A. Pathogenesis

1. Proximal bowel segment invaginates into the distal bowel segment at lead point
2. Intussusception leads to either partial or complete intestinal obstruction
3. Intestinal telescoping impairs venous blood return
4. The affected bowel may swell, become ischemic and necrotic and then perforate

B. Etiology

1. Requires a "lead point" abnormality of intestine
2. Two major classes of lead points
   1. Lymphoid hypertrophy
   2. Abnormal anatomy
3. Hypertrophy of lymphoid tissue
   1. Occurs in Peyer's patches or terminal ileum
   2. Usually following a viral infection
4. Associated with Anatomic Anomalies
   1. Meckel's diverticulum
   2. Intestinal polyp
   3. Lyphoma
   4. Foreign Body
   5. Adhesions (from prior abdominal surgery or inflammation)
5. Quadrivalent rotavirus vaccine (RotaShield®) increases risk of intussusception and has been withdrawn from the market in USA [3]
6. Intussusception in Adults [2]
   1. Uncommon
   2. Usually associated with extra-intestinal mass
   3. Malignant or benign tumors, abscess, or endometriosis may cause intussusception

C. Epidemiology

1. Peak incidence between 3 and 12 months of age
2. Affects 2% of children with more boys than girls
3. Ileocolic intussusception most common
4. Lead Points are Age Related
   1. Children < 18 months, the most common lead point is hypertrophied lymphoid tissue
   2. Older children are more likely to have specific anatomic lesions

D. Symptoms

1. Often preceded by viral gastroenteritis or upper respiratory infection
2. Crampy abdominal pain
3. Vomiting
4. Irritability then lethargy

E. Physical Examination

1. Palpable abdominal mass
2. Blood per rectum (currant jelly stool) as a late manifestation

F. Diagnosis

1. Abdominal Radiograph
   1. Showing paucity of gas in the right lower quadrant
   2. May also appear as intestinal obstruction
2. Barium enema shows a coiled spring appearing bowel wall at site of intussusception

G. Treatment

1. IV hydration and nasogastric suctioning
2. Hydrostatic Barium Enema Reduction
   1. Successful in 50% of cases
   2. Contraindicated with peritoneal free air
3. Air Insufflation
   1. Used if there is concern for unrecognized perforation
   2. This method will prevent contamination of the peritoneal cavity with barium
4. Surgical Correction
   1. Required with frank small bowel obstruction or peritonitis
   2. Used if unsuccessful hydrostatic reduction

References

1. Fleisher G. 1996. Synopsis of Pediatric Emergency Medicine , pp. 707
2. Berger DL and Mohammadkhani M. 2002. NEJM. 347(8):601 (Case Record)
3. Murphy TV, Gargiullo PM, Massoudi MS, et al. 2001. NEJM. 344(8):564