Case Presentation: A previously healthy 15-year-old M presented for 2-week history of fevers and painless right-sided limp noticed by parents. He was evaluated at an outside hospital three times in the week prior to presentation at Tufts, and ultimately diagnosed with tendonitis. Although he denied hip pain, he endorsed right-sided anterior thigh pain. Denied trauma, numbness, paresthesia, or weakness of lower extremities. Despite this, he was able to play soccer and was participating at practice just prior to being seen in the ED. Exam revealed full and painless passive/active range of motion of right lower extremity with ability to bear weight. He intermittently demonstrated gait abnormality on serial exams.Due to gait abnormality, initial workup focused on orthopedic etiologies of limp, but x-ray of hips and overall exam were reassuring.Labs obtained on arrival revealed marked leukocytosis and elevated inflammatory markers. MRI of the lumbar spine was obtained and revealed a 2.8 x 1.9 cm abscess anterior to the right iliopsoas muscle. Because there are isolated cases of iliopsoas abscess formation associated with appendicitis, ultrasound of abdomen was obtained, showing the appendix was borderline in size and fluid-filled, possibly representing appendicitis. Due to the location of the abscess, it was deemed to be unamenable to drainage. He was started on IV Zosyn as the antibiotic of choice and demonstrated down-trending inflammatory markers and leukocytosis. Prior to discharge, was started on oral antibiotics (Ciprofloxacin and Linezolid) with plans to undergo interval appendectomy 2 weeks after discharge.
Discussion: An iliopsoas abscess is a rare diagnosis and is reported to have a worldwide incidence of 12 new cases per year. The pathogenesis of abscess formation is divided into primary and secondary form, with the primary form being more common. The patient in this report developed an iliopsoas abscess due to a secondary form of infection—a ruptured appendix. However, he denied classical signs and symptoms of appendicitis, such as periumbilical/right lower quadrant pain or nausea/vomiting. His physical exam was consistently negative for McBurney’s sign or any abdominal tenderness.
Conclusions: The diagnosis of iliopsoas abscess is rare, and symptoms may be nonspecific. However, must be considered in patients presenting with prolonged fevers and pain radiating to the pelvis or hip. Patients may not present with classical symptoms of appendicitis, and may undergo appendiceal rupture without recognition, placing them at increased risk of developing an iliopsoas abscess.
