Urinalysis Biochemistry Unit 15 PDF

Urinalysis  Outline  Urine composition  Collection and preservation of urine sample  Types of urine specimens  FEME analysis  Physical examination of urine  Chemical analysis of urine  Microscopic examination of urine  Composition of Urine ...

Urinalysis  Outline  Urine composition  Collection and preservation of urine sample  Types of urine specimens  FEME analysis  Physical examination of urine  Chemical analysis of urine  Microscopic examination of urine  Composition of Urine  Composition of urine varies greatly, depending on factors such as diet, nutritional status, metabolic rate, general state of the body, and state of the kidney of its ability to function normally.  Urine is a complex aqueous mixture consisting of 95% water and 5% dissolved substances.  Nitrogenous wastes: urea, uric acid and creatinine  Other normal solutes: Na+, Cl-, K+, PO34-, SO42-, Ca2+, Mg2+, HCO3-  Abnormally high concentrations of any urinary constituents may indicate pathology.  Urine Composition: UREA  A water-soluble compound, CO(NH2)2, that is the major nitrogenous end product of protein metabolism.  Breakdown of proteins by the body, during which amino groups are removed from amino acids and converted into ammonia (NH3), which are toxic at high concentrations. The liver then converts ammonia into urea.  High urea excretion results from high protein diet or conditions associated with an increased protein catabolism (e.g. diabetes mellitus).  Urine Composition: URIC ACID ▪ Uric acid is the end product of purine metabolism. ▪ 75% excreted in urine by the kidneys, the remaining is secreted into the gastrointestinal (GI) tract. ▪ Uric acid (weak acid) exists majorly as urate (present in synovial fluid and plasma). Urate can combine with sodium to form monosodium urate. Crystals of monosodium urate Urine Composition: CREATININE  Creatinine is a break-down product (waste product) of creatine and will be excreted by the kidneys in the urine at a constant rate (depending on muscle mass).  Creatine is a naturally occurring amino acid found in the muscle.  Creatinine is removed from the plasma by glomerular filtration, and NONE is reabsorbed back into the blood.  Hence, plasma creatinine level used to evaluate renal function  Increased plasma creatinine: impaired glomerular filtration →impaired renal function  Serum normal range: male: 0.6-1.2 mg/dL; female: 0.5-1.1 mg/dL  Collection of Urine Specimens  Important considerations in the proper collection & handling of urine:  Container used  Collection procedure  Conditions of storage  Preservation from collection until testing  For routine analysis, urine specimen must be collected in a suitable, clean, dry container.  In most cases, the first specimen freely voided in the morning is preferred.  Explicit instructions to patients not to touch the inside of the container/ container lid with their body.  The specimen must be examined when fresh, ideally within 30 mins, or suitably preserved, such as by refrigeration for up to 6 to 8 hours.  If urine testing cannot be performed within 2 hours of collection, the specimen should be stored at 4 °C as soon as possible after collection  Preservatives Used for Urine Collection Preservative Advantages Disadvantages Boric acid - Prevent cell degradation and Precipitate uric acid overgrowth of organisms Toluene - Preserve acetone Flammable - Prevent bacterial growth Formaldehyde - Preserve formed elements Interferes with chemical teste like glucose, blood and WBC Thymol - Preserve glucose and Interferes with acid sediments precipitation for the protein. Sodium - Preserve the porphyrins and Interferes with other urine bicarbonate urobilinogen constituents  Type of Urine Specimens and Collection Type of Sampling Purpose specimens First morning - Obtained during the - Suitable for microscopic specimen (8- first urination of the day examination and routine hour specimen) - Bladder incubated urinalysis (particularly protein and nitrite test) Random - Obtained at any time - Collected most often for specimen during examination routine urinalysis (chemical screening and microscopic examination) Postprandial - Obtained 2 hours after - To measure the level of specimen meal glucose in the urine  Type of Sampling Purpose specimens Midstream clean - Cleanse the urethral - Suitable for culture and catch specimen area sensitivity testing - Void the first portion of the urine - The urine midstream is collected into a clean container 24-hour - Obtained within 24 - Used in various renal specimen hours function tests (measuring creatinine, urea nitrogen, protein etc.)  Type of Sampling Purpose specimens Catheter - Use of existing catheter - Conducted when a collection or insert a Foley catheter patient is bedridden or specimen into the bladder through cannot urine the urethra to collect urine independently Suprapubic - Needle aspiration through - For bedridden patients aspiration the abdominal wall into the that cannot be specimen bladder catheterized or a sterile specimen is required. Pediatric - A special urine - For infants and small specimen collection bag adhered children to the skin surrounding the urethral area.  