A

A psoas abscess typically produces a flank/lumbar swelling, the hip is held in flexion and pain worsens when the hip is passively extended (psoas stretch). It often arises secondarily from spinal tuberculosis, so vertebral changes on X-ray are common. These features match the presentation far better than pyonephrosis, a retrocecal appendicular mass, or testicular torsion [Smith 1982, PMID 7161686; Masavkar 2012, PMID 23259114].