Constipation is a common health problem, especially in the Western world, most probably due to dietary habits and lifestyle. It is difficult to define constipation, due to wide range of normal bowel habits, but in general constipation refers to persistent, difficult, infrequent, or seemingly defecation.

The normal stool frequency also has a wide range, e.g. in Western countries most individuals have at least 3 bowel movements per week, but in developing countries an individual may have as many as three bowel movements per day (due to consumption of natural food with high fiber content) as normal bowel habit. If an American or European has 3 bowel movements a day it can be considered as diarrhea and if an Indian (or from other developing country) has 3 bowel movements per week it can be considered as constipation.That is why low stool frequency alone can not be the sole criterion for the diagnosis of constipation and other factors need to be considered before diagnosing constipation.

Many individuals with “constipation” have normal bowel habit but complain of a sense of incomplete defecation, excessive straining, hard stools, or lower abdominal fullness. The diagnosis of “constipation” need to be individualized and an attempt should be made to differentiate “constipation” from difficulty in defecation, before attempting to treat a patient with constipation.

The form and consistency of stool correlate well with the time from preceding defecation and transit time through the gut. If transit time is slow, hard and pellety stools occur whereas loose watery stools occur if transit is rapid. In general very large stools or hard small pellety stools are more difficult to expel than normal stools.

In constipation, psychosocial and cultural factors are important. For example, if a person’s parents consider daily defecation to be important, it will become a great concern when the person misses a daily bowel movement. Some persons habitually delay the call of nature and may suffer from constipation later.

What are the Causes of Constipation?

Constipation can be of recent onset or chronic and the causes of constipation may be different in recent onset constipation from chronic constipation.

Recent onset constipation may be a symptom of significant organic disease such as tumor or stricture. Causes of recent onst constipation are obstruction of colon (due to neoplasm or tumor, stricture, ischemia, diverticula, inflammation in gastrointestinal tract), spasm of anal sphincter (due to anal fissure or painful hemorrhoids) and medications (such as iron, some antibiotics etc.).

Chronic constipation is generally due to inadequate fiber or fluid intake or due to disorder in colonic transit or disorder in anorectal function. All these disorders result due to neurogastroenterologic disturbance, certain drugs, old age, or due to systemic diseases that affect the gastrointestinal tract.

Causes of chronic constipation include IBS (irritable bowel syndrome of constipation predominant type of alternating type), medications (antidepressants, calcium channel blockers etc.), psychiatric problems (such as depression, eating disorders, and drugs), colonic pseudo-obstruction (slow-transit constipation, megacolon such as Hirschsprung's disease, Chagas disease), neurological problems (such as Parkinsonism, multiple sclerosis, spinal cord injury etc.), disorders of rectal evacuation (due to pelvic floor dysfunction, anismus or pain during defecation, rectal mucosal prolapse, rectocele etc.), endocrinopathies (such as hypothyroidism, hypercalcemia,) etc. Pregnancy can also be a cause of chronic constipation.

History and Examination (physical and laboratory) of patient with constipation:

If a patient comes to a physician with complaint of constipation, a careful history should be taken to determine if the patient is truly suffering from constipation, based on frequency (e.g., fewer than three bowel movements per week, in Western countries and may be more in developing countries based on local experience), consistency (i. e. stool is lumpy or hard), excessive straining required for defecation (much prolonged defecation time than normal)or is there any need to support the perineum or need manual evacuation with fingers.

In more than 90% of patients with constipation, there is no underlying cause (such as tumor, psychological problem etc.) of constipation and respond to general measures such as adequate hydration, intake of high fiber diet (at least 15-20 grams of fiber is recommended per day) and exercise. Physical examination should be done to exclude fecal impaction in rectum. Physical examination can also exclude important diseases that has constipation as symptom and indicate an evacuation disorder (e.g., high anal sphincter tone) if present.

