From Chronic Irritation to a Rare Malignant Subtype: ¹⁸F-FDG PET/ CT Imaging of Bladder Squamous Cell Carcinoma following Long-term Suprapubic Catheterisation

A 55-year-old man was diagnosed with muscle-invasive squamous cell carcinoma (SCC) of the urinary bladder in June 2025. The patient had a long-term indwelling suprapubic catheter placed in 2014 due to iatrogenic urethral trauma sustained after catheterization during inguinal hernia surgery. Subsequently, he underwent multiple surgeries for recurrent abscesses involving the urethra, urinary bladder, soft tissues of the pubic region, and the root of the penis. Follow-up magnetic resonance imaging was performed due to new-onset hematuria in June 2025, revealing a soft-tissue lesion in the anterior bladder wall near the entry site of the suprapubic catheter, as well as several fistulous tracts extending between the root of the penis (including the penile urethra) and the adjacent soft tissues. Cystoscopy through the cystostomy tract and biopsy of the lesion were performed, confirming the diagnosis of muscle-invasive SCC. The patient was referred for initial staging with ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) to assess for regional and distant metastases.

The hybrid imaging modality demonstrated pathologically increased metabolic activity in the primary malignant lesion in the anterior bladder wall, surrounding the insertion site of the indwelling suprapubic catheter, with no evidence of regional lymphadenopathy or distant metastatic spread [Fig 1]. In addition, multiple curvilinear, metabolically active structures were noted in the pubic region, extending from the root of the penis (including the penile urethra) toward the adjacent soft tissues, consistent with chronic, recurrent inflammatory changes and fistulous tracts [Fig 2].

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Fig 1: (a) The whole-body maximum intensity projection (MIP) image demonstrates increased urinary radiotracer accumulation along the suprapubic catheter (black arrow) and intense ¹⁸F-FDG uptake in the region of the urinary bladder (red arrow). Several additional¹⁸F-FDG avid curvilinear foci are noted in the pelvic region (green arrows), corresponding to active inflammatory changes and fistulous tracts. (b-e) The fused PET/CT images in axial and sagittal planes at the level of the urinary bladder show intense metabolic activity in the anterior bladder wall, corresponding to a soft tissue malignant lesion encompassing the suprapubic catheter which is seen also on MRI T2W-images. No metabolically active locoregional lymph nodes or distant metastases were identified on the whole-body PET/CT scan. FDG: Fluorodeoxyglucose; PET/CT: Positron emission tomogrpahy/computed tomography; MRI: Magnetic resonance imaging.

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Fig 2: Axial fused PET/CT image shows fistulous tracts with increased metabolic activity between the penile root, the subcutaneous fat in the pubic area and the left ischioanal fossa (arrows). PET/CT: Positron emission tomography

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Bladder cancer is the sixth-most common malignancy in men and ranks ninth when both sexes are considered.^[1] More than 90% of cases are urothelial carcinoma. One of the less common histological subtypes is SCC, accounting for 2%– 5% of bladder cancers, typically associated with an aggressive course and poor prognosis.^[2,3] The disease comprises two major subtypes: SCC associated with schistosomiasis (bilharzial-associated SCC [B-SCC]) and SCC unrelated to schistosomiasis (non-B-SCC [NB-SCC]). Schistosomiasis is a leading cause of bladder SCC in endemic regions such as North and East Africa and the Middle East. In nonendemic countries, including Bulgaria, the main risk factors for NB-SCC are related to chronic irritation of the urothelium and include long-term indwelling catheterisation, recurrent urinary tract infections, and bladder calculi.^[4] Prior pelvic radiotherapy and prolonged exposure to cyclophosphamide have also been implicated.^[5] These conditions create a proinflammatory environment conducive to squamous metaplasia and, ultimately, malignant transformation.^[6]This case illustrates the risk of bladder SCC in patients with long-term suprapubic catheterisation and recurrent urinary tract infections. It emphasises the need for regular follow-up and early evaluation of any new urinary symptoms in this high-risk group.