Postpartum inflammatory sacroiliitis mimicking infection: A case report of diagnostic and therapeutic challenges

Low back pain is common during pregnancy, often resolving postpartum. However, acute severe postpartum Sacroiliac Joint (SIJ) inflammation mimicking infection is rare. We report a case of a 25-year-old female presenting with severe right-sided low back pain radiating to the leg, two days after vaginal delivery of a stillbirth. Magnetic Resonance Imaging (MRI) suggested infective sacroiliitis, and empirical intravenous antibiotics were initiated. Despite treatment, pain persisted. A Computed Tomography (CT)-guided biopsy indicated an inflammatory process without infection. Ultrasound and fluoroscopy-guided SIJ injection of local anesthetic and corticosteroid resulted in immediate significant pain relief, with further improvement after a repeat injection two months later. This case highlights the challenges of managing peripartum sacroiliitis. MRI is the choice of diagnostic modality but tissue biopsy is recommended to differentiate between infective and inflammatory pathology. Early image-guided SIJ injection serves both diagnostic and therapeutic roles, enabling faster recovery when conservative treatment fails.