One review stated that the most common causes of disruption to the defecation cycle are associated with pregnancy and childbirth, gynaecological descent or neurogenic disturbances of the brain-bowel axis. Patients with obstructed defecation appear to have impaired pelvic floor function.

Specific causes include:

- Anismus and pelvic floor dysfunction

- Rectocele

- "Rectal invagination" (likely refers to rectal intussusception)

- Internal anal sphincter hypertonia

- Anal stenosis

- Fecal impaction

- Rectal or anal cancer

- Descending perineum syndrome

There are 2 schools of thought regarding the nature of internal intussusception, viz: whether it is a primary phenomenon, or secondary to (a consequence of) another condition.

Some believe that it represents the initial form of a progressive spectrum of disorders the extreme of which is external rectal prolapse. The intermediary stages would be gradually increasing sizes of intussusception. The folding section of rectum can cause repeated trauma to the mucosa, and can cause solitary rectal ulcer syndrome. However, internal intussusception rarely progresses to external rectal prolapse.

Others argue that the majority of patients appear to have rectal intussusception as a consequence of obstructed defecation rather than a cause, possibly related to excessive straining in patients with obstructed defecation. Patients with other causes of obstructed defecation (outlet obstruction) like anismus also tend to have higher incidence of internal intussusception. Enteroceles are coexistent in 11% of patients with internal intussusception. Symptoms of internal intussusception overlap with those of rectocele, indeed the 2 conditions can occur together.

Patients with solitary rectal ulcer syndrome combined with internal intussusception (as 94% of SRUS patients have) were shown to have altered rectal wall biomechanics compared to patients with internal intussusception alone. The presumed mechanism of the obstructed defecation is by telescoping of the intussusceptum, occluding the rectal lumen during attempted defecation. One study analysed resected rectal wall specimens in patients with obstructed defecation associated with rectal intussusception undergoing stapled trans-anal rectal resection. They reported abnormalities of the enteric nervous system and estrogen receptors. One study concluded that intussusception of the anterior rectal wall shares the same cause as rectocele, namely deficient recto-vaginal ligamentous support.

Although SRUS is not a medically serious disease, it can be the cause of significantly reduced quality of life for patients. It is difficult to treat, and treatment is aimed at minimizing symptoms.

Stopping straining during bowel movements, by use of correct posture, dietary fiber intake (possibly included bulk forming laxatives such as psyllium), stool softeners (e.g. polyethylene glycol, and biofeedback retraining to coordinate pelvic floor during defecation.

Surgery may be considered, but only if non surgical treatment has failed and the symptoms are severe enough to warrant the intervention. Improvement with surgery is about 55-60%.

Ulceration may persist even when symptoms resolve.

Liquid stool is more difficult to control than formed, solid stool. Hence, FI can be exacerbated by diarrhea. Some consider diarrhea to be the most common aggravating factor. Orlistat is an anti-obesity (weight loss) drug that blocks the absorption of fats. This may give side effects of FI, diarrhea and steatorrhea.

This may occur when there is a large mass of feces in the rectum (fecal loading), which may become hardened (fecal impaction). Liquid stool elements are able to pass around the obstruction, leading to incontinence. Megarectum (enlarged rectal volume) and rectal hyposensitivity are associated with overflow incontinence. Hospitalized patients and care home residents may develop FI via this mechanism, possibly a result of lack of mobility, reduced alertness, constipating effect of medication and/or dehydration.

Tenesmus is characterized by a sensation of needing to pass stool, accompanied by pain, cramping, and straining. Despite straining, little stool is passed. Tenesmus is generally associated with inflammatory diseases of the bowel, which may be caused by either infectious or noninfectious conditions. Conditions associated with tenesmus include:

- Amebiasis

- Coeliac disease

- Chronic arsenic poisoning

- Colorectal cancer

- Anal melanoma

- Cytomegalovirus (in immunocompromised patients)

- Diverticular disease

- Hemorrhoid, which are prolapsed

- Inflammatory bowel disease

- Irritable bowel syndrome

- Ischemic colitis

- Kidney stones, when a stone is lodged in the lower ureter

- Pelvic floor dysfunction

- Radiation proctitis

- Rectal gonorrhoea

- Rectal lymphogranuloma venereum

- Rectal lower gastrointestinal parasitic infection, particularly "Trichuris trichiura" (whipworm)

- Shigellosis

- Ulcerative colitis

Tenesmus (rectal) is also associated with the installation of either a reversible or non reversible stoma where rectal disease may or may not be present. Patients who experience tenesmus as a result of stoma installation can experience the symptoms of tenesmus for the duration of the stoma presence. Long term pain management may need to be considered as a result.

