Constipation overview

# Overview
Constipation is defined as straining, hard stool, sensation of incomplete evacuation, sensation of obstruction, necessity of manual maneuvers, less than 3 bowel movements per week, lack of loose stool, and lack of irritable bowel syndrome (IBS). Constipation is classified according to etiology into seven subtypes including gastrointestinal, neurologic, metabolic, endocrine, psychiatric, drug-induced, and idiopathic The defecation process consist of three important stages, include filling of the rectum, sensation of rectum fullness, and relaxation of pelvic floor muscles in a coordinated fashion. Primary constipation is caused by anorectal and colonic problems, while secondary constipation is caused by organic and metabolic diseases or medications. Diseases that disturb the nervous system may lead to constipation, such as diabetes mellitus, autonomic neuropathy, Chagas' disease, and Hirschsprung's disease. Chronic use of the laxative may lead to melanosis coli, which is identified by hyperpigmentation and brownish discoloration of colonic mucosa. The primary histopathological finding in melanosis coli is brown granular pigment in lamina propria. Diagnostic study of choice for constipation is ROME III criteria. Rome III criteria includes symptom onset for more than 6 months and two or more number of specific symptoms. Specific constipation symptoms include straining, hard stool, sensation of incomplete evacuation, sensation of obstruction, necessity of manual maneuvers, less than 3 bowel movements per week, lack of loose stool, and lack of irritable bowel syndrome (IBS). Chronic constipation treatment includes both behavioral and pharmacological interventions. Behavioral management mostly consists of life style and dietary modification, while pharmacological interventions are mostly based on laxatives. Increasing physical activity is postulated to improve constipation and colonic transit time in patients with constipation. The most important behavioral treatment for constipation is biofeedback, consisting of teaching the patients how to use their abdominal and pelvic muscles during defecation. Probiotics are live microorganism spores that are given orally to improve the gastrointestinal tract function. Recently, using probiotics in food industry is growing. Bifidobacterium and Lactobacillus are most evaluated organisms as probiotics.

# Historical Perspective
The Egyptian Ebers papyrus, from 16th century BC is the first book that presented a basic description for constipation. Ebers papyrus defined constipation as intoxication of body with hazardous agents from feces in bowels. In early 1900s, all-bran products were first introduced to prevent and treat auto-intoxicated patients due to constipation. In 1970s and 1980s, Denis Burkitt, an English surgeon, claimed the hypothesis about dietary fibers followed by the definition of "The Commonest Western disease".

# Classification
Constipation is classified according to etiology into seven subtypes include gastrointestinal, neurologic, metabolic, endocrine, psychiatric, drug-induced, and idiopathic.

# Pathophysiology
About 1.5 liter fluid enters the colon from small intestine every day. Colon only excrete out  200-400 mL stool. The defecation process consist of three important stages, include filling of the rectum, sensation of rectum fullness, and relaxation of pelvic floor muscles in a coordinated fashion. Primary constipation is caused by anorectal and colonic problems, while secondary constipation is caused by organic and metabolic diseases or medications. Diseases that disturb the nervous system may lead to constipation, such as diabetes mellitus, autonomic neuropathy, Chagas' disease, and Hirschsprung's disease. Chronic use of the laxative may lead to melanosis coli, which is identified by hyperpigmentation and brownish discoloration of colonic mucosa. The primary histopathological finding in melanosis coli is brown granular pigment in lamina propria.

# Causes
Constipation in adults may be due to side effects of medications, such as antispasmodics, anticholinergics, analgesics; or may be associated with systemic disorders, such as diabetes mellitus and hypothyroidism.  Idiopathic constipation should be considered once the secondary causes are ruled out and it may be associated with normal or slow colonic transit, dysfunction in defecation, or both. Constipation in childhood often resolves with age after proper guidance regarding diet, toilet training, and toileting behaviors.

# Differentiating Constipation overview from Other Diseases
Diseases that cause constipation should differentiate from each others, such as malignancy, diabetic autonomic neuropathy, irritable bowel syndrome, rectocele, fissure, anismus, systemic sclerosis, hypothyroidism, Parkinson's disease, multiple sclerosis, hypomagnesemia, hypocalcemia, and depression.