Patient collection instructions for midstream, clean-catch urine specimen for culture 1. Wash your hand thoroughly with soap and water. 2. Open the lid of the urine container provided. Be careful to not touch the inside. 3. Cleanse your genital area using the following procedure: MAN a) If you are uncircumcised, draw back the foreskin before cleansing. b) Clean the tip of your penis using a sterile cleansing towelette, beginning at the tip and moving toward the base. Repeat the cleansing process using a second towelette. WOMAN a) Squat over the toilet, and use the finger of one hand to separate and hold open the folds of the skin in your genital area. b) Clean the urinary opening and surrounding area with a sterile cleansing towelette, moving from front to back. Repeat the cleansing process using a second towelette. 4. Discard the towelettes in a trash receptacle (not in the toilet). 5. Begin urinating into the toilet bowl. After the urine has glowed for several seconds into the toilet, catch the midortion of the urine flow in the collection container. When sufficient urine has been collected (approximately half full), continue urinating into the toilet. 6. Tightly screw the cap on the specimen container. 7. Wash your hands thoroughly with soap and water. 8. Promptly give the specimen container to the nurse or laboratory personnel, or leave in the place specified. 9. Ensure that the specimen label contains your proper identification.  FEME ANALYSIS  Urinalysis consists of:  Physical observation (observe the color, odor and transparency)  FEME Chemistry test (using dipstick method)  FEME Microscopic observation (examine particles such as cells, bacteria, cast and crystals) and to confirm the chemical test.  Physical Observation Physical properties of urine include: Volume (Not measured as part of routine urinalysis) Color Transparency Odor Specific gravity Physical Observation: Volume  Normal adults with normal fluid intake, average 24-hour urine volume is 1.2–1.5L.  Abnormality:  Oliguria – urine output < 500mL/day (causes: shock, dehydration, acute renal failure)  Polyuria – urine output > 2L/day (causes: diabetic mellitus, nephrogenic diabetes insipidus, diuretics intake)  Anuria – urine output < 100mL/day (causes: hypovolemia, heart failure, shock, renal failure)  Nocturia – excessive urination during the night (causes: urinary tract infection or bladder infection)  Physical Observation: Color  Normal urine: pale yellow to deep amber (due to presence of urochrome)  Abnormally colored urine may result from pathologic conditions; certain foods and drugs.  Physical Observation: Transparency  Normal urine : clear or transparent  In normal urine: causes of cloudiness include epithelial cells, mucus, sperm and prostatic fluid, normal crystals or contaminants (like body lotions and powders).  In pathological urine: RBCs, WBCs or bacteria.  Physical Observation: Odor  Normal urine: faint aromatic odor (due to presence of volatile acid)  In some pathological conditions, certain metabolites may be produced to give a specific odor such as:  Fruity odor is due to acetone (diabetic urine)  Ammoniacal odor is due to decomposition of urea (urine that is left to standing too long)  Foul odor is due to urinary tract infection  Musty odor is due to phenylketonuria  Maple syrup odor is due to congenital defect in protein metabolism  Physical Observation: Specific Gravity  A measure of the concentration of particles including waste and electrolytes in the urine (High specific gravity – concentrated urine; low specific gravity – dilute urine)  Used to evaluate the concentrating and excretory function of the kidney.  Can be measured by urinometer or dipsticks.  Normal value range: 1.005 – 1.030  Increased urine specific gravity (Hypersthenuria) may indicate:  Dehydration, diabetes mellitus, proteinuria  Decreased urine specific gravity (Hyposthenuria) may indicate:  Overdehydration, Chronic renal diseases (inability to concentrate urine)  Fixed specific gravity = 1.010 (Isosthenuria) may indicate:  Renal tubular damage/ failure of renal medullary function  FEME Chemical Observation Chemical properties of urine include: pH Protein Glucose Ketone Blood Bilirubin Urobilinogen Nitrite Leukocyte esterase  FEME Chemical Observation: pH  Normal value range: 4.6 – 8.0 (average 6.0)  Increased acidity in urine: due to diabetes, starvation, systemic acidosis, or a diet high in meat products and cranberries.  Increased alkalinity in urine: due to bacteria, urinary tract infection, or a diet high in citrus fruits and vegetables.  Urine sample must be fresh.  FEME Chemical Observation: Protein  Normal urine: Negative  Protein is a sensitive indicator of glomerular and tubular renal function.  Healthy individuals excrete