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

Imperforate anus has an estimated incidence of 1 in 5000 births. It affects boys and girls with similar frequency. However, imperforate anus will present as the low version 90% of the time in females and 50% of the time in males.

Imperforate anus is an occasional complication of sacrococcygeal teratoma.

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)

With a high lesion, many children have problems controlling bowel function and most also become constipated. With a low lesion, children generally have good bowel control, but they may still become constipated.

For children who have a poor outcome for continence and constipation from the initial surgery, further surgery to better establish the angle between the anus and the rectum may improve continence and, for those with a large rectum, surgery to remove that dilated segment may significantly improve the bowel control for the patient. An antegrade enema mechanism can be established by joining the appendix to the skin (Malone stoma); however, establishing more normal anatomy is the priority.

For adults, the following may help prevent anal fissures:

- Avoiding straining when defecating. This includes treating and preventing constipation by eating food rich in dietary fiber, drinking enough water, occasional use of a stool softener, and avoiding constipating agents. Similarly, prompt treatment of diarrhea may reduce anal strain.

- Careful anal hygiene after defecation, including using soft toilet paper and cleaning with water, plus the use of sanitary wipes.

- In cases of pre-existing or suspected fissure, use of a lubricating ointment (It is important to note that hemorrhoid ointment is contraindicated because it constricts small blood vessels, thus causes a decrease in blood flow, which prevents healing.)

In infants, frequent diaper change can prevent anal fissure. As constipation can be a cause, making sure the infant is drinking enough fluids (i.e. breastmilk, proper ratios when mixing formulas) is beneficial. In infants, once an anal fissure has occurred, addressing underlying causes is usually enough to ensure healing occurs.

Most anal fissures are caused by stretching of the anal mucosa beyond its capability.

Superficial or shallow anal fissures look much like a paper cut, and may be hard to detect upon visual inspection, they will generally self-heal within a couple of weeks. However, some anal fissures become chronic and deep and will not heal. The most common cause of non-healing is spasming of the internal anal sphincter muscle which results in impaired blood supply to the anal mucosa. The result is a non-healing ulcer, which may become infected by fecal bacteria.

In adults, fissures may be caused by constipation, the passing of large, hard stools, or by prolonged diarrhea. In older adults, anal fissures may be caused by decreased blood flow to the area. When fissures are found laterally, tuberculosis, occult abscesses, leukemic infiltrates, carcinoma, acquired immunodeficiency syndrome (AIDS) or inflammatory bowel disease should be considered as causes. Some sexually transmitted infections can promote the breakdown of tissue resulting in a fissure. Examples of sexually transmitted infections that may affect the anorectal area are syphilis, herpes, chlamydia and human papilloma virus.

Other common causes of anal fissures include:

- childbirth trauma in women

- anal sex

- Crohn's disease

- ulcerative colitis

- poor toileting in young children.

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.

The precise cause is unknown, and has been much debated. In 1912 Moschcowitzl proposed that rectal prolapse was a sliding hernia through a pelvic fascial defect.

This theory was based on the observation that rectal prolapse patients have a mobile and unsupported pelvic floor, and a hernia sac of peritoneum from the Pouch of Douglas and rectal wall can be seen. Other adjacent structures can sometimes be seen in addition to the rectal prolapse. Although a pouch of Douglas hernia, originating in the cul de sac of Douglas, may protrude from the anus (via the anterior rectal wall), this is a different situation from rectal prolapse.

Shortly after the invention of defecography, In 1968 Broden and Snellman used cinedefecography to show that rectal prolapse begins as a circumferential intussusception of the rectum, which slowly increases over time. The leading edge of the intussusceptum may be located at 6–8 cm or at 15–18 cm from the anal verge. This proved an older theory from the 18th century by John Hunter and Albrecht von Haller that this condition is essentially a full-thickness rectal intussusception, beginning about 3 inches above the dentate line and protruding externally.

