Appendiceal intussusception is a rare condition characterized by invagination of the appendix into the cecal lumen. Lead points include lymphoid hyperplasia, mucocele, endometriosis, adenoma, carcinoid tumor, or inverted appendiceal stump. In children, it is usually caused by lymphoid hyperplasia, while neoplastic lead points are more common in adults. Clinically, it may present with right lower quadrant pain, intermittent colic, hematochezia, or be incidentally detected. On imaging, it appears as a target sign or sausage-shaped mass within the cecal lumen.
Age Range
10-60
Peak Age
35
Gender
Equal
Prevalence
Appendiceal intussusception occurs when the proximal segment of the appendix telescopes into the lumen of the distal segment or cecum. A lead point is required for this mechanism — the lead point is pulled by peristaltic movements and drags the remaining appendix behind it. In children, the most common lead point is lymphoid hyperplasia; in adults, mucocele, endometriosis, carcinoid tumor, or adenoma commonly underlie it. During invagination, the mesoappendix is also drawn into the cecum, and vessels in the mesoappendix are stretched/compressed — this can lead to venous stasis, edema, and ischemia. On imaging, the invaginated appendix creates concentric layers within the cecal lumen (intussusceptum — invaginated segment, intussuscipiens — receiving cecum), producing a target sign. Fat tissue in the invaginated mesoappendix appears as low density on CT, creating the bull's-eye sign within the cecal lumen.
Bull's-eye sign in axial section within the cecal lumen consisting of concentric soft tissue and fat density layers. Invaginated appendiceal wall (soft tissue) and mesoappendix (fat) form alternating rings. Considered pathognomonic for appendiceal intussusception.
Target sign consisting of concentric layers within the cecal lumen. Invaginated appendiceal wall (soft tissue density) and dragged mesoappendix fat (negative density) form alternating layers. Bull's-eye appearance on axial sections is typical.
Report Sentence
Target sign consisting of concentric soft tissue and fat density layers is observed within the cecal lumen, compatible with appendiceal intussusception.
Sausage-shaped intraluminal mass in the cecal lumen with its long axis extending along the cecum on coronal and sagittal reformations. Reflects the longitudinal appearance of the invaginated appendix. Lead point lesion may be seen at the distal end of the mass.
Report Sentence
A sausage-shaped intraluminal mass measuring __ mm in length is observed in the cecal lumen on coronal reformation.
Appendix is not visualized at normal anatomical location; instead, invaginated appendiceal mass is seen within the cecal lumen. Invagination point (entry point) at the appendiceal base on the medial wall of the cecum may be detected.
Report Sentence
The appendix is not identified at normal anatomical location; appendiceal intussusception is considered in conjunction with the mass within the cecal lumen.
Target sign consisting of concentric hypoechoic and hyperechoic layers within the cecal lumen on ultrasonography. Invaginated appendiceal wall appears hypoechoic, dragged mesoappendix fat appears hyperechoic. Oscillation with peristaltic movements may be seen on real-time evaluation.
Report Sentence
Target sign consisting of concentric layers is observed in the cecal lumen, compatible with appendiceal intussusception.
Mesoappendix fat tissue drawn into the cecal lumen along with the invaginated appendix. Negative density fat areas are seen within the mass in the cecal lumen — pathognomonic finding on CT.
Report Sentence
Negative density areas corresponding to mesoappendix fat tissue are observed within the intraluminal mass in the cecal lumen.
Criteria
The entire appendix has invaginated into the cecal lumen. The appendiceal base has also been drawn into the cecum.
Distinct Features
Appendix not seen at normal location on CT. Large intraluminal mass within the cecum. Higher risk of ischemia and necrosis — may require emergent surgery.
Criteria
Part of the appendix (usually the tip) has invaginated into the cecal lumen. The appendiceal base is at normal location.
Distinct Features
Appendiceal base in normal position, but invagination at the appendiceal tip. Smaller intraluminal mass. Higher likelihood of spontaneous reduction.
Distinguishing Feature
Lymphoid hyperplasia shows in situ appendiceal thickening without invagination into the cecum. Intussusception shows invaginated appendix with target sign within the cecal lumen.
Distinguishing Feature
Mucocele shows cystic dilatation at the appendiceal location without invagination into the cecal lumen. Intussusception shows target sign with solid mass and fat tissue within the cecal lumen.
Distinguishing Feature
Lipoma is a well-defined fat-density mass in the appendiceal wall that may serve as a lead point for intussusception; however, isolated lipoma has no invagination. In intussusception, lipoma lead point is seen together with intracecal target sign.
Urgency
urgentManagement
surgicalBiopsy
Not NeededFollow-up
specialist-referralAppendiceal intussusception requires surgical evaluation. Emergent surgery is indicated if there are findings of ischemia or necrosis (loss of wall enhancement, pneumatosis, periappendiceal free fluid). Lead point should be investigated in adults — broader resection (right hemicolectomy) may be needed in the presence of neoplastic lead point (carcinoid, adenoma, mucocele). In children, it is usually caused by lymphoid hyperplasia with possible spontaneous reduction; however, surgical consultation is recommended. Colonoscopic reduction may be attempted in some cases; however, caution is needed due to perforation risk. Preoperative CT should be used for lead point investigation, ischemia assessment, and surgical planning.
Appendiceal intussusception is rare but clinically important as it may mask underlying pathology (mucocele, neoplasm, endometriosis). Surgical treatment (appendectomy or right hemicolectomy) is required. It may be misinterpreted as a polyp on colonoscopy — CT is critical for diagnosis. Intraoperative frozen section is important to evaluate for underlying neoplasia.