MLPAO Urinalysis and Body Fluids Case Studies Flashcards

A patient with nephrotic syndrome has urine showing 4+ protein, oval fat bodies, fatty casts, and Maltese cross pattern under polarized light. What do these findings confirm?

Answer: Lipiduria associated with nephrotic syndrome — cholesterol in oval fat bodies produces the characteristic Maltese cross birefringence

Nephrotic syndrome is characterized by massive proteinuria (>3.5 g/day), hypoalbuminemia, edema, and hyperlipidemia with lipiduria. Oval fat bodies (lipid-laden tubular cells/macrophages), fatty casts, and free fat droplets in urine confirm lipiduria. Under polarized light, cholesterol crystals within these structures produce the characteristic Maltese cross (four-quadrant bright pattern).

A urine specimen is received 6 hours after collection at room temperature. What changes would be expected?

Answer: Increased bacteria and pH, decreased glucose, decomposed casts and cells, and possible crystal formation due to pH change

Delayed analysis at room temperature causes multiple artifacts: bacterial multiplication (converting urea to ammonia, raising pH), glucose consumption by bacteria, decomposition of RBCs, WBCs, and casts, possible precipitation of amorphous phosphates (from increased pH), and production of nitrite. These changes can significantly alter all three components of the urinalysis.

A patient with diabetes has a urine showing 2+ glucose, 2+ ketones, specific gravity 1.035, and pH 5.0. What is the clinical correlation?

Answer: Diabetic ketoacidosis (DKA) or poor glycemic control — glucosuria with ketonuria in concentrated, acidic urine

Glucosuria (blood glucose exceeds renal threshold) with ketonuria (increased fat metabolism due to insulin deficiency) in concentrated, acidic urine suggests poor glycemic control or impending/active diabetic ketoacidosis. The high specific gravity indicates dehydration (common in DKA due to osmotic diuresis). Blood glucose and blood gas analysis should be performed urgently.

A body fluid from a knee joint aspiration has a WBC count of 75,000/µL with 95% neutrophils and a positive Gram stain showing gram-positive cocci in clusters. What is the diagnosis and management?

Answer: Septic arthritis requiring urgent surgical drainage and IV antibiotics

WBC >50,000/µL with >90% neutrophils combined with a positive Gram stain confirms septic arthritis. Gram-positive cocci in clusters suggest Staphylococcus aureus, the most common cause. This is an orthopedic emergency requiring urgent joint drainage (surgical washout or serial aspirations) and IV anti-staphylococcal antibiotics to prevent joint destruction.

A urine microscopy shows hexagonal, colourless crystals in acidic urine from a young patient with recurrent kidney stones. What is the diagnosis?

Answer: Cystinuria with cystine crystals

Hexagonal, colourless crystals in acidic urine are pathognomonic for cystine. Cystinuria is an inherited autosomal recessive disorder of amino acid transport affecting reabsorption of cystine, ornithine, lysine, and arginine (COLA) in the renal tubules. Cystine is poorly soluble, forming recurrent stones. Confirmatory testing includes the cyanide-nitroprusside test and 24-hour urine cystine.

An ascitic fluid has a SAAG of 15 g/L, total protein 18 g/L, and WBC 150/µL with lymphocyte predominance. What is the most likely diagnosis?

Answer: Cirrhotic ascites (portal hypertension) — high SAAG with low protein

A SAAG ≥11 g/L indicates portal hypertension with 97% accuracy. The high SAAG (15 g/L) with low protein (18 g/L) is classic for cirrhotic ascites. The WBC <250/µL with lymphocyte predominance excludes SBP. Portal hypertensive ascites typically has low protein because the diseased liver produces less albumin and the transudate mechanism produces a low-protein fluid.