Although renal ultrasonography (USG) has improved the detection rate of hydronephrosis (HN), its clinical courses and postnatal management remains controversial. Here, we reviewed the clinical features of patients with HN according to the grades.

We retrospectively studied 207 patients who were regularly followed-up among 367 patients with HN detected by renal USG postnatally between April 1998 and December 2007. These patients were grouped into four groups, grades 1-4, according to renal pelvic diameter (RPD). For analysis, each group was merged into two categories (mild: grade 1, 2; severe: grade 3, 4).

During follow-up, 128 episodes of urinary tract infection (UTI) occurred in 91 patients. According to grades from 1 to 4, 35/89 (39.3%), 41/88 (46.5%), 11/22 (50%), and 4/8 (50%), respectively, had UTI, without any significance between the mild and severe groups. However, the severe group presented a higher risk in cumulative episodes of UTI per year ( P =0.041). The spontaneous resolution of HN was observed in 103 (58.8%) of the 175 mild group patients and in 3 (10.7%) of the 28 severe group patients ( P <0.001). Furthermore, the detection rate of prenatal HN by prenatal USG was much higher in patients with severe RPD ( P <0.001).

We found that the severer the grade of HN, the lower was the rate of spontaneous resolution and higher was the frequency of UTI. Therefore, the establishment of guidelines for managing treatments such as antibiotic prophylaxis for patients with HN is needed to improve renal prognosis.