Prognostic value of rectal dilatation and histological features of the rectal wall in dogs with perineal hernia – a cohort and case-control study

Factors involved in recurrence or incomplete resolution of clinical signs after surgical correction of perineal hernia (PH) have not been explored. This study aims to describe the histological features of the rectal wall in dogs with PH and the possible associations between rectal dilatation (RD) severity or histological features and persistence of clinical signs or recurrence in dogs surgically treated for PH. A case-control design was employed to compare the histopathological features of the rectal wall between PH and control dogs. All dogs underwent a full-thickness biopsy of the rectal wall, which was evaluated for inflammation, fibrosis, histomorphology of elastic fibers, and the number of myenteric ganglia. The same PH group was included in a cohort study. The RD was scored by digital rectal examination at T0 (preoperatively), T1 (immediately postoperatively) and T2 (60 days after surgery). A high RD score at T1 and T2 was found to be associated with a negative outcome, and both a high RD score at T1 and T2 and the fibrosis score were associated with recurrence. The histological evaluation revealed a significantly higher inflammation and fibrosis score in the PH group, and a more frequent regular orientation of elastic fibers in dogs belonging to the control group. Notably, the number of ganglia did not differ between the two groups; further studies should explore the neuromuscular efficiency of the rectal wall in dogs bearing PH. Histological assessment of the rectal wall may support veterinary surgeons in developing an accurate prognosis after surgical correction in clinical settings.