A 32-year-old man comes to the emergency department due to sudden onset of severe right flank pain that radiates toward the groin. He also has gross hematuria but no fever or dysuria. The patient has no significant medical conditions and has never experienced similar symptoms. He takes no medications. Temperature is 36.7 C (98.1 F), blood pressure is 120/80 mm Hg, and pulse is 88/min. The right flank is tender to palpation. There is no costovertebral angle tenderness. Imaging shows a stone in the middle of the right ureter. Which of the following is most likely to be seen on laboratory evaluation of this patient?

Question

A 32-year-old man comes to the emergency department due to sudden onset of severe right flank pain that radiates toward the groin.  He also has gross hematuria but no fever or dysuria.  The patient has no significant medical conditions and has never experienced similar symptoms.  He takes no medications.  Temperature is 36.7 C (98.1 F), blood pressure is 120/80 mm Hg, and pulse is 88/min.  The right flank is tender to palpation.  There is no costovertebral angle tenderness.  Imaging shows a stone in the middle of the right ureter.  Which of the following is most likely to be seen on laboratory evaluation of this patient?

Quizplus · Accepted Answer

Calcium stones represent 75%-80% of all renal calculi and include calcium oxalate and calcium phosphate stones. Hypercalciuria is the most common risk factor for calcium stones in adults. In most patients, the hypercalciuria is idiopathic. Factors can include increased gastrointestinal absorption, increased mobilization of calcium from bone, or decreased renal tubular calcium reabsorption. However, in the absence of an underlying metabolic disorder (eg, hyperparathyroidism), most patients remain normocalcemic due to regulation of plasma calcium levels by vitamin D and parathyroid hormone. (Choice A) Hypercalcemia with resulting hypercalciuria may occur in primary hyperparathyroidism, sarcoidosis, malignancy, and chronic acidemia. However, these are less common causes of nephrolithiasis, and this patient has no symptoms of hypercalcemia (eg, fatigue, constipation) or clinical features to suggest a disorder that might cause hypercalcemia. (Choices B and E) Hyperuricosuria with hyperuricemia can occur with myeloproliferative disorders, tumor lysis syndrome, gout, and Lesch-Nyhan syndrome. High-protein diets typically cause hyperuricosuria with normouricemia. Hyperuricosuria can cause uric acid stone formation and also predisposes to calcium nephrolithiasis (uric acid precipitation acts as a nidus for calcium deposition). (Choice D) Hyperoxaluria can result from a diet high in oxalate (found in foods such as chocolate, nuts, and spinach). Low-calcium diets and intestinal malabsorption syndromes such as Crohn disease can also cause hyperoxaluria as both cause less calcium to be available to bind and trap oxalate in the gut. Hyperoxaluria is a less common risk factor for calcium stone formation than hypercalciuria. Educational objective: Hypercalciuria is the most common risk factor for calcium (calcium oxalate and calcium phosphate) kidney stones in adults; contributing factors may include increased gastrointestinal absorption, increased mobilization of calcium from bone, or decreased renal tubular calcium reabsorption. However, most patients remain normocalcemic due to regulation of plasma calcium levels by vitamin D and parathyroid hormone.

A 32-Year-Old Man Comes to the Emergency Department Due to Sudden