genitourinary disorders
Urinary Calculi
Key Points
85% of urinary calculi are composed of calcium, mainly calcium oxalate (see table); 10% are composed of uric acid; 2% are composed of cystine; and most of the remainder are composed of magnesium ammonium phosphate (struvite). Larger calculi are more likely to obstruct; however, obstruction can occur even with small ureteral calculi (ie, 2 to 5 mm). Symptoms include hematuria, symptoms of infection, and renal colic. Test usually with urinalysis, imaging, and—if the calculus can later be retrieved—determination of calculus composition. Give analgesics and other medications to facilitate calculus passage (eg, alpha-receptor blockers) acutely and remove calculi that cause infection or persist endoscopically. Decrease the risk of subsequent calculus formation by treating with measures such as thiazide diuretics,potassium citrate, increases in fluid intake, and decreases in dietary animal protein, depending on calculus composition. 