Intussusception in Adults

Etiology

Intussusceptions are classified as benign or malignant based on their etiology. In adults, more than 90% of cases have a pathological lead point, most commonly a neoplasm.[5][6] Benign causes are typically in the small intestine and include a Meckel diverticulum, lipomas, lymphoid hyperplasia, hemangiomas, adhesions, or adenomas associated with Peutz-Jeghers syndrome. Malignant causes include metastasis, adenocarcinoma, gastrointestinal stromal tumor, lymphoma, leiomyosarcoma, and neuroendocrine tumors. Other etiologies include iatrogenic causes such as catheter placement or gastrojejunostomy.[7]  

Epidemiology

Intussusception in adults is extremely rare, found in less than 1 in 1300 abdominal operations. Children are affected more than adults, with an approximate 20:1 ratio. Intussusception represents 1% of small bowel obstructions in adults, with the most common cause being a tumor.[8]

Pathophysiology

Intussusception is a condition involving part of the intestine folding into the section adjacent to it. Part of the proximal bowel (intussusceptum) slides into the adjacent distal section (intussuscipiens) and can cause bowel obstruction as well as intestinal ischemia. The mesentery may or may not be involved. The blood supply to the affected bowel is compressed due to impaired peristalsis, leading to bowel obstruction and gangrene if not treated. Perforation and sepsis can occur from a segment of intestine becoming necrotic secondary to ischemia.[1]

Nonspecific abdominal pain is the most common symptom in adults. Patients may also present with vomiting (can be bilious), bloating, or even bloody stool.[9][10][11] This condition may also result in small- or large-bowel obstruction. In adults, symptoms can be acute, intermittent, or chronic, which complicates diagnosis.[12] The most common site of an intussusception is the ileocecal junction and involves a freely moving segment of bowel with a fixed retroperitoneal structure. The adult intussusception is generally divided into four main categories based on the site of the origin:

• Enteroenteric: involving the small bowel
• Ileocolic: terminal ileum telescoping into the ascending colon
• Ileocecal: the ileocecal valve is the lead point
• Colocolic: involving the large bowel [1]

Histopathology

Histopathology does not play a role in the diagnosis of intussusception. However, histopathology is important in determining the etiology in cases with a pathological lead point, such as a neoplasm. 

History and Physical

Although relevant, the history and physical examination are variable in adults. The most common presenting symptom is abdominal pain in over 80% of affected adults.[1] However, the classic triad of abdominal pain, bloody currant-jelly stools, and a palpable, tender abdominal mass seen in children is uncommon in adults. Adults may present with chronic and intermittent abdominal cramping associated with nonspecific abdominal symptoms such as nausea, vomiting, gastrointestinal bleeding, abdominal distention, or constipation.[13]

Evaluation

Abdominal computed tomography (CT) appears to be the most sensitive diagnostic method in making a preoperative diagnosis of adult intussusception, especially in patients presenting with nonspecific abdominal pain.[14][15] However, plain abdominal radiography is often the first diagnostic imaging modality, as most patients present with obstructive symptoms. Upper gastrointestinal studies may demonstrate a "stacked coin" or "coil-spring" appearance. On barium enema, a "cup-shaped" filling defect, "spiral" appearance, or "coil-spring" appearance is characteristically seen in patients with colocolic or ileocolic intussusceptions.[11]

Ultrasonography of the abdomen has lower sensitivity for detecting adult intussusception than abdominal CT. Still, this modality can identify the characteristic "target" sign in the transverse view or the "pseudo-kidney" sign in the longitudinal view, especially in patients presenting with a palpable abdominal mass, where it is more than 90% sensitive.[4][5][11][15] Ultrasound has several disadvantages, including the masking of identifiable features by gas-filled bowel loops and operator dependency.[16][17][18]

The cardinal features on abdominal CT include a "target"- or "sausage"-shaped soft-tissue mass with a layering effect. Visualization of mesenteric vessels within the bowel lumen may also be seen. Abdominal CT can define the location and nature of the mass, its proximity to surrounding structures, and staging in cases of suspected malignancy. Abdominal CT can also determine whether there is a lead point (features suggestive of proximal bowel obstruction).[11] Endoscopy plays a limited role in the diagnosis of adult intussusception. In patients presenting with subacute or chronic large bowel obstruction, lower endoscopy can confirm the intussusception, localize the disease, and identify the lead point.[11]

