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Full thickness prolapse is clearly evident with bearing down with eversion of the rectum and a protruding bulge. Therefore, this diagnosis is made clinically. Partial thickness (mucosal) prolapse can sometimes also be severe enough to result in prolapsing mucosa that bulges and is visible external to the anal sphincter on straining (Figure 1a). More typically however, it is less obvious, and is visible on , a real time x-ray taken while defecating. Rectal prolapse may also be more obvious in the relaxed state, such as under general anaesthesia.
Rectal prolapse may be confused easily with prolapsing hemorrhoids. Mucosal prolapse also differs from prolapsing (3rd or 4th degree) hemorrhoids, where there is a segmental prolapse of the hemorrhoidal tissues at the 3, 7 and 11 o’clock positions. Mucosal prolapse can be differentiated from a full thickness external rectal prolapse (a complete rectal prolapse) by the orientation of the folds (furrows) in the prolapsed section. In full thickness rectal prolapse, these folds run circumferential. In mucosal prolapse, these folds are radially. The folds in mucosal prolapse are usually associated with internal hemorrhoids. Furthermore, in rectal prolapse, there is a sulcus present between the prolapsed bowel and the anal verge, whereas in hemorrhoidal disease there is no sulcus. Prolapsed, incarcerated hemorrhoids are extremely painful, whereas as long as a rectal prolapse is not strangulated, it gives little pain and is easy to reduce.
Sphincter function in rectal prolapse is almost always reduced. This may be the result of direct sphincter injury by chronic stretching of the prolapsing rectum. Alternatively, the intussuscepting rectum may lead to chronic stimulation of the rectoanal inhibitory reflex (RAIR – contraction of the external anal sphincter in response to stool in the rectum). The RAIR was shown to be absent or blunted. Squeeze (maximum voluntary contraction) pressures may be affected as well as the resting tone. This is most likely a denervation injury to the external anal sphincter.
