Unit 4 Text: Urinalysis PDF

220 Part Two | Urinalysis Introduction hypertension, oliguria, proteinuria, and hematuria. Symptoms usually occur in children and young adults after respiratory Disord...

220 Part Two | Urinalysis Introduction hypertension, oliguria, proteinuria, and hematuria. Symptoms usually occur in children and young adults after respiratory Disorders throughout the body can affect renal function and infections caused by certain strains of group A β-hemolytic strep- produce abnormalities in the urinalysis. Considering that the tococci that contain M protein in the cell wall. During the course major function of the kidneys is filtration of the blood to remove of the infection, these nephrogenic strains of streptococci form waste products, it becomes evident that the kidneys are consis- immune complexes with their corresponding circulating antibod- tently exposed to substances that are potentially damaging. ies and become deposited on the glomerular membranes. The Often renal disease is classified as being glomerular, tubular, accompanying inflammatory reaction affects glomerular function. or interstitial, based on the area of the kidney primarily affected. In most cases, treatment involves successful management In this chapter, we will cover the disorders encountered most of the secondary complications (hypertension and electrolyte commonly in relation to the affected areas of the kidney. Basic imbalance) until the immune complexes have been cleared knowledge of these disorders can be helpful when analyzing the from the blood and the inflammation subsides, resulting in no results of a routine urinalysis. permanent damage to the kidney. Primary urinalysis findings include marked hematuria, Glomerular Disorders proteinuria, and oliguria, accompanied by red blood cell (RBC) casts, dysmorphic RBCs, hyaline and granular casts, and Most glomerular disorders result from immunologic disorders white blood cells (WBCs). As toxicity to the glomerular mem- throughout the body, including the kidney. Immune complexes brane subsides, urinalysis results return to normal, with the formed as a result of immunologic reactions and increased possible exception of microscopic hematuria that lasts until the serum immunoglobulins, such as immunoglobulin A (IgA), cir- membrane damage has been repaired. Blood urea nitrogen culate in the bloodstream and are deposited on the glomerular (BUN) may be elevated during the acute stages, but, like the membranes. Then components of the immune system, includ- urinalysis, returns to normal. Demonstration of positive anti– ing complement, neutrophils, lymphocytes, monocytes, and cy- group A streptococcal enzyme tests (antistreptolysin O [ASO] tokines, are attracted to the deposit area, producing changes and antideoxyribonuclease-B antibody [anti-DNase B]) pro- and damage to the membranes. Depending on the immune sys- vides evidence that the disease is of streptococcal origin. tem mediators involved, damage may consist of cellular infil- Since the development of rapid anti–group A streptococcal tration or proliferation, resulting in thickening of the glomerular enzyme tests that can be performed in a physician’s office, ur- basement membrane, as well as complement-mediated damage gent care facility, or emergency department, the incidence of to the capillaries and basement membrane. acute poststreptococcal glomerulonephritis has declined. Nonimmunologic causes of glomerular damage include the following: Technical Tip 8-1. RBC casts are a hallmark character- Exposure to chemicals and toxins that also affect the istic of acute glomerulonephritis. tubules Disruption of the electrical membrane charges as occurs in nephrotic syndrome (NS) Rapidly Progressive (Crescentic) Glomerulonephritis Deposition of amyloid material from systemic disorders A more serious form of acute glomerular disease is called rapidly that may involve chronic inflammation and acute-phase progressive (or crescentic) glomerulonephritis (RPGN) and reactants has a much poorer prognosis, often terminating in renal failure. Thickening of the basement membrane associated with Symptoms are initiated by deposition of immune complexes in diabetic nephropathy the glomerulus, often as a complication of another form of glomerulonephritis or a disorder of the immune system, such as Glomerulonephritis systemic lupus erythematosus (SLE). Damage by macrophages The term glomerulonephritis refers to a sterile, in- to the capillary walls releases cells and plasma into Bowman flammatory process that affects the glomerulus and space, and the production of crescentic formations containing is associated with the finding of blood, protein, and macrophages, fibroblasts, and polymerized fibrin causes perma- casts in the urine.1 A variety of types of glomeru- nent damage to the capillary tufts. lonephritis exist, and the condition also may progress from one Initial laboratory results are similar to AGN but become form to another (i.e., rapidly progressive glomerular nephritis, more abnormal as the disease progresses, including protein lev- to chronic glomerulonephritis, to nephrotic syndrome and els that are markedly elevated and glomerular filtration rates eventual renal failure). that are very low. Some forms may demonstrate increased fib- rin degradation products, cryoglobulins, and the deposition of Acute Poststreptococcal Glomerulonephritis IgA immune complexes in the glomerulus.2 As its name implies, acute glomerulonephritis (AGN) is a Goodpasture Syndrome disease marked by the sudden onset of symptoms consistent with damage to the glomerular membrane. These may include Morphological changes to the glomeruli resembling those in rap- fever, edema (most noticeably around the eyes), fatigue, nausea, idly progressive glomerular nephritis are seen in conjunction with  Chapter 8 | Renal Disease 221 the autoimmune disorder termed Goodpasture syndrome. A SLE, Sjögren syndrome, secondary syphilis, hepatitis B, gold cytotoxic autoantibody can appear against the glomerular and and mercury treatments, and malignancy. In about 75% of cases, alveolar basement membranes after viral respiratory infections. the etiology is unknown.6 As a rule, the disease progresses Attachment of this autoantibody to the basement membrane, slowly, with possible remission; however, symptoms of nephrotic followed by complement activation, produces the capillary de- syndrome frequently develop.7 There also may be a tendency struction. Referred to as antiglomerular basement membrane toward thrombosis. antibody, the autoantibody can be detected in patient serum. Laboratory findings include microscopic hematuria and Initial pulmonary complaints are hemoptysis and dyspnea, elevated urine protein excretion that may reach concentrations followed by the development of hematuria. Urinalysis results similar to those in nephrotic syndrome. RBC casts are rare, but include proteinuria, hematuria, and the presence of RBC casts. microscopic hematuria is common.6 Demonstration of one of Progression to chronic glomerulonephritis and end-stage renal the secondary disorders through blood tests can aid in the failure is common. diagnosis. Granulomatosis With Polyangiitis Membranoproliferative Glomerulonephritis Granulomatosis with polyangiitis (GPA), formerly called Membranoproliferative glomerulonephritis (MPGN) is Wegener granulomatosis, causes a granuloma-producing in- marked by different alterations in the cellularity of the flammation of the small blood vessels, primarily of the kidney glomerulus and peripheral capillaries. Type 1 displays in- and respiratory system.3 Key to the diagnosis of GPA is the creased cellularity in the subendothelial cells of the mesangium demonstration of antineutrophilic cytoplasmic antibody (interstitial area of Bowman capsule), causing thickening of the (ANCA) in the patient’s serum.3,4 Binding of these autoanti- capillary walls, whereas type 2 (dense deposit disease) displays bodies to the neutrophils located in the vascular walls may ini- extremely dense deposits in the glomerular basement mem- tiate the immune response and the resulting granuloma brane, tubules, and Bowman capsule. MPGN type 3 is charac- formation. Patients usually present first with pulmonary symp- terized by both subepithelial and subendothelial deposits.8 toms and later develop renal involvement, including hema- Many of the patients are children, and the disease has a poor turia, proteinuria, RBC casts, and elevated levels of serum prognosis: type 1 patients progress to nephrotic syndrome, and creatinine and