Adult Intussusception: A Rare but Critical CT Diagnosis Every Clinician Should Recognize

Imagine a previously healthy middle-aged man arriving at the emergency department with severe upper abdominal pain and nausea.

Initial evaluation appears relatively unremarkable. Laboratory findings are nonspecific. Symptoms partially improve with conservative management.

Then the pain returns.

A repeat CT scan reveals one of radiology's most recognizable yet potentially deceptive imaging signs—the "Target Sign."

What appears at first glance to be a transient bowel abnormality may actually conceal an underlying malignancy.

This was precisely the situation encountered in a patient ultimately diagnosed with jejunojejunal intussusception caused by small bowel adenocarcinoma.

For radiologists, emergency physicians, gastroenterologists, and surgeons, adult intussusception remains a fascinating yet clinically important diagnosis because it differs dramatically from the pediatric disease.

Unlike childhood intussusception, which is usually idiopathic, adult intussusception frequently has a pathological lead point, including benign tumors, malignant neoplasms, postoperative adhesions, inflammatory lesions, and metastatic disease.

Understanding the imaging findings is therefore essential for accurate emergency diagnosis and optimal patient outcomes.

What Is Intussusception?

Intussusception occurs when a segment of bowel telescopes into an adjacent bowel segment.

The invaginating segment is known as the intussusceptum, while the receiving segment is called the intussuscipiens.

As the bowel folds into itself, mesenteric fat and blood vessels become trapped within the lesion.

This process can result in:

Bowel obstruction
Venous congestion
Bowel wall edema
Ischemia
Necrosis
Perforation
Sepsis

When untreated, the condition can rapidly become life-threatening.

Epidemiology

Pediatric Intussusception

Approximately 90% of pediatric cases are idiopathic.

Peak incidence:

6–18 months of age
Male predominance
Frequently follows a viral infection

Adult Intussusception

Adult cases account for:

1–5% of bowel obstructions
Approximately 5% of all intussusceptions

Important differences:

Feature	Pediatric	Adult
Cause	Usually idiopathic	Usually pathological
Malignancy risk	Rare	Common
Treatment	Enema reduction	Often surgery
Imaging modality	Ultrasound	CT scan

Pathophysiology

The development of intussusception begins when a focal lesion alters normal bowel peristalsis.

Potential lead points include:

Benign Causes

Lipoma
Hamartoma
Polyps
Meckel diverticulum
Adhesions

Malignant Causes

Adenocarcinoma
Lymphoma
Gastrointestinal stromal tumor (GIST)
Metastatic melanoma

Postoperative Causes

Anastomotic sites
Scar tissue
Altered motility

The lead point becomes pulled forward by peristalsis, dragging adjacent bowel inward and creating the characteristic telescoping configuration.

Clinical Presentation

Adult intussusception frequently presents with nonspecific symptoms.

Common manifestations include:

Intermittent abdominal pain
Nausea
Vomiting
Abdominal distension
Gastrointestinal bleeding
Weight loss

Unlike pediatric patients, adults rarely exhibit the classic triad of:

Abdominal pain
Bloody stool
Palpable mass

This diagnostic ambiguity often delays treatment.

Case Presentation: Jejunojejunal Intussusception Revealed by CT

A middle-aged male presented with upper abdominal pain and nausea.

Initial CT imaging demonstrated bowel intussusception.

Conservative management temporarily improved symptoms.

However, symptoms recurred several days later.

Repeat CT imaging demonstrated:

Dilated small bowel loops
Classic target sign
Features highly suggestive of recurrent intussusception

Subsequent surgery confirmed jejunojejunal intussusception associated with an intraluminal tumor.

Pathologic analysis revealed:

5.5 cm adenocarcinoma
Stage T2N0
Negative surgical margins

This case illustrates why adult intussusception should never be dismissed as a benign transient finding.

Imaging Evaluation of Intussusception

Why Medical Imaging Is Essential

Clinical findings alone are often insufficient.

Modern medical imaging plays a central role in:

Early detection
Emergency diagnosis
Surgical planning
Identification of lead points
Assessment of complications

CT Scan Diagnosis: The Gold Standard

CT is currently the most sensitive imaging technique for adult intussusception.

Reported diagnostic accuracy frequently exceeds 80–90%.

Advantages include:

Visualization of bowel layers
Detection of lead points
Evaluation of ischemia
Assessment of obstruction severity

Figure 1. Axial CT scan showing the classic "Target Sign" of small bowel intussusception.

Radiologic Interpretation

The CT image demonstrates:

Concentric bowel rings
Infiltrated mesenteric fat
Telescoping bowel loops
Small bowel dilation

The alternating soft tissue and fat attenuation creates the characteristic target appearance that strongly suggests intussusception.

In this patient, no definitive lead point was identified on CT, although surgery subsequently revealed adenocarcinoma as the underlying cause.

