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.

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.

Biliary atresia seems to affect females slightly more often than males, and Asians and African Americans more often than Caucasians. It is common for only one child in a pair of twins or within the same family to have the condition. There seems to be no link to medications or immunizations given immediately before or during pregnancy. Diabetes during pregnancy particularly during the first trimester seems to predispose to a number of distinct congenital abnormalities in the infant such as sacral agenesis and the syndromic form of biliary atresia.

Assisted reproductive technology (ART) is a general term referring to methods used to achieve pregnancy by artificial or partially artificial means. According to the CDC, in general, ART procedures involve surgically removing eggs from a woman's ovaries, combining them with sperm in the laboratory, and returning them to the woman's body or donating them to another woman. ART has been associated with epigenetic syndromes, specifically BWS and Angelman syndrome. Three groups have shown an increased rate of ART conception in children with BWS. A retrospective case control study from Australia found a 1 in 4000 risk of BWS in their in-vitro population, several times higher than the general population. Another study found that children conceived by in vitro fertilisation (IVF) are three to four times more likely to develop the condition. No specific type of ART has been more closely associated with BWS. The mechanism by which ART produces this effect is still under investigation.

Beckwith–Wiedemann syndrome has an estimated incidence of one in 13,700; about 300 children with BWS are born each year in the United States. The exact incidence of BWS is unknown because of the marked variability in the syndrome's presentation and difficulties with diagnosis. The number of reported infants born with BWS is most likely low because many are born with BWS, but have clinical features that are less prominent and therefore missed. BWS has been documented in a variety of ethnic groups and occurs equally in males and females.

Children conceived through In vitro fertilization have a three to fourfold increased chance of developing Beckwith–Wiedemann syndrome. It is thought that this is due to genes being turned on or off by the IVF procedures.

Fundic gland polyps are found in 0.8 to 1.9% of patients who undergo esophagogastroduodenoscopy, and are more common in middle aged women.

The most important consideration in evaluating patients with FGPs is distinguishing between sporadic form (patients without any other gastrointestinal condition, usually in middle age with female prevalence) and syndromic form. This is to ascertain the risk of development of gastric cancer, and to ascertain the risk of concomitant colon cancer.

FGPs can be found in association with the following genetic conditions:

- familial adenomatous polyposis

- attenuated familial adenomatous polyposis syndromes

- Zollinger-Ellison syndrome

- gastric adenocarcinoma associated with proxymal polyposis of the stomach (GAPPS): this condition, described in three families is characterized by development of antral adenomas and FGPs, with early development of severe dysplasia and gastric cancer, in absence of overt intestinal polyposis. This condition has been recently characterized by a point mutation in exon 1B of APC gene.

Sporadic FGPs have been associated with:

- chronic use of proton pump inhibitors (proposed by some authors, denied by others)

- "Helicobacter pylori" infection: there is a reverse relationship between infection and fundic gland polyps, and infection by "H pylori" causes polyps regression.

There is a risk of development of cancer with fundic gland polyposis, but it varies based on the underlying cause of the polyposis. The risk is highest with congenital polyposis syndromes, and is lowest in acquired causes. As a result, it is recommended that patients with multiple fundic polyps have a colonoscopy to evaluate the colon. If there are polyps seen on colonoscopy, genetic testing and testing of family members is recommended.

In the gastric adenocarcinoma associated with proximal polyposis of the stomach (GAPPS), there is a high risk of early development of proximal gastric adenocarcinoma.

It is still unclear which patients would benefit with surveillance gastroscopy, but most physicians recommend endoscopy every one to three years to survey polyps for dysplasia or cancer. In the event of high grade dysplasia, polypectomy, which is done through the endoscopy, or partial gastrectomy may be recommended. One study showed the benefit of NSAID therapy in regression of gastric polyps, but the efficacy of this strategy (given the side effects of NSAIDs) is still dubious.

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.

