How common are asymptomatic ileal neuroendocrine (carcinoid) tumors in adults presenting with ileal intussusception on CT scan?

Asymptomatic Ileal Carcinoid Tumors Are Common, But Intussusception Strongly Suggests Malignancy

In adults presenting with ileal intussusception on CT, a carcinoid tumor is highly likely to be the underlying cause, and while many ileal carcinoids can be asymptomatic for years, the presence of intussusception itself represents a symptomatic manifestation requiring urgent surgical intervention.

Prevalence of Asymptomatic Ileal Carcinoids

The true burden of neuroendocrine tumors far exceeds what is diagnosed clinically:

• Autopsy studies reveal that gastrointestinal NETs are substantially more common than detected during life, indicating many patients harbor these tumors asymptomatically 1
• In surgical series, 60% of all gastrointestinal carcinoid tumors were discovered incidentally as asymptomatic lesions 2
• However, among patients specifically with ileal carcinoid tumors, 48% were symptomatic at presentation 2, making ileal primaries more likely to cause symptoms compared to other GI sites
• There is typically a 7-year delay between first symptoms and diagnosis, suggesting prolonged periods of minimal or non-specific symptoms 1

Clinical Context of Intussusception

Your patient's presentation changes the clinical picture significantly:

• Adult intussusception is pathologic in 90% of cases, with an identifiable structural lesion serving as the lead point 3
• Carcinoid tumors are a recognized cause of adult ileocecal intussusception 4, 3, though less common than adenocarcinoma in colonic intussusception
• The intussusception itself represents a symptomatic complication of the tumor, even if the patient had no prior carcinoid-specific symptoms (flushing, diarrhea) 4

Metastatic Potential at Presentation

Ileal carcinoids have aggressive metastatic behavior that is often clinically silent:

• Ileal carcinoids demonstrate 60% nodal metastases and 30% liver metastases at diagnosis 5, the highest rates among GI carcinoids
• Critically, 18% of ileal carcinoids smaller than 1 cm already have metastases 2, emphasizing that tumor size does not predict benign behavior
• Carcinoid syndrome occurs in only 20% of ileal NET cases 1, meaning 80% lack the classic hormonal symptoms even with advanced disease
• The syndrome typically requires liver metastases to manifest, as hepatic first-pass metabolism normally clears vasoactive substances 1

Diagnostic and Management Algorithm

For your patient with ileal intussusception on CT:

1. Proceed directly to surgical exploration - adult intussusception requires resection without attempted reduction due to high malignancy risk 3

2. Expect to find a carcinoid tumor - this is a well-documented cause of ileocecal intussusception in adults 4, 3

3. Perform extended resection with wide mesenteric lymph node sampling - given the 60% rate of nodal involvement in ileal primaries 5

4. Obtain intraoperative assessment for mesenteric disease and liver metastases 4

5. Send tissue for immunohistochemistry (chromogranin A, synaptophysin) and Ki-67 proliferation index for WHO grading 6

6. Postoperative biochemical evaluation with 5-HIAA and chromogranin A to assess for residual disease 4

Critical Pitfalls to Avoid

• Do not assume the tumor is benign based on absence of carcinoid syndrome - 80% of ileal NETs lack hormonal symptoms 1
• Do not rely on tumor size alone - even sub-centimeter ileal carcinoids metastasize in 18% of cases 2
• Do not attempt radiologic or endoscopic reduction - formal surgical resection is required for adult intussusception due to high malignancy rates 3
• Do not overlook synchronous malignancies - 20% of NET patients develop other cancers, one-third in the GI tract 1