BUN. type 2 patients experience symptoms of chronic glomeru- Testing for ANCA includes incubating the patient’s serum lonephritis. There is a high incidence of recurrent disease after with either ethanol or formalin/formaldehyde-fixed neutrophils renal transplant.8 The laboratory findings vary, but hematuria, and examining the preparation using indirect immunofixation proteinuria, and decreased serum complement levels are usual to detect the serum antibodies attached to the neutrophils. If findings. There appears to be an association with autoimmune the neutrophils are fixed in ethanol, the antibodies form a disorders, infections, and malignancies.9 perinuclear pattern called p-ANCA. When the neutrophils are Chronic Glomerulonephritis fixed with formalin/formaldehyde, the pattern is granular throughout the cytoplasm and is referred to as c-ANCA.5 Depending on the amount and duration of the damage to the glomerulus in the glomerular disorders discussed Henoch-Schönlein Purpura previously, progression to chronic glomerulonephritis (CGN) and end-stage renal disease (ESRD) may occur. Henoch-Schönlein purpura disease occurs primarily in chil- Gradually worsening symptoms include fatigue, anemia, hyper- dren after upper respiratory infections. As its name implies, tension, edema, and oliguria. initial symptoms include the appearance of raised, red patches Examination of the urine reveals hematuria, proteinuria, on the skin. Respiratory and gastrointestinal symptoms, in- glucosuria as a result of tubular dysfunction, and many vari- cluding blood in the sputum and stools, may be present. Renal eties of casts, including broad casts. A glomerular filtration rate involvement is the most serious complication of the disorder that is markedly decreased is present in conjunction with in- and may range from mild to heavy proteinuria and hematuria creased BUN and creatinine levels and electrolyte imbalance. with RBC casts. Complete recovery with normal renal function is seen in more than 50% of patients. In other patients, pro- gression to a more serious form of glomerulonephritis and Technical Tip 8-2. The presence of broad casts renal failure may occur. Urinalysis and renal function assess- is often seen in chronic glomerulonephritis that ment should be used to monitor patients after recovery from progresses to ESRD. the original symptoms. Membranous Glomerulonephritis Immunoglobulin A Nephropathy The predominant characteristic of membranous glomeru- lonephritis (MGN) is a pronounced thickening of the glomeru- Also known as Berger disease, IgA nephropathy, in which im- lar basement membrane resulting from the deposition of mune complexes containing IgA are deposited on the glomerular immunoglobulin G immune complexes. Disorders associated membrane, is the most common cause of glomerulonephritis. with membranous glomerulonephritis development include Patients have increased serum levels of IgA, which may be a 222 Part Two | Urinalysis result of a mucosal infection. The disorder is seen most fre- results for BUN and creatinine. It is the most common cause of quently in children and young adults. nephrotic syndrome in children (85% to 95%) but only 10% to Patients usually present with an episode of macroscopic 15% of cases of nephrotic syndrome in adults.11 Although hematuria after an infection or strenuous exercise. Recovery the etiology is unknown at this time, allergic reactions, recent from the macroscopic hematuria is spontaneous; however, immunization, and possession of the human leukocyte antigen- asymptomatic microhematuria and elevated serum levels of IgA B12 (HLA-B12) antigen have been associated with this disease. remain.10 Except for periodic episodes of macroscopic hema- Therefore, it is postulated that MCD is a disorder of T cells, turia, a patient with the disorder may remain essentially which release a cytokine that injures the glomerular epithelial asymptomatic for 20 years or more; however, there is a gradual foot processes.11 The disorder responds well to corticosteroids, progression to chronic glomerulonephritis and ESRD. and the prognosis is generally good, with frequent complete remissions.12 Nephrotic Syndrome Focal Segmental Glomerulosclerosis Nephrotic syndrome is marked by massive protein- uria (greater than 3.5 g/day), low levels of serum In contrast to the disorders discussed previously, focal segmen- albumin, high levels of serum lipids, and pronounced tal glomerulosclerosis (FSGS) affects only certain numbers edema.1 Acute onset of the disorder can occur in in- and areas of glomeruli and the others remain normal. FSGS is stances of circulatory disruption, producing systemic shock that one of the most common causes of primary glomerular disease decreases the pressure and flow of blood to the kidney. Progres- in adults. It can occur as a primary (idiopathic) glomerular dis- sion to nephrotic syndrome also may occur as a complication ease or secondary to another disease or drug. Often FSGS is of the forms of glomerulonephritis discussed previously. seen in association with abuse of heroin and analgesics and with Increased permeability of the glomerular membrane is the HIV and hepatitis viruses.13 Symptoms may be similar to attributed to damage to the shield of negativity and the nephrotic syndrome and MCD due to damaged podocytes. podocytes that produces a barrier that is less tightly connected. Immune deposits, primarily immunoglobulin M and C3, are a Such damage facilitates the passage of high-molecular-weight frequent finding and can be seen in undamaged glomeruli. proteins and lipids and negatively charged albumin into the Moderate to heavy proteinuria and microscopic hematuria are urine. Albumin is the primary protein depleted from the circu- the most consistent findings from urinalysis.13 lation. The ensuing hypoalbuminemia appears to stimulate in- Laboratory testing and clinical information for the creased lipid production by the liver. The lower oncotic pressure glomerular disorders are summarized in Tables 8-1 and 8-2. in the capillaries resulting from the depletion of plasma albumin increases fluid loss into the interstitial spaces, which, accompa- Tubular Disorders nied by sodium retention, produces the edema. Depletion of immunoglobulins and coagulation factors places patients at an Disorders affecting the renal tubules include those in which increased risk of infection and coagulation disorders. Both tubular function is disrupted as a result of actual damage to tubular and glomerular damage occurs, and nephrotic syndrome the tubules, as well as those in which a metabolic or hereditary may progress to chronic renal failure. disorder affects the intricate functions of the tubules. Urinalysis observations include marked proteinuria; urinary fat droplets (lipiduria); oval fat bodies; renal tubular epithelial Acute Tubular Necrosis (RTE) cells; epithelial, fatty, and waxy casts; and microscopic The primary disorder associated with damage to the hematuria. Absorption of the lipid-containing proteins by the renal tubules is acute tubular necrosis (ATN). RTE cells followed by cellular sloughing produces the charac- Damage to the RTE cells may be produced by de- teristic oval fat bodies seen in the sediment examination. creased blood flow that causes a lack of oxygen pres- entation to the tubules (ischemia) or the presence of toxic substances in the urinary filtrate. Technical Tip 8-3. As discussed in Chapter 7, using Disorders causing ischemic ATN include shock, trauma polarized light microscopy will result in the appear- (such as crushing injuries), and surgical procedures. “Shock” ance of the characteristic Maltese cross formation is a general term indicating a severe condition that decreases in the oval fat bodies and fatty casts containing the flow of blood throughout the body. Examples of conditions cholesterol. that may cause shock are cardiac failures, sepsis involving tox- igenic bacteria, anaphylaxis, massive hemorrhage, and contact with high-voltage electricity. Minimal Change Disease Exposure to a variety of nephrotoxic agents can damage As the name implies, minimal change disease (MCD) (also and affect the function of the RTE cells. Substances include known as lipid nephrosis or nil disease) produces little cellular aminoglycoside antibiotics, the antifungal agent amphotericin change in the glomerulus, except for some damage to the B, cyclosporine, radiographic dye, organic solvents such as eth- podocytes and the shield of negativity, allowing for increased ylene glycol, heavy metals, and toxic mushrooms. As discussed protein filtration. Patients are usually children who present in Chapter 6, filtration of large amounts of hemoglobin and with edema, heavy proteinuria, transient hematuria, and normal myoglobin is also nephrotoxic.  