Anomalies between the diverticulum and umbilicus may include the presence of fibrous cord, cyst, fistula or sinus, leading to:

- Infection or excoriation of periumbilical skin, resulting in a discharging sinus

- Recurrent infection and healing of sinus

- Abscess formation in the abdominal wall

- Fibrous cord increases the risk of volvulus formation and internal herniation

Symptoms: Vomiting, abdominal pain and severe or complete constipation.

- The vitelline vessels remnant that connects the diverticulum to the umbilicus may form a fibrous or twisting band (volvulus), trapping the small intestine and causing obstruction. Localised periumbilical pain may be experienced in the right lower quadrant (like appendicitis).

- "Incarceration": when a Meckel's diverticulum is constricted in an inguinal hernia, forming a Littré hernia that obstructs the intestine.

- Chronic diverticulitis causing stricture

- Strangulation of the diverticulum in the obturator foramen.

- Tumors e.g. carcinoma: direct spread of an adenocarcinoma arising in the diverticulum may lead to obstruction

- Lithiasis, stones that are formed in Meckel's diverticulum can:

1. Extrude into the terminal ileum, leading to obstruction

2. Induce local inflammation and intussusception.

- The diverticulum itself or tumour within it may cause intussusception. For example, from the ileum to the colon, causing obstruction. Symptoms of this include "currant jelly" stools and a palpable lump in the lower abdomen. This occurs when the diverticulum inverts into the lumen of the ileum, due to either:

1. An "active" peristaltic mechanism of the diverticulum that attempts to remove irritating factors

2. A "passive" process such as the transit of food

Prognosis varies widely depending on severity of symptoms, degree of intellectual impairment, and associated complications. Because the syndrome is rare and so newly identified, there are no long term studies.

Most (>95%) infants with biliary atresia will undergo an operation designed to retain and salvage the native liver, restore bile flow and reduce the level of jaundice. This is known as the Kasai procedure (after Morio Kasai, the Japanese surgeon who first developed the technique) or hepatoportoenterostomy. Although the procedure is not thought of as curative, it may relieve jaundice, and stop liver fibrosis allowing normal growth and development. Published series from Japan, North America and the UK show that bilirubin levels will fall to normal values in about 50-55% of infants allowing 40-50% to retain their own liver to reach the age of 5 and 10 years (and beyond). Liver transplantation is an option for those children whose liver function and symptoms fail to respond to a Kasai operation.

Recent large-scale studies by Davenport et al. ("Annals of Surgery", 2008) show that the age of the patient is not an absolute clinical factor affecting prognosis. The influence of age differs according to the disease etiology—i.e., whether biliary atresia is isolated, cystic (CBA), or accompanied by splenic malformation (BASM).

It is widely accepted that corticosteroid treatment after a Kasai operation, with or without choleretics and antibiotics, has a beneficial effect on postoperative bile flow and can clear jaundice, but the dosing and duration of the ideal steroid protocol are controversial. Furthermore, it has been observed in many retrospective longitudinal studies that corticosteroid treatment does not prolong survival of the native liver or transplant-free survival. Davenport et al. also showed ("Hepatology" 2007) that short-term, low-dose steroid therapy following a Kasai operation had no effect on the mid- or long-term prognosis of biliary atresia patients.

Genetic counseling for VWS involves discussion of disease transmission in the autosomal dominant manner and possibilities for penetrance and expression in offspring. Autosomal dominance means affected parents have a 50% chance of passing on their mutated "IRF6" allele to a their child. Furthermore, if a cleft patient has lip pits, he or she has a ten times greater risk of having a child with cleft lip with or without cleft palate than a cleft patient who does not have lip pits. Types of clefting between parents and affected children are significantly associated; however, different types of clefts may occur horizontally and vertically within the same pedigree. In cases where clefting is the only symptom, a complete family history must be taken to ensure the patient does not have non-syndromic clefting.

Recent research has found that Dandy–Walker syndrome often occurs in patients with PHACES syndrome.

