Acute psoas abscess in a newborn infant

A 1-month-old neonate was seen for an acute toxic illness, suggestive of septicemia. No obvious focus of infection was present. During attempted femoral venipuncture, purulent material, thought to originate from the right hip joint, was encountered. Because of this aspirate, as well as suggestive local signs, septic arthritis of the right hip was diagnosed. Arthrotomy failed to confirm the diagnosis, and on further surgical exploration a purulent psoas abscess was discovered. The patient made an uneventful recovery, and at follow-up 48 months later was asymptomatic with a normal clinical examination. This case illustrates the difficulty of differentiating acute psoas abscess from septic arthritis of the hip in the neonate.