Retro-psoas appendicitis.

The vermiform appendix (VA) is known to exhibit a wide range of anatomic variability, with clinical presentation correlating with certain known anatomic positioning. To the best of our knowledge, we describe the second known case of a retro-psoas muscle VA variant and the first known case of appendicitis in such a location. Retroperitoneal access was obtained, and the appendix was freed from the intermuscular recess between the psoas and iliacus. The peritoneal defect was primarily repaired, and the patient was discharged on postoperative day 1 in good condition.