Mosaic mutations in PIK3CA have been found to be the genetic cause of M-CM. Genetic testing for the mutation is currently only available on a research basis. Other overgrowth conditions with distinct phenotypes have also been found to be caused by mosaic mutations in PIK3CA. How different mutations in this gene result in a variety of defined clinical syndromes is still being clarified. Mutations in PIK3CA have not been found in a non-mosaic state in any of these disorders, so it is unlikely that the conditions could be inherited.

a combination of various vascular malformations. They are 'complex' because they involve a combination of two different types of vessels.

- CVM: capillary venous malformation

- CLM: capillary lymphatic malformation

- LVM: lymphatic venous malformation

- CLVM: capillary lymphatic venous malformation. CLVM is associated with Klippel-Trenaunay syndrome

- AVM-LM: Arteriovenous malformation- lymphatic malformation

- CM-AVM: capillary malformation- arteriovenous malformation

Until recently, the medical literature did not indicate a connection among many genetic disorders, both genetic syndromes and genetic diseases, that are now being found to be related. As a result of new genetic research, some of these are, in fact, highly related in their root cause (genotype) despite the widely varying set of medical characteristics (phenotype) that are clinically visible in the disorders. Dandy–Walker syndrome is one such disease, part of an emerging class of diseases called ciliopathies. The underlying cause may be a dysfunctional molecular mechanism in the primary cilia structures of the cell, organelles which are present in many cellular types throughout the human body. The cilia defects adversely affect "numerous critical developmental signaling pathways" essential to cellular development and thus offer a plausible hypothesis for the often multi-symptom nature of a large set of syndromes and diseases. Known ciliopathies include primary ciliary dyskinesia, Bardet-Biedl syndrome, polycystic kidney and liver disease, nephronophthisis, Alstrom syndrome, Meckel-Gruber syndrome and some forms of retinal degeneration.

Genetic associations of the condition are being investigated.

A few studies have worked on providing details related to the outlook of disease progression. Two studies show that each year 0.5% of people who have never had bleeding from their brain cavernoma, but had symptoms of seizures, were affected by bleeding. In contrast, patients who have had bleeding from their brain cavernoma in the past had a higher risk of being affected by subsequent bleeding. The statistics for this are very broad, ranging from 4%-23% a year. Additional studies suggest that women and patients under the age of 40 are at higher risk of bleeding, but similar conducted studies did not reach the same conclusion. However, when cavernous hemangiomas are completely excised, there is very little risk of growth or rebleeding. In terms of life expectancy, not enough data has been collected on patients with this malformation in order to provide a representative statistical analysis.

Lip pits may be surgically removed either for aesthetic reasons or discomfort due to inflammation caused by bacterial infections or chronic saliva excretion, though spontaneous shrinkage of the lip pits has occurred in some rare cases. Chronic inflammation has also been reported to cause squamous-cell carcinoma. It is essential to completely remove the entire lip pit canal, as mucoid cysts can develop if mucous glands are not removed. A possible side effect of removing the lip pits is a loose lip muscle. Other conditions associated with VWS, including CL, CP, congenital heart defects, etc. are surgically corrected or otherwise treated as they would be if they were non-syndromic.

Ileus is a cause of colic in horses due to functional obstruction of the intestines. It most commonly seen in horses postoperatively, especially following colic surgery. Horses experiencing ileus are at risk for gastric rupture due to rapid reflux build-up, and require intense medical management with frequent nasogastric intubation. Ileus may increase adhesion formation, because intestinal segments have more prolonged contact and intestinal distention causes serosal injury and ischemia. It is usually treated with aggressive fluid support, prokinetics, and anti-inflammatories.

Venous malformation is a subtype of vascular malformation affecting the venous vasculature. They are usually congenital and found at birth and are treated by Schlerotherapy or Laser Therapy.

