Ultrasound Findings
| Finding | Description |
|---|---|
| Target sign / donut sign (transverse view) | Hypoechoic outer rim (intussuscipiens) surrounding echogenic center (intussusceptum with mesenteric fat); multiple concentric rings of bowel-within-bowel |
| Pseudokidney sign (longitudinal view) | Elongated ovoid mass resembling a kidney; hyperechoic mesenteric fat surrounded by hypoechoic bowel wall layers; most common in RUQ or epigastrium |
| Lead point | Identified in ~5% of cases; Meckel's diverticulum, polyp, duplication cyst, lymphoma; suspect if age >5 years, recurrent episode, or identifiable mass within intussusceptum |
| Free fluid | Simple anechoic fluid does not preclude reduction; complex or echogenic free fluid → concern for bowel ischemia or perforation |
| Trapped lymph nodes | Mesenteric nodes within intussusceptum; reactive post-viral lymphadenopathy is the most common identifiable "lead point" at any age |
Post-viral lymphadenopathy is the most common lead point — mesenteric nodes enlarge after a viral illness and act as a fulcrum for ileocolic telescoping. This is why intussusception peaks in spring and fall coinciding with viral seasons.
Enema Reduction
Pneumatic (air) or hydrostatic (saline/contrast) reduction under fluoroscopic or ultrasound guidance. Success rate: ~80–90% for pneumatic reduction. Recurrence rate: ~10% — most within 72 hours.
Contraindications to enema reduction:
- Pneumoperitoneum
- Peritonitis
- Hemodynamic instability
Complex or echogenic free fluid on ultrasound = do not attempt enema reduction. This pattern suggests bowel ischemia or perforation. Emergent surgical consultation is required.
After failed reduction: Surgical consultation. Lead point identified at surgery in a higher proportion of failed reductions. Repeat enema attempt (up to 3 attempts) is accepted practice at many centers before surgical referral if no ischemia signs.