Intussusception occurs when one segment of the intestine telescopes into an adjacent segment, similar to the collapse of a telescope. This action causes the inner portion of the bowel, known as the intussusceptum, to slide into the outer portion, or intussuscipiens. This telescoping can lead to intestinal obstruction and compress the blood supply, potentially causing ischemia and tissue death. While this is the most common cause of intestinal obstruction in young children, it is significantly rarer in adults. Adult intussusception accounts for only about 5% of all cases and a small fraction of adult bowel obstructions.
What Is Intussusception and Its Rarity in Adults
The mechanism involves abnormal peristaltic movement, where wave-like contractions pull a segment of the bowel into the next. Intussusception is classified anatomically based on the segments involved: enteroenteric (small bowel), colocolic (large bowel), or ileocolic (small bowel into large bowel). The distinction between adult and pediatric cases centers on the cause. In children, the cause is often unknown, or idiopathic, in up to 90% of cases.
In contrast, nearly 90% of adult intussusception cases are secondary to an identifiable pathological condition. This structural abnormality is termed a “lead point,” which is a mass or lesion that the bowel’s contractions attempt to push forward, pulling the intestinal wall along with it. Adult intussusception is often a symptom of a more serious, pre-existing disease. The presence of a lead point dictates a different approach to diagnosis and treatment compared to children.
Specific Causes: Identifying the Adult Lead Point
The cause of adult intussusception is the presence of a pathological lead point, most frequently a tumor or mass. Neoplastic causes are responsible for over half of all adult cases, making the risk of malignancy a primary concern. The type of lesion depends on the location within the digestive tract.
In the small intestine, intussusception is more common, and the lead points are generally benign in 50% to 75% of cases. Benign lesions include lipomas, leiomyomas, and various polyps. Malignant causes, accounting for up to 30% of cases, are often metastatic tumors that have spread from a primary site. Conversely, intussusception in the large intestine (colocolic type) is much more likely to be malignant.
Malignancy is found in up to 66% of colonic intussusception cases, with adenocarcinoma being the most common type. Non-neoplastic causes are less frequent but include inflammatory bowel diseases, such as Crohn’s disease, which cause bowel wall thickening. Other triggers involve postsurgical adhesions, vascular malformations, and congenital abnormalities like Meckel’s diverticulum.
Recognizing Symptoms and Diagnostic Procedures
Diagnosing intussusception in adults is challenging because symptoms are often chronic or intermittent. Unlike the acute presentation seen in children, adult patients commonly experience vague abdominal pain that comes and goes over weeks or months. Other symptoms include nausea, vomiting, a change in bowel habits, and occasionally gastrointestinal bleeding. The intermittent nature of the symptoms often leads to a delayed diagnosis, as the condition can mimic other abdominal issues.
The gold standard for confirming the diagnosis is a computed tomography (CT) scan of the abdomen. CT imaging provides a high-resolution view effective for visualizing the characteristic signs of intussusception. The pathognomonic finding is often described as a “target sign” or “sausage-shaped mass,” representing the bowel-within-bowel configuration. CT is also crucial for locating the lead point and determining the extent of any potential bowel obstruction or ischemia.
Treatment and Management Strategies
The definitive management for adult intussusception is almost always surgical intervention. This approach is necessitated by the high probability of finding a pathological lead point, particularly the significant risk of an underlying malignancy. Non-operative methods, such as pneumatic or hydrostatic reduction used in children, are generally avoided in adults. Attempting to manually reduce the telescoping segment risks perforation, especially if the tissue is compromised by ischemia or a rigid tumor.
The standard procedure involves surgical resection, which is the complete removal of the affected segment of the bowel and the lead point. For colonic intussusception, resection is performed without reduction to follow oncologic principles and prevent the spread of malignant cells. The resected tissue is sent for pathological review to determine the exact nature of the lead point. The pathology results—whether benign or malignant—guide necessary follow-up care and further treatment.