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Appendicitis: spectrum of appearances on helical CT

University Departments of ¹ Radiology and ² Surgery, Addenbrooke's NHS Trust and the University of Cambridge, Hills Road, Cambridge CB2 2QQ, UK

View larger version (107K): [in a new window]   Figure 1. Normal appendix. Non-distended, thin walled, retrocaecal appendix with normal surrounding fat (arrows). Note caecum (c), right common iliac vessels (v), ureter (u) and psoas muscle (p).

View larger version (91K): [in a new window]   Figure 2. Typical appendicitis. 22-year-old man with intermittent abdominal pain and several admissions for possible appendicitis. CT with intravenous contrast medium shows a dilated appendix with an enhancing thickened wall (arrow).

View larger version (110K): [in a new window]   Figure 3. Appendicolith with inflammation. 53-year-old man with 3-day history of right iliac fossa pain, clinically not thought to be appendicitis. CT shows an appendicolith with peri-appendiceal fat stranding (arrow).

View larger version (147K): [in a new window]   Figure 4. Appendicolith without inflammation. 12-year-old boy with three episodes of right iliac fossa pain in 4 months. Each episode settled with conservative treatment. CT shows an appendicolith without peri-appendiceal inflammation (arrow). Nevertheless, surgery and histology confirmed appendicitis.

View larger version (139K): [in a new window]   Figure 5. Lateral conal fascial thickening. 60-year-old man with 4-day history of peri-umbilical pain radiating to the right iliac fossa. CT with intravenous contrast medium shows a distended retrocaecal appendix with an enhancing wall (single arrow), together with thickening of the lateral conal fascia (paired arrows). c, caecum.

View larger version (121K): [in a new window]   Figure 6. "Arrowhead" sign. 64-year-old man with 3-day history of colicky lower abdominal pain and right iliac fossa tenderness. CT shows an "arrowhead" sign (arrow) with peri-appendiceal inflammation. The arrowhead sign results from the accumulation of gastrointestinal contrast medium between a symmetrically thickened caecal apex; the intraluminal collection of contrast "points" at the occluded orifice of the appendix.

View larger version (85K): [in a new window]   Figure 7. Inflammatory mass. 37-year-old man with a 2-day history of right iliac fossa pain and two similar episodes 1 month and 1 year previously. CT following intravenous contrast medium shows a dilated appendix with a thickened enhancing wall (arrow) and an inflammatory mass. Note that the mass abuts the right psoas muscle (p).

View larger version (60K): [in a new window]   Figure 8. Inflammatory mass displacing adjacent structures. Same patient as Figure 6. CT shows (a) fascial thickening in right paracolic gutter (arrows) and (b) inflammatory mass (arrows) surrounding an inflammed appendix, displacing bladder, labelled b, to the left.

View larger version (54K): [in a new window]   Figure 9. Progression of inflammatory mass to an abscess collection. 17-year-old man with 2 days of vomiting and mild lower abdominal pain. (a) CT with intravenous (iv) contrast medium on admission shows a 4 cm phlegmonous soft tissue mass with surrounding fat stranding (arrow). Initial management plan was for antibiotic therapy to be followed by interval appendicectomy. (b) CT with iv contrast medium 9 days later, obtained because of clinical deterioration, shows a liquefied right iliac fossa abscess (arrow) with a locule of gas.

View larger version (114K): [in a new window]   Figure 10. Involvement of the psoas muscle. 6-year-old boy with a 6-day history of vomiting and intermittent pyrexia initially considered to be a viral infection. Pain subsequently localized to the right iliac fossa. Ultrasound examination was indeterminate. CT with intravenous contrast medium shows a distended appendix with a thick enhancing wall (single arrow) together with inflammatory involvement (paired arrows) of the right psoas muscle (p) (compare with left psoas muscle). A retrocaecal appendicitis and a psoas abscess were confirmed at surgery.

View larger version (98K): [in a new window]   Figure 11. Intra-abdominal abscesses. 32-year-old man with a 1-week history of diffuse abdominal pain, distension and vomiting. CT with intravenous contrast medium shows a large abscess collection with an enhancing wall in the rectovesical pouch, containing small locules of gas (arrow) (r, rectum; b, bladder). There were further collections posterior to the ascending colon and caecum, and anterior to the sigmoid colon (not shown). The walls of the caecum and the proximal ascending colon were also thickened, but the appendix was not identified at CT. Surgery revealed a perforated appendix and confirmed the large pelvic collection.

View larger version (63K): [in a new window]   Figure 12. Perforation and collections in unusual locations. Same patient as Figure 3. CT with intravenous contrast medium shows (a) collection in the left subhepatic space (arrow), anterior to the stomach (s) and (b) free intraperitoneal gas anterior to and posterior to the liver, and in the falciform fissure (arrows).

View larger version (98K): [in a new window]   Figure 13. Mucocele of the appendix mimicking appendicitis. 75-year-old man. CT shows a distended appendix without peri-appendiceal inflammation (arrows). Histopathology showed a distended appendix containing a mucus-secreting adenoma with no evidence of acute inflammation.