The prevalence of congenital Chiari I malformation, defined as tonsilar herniations of 3 to 5 mm or greater, was previously believed to be in the range of one per 1000 births, but is likely much higher. Women are three times more likely than men to have a congenital Chiari malformation. Type II malformations are more prevalent in people of Celtic descent. A study using upright MRI found cerebellar tonsillar ectopia in 23% of adults with headache from motor-vehicle-accident head trauma. Upright MRI was more than twice as sensitive as standard MRI, likely because gravity affects cerebellar position.

Cases of congenital Chiari malformation may be explained by evolutionary and genetic factors. Typically, an infant's brain weighs around 400g at birth and triples to 1100-1400g by age 11. At the same time the cranium triples in volume from 500 cm to 1500 cm to accommodate the growing brain. During human evolution, the skull underwent numerous changes to accommodate the growing brain. The evolutionary changes included increased size and shape of the skull, decreased basal angle and basicranial length. These modifications resulted in significant reduction of the size of the posterior fossa in modern humans. In normal adults, the posterior fossa comprises 27% of the total intracranial space, while in adults with Chiari Type I, it is only 21%. If a modern brain is paired with a less modern skull, the posterior fossa may be too small, so that the only place where the cerebellum can expand is the foramen magnum, leading to development of Chiari Type I. H. neanderthalensis had platycephalic (flattened) skull. Some cases of Chiari are associated with platybasia (flattening of the skull base).

All fast-flow malformations are malformations involving arteries. They constitute about 14% of all vascular malformations.

- Arterial malformation

- Arteriovenous fistula (AVF) : a lesion with a direct communication via fistulae between an artery and a vein.

- Arteriovenous malformation : a lesion with a direct connection between an artery and a vein, without an intervening capillary bed, but with an interposed nidus of dysplastic vascular channels in between.

The most widely accepted pathophysiological mechanism by which Chiari type I malformations occur is by a reduction or lack of development of the posterior fossa as a result of congenital or acquired disorders. Congenital causes include hydrocephalus, craniosynostosis (especially of the lambdoid suture), hyperostosis (such as craniometaphyseal dysplasia, osteopetrosis, erythroid hyperplasia), X-linked vitamin D-resistant rickets, and neurofibromatosis type I. Acquired disorders include space occupying lesions due to one of several potential causes ranging from brain tumors to hematomas.

Head trauma may cause cerebellar tonsillar ectopia, possibly because of dural strain. Additionally, ectopia may be present but asymptomatic until whiplash causes it to become symptomatic. Posterior fossa hypoplasia causes reduced cerebral and spinal compliance.

In most cases, a fetus with CPAM is closely monitored during pregnancy and the CPAM is removed via surgery after birth. Most babies with a CPAM are born without complication and are monitored during the first few months. Many patients have surgery, typically before their first birthday, because of the risk of recurrent lung infections associated with CPAMs. Some pediatric surgeons can safely remove these lesions using very tiny incisions using minimally invasive surgical techniques (thoracoscopy). However, some CPAM patients live a full life without any complication or incident. It is hypothesized that there are thousands of people living with an undetected CPAM. Through ultrasound testing employed in recent years, many more patients are aware that they live with this condition. Rarely, long standing CPAMs have been reported to become cancerous.

Very large cystic masses might pose a danger during birth because of the airway compression. In this situation, a special surgical type of delivery called the EXIT procedure may be used.

In rare extreme cases, where fetus's heart is in danger, fetal surgery can be performed to remove the CPAM. If non-immune hydrops fetalis develop, there is a near universal mortality of the fetus without intervention. Fetal surgery can improve the chances of survival to 50-60%. Recently, several studies found that a single course of prenatal steroids (betamethasone) may increase survival in hydropic fetuses with microcystic CPAMs to 75-100%. These studies indicate that large microcystic lesions may be treated prenatally without surgical intervention. Large macrocyst lesions may require in utero placement of a Harrison thoracoamniotic shunt.