Although perforated appendicitis is a well-established cause of retroperitoneal abscess
formation, (2) the absence of abdominal or flank pain, as well as extension into the thigh as seen with this case, is rare.
An early ultrasound and drainage in this case may have prevented fistulation of the retroperitoneal abscess through the abdominal wall.
Occult retroperitoneal abscess presenting as septic arthritis of the hip.
Drainage of a retroperitoneal abscess
was performed with culture: Fusobacterium varium and Bacteroides ovatus , and antibiotics were prescribed.
Key Words: computed axial tomography, retroperitoneal abscess
Retroperitoneal abscess is a relatively rare condition and is often misdiagnosed or suspected late in its clinical course.
3] Knowing that the anatomical position of the appendix is variable and 65% of the appendix have been reported to be retrocecal,  a perforation at this location is fraught with danger of retroperitoneal abscess
CT findings of duodenal perforation include extraluminal air, segmental duodenal wall thickening, periduodenal fat stranding, collection of extraluminal air bubbles in the right perirenal space, focal defect in the bowel wall with oral contrast extravasation and retroperitoneal abscess