Misdiagnosis of Rectus Abdominis Abscess Owing to Delayed Contrast-Enhanced Computed Tomography

A 77-year-old man, who was on anticoagulation, presented with a painful lump on the right abdominal wall. Laboratory tests showed slight anaemia and elevated inflammatory markers. Abdominal plain computed tomography (CT) revealed a mass in the right rectus abdominis muscle. He was admitted with a diagnosis of primary rectus abdominis haematoma. However, on the next day, the diagnosis was corrected to primary rectus abdominis abscess, following contrast-enhanced CT of the abdomen. This case illustrates the importance of considering primary rectus abdominis abscess in patients with suspected primary rectus abdominis haematoma, and contrast should be used when performing CT. LEARNING POINTS: Primary rectus abdominis abscess should be considered in patients with suspected primary rectus abdominis haematoma. To differentiate rectus abdominis abscess from rectus abdominis haematoma, contrast should be used when computed tomography is performed.