Renal Disorders .pdf

Renal DISORDER THE NEPHRON The nephron is the functional unit of the kidney, is composed of vascular components (the glomerulus and peritubular capillaries) and tubular components. Fluid and solutes are filtered from the glomerular capillaries into the tubular structures, in which urine i...

Renal DISORDER THE NEPHRON The nephron is the functional unit of the kidney, is composed of vascular components (the glomerulus and peritubular capillaries) and tubular components. Fluid and solutes are filtered from the glomerular capillaries into the tubular structures, in which urine is formed for elimination from the body. In the tubular portion of the nephron, substances needed by the body are reabsorbed into the peritubular capillaries, whereas unneeded substances are secreted from the peritubular capillaries into the urine filtrate. Tubular Components of the Nephron The nephron tubule is divided into four segments: 1. A highly coiled segment called the proximal convoluted tubule, which drains the Bowman capsule 2. A thin, looped structure called the loop of Henle 3. A distal coiled portion called the distal convoluted tubule 4. A collecting tubule (or collecting duct), which joins with several tubules to collect the filtrate6 NORMAL VALUES FOR ROUTINE URINALYSIS Congenital Disorders of the Kidneys The kidneys begin to develop early and begin producing urine by week 13 of gestation. Fetal urine is excreted into the amniotic cavity and is the main constituent of amniotic fluid The relative amount of amniotic fluid can provide information about the status of fetal renal function Agenesis and Hypoplasia Dysgenesis refers to a failure of an organ to develop normally. Agenesis refers to failu.re of an organ to develop at all. Renal agenesis often have characteristic facial features, previously called Potter syndrome, resulting from the effects of oligohydramnios. Renal hypoplasia, the kidneys do not develop to normal size and contain fewer renal lobes Renal Dysplasia Renal dysplasia is caused by an abnormality in the differentiation of kidney structures during embryonic development. It is characterized by undifferentiated tubular structures surrounded by primitive embryonic tissue and may contain smooth muscle and cartilage. Noncommunicating cysts of varying size may replace normal renal parenchyma. A multicystic kidney is one in which the kidney is replaced by cysts and does not function Alterations in Kidney Position and Form One or both kidneys may be in an abnormal position. An ectopic kidney may be located within the pelvic cavity on the same or opposite side of its ureter, or it may be located within the margins of the iliac crest or in the abdominal or chest cavities. The most common alterations in kidney form—occurring in approximately 1 of every 500 births—is an abnormality called a horseshoe kidney This condition usually does not cause problems unless there is an associated defect in the renal pelvis or other urinary structures that obstructs urinary flow. Inherited Cystic Kidney Diseases The inherited cystic kidney diseases are single-gene disorders transmitted through Mendelian patterns and include autosomal dominant and recessive polycystic kidney disease. Polycystic kidney diseases are a group of kidney disorders characterized by fluid-filled sacs or segments that have their origins in the tubular structures of the kidney. The cysts may be single or multiple and can vary in size from microscopic to several centimeters in diameter. autosomal dominant polycystic kidney disease (ADPKD) In the autosomal dominant polycystic kidney disease (ADPKD), thousands of large cysts are derived from every segment of the nephron. The tubule wall (which is lined by a single layer of tubular cells) expands and then rapidly closes the cyst off from the tubule of origin Autosomal dominant polycystic kidney disease (ADPKD), also known as adult polycystic disease, is the most common hereditary form of renal cystic disease. The cause of ADPKD was originally believed to be mutations in the PKD1 and PDK2 genes, thought to account for 85% and 15% or cases, respectively. Disease progression is typically more rapid in people with type I disease. autosomal recessive polycystic kidney disease In the autosomal recessive polycystic kidney disease, small, elongated cysts form in the collecting ducts and maintain contact with the nephron of origin. In acquired cystic disease, simple cysts develop in the kidney as a consequence of aging, dialysis, or other conditions that affect tubular function. Clinical Manifestations. Typically, the progress of the kidney disease is slow, and end-stage renal failure (ESRF) is uncommon for adults before 40 years of age. Initially, the person with renal cysts is generally asymptomatic, with normal kidney and liver function. As the kidney disease progresses, the manifestations of ADPKD include pain from the