Obstructed defecation has many causes, so the management in any individual case is specific to the cause of the symptom. For rectal internal intususception treatment is surgical, either STARR or rectopexy. For rectocele STARR or mesh implantation. For anismus/ pelvic floor dessynergia: biofeedback exercise.

One of the main causes is suggested to be excessive and repetitive straining during defecation. Other causes include weakness of the pelvic floor muscles (secondary to age related neuropathic degeneration or traumatic injury during pregnancy and labor.

When the fecal stream is diverted as part of a colostomy, a condition called diversion colitis may develop in the section of bowel that no longer is in contact with stool. The mucosal lining is nourished by short-chain fatty acids, which are produced as a result of bacterial fermentation in the gut. Long-term lack of exposure to this nutrients can cause inflammation of the colon (colitis). Symptoms include rectal bleeding, mucous discharge, tenesmus and abdominal pain.

Anal warts are irregular, verrucous lesions caused by human papilloma virus. Anal warts are usually transmitted by unprotected, anoreceptive intercourse. Anal warts may be asymptomatic, or may cause rectal discharge, anal wetness, rectal bleeding, and pruritus ani. Lesions can also occur within the anal canal, where they are more likely to create symptoms.

Several definitions have been offered:

- "Absence of normal relaxation of pelvic floor muscles during defecation, resulting in rectal outlet obstruction".

- "Malfunction (a focal dystonia) of the external anal sphincter and puborectalis muscle during defecation".

- "[...] failure of [the external anal sphincter and puborectalis] muscle[s] to relax, resulting in maintenance of the anorectal angle and the difficulty with initiating and completing bowel movements".

- "[...] failure of relaxation (or paradoxic contraction) of the puborectalis muscle sling during defaecation, attempted defaecation or straining."

Rectoceles result from the weakening of the pelvic floor also called pelvic organ prolapse. Weakened pelvic structures occur as a result of an episiotomy during previous births, even decades later. Other causes of pelvic floor prolapse can be advanced age, multiple vaginal deliveries, and birthing trauma. Birthing trauma includes vacuum delivery, forceps delivery, and perineal tear. In addition, a history of chronic constipation and excessive straining with bowel movements are thought to play a role in rectocele. Multiple gynecological or rectal surgeries can also lead to weakening of the pelvic floor. Births that involve babies over nine pounds in weight, or rapid births can contribute to the development of rectocele.

A hysterectomy or other pelvic surgery can be a cause, as can chronic constipation and straining to pass bowel movements. It is more common in older women than in younger ones; estrogen which helps to keep the pelvic tissues elastic decreases after menopause.

Treatment depends on the severity of the problem, and may include non-surgical methods such as changes in diet (increase in fiber and water intake), pelvic floor exercises such as Kegel exercises, use of stool softeners, hormone replacement therapy for post-menopausal women and insertion of a pessary into the vagina. A high fiber diet, consisting of 25-30 grams of fiber daily, as well as increased water intake (typically 6-8 glasses daily), help to avoid constipation and straining with bowel movements, and can relieve symptoms of rectocele.

Rectovaginal fistulas are often the result of trauma during childbirth (in which case it is known as obstetric fistula) where improper medical interventions are used, such as episiotomy with forceps/vacuum extraction or in situations where there is inadequate health care, such as in some developing countries. Rectovaginal fistula is said to be known as the leading cause in maternal death in developing countries. Risk factors include prolonged labour, difficult instrumental delivery and paramedian episiotomy. Rates in Eritrea are estimated as high as 350 per 100,000 vaginal births. Fistulas can also develop as a result of physical trauma to either the vagina or anus, including from rape. Women with rectovaginal fistulae are often stigmatized in developing countries, and become outcasts.

Rectovaginal fistula can also be a symptom of various diseases, including infection by lymphogranuloma venereum, or the unintended result of surgery, such as episiotomy or sexual reassignment surgery. They may present as a complication of vaginal surgery, including vaginal hysterectomy. They are a recognized presentation of rectal carcinoma or rarely diverticular disease of the bowel or Crohn's disease. They are seen rarely after radiotherapy treatment for cervical cancer.

Anismus is classified as a functional defecation disorder. It is also a type of rectal outlet obstruction (a functional outlet obstruction). Where anismus causes constipation, it is an example of functional constipation. Some authors describe an "obstructed defecation syndrome", of which anismus is a cause.

The Rome classification subdivides functional defecation disorders into 3 types, however the symptoms the patient experiences are identical.

- Type I: paradoxical contraction of the pelvic floor muscles during attempted defecation

- Type II: inadequate propulsive forces during attempted defecation (inadequate defecatory propulsion)

- Type III: impaired relaxation with adequate propulsion

It can be seen from the above classification that many of the terms that have been used interchangeably with anismus are inappropriately specific and neglect the concept of impaired propulsion. Similarly, some of the definitions that have been offered are also too restrictive.

