Differential diagnoses are acute appendicitis with abscess formation and right colon diverticulitis. In our opinion, the differenitial points of appendiceal diverticulitis from periappendiceal abscess are direct continuation of the appendiceal mucosa and submucosa to the diverticulum, multiplicity and relatively well-margined round or oval shape. The differentiation from the right colon diverticulitis is possible by direct visualization of the diverticula from the appendix and not from the right colon (Fig. 6). In addition, diverticulitis of the appendix does not show colonic wall-thickening which is seen in right colon diverticulitis. Furthermore, right colonic diverticulitis show frequent visualization of the fecalith which makes posterior shadowing(5), while, diverticulitis of the appendix did not shows it in our study.

Diverticulitis of the Appendix: Sonographic EvaluationKwan Seop Lee MD, Jae Young Lee MD, Hyun Beom Kim MD, Ihn Jae Lee MD, Dae Hyun Hwang MD, Yul Lee MD, Shang Hoon Bae MD, 1Ki Taek Chang MD.

The Department of Radiology, 1Pathology, Hallym University College of Medicine

Discussion

The incidence of diverticula found in appendectomies has been reported as ranging from 0.004 to 2.1 percent (1). This striking variability of frequency (1-3) is greatly influenced by the awareness, interest and effort with which they were sought. Their frequent small size, their usual location along the mesenteric border where they may be buried in the adipose tissue are factors which contribute to making their detection difficult (3). Appendiceal diverticula are classified into two types: the congenital and acquired. Congenital diverticula are extremely rare and all layers of the wall of the appendix are present. Acquired diverticula are far more common, of which the muscular layer is absent. They contain only mucosa, submucosa and serosa in their wall with abrupt interruption of the muscular layer. The sonographic findings of diverticulitis of the appendix were characteristic in our study (Fig. 1-5). On transverse section, protruded hypoechoic sac which was continous from the lumen of the appendix was seen with focal disruption of the wall of the appendix. On longitudinal view, hypoechoic sacs in the inflamed hyperechoic omentum were seen. The omentum was hypertrophied due to inflammation when the diverticulitis was protruded to the mesenteric side. All cases showed absent muscular layer in the wall on sonography, which was confirmed as acquired diverticula. In our study, protrusion to the mesenteric border was the most common site. On color sonography, all cases showed increased color flow in the wall of the diverticulitis or surrounding omentum due to inflammation. Clinically the diverticulitis of the appendix is known to be more likely to perforate than acute appendicitis. And the association with the mucocele or pseudomyxoma peritonei was 20 percent in the report of Collins. These data would seem to indicate that diverticulitis of the appendix is a disease entity that the radiologist should stress.

Results

All nine patients were proven by pathologic confirmation. The final pathologic diagnosis was acute appendicitis with diverticulitis. The mean age of the patients were 55 years. The incidence was 2.7 %(9/335). Sonographic findings were as follows: On transverse section, protrusion of round hypoechoic sac from the lumen of the appendix to the mesenteric or antimesenteric side with focal disruption of the wall of the appendix was noted. On longitudinal section, round hypoechoic sacs in the mesentery of appendix were seen. Seven patients were multiple diverticuli and two were single diverticulum. The total numbers of the diverticulum were 31 and mean numbers were 3.4(31/9). The number of protruded diverticulum to the mesenteric side was 27(87%); to the tip, 3(10%) ;and to the antimesenteric side, 1(3%). The size was from a mere slit to 10 mm in diameter.

Diverticulosis of the appendix is uncommonly seen on barium studies as an incidental findings. The diagnosis is seldom made before operation, and may not even be recognized by the surgeon at the time of operation. After the introduction of the sonographic diagnosis of the acute appendicitis using graded compression technique, numerous reports about the usefulness of the sonography in the evaluation of the acute appendicitis have been described. However, to the best of our knowledge, the sonographic findings of diverticulitis of the appendix are not described in the English literature. During last 13 months, We encountered nine cases of diverticulitis of the appendix combined with acute appendicitis, which was diagnosed by sonography preoperatively. The purpose of this study is to describe the sonographic findings of diverticulitis of the appendix and to call attention and by so doing aid in its recognition at the time of sonography.

