Answer to Quiz from March 10, 2012: 1. C, 2. B, 3 E, 4. A, 5. D.
The Question
For each patient with renal colic described below, select the most likely finding in the urine sediment (A-E).
A. Envelope- and needle-shaped crystals
B. Coffin lid-shaped crystals
C. Hexagonal plate-like crystals
D. Spherical crystals
E. Red blood cells, no crystals
1. 16-year-old girl with recurrent nephrolithiasis since early childhood. Her parents are second cousins. Her urine turns purple color with addition of sodium nitroprusside.
2. 85-year-old man with an ileal loop diversion and chronic pyuria.
3. 26-year-old woman with sickle cell disease, polyuria and chronic renal failure, who presents with macroscopic hematuria and renal colic.
4. 30-year-old man brought in inebriated without alcoholic fetor. His urine fluoresces under a Wood’s light.
5. 70-year-old female with congestive cardiac failure and osteoarthritis. Her medications include furosemide, hydrochlorothiazide, triamterene, hydralazine and naprosyn.
Explanation
The 16-year-old girl has cystinuria, an autosomal recessive disorder, which is suggested by the family history of consanguinity. Cystine in the urine, which can be qualitatively detected by a positive nitroprusside test, appears as hexagonal plate-like crystals. Patients with ileal loop diversions, as in the 85-year old man, have chronic pyuria, recurrent urinary tract infections, and struvite stones. Crystals of struvite may be seen in the urine and have a coffin-lid appearance. Patients with ethylene glycol poisoning, usually due to ingestion of anti-freeze, often appear inebriated but have no alcoholic fetor. As fluorescein is used as an additive in automotive antifreeze, the urine of such patients may fluoresce under a Wood’s light. Ethylene glycol is metabolized to oxalate, resulting in the appearance of calcium oxalate dihydrate (envelope-shaped) and monohydrate (needle-shaped) crystals in the urine. Triamterene may also cause crystalluria and obstructive uropathy, particularly in patients who are also on thiazides or non-steroidal anti-inflammatory drugs, and appear as spherical crystals. The 26-year-old woman with sickle cell disease likely has tubulointerstitial nephropathy causing a urinary concentrating defect and chronic renal failure. Papillary necrosis may occur in this setting, likely due to medullary ischemia, and the sloughed papilla may cause hematuria and renal colic that is indistinguishable from symptoms due to passage of a ureteric stone, or a blood clot.
(Source: Dr. Alan Yu, University of Kansas Medical Center, USA)
