Nephrolithiasis and gestation.

Although both anatomical and physiological changes in pregnancy may predispose to kidney stone formation, it still remains an uncommon occurrence. Correct diagnosis is often difficult. Ultrasound has become the primary diagnostic tool, and a limited study excretory urogram is only necessary for complicated cases. Nephrolithiasis during pregnancy occurs more frequently during the later stages of gestation in multiparas, and without a difference in laterality. Conservative management with bed rest, hydration and analgesia can result in spontaneous passage of the majority of stones in gravidas. Past experience indicates that cystoscopy and/or surgery can usually be done safely when absolutely necessary. Pre-existing stone disease can increase the incidence of maternal urinary tract infections by 10-20%. The most common obstetric complication of stones during gestation is the precipitation of premature labour by renal colic. Unfortunately, most drugs used to treat stone disease are contraindicated in gestation. Experimental evidence suggests that known inhibitors of stone formation are present in gestation, and may help to explain why the incidence of stones is not increased in this particularly hypercalciuric state.