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.

The different types of intestinal atresia are named after their location:

- Duodenal atresia – malformation of the duodenum, part of the intestine that empties from the stomach

- Jejunal atresia – malformation of the jejunum, the second part of the intestine extending from the duodenum to the ileum

- Ileal atresia – malformation of the ileum, the lower part of the small intestine

- Colon atresia – malformation of the colon

Duodenal atresia has a strong association with Down syndrome. It is the most common type, followed by ileal atresia.

An inherited form – familial multiple intestinal atresia – has also been described. This disorder was first reported in 1971. It is due to a mutation in the gene TTC7A on short arm of chromosome 2 (2p16). It is inherited as an autosomal recessive gene and is usually fatal in infancy.

With early intervention, morbidity and mortality of cases of intestinal obstruction is low. The outcome is in part dependent upon congenital comorbidities and delays in diagnosis and management.

The exact causes are not known. It is not associated with a particular gene, but there is some evidence of recurrence in families.

According to a 1984 study conducted in Maryland, Hirschsprung's disease appears in 18.6 per 100,000 live births. In Japan, it occurs at a similar rate of about one in 5,000 births (20 per 100,000). It is more common in male than female (4.32:1) and in white rather than nonwhite. Nine percent of the Hirschsprung cases were also diagnosed as having Down syndrome. Most cases are diagnosed before the patient is 10 years of age.

The prognosis for non-ischemic cases of SBO is good with mortality rates of 3–5%, while prognosis for SBO with ischemia is fair with mortality rates as high as 30%.

Cases of SBO related to cancer are more complicated and require additional intervention to address the malignancy, recurrence, and metastasis, and thus are associated with poorer prognosis.

All cases of abdominal surgical intervention are associated with increased risk of future small-bowel obstructions. Statistics from U.S. healthcare report 18.1% re-admittance rate within 30 days for patients who undergo SBO surgery. More than 90% of patients also form adhesions after major abdominal surgery.

Common consequences of these adhesions include small-bowel obstruction, chronic abdominal pain, pelvic pain, and infertility.

This can lead to a number of disease manifestations such as:

- Acute midgut volvulus

- Chronic midgut volvulus

- Acute duodenal obstruction

- Chronic duodenal obstruction

- Internal herniation

- Superior mesenteric artery syndrome

The disorder may occur by itself or in association with other genetic disorders such as Down syndrome. About half of isolated cases are linked to a specific genetic mutation and about 20% occur within families. Some of these occur in an autosomal dominant manner. The cause of the remaining cases is unclear. If otherwise normal parents have one child with the condition, the next child has a 4% risk of being affected.

The condition is diagnosed most often in infancy and early childhood. It strikes about 2,000 infants (one in every 1,900) in the United States in the first year of life. Its incidence begins to rise at about one to five months of life, peaks at four to nine months of age, and then gradually declines at around 18 months.

Intussusception occurs more frequently in boys than in girls, with a ratio of approximately 3:1.

In adults, intussusception represents the cause of approximately 1% of bowel obstructions and is frequently associated with neoplasm, malignant or otherwise.

Fetal and neonatal bowel obstructions are often caused by an intestinal atresia, where there is a narrowing or absence of a part of the intestine. These atresias are often discovered before birth via an ultrasound, and treated with using laparotomy after birth. If the area affected is small, then 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 a period of time, a temporary stoma may be placed.

Causes of intussusception are not clearly established or understood. About 90% of cases of intussusception in children arise from an unknown cause. They can include infections, anatomical factors, and altered motility.

- Meckel's diverticulum

- Polyp

- Duplication

- Appendix

- Hyperplasia of Peyer's patches

- Idiopathic

An earlier version of the rotavirus vaccine that is no longer used was linked to intussusception, but the current versions are not clearly linked. Due to a potential risk, they are thus not recommended in babies who have had intussusception.

Blind loop syndrome is a complication of surgical operations of the abdomen, as well as inflammatory bowel disease or scleroderma. Another cause is jejunoileal diverticula.

The diagnosis is suspected based on polyhydramnios in uteru, bilious vomiting, failure to pass meconium in the first day of life, and abdominal distension. The presentations of NBO may vary. It may be subtle and easily overlooked on physical examination or can involve massive abdominal distension, respiratory distress and cardiovascular collapse. Unlike older children, neonates with unrecognized intestinal obstruction deteriorate rapidly.

The causes of diverticulitis are poorly understood, with approximately 40 percent due to genes and 60 percent due to environmental factors. Conditions that increase the risk of developing diverticulitis include arterial hypertension and immunosuppression. Obesity is another risk factor.

There is no cure for short bowel syndrome except transplant. In newborn infants, the 4-year survival rate on parenteral nutrition is approximately 70%. In newborn infants with less than 10% of expected intestinal length, 5 year survival is approximately 20%. Some studies suggest that much of the mortality is due to a complication of the total parenteral nutrition (TPN), especially chronic liver disease. Much hope is vested in Omegaven, a type of lipid TPN feed, in which recent case reports suggest the risk of liver disease is much lower.

Although promising, small intestine transplant has a mixed success rate, with postoperative mortality rate of up to 30%. One-year and 4-year survival rate are 90% and 60%, respectively.

