In stercoral perforation a fecaloma if formed (a localized hard, inspissated, or calcified fecal mass) usually of a diameter equal to or greater than the colonic lumen.  This is thought to cause pressure necrosis on the colonic wall, resulting in perforation.   This then causes both local and sometimes distant extra-luminal air and an adjacent extruded fecal content.  The recto-sigmoid is by far the commonest location.

The absence of another cause for perforation, such as a diverticulum, tumor of inflammed colonic wall is also often a clue.

Laparotomy identified a large faeculoma and a stercoral perforation.