Treatment / Management

Adult intussusception typically necessitates surgical intervention because of the high incidence of an associated malignancy.[19] However, spontaneous resolution of intussusception without lead points has been reported. A selective approach to resection in adult intussusception has been recommended. Due to the high association with a malignancy, resection without reduction has been recommended whenever possible in ileocolic, colocolic, and ileocecal intussusception. A formal resection using appropriate oncologic techniques should be performed.[15] (B2)

Manipulation and reduction of intussuscepted bowel carry risks, including intraluminal seeding and dissemination of tumor cells, perforation and release of microorganisms into the peritoneal cavity, and an increased risk of anastomotic complications. Reduction should not be attempted in cases of inflammation or bowel ischemia.[11][15][20] In small bowel intussusceptions, reduction should be attempted unless bowel ischemia is present.[15] Laparoscopy can be successfully used in selected cases, depending on the patient's clinical condition and the availability of laparoscopic expertise.[11](B3)

Differential Diagnosis

In adults, the nonspecific symptoms and clinical presentation lead to a wide differential diagnosis. Differential diagnoses include:

• Volvulus
• Small bowel obstruction 
• Large bowel obstruction 
• Peptic ulcer disease 
• Mesenteric ischemia 
• Constipation
• Inflammatory bowel disease 
• Irritable bowel syndrome 
• Diverticulitis 
• Diverticulosis 
• Appendicitis
• Crohn disease
• Cystic fibrosis
• Ovarian torsion 
• Tubo-ovarian abscess
• Fibroids 
• Pelvic inflammatory disease 
• Pyelonephritis 
• Ileus
• Meckel diverticulum
• Foreign bodies [18][21]

Surgical Oncology

Adult intussusception is associated with an identifiable cause in approximately 90% of cases. Benign or malignant neoplasms account for two-thirds of all cases, with more than 50% malignant.[21] The presence of anemia and colonic intussusception is an independent predictor of malignancy.[21][22]

Malignancy is a leading cause of intussusception, with metastatic disease the most common cause. Malignant causes of small bowel intussusception include leiomyosarcomas, adenocarcinoma, gastrointestinal stromal tumors, carcinoid tumors, neuroendocrine tumors, and lymphomas. Colonic intussusception is more likely to have a malignant lead point. Common malignant causes of malignant colonic intussusception include adenocarcinoma, sarcoma, and lymphoma.[21]

Due to the increased incidence of an underlying malignancy in colonic intussusception and the inability to distinguish a malignant from a benign etiology preoperatively or intraoperatively, primary resection without reduction of the intussusception is recommended. Reduction of intussusceptions with a malignant lead point has a theoretical risk of intraluminal seeding of malignant cells and venous embolization.[21][22][18] Standard oncological principles should be applied to resect an unreduced intussusception, including lymphadenectomy of major draining vessels and resection of at least 12 lymph nodes to facilitate accurate diagnosis and future chemotherapeutic intervention.[21]

Prognosis

The prognosis is generally favorable, depending on the etiology of the intussusception. The rarity of this disease, diagnostic delays, and the prevalence of malignancy can lead to severe complications that can have high mortality rates.[23] Prognosis is worse in small bowel intussusceptions associated with metastatic disease.[13] 

Transient cases of adult intussusception have been reported. The results of a retrospective analysis demonstrated that intussusceptions less than 4 cm in length were more likely to respond to conservative management. Intussusceptions greater than 9.6 cm were more likely to require surgical exploration.[24]

Complications

Given the high probability of a delay in diagnosis due to vague complaints and an extensive differential diagnosis, intussusception has the potential for life-threatening complications. Complications include superficial wound infections, bowel obstruction, bowel necrosis, perforation, septic shock, pneumonia, and severe organ failure.[13][18][23] Mortality rates are more severe depending on the etiology of the intussusception and when the diagnosis is delayed.[23] Mortality rates range from 0% to 5%.[18][23][25]