Constipation other imaging findings

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Eiman Ghaffarpasand, M.D. [2]

Barium enema may be helpful in diagnosing underlying diseases of constipation. Findings on a barium enema suggestive of constipation are redundant sigmoid colon, megacolon, megarectum, extrinsic compression, and intraluminal masses. Defecography may be helpful in diagnosing underlying diseases causing constipation. Findings on a defecography suggestive of constipation are poor activation of levator ani muscle, prolonged retention or inability to expel the barium, absence of a stripping wave in the rectum, mucosal intussusceptions, or rectocele. The transit time of the colon can be measured by means of various methods, include radiopaque marker ingestion, radioisotope and scintigraphy study, and wireless motility capsule.

• Barium enema visualizes bowels (rectum, colon, and lower portions of small intestine), using radiopaque enema through the anus.^[2]
• Barium enema may be helpful in diagnosing underlying diseases causing constipation. Findings on a barium enema suggestive of constipation include:^[3]
  • Redundant sigmoid colon
  • Megacolon
  • Megarectum
  • Extrinsic compression
  • Intraluminal masses

• Barium enema is found to be inefficient for diagnosing organic lesions in colorectal portions of patients with constipation.^[4]

• Defecography is an fluoroscopic method of visualizing actual process, rate, and completeness of fecal evacuation along with anorectal abnormalities, and evaluates anorectal muscle contractions and relaxation.^[5]
• The procedure consists of infusing 150 cc contrast with the same consistency as stool into the rectum, asking the subject to evacuate and expel the barium. Fluoroscopic study is done during the evacuation.
• Defecography may be helpful in diagnosing underlying diseases causing constipation. Findings on a defecography suggestive of constipation include:^[6]
  • Poor activation of levator ani muscle
  • Prolonged retention or inability to expel the barium
  • Absence of a stripping wave in the rectum
  • Mucosal intussusceptions
  • Rectocele
• Defecography revealed modest correlation with symptoms of the patients, while it has multiple disadvantages, include:^[5]
  • Radiation exposure
  • Embarrassment
  • Interobserver bias
  • Inconsistent methodology

• Colorectal transit study shows how well food moves through the colon, since the patient recall of bowel movements is mostly not reliable.
• The transit time of the colon can be measured by means of various methods, include radiopaque marker ingestion, radioisotope and scintigraphy study, and wireless motility capsule.

• Radiopaque markers are plastic beads or rings are been contained in a edible capsule.
• There are 20-50 rings in each capsule. There are two methods of diagnosis:
  • Serial abdominal X-rays are taken after ingestion of the Sitzmarks capsule, until all the rings clears from bowels.
  • Single abdominal X-ray on the day 5 (after 120 hours) [preferred method due to less radiation exposure].
• On the day 5, more than 20% rings (more than 6 markers) remaining in the bowels is diagnostic of delayed colonic transit.^[7]

• Scintigraphy method of measuring colonic transit time is visualizing the bowels using gamma-camera in patients who has been administered indium-111-labeled polystyrene pellets.^[8]
• Primary time of imaging is after 24 hours and the normal range of geometric center is 1.7-4.0. Higher amounts of geometric center reflects delayed transit in colon.^[2]
• Scintigraphy application in patients with refractory constipation after laxative treatment is increasing, but high price and low availability prevent the scintigraphy to be the diagnostic study of choice.^[9]

• Wireless motility capsule (WMC) is a non-invasive method for determining not only colonic transit time, but also the primary characteristics of gastric emptying and small intestine transit time.^[10]
• WMC measures the temperature (T), pH, and pressure (P) changes during the gut passage. Therefore, transit time can be studied in each part of gastrointestinal tract, regarding different levels of T, pH, and P.
• WMC is proved to have a reasonable sensitivity in detecting any motility disorder or other underlying diseases causing constipation.^[11]

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