Intussusception occurs when one segment of the intestine slides into an adjacent part, like a collapsing telescope. This telescoping action can block the intestine, preventing passage of food and fluids, and cutting off blood supply to the affected bowel. While it can occur at any age, intussusception is most common in infants and young children, a frequent cause of acute abdominal distress. Prompt diagnosis is important to prevent complications. Ultrasound is the primary and most reliable method for identification.
Recognizing the Need for an Ultrasound
Doctors suspect intussusception based on sudden clinical signs and symptoms in a child. The classic presentation includes sudden, severe abdominal pain that comes and goes in waves, known as colicky pain, causing the child to cry and draw legs to chest. This pain recurs every 15 to 20 minutes, with periods of calm in between episodes. Vomiting is common, initially stomach contents, progressing to bile-stained material as obstruction worsens.
A characteristic, though not always present, sign is “currant jelly” stool (blood and mucus). This results from irritation and bleeding of the intestinal lining. Other indicators include lethargy, unusual sleepiness, or a palpable sausage-shaped mass in the abdomen. When these symptoms are observed, especially in young children, an ultrasound is ordered without delay to confirm or rule out the diagnosis.
The Ultrasound Procedure
Ultrasound is a non-invasive, painless medical imaging technique using sound waves to create pictures of internal organs and structures. For suspected intussusception, the procedure is straightforward, taking 15 to 30 minutes. The child lies on an examination table while a sonographer or radiologist performs the scan.
Warm gel is applied to the child’s abdomen, helping ultrasound waves travel effectively from the transducer to the body. The sonographer moves a small, handheld transducer, resembling a wand, gently over the abdomen. This device emits high-frequency sound waves that bounce off internal structures, converted into real-time images on a monitor. Ultrasound does not use ionizing radiation, making it a safe option for children. As intussusception is often an emergency, no special preparation, such as fasting, is required.
Interpreting the Ultrasound Findings
Radiologists interpret ultrasound for suspected intussusception by looking for specific visual patterns that confirm the diagnosis. The most characteristic finding is the “target sign” or “donut sign,” seen when the telescoped bowel is viewed in cross-section, like a cut sausage or jelly roll. This appearance is created by concentric rings of bowel wall and mesentery, representing the folded outer and inner segments of the intestine. These layers appear as alternating bright and dark rings.
Another finding is the “pseudokidney sign,” observed when intussusception is viewed longitudinally. This view shows multiple layers of bowel wall resembling kidney tissue. Both signs clearly demonstrate intestinal telescoping.
Ultrasound can also provide information about trapped fluid, enlarged lymph nodes, or free fluid. Additionally, Doppler ultrasound assesses blood flow to the affected area, determining if bowel blood supply is compromised. Absence of blood flow indicates a more severe condition requiring immediate intervention.
Next Steps After the Ultrasound
Once ultrasound results are available, the medical team determines the course of action based on whether intussusception is confirmed or ruled out. If ultrasound is positive for intussusception and there are no signs of bowel perforation or severe compromise, the next step is a non-surgical therapeutic enema. This involves introducing air or a liquid contrast, like barium, into the rectum, traveling up the colon. The pressure can push the telescoped segment back into its normal position, effectively reducing the intussusception.
This reduction attempt is performed under fluoroscopic guidance, allowing real-time visualization. If the enema is unsuccessful, or if there are signs of bowel perforation, peritonitis, or significant bowel damage, surgical intervention becomes necessary. During surgery, the affected intestine is manually reduced, or if damaged, the compromised section may be removed. If ultrasound is negative, doctors investigate other potential causes for the child’s symptoms, considering other abdominal conditions with similar signs.