A 16-year-old boy arrives at the emergency department complaining of left-sided abdominal pain and blood in his urine. The intensity of the pain fluctuates and does not improve with rest or position changes. He has had similar pain episodes in the past, but this is the first time he has had gross hematuria. On physical examination, the left costovertebral angle is tender. The urine was examined under a microscope. Further quantitative laboratory evaluation is most likely to detect which of the following abnormalities in this patient?

Question

A 16-year-old boy arrives at the emergency department complaining of left-sided abdominal pain and blood in his urine. The intensity of the pain fluctuates and does not improve with rest or position changes. He has had similar pain episodes in the past, but this is the first time he has had gross hematuria. On physical examination, the left costovertebral angle is tender. The urine was examined under a microscope.  Further quantitative laboratory evaluation is most likely to detect which of the following abnormalities in this patient?

Quizplus · Accepted Answer

Eductional Objective: Cystinuria is caused by faulty dibasic amino acid transport in intestinal and proximal renal tubular epithelial cells. Due to decreased reabsorption of cysteine from the urine, it frequently manifests as recurrent stone formation at a young age. Pathognomonic hexagonal cystine crystals can be seen in urine, and the sodium cyanide-nitroprusside test can be used to detect excess cystine in the urine.

A 16-Year-Old Boy Arrives at the Emergency Department Complaining of Left-Sided