Spontaneous remission of urinary tract obstruction and ascites in a fetus with posterior urethral valves.

We report a case of posterior urethral valves with its typical sonographic findings. The initial diagnosis of an infravesical obstruction was made at 18 weeks gestation based on the finding of an enlarged fetal bladder and bilateral dilated renal pelves. Weekly observations showed no change in bladder size until 27 weeks gestation. At this time there was a significant increase in dilatation, the bladder wall was thickened and at 28 weeks a large amount of fetal ascites was diagnosed, but there was no oligohydramnios. Fetal urine investigations following ultrasound-guided puncture of the fetal bladder revealed hypotonic urine and adequate renal function. Hence no vesicoamniotic drainage was performed. At 32 weeks, spontaneous remission of ascites and reduction of the bladder dilatation were noted. The fetus was delivered vaginally at term. Follow-up of the newborn during the 1st year of life is reported. At the age of 1 year the infant shows good renal function with a serum creatinine of 0.33 mg/dl. This case shows that spontaneous remission of fetal urinary tract obstruction as a consequence of posterior urethral valves is possible. The sequence of events leading to spontaneous remission and the favorable outcome is discussed. Copyright 1991 International Society of Ultrasound in Obstetrics and Gynecology