There are several forms of imperforate anus and anorectal malformations. The new classification is in relation of the type of associated fistula.

The classical Wingspread classification was in low and high anomalies:

- A low lesion, in which the colon remains close to the skin. In this case, there may be a stenosis (narrowing) of the anus, or the anus may be missing altogether, with the rectum ending in a blind pouch.

- A high lesion, in which the colon is higher up in the pelvis and there is a fistula connecting the rectum and the bladder, urethra or the vagina.

- A persistent cloaca (from the term cloaca, an analogous orifice in reptiles and amphibians), in which the rectum, vagina and urinary tract are joined into a single channel.

Imperforate anus is usually present along with other birth defects—spinal problems, heart problems, tracheoesophageal fistula, esophageal atresia, renal anomalies, and limb anomalies are among the possibilities.

Imperforate anus is associated with an increased incidence of some other specific anomalies as well, together being called the VACTERL association:

- V – Vertebral anomalies

- A – "Anal atresia"

- C – Cardiovascular anomalies

- T – Tracheoesophageal fistula

- E – Esophageal atresia

- R – Renal (kidney) and/or radial anomalies

- L – Limb defects

Other entities associated with an imperforate anus are trisomies 18 and 21, the cat-eye syndrome (partial trisomy or tetrasomy of a maternally derived number 22 chromosome), Baller-Gerold syndrome, Currarino syndrome, caudal regression syndrome, FG syndrome, Johanson-Blizzard syndrome, McKusick-Kaufman syndrome, Pallister-Hall syndrome, short rib-polydactyly syndrome type 1, Townes-Brocks syndrome, 13q deletion syndrome, urorectal septum malformation sequence, and the OEIS complex (omphalocele, exstrophy of the cloaca, imperforate anus, spinal defects).

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)

If a colostomy is not performed immediately after birth, patients with rectovestibular fistulae may present later in life with complications including severe constipation and megacolon (abnormal dilation of the colon), requiring colostomy or further surgery.

The diagnosis of a rectovestibular fistula can be made in female newborns if the vulva is stained with meconium (the earliest form of stool in an infant). The opening of the anus may be difficult to see due to its small size and position, but it may be visible as a thickening of the median perineal raphe with an obvious anal dimple. Patients with rectovestibular fistulae are commonly misdiagnosed with rectovaginal fistulae.

Diagnosis of a female with cloaca should be suspected in a female born with an imperforate anus and small looking genitalia. The diagnosis can be made clinically. Failure to identify a cloaca as being present in a newborn may be dangerous, as more than 90% have associated urological problems. The goal for treatment of a female born with cloaca is to achieve bowel control, urinary control, and sexual function, which includes menstruation, sexual intercourse, and possibly pregnancy. Cloacas probably occur in 1 in 20,000 live births.

Intestinal atresias are often discovered before birth: either during a routine sonogram which shows a dilated intestinal segment due to the blockage, or by the development of polyhydramnios (the buildup of too much amniotic fluid in the uterus). These abnormalities are indications that the fetus may have a bowel obstruction which a more detailed ultrasound study can confirm.

Some fetuses with bowel obstruction have abnormal chromosomes. An amniocentesis is recommended because it can determine not only the sex of the baby, but whether or not there is a problem with the chromosomes.

A persistent cloaca is a symptom of a complex anorectal congenital disorder, in which the rectum, vagina, and urinary tract meet and fuse, creating a cloaca, a single common channel.

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.

Intestinal atresia is a malformation where there is a narrowing or absence of a portion of the intestine. This defect can either occur in the small or large intestine.

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.

Symptoms and signs in the newborn can be sepsis, abdominal mass, and respiratory distress. Other abdominopelvic or perineal congenital anomalies frequently prompt radiographic evaluation in the newborn, resulting in a diagnosis of coincident vaginal atresia. Symptoms for vaginal atresia include cyclical abdominal pain, the inability to start having menstrual cycles, a small pouch or dimple where a vaginal opening should be, and pelvic mass when the upper vagina becomes filled with menstrual blood. Signs and symptoms of vaginal atresia or vaginal agenesis can often go unnoticed in females until they reach the age of menstruation. Women may also experience some form of abdominal pain or cramping.

Vaginal atresia can sometimes be diagnosed by physical examination soon after birth. A child with vaginal atresia often has other congenital abnormalities and other tests such as x-ray and tests to evaluate the kidney are done. Findings in adolescents may include abdominal pain, difficulty voiding, and backache, but most present with amenorrhea. Difficulties with sexual intercourse can suggest atresia. In the event that the condition is not caught shortly after birth, vaginal atresia becomes more evident when no menstrual cycle is occurs. If vaginal atresia is suspected by the doctor, a blood test may also be request for any of the previously mentioned syndromes, a magnetic resonance imaging (MRI) test, or an ultrasound. A regular evaluation of children born with an imperforate anus or anorectal malformation should be paired with the assessment of the results from these tests.

