A Case of Psoas Muscle Abscess With Hematuria, Detected Initially by Point-of-Care Ultrasound in the Emergency Department

Abstract

Background: Psoas muscle abscess (PMA) is a collection of pus in the psoas muscle. It is considered a rare clinical entity and is often misdiagnosed due to highly vague symptoms. We report that point-of-care ultrasound (POCUS) serves as a useful and noninvasive tool for early detection of PMA.

Case report: Our patient was a 35-year-old man without any past medical illness who visited the emergency department due to right lower back pain and hematuria for 8 months. He denied fever, trauma, or recreational drug use. On arrival, the patient's vital signs were stable and had no fever. Laboratory tests showed white blood cell count 12,800/μL with neutrophil segment 83.2%, C-reactive protein 0.2 mg/dL, and normal renal function. Urine routine showed red blood cells > 100/high-power field. Kidney-ureter-bladder radiograph revealed a positive psoas sign on the right. POCUS showed a mixed echogenic mass adjacent to the right kidney. Subsequently, contrast abdominal computed tomography revealed T10-T11 collapsed vertebral bodies with disc erosion and right psoas muscle abscess at the right kidney level. The patient received open drainage of psoas muscle abscess and T11-T12 laminectomy. He was discharged 13 days post admission. Why ShouldanEmergency PhysicianBe Aware of This? Early and accurate diagnosis of PMA is important because, if left untreated, mortality rate can reach 100%. A potential pitfall in our case is the presence of hematuria with flank pain that could lead to incorrect diagnosis of renal calculi, a much more common condition. This case illustrates the importance of using POCUS in any patient with back or flank pain, with or without hematuria.

Keywords: hematuria; periureteritis; point-of-care ultrasound; psoas muscle abscess; renal calculi; spondylodiscitis.