Different types of constipation

Classification of constipation:

Constipation can be classified into three broad categories but there is much overlap:

normal transit through the colon (59%)
defecatory disorders (25%)
slowtransit (13%).
Defecatory disorders with slow transit can occur together (3%).


Normal-transit constipation:

In normal-transit constipation, stool traverses the colon at a normal rate, the stool frequency is normal and yet patients believe they are constipated. This is likely to be due to perceived difficulties of evacuation or the passage of hard stools. Patients may complain of abdominal pain or bloating. Normal-transit constipation can be distinguished from slow-transit constipation by undertaking marker studies of colonic transit. Capsules containing 21 radio-opaque shapes are swallowed on days 1, 2 and 3 and an abdominal X-ray obtained 120 hours after ingestion of the first capsule. Each capsule contains shapes of different configuration and the presence of more than 4 shapes from the first capsule, 6 from the second and 12 from the
third denotes moderate to severe slow transit.


Slow-transit constipation:

Slow-transit constipation occurs predominantly in young women who have infrequent bowel movements (usually less than once a week). The condition often starts at puberty and the symptoms are usually an infrequent urge to defecate, bloating, abdominal pain and discomfort, which can make the condition difficult to distinguish from constipation-predominant irritable bowel syndrome. Some patients with severe slow-transit constipation have delayed emptying of the proximal colon and others a failure of 'meal-stimulated' colonic motility. Histopathological abnormalities have been demonstrated in the colons of some patients with severe slow-transit constipation, and some patients have coexisting disorders of small intestinal motility, consistent with a diagnosis of chronic idiopathic intestinal pseudo-obstruction.


Defecatory disorders:

A 'paradoxical' contraction rather than the normal relaxation of the puborectalis and external anal sphincter and associated muscles during straining may prevent evacuation (pelvic floor dyssynergia, anismus). These are mainly due to dysfunction of the anal sphincter and pelvic floor. An anterior rectocele is a common problem where there is a weakness of the rectovaginal septum, resulting in protuberance of the anterior wall of the rectum with trapping of stool if the diameter is more than 3 cm. In some patients the mucosa of the anterior rectal wall
prolapses downwards during straining impeding the passage of stool, whilst in others there may be a higher mucosal intussusception. In some patients the rectum can become unduly sensitive to the presence of small volumes of stool, resulting in the urge to pass frequent amounts of small-volume stool and the sensation of incomplete evacuation.. The defecatory disorders can often be characterized by performing evacuation proctography and tests of anorectal physiology.

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