Constipation

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What is constipation?

  • Infrequent and difficult defection.

    • Formally, constipation gets defined as three or fewer bowel movements per week.

  • In North America, chronic constipation is quite prevalent: estimated around 15%.

  • Chronic constipation is more prevalent in females, and in those over age 65.

    • However, pregnancy is another common time period for constipation to occur.

  • Before we get too deep into a discussion on stool, know we’ll be making mention today of the Bristol stool chart. 

    • Many of the diagnoses and considerations surrounding constipation, diarrhea, and IBS use this scale. It’s worth reviewing – probably the last time you looked was medical school! We’ll have one on the website.

WIKIPEDIA

Here are actual criteria to make a diagnosis of functional constipation known as the Rome IV criteria:

  • Functional constipation must be three months with:

    • 1) Loose stools rarely present without the use of laxatives

    • 2) Insufficient criteria to diagnose irritable bowel syndrome (IBS)

    • 3) Two or more of the following symptoms:

      • Straining during more than 25% of defecations

      • Lumpy or hard stools (Bristol scale 1 or 2) in more than 25% of defecations

      • Sensation of incomplete evacuation for more than 25% of defecations.

      • Sensation of anorectal obstruction/blockage for more than 25% of defecations.

      • Manual maneuvers to facilitate more than 25% of defecations (i.e., splinting or digital evacuation)

      • Fewer than three spontaneous bowel movements per week.

  • In terms of causes, there are three broad categories:

    • Normal transit constipation, which includes functional chronic constipation and IBS. 

    • Slow transit constipation, which can be due to a variety of factors like: 

      • medications that slow colonic transit (i.e., opioids) or 

      • medical disorders or conditions such as different systemic or neuromuscular diseases (i.e., severe diabetes, anorexia nervosa, pregnancy) or diseases of the colon (i.e., colorectal cancer, Hirschsprung’s disease)

    • Pelvic floor disorders, such as pelvic floor dysfunction after injury or trauma, or pelvic organ prolapse.

  • Constipation is usually not a life-threatening issue.

    • It is a major quality of life issue though!

    • Severe constipation can lead to colonic dilatation and perforation.

How to approach the patient with constipation

  • Start with history:

    • Get a sense of the problem, and whether there might be any major red flags:

      • Evaluate medications that may slow colonic transit.

        • Common meds that slow transit include:

          • Opioids, 

          • Antihistamines, 

          • Certain antidepressants and antipsychotics, 

          • Iron supplements,

          • Aluminum-based antacids, 

          • Serotonin antagonists (i.e., ondansetron/Zofran), 

          • and some antihypertensives like calcium channel blockers (i.e., nifedipine).

      • Ask about major red flags for colon cancer:

        • Presence of hematochezia, or positive fecal occult blood tests

        • Weight loss of > 10 lbs

        • Family history of colon cancer or inflammatory bowel disease

        • Acute onset of constipation particularly in older adults

      • Consider other medical conditions that may contribute to constipation, depending on the patient’s age and medical status:

        • Diabetes mellitus or other neuropathic disorders

        • Multiple sclerosis, Parkinson disease

        • Spinal cord injuries

        • Hypothyroidism

        • Pregnancy

        • Panhypopituitarism (i.e., Sheehan syndrome after postpartum hemorrhage)

        • Irritable bowel syndrome

          • IBS specifically encompasses abdominal pain that is recurrent, and can be associated with changes in stool (diarrhea or constipation).

          • The Rome IV criteria for IBS are having > 1 day per week of recurrent abdominal pain for at least three months, along with two or more of the following:

            • The pain is related to defecation (either increasing or relieving pain)

            • The pain is associated with a change in stool frequency

            • The pain is associated with a change in stool form (appearance on Bristol scale)

  • Consider a physical exam:

    • In most patients, a general physical exam is not super helpful.

    • A pelvic and rectal exam may be quite useful in those with chronic constipation:

      • Can identify evidence of chronic constipation, such as skin tags, fissures, hemorrhoids, or a fistula near the anus.

      • Can evaluate for prolapse and pelvic floor dysfunction.

        • Inspecting the anus, can ask the patient to squeeze like they’re holding a bowel movement to look for contraction of the sphincter and gluteal muscles.

        • Check for anal wink reflex to make sure sacral nerves intact.

        • Digital rectal exam to assess rectal tone, tenderness, and relaxation when finger is expelled.