Rectovestibular fistula is the most common defect of the rectum and anal canal in females.

Rectal tenesmus (Latin, from Greek teinesmos, from teinein to stretch, strain) is a feeling of incomplete defecation. It is the sensation of inability or difficulty to empty the bowel at defecation, even if the bowel contents have already been evacuated. Tenesmus indicates the feeling of a residue, and is not always correlated with the actual presence of residual fecal matter in the rectum. It is frequently painful and may be accompanied by involuntary straining and other gastrointestinal symptoms.

Tenesmus has both a nociceptive and a neuropathic component.

Vesical tenesmus is a similar condition, experienced as a feeling of incomplete voiding despite the bladder being empty.

Often, rectal tenesmus is simply called tenesmus. The term rectal tenesmus is a retronym to distinguish defecation-related tenesmus from vesical tenesmus.

Tenesmus is a closely related topic to obstructed defecation.

Proctitis has many possible causes. It may occur idiopathically (idiopathic proctitis). Other causes include damage by irradiation (for example in radiation therapy for cervical cancer and prostate cancer) or as a sexually transmitted infection, as in lymphogranuloma venereum and herpes proctitis. Studies suggest a celiac disease-associated "proctitis" can result from an intolerance to gluten.

A common cause is engaging in anal sex with partner(s) infected with sexual transmitted diseases in men who have sex with men. Shared enema usage has been shown to facilitate the spread of Lymphogranuloma venereum proctitis.

Surgical treatments may be used to treat the condition, and include retro-rectal levatorplasty, post-anal repair, retro-anal levator plate myorrhaphy.

Genital prolapse occurs in about 316 million women worldwide as of 2010 (9.3% of all females).

Anorectal anomalies are medical problems affecting the structure of the anus and rectum. A person with an anorectal problem would have some sort of deformative feature of the anus or rectum, collectively known as an anorectal malformation.

Examples of anorectal anomalies include:

- Anal stenosis

- Imperforate anus

- Proctitis

- Anal bleeding

- Anal fistula

- Anal cancer

- Anal itching

- Hemorrhoid (piles)

A rectovestibular fistula, also referred to simply as a vestibular fistula, is an anorectal congenital disorder where an abnormal connection (fistula) exists between the rectum and the vulval vestibule of the female genitalia.

If the fistula occurs within the hymen, it is known as a rectovaginal fistula, a much rarer condition.

A rectovaginal fistula is a medical condition where there is a fistula or abnormal connection between the rectum and the vagina.

Rectovaginal fistula may be extremely debilitating. If the opening between the rectum and vagina is wide it will allow both flatulence and feces to escape through the vagina, leading to fecal incontinence. There is an association with recurrent urinary and vaginal infections. The fistula may also connect the rectum and urethra, which is called recto-urethral fistula. Either conditions can lead to labial fusion. This type of fistula can cause pediatricians to misdiagnose imperforate anus. The severity of the symptoms will depend on the size of fistula. Most often, it appears after about one week or so after delivery.

Megarectum is a large rectum as a result of underlying nerve supply abnormalities or muscle dysfunction, which remains after disimpaction of the rectum. The Principles of Surgery textbook describes any rectum that can hold more than 1500cc of fluid as a megarectum. The term megarectum is also used for a large rectal mass on rectal examination, a wide rectum on an abdominal x-ray, the presence of impaired rectal sensation or the finding of large maximal rectal volumes on anorectal manometry. In addition, can be the bloating of the colon due to infection, also called megacolon. On defecography, megarectum is suggested by a rectal width of >9 cm at the level of the distal sacrum.

In dogs, perineal hernia usually is found on the right side. Most cases are in older intact (not neutered) male dogs (93 percent in one study). Breeds that may be at risk include Welsh Corgis, Boxers, Australian Kelpies, Boston Terriers, Collies, Dachshunds, Old English Sheepdogs, and Pekingese. Perineal hernias are rare in female dogs and uncommon in cats.

Dogs with benign prostatic hyperplasia have been found to have increased relaxin levels and suspected subsequent weakening of the pelvic diaphragm. In cats, perineal hernias are seen most commonly following perineal urethrostomy surgery or secondary to megacolon. Medical treatment consists of treatment of the underlying disease, enemas, and stool softeners. Because only about 20 percent of cases treated medically are free of symptoms, surgery is often necessary. Recurrence is common with or without surgery.

Several surgeries have been described for perineal hernias in dogs. The current standard involves transposition of the internal obturator muscle. This technique has a lower recurrence and complication rate than traditional hernia repair. A new technique uses porcine small intestinal submucosa as a biomaterial to help repair the defect. This is can also be done in combination with internal obturator muscle transposition, especially when that muscle is weak.