enlarging cysts that may reach debilitating levels, episodes of gross hematuria from bleeding into a cyst, infected cysts from ascending UTIs, and hypertension resulting from compression of intrarenal blood vessels with activation of the renin–angiotensin mechanism. The kidneys are usually enlarged in people with ADPKD and may achieve enormous sizes.The external contours of the kidneys are distorted by numerous cysts, some as large as 5 cm in diameter, which are filled with straw-colored. As the disease continues to progress, extrarenal manifestations such as aneurysms are frequent Autosomal Recessive Polycystic Kidney Disease Clinical Manifestations. The typical infant with ARPKD presents with bilateral flank masses, accompanied by severe renal failure. The very large size of the kidneys restricts lung development and function. There are also varying degrees of liver fibrosis and portal hypertension. Potter facies and other defects associated with oligohydramnios may be present. Hypertension is usually noted within the first few weeks of life and is often severe. Death during the perinatal period often results from pulmonary hypoplasia. Exceptional cases of ARPKD manifest in older children and adults. Nephronophthisis–Medullary Cystic Disease Complex The nephronophthisis (NPHP)–medullary cystic disease complex is a group of renal disorders that have their onset in childhood. Common characteristics of this autosomal recessive kidney disease are small, shrunken kidneys and the presence of a variable number of cysts, usually concentrated at the corticomedullary junction. NPHP is a progressive form that typically advances to end-stage renal disease prior to adulthood. Affected children present first with polyuria, polydipsia, and enuresis (bed- wetting), which reflect impaired ability of the kidneys to concentrate urine. Other manifestations of the disorders include salt wasting, growth retardation, anemia, and progressive renal insufficiency. Simple and Acquired Renal Cysts Simple cysts are a common disorder of the kidney. The cysts may be single or multiple, unilateral or bilateral, and they usually are less than 1 cm in diameter, although they may grow larger. Most simple cysts do not produce signs or symptoms or compromise renal function. When symptomatic, the cysts may cause flank pain, hematuria, infection, and hypertension related to ischemia-produced stimulation of the renin– angiotensin system. They are most common in older adults. Although the cysts are benign, they may be confused clinically with renal cell carcinoma. An acquired form of renal cystic disease occurs in people with ESRD who have undergone prolonged dialysis treatment. Although the condition is largely asymptomatic, the cysts may bleed, causing hematuria. Tumors, usually adenomas but occasionally adenosarcomas, may develop in the walls of these cysts. OBSTRUCTIVE DISORDERS Urinary obstruction can occur in people of any age and can involve any level of the urinary tract, from the urethra to the renal pelvis. Obstruction may be sudden or insidious, partial or complete, and unilateral or bilateral. The conditions that cause urinary tract obstruction include congenital anomalies, urinary calculi (i.e., stones), pregnancy, benign prostatic hyperplasia, scar tissue resulting from infection and inflammation, tumors, and neurologic disorders such as spinal cord injury. Obstructive uropathy is usually classified according to site, degree, and duration of obstruction Causes of Urinary Tract Obstruction Hydronephrosis Hydronephrosis refers to urine-filled dilation of the renal pelvis and calices associated with progressive atrophy of the kidney because of obstruction of urine outflow. The degree of hydronephrosis depends on the duration, degree, and level of obstruction. The condition is usually unilateral. When the obstruction affects the outflow of urine from the distal ureter, the increased pressure dilates the ureter, a condition called hydroureter Bilateral hydroureter may develop as a complication of bladder outflow obstruction because of prostatic hyperplasia. Clinical Manifestations The manifestations of urinary obstruction depend on the site of obstruction, the cause, and the rapidity with which the condition developed. Urinary tract obstruction encourages the growth of microorganisms and should be suspected in people with recurrent UTIs. Hypertension is an occasional complication of urinary tract obstruction. Pain Renal Calculi The most common cause of upper urinary tract obstruction is urinary calculi. It is thought to encompass a number of factors, including increases in blood and urinary levels of stone components and interactions among the components, anatomic changes in urinary tract structures, metabolic and endocrine influences, dietary and intestinal absorption factors, and UTIs. Several factors contribute to stone formation, including a supersaturated