Introduction

From March 2000 to March 2001, we performed appendix sonography in 764 patients and 335 patients proved to have acute appendicitis pathologically. Nine of the 335 patients, preoperative diagnosis was diverticulitis of the appendix combined with acute appendicitis. Sonogrphic examination of the appendix was performed with 5-8 MHz curved array (22.5 mm) and 5-12 MHz linear array transducers on commercially available equipment (HDI 5000; Advanced Technology Laboratories, Bothell, WA, USA). Postoperative surgical specimen sonography was performed with the specimen put either in the water or US gel. We used 5-12 MHz linear array transducer in the surgical specimen sonography. Cutting of the pathologic specimen was done by transverse section of the appendix.

Materials and Methods

Fig. 1.

A. Transverse(TR) view of the appendix: Protrusion of the hypoechoic sac (arrow) from the lumen of the appendix is noted.

B. Cross section specimen of the appendix: Small diverticulum (arrow) is connected with appendiceal lumen. Muscular layer of the appendix wall is abruptly interrupted.

A

B

A. US(TR view): Protruded hypoechoic sac (arrow) to the mesenteric side is seen.

B. Specimen US: Protrusion of hypoechoic sac (arrow) to the mesenteric side with abrupt interruption of the muscular layer.

C. Microscopic view: The mucosa (arrow) of diverticulum is preserved compared to ordinary lumen (double arrows) of appendix.

A. US (TR view) : Protruded large hypoechoic sac (arrow) which is continuous from the lumen of the appendix is noted. The protrusion is to the mesenteric side and hypertrophied omentum is noted.

B. Color US: Increased color flow in the wall of the appendix and diverticulum and inflammed mesentery.

C. Specimen US: same findings with Fig. 3-A. D. US (LO view):Two diverticula (arrows) protruded to the mesenteric

side combined with acute appendicitis. *LO=longitudinalE. Specimen US(LO view): Visualization of diverticula (arrows)

continuous from the lumen of the appendix are well seen. F. US (LO view): A diverticulum (arrow) protruded to the tip of the

appendix. G. Specimen US: The continuation of the mucosa (short arrows) and

submucosa (*) to the diverticulum with abrupt interruption of the muscular layer (long arrow) is well noted.

B CA

E

G

D

F

* **

Fig. 3.

A. US(LO view): Three hypoechoic sacs (arrows) in the hypertrophied omentum are seen when the angle of the ultrasound tilted to the mesenteric side.

B. Specimen US: The small diverticula has echogenic mucosal layer. C. LO view of the gross specimen: Three diverticula seen on Fig. A,B

along the mesenteric border are seen. Another diverticulum is seen in the tip (open arrow).

D. E. US, specimen US (TR view): No visible mucosa in the diverticulum (arrow) due to sevre inflammation.

F. Gross specimen (cross section) : The mucosa is not seen due to severe diverticulitis.

A B

Fig. 4.

C

D E F

A. US(TR view): Clear visualization of the echogenic mucosa (arrows) in the diverticulum is noted.

B. Color US: Prominent color flow (arrow) in the wall of the diverticulum and mild color flow in the wall of the appendix are seen.

C. Specimen US: same image with A&B. D. Cross section of the gross specimen: Arrow indicates

diverticulum. E. Microscopic view (cross section): Abrupt interruption of the

muscular layer (arrows) of the appendix wall at the site of the diverticulum is well documented.

F. Gross specimen: Several diverticula along the mesenerteric (long arrows) and antimesenteric borders (short arrow). *dotted line: imaginary cross section of the A-E.

Fig. 5.

A B C

D E F

References1. Trollope ML, Lindenauer SM. Diverticulosis of the Appendix: A Collective Review. Dis. Colon Rectum 1974;

17:200-218.2. Lipton S, Estrin J, Glasser I. Diverticular Disease of the Appendix. Urg Gynecol Obstet 1989;168:13-16.3. Esparza AR, Pan CM. Diverticulosis of the Appendix. Surgery 1970;67:922-928.4. Oudenhoven LFIJ, Koumans RKJ, Puylaert JBCM. Right Colon Diverticulitis: US and CT Findings – New

Insights about Frequency and Natural History. Radiology 1998;208:611-618.

Conclusion

Diverticulitis of the appendix has characteristic sonographic findings. Understanding of the sonographic findings and increased awareness of the radiologist to this disease will make the preoperative diagnosis possible and help the surgeon and pathologist in search for and discovery of this rare entity.

CBA

Fig. 2.

Fig. 6. A. Diverticulitis of the ascending colon: strong clear acoustic shadowing due to fecalith (long arrow). Colonic wall thickening (short arrows) B. Cecal diverticulitis (thin arrows) and normal appendix (thick arrows).A B

colon

cecum