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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.
