To Poop or Not to Poop!

April 30, 2009

Constipation is a very prevalent problem, affecting up to 20% of the US population.

Clinical Scenario: Ms. C is an 8-year-old female with a history of hypothyroidism, hypertension, dementia, depression, chronic constipation, and diverticulosis is admitted with abdominal discomfort and distention. She was originally brought to the ED by family for altered mental status. On further history, she has not had a bowel movement for 8 days and is passing minimal gas. There is no associated nausea or vomiting. Portable Abdominal X-ray shows a colon full of stool without obstruction. On exam, the rectal vault is full of hard feces. Her medications include Synthroid, Verapamil, Elavil, psyllium, and docusate.

Constipation is a very prevalent problem, affecting up to 20% of the US population. Chronic constipation as defined by the Rome III Criteria requires a patient to have 2 or more of the following in the last 3 months: straining with 25% of defecations, hard or lumpy stools with 25% of defecations, sensation of incomplete evacuation with 25% of defecations, sense of anorectal obstruction with 25% of defecations, need for manual maneuvers to facilitate with 25% of defecations, having less than 3 bowel movements per week, lack of loose stools unless with use of laxatives, do not meet the criteria for irritable bowel syndrome (main distinction being predominance of pain). Based solely on the widespread prevalence of constipation, it comes as no surprise that national data estimates constipation related costs to approximate $250 million a year! This does not include the indirect costs arising from absenteeism from work and impairment during work due to constipation. Most importantly, chronic constipation can have a significant negative impact on quality of life.

While most of us have a good general idea of what constipation is and the pharmaceutical and non-pharmaceutical options for management, it never hurts to review the topic again. Most of what I am going to present here is from reviewing several articles but with focus on a review paper from JMCP, “Optimal treatment of Chronic Constipation in Managed Care: Review and Roundtable Discussion,” which can be found at www.amcp.org. (JMCP, volume 14, No 9, S-a, Nov 2008)

There are two main categories of constipation, primary and secondary. Primary refers to idiopathic or functional constipation, which is further divided into normal-transit constipation (most common), slow-transit constipation, and pelvic floor dysfunction (likely most overlooked). Secondary constipation refers to constipation resulting from a medical condition (hypothyroidism, hypercalcemia, neuropathy, anxiety, colonic strictures, inactivity, etc) or medications (analgesics, anticholinergics, calcium channel blockers, etc). Our patient above has many of these predisposing factors that are likely contributing to her constipation. As the name implies, slow-transit constipation is mainly caused by impaired colonic contractile activity which leads to infrequent bowel movements, urgency, straining, etc. In contrast, normal-transit constipation has normal stool passage, but these patients still perceive difficulty in passing stools. These two types can easily be distinguished by simple radiography using radio-opaque markers and performing follow up x-rays. It is important to note that while there is an overlap between chronic constipation and irritable bowel syndrome with constipation one can distinguish the two by the predominance of abdominal pain with IBS. The pelvic dysfunction variety of constipation can result from problems of the pelvic floor or the anal sphincter. There are methods for diagnosing pelvic dysfunction, including balloon expulsion, dynamic pelvic MRI, anorectal manometry, and defecography.

Why is it important to diagnose and manage constipation? Other than just making patients feel bad, it can have many adverse consequences such as hemorrhoids, fecal impaction leading to obstruction, volvulus, rectal prolapse, anal fissures, fecal incontinence, overflow diarrhea, pressure related ulcers and bowel perforation, etc.

So you have determined that your patient is indeed a sufferer of chronic constipation, and you have ruled out possible secondary (organic or medication related) causes of constipation. Needless to say, the first step in management should be educating your patient about life style modifications including increasing water and fiber intake, scheduled bowel movements, and regular exercise. In some cases, it might be indicated to perform some of the preliminary testing as above to categorize the primary underlying problem (transit vs. pelvic floor dysfunction) as it may impact the management. For example, patients with pelvic floor dysfunction do best with anorectal biofeedback.

Without getting too detailed, I wanted to review some of the readily available pharmacological treatments for constipation. Many of the medications are now available over the counter (OTC) and thus easy to access. The big categories include bulking laxatives, osmotic laxatives, stimulant laxatives, stool softeners, and emollients. In my review, it appeared that not many studies have been done comparing these agents face to face and thus there are is not a clearly defined, evidence-based algorithm by the ACG (American College of Gastroenterology) Task Force on the most effective management strategy for chronic constipation. Of the medications I will discuss, only the osmotic laxatives, polyethylene glycol and lactulose, meet Grade A ACG recommendations. Furthermore, newer agents have since been approved by FDA, and are not included.

Bulk laxatives are fiber supplements (eg, psyllium and methylcellulose) that soften stool and increase bulk to facilitate defecation. These are the most commonly used OTC agents and can take 2-3days to work. Stool softeners, such as docusate, will coat the stool surface like detergent to allow easier passage. However, note, solely using these agents without concomitant laxatives, especially in patients who have impaired colonic activity such as slow-transit constipation or pelvic floor dysfunction, is useless. Mineral oil is an emollient product that also lubricates and softens the stool and promotes bowel movements. Then, there are stimulant and osmotic laxatives. Stimulant laxatives such as senna and biscodyl, enhance intestinal smooth muscle contractions as well as decrease water resorption, generally resulting in a bowel movements within 6-12hours. Finally, osmotic laxatives include milk of magnesium, magnesium citrate, polyethylene glycol (PEG/miralax), sorbitol, and lactulose. Lactulose is the only agent thus far that requires a prescription. And, as mentioned above, PEG and lactulose are the only ones that have actually been studied and thus have Grade A recommendations by ACG for their use in chronic constipation management. These agents use osmotic forces to draw water into the colon, which in turn facilitates defecation. As for the newer agents approved by the FDA in 2008, these include lubiprostone (chloride channel activator that enhances intestinal fluid secretion), and two agents specifically for opiod-induced constipation (secondary), methylnaltrexone, and alvimopan (work on peripheral opiod receptors thus does not affect central analgesic effects). Since these agents are still relatively new, they are expensive and do not yet have a clear long-term safety profile, which render them second line options.

For the most part, most agents for managing chronic constipation are widely available as OTC. Thus, routine physician to patient education on their proper use may go a long way in management of this not so comfortable scenario (literally). Furthermore, unlike many medications, these agents are for the most part well tolerated and have a decent safety profile. The most common side effects across all groups include bloating, flatulence, nausea, abdominal pain/cramping, and diarrhea. The most common adverse effects appear to be related to malabsorption of other medications and electrolyte disturbances due to its effects on the colon. Obviously caution should be taken with the very young, very old, patients with renal failure, multiple comorbidities, etc. Long term uses of some agents, such as emollients, not only lead to malabsorption of certain medications, but also of fat-soluble vitamins (ADEK). Furthermore, its use in the very old and very young who are predisposed to aspiration can lead to lipoid pneumonia. Long term use of stimulant laxatives, such as senna, can pigment the colonic mucosa (melanosis coli), but this is reversible and has no correlation to colon cancer.

In the clinical scenario, Ms. C. likely had delirium secondary to constipation complicated by fecal impaction, which is a common scenario in the elderly. After manual fecal disimpaction, it would be important to review life-style modification with the patient/family, check TSH, and search for alternatives to verapamil (calcium channel blocker) and Elavil (tri-cyclic anti-depressant). If this does not result in regular bowel movements, you may consider adding an as needed agent such as an osmotic or stimulant laxative.