Since most patients with rectal prolapse have a long history of constipation, it is thought that prolonged, excessive and repetitive straining during defecation may predispose to rectal prolapse. Since rectal prolapse itself causes functional obstruction, more straining may result from a small prolapse, with increasing damage to the anatomy. This excessive straining may be due to predisposing pelvic floor dysfunction (e.g. obstructed defecation) and anatomical factors:

- Abnormally low descent of the peritoneum covering the anterior rectal wall

- poor posterior rectal fixation, resulting in loss of posterior fixation of the rectum to the sacral curve

- loss of the normal horizontal position of the rectum with lengthening (redundant rectosigmoid) and downward displacement of the sigmoid and rectum

- long rectal mesentery

- a deep cul-de-sac

- levator diastasis

- a patulous, weak anal sphincter

Some authors question whether these abnormalities are the cause, or secondary to the prolapse. Other predisposing factors/associated conditions include:

- pregnancy (although 35% of women who develop rectal prolapse are nulliparous (have never given birth)

- previous surgery (30-50% of females with the condition underwent previous gynecological surgery)

- pelvic neuropathies and neurological disease

- high gastrointestinal helminth loads (e.g. Whipworm)

- COPD

- cystic fibrosis

The association with uterine prolapse (10-25%) and cystocele (35%) may suggest that there is some underlying abnormality of the pelvic floor that affects multiple pelvic organs. Proximal bilateral pudendal neuropathy has been demonstrated in patients with rectal prolapse who have fecal incontinence. This finding was shown to be absent in healthy subjects, and may be the cause of denervation-related atrophy of the external anal sphincter. Some authors suggest that pudendal nerve damage is the cause for pelvic floor and anal sphincter weakening, and may be the underlying cause of a spectrum of pelvic floor disorders.

Sphincter function in rectal prolapse is almost always reduced. This may be the result of direct sphincter injury by chronic stretching of the prolapsing rectum. Alternatively, the intussuscepting rectum may lead to chronic stimulation of the rectoanal inhibitory reflex (RAIR - contraction of the external anal sphincter in response to stool in the rectum). The RAIR was shown to be absent or blunted. Squeeze (maximum voluntary contraction) pressures may be effected as well as the resting tone. This is most likely a denervation injury to the external anal sphincter.

The assumed mechanism of fecal incontinence in rectal prolapse is by the chronic stretch and trauma to the anal sphincters and the presence of a direct conduit (the intussusceptum) connecting rectum to the external environment which is not guarded by the sphincters.

The assumed mechanism of obstructed defecation is by disruption to the rectum and anal canal's ability to contract and fully evacuate rectal contents. The intussusceptum itself may mechanically obstruct the rectoanal lumen, creating a blockage that straining, anismus and colonic dysmotility exacerbate.

Some believe that internal rectal intussusception 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. However, internal intussusception rarely progresses to external rectal prolapse. The factors that result in a patient progressing from internal intussusception to a full thickness rectal prolapse remain unknown. Defecography studies demonstrated that degrees of internal intussusception are present in 40% of asymptomatic subjects, raising the possibility that it represents a normal variant in some, and may predispose patients to develop symptoms, or exacerbate other problems.

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.

The prognostic outcomes for this type of cloaca are good for bowel control and urinary function. The surgical repair for this type of cloaca can usually be done by performing posterior sagittal approach without opening of the abdomen. A common channel longer than 3 cm in length usually has poor sphincter muscles and a poor sacrum, suggesting a prognostic outcome for bowel control and urinary function to be less likely. Common channels longer than 3 cm are generally considered more complex and more technically challenging in surgical repair.

Cloacas appear in a wide spectrum of variation in females born with the malformation. The single orifice, called a common channel, may occur varying in length from 1 to 10 cm. The length of the common channel can be used to judge prognostic outcomes and technical challenges during surgical repair. A common channel less than 3 cm in length usually has good sphincter muscles and a well-developed sacrum.

Anal stricture or anal stenosis is a narrowing of the anal canal. It can be caused by a number of surgical procedures including: hemorrhoid removal and following anorectal wart treatment.

The most common cause of non-duodenal intestinal atresia is a vascular accident in utero that leads to decreased intestinal perfusion and ischemia of the respective segment of bowel. This leads to narrowing, or in the most severe cases, complete obliteration of the intestinal lumen.

In the case that the superior mesenteric artery, or another major intestinal artery, is occluded, large segments of bowel can be entirely underdeveloped. Classically, the affected area of bowel assumes a spiral configuration and is described to have an "apple peel" like appearance; this is accompanied by lack of a dorsal mesentery.

