Chapter 12 Renal Physiology and Urinalysis PDF

CHAPTER 12 RENAL PHYSIOLOGY AND URINALYSIS 1  Learning Outcomes 1. List the clinical purposes for performing a urinalysis. 2. List the basic anatomic components of the urinary system and the function of each. 3. Differentiate various urine specimen requirements...

CHAPTER 12 RENAL PHYSIOLOGY AND URINALYSIS 1  Learning Outcomes 1. List the clinical purposes for performing a urinalysis. 2. List the basic anatomic components of the urinary system and the function of each. 3. Differentiate various urine specimen requirements for a routine urinalysis, including preservation and storage requirements. 4. Categorize various types of urine collection, including midstream clean-catch, quantitative, and timed specimens, and compare the differences. 5. Correlate normal and abnormal physical properties that might be encountered in urine specimens, with physical findings and chemical and microscopic findings. 6. List the abnormal urine volumes that can result due to certain patient conditions. 7. Define the term specific gravity. 8. Correlate the relationship between urine volume and specific gravity. 9. Discuss the chemical composition of urine. 10. List the chemical tests performed on a urine using the Multistix 10 SG dipstick. 11. Describe conditions when urine should be examined microscopically. 12. Identify the normal crystals found in a urine as discussed in lecture. 2 History of Urinalysis https://youtu.be/X1ZYM7XztSo?si=tKHrdNqHtv7ZNjMi In medieval times, the four humors were a central part of medical diagnosis, and urine color was believed to reveal information about a patient's health. The four humors were black bile, yellow bile, phlegm, and blood. Disease was thought to result from the imbalance of these “humors”, reflected by one of the urine colors. 3  Modern Urinalysis Urinalysis is the physical, chemical, and microscopic analysis of the urine. The Clinical Purposes for performing a urinalysis: ◦ To aid in the diagnosis of disease ◦ To monitor wellness (screening for asymptomatic, congenital, or hereditary disease) ◦ To monitor therapy (effectiveness or complications) Test performance can be manual, semiautomated, or fully automated. 4  Quality Assessment & Quality Control The urinalysis laboratory requires a quality assessment program to ensure that testing results are meaningful. (urinalysis lab is usually part of hematology in some hospitals) The preanalytical stage of urine testing consists of the following six phases: a. Test ordering b. Sample collection c. Specimen transport to the lab d. Specimen receipt in the lab e. Preparation of samples for testing f. Transportation of samples to the urinalysis department for testing Each of these phases contains between 2-5 steps averaging a total of 22 steps until the urine is fully tested and resulted. 5 Quality Assessment & Quality Control Involves: A. Pre-analytic variability B. Analytic variability C. Post-analytical variability 6 Quality Assessment & Quality Control A. Pre-analytical variability in urinalysis is the process of factors that can affect the quality of a urine sample before it's tested, from ordering the test to just before the sample is analyzed. 1. Patient-related factors (diet, exercise, and when the sample is taken) 2. Specimen collection factors (how the sample is transported, processed, and stored) 3. Physiological variables: Factors like age, gender, pregnancy, menstruation, and lifestyle 4. Endogenous variables: Factors like drugs and circulating antibodies Preanalytical variability is a major source of error in laboratory medicine. Some preanalytical variables can be controlled, but others are uncontrollable. It's important to understand the uncontrollable variables so their effects can be separated from disease-related changes. 