Typical recovery from NEC if medical, non-surgical treatment succeeds, includes 10–14 days or more without oral intake and then demonstrated ability to resume feedings and gain weight. Recovery from NEC alone may be compromised by co-morbid conditions that frequently accompany prematurity. Long-term complications of medical NEC include bowel obstruction and anemia.

In the United States it caused 355 deaths per 100,000 live births in 2013, down from 484 per 100,000 live births in 2009. Rates of death were almost three times higher for the black populations than for the white populations.

Overall, about 70-80% of infants who develop NEC survive. Medical management of NEC shows an increased chance of survival compared to surgical management. Despite a significant mortality risk, long-term prognosis for infants undergoing NEC surgery is improving, with survival rates of 70–80%. "Surgical NEC" survivors are at risk for complications including short bowel syndrome and neurodevelopmental disability.

These hernias should be repaired because of the high risk of strangulation; fortunately, surgery is straightforward, with only larger defects requiring a mesh prosthesis. Varied Spigelian hernia mesh repair techniques have been described, although evidence suggests laparoscopy results in less morbidity and shorter hospitalization compared with open procedures. Mesh-free laparoscopic suture repair is feasible and safe. This novel uncomplicated approach to small Spigelian hernias combines the benefits of laparoscopic localization, reduction, and closure without the morbidity and cost associated with foreign material.

Laparotomy for other forms of volvulus, especially anal volvulus.

It is unclear what role dietary fibre plays in diverticulitis. It is often stated that a diet low in fibre is a risk factor; however, the evidence to support this is unclear. There is no evidence to suggest that the avoidance of nuts and seeds prevents the progression of diverticulosis to an acute case of diverticulitis. It appears in fact that a higher intake of nuts and corn could help to avoid diverticulitis in adult males.

An ileosigmoid knot is a form of volvulus in which ileum wraps around the base of the sigmoid and passes beneath itself forming a knot.

The exact cause of this condition is not known. Patients usually present with clinical features of colonic obstruction. Vomiting, abdominal distension, abdominal pain, blood stained stools are frequent symptoms. It is difficult to diagnose this condition before surgery. Raveenthiran described a triad which may be useful in preoperative diagnosis. The triad includes 1). Clinical features suggestive of small bowel obstruction, 2). Radiological features suggestive of large bowel obstruction, 3). Inability to negotiate sigmoidoscope or a flatus tube. This is a surgical emergency that requires urgent resection of gangrenous bowel and untwisting of the volvulus.

The overgrowth of bacteria in the small intestine is prevented by various mechanical and chemical factors which include the constant peristaltic movement of contents along the length of the gastrointestinal tract and the antibacterial properties of gastric secretions, pancreatic secretions and bile.

It follows that a disruption of any of these factors could lead to bacterial overgrowth and indeed BLS has been found to occur in persons with anatomical anomalies that result in stagnation. BLS has also been associated with achlorhydria, dysmotility, fistulae, and strictures. Chronic or high dose opioid therapy may contribute to BLS by reducing gastric motility.

Due to the disruption of digestive processes by the overgrowth of intestinal bacteria malabsorption of bile salts, fat and fat-soluble vitamins, protein and carbohydrates results in damage to the mucosal lining of the intestine by bacteria or via the production of toxic metabolites.

Short bowel syndrome in adults and children is usually caused by surgery. This surgery may be done for:

- Crohn's disease, an inflammatory disorder of the digestive tract

- Volvulus, a spontaneous twisting of the small intestine that cuts off the blood supply and leads to tissue death

- Tumors of the small intestine

- Injury or trauma to the small intestine

- Necrotizing enterocolitis (premature newborn)

- Bypass surgery to treat obesity

- Surgery to remove diseases or damaged portion of the small intestine

Some children are also born with an abnormally short small intestine, known as congenital short bowel.

In a cecal volvulus, the cecum may be returned to a normal position and sutured in place, a procedure known as cecopexy. If identified early, before presumed intestinal wall ischemia has resulted in tissue breakdown and necrosis, the cecal volvulus can be detorsed laparoscopically.

A Spigelian hernia (or lateral ventral hernia) is a hernia through the Spigelian fascia, which is the aponeurotic layer between the rectus abdominis muscle medially, and the semilunar line laterally. These are generally interparietal hernias, meaning that they do not lie below the subcutaneous fat but penetrate between the muscles of the abdominal wall; therefore, there is often no notable swelling.

Spigelian hernias are usually small and therefore risk of strangulation is high. Most occur on the right side. (4th–7th decade of life.) Compared to other types of hernias they are rare.

Most patients will develop flat, brownish spots (melanotic macules) on the skin, especially on the lips and oral mucosa, during the first year of life, and a patient’s first bowel obstruction due to intussusception usually occurs between the ages of six and 18 years. The cumulative lifetime cancer risk begins to rise in middle age. Cumulative risks by age 70 for all cancers, gastrointestinal (GI) cancers, and pancreatic cancer are 85%, 57%, and 11%, respectively.

A 2011 Dutch study followed 133 patients for 14 years. The cumulative risk for cancer was 40% and 76% at ages 40 and 70, respectively. 42 (32%) of the patients died during the study, of which 28 (67%) were cancer related. They died at a median age of 45. Mortality was increased compared with the general population.

A family with sinonasal polyposis were followed up for 28 years. Two cases of sinonasal type adenocarcinoma developed. This is a rare cancer. This report suggested that follow up of sinus polyps in this syndrome may be indicated.