Uronephrology Labs PDF

Uronephrology Labs 1. Utilize renal function tests to differentiate between pre-renal, intrarenal, and post-renal causes of decreased kidney function. a. BMP (for BUN and Creatinine) i. SCr is a product of muscle mass–waste product of muscles, usually excreted in urine (does NOT change rapidly) 1. N...

Uronephrology Labs 1. Utilize renal function tests to differentiate between pre-renal, intrarenal, and post-renal causes of decreased kidney function. a. BMP (for BUN and Creatinine) i. SCr is a product of muscle mass–waste product of muscles, usually excreted in urine (does NOT change rapidly) 1. Normal range: 0.6-1.2mg/dL ii. BUN is a product of breakdown of blood (can change more rapidly) –urea is usually removed from blood and excreted 1. Normal: 8-20mg/dL 2. Elevation = azotemia iii. BUN:Cr Ratio 1. Normal: 10:1 2. >20:1 is pre-renal (blood not getting to kidneys so it cannot filter it out; MC due to dehydration, CHF, or blood loss) 3. 7 is calcium carbonate/calcium phosphate stones iii. Specific gravity- normal range: 1.016-1.022 1. Reflection of hydration status (measure of dissolved substances in urine; concentration)– Higher the number, the more dehydrated (>1.020 = dehydration) 2. False elevation w/ proteinuria iv. Urobilinogen- normal range: 0.3-1.0 1. Elevations w/ liver pathology. Absence indicates biliary obstruction, other than that, this is not really used v. Bilirubin- normal range: negative 1. Positive- intrahepatic cholestasis or obstruction of bile duct, hepatitis 2. False positives- phenothiazines, phenazopyridine (azo) – ruins UA so have to culture it if taking these 3. False negatives- really high Vit C doses vi. Hematuria- normal range: negative 1. Gross (painless) hematuria is indicative of malignancy until proven otherwise, also positive in trauma and w/ stones, but that will be painful 2. False positives- dehydration, exercise, UTI, menstruation 3. Dipstick is sensitive to hemoglobin and myoglobin (rhabo), still send microscopic vii. Leukocyte esterase- normal range: negative 1. detects esterase (enzyme on outside of WBC–if positive, you have WBC for sure since enzyme is positive) 2. indirect test for UTIs and inflammatory processes 3. false positive if contaminated viii. Nitrite- normal range: negative 1. reduction of nitrate to nitrite by bacterial organisms (E. coli, klebsiella, enterobacter, proteus, pseudomonas) 2. indirect test for UTIs → cx urine (if nitrite is +, UTI probably, but culture in case) 3. false negatives from enterococcus (don’t produce nitrite) 4. false positives from strips exposed to air (negative results do not r/o bacteria) ix. Glucose and Ketones- normal range: none 1. Glucosuria occurs above 180 mg/dL a. DM, cushing’s 2. Ketonuria (NO glycogen stores) a. DM (type I), dehydration, carb free diets (keto, epilepsy in kids), pregnancy, alcohol abuse 3. false positives from AZO and levodopa 3. Discuss the purpose, indications, and interpretation of urine culture and sensitivity. a. Order if suspect infection → will tell you what specific bacteria is causing sxs b. Do not assume lab will automatically do it c. Consider it a contaminated sample if multiple types of bacteria are present 4. Describe the role of commonly obtained urinary electrolytes and the fractional excretion of sodium (FENa) in the diagnostic process. a. Urinary K i. Normal range: varies widely ii. Excretion of K is dependent on intake iii. Useful for hypokalemia (not useful in hyperkalemia → usually due to kidney failure or hyperglycemia) 1. If urine K > 10mEq/L usually from renal loss (diuretics, high dose Na, penicillin, metabolic acidosis or alkalosis) 2. If urine K < 10 mEq/L usually from GI loss b. Urinary Na i. Normal range: vaires 1. Can be falsely elevated with diuretics ii. Excretion should be = dietary intake iii. Used to assess volume status or adherence to salt restriction diet for HTN or CHF pt iv. Hyponatremia in serum (blood): 1. If urine Na < 20 mEq/L = volume depletion (urine sodium low because holding onto it in serum to increase volume in body – body also doesn’t have a lot due to vol depletion) 2. If urine Na > 20-40 mEq/L = SIADH (urine Na is high), commonly drug-induced (SSRIs) (because body holding on to a lot of water → so urine will be concentrated with Na because less water to be mixed with) v. Hypernatremia in serum (blood): 1. Low urine sodium = diabetes insipidus (because peeing out a lot of water) c. FENA = Urinary Fractional Excretion of Sodium i. ii. U = urinary, P = plasma iii. Indicates % of Na filtered in the glomerulus and excreted in the urine 1. < 1% hypovolemia (dehydration, CHF) – pre-renal causes 2. > 2-3% acute tubular necrosis (kidney damage) a. Falsely elevated with diuretic therapy