Emergency Medicine

Intussusception

When a segment of bowel is drawn into the next distal segment, severe pain and risk of intestinal obstruction result. The authors provide diagnostic, therapeutic, and prognostic keys to intussusception in both children and adults.

By Shaun C. Spalding, MD, and Bruce Evans, MD

What is intussusception and why is it medically important?

Intussusception is defined as the telescoping of one segment of bowel into the immediately distal segment of bowel. The proximal segment, or intussusceptum, is constricted by peristalsis and is carried by progressive smooth muscle contractions into the distal segment, or intussuscipiens. The intussusceptum, in some cases, can be the direct result of a lead point, characterized by an intraluminal, mural, or extraluminal process that acts as a focal area of traction, allowing one segment of intestine to move into the lumen of an adjacent segment. Classically, intussusception is created by an intraluminal mass that is pulled by peristaltic contractions into the adjacent bowel. More commonly, mural and extraluminal pathologies can create a situation in which a discrete area of the bowel wall does not contract properly or in synchronization with the adjacent or opposite bowel wall. The normally contracting bowel wall can then rotate and pull in the abnormal bowel wall to create a lead point, leading to intussusception.

Signs of obstruction. Scout film of the abdominal computed tomographic scan illustrating dilated loops of small bowel indicative of bowel obstruction. The small bowel is less dilated post nasogastric tube insertion.

Untreated intussusception will usually progress in one of two ways. The more common scenario is that the continued peristaltic contractions of the intussuscipiens will eventually occlude the lead point of the intussusceptum, creating an intestinal obstruction. The obstruction may be acute or chronic due to recurrence with spontaneous resolution. Rarely, the intussusceptum becomes strangulated, necrotic, and gangrenous, which can lead to peritonitis, sepsis, and death.

How common is intussusception?

Intussusception is most commonly encountered in children and has been reported to be the second most common abdominal emergency in this population, behind appendicitis. It accounts for 15% of all cases of bowel obstruction in children. After two years of age, the incidence of intussusception declines. Only 30% of all cases of intussusception occur in children older than two years of age. Also, boys are three times more likely than girls to develop intussusception.

Adult intussusception is relatively rare; 5% to 16% of all reported cases have occurred in adults. It is the etiology of only 1% of all cases of bowel obstruction in adults. Eisen and colleagues, in a retrospective evaluation over eleven years at the Mount Sinai Medical Center in New York City, found only 27 cases of intussusception aged 16 years and older. A review conducted by Karakousis spanning 13 years at the Roswell Park Memorial Institute in Buffalo, New York, found only 15 cases of documented intussusception in adult patients.

The mean age for intussusception in adults is 50 years of age. Incidence is about the same in males and females.

What areas of the GI tract can be involved in intussusception?

Intussusceptions can be categorized into three types: enteroenteric, colocolic, and enterocolic. Enteroenteric intussusceptions involve only the small intestine; they can be further categorized by specifying the involved segments of the small bowel. Colocolic intussusceptions develop only in the colon, sigmoid, and rectum. An enterocolic intussusception involves both the small and large bowel; this is the most common type of intussusception.

The most common of the enterocolic intussusceptions is the ileocolic type, which includes the ileum intussuscepting into the cecum and colon. The duodenum, stomach, and esophagus are rarely involved in intussusceptions because they are less mobile within the abdomen and because they are less redundant. There have also been reported cases of stomal intussusceptions involving ileostomies and colostomies. In a study involving 745 diagnosed intussusceptions, Brayton and colleagues reported that 6% of intussusceptions involved the stomach and duodenum with another 4% being stomal in origin.

What are the causes of intussusception?

The etiology of intussusception in children, in most cases, is unknown with failure to demonstrate the presence of a lead point. Nonidiopathic causes can be attributed to polyps, lipomas, Meckel's diverticulum, intestinal duplication, Henoch-Schönlein purpura, lymphomas, hypertrophied Peyer patches secondary to infection, adenovirus infection, foreign bodies, parasitic infestations, celiac disease, and cystic fibrosis. Previous abdominal surgery can predispose to the formation of adhesions and subsequent intussusceptions. Also, there were reports of an increased risk of intussusception in children receiving oral rotavirus immunization, especially in the weeks following its administration, which led to the drug being withdrawn from the market in 1999. With increasing age, the nonidiopathic causes tend to become more prevalent; more intussusceptions in children over the age of 6, for example, are due to lymphomas, compared with younger children.