Malformations can be congenital. They are classified by location of the malformation, such as uterine malformation.

Alternatively, female genital diseases can be more strictly classified by location of the disease, which, in turn, can be broadly divided between diseases that affect the female internal genitalia and those that affect the female external genitalia.

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.

The key features of this syndrome are an enlargement of the fourth ventricle; complete absence of the cerebellar vermis, the posterior midline area of cerebellar cortex responsible for coordination of the axial musculature; and cyst formation near the internal base of the skull. An increase in the size of the fluid spaces surrounding the brain as well as an increase in pressure may also be present. The syndrome can appear dramatically or develop unnoticed.

Symptoms, which often occur in early infancy, include slower motor development and progressive enlargement of the skull. In older children, symptoms of increased intracranial pressure such as irritability, vomiting, and convulsions and signs of cerebellar dysfunction such as unsteadiness and lack of muscle coordination or jerky movements of the eyes may occur. Other symptoms include increased head circumference, bulging at the back of the skull, problems with the nerves that control the eyes, face and neck, and abnormal breathing patterns.

Dandy–Walker syndrome is frequently associated with disorders of other areas of the central nervous system including absence of the corpus callosum, the bundle of axons connecting the two cerebral hemispheres, and malformations of the heart, face, limbs, fingers and toes.

The Dandy–Walker complex is a genetically sporadic disorder that occurs one in every 30,000 live births. Prenatal diagnosis and prognosis of outcomes associated with Dandy–Walker can be difficult. Prenatal diagnosis is possible with ultrasound. Because the syndrome is associated with an increased risk for fetal karyotype abnormalities, amniocentesis can be offered after prenatal diagnosis. There is a relative contraindication of taking Warfarin during pregnancy, as it is associated with an increased risk of Dandy–Walker syndrome if taken during the first trimester.

The blockage of cerebrospinal fluid (CSF) flow may also cause a syrinx to form, eventually leading to syringomyelia. Central cord symptoms such as hand weakness, dissociated sensory loss, and, in severe cases, paralysis may occur.

Anal carcinoma is much less common than colorectal cancer. The most common form is squamous cell carcinoma, followed by adenocarcinoma and melanoma. SCC usually occurs in the anal canal, and more rarely on the anal margin. Anal margin SCC presents as a lesion with rolled, everted edges and central ulceration. Symptoms include a painful lump, bleeding, pruritus ani, tenesmus, discharge or possibly fecal incontinence. SSC in the anal canal most commonly causes bleeding, but may also cause anal pain, a lump, pruritus ani, discharge, tenesmus, change in bowel habits and fecal incontinence. Because these symptoms are so unspecific, and because symptoms of anal carcinoma may not always be typical, this can lead to delays in diagnosis.

Rare neoplasms at this site that can give rise to discharge include Paget's disease (which is possibly a type of adenocarcinoma) and verrucous carcinoma.

Various types of fistulas include:

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

Symptoms include:

- Straining to pass fecal material

- Tenesmus (a feeling of incomplete evacuation)

- Feeling of anorectal obstruction/blockage

- Digital maneuvers needed to aid defecation

- Difficulty initiating and completing bowel movements

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.

The DWS malformation is the most severe presentation of the syndrome. The posterior fossa is enlarged and the tentorium is in high position. There is complete agenesis of the cerebellar vermis. There is also cystic dilation of the fourth ventricle, which fills the posterior fossa. This often involves hydrocephalus and complications due to associated genetic conditions, such as Spina Bifida.

A common symptom is a continual urge to have a bowel movement—the rectum could feel full or have constipation. Another is tenderness and mild irritation in the rectum and anal region. A serious symptom is pus and blood in the discharge, accompanied by cramps and pain during the bowel movement. If there is severe bleeding, anemia can result, showing symptoms such as pale skin, irritability, weakness, dizziness, brittle nails, and shortness of breath.

Symptoms are ineffectual straining to empty the bowels, diarrhea, rectal bleeding and possible discharge, a feeling of not having adequately emptied the bowels, involuntary spasms and cramping during bowel movements, left-sided abdominal pain, passage of mucus through the rectum, and anorectal pain.

Solitary rectal ulcer syndrome

Colitis cystical profunda

Internal intussusception

Mucosal prolapse

Rectal prolapse