Chapter 8 | Renal Disease 223 Table 8–1 Laboratory Testing in Glomerular Disorders Disorder Primary Urinalysis Result Other Significant Tests Acute glomerulonephritis (AGN) Macroscopic hematuria Anti–group A streptococcal enzyme tests Proteinuria RBC casts Granular casts Rapidly progressive Macroscopic hematuria BUN glomerulonephritis (RPGN) Proteinuria Creatinine RBC casts eGFR Goodpasture syndrome Macroscopic hematuria Antiglomerular basement membrane antibody Proteinuria RBC casts Granulomatosis with Macroscopic hematuria Antineutrophilic peripheral or cytoplasmic antibody polyangiitis (GPA) Proteinuria RBC casts Henoch-Schönlein purpura Macroscopic hematuria Stool occult blood Proteinuria RBC casts Membranous Microscopic hematuria Antinuclear antibody glomerulonephritis (MGN) Proteinuria Hepatitis B surface antigen Fluorescent treponemal antibody-absorption test (FTA-ABS) Membranoproliferative Hematuria Serum complement levels glomerulonephritis (MPGN) Proteinuria Chronic Hematuria BUN glomerulonephritis (CGN) Proteinuria Serum creatinine Glucosuria eGFR Cellular and granular casts Electrolytes Waxy and broad casts IgA nephropathy (early stages) Macroscopic or microscopic Serum IgA hematuria IgA nephropathy (late stages) See Chronic glomeru- lonephritis (CGN) Nephrotic syndrome (NS) Heavy proteinuria Serum albumin Microscopic hematuria Cholesterol Renal tubular cells Triglycerides Oval fat bodies Fat droplets Fatty and waxy casts Minimal change disease (MCD) Heavy proteinuria Serum albumin Transient hematuria Cholesterol Continued 224 Part Two | Urinalysis Table 8–1 Laboratory Testing in Glomerular Disorders—cont’d Disorder Primary Urinalysis Result Other Significant Tests Fat droplets Triglycerides Focal segmental Proteinuria Drugs of abuse glomerulosclerosis (FSGS) Microscopic hematuria HIV tests Macroscopic or microscopic hematuria Alport syndrome See Nephrotic Genetic testing syndrome (NS) Microalbuminuria Diabetic nephropathy (late stages) See Chronic glomeru- Blood glucose lonephritis (CGN) Table 8–2 Clinical Information Associated With Glomerular Disorders Disorder Etiology Clinical Course Acute glomerulonephritis (AGN) Deposition of immune complexes, Rapid onset of hematuria and edema; formed in conjunction with beta- permanent renal damage seldom hemolytic group A Streptococcus infec- occurs tion, on the glomerular membranes Rapidly progressive Deposition of immune complexes from Rapid onset with glomerular damage glomerulonephritis (RPGN) systemic immune disorders on the and possible progression to end-stage glomerular membrane renal failure Goodpasture syndrome Attachment of a cytotoxic antibody Hemoptysis and dyspnea followed by formed during viral respiratory infec- hematuria tions to glomerular and alveolar base- ment membranes Possible progression to end-stage renal failure Granulomatosis with Antineutrophilic cytoplasmic autoanti- Pulmonary symptoms, including he- polyangiitis (GPA) body (ANCA) binds to neutrophils moptysis, develop first, followed by in vascular walls, producing damage renal involvement and possible pro- to small vessels in the lungs and gression to end-stage renal failure glomerulus Henoch-Schönlein purpura Occurs primarily in children after viral Initial appearance of purpura followed respiratory infections; a decrease in by blood in sputum and stools and platelets disrupts vascular integrity eventual renal involvement Complete recovery is common, but may progress to renal failure Membranous Thickening of the glomerular membrane Slow progression to nephrotic syndrome glomerulonephritis (MGN) after IgG immune complex deposition or possible remission associated with systemic disorders Membranoproliferative Cellular proliferation affecting the capil- Slow progression to chronic glomeru- glomerulonephritis (MPGN) lary walls or the glomerular basement lonephritis (CGN) or nephrotic syn- membrane, possibly immune mediated drome (NS) Chronic Marked decrease in renal function result- Noticeable decrease in renal function glomerulonephritis (CGN) ing from glomerular damage precipi- progressing to renal failure tated by other renal disorders  Chapter 8 | Renal Disease 225 Table 8–2 Clinical Information Associated With Glomerular Disorders—cont’d Disorder Etiology Clinical Course IgA nephropathy Deposition of IgA on the glomerular Recurrent macroscopic hematuria after membrane resulting from increased exercise with slow progression to levels of serum IgA chronic glomerulonephritis (CGN) Nephrotic syndrome (NS) Disruption of the shield of negativity and Acute onset after systemic shock damage to the tightly fitting podocyte Gradual progression from other barrier, resulting in massive loss of glomerular disorders and then to renal protein and lipids failure Minimal change disease (MCD) Disruption of the podocytes occurring Frequent complete remission after corti- primarily in children after allergic reac- costeroid treatment tions and immunizations; dysfunction of T-cell immunity Focal segmental Disruption of podocytes in certain areas May resemble nephrotic syndrome (NS) glomerulosclerosis (FSGS) of glomeruli associated with heroin or minimal change disease (MCD) and analgesic abuse and with HIV and hepatitis viruses Alport syndrome Genetic disorder showing lamellated Slow progression to nephrotic syndrome and thinning glomerular basement (NS) and end-stage renal disease membrane The disease course of ATN varies. It may present as an convoluted tubule. Therefore, substances affected most no- acute complication of an ischemic event or more gradually dur- ticeably include glucose, amino acids, phosphorous, sodium, ing exposure to toxic agents. Correcting the ischemia, removing potassium, bicarbonate, and water. Tubular reabsorption may the toxic substances, and effectively managing the accompany- be affected by dysfunction of the transport of filtered sub- ing symptoms of acute renal failure (ARF) frequently result in stances across the tubular membranes, disruption of cellular a complete recovery. energy needed for transport, or changes in the tubular Urinalysis findings include mild proteinuria, microscopic membrane permeability. hematuria, and, most noticeably, the presence of RTE cells and Fanconi syndrome may be inherited in association with RTE cell casts containing tubular fragments consisting of three cystinosis and Hartnup disease (see Chapter 9), acquired or more cells. As a result of the tubular damage, a variety of through exposure to toxic agents, including heavy metals and other casts may be present, including hyaline, granular, waxy, outdated tetracycline, or seen as a complication of multiple and broad. myeloma or renal transplant. Urinalysis findings include glycosuria with a normal blood Technical Tip 8-4. RTE cell casts and the presence glucose and possible mild proteinuria. Urinary pH can be very of RTE cells in the urine sediment are characteristic low due to the failure to reabsorb bicarbonate. for ATN. Alport Syndrome Alport syndrome is an inherited disorder of collagen produc- Hereditary and Metabolic Tubular tion affecting the glomerular basement membrane. The syn- Disorders drome can be inherited as a sex-linked or autosomal genetic disorder. Males inheriting the X-linked gene are affected more Disorders affecting tubular function may be caused by systemic severely than females inheriting the autosomal gene. During conditions that affect or override the tubular reabsorptive max- respiratory infections, males younger than 6 years of age may imum (Tm) for particular substances normally reabsorbed by exhibit macroscopic hematuria and continue to exhibit mi- the tubules or by failure to inherit a gene or genes required for croscopic hematuria. Abnormalities in hearing and vision tubular reabsorption. may also develop. The glomerular basement membrane has a lamellated ap- Fanconi Syndrome pearance with areas of thinning. No evidence of glomerular an- The disorder associated with tubular dysfunction most fre- tibodies is present. The prognosis ranges from mild symptoms quently is Fanconi syndrome. The syndrome consists of a to persistent hematuria, proteinuria, and renal insufficiency in generalized failure of tubular reabsorption in the proximal later life to nephrotic syndrome and ESRD. 226 Part Two | Urinalysis Uromodulin-Associated Kidney Disease Urinalysis findings associated