If the patient has weight loss, rectal bleeding, or anemia along with constipation, flexible sigmoidoscopy plus barium enema or colonoscopy alone, should be done to exclude anatomical diseases such as tumor (cancer) or strictures, especially in patients above 40 years of age. Colonoscopy is most cost effective as it can be used for biopsy of mucosal lesions, polypectomy, or dilatation of strictures and recommended.

Barium enema has certain advantages over colonoscopy, especially in isolated constipation, as barium enema is less costly and also can identify colonic dilatation and any significant mucosal lesions or strictures that may be present with isolated constipation. Barium enema can also detect unexpected disorder such as megacolon or cathartic colon.

Measurement of serum calcium, potassium, and thyroid-stimulating hormone levels should be done in patients with chronic constipation to identify patients with rare metabolic disorders.

In many patients with long standing and troublesome constipation, general measures such as exercise, high fiber diet etc. may not help and may need a bowel training regimen, osmotic laxative (lactulose, sorbitol, polyethylene glycol etc.) or may need evacuation with enema or glycerine suppository. After breakfast, a distraction-free 15–20 minute on the toilet without straining should be encouraged for these patients, as excessive straining may lead to development of hemorrhoids. If there is weakness of the pelvic floor or injury to the pudendal nerve, excessive straining may also lead to obstructed defecation from descending perineum syndrome several years later.

Those (although fortunately only few of constipation patients) who do not benefit from the above mentioned treatment modalities and require long-term treatment with potent laxatives have the risk of developing laxative abuse syndrome should be assumed to have severe or intractable constipation and need further investigation.

Investigations in severe or intractable constipation:

Less than 5% of patients with constipation have severe or intractable constipation and are most likely to be seen by gastroenterologists in referral centers. In these patients with severe or intractable constipation, physiologic function of the colon and pelvic floor and of psychological status can help in rational treatment, although in only about two third of these patients, a cause can be found despite extensive investigation. The severe or intractable constipation patients require measurement of colorectal transit time and anorectal and pelvic floor tests.

Measurement of colorectal transit time:

Measurement of colorectal transit time can be easily done by radiopaque markers which are generally safe, inexpensive, reliable, can be repeated and highly useful in for evaluation of constipated patients in clinical practice. There are several methods such as abdominal flat film taken 5 days after ingestion of radiopaque marker, without the use of laxatives or enemas. This method can not show transit profile of the stomach and small intestine.

Radioscintigraphy can overcome the problems of the above procedure. A delayed-release radiolabeled particle containing capsule is used in radioscintigraphy for differentiating normal, delayed or accelerated colonic function over 24 48 hours. This has low radiation exposure. But the disadvantage is high cost and need to prepared radiolabeled particle containing capsule in a nuclear medicine laboratory.

Anorectal and pelvic floor tests:

Inability to evacuate the rectum fully and a feeling of persistent rectal fullness, the need to extract stool from the rectum digitally, pain in rectum, use of pressure on the posterior vagina wall during defecation, need of support of the perineum during straining, and excessive straining are all suggestive of pelvic floor dysfunction. The symptoms of pelvic floor dysfunction should be differentiated from sense of incomplete defecation in IBS (irritable bowel syndrome).

A simple test to identify the proper functioning of the pelvic floor muscles is to ask the patient to strain to expel the index finger during a digital rectal examination. Movement of puborectalis muscle posteriorly during straining is indicative of normal pelvic floor muscles.

Balloon expulsion test for evacuation is a useful clinical test. In balloon expulsion test, a balloon tipped urinary catheter is placed inside rectum and inflated with 50 ml of water. If patient can expel the balloon while seated on a toilet or in the left lateral decubitus position is indicative of normal pelvic floor muscles. If the weight needed to expulpel the balloon is less than 200 gram, it indicate normal pelvic floor muscles.

Other anorectal and pelvic floor tests include defecography, anorectal manometry, proctography during defecation, scintigraphic expulsion of artificial stool, electromyography etc.

