The plica transversalis recti (K Kohlrausch's plica or Houston's valve) shows a preferential double (52%) rather than triple (38%) localization and is absent in as much as 16% of cases. It is alternatively found on the left and right sides, 3-4 and 8-9 cm from the anal margin respectively. Both its detection rate and radiographic features depend on the technique used as follows: (a) 92%, contour indentation and/or linear filling defect, 4 to 5 mm thick at barium enema studies; (b) 67%, the same as in (a) plus 1/3 narrowing of the maximum diameter at defecography; and (c) 90%, two opposite and overlapping folds at coronal CT. Evidence is given that neither organic nor functional anorectal conditions affect the radiographic appearance of the fold, its likely role being to fix the proximal margins during the expulsion of feces.