Late Recurrence of Symptomatic Hydronephrosis in Patients With Prenatally Detected Hydronephrosis and Spontaneous Improvement

PURPOSE: Most prenatal hydronephrosis improves or resolves spontaneously with conservative treatment. However, late recurrence of prenatal hydronephrosis sometimes develops after improvement. To define the need for continuous observation after improvement of hydronephrosis, long-term followup was carried out in children with prenatally diagnosed hydronephrosis. MATERIALS AND METHODS: We retrospectively evaluated 344 cases initially presenting between July 1991 and June 2004 with prenatally detected hydronephrosis that persisted postnatally. Subjects underwent periodic assessment of hydronephrosis using ultrasonography and diuretic renography. Indications for surgery were associated symptoms, enlarged renal pelvis, worsening hydronephrosis on sequential ultrasonography and decrease in differential renal function greater than 5%. Mean duration of followup was 10.1 years. RESULTS: Of the 394 kidneys followed nonoperatively 4 (1%) displayed worsened hydronephrosis after spontaneous improvement. Initial grade of hydronephrosis was grade I in 1 patient, grade II in 1, grade III in 1 and grade IV in 1. On serial ultrasonographic followup hydronephrosis worsened to grade IV in 3 kidneys and to grade III in 1 kidney. Mean patient age at worsening of hydronephrosis was 40 months (range 22 to 60). All 4 patients presented with clinical symptoms. All patients who underwent pyeloplasty displayed no symptoms, and had improved hydronephrosis after pyeloplasty. CONCLUSIONS: Prenatally detected hydronephrosis can worsen after spontaneous postnatal improvement. Long-term followup is not required after improvement of prenatal hydronephrosis. However, pediatric urologists need to tell the parents that the child should undergo ultrasonography if clinical symptoms develop.