Imperforate anus usually requires immediate surgery to open a passage for feces unless a fistula can be relied on until corrective surgery takes place. Depending on the severity of the imperforate, it is treated either with a perineal anoplasty or with a colostomy.

While many surgical techniques to definitively repair anorectal malformations have been described. The posterior sagittal approach (PSARP) has become the most popular. It involves dissection of the perineum without entry into the abdomen and 90% of defects in boys can be repaired this way.

When an infant is born with an anorectal malformation, it is usually detected quickly as it is a very obvious defect. Doctors will then determine the type of birth defect the child was born with and whether or not there are any associated malformations. It is important to determine the presence of any associated defects during the newborn period in order to treat them early and avoid further sequelae. There are two main categories of anorectal malformations: those that require a protective colostomy and those that do not. The decision to open a colostomy is usually taken within the first 24 hours of birth.

Sonography can be used to determine the type of imperforate anus.

This condition takes several different forms, often involving one or more fistulas connecting the trachea to the esophagus (tracheoesophageal fistula).

"Diagnosis" is by examination, either in an outpatient setting or under anaesthesia (referred to as — Examination Under Anaesthesia). The fistula may be explored by using a fistula probe (a narrow instrument). In this way, it may be possible to find both openings. The examination can be an anoscopy. Diagnosis may be aided by performing a fistulogram, proctoscopy and/or sigmoidoscopy.

Possible findings:

- The opening of the fistula onto the skin may be observed

- The area may be painful on examination

- There may be redness

- An area of induration may be felt — thickening due to chronic infection

- A discharge may be seen

CLASSIFICATIONS of ANAL FISTULA

- Park's Classification: This was done in 1976 by Parks et al from UK. This was done in the era when MRI or Endoanal Ultrasound was not there. It classified the fistula in four grades

- St James University Hospital Classification: This was done by Morris et al in the year 2000. This classification was improvement over Parks classification as it was based on MRI studies. It classified the fistula in five grades.

- Garg Classification: This was done by Pankaj Garg in 2017. This classification is improvement over both Parks and St James University Hospital Classification. This was based on MRI studies and operative findings in 440 patients. It classified the fistula in five grades. The grades of this classification correlate quite well with the severity of the disease. Grade I & II are simpler fistulas and can be managed by Fistulotomy whereas grade III-V are complex fistulas in which fistulotomy should be not be done. They should be managed by Fistula experts. Unlike Park's and St James University Hospital Classification, this correlation is quite accurate with Garg's classification. Therefore this new classification is useful to both surgeons and radiologists

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.

This condition may be visible, after about 26 weeks, on an ultrasound. On antenatal USG, the finding of an absent or small stomach in the setting of polyhydramnios was considered a potential symptom of esophageal atresia. However, these findings have a low positive predictive value. The upper neck pouch sign is another sign that helps in the antenatal diagnosis of esophageal atresia and it may be detected soon after birth as the affected infant will be unable to swallow its own saliva. Also, the newborn can present with gastric distention, cough, apnea, tachypnea, and cyanosis. In many types of esophageal atresia, a feeding tube will not pass through the esophagus.

Colostomy is recommended by most surgeons, and has a good prognosis, with 90% of patients regaining normal bowel control. Since the rectal opening and anal orifice in a vestibular fistula tend to be short and narrow, a colostomy is usually performed to allow decompression of the bowel unless the orifice is wide enough to allow normal defecation. Colostomy is often followed by posterior sagittal anorectoplasty (PSARP), a surgical procedure to repair the anal orifice, at a later date. Some surgeons prefer to perform an immediate PSARP without a colostomy first, while others perform neither a colostomy nor a PSARP and instead opt for a simple dilatation of the orifice to allow stool to pass and the bowel to decompress. It has been suggested that only experienced surgeons should perform repair without an initial colostomy.

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.

Other conditions in which infected perianal "holes" or openings may appear include Pilonidal cysts/sinuses.

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.

It is surgically corrected, with resection of any fistula and anastomosis of any discontinuous segments.

Early treatment includes removing fluids from the stomach via a nasogastric tube, and providing fluids intravenously. The definitive treatment for duodenal atresia is surgery (duodenoduodenostomy), which may be performed openly or laparoscopically. The surgery is not urgent. The initial repair has a 5 percent morbidity and mortality rate.

SRUS is commonly misdiagnosed, and the diagnosis is not made for 5–7 years. Clinicians may not be familiar with the condition, and treat for Inflammatory bowel disease, or simple constipation.

The thickened lining or ulceration can also be mistaken for types of cancer.

The differential diagnosis of SRUS (and CCP) includes:

- polyps

- endometriosis

- inflammatory granulomas

- infectious disorders

- drug-induced colitis

- mucus-producing adenocarcinoma

Defecography, sigmoidoscopy, transrectal ultrasound, mucosal biopsy, anorectal manometry and electromyography have all been used to diagnose and study SRUS. Some recommend biopsy as essential for diagnosis since ulcerations may not always be present, and others state defecography as the investigation of choice to diagnose SRUS.

Diagnosis is by rectal examination. A specialized tool called a "Perineocaliper" can be used to measure the descent of the perineum. A retro anal ultrasound scan may demonstrate the condition. "Anti sagging tests", whereby the abnormal descent is corrected temporarily, may help to show whether symptoms are due to descending perineum syndrome or are in fact due to another condition.

Normally, the anal margin lies just below a line drawn between the coccyx (tailbone) and the pubic symphysis. In descending perineum syndrome the anal canal is situated several cm below this imaginary line, or it descends 3–4 cm during straining.

Defecography may also demonstrate abnormal perineal descent.

