Chronic intestinal pseudo-obstruction comprises a group of disorders characterized by signs and symptoms of intestinal obstruction in the absence of an anatomic lesion. Pseudo-obstruction can occur as a primary disease or be secondary to a large number of conditions that can transiently or permanently alter bowel motility. Pseudo-obstruction represents a wide spectrum of pathologic disorders from abnormal myoelectric activity to abnormalities of the nerves (intestinal neuropathy) or musculature (intestinal myopathy) of the gut. The organs involved can include the entire gastrointestinal tract or be limited to certain components, such as the stomach or colon. The distinctive pathologic abnormalities are considered together because of their clinical similarities.

Most congenital forms of pseudo-obstruction occur sporadically. A few clusters of autosomal dominant or recessive patients have been reported as having cases associated with abnormal gut muscle or nerves. Patients with autosomal dominant forms of pseudo-obstruction have variable expressions of the disease. Acquired pseudo-obstruction can follow episodes of acute gastroenteritis, presumably resulting in injury to the myenteric plexus.

In congenital pseudo-obstruction, abnormalities of the muscle or nerves can be demonstrated in most cases. In muscular disease, the outer longitudinal muscle layer is replaced by fibrous material. In neuronal disease, there may be disorganized ganglia, hypoganglionosis, or hyperganglionosis. Abnormalities in the interstitial cells of Cajal (potential gut pacemaker) have been demonstrated in some children and mitochondrial defects have been found in others. Genetic defects have been identified in the transcription factor SOX10, the DNA polymerase gamma gene (POLG), and a locus on chromosome 8.

Constipation is defined by a delay or difficulty in defecation present for 2 weeks or longer and significant to cause distress to the patient. Another approach to the definition is noted in Table 324-2. Functional constipation, also known as idiopathic constipation or fecal withholding, can usually be differentiated from constipation secondary to organic causes on the basis of a history and physical examination (Chapter 21.4). Unlike anorectal malformations and Hirschsprung disease, functional constipation typically starts after the neonatal period. Usually, there is an intentional or subconscious withholding of stool. An acute episode usually precedes the chronic course. The acute episode may be a dietary change from human milk to cow’s milk, secondary to the change in protein:carbohydrate ratio or an allergy to cow’s milk. The stool becomes firm, smaller, and difficult to pass, resulting in anal irritation and often an anal fissure. In toddlers, coercive or inappropriately early toilet training is a factor that can initiate a pattern of stool retention. In older children, retentive constipation can develop after entering a situation that makes stooling inconvenient such as school. Because the passage of bowel movements is painful, voluntary withholding of feces to avoid the painful stimulus develops.