Intussusception

Intussusception refers to a condition in which a segment of the intestine invaginates into the adjacent intestinal lumen, causing obstruction of intestinal contents. Intussusception accounts for 15%-20% of intestinal obstructions. Clinically, acute intussusception is common, while chronic intussusception is generally secondary. Acute intussusception is a disease unique to infancy, most commonly seen in infants aged 4-10 months, with incidence decreasing year by year after 2 years of age. The male-to-female ratio is 2-3:1. The vast majority of intussusceptions involve the proximal bowel invaginating into the distal bowel; retrograde intussusception is rare, accounting for less than 10% of total cases. On longitudinal section, intussusception generally has three layers: the outer layer is the sheath or outer cylinder of the intussusception, and the invaginated portion consists of the inner and middle cylinders. The farthest point of invagination is the head or apex, and the point where the bowel enters from outside is the neck. Intussusception is mostly antegrade, consistent with the direction of peristalsis. After intussusception occurs, the invaginated portion advances continuously with peristalsis, and this segment of bowel along with its mesentery is also drawn into the sheath, with the neck constricting it so that it cannot automatically reduce. Intussusception occurs throughout the year, with the highest incidence in late spring and early summer, possibly related to upper respiratory tract infections and lymph node viral infections.