urine, presence of a nucleus for crystal formation, and deficiency of inhibitors of stone formation Kidney stone formation requires a supersaturated urine and an environment that allows the stone to grow. The risk for stone formation is increased when the urine is supersaturated with stone components (e.g., calcium salts, uric acid, magnesium ammonium phosphate, cystine). Supersaturation depends on urinary pH, temperature, solute concentration, ionic strength, and complexation. The greater the concentration of two ions, the more likely they are to precipitate. Types of Stones Clinical Manifestations Pain Pain and more pain. Renal colic is the term used to describe the colicky pain that accompanies stretching of the collecting system or ureter. The symptoms of renal colic are caused by stones 1 to 5 mm in diameter that can move into the ureter and obstruct flow. Classic ureteral colic is manifested by acute, intermittent, and excruciating pain in the flank and upper outer quadrant of the abdomen on the affected side. The pain may radiate to the lower abdominal quadrant, bladder area, perineum, or scrotum in the man. The skin may be cool and clammy, and nausea and vomiting are common. URINARY TRACT INFECTIONS Most uncomplicated lower UTIs are caused by E. coli, and complicated UTIs are caused by a number of pathogens such as Klebsiella pneumoniae, Enterococcus faecalis, Enterobacter spp., Proteus mirabilis, and Pseudomonas aeruginosa. Most UTIs are caused by bacteria that enter through the urethra. Bacteria can also enter through the bloodstream usually in immunocompromised people and neonates. Although the distal portion of the urethra often contains pathogens, the urine for Pyelonephritis Pyelonephritis refers to infection of the kidney parenchyma and renal pelvis. There are two forms of pyelonephritis—acute and chronic. Acute Pyelonephritis Acute pyelonephritis represents an upper UTI, specifically the renal parenchyma and renal pelvis. Risk factors for complicated acute pyelonephritis are those that increase the host’s susceptibility or reduce the host response to infection. People with diabetes mellitus are at increased risk. A less frequent and more serious type of acute pyelonephritis, called necrotizing pyelonephritis, is characterized by necrosis of the renal papillae. It is particularly common in people with diabetes and may also be a complication of acute pyelonephritis when there is significant urinary tract obstruction. Etiology. Gram-negative bacteria, including E. coli and Proteus, Klebsiella, Enterobacter, and Pseudomonas species, are the most common causative agents. The infection usually ascends from the lower urinary tract, with the exception of Staphylococcus aureus, which is usually spread through the bloodstream. Factors that contribute to the development of acute pyelonephritis are catheterization and urinary instrumentation, vesicoureteral reflux, pregnancy, and neurogenic bladder. Hematogenous acute pyelonephritis occurs most often in debilitated, chronically ill people and those receiving immunosuppressive therapy. Immunosuppression favors the development of subclinical (silent) pyelonephritis and infections caused by nonenteric, aerobic, gram-negative rods, and Candida. Clinical Manifestations Acute pyelonephritis tends to present with an abrupt onset of chills, high fever, and an ache or tenderness in the costovertebral angle (flank area of the back) that is unilateral or bilateral. Lower urinary tract symptoms, including dysuria, frequency, and urgency, also are common. Nausea and vomiting may occur along with abdominal pain. Palpation or percussion over the costovertebral angle on the affected side usually causes pain. Pyuria occurs but is not diagnostic because it also occurs in lower UTIs. Chronic Pyelonephritis Chronic pyelonephritis represents a progressive process. There is scarring and deformation of the renal calyces and pelvis The disorder appears to involve a bacterial infection superimposed on obstructive abnormalities or vesicoureteral reflux. Chronic obstructive pyelonephritis is associated with recurrent bouts of inflammation and scarring, which eventually lead to chronic pyelonephritis. Wilms Tumor Wilms tumor (nephroblastoma) is one of the most common primary neoplasms of young children. It usually presents between 3 and 5 years of age and is the most common malignant abdominal tumor in children. It may occur in one or both kidneys. The incidence of bilateral Wilms tumor is 5% in sporadic cases and up to 20% in familial cases.5  Stage I tumors are limited to the kidney and can be excised with the capsular surface intact. Stage II tumors extend into the renal capsule, but can be excised. Stage III tumors extend to the abdomen, but not beyond. Stage IV tumors have undergone hematogenous metastasis, most commonly involving the lung. Stage V tumors have bilateral involvement when diagnosed.