Defecography:

Defecography is a dynamic barium enema which includes lateral views during barium expulsion. Defecography can reveal abnormalities in many patients, such as changes in rectoanal angle, anatomic defects of the rectum (internal mucosal prolapse, and enteroceles or rectoceles) etc. although only a few cases are amenable to surgery, such as whole-thickness intussusception that obstructs outlet completely due to funnel-shaped plugging at anal canal and a huge rectocele that fills preferentially while attempting to defecate instead of expulsion of the barium through the anus. Abnormalities that are found in defecography are not pathognomonic for pelvic floor dysfunction.

Anorectal manometry:

Anorectal manometry is done to evaluate patients with severe constipation, where high resting (more than 80 mmHg) anal sphincter tone is suggestive of anismus (anal sphincter spasm). Anorectal manometry can also identify (by absence of the rectoanal inhibitory reflex) rare syndromes, such as Hirschsprung's disease in adults.

Proctography and scintigraphy:

Proctography and scintigraphy are done to confirm pelvic floor dysfunction. In proctography if rectoanal angle does not straighten by at least 15° during defecation is confirmatory to pelvic floor dysfunction. Scintigraphy is done by testing expulsion of artificial stool of a particular quantity and the amount of “artificial stool” emptied indicates if there is any pelvic floor dysfunction.

The most common cause of outlet obstruction is failure of the puborectalis muscle to relax during defecation, which can be identified by proctography.

Electromyography:

Electromyography is more useful in evaluation of patients with incontinence than of those with obstructed defecation. Electromyography can help in evaluating constipation due to spinal cord injuries, obstetric injury, and neurologic diseases such as Parkinson's disease, multiple sclerosis, and diabetic neuropathy. Injury or from stretching of the pudendal nerve by chronic, long-standing straining can be demonstrated by electromyography.

MRI in constipation:

MRI is comparatively new in diagnosis of constipation and it is an alternative to other methods to determine abnormalities, and provides more information about the structure and function of the pelvic floor, distal colorectum, and anal sphincters than other methods of investigation.

Treatment of constipation:

Ideally appropriate treatment can be done after defining the cause of constipation. But only approximately 60% of patients with severe constipation are found to have a physiologic disorder, and out of these, half have colonic transit delay and half have evacuation problem. If a cause is found in constipation, the cause should be treated. Constipation due to slow transit in GIT needs vigourous (medical or surgical) treatment. Constipation due to anismus or pelvic floor dysfunction can be treated with biofeedback management appropriately.

Slow-transit constipation patients are treated with bulk laxative, osmotic laxative, secretory, and stimulant laxatives (such as fiber, psyllium, milk of magnesia, lactulose etc.), polyethylene glycol (colonic lavage solution), lubiprostone, prokinetic drugs and bisacodyl. Patients with constipation-predominant IBS or severe constipation cen get benefited with motility and secretion enhancing treatment.

Surgery is indicated if a 3-6 month trial of medical therapy fails and patients continue to have documented slow-transit constipation which is not due to obstructed defecation. These patients can be candidate for laparoscopic colectomy (resection of a part of colon) with ileorectostomy (anastomosis of ileum and rectum), although, surgery should not be done if there is evidence of an evacuation disorder or there is a generalized GI motility disorder. Surgery is required in there is megacolon and/or megarectum. The complications of surgery are small-bowel obstruction (occurs in approximately 11% patients undergoing surgery) and fecal soiling, especially at night during the first postoperative year. Frequency of defecation is 3–8 per day during the first postoperative year, which comes down to 1–3 per day from the second postoperative year.

If a patient has constipation due to evacuation problem and transit/motility problem, he/she should be treated with pelvic floor retraining (biofeedback and muscle relaxation), dietetic advice and psychological counseling first. Surgery (colectomy and ileorectosomy) should be considered if colon transit time is still slow and symptoms still persists despite biofeedback and aggressive medical therapy.

In case of constipation due only to pelvic floor dysfunction, biofeedback training can be successful in 70–80%cases. The success of biofeedback training is measured by development of comfortable stool habits. Management of constipation due to pelvic floor dysfunction with surgery does not give satisfactory results and now mostly abandoned.