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Pitfalls in the CT diagnosis of appendicitis

¹ Department of Radiology, University of Medicine in New Jersey, 150 Bergen Street, Newark NJ, USA and ² Department of Radiology, Tel Aviv - Sourasky Medical Center, 6 Weizman Street, Tel Aviv, Israel

View larger version (89K): [in a new window]   Figure 1. (a) Normal air-filled appendix located in the interaortocaval region (arrow). (b) Normal air-filled appendix in the inguinal canal (arrow). (c) Perforated appendicitis in a patient with an appendix located in the inguinal canal (arrow).

View larger version (82K): [in a new window]   Figure 2. (a) A normal appendix (arrow) extends from the base of the caecum inferiorly. (b) Thickening of the abnormal appendiceal tip (arrow) with marked inflammatory changes in the periappendiceal fat. (c) Coronal reformation showing normal appendix (short arrow) with focal inflammation of appendiceal tip (long arrow).

View larger version (84K): [in a new window]   Figure 3. Perforated tip appendicitis. 70-year-old male with right lower quadrant pain. (a) CT demonstrates a round fluid collection mimicking a distended gallbladder (large arrow) with an apparent gall stone within it (small arrow). (b) At a slightly different level the collapsed gallbladder with mucosal enhancement is identified (small arrow) separate but adjacent to the fluid collection (large arrow). (c) The appendix near its origin is normal without inflammatory changes around it (arrow). (d) At a level between the pericholecystic collection and the normal appendicial origin, inflammatory changes begin to be noted surrounding the appendix (arrow). At surgery the retrocaecal appendix extended cephalad with perforated tip appendicitis and abscess formation adjacent to the gallbladder, mimicking complicated cholecystitis.

View larger version (101K): [in a new window]   Figure 4. Stump appendicitis. A 31-year-old male status post-laparoscopic appendectomy who presented with recurrent right lower quadrant pain. Note infiltration of periappendiceal fat (arrow). Surgery confirmed the diagnosis of stump appendicitis.

View larger version (57K): [in a new window]   Figure 5. (a) 67-year-old male with Crohn's disease. The appendix is distended and slightly thickened (curved arrow), but predominantly filled with "clean" air. These findings are consistent with a secondary inflammation of the appendix rather then appendicitis due to obstruction. The appendiceal dilatation and thickening resolved with conservative treatment of the patients underlying disease. (b) 40-year-old male with appendicitis. CT demonstrates a distended appendix with enhancement of the periappendiceal wall and multiple small air bubbles within the lumen (arrow).

View larger version (92K): [in a new window]   Figure 6. False positive diagnosis of appendicitis in a 50-year-old male with abdominal pain. Contrast administered only per rectum. Note apparent focal thickening of base of caecum (black arrow), with tubular thickened structure appearing to extend from it (large white arrow), separate from terminal ileum (not shown). Surgery demonstrated no evidence of appendicitis. Use of oral contrast medium may have prevented this false positive diagnosis.

View larger version (132K): [in a new window]   Figure 7. Abnormal enhancement of appendix. 52-year-old male with diffuse abdominal pain. Use of intravenous contrast medium with enhancement of appendiceal mucosa helps differentiate appendix (straight arrow) from loops of small bowel (curved arrow). Appendicitis was confirmed at surgery.

View larger version (121K): [in a new window]   Figure 8. Perforated appendicitis. An 18-year-old female with right lower quadrant pain, fever and leucocytosis. CT demonstrates an enlarged right ovary (large arrow) with small cystic areas in it, adjacent fluid (small arrow) and extrinsic inflammation of the adjacent mesenteric fat (arrowhead). A CT diagnosis of tubo-ovarian abscess or pelvic inflammatory disease was entertained. However, the surgical diagnosis was perforated appendicitis, abscess formation and secondary oedema of the right ovary.

View larger version (103K): [in a new window]   Figure 9. Elderly female with diffuse abdominal pain. CT demonstrates dilated contrast filled small bowel loops (large arrow) with collapse of the right and left colon (small arrows) suggestive of small bowel obstruction. Surgery demonstrated appendicitis. However, an inflamed appendix could not be identified on CT even retrospectively.

View larger version (52K): [in a new window]   Figure 10. (a) 30-year-old male. CT demonstrates typical focal thickening of the caecum (arrow) with an appendicolith noted in its centre. (b) A patient with long history of Crohn's disease. CT demonstrates a concentric thickening of the caecum (large arrow), atypical for appendicitis.

View larger version (46K): [in a new window]   Figure 11. (a) 83-year-old male with acute onset of right lower quadrant pain. CT demonstrates marked concentric caecal thickening (arrow). (b) CT images slightly caudal demonstrates a dilated fluid filled appendix with an enhancing appendiceal wall consistent with appendicitis. Due to the nature of the caecal thickening, caecal carcinoma with obstruction and secondary appendicitis was diagnosed. Both findings were confirmed at surgery.

View larger version (127K): [in a new window]   Figure 12. Submucosal fat deposition in Crohn's. A concentrically thickened caecum (arrow) is noted. The wall of the thickened bowel is uniformly low in attenuation due to submucosal fat typical of Crohn's disease.

View larger version (69K): [in a new window]   Figure 13. Caecal diverticulitis. (a) Inflammatory changes surrounding caecum and appendix (large arrow). Note that although the appendiceal wall is thickened, "clean" air is noted within it (small arrow). (b) CT image slightly superior to (a) demonstrates similar changes adjacent to an inflamed diverticulum (arrow). Note that the diverticulum rather then the appendix is situated at the centre of the changes.

View larger version (46K): [in a new window]   Figure 14. (a) Mucocele. Note fluid-filled distended appendix (arrow), typical of a mucocele, in this asymptomatic patient. (b) Appendicitis. A distended fluid-filled appendix is noted (arrow), without inflammatory changes, similar to the appearance of a mucocele. However, this patient had typical symptoms of appendicitis.

View larger version (120K): [in a new window]   Figure 15. Endometriosis involving the appendix. CT demonstrates an enhancing thick-walled appendix (arrow). Surgery demonstrated multiple endometrial deposits, including appendiceal involvement.