Iliopsoas Abscess Mimicking a Lower Motor Neuron Lesion: A Diagnostic Challenge

Iliopsoas abscess is a rare infection that presents with a triad of fever, back pain, and hip pain. However, due to the anatomical proximity of the psoas muscle to various structures, an abscess in this region can manifest with nonspecific symptoms, leading to potential misdiagnosis and delayed diagnosis, which can be fatal. We report a case of a 54-year-old female who presented to the emergency department with right-sided flank pain and symptoms resembling lower motor neuron disorder. Initial investigations were inconclusive until an MRI revealed a large retroperitoneal collection in the right perinephric space and iliopsoas muscle, likely of urological origin, with no spinal abnormalities. Intravenous gentamicin was initiated. A subsequent contrast-enhanced CT scan of the abdomen and pelvis confirmed a right posterior perinephric collection. Ultrasound-guided drainage was performed, and a pigtail catheter was placed in situ for continuous drainage along with targeted antibiotics based on culture and sensitivity.