Congenital pouch colon: an unusual histological finding.

Congenital pouch colon (CPC) is an unusual abnormality in which the colon ends in a pouch-like dilatation and there is generally an associated anorectal malformation. The condition varies from complete absence of normal colon to a nearly normal length of proximal colon with only recto-sigmoid involvement. There is a paucity of data on histological findings in cases of pouch colon. Resected specimens of five cases of CPC were taken. Microscopic sections were stained for H&E and Masson's trichrome stains. We present here an interesting histological finding, namely an unusual muscle layer, inner to the circular muscle layer, in five cases of complete or almost complete CPC and discuss the clinical significance of this finding.