7 Quality Assessment & Quality Control Here are some examples of how preanalytical factors can affect urinalysis: Urine containers: Containers should be made of non-absorbing materials, free of interfering agents, and designed for easy sampling. Urine color: Colored urine from beet ingestion or bilirubinuria can cause a positive reaction. Urine contamination: Urine contaminated with vaginal discharge or mucus can lead to misinterpretation. Drugs: Some drugs, like nitrofurantion, clavulanic acid, meropenem, and imipenem, can lead to misinterpretation. Vitamin C: Vitamin C intake can decrease the sensitivity of the test. Soap and wash products: Soaps and wash products used for infants can cause false positive screening test results 8 Quality Assessment & Quality Control B. Analytical variability in urinalysis involves several tests to detect and measure various compounds that pass in urine. For Example, a complete urinalysis consists of three examinations: A. physical (This assesses the urine's appearance, including color, clarity, odor, and specific gravity) B. Chemical (This uses a dipstick test to analyze the urine for various chemical components like pH, protein, glucose, red blood cells, and white blood cells). C. Microscopic: This involves looking at a sample of urine under a microscope to identify cells, casts, crystals, and microorganisms present 9 Quality Assessment & Quality Control Remember that test performance can be manual, semiautomated, or fully automated A. Physical Examination: The use of multiple-reagent strips (URINE TEST STRIPS) generally ensures rapid and reliable screening of all specimens. Are used to test urine for a variety of conditions. They can detect the presence of substances like glucose, blood, protein, and ketones, which can indicate issues with the kidneys, urinary tract, or other organs. 10 Quality Assessment & Quality Control B. Chemical Examination: There are a variety of tablets used in urinalysis labs, one I used is the: 1. Ictotest Reagent Tablets: Used to test for bilirubin in urine, which can indicate liver disease. 2. Refractometers (manual and digital) are also used to measure urine specific gravity (SG) and assess hydration status. https://youtu.be/CWlNkIzenzw?si=SOjQJn0955xpGUrb 11 Quality Assessment & Quality Control C. Microscopic examination: A microscopic urinalysis is a part of a complete urinalysis that involves examining a urine sample under a microscope to look for cells, crystals, casts, and other substances. 12 Quality Control Quality control must be done each day with known positive and negative controls to make sure the appropriate “test” is working properly. -using commercially available negative and positive controls that have set values for the test being performed. Record QC data daily. Record the date when a strip or bottle is first opened – write the opened date and refer to manufacturer directions for expiration date and storage If quality control does not come you can not perform the test at hand and must troubleshoot 13 Quality Assessment & Quality Control C. Post-analytical variability: involves the final inspection of results before being reported or released to the provider (patient identification). To improve quality assurance in the post-analytical phase, you can: Implement a barcode ID system to prevent misidentification and inaccurate labeling Use automated transmission of reports to ensure results are shared promptly Develop a troubleshooting plan to identify the source of errors and prevent them from recurring 14 Quality Assessment & Quality Control Post-analytical errors can lead to misinterpretations, delayed diagnoses, inappropriate treatments, and potential harm to patients. 15  Quality Assessment & Quality Control involves: ◦ Preanalytical variability ◦ Analytical variability ◦ Post-analytic variability 16  Renal Anatomy and Physiology o Renal anatomy: o2 kidneys o2 ureters o1 bladder o1 urethra 17  Renal Anatomy and Physiology Renal physiology ◦ The functional unit of the kidney is the nephron, where urine is formed. ◦ The formed urine flows from the kidney into the ureter and is passed to the bladder for temporary storage. ◦ It is eliminated from the body through the urethra. 18  Renal Anatomy and Physiology Renal physiology ◦ Main functions of the kidney: 1. Removal of waste products 2. Retention of nutrients 3. Acid–base balance 4. Water and electrolyte balance 5. Hormone synthesis ◦ These functions are carried out by means of filtration, reabsorption, and secretion. https://youtu.be/FN3MFhYPWWo?si=Y7y_ddMqxlC1hnjV 19  Renal Anatomy and Physiology Histology ◦ All urinary system structures, from the glomerular capsule to the terminal portion of the urethra, are lined with epithelial cells. ◦ Each portion of the urinary system has a specific type of epithelial cell. 20 Renal Anatomy & Physiology The epithelial cells of the urinary system are primarily classified as: 1. transitional epithelial cells, which line the bladder and ureters 2. squamous epithelial cells which are found mostly in the urethra 3. renal tubular epithelial cells originating from the kidney tubules A small number of each type is typically present in urine, but an increased amount can indicate a potential issue like a urinary tract infection or kidney disease. 