Impact of second-layer coverages on complication rates in primary tubularized incised plate urethroplasty (TIPU) for distal and midpenile hypospadias repair: a systematic review

This systematic review assesses the impact of different second-layer coverage techniques on complication rates following primary tubularized incised plate urethroplasty (TIPU) for distal and midpenile hypospadias. A systematic search of PubMed, EMBASE, Cochrane Central, and Scopus was conducted in August 2024. Studies were included if they reported outcomes of single- or double-layer neourethral coverage in primary TIPU for distal or midpenile hypospadias. A narrative synthesis was performed due to study heterogeneity. Forty studies met inclusion criteria. In distal hypospadias, single-layer coverage yielded urethrocutaneous fistula (UCF) rates below 10% in most cases. Meatal stenosis reached 33.3% but was uncommon with dorsal dartos (DD) flaps. Double-layer coverage, especially with double DD flaps, showed lower UCF rates (0–12)% and minimal stenosis. For midpenile hypospadias, single-layer coverage showed higher UCF rates (0–36.4%), with DD flaps performing worse (12.5–36.4%) than tunica vaginalis (TV) flaps (0–3.1%). Double-layer techniques consistently reduced UCF to < 5%, with double DD flaps showing no fistula or stenosis. In conclusion, second-layer coverage, particularly double layer, reduces complications in TIPU. The DD flap remains most commonly used due to its accessibility, while the technically demanding TV flap shows promising results. Further high-quality data are needed to identify the optimal technique.