Appendiceal diverticulitis is inflammation of a diverticulum (mucosal herniation) in the appendiceal wall. Appendiceal diverticulum is rare (0.004-2.1%) and usually incidentally detected; however, when inflamed, it mimics acute appendicitis. Characterized on CT by a focal outpouching extending from the appendiceal wall, localized periappendiceal stranding, and wall thickening. Perforation risk is 4 times higher than acute appendicitis.
Age Range
20-70
Peak Age
40
Gender
Male predominant
Prevalence
Rare
Appendiceal diverticulum may be congenital (true diverticulum — involves all wall layers) or acquired (false diverticulum — herniation of mucosa and submucosa). The acquired form is more common, resulting from herniation of mucosa through weak points in the muscularis propria (vascular penetration sites) due to increased intraluminal pressure. Diverticular inflammation begins with fecalith impaction and affects a focal wall segment unlike acute appendicitis. Because the diverticular wall is thin (lacking muscularis propria), perforation risk is high — increasing the clinical significance on CT. Inflammation creates localized periappendiceal stranding around the diverticulum; diffuse stranding suggests acute appendicitis while focal stranding suggests diverticulitis.
On CT, a focal outpouching (diverticulum) extending from the appendiceal wall with localized fat stranding around the diverticulum and focal wall thickening is the diagnostic finding of appendiceal diverticulitis. Relatively normal appendiceal lumen outside the diverticulum is the critical clue in differential diagnosis from acute appendicitis.
Focal outpouching extending from the appendiceal wall (diverticulum) is the fundamental diagnostic finding. The diverticulum typically measures 3-10 mm and has a round or oval shape. Its wall is thin, forming a boundary with surrounding tissues.
Report Sentence
A ... mm focal outpouching (diverticulum) extending from the appendiceal wall is identified.
Localized fat stranding is seen around the diverticulum. This stranding is focal not diffuse, indicating inflammation is limited to the diverticulum. Unlike the diffuse periappendiceal stranding in acute appendicitis, stranding is asymmetric and localized to one side.
Report Sentence
Localized fat stranding around the diverticulum is noted, consistent with appendiceal diverticulitis.
Appendiceal wall thickening is localized and asymmetric to the side containing the diverticulum. The opposite wall may be normal or mildly thickened. This asymmetry differs from the diffuse symmetric thickening in acute appendicitis.
Report Sentence
Focal asymmetric thickening of the appendiceal wall at the diverticulum location is noted.
Calcified fecalith within the diverticulum is localized outside the appendiceal lumen in an extramural pocket. This finding proves the existence of the diverticulum and is distinguished from intraluminal appendicolith by its extraluminal position.
Report Sentence
Calcified fecalith is noted within an extramural appendiceal diverticulum.
The appendiceal lumen outside the diverticulum may be normal or mildly dilated. Absence of diffuse dilatation throughout the lumen is important in differential diagnosis from acute appendicitis.
Report Sentence
The appendiceal lumen is of normal caliber outside the diverticulum without diffuse dilatation.
On ultrasound, a focal outpouching extending from the appendiceal wall (diverticulum) is seen on the lateral surface of the tubular structure showing hypoechoic or mixed echogenicity. Hyperechoic fecalith or internal echoes may be seen within the diverticulum. Graded compression technique can distinguish the diverticulum from surrounding fat tissue.
Report Sentence
A focal outpouching (diverticulum) extending from the appendiceal wall with localized surrounding hyperemia on ultrasound is consistent with appendiceal diverticulitis.
Criteria
Involves all wall layers (mucosa, submucosa, muscularis); usually solitary and larger
Distinct Features
Thicker-walled with lower perforation risk. Wall thickness is measurable on CT and muscularis layer can be distinguished.
Criteria
Only mucosa and submucosa herniation; muscularis layer lacking; usually multiple and smaller
Distinct Features
Thin-walled with much higher perforation risk (66% vs 14%). Wall appears very thin on CT and perforation findings should be carefully sought.
Distinguishing Feature
Acute appendicitis shows diffuse appendiceal dilatation, symmetric wall thickening, and circumferential periappendiceal stranding; diverticulitis shows focal outpouching, asymmetric thickening, and localized stranding
Distinguishing Feature
Perforation shows wall defect, extraluminal air, and diffuse free fluid; diverticulitis preserves the diverticular structure and free air is usually absent (except perforated diverticulitis)
Distinguishing Feature
Carcinoid tumor shows solid enhancing intraluminal nodule; diverticulitis lacks solid nodule, showing outpouching filled with fluid/fecalith
Urgency
urgentManagement
surgicalBiopsy
Not NeededFollow-up
specialist-referralAppendiceal diverticulitis requires surgical treatment because perforation risk is 4 times higher than acute appendicitis (66% vs 17%). Laparoscopic appendectomy is standard treatment. Correct identification of diverticulitis on CT is important because failure rate of conservative (antibiotic) therapy is high. Associated neoplasia should be investigated on pathological examination (in 20-33% of cases) because a known association exists between appendiceal diverticulum and appendiceal neoplasms. Colonoscopy is recommended in patients >40 years.
Treatment of appendiceal diverticulitis is surgical appendectomy. Early surgery is recommended as perforation risk is 4 times higher than acute appendicitis. Diagnosis is usually made intraoperatively or at pathological examination. When appendiceal diverticulum is found, careful pathological examination is needed for associated neuroendocrine tumor.