Pathological and radiological evaluation of ureteral wall thickness measurement in urolithiasis

Non-contrast computed tomography (NCCT) is a mainstay in the diagnosis of urolithiasis, with multiple markers on NCCT used to predict the likelihood of stone passage and to assist in pre-operative planning. Ureter wall thickness (UWT) is one such parameter, however studies evaluating inter-observer agreement and comparing to native ureteral tissue are lacking. We aim to provide the first comparison of UWT from healthy human ureters with UWT measured on NCCT; and to evaluate for inter-observer variability on NCCT measurement. Human ureters were collected from consenting adults at the time of radical nephrectomy. The pathological UWT (pUWT) was compared to the median radiological UWT (rUWT) of three independent blinded observers. Statistical analysis was performed with Wilcoxon matched pairs signed rank test, intraclass correlation co-efficient and Bland-Altmann analysis. Samples from 23 patients were compared with a mean pUWt 2.1mm (range: 0.89-4.11mm) and rUWT of 1.30mm (range: 1-3.52mm). There was significant variation between median rUWT and pUWT (1.3mm vs 2.1mm, p=0.0005) with rUWT underestimating pUWT by a mean of 0.72mm. The intraclass correlation co-efficient of <0.50 suggests poor intra-reader reliability with limits of agreement on Bland-Altmann analysis of 2.5mm. This study represents the first comparison of pathological and radiological UWT in human ureteric tissue. There is a significant variation in pathological and radiological measurements, with high interobserver variability.