with DI are low specific gravity, pale yellow color, and possible false-negative results Uromodulin is a glycoprotein and is the only protein produced for chemical tests. by the kidney—in the proximal and distal convoluted tubules. Although it is not measured by routine laboratory methods, Renal Glycosuria research has shown that it is the primary protein found in In contrast to Fanconi syndrome, which exhibits a generalized normal urine. failure to reabsorb substances from the glomerular filtrate, renal Uromodulin-associated kidney disease is primarily an glucosuria affects only the reabsorption of glucose. The disor- inherited disorder caused by an autosomal mutation in the der is inherited as an autosomal recessive trait. gene that produces uromodulin. The mutation causes a de- In inherited renal glucosuria, either the number of glucose crease in the production of normal uromodulin that is replaced transporters in the tubules is decreased or the affinity of the by the abnormal form. The abnormal uromodulin is still pro- transporters for glucose is decreased. Under normal conditions, duced by the tubular cells and accumulates in them, resulting glucose is not present in the urine unless the blood glucose in their destruction, which leads to the need for renal moni- level reaches the maximal tubular reabsorption capacity for toring and eventual renal transplantation.14 glucose (TMG), which is 160 to 180 mg/dL. Patients with renal The mutation also causes an increase in serum uric acid, glycosuria have increased urine glucose concentrations with resulting in people developing gout as early as the teenage normal blood glucose concentrations. years before the onset of detectable renal disease.14 Laboratory testing and clinical information for the hered- itary and metabolic disorders are summarized in Tables 8-3 and 8-4. Technical Tip 8-5. As discussed in Chapter 7, uro- modulin forms the matrix of urinary casts seen in many renal disorders. The defective gene is not Interstitial Disorders associated with other renal disorders. Considering the close proximity between the renal tubules and the renal interstitium, disorders affecting the interstitium also affect the tubules, resulting in Diabetic Nephropathy the condition commonly called tubulointerstitial Diabetic nephropathy is currently the most common cause of disease. Most of these disorders involve infections and inflam- ESRD. Damage to the glomerular membrane occurs not only as matory conditions. a result of glomerular membrane thickening but also because of the increased proliferation of mesangial cells and increased Urinary Tract Infection deposition of cellular and noncellular material within the The most common renal disease is a urinary tract infection glomerular matrix, resulting in accumulation of solid substances (UTI). Infection may involve the lower urinary tract (urethra around the capillary tufts. This glomerular damage is believed and bladder) or the upper urinary tract (renal pelvis, tubules, to be associated with deposition of glycosylated proteins result- and interstitium). Most frequently encountered is infection of ing from poorly controlled levels of blood glucose. The vascular the bladder (cystitis), which can progress to a more serious structure of the glomerulus also develops sclerosis. upper UTI if left untreated. Cystitis is seen more often in women As discussed in Chapter 6, early monitoring of people and children, who present with symptoms of urinary frequency diagnosed with diabetes mellitus for the presence of microalbu- and burning. Urinalysis reveals the presence of numerous minuria is important to detect the onset of diabetic nephropathy. WBCs and bacteria, often accompanied by mild proteinuria and Modification of diet and strict control of hypertension can hematuria and an increased pH. The absence of pathological decrease the progression of the renal disease. casts differentiates cystitis from pyelonephritis. Nephrogenic Diabetes Insipidus Acute Pyelonephritis As discussed in Chapter 4, urine concentration is regulated Infection of the upper urinary tract, including both the tubules in the distal convoluted tubules and the collecting ducts in and interstitium, is termed pyelonephritis and can occur in response to antidiuretic hormone (ADH) produced by the both acute and chronic forms. Acute pyelonephritis occurs hypothalamus. When the action of ADH is disrupted either most frequently as a result of ascending movement of bacteria by the inability of the renal tubules to respond to ADH from a lower UTI into the renal tubules and interstitium. Pa- (nephrogenic diabetes insipidus [DI]) or failure of the hypo- tients present with rapid onset of symptoms, including urinary thalamus to produce ADH (neurogenic DI), excessive amounts frequency, burning on urination, and lower back pain. of urine are excreted. Differentiation between the two types The ascending movement of bacteria from the bladder is of DI is covered in Chapter 4. enhanced with conditions that interfere with the downward flow Nephrogenic DI can be inherited as a sex-linked recessive of urine from the ureters to the bladder or the incomplete emp- gene or acquired from medications, including lithium and am- tying of the bladder during urination. These include obstruc- photericin B. It also may be seen as a complication of polycystic tions, such as renal calculi, pregnancy, and reflux of urine from kidney disease and sickle cell anemia. the bladder back into the ureters (vesicoureteral reflux [VUR]).  Chapter 8 | Renal Disease 227 Table 8–3 Laboratory Testing in Metabolic and Hereditary Tubular Disorders Disorder Primary Urinalysis Results Other Significant Tests Acute tubular necrosis (ATN) Microscopic hematuria Hemoglobin Proteinuria Hematocrit Renal tubular epithelial (RTE) cells RTE cell casts Cardiac enzymes Hyaline, granular, waxy, broad casts Fanconi syndrome Glucosuria Serum and urine electrolytes Possible cystine crystals Amino acid chromatography Uromodulin-associated kidney RTE cells Serum uric acid disease (early stages) Uromodulin-associated kidney See chronic glomerulonephritis (CGN) disease (late stages) Nephrogenic diabetes insipidus (DI) Low specific gravity, polyuria ADH testing Renal glucosuria Glucosuria Blood glucose Table 8–4 Clinical Information Associated With Metabolic and Tubular Disorders Disorder Etiology Clinical Course Acute tubular necrosis (ATN) Damage to renal tubular cells caused by is- Acute onset of renal dysfunction usu- chemia or toxic agents ally resolved when underlying cause is corrected Fanconi syndrome Inherited in association with cystinosis and Generalized defect in renal tubular Hartnup disease or acquired through reabsorption requiring supportive exposure to toxic agents therapy Uromodulin-associated Inherited defect in the production of normal Continual monitoring of renal function kidney disease uromodulin by the renal tubules and for progression to renal failure and increased uric acid causing gout possible kidney transplantation Nephrogenic diabetes Inherited defect of tubular response to ADH or Requires supportive therapy to prevent insipidus (DI) acquired from medications dehydration Renal glucosuria Inherited autosomal recessive trait Benign disorder With appropriate antibiotic therapy and removal of any under- structural abnormalities may cause reflux between the bladder lying conditions, acute pyelonephritis can be resolved without and ureters or within the renal pelvis, affecting emptying of permanent damage to the tubules. the collecting ducts. Due to its congenital origin, chronic Urinalysis results are similar to those seen in cystitis, includ- pyelonephritis often is diagnosed in children and may not be ing numerous leukocytes and bacteria with mild proteinuria and suspected until tubular damage has become advanced. hematuria. The additional finding of WBC casts, signifying in- Urinalysis results are similar to those seen in acute fection within the tubules, is of primary diagnostic value for both pyelonephritis, particularly in the early stages. As the disease acute and chronic pyelonephritis. Sediments also should be progresses, a variety of granular, waxy, and broad casts are pres- observed carefully for the presence of bacterial casts. ent, accompanied by increased proteinuria and hematuria, and renal concentration is decreased. Chronic Pyelonephritis As its name implies, chronic pyelonephritis is a serious disor- der that can result in permanent damage to the renal tubules Technical Tip 8-6. The presence of WBC casts is and possible