Fibrosis in Distal Rectum of Anorectal Malformation: A Clinicopathological Study

The distal rectum may have neuromuscular system abnormalities, which could be the causes of constipation of anorectal malformations (ARMs). This study aimed to characterize fibrosis in the distal rectum. To propose new hypotheses for the mechanism of constipation and provide histopathological evidence for the distal rectum resection during anorectoplasty.

Thirty intermediate/high-type ARMs patients were included in this study. The hematoxylin and eosin and Masson trichrome stains were used to conduct the histologic examination. The degree of fibrosis of intestinal wall at different distances from the end of the rectum were evaluated, and correlated with clinical features.

The significant histopathological features of the rectal end were thickened intestinal wall, fibrosis in the submucosa and muscularis propria. All the end rectum had moderate/severe fibrosis, and 78 % of the 4-6 cm distal rectum had no or only mild fibrosis. The distal rectal fibrosis degree wasn't related to the ARMs type (P = 0.639), but was related to the rectal dilation degree (P = 0.026). The number of ganglion cells was correlated with the collagen plexus layer thickness (r = -0.537, P < 0.001). The length and width of fistula were related to collagen deposition (r = 0.503, P = 0.028 and r = -0.618, P = 0.014).

The distal rectum of ARMs exhibited fibrosis, smooth muscle dysplasia, and reduced ganglion cells, which may have clinical consequences such as motility abnormalities and increased wall stiffness. The obstruction and dilation of the rectal end may be closely associated with fibrosis.

Level III.