Appendiceal intussusception happens when appendix segment is pulled into itself or into the cecum. This condition can mimic various chronic and acute abdominal conditions. It is an important entity to recognize since it could be mistaken for a cecal mass.
Appendiceal intussusception is a rare condition, with an estimated incidence of 0.01% of patients who underwent appendectomy .
Symptoms of appendiceal intussusception have been divided into four groups:
- asymptomatic patients
- symptoms similar to acute appendicitis
- symptoms consistent with intestinal intussusception: abdominal pain and vomiting occur for several days; bowel movements may be normal, or less frequently, there is constipation, diarrhea or melena
- a prolonged history of intermittent severe attacks of right lower quadrant abdominal pain. Vomiting and melena may be present
The diagnosis is rarely made preoperatively because of its variable presentation and unspecific symptoms.
Appendiceal intussusception can occur without any underlying abnormality. Anatomical variations of the appendix and pathological conditions such as tumors or polyps, endometriosis, parasitism, cystic fibrosis, appendicoliths and foreign bodies, have all been described as possible causes.
In most cases the radiographic findings are normal. When there is associated small bowel obstruction, abdominal radiographs can demonstrate features thereof (i.e. dilated small bowel loops with air-fluid levels).
Ultrasonography has a role, especially in children. Longitudinal sonograms may show the inverted appendix protruding into the cecal lumen.
Similar findings to the intestinal intussusception can be seen, which include:
- target sign (also known as the doughnut sign)
- pseudokidney sign
- crescent in a doughnut sign
CT is the most commonly used diagnostic modality. A CT scan can clearly show the appendix invaginated into the cecal lumen (see case 1).
The appearance of bowel-within-bowel, which identifies the appendix surrounded by the cecum, can be seen.
On imaging, differential considerations include
- cecal tumor
- ileocecal intussusception