Adult intussusception, on the other hand, will have a specific source in most cases. About 80% to 90% of intussusceptions in adults will have a lead point or a specific etiology. As many as two-thirds of pathologies detected as causes of adult intussusception are benign or malignant neoplasms. More than half of these neoplasms are malignant, occurring mostly in the large bowel. Only about 10% of cases are idiopathic.

With regard to location, intussusceptions involving the small bowel are usually associated with benign pathology, such as adhesions, lymphoid hyperplasia, trauma, lipomas, leiomyomas, and hemangiomas. Less common pathology includes malignant etiologies, with metastatic disease (most often from melanomas) being the cause of intussusception in the small bowel in most cases. Small bowel intussusceptions are idiopathic in 20% of cases.

In contrast, the colon is more likely to have a malignant lesion as the cause for intussusception. This has been attributed to the increased prevalence of malignancies in the colon versus the small bowel. In 50% to 60% of cases, colonic intussusception is associated with primary malignancies (such as adenocarcinoma and lymphoma), not metastatic disease, as is the case with small bowel lesions. Intussusceptions of the colon that are idiopathic account for only 5% to 10% of cases.

How does a patient with intussusception present?

In children, the presentation may depend on the age of the child and whether the bowel obstruction from the intussusception is complete or partial. With a complete obstruction, the child may present much earlier and not exhibit some of the later symptoms and physical findings. Generally, an otherwise healthy child will suddenly develop acute abdominal pain that may be accompanied by a drawing up of the knees, screaming, lethargy between painful bouts, and seizures.

In 90% of cases, diarrhea and vomiting quickly follow the onset of abdominal pain, with 50% of cases progressing to bloody, mucus bowel movements within 12 hours. The child may also have fever and abdominal tenderness and distension. Physical examination may reveal a palpable sausage-shaped mass in the mid-abdomen. In children older than 12 months, an intussusception may present as recurrent episodes of abdominal pain that goes away on its own. This may be due to the chronic nature of a recurrent intussusception that resolves spontaneously without intervention.

Intussusception in adults will present much like a small- or large-bowel obstruction. The patient may have subacute or chronic, nonlocalized, colicky abdominal pain with vomiting and loose stool or diarrhea. Bloody bowel movements may not develop. Fever may also be present, as well as abdominal distension and decreased appetite. Underlying medical conditions are more likely in adults and can interfere with a classic presentation. Patients with metastatic cancer throughout the abdomen, for example, may have baseline abdominal pain or no pain at all because of medications they are taking. Also, pancytopenia from immunosuppression or chemotherapeutic agents may prevent patients from developing a fever or may cause a septic-like presentation of sudden onset.

What diagnostic modalities are used to confirm the diagnosis of intussusception?

Plain abdominal radiographs can demonstrate the presence of dilated loops of bowel if an obstruction is present. They can also detect soft-tissue masses and sometimes an "air crescent" sign from air trapped between the bowel walls. Abdominal radiographs can exclude intussusceptions based on the presence of gas and stool in the sigmoid colon, although the sensitivity of this finding is low in children 5 years of age and younger. Abdominal radiographs can be useful in determining bowel gas and fluid distribution, but ultrasound and fluoroscopy, prior to contrast enemas, can provide the same information.

Contrast and pneumatic enemas are the diagnostic procedures of choice for children. The reason for this stems from the enemas' dual role in diagnosis and treatment. Water-soluble radiopaque agents as well as air are used for enemas to both diagnose and reduce the intussusception. Barium enema was the standard until the mid-1980s as ultrasound gained usefulness in the diagnosis of intussusceptions.

Ultrasound can be useful, especially when color Doppler is used. This test may help demonstrate the presence of bowel necrosis by showing compromised blood flow to the intussusceptum. Ultrasound has also been used to image the intussusception post-reduction, which can confirm a successful complete reduction. In addition, it may be used to detect a lead point in some pediatric cases. Ultrasound reduces unnecessary additional imaging and cost, can be used on reluctant children of all ages, and is fast and reliable. All of the above have given ultrasound increasing popularity as the diagnostic procedure of choice.

