Intestinal Intussusception: Recognizing the "Target" or "Donut" Sign on Ultrasound

A Pediatric Emergency Department Par Excellence

Intussusception (or invagination of the intestine) is a medical emergency that occurs predominantly in infants and young children (between 3 months and 3 years of age). It consists of the telescoping or telescoping of one segment of the intestine (the invaginated segment) into another adjacent segment ( the invaginating segment ) . This causes intestinal obstruction, edema, compression of blood vessels, and, if not treated promptly, can lead to ischemia (lack of blood flow), necrosis (tissue death), and perforation. The classic presentation is a previously healthy child with episodes of crying or acute, intermittent abdominal pain, accompanied by vomiting and, sometimes, the passage of bloody and mucous stools ("currant jelly").

Ultrasound: The First-Line and Preferred Diagnostic Imaging Method

In cases of suspected intussusception, abdominal ultrasound is the initial diagnostic study—rapid, accurate, and radiation-free . It has almost completely replaced X-rays and barium enemas for initial diagnosis due to its critical advantages:

• High Sensitivity and Specificity: Close to 100% in expert hands.

• Safety: It does not use ionizing radiation, crucial for pediatric patients.

• Speed and Accessibility: It can be performed in the same emergency room.

• Diagnosing Causes: You can identify a "lead point" such as cysts, polyps, or abnormal lymph nodes.

• Therapeutic Guidance: Can monitor non-surgical reduction during the enema.

  
  

The Pathognomonic Ultrasound Finding: The "Target", "Donut" or "Target Sign"

Ultrasound is so specific because it finds a characteristic and repeatable image in almost all cases:

1. The "Target" or " Donut " Sign

most famous and diagnostic finding . It appears as a rounded mass with alternating concentric layers of different echogenicity .

• Hyperechoic External Ring (White/Gray): Corresponds to the edematous wall of the intussuscepted intestine .

• Hypoechoic (Dark) Intermediate Layer : Corresponds to the edema of the wall of the intussuscepted intestine .

• Hyperechoic Center (White/Gray): This may represent the mucosa of the intussuscepted bowel and, sometimes, the trapped mesentery and fat (which is hyperechoic ). In some cases, the center may be more heterogeneous .

  
  

  This layered image is practically diagnostic on its own in the appropriate clinical context.

2. Longitudinal Section (Sagittal View): The " Pseudokidney " or "Sandwich" Sign Sign , Sandwich Sign )

When the transducer is placed along the axis of the invaginated intestine, an oblong or sausage-shaped structure is seen .

• Hyperechoic outer borders .

• Heterogeneous Center or Internal Strata. It resembles the image of a kidney, hence its name.

3. Other Associated Ultrasound Findings:

• Intra-abdominal Free Fluid : May be present.

• Absence of Peristalsis : In the invaginated segment.

• Enlarged Mesenteric Lymph Nodes: Located near the affected area, reactive to inflammation.

• "Lead Point": In 5-10% of cases (more common in older children), a structural cause can be identified that acts as an anchor for the invagination (e.g., a hyperechoic juvenile polyp , an enterogenic duplication cyst , a Meckel's diverticulum , or, in rarer cases, a lymphoma ).

The Role of Ultrasound in Treatment: Enema Reduction

uncomplicated ileocolic intussusception is enema reduction , which can be performed under fluoroscopic guidance (with X-rays) or, preferably and increasingly commonly, under ultrasound guidance .

• Advantages of Ultrasound: It completely avoids radiation exposure for both the patient and medical staff. The radiologist observes in real time the retreat of the "target sign" as the fluid (saline or air) administered rectally reduces the intussusception, until the free passage of fluid into the terminal ileum is observed.

• Success Criterion: The disappearance of the invaginated mass and the visualization of fluid flow through the ileocecal valve into the ileum.

Ultrasound Differential Diagnosis

Although the target sign is very specific, other abdominal masses in children can be confusing:

• Lymphadenitis : Swollen lymph nodes that may cluster together, but do not have a clear concentric layered architecture.

• Abdominal Tumor: Solid or cystic masses ( neuroblastoma , Wilms tumor ), which usually have a different structure and retroperitoneal location.

• Normal Appearance of Ileocecal Valves or Edematous Intestinal Loops: The operator's experience is key to avoid overdiagnosis .

Conclusion: Ultrasound, a Tool that Saves Intestines and Avoids Radiation

Intussusception is a race against time. Ultrasound is the cornerstone of diagnosis and a key facilitator of treatment in this emergency. Its ability to provide an immediate and non-invasive diagnosis with a clear pathognomonic sign allows for reduction treatment to begin within hours, saving the child's bowel and avoiding major surgery. The possibility of performing therapeutic reduction under ultrasound guidance further solidifies its role as the safest and preferred comprehensive (diagnostic and treatment) technique in the modern management of pediatric intussusception.

Intestinal intussusception pediatric ultrasound

ECOGRAFIA ABDOMINAL COMPLETA

$200.00

15min

Book Now

Dr. Jose Segnini, Radiologist / Diagnostic Medical Sonographer

MD Radiologist (Venezuela – Chile)

Board Certified Diagnostic Medical Sonographer (ARDMS, USA)

Mobile Ultrasound & Medical Supplies – Orlando, Florida