Ileoileal Intussusception in a 1-Year-Old Boy: Ultrasound Findings, Bowel Ischemia, and Meckel Diverticulum as a Lead Point

Edited by ScholarGen MediAI Team

Executive Answer

Ileocolic intussusception is an uncommon form of pediatric intussusception in which one segment of ileum telescopes into an adjacent segment of ileum. In this 1-year-old boy, persistent vomiting despite treatment prompted abdominal radiography followed by ultrasound. The radiographs showed dilated small-bowel loops and multiple air-fluid levels with little gas in the lower abdomen, suggesting small-bowel obstruction. Ultrasound demonstrated the characteristic layered appearance of small-bowel intussusception, including a pseudokidney appearance on longitudinal imaging. Color Doppler showed partially preserved wall vessels but absent detectable flow in portions of the involved bowel, raising concern for ischemia. Surgery confirmed irreducible ileoileal intussusception with bowel ischemia, requiring resection. Pathology identified a Meckel diverticulum, which was considered the pathologic lead point.

Why This Case Matters

Intussusception is a time-sensitive pediatric abdominal emergency because telescoping of one bowel segment into another can produce obstruction, venous congestion, edema, impaired arterial perfusion, ischemia, and eventually necrosis.

Most pediatric intussusception is ileocolic rather than isolated small-bowel intussusception. Therefore, an ileoileal configuration deserves particular attention when the imaging pattern is confined to the small bowel.

This case illustrates an important radiology principle: recognizing the presence of intussusception is only the first diagnostic step. The radiologist should also assess:

• The anatomic type and location of the intussusception

• The extent of involved bowel

• Evidence of obstruction

• Bowel-wall perfusion

• Free intraperitoneal fluid

• A possible pathologic lead point

• Imaging features suggesting complicated or irreducible disease

The combination of a characteristic ultrasound appearance and abnormal vascular findings can provide clinically important information beyond simply identifying the intussusception.

Clinical Scenario

A 1-year-old boy presented with persistent vomiting despite treatment.

Because of concern for an underlying gastrointestinal process, abdominal radiography and abdominal ultrasound were performed.

The available clinical information does not report laboratory values or additional clinical findings such as fever, hematochezia, or a palpable abdominal mass.

The imaging evaluation therefore becomes particularly important in establishing the diagnosis and assessing the severity of the bowel involvement.

Imaging Findings

Abdominal Radiography

Two abdominal radiographs were obtained, including erect frontal and lateral views.

The radiographs demonstrate:

• Dilated small-bowel loops

• Multiple air-fluid levels

• Relatively little bowel gas in the lower abdomen

• A visible gastric air bubble

These findings support a mechanical small-bowel obstructive pattern.

However, plain radiography does not establish the specific cause of the obstruction. In a young child with persistent vomiting, the radiographic findings should prompt further evaluation when clinically indicated.

Figure 1. Abdominal radiograph, erect frontal view.
The frontal radiograph demonstrates dilated small-bowel loops with multiple air-fluid levels, consistent with a small-bowel obstructive pattern.

Figure 2. Abdominal radiograph, erect lateral view.
The lateral radiograph further demonstrates dilated bowel loops and air-fluid levels associated with the obstructive pattern.

Ultrasound Findings

Ultrasound provides the key diagnostic information in this case.

The involved small-bowel loops demonstrate telescoping of one bowel segment into another, producing the characteristic layered appearance of intussusception.

On longitudinal imaging, the involved bowel produces a characteristic pseudokidney appearance.

This appearance results from the longitudinal visualization of the multiple bowel-wall layers contained within the intussusception.

In transverse imaging, the corresponding configuration can produce the familiar target or doughnut appearance, although the exact sonographic appearance depends on the imaging plane and the components of the intussusception.

Figure 3. Transverse ultrasound image.
Transverse ultrasound demonstrates the characteristic concentric layered appearance of small-bowel intussusception.

Figure 4. Color Doppler ultrasound.
Color Doppler demonstrates partially preserved vascularity in the bowel wall, with areas in which detectable blood flow is absent. This finding raises concern for impaired perfusion and bowel ischemia.

Figure 5. Panoramic ultrasound image.
Panoramic ultrasound demonstrates the longitudinal extent and characteristic pseudokidney appearance of the involved bowel.

Radiologist's Reasoning

The diagnostic reasoning can be organized into several sequential questions.

1. Is there bowel obstruction?

Yes.

