Case Report: Urachal abscess complicated by interloop abscess

Urachal abscess, a rare infection arising from a congenital urachal remnant, is uncommonly complicated by secondary interloop abscess. We report a case of urachal abscess complicated by interloop abscess in an elderly woman. The patient presented primarily with lower abdominal pain and a palpable suprapubic mass, with mildly elevated serum levels of carbohydrate antigen 125 (CA125) and carcinoembryonic antigen (CEA). Abdominal computed tomography (CT) and magnetic resonance imaging (MRI) revealed two adjacent thick-walled cystic lesions, one in the space of Retzius and the other posterior to the first lesion. Both lesions showed peripheral rim enhancement, enhancing internal septations, non-enhancing fluid components, and marked hyperintensity on diffusion-weighted imaging (DWI). Thin-slice contrast-enhanced CT clearly depicted a tract-like communication connecting the two lesions. Operative findings confirmed that the lesion in the space of Retzius originated from the urachus, whereas the posterior lesion arose from the interloop space. Histopathological examination showed suppurative inflammation with abscess formation in the urachal lesion. We report the clinical features and imaging findings of this case to raise clinicians’ awareness of this rare complication and to offer preliminary imaging clues that may assist in its preoperative recognition.