| Anorectal manometry |
Assesses the anal sphincter, pelvic floor, and associated nerves |
Special pressure-sensitive catheter is inserted into the anus to measure resting pressure and squeeze pressure of the sphincter |
Principal purpose in chronic constipation is to exclude adult-onset or short-segment Hirschsprung's disease (congenital megacolon) |
| Balloon-expulsion test |
Demonstrates rectal evacuation |
Either a silicone-filled stool-like device or a 4-cm long balloon filled with 50 mL warm water is placed in the rectum, and the patient is asked to expel the device |
Healthy volunteers can expel the balloon within 1 minute; if the patient is unable to expel the device within 3 minutes, dyssynergic defecation should be suspected |
| Colonic-transit study |
Measures rate at which fecal residue moves through colon |
Serial abdominal radiographs are obtained after the patient swallows a capsule filled with radiopaque markers |
In persons with normal transit time, most markers should pass by day 5; in patients with slow colonic transit, markers will be scattered throughout the colon; in patients with pelvic outlet obstruction, > 20% of markers will be delayed in the rectum |
| Defecography |
Provides information on anatomic and functional changes of the anorectum |
Approximately 150 mL barium is placed in the patient's rectum, and the patient is asked to squeeze, cough, and bear down |
Test may reveal poor activation of levator muscles, prolonged retention of contrast material, or inability to expel the barium in patients with dyssynergic defecation |
| MRI defecography |
Provides a global view of pelvic viscera and musculature |
Rectum is filled with a semi-solid substance that is labeled with a contrast marker. Patient sits on a commode between 2 magnetic rings. A series of MRI images are collected during pelvic floor contraction and defecation. |
This technique allows for analysis of anorectal angle, opening of anal canal, pelvic floor descent during defecation, and functioning of the puborectal muscle. Clear visibility of rectal wall can reveal intussusceptions and rectoceles. Visibility of structures surrounding the rectoanal can reveal enteroceles |