progression to chronic renal failure. Congenital significant for differentiating between cystitis and urinary structural defects producing reflux nephropathy pyelonephritis. are the most frequent cause of chronic pyelonephritis. The 228 Part Two | Urinalysis Acute Interstitial Nephritis Table 8–5 Laboratory Results in Interstitial Acute interstitial nephritis (AIN) is marked by Disorders inflammation of the renal interstitium followed by in- Primary Other flammation of the renal tubules. Patients present with Urinalysis Significant a rapid onset of symptoms relating to renal dys- Disorder Results Tests function, including oliguria, edema, decreased renal concen- trating ability, and a possible decrease in the glomerular Cystitis Leukocyturia Urine culture filtration rate. Fever and the presence of a skin rash are fre- Bacteriuria quent initial symptoms. Microscopic AIN is associated primarily with an allergic reaction to hematuria medications that occurs within the renal interstitium, possibly Mild proteinuria caused by the medication binding to the interstitial protein. Symptoms tend to develop approximately 2 weeks after admin- Increased pH istration of medication. Medications commonly associated with Acute Leukocyturia Urine culture AIN include penicillin, methicillin, ampicillin, cephalosporins, pyelonephritis rifampin, sulfonamides, NSAIDs, and thiazide diuretics. Other Bacteriuria drugs that are implicated commonly include indinavir, proton WBC casts pump inhibitors, allopurinol, 5-aminosalicylates, diuretics, and cimetidine.15 Discontinuing the offending medication and Bacterial casts administering steroids to control the inflammation frequently Microscopic result in a return to normal renal function. However, support- hematuria ive renal dialysis may be required to maintain patients until Proteinuria the inflammation subsides. Chronic Leukocyturia Urine culture Urinalysis results include hematuria, possibly macro- pyelonephritis scopic; mild to moderate proteinuria; numerous WBCs; and WBC casts without bacteria. Differential leukocyte staining for Bacteriuria BUN the presence of increased eosinophils may be useful to confirm WBC casts the diagnosis.16 Bacterial casts Laboratory testing and clinical information for the inter- Granular, waxy, Creatinine stitial disorders are summarized in Tables 8-5 and 8-6. broad casts Hematuria Technical Tip 8-7. The presence of eosinophil Proteinuria eGFR casts and eosinophils in the urine sediment are Acute interstitial Hematuria Urine characteristic for AIN. nephritis (AIN) eosinophils Proteinuria BUN Leukocyturia Creatinine Renal Failure WBC casts eGFR Renal failure exists in both acute and chronic forms. As discussed previously in conjunction with many of the disorders, this may be a gradual progression ARF, in contrast to chronic renal failure, exhibits a sudden from the original disorder to chronic renal failure or loss of renal function and frequently is reversible. Primary ESRD. The progression to ESRD is characterized as follows: causes of ARF include a sudden decrease in blood flow to the Marked decrease in the glomerular filtration rate (less kidney (prerenal), acute glomerular and tubular disease (renal), than 25 mL/min) and renal calculi or tumor obstructions (postrenal). As seen Steadily rising serum BUN and creatinine values from the variety of causes (Box 8-1), patients may present with (azotemia) many different symptoms relating to the particular disorder in- Electrolyte imbalance volved; however, general characteristics include a decreased Lack of renal concentrating ability, producing an glomerular filtration rate, oliguria, edema, and azotemia. isosthenuric urine Similar to clinical symptoms, urinalysis findings are varied, but because they relate to the primary cause of the ARF, they Proteinuria can be diagnostically valuable. For example, the presence of Renal glycosuria RTE cells and casts suggests ATN of prerenal origin; RBCs indi- Abundance of granular, waxy, and broad casts, often cate glomerular injury; WBC casts, with or without bacteria, in- referred to as a telescoped urine sediment dicate interstitial infection or inflammation of renal origin; and  Chapter 8 | Renal Disease 229 Table 8–6 Clinical Information Associated With Interstitial Disorders Disorder Etiology Clinical Course Cystitis Ascending bacterial infection of the bladder Acute onset of urinary frequency and burning; resolved with antibiotics Acute pyelonephritis Infection of the renal tubules and intersti- Acute onset of urinary frequency, burning, and tium related to interference of urine flow lower back pain; resolved with antibiotics to the bladder, reflux of urine from the bladder, and untreated cystitis Chronic pyelonephritis Recurrent infection of the renal tubules and Frequently diagnosed in children; requires interstitium caused by structural abnor- correction of the underlying structural malities affecting the flow of urine defect Possible progression to renal failure Acute interstitial Allergic inflammation of the renal intersti- Acute onset of renal dysfunction often nephritis (AIN) tium in response to certain medications accompanied by a skin rash Resolves after discontinuation of medication and treatment with corticosteroids postrenal obstruction may show normal- and abnormal-appearing calculi resembling the shape of the renal pelvis and smooth, urothelial cells possibly associated with malignancy. round bladder stones with diameters of 2 or more inches. Small calculi may be passed in the urine, subjecting the patient to severe pain radiating from the lower back to the legs. Larger stones can- Technical Tip 8-8. Broad casts are often referred to as not be passed and may not be detected until patients develop renal failure casts. symptoms of urinary obstruction. Lithotripsy, a procedure using high-energy shock waves, can be used to break stones located in the upper urinary tract into pieces that then can be passed in the Renal Lithiasis urine. Also, stones can be removed surgically. Conditions favoring the formation of renal calculi are sim- Renal calculi (kidney stones) may form in the calyces and ilar to those favoring formation of urinary crystals, including pelvis of the kidney, ureters, and bladder. In renal lithiasis, pH, chemical concentration, and urinary stasis. Numerous cor- the calculi vary in size from barely visible to large, staghorn relation studies between the presence of crystalluria and renal calculi formation have been conducted with varying results. The finding of clumps of crystals in freshly voided urine sug- gests that conditions may be right for calculus formation. How- Box 8–1 Causes of Acute Renal Failure ever, due to the difference in conditions that affect the urine within the body and in a specimen container, little importance Prerenal can be placed on the role of crystals in predicting calculi for- Decreased blood pressure/cardiac output mation. Increased crystalluria has been noted during the sum- Hemorrhage mer months in people known to form renal calculi.17 Burns Analysis of the chemical composition of renal calculi plays an important role in patient management. Analysis can Surgery be performed chemically, but examination using x-ray crys- Septicemia tallography provides a more comprehensive analysis. Approx- Renal imately 75% of the renal calculi are composed of calcium oxalate or calcium phosphate. Magnesium ammonium phos- Acute glomerulonephritis (AGN) phate (struvite), uric acid, and cystine are the other primary Acute tubular necrosis (ATN) calculi constituents. Frequently calcium calculi are associated Acute pyelonephritis with metabolic calcium and phosphate disorders and, occa- Acute interstitial nephritis (AIN) sionally, diet. Magnesium ammonium phosphate calculi often are accompanied by urinary infections involving urea-splitting Postrenal bacteria. The urine pH is often higher than 7.0. Uric acid cal- Renal calculi culi may be associated with increased intake of foods with Tumors high purine content and with uromodulin-associated kidney disease. The urine pH is acidic. Most cystine calculi are seen 230 Part Two | Urinalysis in conjunction with hereditary disorders of cystine metabo- StatPerarls (Internet). Web site: https://www.ncbi.nlm.nih.gov/ lism (see Chapter 9). Patient management techniques include books/NBK499865/. Published February 15, 2019. Accessed May 19, 2019. maintaining the urine at a pH incompatible with crystalliza- 7. Wasserstein, AG: Membranous glomerulonephritis. In tion of the particular chemicals, maintaining adequate hydra- Jacobson, HR, et al: Principles and Practice of Nephrology. tion to lower chemical concentration, and suggesting possible BC Decker, Philadelphia, 1991. dietary restrictions. 