  • In most patients with new complaints of constipation and no red flag symptoms, a trial of laxatives is appropriate before other major diagnostic workup.

    • Talk more about laxatives and treatments later!

  • If your patient needs some additional testing, others to consider (though probably with our GI colleagues!)

    • Anorectal manometry: a probe with sensors in the rectum to measure rectal and anal pressure, and the gradient with evacuation and squeeze. Similar in principle to urodynamics in urogynecology.

      • Can be accompanied with various tests such as a balloon expulsion test or balloon rectal sensitivity test, which can provide additional information.

    • Defecography: a radiocontrast study to evaluate what occurs during evacuation of rectal content to look for signs of prolapse or obstruction.

    • Sitz marker study or Nuclear medicine scintigraphy: radioopaque markers or tracers are swallowed and radiographs taken at certain intervals to evaluate transit within the bowel and colon.

Treating Constipation

  • There are loads of treatment options for constipation, so we’ll break them down mechanistically.

  • Fiber

    • First line treatment, and soluble fibers are recommended (beans, psyllium, oat bran, barley)

      • Soluble fibers attract water and turn to a gel-substance during digestion.

      • Insoluble fibers (wheat bran, vegetables, whole grain) add bulk to stool and help food pass more quickly.

        • Soluble fibers are generally preferred for constipation and are what are sold as supplements (i.e., psyllium is Metamucil and Benefiber). 

        • Soluble fibers can increase gas production though, and so in those with IBS and slow-transit constipation, it can be difficult to encourage compliance.

          • This can be modulated by starting with small amounts and slowly titrating upwards.

    • Recommended daily intake is >25g/day for women, and >35g/day for men.

  • Osmotic laxatives

    • These laxatives act as hyperosmolar solutions that are not systemically absorbed, and thus add water into the stool in order to increase stool frequency.

      • Examples: polyethylene glycol (GoLytely, MiraLax); lactulose; sorbitol; milk of magnesia, magnesium citrate.

    • They are highly effective and titratable to effect.

    • Excess use in patients with renal and cardiac dysfunction can lead to electrolyte abnormalities.

  • Stimulant laxatives

    • These alter electrolyte transport mechanisms in the intestinal mucosa, thus increasing their motor activity.

      • Examples: bisacodyl (Dulcolax), senna, sodium picosulfate

    • They are generally well-tolerated, but can produce abdominal discomfort in some patients due to the “irritation” effect on the intestines.

      • Some of these can be associated with developing hypokalemia, salt depletion, and significant enteric protein-wasting, so are not encouraged to be used chronically.

    • Some folks can develop tolerance to these medications, so are also not encouraged to be used chronically so that tolerance does not develop.

  • Biofeedback and Pelvic Floor Treatment

    • Pelvic floor PT, biofeedback training, and pelvic floor therapies with colorectal surgeons or urogynecologists can also be effective, especially if patients have symptoms of rectocele.

    • Other positioning tools for pelvic floor dysfunction include things like the “squatty potty” to encourage puborectalis muscle / sphincter relaxation.

  • Suppositories, Enemas, and Disimpaction

    • Bisacodyl suppositories are easy to use and can be considered first.

      • They can effectively liquefy stool and clear impaction in the rectum.

    • Various enemas exist: tap water, mineral oil, soap suds, phosphate, milk & molasses)

      • It is most important to focus on side effects - i.e., fleets enemas (phosphate) can lead to hyperphosphatemia, particularly in patients with kidney disease.

    • Manual disimpaction

      • Never fun, and not a lot of guidance on the best method – break stool up with your well-lubricated finger, and extract it, until the hardened stool is cleared.

      • Best followed up with a mineral oil enema or milk and molasses enema – will soften stool and provide lubrication.

        • If disimpaction is not successful, water-soluble contrast enema should be considered with fluoroscopy to evaluate for obstruction and rarely GI may need to be consulted for flexible or rigid sigmoidoscopy to evacuate stool.

  • What about docusate (Colace)?

    • Not the best evidence… likely no impact.

    • Journal of Hospital Medicine 2019: Things We Do For No Reason: Prescribing Colace for Constipation in Hospitalized Adults

      • Potentially over $100 million spent on colace annually across North America in hospitalized populations.

      • Multiple negative studies in randomized trials show that it does not improve or prevent constipation.

      • Recommend de-implementing it from order sets and hospital formularies.