Master Intussusception with Picmonic for Physician Assistant

Telescoping of Bowel Segments is also known as intussusception and occurs when the intestine folds into itself and causes intestinal obstruction. It occurs most commonly at the ileocecal junction. Telescoping is most commonly idiopathic, but it can involve a lead point like Peyer Patch hypertrophy, Neoplasm or Meckels’ Diverticulum.

Intussusception is rare in adults and is typically due to a pathological lead point. A lead point is an area in which normal peristalsis gains traction to cause the bowel to invaginate. Intussusception in adults is typically caused by a lead point, but is only caused by a lead point 10% of the time in children. Lead points include the appendix, polyps, hyperplasia of Peyer’s Patches, Neoplasm, Meckels’ Diverticulum, but most cases overall do not involve a lead point.

Episodic abdominal pain is caused by the process of one segment of the bowel telescoping into another segment during intestinal peristalsis. While telescoping is most often idiopathic in nature, a Meckel diverticulum, viral infections, and the rotavirus vaccine can all cause lead points for telescoping. It is painful because this telescoping results in ischemia. The pain may cause the patients to pull their knees to their chest.

Patients are irritable and have diarrhea with intussusception, especially if associated with other intestinal pathologies.

On physical exam during palpation, these children can have a “sausage-shaped” mass, which is typically found in the right upper quadrant (RUQ). Furthermore, there is no fullness in the bowel, and there is an empty right lower quadrant (RLQ), otherwise known as “Dance’s sign.” On ultrasound, which is a reliable screening tool in low-risk patients, this mass may be seen as concentric echogenic bands formed by mucosa and muscularis alternating with hypoechoic bands formed by submucosa, otherwise described as “target sign, doughnut sign, or bull’s eye sign”.

With the telescoping that occurs in intussusception, arterial blood flow stops, leading to ischemia and pouring of mucus into the intestine. Venous engorgement also occurs, and together these processes form a mix of blood, mucus, and stool typically described as “red, currant jelly stools.”

Diagnosis of intussusception is typically made by CT or ultrasound after a clinical suspicion is established. Characteristic findings include the “Target Sign” when seen in the sagittal view, but will appear as a sausage in the coronal view. Usually ultrasound is done first and CT reserved for cases in which a pathological lead point can not be identified or an ultrasound is inconclusive.

Upon ultrasound or CT of a patient with intussusception, a picture that appears similar to a target will be seen in sagittal view (looking from the side). This picture represents layers of intestine inside intestine. The mass may be radiologically described as concentric echogenic bands formed by mucosa and muscularis alternating with hypoechoic bands formed by submucosa. Terms for this sign include “target sign, doughnut sign, or bull’s eye sign” .

The majority of cases of intussusception are in infants, typically between 6 and 36 months of age. 60% of cases are in individuals less than a year old, and 90% of cases are under 2 years old. Intussusception is uncommon in adults and is usually due to an intraluminal mass acting as a lead point in adults.

In patients with a history of intussusception the rotavirus vaccine is contraindicated. The rotavirus vaccine is usually administered at ages 2, 4 and 6 months. In patients with no history of intussusception the risk of severe gastroenteritis outweighs the risk of inducing intussusception.

A conservative management technique involves air or hydrostatic enema. An air enema is performed by instilling air into the colon via catheter until it becomes so full that the telescoped bowel is pushed back into a normal position. A hydrostatic enema can be performed by instilling a crystalloid solution into the bowel and has a similar effect. Barium enemas are typically avoided as they can cause peritonitis if bowel perforation occurs.

If other conservative treatments are unsuccessful, the child may require surgical intervention. Here, the invagination (telescoping) is manually reduced, and nonviable intestine is resected. This is typically done laparoscopically, but can be done using the open surgical approach if the patient has excessive adhesions.