The abdominal radiographs demonstrate dilated small-bowel loops and air-fluid levels, with relatively little gas in the lower abdomen. In the clinical setting of persistent vomiting, these findings support small-bowel obstruction.

2. What is causing the obstruction?

Ultrasound demonstrates telescoping of one small-bowel segment into another.

This establishes the diagnosis of ileoileal intussusception.

3. Is this an uncomplicated intussusception?

The Doppler findings make uncomplicated disease less likely.

Although some bowel-wall vessels remain visible, there are regions without detectable Doppler flow. Reduced or absent vascularity within an intussuscepted bowel segment is concerning because progressive venous congestion and compromised perfusion can lead to ischemia and necrosis.

4. Is there evidence of a pathologic lead point?

The final surgical and pathologic findings provide the answer in this case.

A Meckel diverticulum was identified in the resected bowel and was considered the pathologic lead point responsible for the intussusception.

This is an important distinction because a structural lead point changes the clinical interpretation of the episode. It is not simply an unexplained telescoping event; there is an anatomic lesion capable of initiating or maintaining the intussusception.

Why the Pseudokidney Sign Matters

The pseudokidney sign is a classic longitudinal sonographic appearance of intussusception.

Instead of seeing a simple tubular bowel loop, the examiner sees multiple layers of bowel telescoped together. The alternating echogenic and hypoechoic layers correspond to the different bowel-wall components and the incorporated structures.

The sign is particularly useful because ultrasound can demonstrate both the anatomy and the complications of intussusception in real time.

A transverse examination may demonstrate the target or doughnut appearance, whereas longitudinal imaging may demonstrate the pseudokidney or sandwich-type appearance.

In this case, the longitudinal appearance was particularly important because it clearly demonstrated the telescoped small-bowel segments.

Color Doppler: The Critical Severity Assessment

One of the most clinically important features of this case is the Doppler assessment.

The bowel wall shows partially preserved vessels, but detectable flow is absent in some areas.

This should not be interpreted as an isolated binary marker of necrosis. Doppler sensitivity depends on technical factors, including equipment settings, bowel depth, patient motion, and the degree of vascular compromise.

Nevertheless, absent or markedly reduced vascularity within an intussuscepted segment is an important warning sign because impaired perfusion may indicate progression toward bowel ischemia.

The imaging interpretation should therefore integrate:

Intussusception + obstruction + abnormal vascularity + free fluid

rather than relying on a single sonographic sign.

In this case, the concern for ischemia was subsequently supported by the operative findings.

Free Intraperitoneal Fluid

The ultrasound examination also demonstrated intraperitoneal fluid.

Free fluid is not specific for bowel ischemia by itself. However, when it occurs together with an obstructing intussusception and abnormal bowel-wall perfusion, it increases the importance of evaluating the patient for complicated disease.

The radiologist should avoid interpreting individual findings in isolation.

The clinically useful interpretation comes from the combination of structural and hemodynamic abnormalities.

Why Ileoileal Intussusception Can Be Missed

Ileoileal intussusception can be diagnostically challenging for several reasons.

First, the most familiar pediatric intussusception pattern is ileocolic disease. A small-bowel-centered intussusception may therefore receive less immediate attention when the clinical presentation is nonspecific.

Second, small-bowel obstruction has a broad differential diagnosis. Dilated bowel loops and air-fluid levels on radiographs do not identify intussusception by themselves.

Third, a limited ultrasound examination may fail to characterize the entire involved segment.

Finally, recognizing an intussusception is not sufficient. The examiner must also determine whether there is impaired vascularity or another feature suggesting complicated disease.

A systematic multiplanar ultrasound examination is therefore essential.

Differential Diagnosis

The principal differential considerations for a child with vomiting and dilated small-bowel loops include mechanical small-bowel obstruction, ileoileal intussusception, adhesions or congenital obstructive lesions, and other causes of acute bowel obstruction.

Once ultrasound demonstrates characteristic telescoping bowel with concentric or longitudinal layered architecture, intussusception becomes the leading diagnosis.

The more important subsequent question is whether the intussusception is uncomplicated or associated with a pathologic lead point and compromised bowel.

Potential pathologic lead points in pediatric intussusception include Meckel diverticulum, intestinal duplication, polyps, and other structural or inflammatory lesions.

In this case, pathology established a Meckel diverticulum as the relevant lead-point lesion.

Meckel Diverticulum as a Pathologic Lead Point

Meckel diverticulum is a congenital remnant of the vitelline duct and can serve as a pathologic lead point for intussusception.