Ileal atresia can also result as a complication of meconium ileus.

Fetal and neonatal intestinal atresia are treated using laparotomy after birth. If the area affected is small, the surgeon may be able to remove the damaged portion and join the intestine back together. In instances where the narrowing is longer, or the area is damaged and cannot be used for period of time, a temporary stoma may be placed.

An acquired umbilical hernia directly results from increased intra-abdominal pressure caused by obesity, heavy lifting, a long history of coughing, or multiple pregnancies.

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.

Navels with the umbilical tip protruding past the umbilical skin ("outies") are often mistaken for umbilical hernias, which are a completely different shape. Treatment for cosmetic purposes is not necessary, unless there are Incarceration refers to the inability to reduce the hernia back into the abdominal cavity. Prolonged incarceration can lead to tissue ischemia (strangulation) and shock when untreated.

Umbilical hernias are rare. With a study involving Africans, 92% of children had protrusions, 49% of adults, and 90% of pregnant women. However, a much smaller amount actually suffered from hernias: only 23% of children, 8% of adults, and 15% of pregnant women.

When the orifice is small (< 1 or 2 cm), 90% close within 3 years (some sources state 85% of all umbilical hernias, regardless of size), and if these hernias are asymptomatic, reducible, and don't enlarge, no surgery is needed (and in other cases it must be considered).

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.

Atresia is a condition in which an orifice or passage in the body is (usually abnormally) closed or absent.

Examples of atresia include:

- Biliary atresia, a condition in newborns in which the common bile duct between the liver and the small intestine is blocked or absent.

- Choanal atresia, blockage of the back of the nasal passage, usually by abnormal bony or soft tissue.

- Esophageal atresia, which affects the alimentary tract and causes the esophagus to end before connecting normally to the stomach.

- Imperforate anus, malformation of the opening between the rectum and anus.

- Intestinal atresia, malformation of the intestine, usually resulting from a vascular accident in utero.

- Microtia, absence of the ear canal or failure of the canal to be tubular or fully formed (can be related to Microtia, a congenital deformity of the pinna, or outer ear).

- Ovarian follicle atresia, the degeneration and subsequent resorption of one or more immature ovarian follicles.

- Potter sequence, congenital decreased size of the kidney leading to absolutely no functionality of the kidney, usually related to a single kidney.

- Pulmonary atresia, malformation of the pulmonary valve in which the valve orifice fails to develop.

- Renal agenesis, only having one kidney.

- Tricuspid atresia, a form of congenital heart disease whereby there is a complete absence of the tricuspid valve, and consequently an absence of the right atrioventricular connection.

- Vaginal atresia, a congenital occlusion of the vagina or subsequent adhesion of the walls of the vagina, resulting in its occlusion.

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."

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.

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.

A fistula is an abnormal connection between two hollow spaces (technically, two epithelialized surfaces), such as blood vessels, intestines, or other hollow organs. Fistulas are usually caused by injury or surgery, but they can also result from an infection or inflammation. Fistulas are generally a disease condition, but they may be surgically created for therapeutic reasons.

In botany, the term is most common in its adjectival forms, where it is used in binomial names to refer to species that are distinguished by hollow or tubular structures. Monarda fistulosa, for example, has tubular flowers; Eutrochium fistulosum has a tubular stem; and Allium fistulosum has hollow or tubular leaves.

Various types of fistulas include:

Although most fistulas are in forms of a tube, some can also have multiple branches.

Unlike oesophageal varices, rectal varices are less prone to bleeding, are less serious when a bleed does occur, and are easier to treat because of the more accessible location.

Typically, treatment consists of addressing the underlying portal hypertension. Some treatments include portosystemic shunting, ligation, and under-running suturing. Insertion of a transjugular intrahepatic portosystemic shunt (TIPS) has been shown to alleviate varices caused by portal hypertension. Successful treatment of portal hypertension that subsequently reduces anorectal varices provides a confirmation of the initial diagnosis, allowing for a distinction between varices and hemorrhoids, which would not have been alleviated by reduction of portal hypertension.