Diagnostic Importance

The target sign is among the most important CT findings in emergency radiology and should immediately prompt evaluation for:

Bowel obstruction
Ischemia
Underlying neoplasm

Key CT Findings

Target Sign

Cross-sectional appearance:

Multiple concentric rings
Alternating soft tissue density
Mesenteric fat is centrally located

Sausage-Shaped Mass

Longitudinal appearance:

Layered tubular configuration
Bowel-within-bowel appearance

Mesenteric Vessel Entrapment

Findings include:

Twisting vessels
Mesenteric edema
Venous congestion

Bowel Obstruction

Indicators include:

Dilated proximal loops
Air-fluid levels
Distal collapse

X-Ray Findings

Although less sensitive than CT imaging, abdominal radiographs may demonstrate:

Dilated bowel loops
Air-fluid levels
Partial obstruction

Radiographs rarely establish a definitive diagnosis.

Ultrasound Findings

Ultrasound remains highly effective in pediatric patients.

Characteristic signs include:

Doughnut Sign

Cross-sectional view showing concentric rings.

Pseudokidney Sign

Longitudinal view resembling renal morphology.

In adults, CT remains superior.

Figure 2. Intraoperative photograph demonstrating jejunojejunal intussusception with an intraluminal tumor acting as the lead point.

Radiologic-Pathologic Correlation

Surgery revealed:

Ischemic bowel discoloration
Telescoped jejunal segment
Palpable intraluminal mass

Pathology confirmed adenocarcinoma as the lead point.

Clinical Significance

This image highlights the most important principle of adult intussusception:

"Always search for an underlying pathological lead point."

Differential Diagnosis

Radiologists should distinguish intussusception from:

Condition	Key Imaging Feature
Bezoar	Mottled intraluminal mass
Crohn Disease	Segmental wall thickening
Mesenteric Ischemia	Poor enhancement
Volvulus	Whirl sign
Diverticulitis	Inflamed diverticula
Small Bowel Tumor	Focal mass lesion

Diagnostic Workflow

Step 1: Clinical Suspicion

Symptoms:

Intermittent pain
Nausea
Obstruction

Step 2: Initial Imaging

X-ray
Ultrasound

Step 3: CT Scan Diagnosis

Identify:

Target sign
Lead point
Obstruction

Step 4: Surgical Assessment

Evaluate:

Bowel viability
Malignancy risk

Step 5: Pathologic Confirmation

Determine:

Benign vs malignant cause
Tumor stage
Treatment planning

Treatment

Nonoperative Management

Appropriate only in selected transient cases.

Observation may be considered when:

No obstruction exists
No lead point identified
Symptoms resolve completely

Surgical Management

Preferred for most adults.

Options include:

Reduction
Segmental bowel resection
Oncologic resection

The presence of malignancy often necessitates formal resection.

Prognosis

Outcome depends primarily upon:

Etiology
Timing of diagnosis
Presence of ischemia
Presence of malignancy

When diagnosed early:

Mortality is low
Recovery is excellent

Delayed diagnosis increases the risk of:

Necrosis
Perforation
Sepsis

Key Takeaways

✓ Adult intussusception is uncommon but clinically important.

✓ CT imaging is the diagnostic gold standard.

✓ The target sign is the hallmark imaging feature.

✓ Most adult cases have a pathological lead point.

✓ Malignancy must always be excluded.

✓ Early recognition improves survival and reduces complications.

Frequently Asked Questions (FAQ)

Is intussusception a medical emergency?

Yes. Delayed treatment may result in bowel ischemia, perforation, and sepsis.

What is the CT target sign?

A concentric ring appearance created by telescoped bowel segments.

Can adults develop intussusception?

Absolutely. Although rare, adult cases often indicate an underlying pathology.

Is surgery always required?

Many adult patients undergo surgery because of the high likelihood of a lead-point lesion.

Can cancer cause intussusception?

Yes. Adenocarcinoma, lymphoma, and metastatic tumors are recognized causes.

Quiz

Question 1. Which CT finding is most characteristic of intussusception?

A. String sign

B. Apple-core lesion

C. Target sign

D. Thumbprinting

E. Pneumatosis intestinalis

Correct Answer: C. Target sign. Explanation: The target sign reflects concentric bowel layers resulting from telescoping bowel segments and is the hallmark CT feature.

Question 2. Which statement regarding adult intussusception is correct?

A. Usually idiopathic

B. Rarely requires surgery

C. Usually caused by infection

D. Frequently associated with a pathological lead point

E. Diagnosed primarily by ultrasound

Correct Answer: D. Frequently associated with a pathological lead point. Explanation: Unlike pediatric cases, adult intussusception often results from tumors or structural abnormalities.

Question 3. What was the pathological diagnosis in this case?

A. Lipoma

B. Lymphoma

C. Adenocarcinoma

D. GIST

E. Hamartoma

Correct Answer: C. Adenocarcinoma. Explanation: Surgical pathology demonstrated a 5.5-cm T2N0 adenocarcinoma that served as the lead point for jejunojejunal intussusception.

Summary Table

Feature	Adult Intussusception
Best Imaging Test	CT Scan
Hallmark Sign	Target Sign
Common Cause	Lead Point Lesion
Major Concern	Malignancy
Treatment	Surgery
Prognosis	Excellent if diagnosed early

Adult Intussusception: CT Imaging Diagnosis, Target Sign Recognition, and the Hidden Risk of Small Bowel Adenocarcinoma