21 22 Renal Anatomy & Physiology A few of these cells are constantly sloughed off into the urine, but increased numbers or cytologic changes of any of these cells may have clinical significance and may be important in determining the cause of renal dysfunction. 23  Normal urine contains a few cells from the blood and lining of the urinary tract but little or no protein and no casts. Normal urine is usually clear to pale Composit yellow ion of Tests for blood (hemoglobin), nitrite, leukocyte esterase, glucose, ketones, Normal and conjugated bilirubin should all be Urine negative. The reference values shown in the next slide are typical of what may be “normally” encountered when the urine is examined for physical and chemical properties. 24 25 The Composition Concentrated Urine- Concentrated urine is usually a darker shade of yellow or amber in color Concentrated urine is urine that contains more solutes and less water than normal. It can be caused by many conditions, including: Dehydration Diarrhea Excess sweating Heart failure Narrowing of the renal arteries Too much sugar in the urine (glycosuria) Concentrated urine can be a risk factor for kidney stones and can irritate the bladder. It can also smell like ammonia. 26 Composition of Concentrated Urine A laboratory can test the concentration of your urine by measuring its specific gravity, which is the ratio of its density to the density of water. Normal values are usually between 1.000 and 1.030 Microscopic View: When viewed under a microscope, concentrated urine may show the following. 1. Red Blood Cells 2. Urinary casts=RBC casts, WBC casts, Fatty Casts, etc. (Casts are formed when urine becomes highly concentrated and can trap cells in the urine. The size and shape of the cast can indicate the condition of the kidney tubules where it formed 3. Other Substances like bacteria, yeast, parasites, etc. 4. https://youtu.be/f7bQGGW3UTg?si=1K6CJ98XBWAV7Nws 27  Collection and Preservation of Urine Specimens The specimen must be examined when fresh, ideally within 30 minutes, or suitably preserved, such as by refrigeration for up to 6 to 8 hours. Types of urine specimens ◦ Random specimen ◦ First morning specimen ◦ Midstream Clean-catch specimen ◦ 24-hour or timed specimen ◦ Catheter collection specimen ◦ Suprapubic aspiration specimen ◦ Pediatric specimen: U-bag 28  Collection and Preservation of Urine Specimens Containers for urine collection ◦ Urine collection cups ◦ Urinalysis tubes ◦ 24-Hour collection containers ◦ Urine culture containers ◦ Urine transport tubes Urine volume for routine urinalysis ◦ Minimum volume for routine urinalysis is usually 12 milliliters, but 50 milliliters is preferable. ◦ Urine is placed in a disposable centrifuge tube, centrifuged, and concentrated 12-to-1, so that 1 milliliter of sediment is retained for microscopic analysis of the sediment. 29 Collection and Preservation of Urine Specimens Collection of urine specimens: ◦ Routine specimens: a specimen for urinalysis should be collected in a clean, dry container, and the specimen should be fresh. For routine screening, a freshly voided, random, preferably midstream (free flowing-used for culture) urine specimen is suitable. When a culture is ordered with a routine, culture should be done first to avoid contamination. ◦ Collection of timed urine specimens- the patient is instructed about details of the urine collection process if the collection will be done on an outpatient basis. For example, start at 8 am and collect urine for 24 hours. ◦ Collection of urine for culture-a clean-catch, midstream urine specimen Preservation of urine specimens ◦ Decomposition of urine begins within 30 minutes after collection. ◦ The best method of preservation is immediate refrigeration. ◦ Common chemical preservatives are hydrochloric acid, boric acid, and acetic acid. ◦ Example: ◦ https://youtu.be/OUh4_FtQNsA?si=9XjaB6-QLJaefZje 30  Collection and Preservation of Urine Specimens Labeling and processing urine ◦ Labels ◦ Collection date and time ◦ Collection method-UV/UC/Random ◦ Proper preservation- check whether there is a chemical preservative present or whether the specimen has not been refrigerated for longer than 2 hrs after collection. ◦ Light protection -testing of light - sensitive analytes are collected in containers that protect