Nephrolithiasis in pregnancy.

Although the anatomical and physiological changes of normal pregnancy may predispose to kidney stone formation, it remains an uncommon occurrence. Correct diagnosis is often difficult. Ultrasonography has become the primary radiological diagnostic tool, with a limited excretory urogram only necessary in 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 most stones in gravidas. Past experience of several groups suggests 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 complications of stones during gestation is premature labour induced by renal colic. Most drugs normally used to treat stone disease are contraindicated in gestation. Known inhibitors of stone formation are present in gestation and may partially explain why the incidence of stones is not increased in this hypercalciuric state.