Evaluation and follow-up of fetal hydronephrosis

Objective. To determine the antenatal course and neonatal follow-up of isol ated fetal hydronephrosis. Methods. We reviewed our ultrasonography databas e from January 1989 to June 1999 for all cases of unilateral or bilateral f etal hydronephrosis that had at least 1 follow-up ultrasonographic examinat ion. Cases were defined as mild, moderate, or severe depending on the renal pelvis anteroposterior diameter and gestational age. Data were analyzed us ing the chi (2) test with the Fisher exact test where appropriate. Medical records were reviewed, and telephone interviews were performed to determine which infants received follow-up after birth. Results. Of 57,966 ultrasono graphic examinations in 20,049 women during the study period, 393 patients met criteria for evaluation. Of these, 347 (88%) had fetuses with mild hydr onephrosis. Most of these had complete resolution during the pregnancy. For ty patients had fetuses classified as having moderate hydronephrosis, and 6 patients had fetuses with severe hydronephrosis. Of those classified as mo derate hydronephrosis, 15% resolved, 25% improved, 48% remained unchanged, and 12% worsened during the pregnancy. There were no cases of in utero reso lution in the severe group; however, 4 of 6 cases improved to moderate or m ild, and 2 cases remained unchanged. Of the cases identified prenatally, 25 received consultation by a pediatric urologist in the newborn period, and 7 of these required surgical intervention. Conclusions. Our population-base d data suggest that most cases of mild hydronephrosis will resolve before d elivery. In contrast, cases of moderate or severe hydronephrosis are less l ikely to have resolution in utero and are more likely to worsen or remain u nchanged. of those fetuses with persistent hydronephrosis, only a small num ber required some surgical intervention after birth. This information is us eful in counseling the patient whose fetus is noted to have isolated hydron ephrosis.