Perirenal fat stranding as a predictor of disease progression after radical nephroureterectomy for renal pelvic urothelial carcinoma: A retrospective study

Abstract Background To investigate the impact of Perirenal fat stranding (PRFS) on progression after radical nephroureterectomy (RNU) for pelvic urothelial carcinoma (RPUC) without hydronephrosis and to reveal the pathological findings of PRFS. Methods Clinicopathological data, including computed tomography (CT) findings of the ipsilateral and contralateral PRFS, were collected from the medical records of 56 patients treated with RNU for renal RPUC without hydronephrosis between 2011 and 2021 at our institution. Ipsilateral PRFS on CT was classified as either low or high PRFS. The impact of PRFS on progression-free survival (PFS) after RNU was analyzed using the Kaplan-Meier method and log-rank test. In addition, specimens including sufficient perirenal fat from patients with low and with high PRFS were pathologically analyzed. Results Of the 56 patients, 31(55.4%) and 25 (44.6%) patients were classified as having low and high PRFS, respectively. Within a median follow-up of 40.6 months postoperatively, 11 (19.6%) patients showed disease progression. The Kaplan-Meier method and log-rank test revealed that patients with ipsilateral high PRFS had significantly lower PFS rates than those with ipsilateral low PRFS (3-year PFS 69.8% vs 93.3%; p=0.0393). Pathological analysis revealed that ipsilateral high PRFS specimens (n=3 patients) contained more fibrous strictures in perirenal fat than ipsilateral low PRFS specimens (n=3 patients). Conclusions PRFS of RPUC without hydronephrosis consists of collagenous fibers. The presence of ipsilateral high PRFS is a risk factor for progression after RNU for RPUC patients without hydronephrosis. Strict follow-up after surgery is thus recommended for these patients.