Diagnosis of Constipation | How to Diagnose Constipation
Diagnosis of constipation
Investigations to assess the structural abnormality of colon
Barium enema
This is a useful investigation in patients with constipation.
It is useful to assess diverticuli, length of strictures and extent of malignancy.
In Hirschsprung’s disease, radiographs show a characteristic spastic, denervated, distal colonic segment with proximal dilatation.
Flexible sigmoidoscopy
It detects only 2/3rd of polyps and cancers of colorectum.
Indications for flexible sigmoidoscopy are
- Screening for carcinomas.
- Rectal bleeding (chronic gross bleeding).
- Radiographic lesion in sigmoid.
- Suspected colitis, normal rectum.
- Complicated sigmoid diverticular disease.
Colonoscopy
It is useful to assess a colonic lesion beyond the reach of the sigmoidoscope.
Indications for colonoscopy are
- Surveillance for neoplasm’s.
- Previous polyps or cancer.
- Inflammatory bowel disease.
- Familial colon cancer syndromes.
- Rectal bleeding.
- Occult blood in stools.
- Acute severe hemorrhage.
- Radiographic lesion above sigmoid.
- Mapping of inflammatory bowel disease.
- Miscellaneous (volvulus and mega colon).
Colonic biopsy
Rectal biopsy obtained from 3cm above the anal verge is useful in patients with suspected Hirschsprung’s disease.
In patients with a structural lesion (malignancy or tuberculosis), biopsy should be obtained from the site of involvement.
Investigations to assess function of colon and anorectum -
Colonic transit studies
These evaluate the time taken by radio-opaque markers to pass through the colon.
Patients with constipation who have normal transit times usually have a psychological basis for their symptoms.
Those with prolonged transit time have slow-transit constipation.
Transit time can also be measured by injecting a non-absorbable isotope into the caecum and observing its movement through the colon at various intervals.
Sensory function
Progressive distension of a balloon placed in the stretch receptors and elicits the urge to pass stools.
Anorectal manometry
This can be combined with balloon distensions studies.
Manometry evaluates recto-sigmoid pressures, rectal compliance and sphincter to assess inappropriate spasm of the sphincter as a cause for constipation.
Defecography
This is a technique in which thick barium is introduced into the rectum and evacuation is monitored on fluoroscopy.
The anorectal angle is seen to widen during defecation.
Failure of the pelvic floor to descend on straining during defecation is seen as decreased pelvic floor descent and prolonged rectal evaluation time.
Leave a Reply