Fistulae between the trachea and esophagus in the newborn can be of diverse morphology and anatomical location; however, various pediatric surgical publications have attempted a classification system based on the below specified types.

Not all types include both esophageal agenesis and tracheoesophageal fistula, but the most common types do.

The letter codes are usually associated with the system used by Gross, while number codes are usually associated with Vogt.

An additional type, "blind upper segment only" has been described, but this type is not usually included in most classifications.

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.

The diagnosis of duodenal atresia is usually confirmed by radiography. An X-ray of the abdomen shows two large air filled spaces, the so-called "double bubble" sign. The air is trapped in the stomach and proximal duodenum, which are separated by the pyloric sphincter, creating the appearance of two bubbles visible on x-ray. Since the closure of the duodenum is complete in duodenal atresia, no air is seen in the distal duodenum.

Atresias occurring distal to the duodenum are usually caused by vascular accidents or ischemic insult, such as jejunoileal atresia.

Very few risk factors for choanal atresia have been identified. While causes are unknown, both genetic and environmental triggers are suspected. One study suggests that chemicals that act as endocrine disrupters may put an unborn infant at risk. A 2012 epidemiological study looked at atrazine, a commonly used herbicide in the U.S., and found that women who lived in counties in Texas with the highest levels of this chemical being used to treat agricultural crops were 80 times more likely to give birth to infants with choanal atresia or stenosis compared to women who lived in the counties with the lowest levels. Another epidemiological report in 2010 found even higher associations between increased incidents of choanal atresia and exposure to second-hand-smoke, coffee consumption, high maternal zinc and B-12 intake and exposure to anti-infective urinary tract medications.

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)

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.

The main diagnostic tools are blood tests, X-rays of the abdomen, CT scanning, and/or ultrasound. If a mass is identified, biopsy may determine the nature of the mass.

Radiological signs of bowel obstruction include bowel distension and the presence of multiple (more than six) gas-fluid levels on supine and erect abdominal radiographs.

Contrast enema or small bowel series or CT scan can be used to define the level of obstruction, whether the obstruction is partial or complete, and to help define the cause of the obstruction.

According to a meta-analysis of prospective studies by the Cochrane Collaboration, the appearance of water-soluble contrast in the cecum on an abdominal radiograph within 24 hours of oral administration predicts resolution of an adhesive small bowel obstruction with a pooled sensitivity of 97% and specificity of 96%.

Colonoscopy, small bowel investigation with ingested camera or push endoscopy, and laparoscopy are other diagnostic options.

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

Anal dilation, or stretching of the anal canal (Lord's operation), has fallen out of favour in recent years, primarily due to the unacceptably high incidence of fecal incontinence. In addition, anal stretching can increase the rate of flatus incontinence.

In the early 1990s, however, a repeatable method of anal dilation proved to be very effective and showed a very low incidence of side effects. Since then, at least one other controlled, randomized study has shown there to be little difference in healing rates and complications between controlled anal dilation and LIS, while another has again shown high success rates with anal dilation coupled with low incidence of side effects.

Identification of the exact causes usually begins with a thorough medical history, including detailed questioning about symptoms, bowel habits, diet, medication and other medical problems. Digital rectal examination is performed to assesses resting pressure and voluntary contraction (maximum squeeze) of the sphincter complex and puborectalis. Anal sphincter defects, rectal prolapse, and abnormal perineal descent may be detected. Anorectal physiology tests assess the functioning of the anorectal anatomy. Anorectal manometry records the pressure exerted by the anal sphincters and puborectalis during rest and during contraction. The procedure is also able to assess sensitivity of the anal canal and rectum. Anal electromyography tests for nerve damage, which is often associated with obstetric injury. Pudendal nerve terminal motor latency tests for damage to the pudendal motor nerves. Proctography, also known as defecography, shows how much stool the rectum can hold, how well the rectum holds it, and how well the rectum can evacuate the stool. It will also highlight defects in the structure of the rectum such as internal rectal intussusception. Dynamic pelvic MRI, also called MRI defecography is an alternative which is better for some problems but not as good for other problems. Proctosigmoidoscopy involves the insertion of an endoscope (a long, thin, flexible tube with a camera) into the anal canal, rectum and sigmoid colon. The procedure allows for visualization of the interior of the gut, and may detect signs of disease or other problems that could be a cause, such as inflammation, tumors, or scar tissue. Endoanal ultrasound, which some consider to be the gold standard for detection of anal canal lesions, evaluates the structure of the anal sphincters, and may detect occult sphincter tears that otherwise would go unseen.

Functional FI is common. The Rome process published diagnostic criteria for functional FI, which they defined as "recurrent uncontrolled passage of fecal material in an individual with a developmental age of at least 4 years". The diagnostic criteria are, one or more of the following factors present for the last 3 months: abnormal functioning of normally innervated and structurally intact muscles, minor abnormalities of sphincter structure/innervation (nerve supply), normal or disordered bowel habits, (i.e., fecal retention or diarrhea), and psychological causes. Furthermore, exclusion criteria are given. These are factors which all must be excluded for a diagnosis of functional FI, and are abnormal innervation caused by lesion(s) within the brain (e.g., dementia), spinal cord (at or below T12), or sacral nerve roots, or mixed lesions (e.g., multiple sclerosis), or as part of a generalized peripheral or autonomic neuropathy (e.g., due to diabetes), anal sphincter abnormalities associated with a multisystem disease (e.g., scleroderma), and structural or neurogenic abnormalities that are the major cause.

Physical examination can rule out anismus (by identifying another cause) but is not sufficient to diagnose anismus.