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THE ROLE OF CONTINUOUS ANTIBIOTIC PROPHYLAXIS IN MILD ISOLATED HYDRONEPHROSIS: A RANDOMIZED CONTROL TRIAL

INTRODUCTION AND AIMS: The decision to prescribe continuous antibiotic prophylaxis (CAP) to a newborn with hydronephrosis depends on the chance of having febrile urinary tract infection (fUTI). The association between uropathy and severity of isolated hydronephrosis (IH), characterized by hydronephrosis without ureter and bladder abnormalities, was previously confirmed. In newborns with severe IH, CAP seems to be beneficial. However, the practice of prescribing CAP in infants with mild IH is variable and based on physician discretion as evidence-based guidelines are lacking. The aim of this study was to evaluate the role of CAP in infants with mild IH, defined by the anteroposterior diameter (APD) of renal pelvis < 16 mm and the Society for Fetal Urology (SFU) grade < 4 in renal ultrasounds (RUS).

METHODS: In this open-labeled, randomized controlled trial (clinicaltrials.in.th TCTR20150803001), 80 healthy full-term infants aged younger than 30 days with mild IH were randomized from August 2015 to December 2016 to CAP [2-3 mg/kg of cotrimoxazole once daily] (N=40) or no CAP (N=40) until the age of 12 months. Primary outcome was fUTI or resolution of hydronephrosis defined as APD ≤ 5 mm and SFU grade ≤ 1 in two consecutive RUS.

RESULTS: There was no significant difference in baseline characteristics between the two groups (Table 1).

After randomization, parental unwillingness to have the child on CAP occurred in 6 patients (15%). Thus, 34 patients received CAP whereas 46 patients did not. All infants completed the study without reported adverse effects of CAP. Nine/80 infants (11.3%) developed fUTI. All were male. Cystograms after fUTI showed no reflux. Patient characteristics of infants with fUTI are summarized in Table 2.

Antibiotic resistant bacteria were identified with a higher frequency in CAP than in no CAP groups (p=0.04). By intention-to-treat analysis, fUTI occurred in 5/40 (12.5%) of CAP group vs. 4/40 (10.0%) of no CAP group (p = 0.50). By per-protocal analysis, fUTI occurred in 5/34 (14.7%) of patients who received CAP vs. 4/46 (8.7%) of those who did not (p = 0.31). Overall fUTI-free rates (95% CI) at 6 and 12 months of age were 92.4 (82.6-96.8) % and 85.3 (73.6-92.1) %, respectively, and did not significantly differ between the two groups by both analyses (Figure 1 a-b).

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CONCLUSIONS: The risk of fUTI in infants with mild IH was increased when compared with the normal population, especially in male infants. The results of our study did not support the benefit of CAP in preventing fUTI in mild IH. Moreover, CAP may cause a negative impact of antibiotic resistance on patients.