Nephrolithiasis in pregnancy.

Despite anatomic and physiologic changes that predispose to stone formation, nephrolithiasis in pregnancy remains an uncommon occurrence. Stones occur more frequently in multiparas, during the later stages of gestation, and without a difference in laterality. Correct diagnosis can be confusing. Ultrasound has become a primary diagnostic tool and limited excretory urograms are only recommended for complicated cases. Conservative management can result in spontaneous passage of most stones. When necessary, cystoscopy or surgery can be done safely. Preexisting stone disease is associated with an increased incidence of urinary tract infections in pregnancy. Renal colic often precipitates premature labor. Most drugs used to treat stone disease are contraindicated in gestation. Increased quantities of known inhibitors of stone formation are present in gestation and may explain why the incidence of stones is not increased in this hypercalciuric state.