Chronic Constipation – The Causes, Symptoms, and Treatment

By Dr. Namhyun Kim
General Surgery
European Society of Hemato-Centric Medicine
Düsseldorf, Germany

Constipation is the most common digestive complaint in the United States according to survey data [19]. Chronic constipation is a common condition that affects up to 27% of the population [1] and is twice as common in women than in men [2]. More than four million Americans have frequent constipation, accounting for 2.5 million physician visits a year. Constipation-related healthcare costs total $6.9 billion in the U.S. each year [20], with another $725 million spent on laxative products [21].

Causes:

Constipation is a symptom with many causes. The two primary causes are obstructed defecation (organic) and colonic slow transit (functional). The distinction between organic and functional types of chronic constipation has no practical relevance in the treatment of patients.

• Primary: Primary or functional constipation are on-going symptoms that last more than six months that do not have any underlying cause such as medication side effects or a medical condition.
• Diet: Constipation can be caused or exacerbated by a low-fiber diet, low liquid intake, or dieting.
• Medication: Constipation is a side effect of several types of medication.
• Metabolic and muscular: Metabolic and endocrine problems which may lead to constipation include hypercalcemia, hypothyroidism, diabetes mellitus, cystic fibrosis and celiac disease. Constipation is also common in individuals with muscular and myotonic dystrophy.

• Structural and functional abnormalities:

  – Structural causes: spinal cord lesions, Parkinson, colon cancer, anal fissures, proctitis and pelvic floor dysfunction.
  – Functional (neurological) causes: anismus, descending perineum syndrome and Hirschsprung’s disease.

Symptoms:

The term “constipation” refers to a constellation of symptoms. The “Rome III criteria” are a useful set of diagnostic criteria for constipation. At least two of the following symptoms are required to have been present for at least three of the past six months:

• Straining at stool at least 25% of the time
• Hard stools at least 25% of the time
• A feeling of incomplete evacuation at least 25% of the time
• A feeling of anal blockage at least 25% of the time
• Manual maneuvers for rectal emptying at least 25% of the time
• Two stools or less per week

Diagnostic evaluation

It is important to be diligent in examining the patient’s history, as many patients often do not report certain symptoms spontaneously. Apart from history-taking, diagnostic testing can be kept to a bare minimum for the vast majority of patients.

A digital rectal examination is part of the basic physical work-up, particularly when the symptoms point to a possible functional disturbance of the rectum. Large amounts of stool in the colon usually can be visualized by a simple X-ray examination of the abdomen; the more stool that is visualized, the more severe the constipation.

Colonoscopy is indicated only if an organic disease of the colon is suspected, or if the procedure is scheduled to be performed as part of cancer screening. It is not an essential element of the diagnostic evaluation of chronic constipation. Laboratory studies, too, are superfluous in most cases.

The next step is high-dose trial therapy with bacterially non-degradable dietary fiber, for a period of about two weeks. The most suitable substances for this purpose are wheat bran and psyllium preparations. Bran is less expensive, but also less well tolerated [3]. If a trial of non-degradable fiber results in adequate improvement of the symptoms, then no further diagnostic assessment is needed [4].

Measurement of the transit time mainly serves to objectify the patient’s symptoms, as subjective reports of low stool frequency are often not very accurate. If the transit time is normal, for example, then this will effectively disprove a patient’s claim of having had “practically no bowel movements at all for a week”.

Colonic transit studies are simple X-ray studies that determine how long it takes for food to travel through the intestines. For transit studies, individuals swallow capsules for one or more days. Inside the capsules are many small pieces of plastic that can be seen on X-rays. The gelatin capsules dissolve and release the plastic pieces into the small intestine. The pieces of plastic then travel (as would digesting food) through the small intestine and into the colon. After 5 or 7 days, an X-ray of the abdomen is taken and the pieces of plastic in the different parts of the colon are counted. From this count, it is possible to determine if and where there is a delay in the colon. In non-constipated individuals, all of the plastic pieces are eliminated in the stool and none remain in the colon. When pieces are spread throughout the colon, it suggests that the muscles or nerves throughout the colon are not working, which is typical of colonic inertia. When pieces accumulate in the rectum, it suggests pelvic floor dysfunction.