8. Kathuria, P: Membranoproliferative Glomerulonephritis. Urine specimens from patients suspected of passing or Medscape. Web site: https://emedicine.medscape.com/ article/240056-overview. Published June 23, 2016. Accessed being in the process of passing renal calculi are received in the May 19, 2019. laboratory frequently. The presence of microscopic hematuria 9. Donadio, JV: Membranoproliferative glomerulonephritis. In resulting from irritation to the tissues by the moving calculus Jacobson, HR, et al: Principles and Practice of Nephrology. is the primary urinalysis finding. BC Decker, Philadelphia, 1991. 10. Bricker, NS, and Kirschenbaum, MA: The Kidney: Diagnosis and Management. John Wiley, New York, 1984 11. Mansur, A: Minimal-Change Disease. Medscape. Web site: For additional resources please visit https://emedicine.medscape.com/article/243348-overview#a6. www.fadavis.com Published December 24, 2018. Accessed May 19, 2019. 12. Sherbotle, JR, and Hayes, JR: Idiopathic nephrotic syndrome: Minimal change disease and focal segmental glomerulosclerosis. In Jacobson, HR, et al: Principles and Practice of Nephrology. References BC Decker, Philadelphia, 1991. 1. Forland, M (ed): Nephrology. Medical Examination Publishing, 13. Rao, STK: Focal Segmental Glomerulosclerosis. Medscape. New York, 1983. Web site: https://emedicine.medscape.com/article/245915- 2. Couser, WG: Rapidly progressive glomerulonephritis. In overview#a5. Published October 2, 2018. Accessed May 19, Jacobson, HR, et al: Principles and Practice of Nephrology. 2019. BC Decker, Philadelphia, 1991. 14. Bleyer, AJ, Zivna, M, and Kmoch, S: Uromodulin-associated 3. Tracy, CL: Granulomatosis with Polyangiitis (Wegener Granulo- kidney disease. Nephron Clin Prac 118(1):c31–c36, 2011. matosis). Medscape. Web site: https://emedicine.medscape.com/ 15. Finnigan, NA, Bashir, K: Allergic Interstitial Nephritis (AIN). article/332622-overview. Published January 4, 2019. Accessed National Center for Biotechnology Information (NCBI). Stat- May 19, 2019. Pearls [Internet]. Bookshelf ID: 4882323 PMID: 29493948. 4. Kallenberg, CG, Mulder, AH, and Tervaert, JW: Antineutrophil Web site: https://ncbi.nlm.nih.gov/books/NBK482323/. cytoplasmic autoantibodies: A still-growing class of autoantibod- Accessed May 20, 2019. ies in inflammatory disorders. Am J Med 93(6):675–682, 1992. 16. Bennett, WM, Elzinga, LW, and Porter, GA: Tubulointerstitial 5. Frasier, LL, and Hoag, KA: Differential diagnosis of Wegener’s disease and toxic nephropathy. In Brenner, BM, and Rector, FC: granulomatosis from other small vessel vasculitides. LabMed The Kidney: Physiology and Pathophysiology. WB Saunders, 38(7):437–439, 2007. Philadelphia, 1991. 6. Raza, A, and Aggarwal, S: Membranous Glomerulonephritis. 17. Hallson, PC, and Rose, GA: Seasonal variations in urinary National Center for Biotechnology Information. NCBI Resources. crystals. Br J Urol 49(4):277–284, 1977. Study Questions 1. Most glomerular disorders are caused by: 3. Occasional episodes of macroscopic hematuria over peri- A. Sudden drops in blood pressure ods of 20 or more years are seen in patients with: B. Immunologic disorders A. Crescentic glomerulonephritis C. Exposure to toxic substances B. IgA nephropathy D. Bacterial infections C. Nephrotic syndrome D. GPA 2. Dysmorphic RBC casts would be a significant finding with all of the following except: 4. Antiglomerular basement membrane antibody is seen A. Goodpasture syndrome with: B. AGN A. GPA C. Chronic pyelonephritis B. IgA nephropathy D. Henoch-Schönlein purpura C. Goodpasture syndrome D. Diabetic nephropathy 236 Part Two | Urinalysis Introduction renal type. Overflow disorders result from disruption of a nor- mal metabolic pathway that causes increased plasma concen- As discussed in previous chapters, many of the abnormal results trations of the nonmetabolized substances. These chemicals obtained in the routine urinalysis are related to metabolic rather either override the reabsorption ability of the renal tubules or than renal disease. Urine as an end product of body metabolism are not normally reabsorbed from the filtrate because they are may contain additional abnormal substances not tested for by present in only minute amounts. Abnormal accumulations of routine urinalysis. Often these substances can be detected or the renal type are caused by malfunctions in the tubular reab- monitored by additional screening tests that also can be per- sorption mechanism, as discussed in Chapter 8. formed in the urinalysis laboratory. Then positive screening tests The abnormalities encountered most frequently are associ- can be followed up with more sophisticated procedures per- ated with metabolic disturbances that produce urinary overflow formed in other sections of the laboratory (Table 9-1). of substances involved in the metabolism of protein, fat, and car- The need to perform additional tests may be detected by bohydrates. This is understandable when one considers the vast the observations of alert laboratory personnel when performing number of enzymes used in the metabolic pathways of proteins, the routine analysis or from observations of abnormal speci- fats, and carbohydrates and the fact that their function is essen- men color and odor by nursing staff and patients (Table 9-2). tial for complete metabolism. Disruption of enzyme function can In other instances, clinical symptoms and family histories are be caused by failure to inherit the gene to produce a particular the determining factors. enzyme, referred to as an inborn error of metabolism (IEM),1 or by organ malfunction from disease or toxic reactions. The ab- Overflow Versus Renal Disorders normal urinary metabolites that are encountered most frequently are summarized in Table 9-3, and their appearance is classified The appearance of abnormal metabolic substances in the urine according to functional defect. Table 9-3 also includes substances can be caused by a variety of disorders that generally can be and conditions that are covered in this chapter. grouped into two categories, termed the overflow type and the Newborn Screening Tests Table 9–1 Urine Screening Tests for Metabolic Disorders Many of the urine tests discussed in this chapter traditionally were performed primarily to detect and monitor newborns for Test Disorder IEMs. In recent years, the screening of newborns has increased Benedict test Alkaptonuria to include more sensitive detection methods and ever-increasing Ferric chloride test Alkaptonuria levels of state-mandated tests for IEMs. Many states currently require testing for as many as 31 core conditions and 25 second- MSUD ary target conditions.2 Melanuria As discussed later in this chapter, because many of these PKU disorders cause the buildup of unmetabolized toxic food ingre- Hoesch test Porphyria dients, it is important that the defects be detected early in life. Levels of these substances are elevated more rapidly in blood Nitrosonaphthol test Tyrosinuria than in urine. Therefore, blood collected by infant heel puncture Silver nitrate test Alkaptonuria is tested initially. Testing for many substances is now performed Watson-Schwartz test Porphyria using tandem mass spectrophotometry (MS/MS). MS/MS is ca- pable of screening the infant blood specimen for specific sub- stances associated with particular IEMs. Figure 9-1 shows the standard form collected for testing using MS/MS. Methods for Table 9–2 Abnormal Metabolic Constituents or specific gene testing also are being developed rapidly. Conditions Detected in the Routine Urinalysis Color Odor Crystals Amino Acid Disorders Homogentisic Phenylketonuria Cystine The amino acid disorders with urinary screening tests include acid phenylketonuria (PKU), tyrosyluria, melanuria, alkaptonuria, maple syrup urine disease (MSUD), organic acidemias, indi- Melanin Maple syrup urine Leucine canuria, cystinuria, and cystinosis. disease Indican Isovaleric acidemia Tyrosine Phenylalanine-Tyrosine Disorders Porphyrins Cystinuria Lesch-Nyhan Major inherited disorders include PKU, tyrosyluria, and Cystinosis disease alkaptonuria. Metabolic defects cause overproduction of Homocystinuria melanin. The relationship of these varied disorders is illus- trated in Figure 9-2.  