A 45-year-old woman comes to the emergency department with vomiting and severe right flank pain that radiates to her groin. The patient has been to the emergency department twice in the past due to similar episodes of renal colic. Previous imaging showed radio-opaque stones. The stones passed spontaneously, and she did not seek further medical care. Imaging now shows another ureteral stone. A 24-hour urine collection shows urinary calcium excretion of 350 mg (normal is

Question

A 45-year-old woman comes to the emergency department with vomiting and severe right flank pain that radiates to her groin.  The patient has been to the emergency department twice in the past due to similar episodes of renal colic.  Previous imaging showed radio-opaque stones.  The stones passed spontaneously, and she did not seek further medical care.  Imaging now shows another ureteral stone.  A 24-hour urine collection shows urinary calcium excretion of 350 mg (normal is <250 mg in women).  Laboratory results show a serum calcium concentration of 8.9 mg/dL; serum parathyroid hormone is normal.  Further investigations fail to reveal a cause of the hypercalciuria.  Apart from advising increased fluid intake, which of the following interventions will benefit this patient?

Quizplus · Accepted Answer

11ec25c8_d13b_6410_bc81_c1973c0b6855_MD0003_00 Renal stone formation involves the abnormal excretion of stone-forming salts and/or a deficiency of urinary inhibitors of crystal formation due to metabolic disorders or dietary factors. Calcium stones are the most common type of stone seen and usually present in the third or fourth decade of life. Most patients have hypercalciuria (24-hour urinary calcium excretion >4 mg/kg). This patient most likely has recurrent calcium stones due to idiopathic hypercalciuria, which is best treated with increased fluid intake, dietary sodium and protein restriction, and thiazide/amiloride diuretics. The mild volume depletion caused by thiazide diuretics leads to a compensatory rise in reabsorption of sodium and water with resulting increased passive reabsorption of calcium. Thiazides are also thought to modulate calcium channels on the tubular membrane. Lowering the urinary concentration of calcium reduces its precipitation as insoluble calcium salts. thiazide diuretics (Choices A and C) Aldosterone antagonists like spironolactone or eplerenone are potassium-sparing diuretics. Furosemide is a loop diuretic. They all increase urinary calcium excretion, potentially worsening stone formation. (Choice B) Increased sodium load from high dietary sodium reduces reabsorption of sodium and thereby reduces the passive reabsorption of calcium. Typically <100 mEq/day of sodium is recommended. (Choice D) Calcium binds with oxalate in the gut to form unabsorbable calcium oxalate. Reduced dietary calcium leads to an increase in oxalate absorption in the gut, which is then excreted into the urine and binds urinary calcium to form calcium oxalate stones. Excess calcium supplementation (ie, not from food sources) is also associated with increased stone formation. Educational objective: Measures to prevent urinary calcium stone formation include increasing fluid intake, following a low-sodium, low-protein diet, maintaining moderate calcium intake, and taking thiazide diuretics to lower urinary calcium excretion. References: Medical management to prevent recurrent nephrolithiasis in adults: a systematic review for an American College of Physicians Clinical Guideline. (http://www.ncbi.nlm.nih.gov/pubmed/23546565) From crystalluria to kidney stones, some physicochemical aspects of calcium nephrolithiasis. (http://www.ncbi.nlm.nih.gov/pubmed/25374820)

A 45-Year-Old Woman Comes to the Emergency Department with Vomiting