Treatment

Basic Treatment

Chronic constipation often impairs the patient’s quality of life [5]. Patient education is important. Dietary fiber is worth trying, but it is not a magic bullet and some patients cannot tolerate it. If trial therapy with dietary fiber is successful and well tolerated, it is reasonable to recommend a high-fiber diet with whole wheat products. Fruit and vegetables are relatively ineffective, because most of the dietary fiber they contain is degraded by bacteria [6].

Laxatives

1. Water-binding laxatives

Some osmotic salts, such as Carlsbad salt, are found in natural sources and have been used to treat constipation for years. However, long-term use can be problematic due to their disagreeable taste.

In recent years, polyethylene glycol (macrogol), which has long been used to cleanse the bowel in preparation for diagnostic and therapeutic procedures, has been found to be effective for the long-term treatment of constipation [7].

The sugar alcohol sorbite and the disaccharide lactulose are also often used to treat constipation. They produce a considerable degree of bloating, however, and are not very effective if the colonic transit time is prolonged [7, 8].

2. Stimulating laxatives

The generic term “stimulating laxatives” includes the anthraquinones as well as the diphenylmethanes bisacodyl and sodium picosulfate. These agents have a dual mechanism of action. They inhibit fluid resorption from the small and large intestines and induce fluid secretion in dose-dependent fashion; they also have a marked prokinetic effect. The latter may cause cramp-like abdominal pain. These medications take effect 6 to 12 hours after they are consumed, causing one to three bowel movements [9].

Anthraquinones are naturally present in the form of glycosides. These compounds cannot be resorbed from the small intestine and thus have no effect on it. The pharmacologically active rhein canthrones arise only in the colon as the result of bacterial degradation of the drug.

The synthetic laxative bisacodyl is converted into the active substance BHPM (bis-[p-hydroxyphenyl]-pyridyl-2-methane) by hydrolases of the colonic mucosa. Because an effect on the small intestine is not wanted, this medication is given only in tablet form, and not in liquid form. An elegant alternative is to administer the sulphate ester of bisacodyl, i.e., sodium picosulfate [9]. This substance is enzymatically activated by hydrolases only after it is degraded by bacteria in the colon. It can thus be given in drop form and can be more finely dosed.

Prokinetic

Because chronic constipation is usually a hypomotile disorder, it would seem logical to attempt to treat it with purely prokinetic agents. In accordance with our current state of knowledge, the main purely prokinetic agents coming into consideration are 5-hydroxytryptamine4 (5-HT4) agonists. In this class of medications, cisapride, prucalopride, and tegaserod have been well studied in randomized, controlled trials and have been found to be moderately effective against chronic constipation [1].

In recent years, the nonselective serotonin 5-HT4 receptor agonist tegaserod and the chloride-channel activator lubiprostone have been used in the United States to treat chronic constipation [10, 11].

Prucalopride, a dihydrobenzofurancarboxamide derivative, is a selective, high-affinity 5-HT4 receptor agonist, which accounts for its enterokinetic effects [12, 13]. Prucalopride increases colonic motility and transit [14-18].

The mechanism whereby Prucalopride relieves constipation is interesting and is related to its effects on the intestinal serotonin, a chemical that controls contractions of intestinal muscles. The contractions of the intestinal muscles control transit of digesting food through the intestine. More contractions speed transit while fewer contractions slow transit. In constipated patients, contractions are fewer.

Serotonin is a chemical manufactured in the intestine that is released and then binds to muscle cells. Depending on which receptor it binds to on the muscle, serotonin can either promote or prevent contractions. Prucalopride alters colonic motility patterns via serotonin 5-HT4 receptor stimulation: it stimulates colonic mass movements, which provide the main propulsive force for defecation. The increased contraction speed the transit of digesting food and reduces constipation.

Enemas

Enemas (transanal irrigation) can be used to provide a form of mechanical stimulation. There are many different types of enemas. By distending the rectum, all enemas stimulate the colon to contract and eliminate stool.

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