POSTNATAL FOLLOW-UP OF HYDRONEPHROSIS DETECTED BY PRENATAL ULTRASOUND- THE NATURAL-HISTORY

Babies with hydronephrosis detected antenatally who were born at or re ferred to our hospital from 1990 to 1995 were followed up with ultraso und (U/S), micturating cystourethrogram (MCU) or nuclear medicine stud ies after birth. One hundred and three patients were diagnosed antenat ally at 17-42 weeks gestation. Twelve cases were excluded from the ana lysis of the results because of incomplete data. Fifty-c,ne (56%) pati ents had hydronephrosis without organic obstruction, and 80% of these became normal in 3 years. Fifteen patients (17%) had a normal scan 4 d ays after birth. This suggests the possibility of antenatal spontaneou s regression. Seven (8%) had a ureterocele and 4 (5%) had pelviureteri c junction (PUJ) obstruction, Four (5%) had vesicoureteric reflux, and 4 (5%) had primary megaureter. Two (2%) had posterior urethral valves (PUV), 3 (3%) had refluxing primary megaureter, and 1 (1%) had urethr al atresia. Fifteen patients (17%) underwent surgical intervention. Si x had a nephrectomy, 1 a vesicostomy, 3 an Anderson-Hynes pyeloplasty, 3 had the ureterocele unroofed, 1 had a ureteric reimplant, and I abl ation of valves. In 42 infants with 60 abnormal kidneys, the renal ant eroposterior diameter of the pelvis was measured. Retrospectively, 48 kidneys diagnosed as having hydronephrosis, antenatally had a renal pe lvis diameter greater than or equal to 4 mm before 33 weeks gestation or greater than or equal to 7 mm after 33 weeks gestation. One patient with PUJ obstruction lost kidney function, but there is no good marke r to detect these patients. Early unroofing of ureteroceles may rescue kidney function. Our follow-up protocol for antenatal hydronephrosis is U/S at 4 days, 1 month and 1 year of age. An MCU is not required un less the ureter is seen on antenatal U/S, If dilatation persists past 1 month, a radionucleotide (MAG3) scan and repeat U/S are performed at 3 months. The methods for assessing obstruction and the indications f or surgical intervention in these patients require reexamination.