An ultrasound may be helpful in the diagnosis of intussusception. Findings on an ultrasound suggestive of/diagnostic of Intussusception include target sign or doughnut sign and pseudokidney sign. If the ultrasonographer is experienced then sensitivity, specificity and negative predictive value can be close to 100%.

• Ultrasound is the gold standard imaging modality used to diagnose intussusception^[1]
• If the ultrasonographer is experienced then ^[2]
  • Sensitivity – 100%
  • Specificity – 100%
  • Negative predictive value – 100%
• Target or doughnut sign^[3]
  • Edematous intussuscipien forms an external ring around the centrally located intussusceptum
  • Target sign is usually seen in right lower quadrant
• Layers of intussusception forms pseudo-kidney appearance on the transverse view
• Ultrasound in adults:
  • Less accurate than in children
  • Target sign or doughnut sign
    • Concentric alternating echogenic and hypoechogenic bands
    • Echogenic bands are formed by mucosa and muscularis
    • Hypoechoic bands – formed by the submucosa
    • Can be visualized in transverse view
  • Pseudo-kidney sign – It can be visualized in longitudinal view
  • The intussuscepted segment of bowel mimics a kidney
• Ultrasound can be used to diagnose ileo-ileal intussusception which is a rare form. Fluoroscopy can miss this form of intussusception
• Ultrasound can detect the pathology in 2/3rd of cases.^[4]
• Color duplex can detect ischemia of intussusception. It detects lack of perfusion
• Small bowel intussusception:
  • Jejuno-jejunal or jejuno-ileal, rather than ileocolic intussusception :
    • If the intussusception is outside of the right lower quadrant – paraumbilical or left abdominal region
    • Lesion size ≤3 cm
  • In children if small bowel intussusception is suspected and the symptoms are mild
    • Repeat the ultrasound to see if the finding persists as small bowel intussusceptions mostly reduce spontaneously
    • If the finding persist then next step is to evaluate using a CT scan. CT scan can detect if there is a lead point
  • The length of the intussusceptum is measured using ultrasound or CT scan. It helps to determine the prognosis so that management is started accordingly
• Limitations of ultrasound:^[5]
  • In cases of bowel distension and morbid obesity, massive air can result in reduced rate of detection and diagnosis of intussusception.