When a structural lesion acts as a lead point, normal peristaltic activity can contribute to telescoping of the involved bowel segment.

The presence of a Meckel diverticulum is particularly relevant in an unusual small-bowel intussusception because it provides a plausible structural explanation for why the intussusception developed.

In this case, the Meckel diverticulum was not simply an incidental pathologic finding. It was considered the lesion responsible for initiating the intussusception.

Importantly, the diagnosis of a Meckel diverticulum as the lead point was established through surgical and pathologic evaluation rather than being definitively demonstrated on the preoperative ultrasound.

Clinical Significance of Bowel Ischemia

The most important complication demonstrated in this case was bowel ischemia.

When bowel telescopes into an adjacent segment, the mesenteric vessels can become compressed. Venous outflow obstruction may occur first, producing congestion and edema. Progressive compromise can then affect arterial inflow and ultimately result in ischemia, necrosis, and perforation.

The imaging findings in this case raised concern for this progression.

At surgery, the involved bowel was ischemic and could not be successfully reduced. The affected segment was therefore resected.

This illustrates why the imaging assessment should extend beyond diagnosis to evaluation of bowel viability.

Diagnostic Risk Perspective

This case highlights several potential diagnostic vulnerabilities.

1. Anchoring on nonspecific obstruction

Dilated bowel loops and air-fluid levels can establish an obstructive pattern but do not establish the cause.

2. Stopping after identifying intussusception

The diagnosis of intussusception should be followed by assessment of vascularity, free fluid, extent, and possible lead points.

3. Incomplete ultrasound evaluation

Scanning in only one plane may reduce confidence in the diagnosis. Both transverse and longitudinal imaging contribute important information.

4. Underestimating small-bowel intussusception

The classic pediatric pattern is ileocolic, but an ileoileal configuration can occur and should remain in the differential diagnosis when the imaging findings support it.

5. Missing the significance of absent Doppler flow

Abnormal vascularity is an important warning sign that should trigger careful clinical correlation and urgent communication when appropriate.

Diagnostic Algorithm

A practical imaging pathway for a child with persistent vomiting and suspected bowel obstruction can be summarized as:

The exact treatment pathway depends on the patient's clinical status, the type of intussusception, institutional expertise, and evidence of complications.

AI Perspective: Where Medical Imaging AI May Help

This case also illustrates a potential role for AI-assisted medical imaging, particularly as a second-reader or workflow-support technology.

An AI system could theoretically assist by flagging imaging patterns suggestive of:

• Dilated small-bowel loops

• Target-like or concentric bowel-wall patterns

• Longitudinal pseudokidney appearances

• Abnormal bowel-wall morphology

• Possible intussusception

• Potentially abnormal vascularity on Doppler imaging

However, this should remain an assistive role.

The case does not provide evidence for the diagnostic performance of any specific AI system, and no claim about sensitivity, specificity, accuracy, or clinical outcome should be made from a single case.

AI should not replace direct image review by a qualified clinician.

AI Failure Modes in This Case Type

An AI system applied to pediatric abdominal imaging could encounter several realistic failure modes.

False negatives

A short-segment or atypically located ileoileal intussusception could potentially be overlooked, particularly if the relevant bowel segment is not well represented in the input images.

False positives

Thickened or folded bowel loops, stool, or other abdominal structures may potentially mimic the appearance of intussusception.

Image-quality dependence

Ultrasound is operator-dependent, and image quality may vary with patient motion, bowel gas, depth, and scanning technique.

Domain shift

An AI model trained predominantly on classic ileocolic intussusception may not generalize reliably to less common ileoileal cases.

Automation bias

A negative AI result should not override convincing clinical or imaging evidence, and a positive AI alert should not be accepted without image-level verification.

The appropriate role for AI is therefore diagnostic support rather than diagnostic responsibility transfer.

Practical Radiology Pearls

1. Persistent vomiting plus dilated small-bowel loops and air-fluid levels should raise concern for mechanical obstruction.

2. Ultrasound is particularly valuable when pediatric intussusception is suspected because it can demonstrate both the bowel configuration and potential complications.

3. The transverse target or doughnut appearance and longitudinal pseudokidney appearance are complementary signs of intussusception.

4. An ileoileal configuration should be recognized as a small-bowel form of intussusception rather than assuming that all pediatric cases are ileocolic.

5. Color Doppler assessment is important when evaluating bowel viability.

6. Absent detectable flow in part of an intussuscepted segment should raise concern for compromised perfusion, although Doppler findings must be interpreted in technical and clinical context.