Chapter 9 | Urine Screening for Metabolic Disorders 237 Table 9–3 Major Disorders of Protein and Carbohydrate Metabolism Associated With Abnormal Urinary Constituents, Classified by Functional Defect Overflow Inherited Metabolic Renal Phenylketonuria Infantile tyrosinemia Hartnup disease Tyrosinemia Melanuria Cystinuria Alkaptonuria Indicanuria Maple syrup urine disease 5-Hydroxyindoleacetic acid Organic acidemias Porphyria Cystinosis Porphyria Mucopolysaccharidoses Galactosemia Lesch-Nyhan disease screening tests are available for early detection of the abnor- mality, and all states have laws that require the screening of newborns for PKU.2 Once discovered, dietary changes that eliminate phenylalanine, a major constituent of milk, from the infant’s diet can prevent excessive buildup of serum phenylala- nine, thereby avoiding damage to the child’s mental capabilities. Many products that contain large amounts of phenylalanine, such as aspartame (added to medications, diet foods, and diet sodas), now features warning labels for people with PKU. The initial screening for PKU does not come under the auspices of the urinalysis laboratory because increased blood levels of phenylalanine must, of course, occur before urinary excretion of phenylpyruvic acid, which may take 2 to 6 weeks. State laws require that blood be collected between 24 and Figure 9–1 Specimen collection form for MS/MS newborn screen- 48 hours after birth and before the newborn leaves the hospi- ing test. (From Strasinger, SK, and DiLorenzo, MA: The Phlebotomy tal. The increasing tendency to release newborns from the hos- Textbook, 4th ed, FA Davis.) pital as early as 24 hours after birth has caused concern about the ability to detect increased phenylalanine levels at that early Phenylketonuria stage. Studies have shown that in many cases phenylalanine The most well-known of the aminoacidurias, phenylke- can be detected as early as 4 hours after birth, and if the cutoff tonuria (PKU) is estimated to occur in 1 of every 10,000 to level for normal results is lowered from 4 mg/dL to 2 mg/dL, 20,000 births and, if undetected, results in severe intellectual then the presence of PKU should be detected. Tests may need disability. It was first identified in Norway by Ivan Følling in to be repeated during an early visit to the pediatrician. More 1934, when a mother with other children who were intellectually girls than boys escape detection of PKU during early tests be- delayed reported a peculiar mousy odor to her child’s urine and cause of slower rises in levels of blood phenylalanine.1 sweat. Analysis of the urine showed increased amounts of the Urine testing using ferric chloride may be used as a follow- keto acids, including phenylpyruvate. As shown in Figure 9-2, up test to ensure proper dietary control in cases diagnosed pre- this occurs when the normal conversion of phenylalanine to viously and as a means of monitoring the dietary intake of tyrosine is disrupted. Interruption of the pathway also produces pregnant women known to lack phenylalanine hydroxylase. children with fair complexions and lighter hair and eyes—even Urine tests to screen for phenylpyruvic acid are based on in dark-skinned families—due to the decreased production of the ferric chloride reaction performed by tube test. The addi- tyrosine and its pigmentation metabolite melanin. Seizures, tion of ferric chloride to urine containing phenylpyruvic acid hyperactivity, developmental delay, and psychiatric disturbances produces a permanent blue-green color (see Procedure 9-1). also may be present in some patients. Tyrosyluria PKU is caused by failure to inherit the gene to produce the enzyme phenylalanine hydroxylase. The gene is inherited as Tyrosyluria, the accumulation of excess tyrosine in the plasma an autosomal recessive trait with no noticeable characteristics (tyrosinemia) producing urinary overflow, may be due to several or defects exhibited by heterozygous carriers. Fortunately, causes and is not well categorized. As seen in Table 9-2, disorders 238 Part Two | Urinalysis Normal metabolism Metabolic disorders Phenylalanine Enzymes Phenylketonuria Phenylalanine hydroxylase Tyrosine Phenylpyruvic acid Tyrosine Melanin aminotransferase Thyroxine Normal byproducts Tyrosinemia Epinephrine type 2 p-Hydroxyphenylpyruvic acid Tyrosyluria p-hydroxyphenylpyruvic acid p-hydroxyphenylpyruvate p-hydroxyphenyllactic acid oxidase Tyrosinemia Homogentisic acid type 3 Homogentisic acid Alkaptonuria oxidase Maleylacetoacetic acid Homogentisic Maleylacetoacetic acid acid isomerase Tyrosinemia type 1b Fumarylacetoacetic acid Tyrosinemia Fumarylacetoacetic type 1 acid hydrolase Tyrosinemia type 1a Fumaric acid and acetoacetic acid Figure 9–2 Phenylalanine and tyrosine metabolic pathway, including the normal pathway (blue), enzymes (yellow), and disorders caused by failure to inherit particular enzymes (green). and leucine crystals may be observed during microscopic exam- PROCEDURE 9-1 ination of the urine sediment. Ferric Chloride Tube Test Hereditary disorders in which enzymes required in the 1. Place 1 mL of urine in a tube. metabolic pathway are not produced present serious and often fatal conditions that result in both liver and renal tubular dis- 2. Slowly add five drops of 10% ferric chloride. ease, producing a generalized aminoaciduria. Based on the en- 3. Observe color for a permanent blue-green color. zymes affected, the hereditary disorders can be classified into three types, all producing tyrosinemia and tyrosyluria. As shown in Figure 9-2, type 1 is caused by the deficiency of the enzyme fumarylacetoacetate hydrolase (FAH). Type 1 of tyrosine metabolism may result from either inherited or meta- produces a generalized renal tubular disorder and progressive bolic defects. Also, because two reactions are directly involved in liver failure in infants soon after birth. Tyrosemia type 1 is the metabolism of tyrosine, the urine may contain excess tyrosine diagnosed by the detection of tyrosine and succinylacetone in or its degradation products, p-hydroxyphenylpyruvic acid and the urine and blood. Tyrosine and succinylacetone can be p-hydroxyphenyllactic acid. measured on the newborn screening by MS/MS. Molecular Most frequently seen is a transitory tyrosinemia in prema- genetic testing for FAH gene mutations is available to confirm ture infants, which is caused by underdevelopment of the liver the diagnosis.3 function required to produce the enzymes necessary to complete Type 2 tyrosinemia is caused by lack of the enzyme tyro- the tyrosine metabolism. sine aminotransferase. People with type 2 tyrosinemia develop Acquired severe liver disease also produces tyrosyluria re- corneal erosions and lesions on the palms, fingers, and soles sembling that of the transitory newborn variety and, of course, is of the feet, believed to be caused by crystallization of tyrosine a more serious condition. In both instances, rarely seen tyrosine in the cells. Diagnosis of type 2 tyrosinemia is made by testing  Chapter 9 | Urine Screening for Metabolic Disorders 239 for plasma tyrosine and molecular diagnostic tests to determine darkened after becoming alkaline from standing at room tem- genetic markers. Patients also may have elevated 4-hydroxy perature. Therefore, the term “alkali lover,” or alkaptonuria, phenylpyruvic acid in urine. was adopted. This metabolic defect is actually the third major Type 3 tyrosinemia is caused by lack of the enzyme defect in the phenylalanine–tyrosine pathway and occurs from p-hydroxyphenylpyruvic acid dioxygenase. This can result in failure to inherit the gene to produce the enzyme homogentisic intellectual disability, seizures, and intermittent ataxia if dietary acid oxidase. Without this enzyme, the phenylalanine–tyrosine restrictions of phenylalanine and tyrosine are not implemented. pathway cannot proceed to completion, and homogentisic acid Type 3 tyrosinemia is diagnosed by the presence of elevated accumulates in the blood, tissues, and urine. This condition levels of plasma tyrosine and the presence of the urine metabo- usually does not manifest itself clinically in early childhood, but lites 4-hydroxyphenylpyruvic acid,4-hydroxyphenyllactic, and observations of brown-stained or black-stained cloth diapers 4-hydroxyphenylacetic acid. Genetic studies include testing and reddish-stained disposable diapers have been reported.5 for mutations in the gene for 4-hydroxyphenylpyruvic acid In later life, the brown pigment becomes deposited in the dioxygenase.4 body tissues, particularly noticeable in the ears (ochronosis). Screening tests using MS/MS and molecular diagnostic Deposits in connective tissue, especially the cartilage, eventu- tests are available for tyrosinemia