Hydronephrosis of pregnancy.

During pregnancy, up to 90 percent of women have some degree of asymptomatic dilatation of the renal calyces, the renal pelves and the upper two-thirds of the ureters. Such changes occur in the face of increased renal blood flow and are well tolerated. However, the dilatation may be responsible for the increased propensity of asymptomatic bacteriuria to progress to symptomatic infection during pregnancy. Pathologic hydronephrosis manifested by acute pain, refractory urosepsis or even renal failure has been reported. A case of spontaneous extravasation of urine in a 19-year-old primigravida during the 28th week of gestation is reported. The ureteral obstruction in this patient required percutaneous nephrostomy drainage until delivery of the fetus.