Complicated pubovesical fistula on PET/CT and MRI

Abstract

Pubovesical fistula (PVF) is a rare, unexpected complication that can occur in the clinical course of prostate cancer (PCa) treatment [1]. In a recent largest case series, PVF developed 2.3–27.0 years after initial radiation treatment [2]. MRI with contrast is the preferred imaging modality to provide ideal resolution of PVF and potential fluid collections and to assess the extent of osseous involvement and inflammatory changes of the surrounding musculature. CT has a very limited role in assessing PVF but can show complications of PVF, e.g., destruction, sclerosis, fragmentation, or abscess. A 75-year-old man with metastatic PCa underwent restaging MRI pelvis and Ga-prostate-specific membrane antigen (PSMA) PET/CT. On MRI, axial (A) T2-weighted image, axial T2-weighted fat saturated image (B), and axial post-contrast image (C) show a fistula tract between the pubic symphysis and the bladder (white arrows), bladder wall thickening (white asterisk, negative for malignancy on biopsy), and a small right pectineus muscle abscess (white arrowheads). PET images show increased Ga-PSMA uptake, in several foci in the pelvis; in the asymmetric reactive right bladder wall thickening (E and H, white arrows; better evaluated on MRI); in the small right pectineus muscle abscess (E and H, white arrowheads; better delineated on MRI); and in erosions and fragmentation of the pubic symphysis bone (G and H, black arrowheads; bone window image), with surrounding inflammatory uptake. The patient received therapeutic pelvic radiation therapy for PCa which probably contributed to PVF [1–4] with bladder wall thickening, pubic bone erosions and fragmentations, and a small right pectineus muscle abscess. While a few reports have demonstrated increased Ga-PSMA uptake in different benign infectious/ inflammatory processes [5, 6] and fistula [7] conditions, this case also illustrates benign infectious/inflammatory Ga-PSMA uptake in this extremely rare complication of PCa treatment.