Move smoothly through constipation evaluation and management. Learn how to evaluate for the various etiologies of constipation including pelvic floor dysfunction, IBS-C and more with our esteemed guest Dr. Xiao Jing (Iris) Wang @IrisWangMD!
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To produce a bowel movement:
Constipation includes symptoms of decreased stool frequency, incomplete evacuation, changes in stool consistency, and difficulty with defecation. Constipation is formally diagnosed as 3 or fewer bowel movements per week and chronic constipation occurs when symptoms persist for 3 consecutive months.
“Bowel Habit Review of Systems”
1. Start with baseline: Frequency of stools—what was your baseline what was normal for you and what is it now?
2. Bristol stool form: On a 1-7 scale visual idea of softness of bowel movement, 1 to 2 is a hard bowel movement by definition though changes may be relative to baseline
3. Ask about warning signs including weight loss, change in stool caliber (especially sudden onset change), severe pain & rectal bleeding.
4. Do you strain when you have a bowel movement?
5. Sensation of incomplete evacuation or feeling like you just had a bowel movement and there is still more stool present?
6. Do you need to shift positions on the toilet? Are you doing “toilet yoga”?
7. Do you ever use a finger to help the stool come out (manual evacuation)?
8. For females: Do you need to splint the back wall of the vagina? If so, concern for pelvic organ prolapse or rectocele.
**From #4 on, these questions are used to evaluate rectal evacuation disorders
Full head to toe physical exam to evaluate for evidence of upper neuron disorders or systemic disease. Listen to bowel sounds to know if hypoactive or hyperactive. Palpate LLQ because sometimes you can actually feel the stool.
A thorough rectal exam has a sensitivity of 93% and a PPV of 91% compared to your anal rectal manometry and balloon expulsion studies (Bharucha 2020). Dr. Wang recommends describing the rectal exam in detail with patients prior to completing.
There are three categories of constipation: 1) Normal transit constipation (IBS-C & functional constipation), 2) Slow transit constipation (diminished gastrocolic reflex & neuronal or muscular tissue disorders), 3) Defecatory disorders (pelvic floor dysfunction, prolapse).
The evaluation of chronic constipation (usually outpatient) should be completed by first evaluating for secondary causes of constipation. If there is no secondary etiology, a trial of laxatives is recommended (Bharucha 2020).
If the treatment trial is not successful then evaluate for the underlying constipation phenotype with the following (Bharucha 2020):
Additional Testing (Lembo 2003)
**Important to look for pelvic floor dysfunction first because it can slow down bowel transit by causing rectal distention that signals slowing of small bowel and colon transit
Fiber is first-line treatment and Dr. Wang recommends soluble fiber (beans, psyllium, oat bran, barley). Recommended total fiber intake is >25g for women and >35g for men per day, uptitrated over one week to improve tolerance. Dr. Wang recommends aiming for dietary fiber intake with foods such as two kiwi fruits a day or 4 prunes a day (Chey 2021). Although this is first line treatment, evidence has not supported improvement with fiber compared to placebo. If fiber is not tolerable, it is okay to stop it.
Osmotic laxatives are also a backbone treatment. Dr. Wang recommends polyethylene glycol (easily titratable) or milk of magnesia. Lactulose should be avoided particularly in patients with suspected ileus or obstruction as this can generate increased gas when metabolized and potentially induce megacolon.
Stimulant laxatives include senna and bisacodyl. Dr. Wang counsels to take it just when patients are actively constipated and then to stop once they are regular to minimize tolerance. Oral tabs can be taken at night (so peak onset can be timed closer to morning) versus rectal bisacodyl can be in the morning given fast onset.
Secretagogues include linaclotide, plecanatide, & lubiprostone that work by activating chloride receptors in the bowel (think of medicated cholera). Lubiprostone is FDA approved for opioid induced constipation, chronic constipation, and women with IBS-C. Linaclotide & plecanatide are approved for chronic constipation and IBS-C and contraindicated in children. In Dr. Wang’s experience, linaclotide can lead to ‘explosive’ diarrhea, so consider using the lowest of three doses if this occurs. These new medications are useful, but in a network meta-analysis including bisacodyl, bisacodyl performed better than these secretagogues at 4 weeks (Nelson 2017).
Promotility agents: Prucalopride is a prescription laxative that works by increasing bowel contraction. Consider using this agent in cases of slow-transit constipation instead of a secretagogue or if there is no response to secretagogues.
Suppositories/Enemas- Try a bisacodyl suppository first for ease of use. Various enemas (tap water, mineral oil, soap suds, & phosphate) were similarly effective when studied in pediatric patients (Anderson 2019). Therefore, it is important to focus on the potential side effects. For example phosphate or Fleets enemas can lead to hyperphosphatemia, particularly in patients with CKD. Milk and molasses enemas are highly effective and can be considered inpatient.
Pelvic Floor Dysfunction- Biofeedback with trained therapists is recommended and effective (Wald 2016). Positioning with flexion of the hips using something like a “squatty potty” can be recommended to aid with defecation.
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Listeners will develop an approach to the basic evaluation and initial management of constipation.
After listening to this episode listeners will…
Dr Wang reports no relevant financial disclosures. The Curbsiders report no relevant financial disclosures.
Gibson EG, Wang I,Williams PN, Watto MF. “#314 When the Flow Won’t Go: Constipation Evaluation & Management with Dr. Iris Wang”. The Curbsiders Internal Medicine Podcast. http://thecurbsiders.com/episode-list January 3, 2022.
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