Kelynack first described diverticulosis of the vermiform appendix in 1893. Since that time, many others have proposed theories on the pathogenesis of the diverticula. As with all intestinal diverticula, those found in the appendix can be classified as congenital or acquired.
In the congenital diverticulum, all layers of the bowel wall are present. This is extremely rare, with fewer than 50 cases reported world-wide. Favara suggested a chromosomal basis for this lesion. In reviewing eight patients with multiple congenital appendiceal diverticula, seven were infants born with trisomy D 13-15 syndrome. Other suggested mechanisms include appendiceal duplication, local sacculations formed during appendiceal recanalization, epithelial inclusion in the appendiceal wall, and traction.
The wall of the diverticulum in the acquired cases contains only mucosa, submucosa, and serosa. Trollope and Lindenauer published a collective review in 1974 of the 1,373 known cases along with a discussion of the most common theories of pathogenesis. The first theory involves a post-appendicitis weakness of the bowel wall, leading to ulceration and secondarily regenerated epithelium over the injured area. Stout reported the most likely noninflammatory theory in 1923. He believed that appendiceal diverticula could be formed by a combination of luminal obstruction and active muscular contraction. The obstruction, coupled with the 1 to 2 mL of appendiceal secretions that are produced daily, is augmented by contractions of the appendix in an effort to empty itself; the result is a high enough pressure to cause diverticular formation or perforation. It is likely that in most cases multiple factors lead to the development of acquired appendiceal diverticulosis.
Progression from diverticulosis to diverticulitis follows a partial or complete obstruction of the lumen. This may be due to swelling of the mucosa, inflammation, fecaliths, fibrous strictures, or torsion.[10,11,12] In the pre-antibiotic era, most of these patients had a preoperative diagnosis of chronic appendicitis. The pain is often described as insidious in nature, intermittent, and extended over a long period. Low-grade fever and leukocytosis are commonly found. Anorexia, nausea, and vomiting are usually absent. Most of the patients have had one or more admissions before the operative admission.
Appendiceal diverticulitis is an uncommon problem. It is also clear that the incidence is greater than that generally appreciated. Since Trollope and Lindenauer's original 1,373 cases 2 were reported, an additional 294 cases 13-24 have been discussed in the English language literature. The average age of the appendiceal diverticulitis patient is 37 years compared with 19 years in cases of appendicitis. Both the congenital and the acquired types are more common in men. Nearly all appendiceal diverticula are of the acquired type. Due to the thinned wall, these diverticula are prone to perforate early in the presence of acute inflammation. Grossly, the proximal appendix usually appears normal but plunges into an inflamed mass covered with fibrinous exudate. Nearly 60% of the diverticula are located in the distal third of the appendix.
In a comparison of acute diverticulitis to acute appendicitis, perforation was found to be more than four times as likely in the diverticulitis group at 66%. Another reported complication of appendiceal diverticulosis is hemorrhage requiring several units of blood transfusion. In addition, multiple cases of pseudomyxoma peritonei have been reported from appendiceal diverticula.[27,28]
The patients most likely to have appendiceal diverticulitis are those with cystic fibrosis. In these patients, the diverticula arise at the site of a penetrating artery. Most of the patients are adolescents, and their age averages 13 years. The total incidence of appendiceal diverticulosis in cystic fibrosis patients from autopsy data is 14%. For cystic fibrosis patients with abdominal surgery excluding laparotomy for meconium ileus, this rises to a 43% incidence.
No current diagnostic radiographic evaluations are available for appendiceal diverticulosis. Due to the likelihood of complications, diverticulosis of the appendix is a finding that radiologists stress. Computed tomography has become an increasingly popular tool for cases of nonspecific right lower quadrant abdominal pain, and in most cases it can be used to determine if the condition is a surgical or nonsurgical problem. Computed tomography findings in cases of appendicitis can include appendiceal swelling, pericecal inflammation, abscess, phlegmon, and increased density in the pericecal fat. In the case of our patient, the CT image shows a large pericecal phlegmon without evidence of abscess formation. It does not clearly identify the appendiceal diverticulum.
Treatment of appendiceal diverticulitis can be appendectomy, cecectomy, or right hemicolectomy, depending on intraoperative findings. If the induration extends onto the cecum, it may be difficult to differentiate the inflammatory mass of diverticulitis from that of a tumor. In one case, a laparoscopic appendectomy for appendiceal diverticulitis was safely completed without difficulties.
South Med J. 2000;93(1) © 2000 Lippincott Williams & Wilkins
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