CT findings and diagnostic performance of upper urinary tract carcinoma in situ.

<bold>Objectives: </bold>To evaluate the CT characteristics and detectability of carcinoma in situ (CIS) of the upper urinary tract.<bold>Methods: </bold>Between January 2007 and March 2020, 28 patients (mean age: 73 years, 25 male and 3 female) with 29 pure CIS lesions of the upper urinary tract (i.e., without concomitant non-CIS lesion) who underwent nephroureterectomy were identified. The most recent CT scan performed before ureteroscopy, systemic neoadjuvant chemotherapy, or nephroureterectomy was selected for analysis. Twenty-eight patients without upper tract malignancy were selected as a control group. All images were evaluated for presence of upper urinary tract CIS using confidence levels ranging from 1 to 100 by two radiologists. The confidence level of 75 was used as a cutoff threshold for calculating sensitivity and specificity.<bold>Results: </bold>The median interval between CT scan and nephroureterectomy was 96 days. The number of true-positive lesions (per-lesion sensitivity) was 41% (12/29) and 52% (15/29) by readers 1 and 2. The true-positive lesion appeared as wall thickening in 83% (10/12) by reader 1 and 80% (12/15) by reader 2, and as a mass in 17% (2/12) by reader 1 and 20% (3/15) by reader 2. All mass-forming lesions were located in the renal collecting system. The per-patient sensitivity and specificity were 42% and 100% in reader 1, and 54% and 96% in reader 2.<bold>Conclusions: </bold>The common abnormal finding of pure CIS in the upper urinary tract was wall thickening. Pure CIS could also appear as a mass-forming lesion when it is located in the renal collecting system.<bold>Key Points: </bold>• The common abnormal finding of pure CIS in the upper urinary tract is wall thickening. Gradually progressive urothelial wall thickening and/or worsening symptoms should raise the suspicion of CIS. • Pure CIS in the upper urinary tract also appears as a mass-forming lesion when it is located in the renal collecting system. • Hydronephrosis and fat stranding play an auxiliary role in detecting pure CIS in the upper urinary tract. [ABSTRACT FROM AUTHOR]