Computed tomography (CT) is generally the imaging modality of choice in adults. The images on CT are pathognomonic for intussusception. A CT scan may be of further advantage by providing clues to the etiology of the intussusception. The presence of lymphadenopathy or metastatic lesions, for example, may point to a malignant cause.

Magnetic resonance imaging has been used less frequently. This test does have the potential advantage of detecting evidence of necrosis by showing diminished bowel wall enhancement.

What are the treatment options for intussusception?

In children, the therapy of choice is reduction via barium enema, hydrostatics, or pneumatics. Although barium is generally used, water-soluble contrast agents have the advantage of not staining the peritoneum should a perforation occur. Pneumatic reduction has become increasingly popular as a clean, efficient technique. The use of air also allows for reduced radiation exposure compared to barium enemas. Pneumatic reduction involves pressurized air pumped into the rectum and colon via an insufflation device. Target pressures range between 80 and 120 mm Hg for successful reduction. Gorenstein and colleagues recommend up to two repeated pneumatic reductions in children. They repeated pneumatic reductions after 45 to 60 minutes; these intervals allowed the partially reduced intussusceptum's venous congestion and bowel wall edema to decrease.

Muscle relaxants and sedation have received mixed reviews with regard to their safety in children as well as their efficacy in aiding reduction efforts. Transabdominal manipulation has been reported to be of benefit, yet higher rates of reduction have been achieved without it. In children who have symptoms or diagnostic evidence of peritonitis or shock, reduction should be bypassed for surgical exploration and repair.

In adults, there has been some debate about the use of reduction as a first-line treatment. Because malignant neoplasms cause most adult intussusceptions, surgery is widely advocated as the procedure of choice. The presence of a mass as the lead point for adult intussusception makes it unlikely that a reduction will be successful. In enteroenteric intussusceptions, which involve more benign etiologies, preoperative reduction has been suggested. This allows for a smaller resection of bowel, but opponents believe that preoperative reduction may increase the risk of intraluminal seeding or venous embolization of malignant tumors, while unnecessarily increasing the risk of perforation in the presence of bowel ischemia.

What is the patient's prognosis?

The prognosis depends on how long the patient had the intussusception prior to treatment, whether or not complications develop during or after treatment, and the presence of comorbidities. With barium enema or pneumatic reduction of an intussusception, perforation of the bowel wall may occur. In several studies investigating the success of pneumatic reduction, 2.8% was the highest reported incidence of perforation, with several reports under 1%. Regardless of the technique used, the incidence of perforation was greater in patients with a longer duration of symptoms, which can predispose to necrosis. Reduction of necrotic bowel may lead to sepsis and shock after cytokines and endotoxins in the bowel wall are released with alleviation of venous congestion.

Surgical resection of intussusception, as with any procedure, can lead to complications inherent in the procedure itself. However, surgery has been associated with a lower rate of recurrence compared to pneumatic reduction.

The success of pneumatic reduction is inversely proportional to the duration of the intussusception. In two separate studies by Stein and Gorenstein, the success rate of pneumatic reduction of an intussusception dropped substantially after 48 hours from the onset of symptoms.

Patients with comorbidities usually have a prognosis that is dependent on their underlying conditions and the stages of those conditions. Intussusception encountered in a patient with cancer can be treated with equal success as in a patient without cancer. However, the prognosis of the patient with cancer will depend on his or her susceptibility to infection and recurrence, which in turn hinges on the type of cancer, the type of therapy, and the presence of metastatic lesions acting as lead points.

The mortality rate with all treatments is 1% to 2%. Recurrence rates can range from 5% to 20% depending on the reduction technique used. The overall recurrence rate of an intussusception after pneumatic reduction is 3% to 4% in the 24-hour period following the reduction procedure. Recurrent intussusceptions occur in 10% of all children who had an initially successful reduction, regardless of the reduction technique used.

Recurrence is not necessarily an indication for surgery. Rather, each recurrence should be handled as if it were the first episode, provided that each previous reduction was successful.