Mechanism of healing following the Snodgrass repair

It has been suggested that healing after tubularized incised plate urethroplasty occurs through re-epithelialization with normal tissue ingrowth or by secondary intent through scarring. We investigated healing in tubularized incised plate urethroplasty.

Hypospadias was created in 5 dogs by incising the ventral urethra, allowed to heal for 21 days and subsequently repaired. During hypospadias creation a tattoo was made longitudinally in the midline dorsal urethral plate. The tattoo was bisected during repair, thus creating 2 distinct lines marking the edges of the incision. A neourethra was tubularized and closed in 2 layers. At 21 days the phallus was harvested, inspected and embedded for histology.

The dorsal urethral plate incision contained 2 distinct lines in all samples representing the area of separation between the native and ingrowing urethras. The distance between these lines was 0.9 +/- 0.1 mm. Proximal urethral lumen diameter (3. 3 +/- 0.1 mm.) was not significantly different from that of the neourethral lumen (3.1 +/- 0.1 mm.). Histologically all repairs had intact squamous epithelium. There was normal appearing subepithelial architecture with scant perivascular lymphocytic infiltrates between the tattoos. In contrast, the area around the sutures showed a desmoplastic (fibroblastic) reaction with an inflammatory, primarily neutrophilic response.

Healing of the incision in the dorsal urethral plate during tubularized incised plate urethroplasty occurs by re-epithelialization with normal tissue ingrowth. In contrast, the sutured closure heals with a desmoplastic and inflammatory response.