# Epidemiology and Demographics
The incidence of constipation is approximately 16,666 per 100,000 individuals in general population (one in every six). The prevalence of constipation is approximately 2,000 to 28,000 per 100,000 individuals in general population. It is estimated that 4-56 million people are suffering from constipation in United States. The prevalence of constipation is approximately 1,900 to 27,200 (with an average of 14,800) per 100,000 individuals in North America. The general decline in 10-year survival rate of people with functional constipation is about 12%, comparing to normal population. The incidence of constipation increases with age. The non-White to White ratio of involving in constipation is from 1.13 to 2.89 (Mean 1.68, Median 1.41). Females are more commonly affected by constipation than males. The female to male ratio is approximately 2.2 to 1. Developing countries with lower income show higher prevalence of constipation rather than developed countries with higher income. Educational years in the population show an inverse relationship with prevalence of constipation.

# Risk Factors
The most potent risk factor in the development of constipation is inappropriate diet. Common risk factors include female gender, > 65 years of age, pregnancy, and Iron supplements.

# Screening
According to the USPSTF, screening for constipation is not recommended in general population. In palliative care patients, screening for constipation by specific questionnaire about subjective and objective findings is recommended.

# Natural History, Complications, and Prognosis
The symptoms of constipation can develop in the different decades of life, and starts with symptoms such as bloating, mucus passage, and abdominal pain. Then the symptoms increase in severity by hardening of stool which is contributes to straining and inability to pass the stool, may be need for manual evacuation. Common complications of chronic constipation include hemorrhoid, anal fissure, fecal impaction, and rectal prolapse. The colonic transit time (CTT) more than 100 hours is associated with a particularly poor prognosis among patients with constipation.

# Diagnosis

## Diagnostic study of choice
Diagnostic study of choice for constipation is ROME III criteria. Rome III criteria includes symptom onset for more than 6 months and two or more number of specific symptoms. Specific symptoms of constipation include straining, hard stool, sensation of incomplete evacuation, sensation of obstruction, necessity of manual maneuvers, less than 3 bowel movements per week, lack of loose stool, and lack of irritable bowel syndrome (IBS).

## History and Symptoms
A positive history of straining, hard stools, sensation of incomplete evacuation, sensation of anorectal obstruction, use of manual maneuvers, and less than 3 defecations weekly is suggestive of constipation. The most common symptoms of constipation include infrequent bowel movements, abdominal bloating, necessity to strain, and anal pain. Less common symptoms of constipation include abdominal fullness, visible abdominal distention, incomplete evacuation, abdominal pain, rectal bleeding, and mass protrusion. Bristol Stool Form Scale and Patient Assessment Constipation-Quality of Life (PAC-QOL) are two questionnaire based on patients symptoms, help to diagnose constipation and quality of life in constipated patients.

## Physical Examination
Physical examination of patients with constipation is usually remarkable for anal fissure or palpable lumpy mass in abdomen (particularly in left quadrant). The presence of thrombosed external hemorrhoids, skin tags, rectal prolapse, anal fissure, anal warts, excoriation or evidence of pruritus ani due to fecal soiling on physical examination are suggestive of constipation. Patients with chronic constipation usually appear to be discomfort while sitting due to anal pain.

## Laboratory Findings
There are no diagnostic laboratory findings necessary for diagnosing constipation in young people without alarm signs. Laboratory test for exclusion of underlying diseases are complete blood count, blood urea nitrogen (BUN)/creatinine, serum phosphate levels, blood glucose levels, liver function tests (LFTs), fecal occult blood test, thyroid function tests, serum calcium levels, and serum magnesium levels. In case of high suspicion, other laboratory tests may be needed such as serum protein electrophoresis, urine porphyrins, serum parathyroid hormone, and serum cortisol levels.

## Abdominal X Ray
An abdominal X-ray may be helpful in the diagnosis of constipation. Findings on an X-ray suggestive of constipation is interpreted according to three scoring system, including Barr, Blethyn, and Leech systems. Barr scoring system is the first scoring method used to interpret abdominal X-ray suggestive of constipation. The total score of more than 10 was postulated as diagnosis of constipation. The revised scoring system of Blethyn (a simplified version of Barr scoring system) is based on the amount of remained feces in large bowel. The Blethyn scoring system consists of 4 grades of fecal retention in bowels. The most studies and organized scoring system for diagnosis of constipation is Leech method. The score of more than 8 is considered as constipation.