7. Free intraperitoneal fluid should be interpreted together with the other imaging findings rather than as an isolated marker of ischemia.

8. An unusual or complicated intussusception should prompt consideration of a pathologic lead point.

9. Meckel diverticulum can act as a lead point for pediatric intussusception.

10. The imaging diagnosis should communicate not only what the lesion is, but also whether there are features suggesting complicated disease.

Common Pitfalls

• Focusing only on the abdominal radiograph and not proceeding to targeted ultrasound when clinically appropriate

• Assuming that pediatric intussusception is necessarily ileocolic

• Performing an incomplete ultrasound examination

• Evaluating the bowel morphology without assessing vascularity

• Treating absent Doppler flow as an absolute standalone diagnosis of necrosis

• Failing to consider a pathologic lead point in an atypical case

• Overlooking free intraperitoneal fluid

• Reporting intussusception without communicating concerning signs of bowel compromise

• Assuming that an AI result can substitute for direct clinical image interpretation

Frequently Asked Questions

What is ileoileal intussusception?

Ileoileal intussusception occurs when one segment of ileum telescopes into an adjacent segment of ileum. It is a form of small-bowel intussusception and differs anatomically from the more common ileocolic pattern.

What is the key ultrasound finding in intussusception?

The classic findings include a concentric target or doughnut appearance on transverse imaging and a pseudokidney-type appearance on longitudinal imaging. These reflect telescoping of bowel segments and their associated mesenteric structures.

Why is color Doppler important in intussusception?

Color Doppler can help assess bowel-wall perfusion. Preserved vascularity is reassuring, whereas absent or markedly reduced detectable flow may raise concern for compromised perfusion and ischemia. Doppler findings must be interpreted together with the overall clinical and imaging picture.

Can Meckel diverticulum cause intussusception?

Yes. Meckel diverticulum can serve as a pathologic lead point for intussusception. In this case, the resected bowel contained a Meckel diverticulum, which was considered the lead point.

Is ileoileal intussusception the same as ileocolic intussusception?

No. Ileoileal intussusception involves one ileal segment telescoping into another ileal segment. Ileocolic intussusception involves the ileum telescoping through the ileocecal region into the colon. The distinction is important because the anatomy and potential causes can differ.

What does a pseudokidney sign mean on ultrasound?

The pseudokidney sign is a longitudinal sonographic appearance produced by telescoped bowel segments. It should prompt consideration of intussusception when seen in the appropriate clinical setting.

Can AI diagnose pediatric intussusception?

AI may potentially assist with detection or triage of imaging findings, but this case does not establish the performance of any AI system. AI output should be treated as decision support and verified by qualified clinicians.

Key Takeaways

This case demonstrates the diagnostic value of integrating abdominal radiography, grayscale ultrasound, and color Doppler assessment in a child with persistent vomiting and suspected bowel obstruction.

The radiographs demonstrated a small-bowel obstructive pattern. Ultrasound established the diagnosis of ileoileal intussusception through characteristic telescoped bowel morphology and a pseudokidney appearance.

The additional finding of absent detectable Doppler flow in portions of the involved bowel raised concern for ischemia. Surgery subsequently confirmed ischemic, irreducible ileoileal intussusception requiring bowel resection.

Pathologic examination identified a Meckel diverticulum, providing a structural pathologic lead point.

The broader radiology lesson is straightforward:

Do not stop after identifying intussusception. Determine its location, evaluate bowel perfusion, look for complications, and consider an underlying lead point when the presentation or imaging pattern is atypical.

Continue Learning

If you want to understand the imaging signs:
[INTERNAL LINK] — Target Sign and Pseudokidney Sign in Pediatric Intussusception

If you want to understand the differential diagnosis:
[INTERNAL LINK] — Pediatric Small-Bowel Obstruction: Imaging Differential Diagnosis

If you want to understand the pathologic lead point:
[INTERNAL LINK] — Meckel Diverticulum as a Lead Point for Intussusception

If you want to understand AI in pediatric imaging:
[INTERNAL LINK] — AI-Assisted Detection of Intussusception on Ultrasound

If you want to understand workflow implications:
[INTERNAL LINK] — How AI Could Support Pediatric Emergency Imaging

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Medical Disclaimer

This article is provided for educational and informational purposes only and is not intended to provide medical advice, diagnosis, or treatment. Imaging findings and clinical interpretations should be considered in the context of the individual patient and evaluated by qualified healthcare professionals. This case does not replace professional medical judgment, institutional protocols, or consultation with an appropriate specialist.