specimen from light 31  Physical Properties of Urine 1. Volume 2. Color 3. Transparency 4. Odor 5. Specific gravity 32 Physical Properties of Urine Volume ◦ In normal adults with normal fluid intake, the average 24-hour urine volume is 1200 to 1500 mL range = 600 to 1600 mL. Color ◦ Result sfrom the presence of three pigments: urochrome, uroerythrin, and urobilin. Transparency ◦ Urine is normally clear but becomes cloudy when it stands. Odor ◦ Normal urine has a characteristic, faintly aromatic odor Specific gravity ◦ Is a measure the amount of the amt of dissolved substances in a solution compared with distilled water with a specific gravity of 1.000 33 Physical Properties of Urine Abnormal volumes ◦ Polyuria: Consistent elimination of an abnormally large volume of urine, more than 2000 mL/24 hours ◦ Diuresis: Any increase in urine volume, even if the increase is only temporary ◦ Oliguria: Excretion of an abnormally small amount of urine, less than 500 mL/24 hours ◦ Anuria: Complete absence of urine formation ◦ Nocturia: Excretion of more than 400 mL urine at night 34  Physical Properties of Urine Abnormal color: ◦ Pale can indicate dilute urine. ◦ Amber can indicate concentrated urine or bilirubin. ◦ Brown can indicate bilirubin or biliverdin. ◦ Orange can indicate urobilin. ◦ Bright orange can indicate azo-containing dyes or compounds. ◦ Red can indicate blood or heme-derived pigment, urates or uric acid, drugs, foodstuffs. ◦ Clear red can indicate hemoglobin. ◦ Cloudy red can indicate red blood cells. ◦ Dark red-brown can indicate myoglobin. ◦ Dark red or red-purple can indicate porphyrins. ◦ Black or dark brown can indicate melanin, homogentisic acid, or phenol poisoning. ◦ Green, blue, or orange can indicate drugs, medications, foodstuffs. 35 Physical Properties of Urine Abnormal transparency ◦ Hazy, cloudy, turbid can indicate mucus, phosphates, urates, crystals, bacteria, pus, fat, casts. Abnormal odor ◦ Odor of ammonia (ammoniacal) can indicate breakdown of urea by bacteria (old urine). ◦ Other abnormal odors can indicate infection. ◦ Sweet or “fruity” can indicate ketone bodies. ◦ Sweaty feet, maple syrup, cabbage or hops, mousy, rotting fish, rancid can indicate a specific amino acid disorder for each scent. 36  Physical Properties of Urine Specific gravity: ◦ Clinical aspects ◦ Used for the information about two general functions: the state of the kidney and the patient’s state of hydration Although specific gravity is a good measure of urine solute concentration, there are other measures, such as osmolality, refractive index, and ionic concentration. All the methods of measuring solute concentration are influenced by the number of molecules present in the solution, in addition to the size and ionic charge. ◦ Use of reagent strips for specific gravity ◦Reagent strips have extensively replaced the refractometer 37  Chemical Tests in Routine Urinalysis Reagent strip tests ◦ Advantages ◦ Convenience (rapid results within a minimum amount of time and personnel; cost-effectiveness; stability (RT, exp 6 months, watch for deterioration); ease in learning to use; disposability; smaller sample volumes required; space savings (storage, use, and clean up) ◦ The timing stated by the manufacturer for each Clinical test. If using an automated instrument It controls the exact time at which all the chemical Reactions are read. https://youtu.be/Kg-8D7_3R3w? si=YOjWDTgHdF0MzpFW 38  Chemical Tests in Routine Urinalysis- Reagent Test Strips pH: ◦ Clinical importance: ◦ Kidneys eliminate excess acid ◦ Causes and effects of acidic urine ◦ Causes and effects of alkaline urine ◦ Reagent strip tests for pH ◦ Principle: double-indicator system: methyl red and bromthymol blue ◦ Additional comments ◦ The specimen must be tested when fresh because bacterial growth may result in a shift to an alkaline pH, giving falsely alkaline values. ◦ Do not wet the reagent strip excessively so that the acid buffer from the protein area runs into the pH area, causing an orange coloration. 39  Chemical Tests in Routine Urinalysis Protein ◦ Clinical importance ◦ Proteinuria may be the result of the following: 1. Glomerular damage 2. Tubular damage 3. Prerenal disorders or overflow from excessive production of low-molecular-weight proteins such as hemoglobin, myoglobin, or immunoglobulins 4. Lower urinary tract disorders 5. Asymptomatic disorders ◦ May be found in young adults after excessive exercise; after exposure to cold; or in orthostatic proteinuria 6. Consistent microalbuminuria in diabetes mellitus 40  Chemical Tests in Routine Urinalysis Proteinuria may be classified as to the amount (quantity) or degree of protein excreted per day (24 hours): ◦ Mild or minimal: less than 1 gram per day ◦ Moderate: 1 to 3 or 4 grams per day ◦ Large or heavy: greater than 3 or 4 grams per day The amount of protein per 100 mL in a random urine specimen is related to 24-hour urine volume. 