types 1, 2, and 3. See Proce- ally lead to arthritis. A high percentage of people with alkap- dure 9-2 for a qualitative urine screening test for tyrosyluria tonuria develop liver and cardiac disorders.6 using nitroso-naphthol. Homogentisic acid reacts in several of the screening tests historically used for metabolic disorders, including the ferric Melanuria chloride test, in which a transient deep blue color is produced The previous discussion focused on the major phenylalanine– in the tube test. A yellow precipitate is produced in the Clinitest, tyrosine metabolic pathway illustrated in Figure 9-2; however, indicating the presence of a reducing substance. Another screen- as also shown in Figure 9-2 and is the case with many amino ing test for urinary homogentisic acid is to add alkali to freshly acids, a second metabolic pathway also exists for tyrosine. This voided urine and observe for darkening of the color; however, pathway is responsible for the production of melanin, thyroxine, large amounts of ascorbic acid interfere with this reaction. epinephrine, protein, and tyrosine sulfate. Of these substances, Gas chromatography–mass spectrometry (GC-MS) proce- the major concern of the urinalysis laboratory is melanin, the dures are available for quantitating homogentisic acid. Molecular pigment responsible for the dark color of hair, skin, and eyes. genetic testing for the homogentisic acid oxidase gene is available Deficient production of melanin results in albinism. on a clinical basis.7 The ferric chloride test and the silver nitrate Increased urinary melanin (melanuria) darkens the urine. test for homogentisic acid, provided in Procedure 9-3, are The darkening appears after the urine is exposed to air. Elevated screening tests for homogentisic acid. urinary melanin is a serious finding that indicates proliferation Treatment for alkaptonuria is aimed at the specific symp- of the normal melanin-producing cells (melanocytes), produc- toms that are present in each patient. Vitamin C has been used ing a malignant melanoma. These tumors secrete a colorless to treat alkaptonuria because it hinders the accumulation and precursor of melanin, 5,6-dihydroxyindole, which oxidizes to deposition of homogentisic acid.7 melanogen and then to melanin, producing the characteristic dark urine. Technical Tip 9-1. Careful observation during the Alkaptonuria physical component of urinalysis is helpful in cases of alkaptonuria. The appearance of black urine from a pa- Alkaptonuria was one of the six original IEMs described by tient of any age should be reported to a supervisor. Garrod in 1902. The name alkaptonuria was derived from the observation that urine from patients with this condition Technical Tip 9-2. Melanin may react with sodium nitroferricyanide (acetone reagent strip), producing a red color. PROCEDURE 9-2 Nitroso-Naphthol Test for Tyrosine Technical Tip 9-3. It is important to differentiate be- 1. Place five drops of urine in a tube. tween the presence of homogentisic acid and melanin when urine is observed to have turned black upon 2. Add 1 mL of 2.63N nitric acid. standing. 3. Add one drop of 21.5% sodium nitrite. 4. Add 0.1 mL 1-nitroso-2-napthol. 5. Mix. Branched-Chain Amino Acid Disorders 6. Wait 5 minutes. The branched-chain amino acids differ from other amino acids 7. Observe for an orange-red color, indicating tyrosine by having a methyl group that branches from the main metabolites. aliphatic carbon chain (Fig. 9-3 A and B). Two major groups of disorders are associated with errors in the metabolism of the 240 Part Two | Urinalysis urinalysis, notifying the physician about this unusual finding PROCEDURE 9-3 can prevent progression to severe intellectual disability and Homogentisic Acid Test even death. Studies have shown that if MSUD is detected by 1. Place 4 mL of 3% silver nitrate in a tube. the 11th day, dietary regulation and careful monitoring of uri- nary concentrations of keto acid can control the disorder.8 The 2. Add 0.5 mL of urine. 2,4-dinitrophenylhydrazine (DNPH) urine screening test for 3. Mix. MSUD is provided in Procedure 9-4. Newborn screening for 4. Add 10% NH4OH by drops. MSUD is performed with MS/MS. Plasma amino acids (PAA) test- 5. Observe for black color. ing should be performed to assess for elevated levels of branched- chain amino acids (BCAAs) and to detect alloisoleucine. A plasma alloisoleucine level greater than 5 µmol/L is the most specific and sensitive marker for MSUD.9 Molecular testing for branched-chain amino acids. In one group, accumulation of the genes reported in patients with MSUD confirm the diag- one or more of the early amino acid degradation products oc- nosis, provide information about prognosis, and provide curs, as is seen in MSUD. Disorders in the other group are information for genetic counseling.9 termed organic acidemias and result in accumulation of organic Treatment of MSUD is the dietary restriction of foods that acids produced further down in the amino acid metabolic contain BCAAs. Nutritional therapies are prescribed to reduce pathway. toxic metabolites while promoting normal growth. A significant laboratory finding in branched-chain amino acid disorders is the presence of ketonuria in a newborn. Maple Syrup Urine Disease Technical Tip 9-4. As discussed in Chapter 5, as part of the physical examination of urine, the sweet odor of Although maple syrup urine disease (MSUD) is rare, a brief urine is a clue to MSUD. discussion is included in this chapter because the urinalysis laboratory can provide valuable information for the essential early detection of this disease. MSUD is also included in new- Organic Acidemias born screening profiles using MS/MS. MSUD is caused by an IEM, inherited as an autosomal re- Generalized symptoms of the organic acidemias include early cessive trait. The amino acids involved are leucine, isoleucine, severe illness, often with vomiting accompanied by metabolic and valine. The metabolic pathway begins normally, with acidosis; hypoglycemia; ketonuria; and increased serum am- the transamination of the three amino acids in the liver to the monia.10 The three disorders encountered most frequently are keto acids (a-ketoisovaleric, a-ketoisocaproic, and a-keto- isovaleric, propionic, and methylmalonic acidemia. β-methylvaleric). Failure to inherit the gene for the enzyme Isovaleric acidemia may be suspected when urine speci- necessary to produce oxidative decarboxylation of these keto mens, and sometimes even the patient, possess a characteristic acids results in their accumulation in the blood and urine.1 odor of “sweaty feet.” This odor is caused by the accumulation Newborns with MSUD begin to exhibit clinical symptoms of isovalerylglycine due to a deficiency of isovaleryl coenzyme associated with failure to thrive after approximately l week. A in the leucine pathway. The presence of the disease may be suspected from these clin- Propionic and methylmalonic acidemias result from errors ical symptoms; however, many other conditions have similar in the metabolic pathway converting isoleucine, valine, threo- symptoms. Personnel in the urinalysis laboratory, nurses, or nine, and methionine to succinyl coenzyme A. Propionic acid is parents may detect the disease by noticing a urine specimen the immediate precursor to methylmalonic acid in this pathway. that produces a strong odor resembling maple syrup that is The presence of isovaleric, propionic, and methylmalonic caused by the rapid accumulation of keto acids in the urine. acidemias can be detected by newborn screening programs Even though a report of urine odor is not a part of the routine using MS/MS. Alpha amino group Alpha amino group Carboxyl group H H O H H O N C C N C C Figure 9–3 a-Alpha amino acid and H R OH H CH OH branched chain amino acid struc- tures. A. Structure of an a-amino R group H 3C CH3 acid. B. Structure of the branched (variant) A B Leucine group chain amino acid leucine.  Chapter 9 | Urine Screening for Metabolic Disorders 241 Except in cases of Hartnup disease, correction of the un- PROCEDURE 9-4 derlying intestinal disorder returns urinary indican levels to 2,4-DNPH Test for MSUD normal. The inherited defect in Hartnup disease affects not 1. Place 1 mL of urine in a tube. only the intestinal reabsorption of tryptophan but also the renal tubular reabsorption of other amino acids, resulting in a gen- 2. Add 10 drops of 0.2% 2,4-DNPH in 2N HCl. eralized aminoaciduria (Fanconi syndrome). The defective 3. Wait 10 minutes. renal transport of amino acids does not appear to affect other 4. Observe f