## CT
There are no CT scan findings associated with constipation.

## MRI
Different MRI modalities may be helpful in the diagnosis of constipation underlying diseases. Four types of MRI which are used for diagnosing constipation are conventional pelvic MRI, dynamic MRI (MR defecography), endoanal MRI, and fluoroscopic MRI. Pelvic MRI mostly reveals the general structure and anatomy of pelvic organs. Findings on MR defecography suggestive of constipation include various types of rectal prolapse (mucosal or full-thickness), disorders of pelvic floor muscles movements, very acute anorectal angle, and Increased perineal descent degree during rectal evacuation. The major findings on endoanal MRI are thinning of sphincter muscles, disruption of sphincter muscles, and changes in the anorectal angle. MRI fluoroscopy is a real time modality that evaluates the pelvic floor and viscera during defecation, valsalva maneuver, and evacuation process.

## Ultrasound
Endoanal ultrasound may be helpful for diagnosing underlying diseases causing constipation, particularly sphincter pathologies. Findings on an ultrasound suggestive of sphincter disorders are decline in thickness, depth, and size of the sphincter muscle. Endoanal ultrasound findings are scored through Starck scoring system, based on thickness, depth, and size of the sphincter muscles. The sphincter abnormality is classified as small (score of 1-4), moderate (score of 5-7), or large (score of 8-16).

## Other imaging findings
Barium enema may be helpful in diagnosing underlying diseases of constipation. Findings on a barium enema suggestive of constipation are redundant sigmoid colon, megacolon, megarectum, extrinsic compression, and intraluminal masses. Defecography may be helpful in diagnosing underlying diseases causing constipation. Findings on a defecography suggestive of constipation are poor activation of levator ani muscle, prolonged retention or inability to expel the barium, absence of a stripping wave in the rectum, mucosal intussusceptions, or rectocele. The transit time of the colon can be measured by means of various methods, include radiopaque marker ingestion, radioisotope and scintigraphy study, and wireless motility capsule.

## Other diagnostic studies
Endoscopic evaluation of patients with constipation include flexible sigmoidoscopy and colonoscopy. Flexible sigmoidoscopy is the direct visualization of the rectum and sigmoid colon. However, colonoscopy is study of the whole colon lumen. Every patient with alarm signs have to be evaluated using colonoscopy. In younger patients, flexible sigmoidoscopy would be sufficient for further investigation of alarm signs. Colonic manometry is 24-hour measurement of pressure within the large bowel, using specific probes and portable recorders. Anorectal manometry is studying the pressure activity of anorectum during rest and defecation, along with rectal sensation, rectoanal reflexes, and anal sphincter function. Balloon expulsion test is a simple bedside test to evaluate the ability of patient to evacuate the artificial stool. Rectal biostat test consists of a very compliant plastic balloon, which is inserted into the rectum, concurrently connected to computer device to measure the pressure.

# Treatment

## Medical Therapy
Chronic constipation treatment includes both behavioral and pharmacological interventions. Behavioral management mostly consists of life style and dietary modification, while pharmacological interventions are mostly based on laxatives. Increasing physical activity is postulated to improve constipation and colonic transit time in patients with constipation. The most important behavioral treatment for constipation is biofeedback, consisting of teaching the patients how to use their abdominal and pelvic muscles during defecation. Probiotics are live microorganisms that are eaten to improve the gastrointestinal tract function. Recently, use of probiotics in food industry is growing. Bifidobacterium and Lactobacillus are most studied organisms as probiotics.

## Surgery
Surgery is not the first-line treatment option for patients with constipation. Surgery is usually reserved for patients with either rectopexy, total colectomy, and subtotal colectomy with ileorectal anastomosis.

## Primary Prevention
Constipation is usually easier to prevent than to treat. The relief of constipation with osmotic agents, i.e., lactulose, polyethylene glycol (PEG), or magnesium salts, should also be immediately followed by prevention using increased fiber (fruits, vegetables, and grains) and a nightly decreasing dose of osmotic laxative. Effective measures for the primary prevention of constipation include fiber supplementation, appropriate fluid intake, toilet habits, and exercise.

## Secondary Prevention
Effective measures for the secondary prevention of constipation include appropriate dietary modification and addition of fiber, suitable laxative and stool softener therapies, and avoiding harmful food products while constipated.