41  Chemical Tests in Routine Urinalysis ◦ Reagent strip tests for protein ◦ Principle: pH indicators. At a fixed pH, certain pH indicators will show one color in the presence of protein and another color in its absence. This phenomenon is known as the “Protein error of indicators” ◦ Specificity- more sensitive to albumin than other proteins ◦ Sensitivity (minimum detectable level) -Manufacturers’ values 42  Chemical Tests in Routine Urinalysis Blood (hemoglobin and myoglobin) ◦Clinical significance: used as indicators of the state of the kidney and urinary tract. ◦Hematuria- presence of red blood cells in the urine ◦Hemoglobinuria- presence of free hemoglobin in the urine ◦Myoglobinuria- presence of myoglobin in the urine 43  Chemical Tests in Routine Urinalysis Differentiation of red blood cells, hemoglobin, and myoglobin in urine ◦ Reagent strip for blood is positive for all three. ◦ Urine sediment for red cells ◦ Red blood cells: Present ◦ Hemoglobin: Absent (few) ◦ Myoglobin: Absent (few) ◦ Urine appearance ◦ Red blood cells: Cloudy red ◦ Hemoglobin: Clear red ◦ Myoglobin: Clear red-brown 44  Chemical Tests in Routine Urinalysis Nitrite ◦Clinical importance- rapid method of detecting UTI. ◦ Reagent strip tests for nitrite are based on the: ◦ Principle: Greiss test ( this involves a diazo reaction) ◦ Specificity- specific for nitrate ◦ Results= pos (overall pink coloration) or neg ◦ Sensitivity (minimum detectable level) ◦ Conformation- Go for culture- Gram-negative rods 45  Chemical Tests in Routine Urinalysis Leukocyte esterase ◦ Clinical importance ◦ Another means of detecting urinary tract infections ◦ Reagent strip tests for leukocyte esterase ◦ Principle: diazo reaction, similar to the reagent strip tests for nitrate ◦ Specificity: specific for esterase that is present in leukocytes (mostly neutrophils in urine) ◦ Sensitivity (minimum detectable level) ◦ Interferences: false pos results (urinary preservatives such as formalin should not be used) – false neg results (antibiotics, high specific gravity, increased glucose to name a few) 46  Chemical Tests in Routine Urinalysis Glucose (sugar) ◦ The reagent strip tests for urinary sugar are specific for glucose because they are based on the use of the below enzyme. ◦ Reagent strip tests: glucose oxidase Ketone bodies- The reagent strip tests for ketone bodies are based on the Legal test, a color reaction with sodium nitroprusside. 47  Chemical Tests in Routine Urinalysis Bilirubin and urobilinogen ◦Normal liver function ◦Normal formation and excretion of bilirubin and urobilinogen ◦Clinical importance: when liver disease or a hemolytic condition is suspected from the patient’s history. 48 Chemical Tests in Routine Urinalysis Reagent strip test for bilirubin ◦ Principle: diazo reaction Reagent strip test for urobilinogen Principle: modified Ehrlich aldehyde reaction 49  Microscopic Analysis of Urine Sediment Urine sediment refers to all solid materials suspended in the urine specimen. Specimen requirements ◦ Type of specimen-fresh voided, am specimen ◦ Preservation- must be tested within 2 hrs, if not refrigerate ◦ Protection from contamination 50 Microscopic Analysis of Urinary Sediment Normal sediment ◦ The biological part includes RBCs (erythrocytes), WBCs (leukocytes), epithelial cells, fat of biological origin, casts, bacteria, yeast, fungi, parasites, and spermatozoa. ◦ The chemical portion consists of crystals of chemicals and amorphous material. In general, this portion is less important than the biological portion. 51 MICROSCOPIC ANALYSIS OF URINARY SEDIMENT How it's performed The sediment is first examined with low magnification to identify large objects, then examined at high magnification to identify smaller objects Techniques for microscopic examination of sediment ◦ Brightfield microscopy ◦ Phase-contrast microscopy ◦ Plane-polarizing microscopy 52 NORMAL CRYSTALS FOUND IN URINE SEDIMENT AMORPHOUS URATES URIC ACID ACID URATES MONOSODIUM OR SODIUM URATES CALCIUM OXALATE HIPPURIC AMMONIUM BIURATE 53