Assessment of colonic transit in a patient presenting with constipation is recommended only after excluding a defecatory disorder and after treatment with laxatives and first-line pharmacologic agents fails, or after pelvic floor training in those with a defecatory disorder fails, according to a new medical position statement from the American Gastroenterological Association.
This recommendation is in contrast to the previous AGA medical position statement on constipation, which called for earlier assessment for colonic transit.
The change is one of only three substantive changes to the statement, which is published in the January issue of Gastroenterology; the others are the use of GRADE (Grading of Recommendations Assessment, Development, and Evaluation), which rates for each recommendation, its strength and quality of evidence, and the inclusion of newer agents; and deletion of certain older agents in treatment recommendations.
The colonic transit assessment recommendation is based in part on concerns about potential long-term side effects associated with newer agents that might be prescribed in patients with slow colonic transit.
"At present, the medical approaches used for managing normal and slow-transit constipation are similar. However, the major pharmacological trials in chronic constipation did not assess if the response to therapy is influenced by colonic transit. While newer agents may also be considered without assessing colonic transit, the long-term side effects, if any, of these agents are unknown and exposure to such potential risks might be more appropriate in patients with the more severe forms of constipation associated with slow transit," according to the statement.
Also, up to 50% of all patients with defecatory disorders have slow colonic transit as well, thus slow colonic transit does not exclude a defecatory disorder – and it also does not alter the management of defecatory disorders.
As for the approach to assessing for slow transit once a defecatory disorder is excluded, the statement says, "consideration should be given to assessing colonic transit by radiopaque markers, scintigraphy, or a wireless motility capsule in patients with persistent symptoms on laxatives."
Identifying slow colonic transit can reassure patients about the pathophysiology of their symptoms and also can serve as an objective marker for documenting response to treatment and provide physicians with the appropriate rationale for prescribing newer, often more expensive treatments.
Recommendations in the AGA statement that address the initial clinical assessment of constipation include the following:
• When feasible, medications that can cause constipation should be discontinued before further testing is initiated. This is a "strong" recommendation based on low-quality evidence.
• A careful digital rectal examination, including assessment of pelvic floor motion during simulated evacuation, is preferable to a cursory examination without these maneuvers and should be performed prior to referral for anorectal manometry. A normal exam, however, does not exclude defecatory disorders. This is a "strong" recommendation based on moderate-quality evidence.
The recommendations also address testing to assess medical causes of constipation. In addition to colonic transit testing, after ruling out a defecatory disorder, other recommended tests to assess for medical causes of constipation include a complete red blood count. Metabolic tests such as glucose, calcium, and sensitive thyroid-stimulating hormone are necessary only when other clinical features warrant these tests, and a colonoscopy and an imaging procedure for colonic lesions is only necessary in the presence of "alarm features," including blood in the stool, anemia, and weight loss, for medically refractory constipation or when age-appropriate colon cancer screening has not been performed. Anorectal manometry and a rectal balloon expulsion are indicated in those who fail to respond to laxatives but defecography only when anorectal manometry and a rectal balloon expulsion are inconclusive for defecatory disorders. All of these are "strong" recommendations based on low- or moderate-quality evidence.
Initial medical management, according to the statement, should include:
• A therapeutic trial of fiber supplementation and/or osmotic or stimulant laxatives after discontinuing medications that can cause constipation and after performing blood and other tests as guided by clinical features, but before anorectal testing.
• Use of long-term laxatives for normal and slow-transit constipation.
• Anorectal testing in patients who do not respond to these measures.
• Pelvic floor retraining by biofeedback therapy rather than laxatives in those with defecatory disorders.
These are all "strong" recommendations based on moderate- or high-quality evidence.
As for treatments to consider in patients who fail to respond to initial approaches, the AGA says that newer agents, such as lubiprostone and linaclotide, should be considered in those with normal or slow transit constipation who fail to respond to simple laxatives. Based on the GRADE ratings, this is a "weak" recommendation (implying that benefits, risks, and the burden of intervention are balanced among several legitimate management options or that appreciable uncertainty exists, and is based on moderate-quality evidence).