Appendicitis or Not Appendicitis: A Case Report of Acute Appendicitis Complicated with Disseminated MSSA and Iliopsoas Abscess This case report describes a 17-year-old female with acute appendicitis complicated by Methicillin-Sensitive Staphylococcus Aureus (MSSA) bacteremia and an iliopsoas abscess. Initially presenting with right iliac fossa pain and fever, she was diagnosed with acute appendicitis and underwent appendectomy. Postoperatively, she developed persistent fever and hip pain. Imaging revealed an abscess in the right iliacus muscle, which was drained percutaneously. MSSA was identified in the abscess culture. The patient recovered with targeted antibiotics. This case highlights the diagnostic challenges and importance of considering secondary infections in postoperative patients with atypical symptoms. Prompt recognition and treatment are essential for positive outcomes.