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

OBJECTIVES: To evaluate the CT characteristics and detectability of carcinoma in situ (CIS) of the upper urinary tract. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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. KEY POINTS: • 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.

CT and MR imaging for solid renal mass characterization.

As our understanding has expanded that relatively large fraction of incidentally discovered renal masses, especially in small size, are benign or indolent even if malignant, there is growing acceptance of more conservative management including active surveillance for small renal masses. As for advanced renal cell carcinomas (RCCs), nonsurgical and subtype specific treatment options such as immunotherapy and targeted therapy is developing. On these backgrounds, renal mass characterization including differentiation of benign from malignant tumors, RCC subtyping and prediction of RCC aggressiveness is receiving much attention and a variety of imaging techniques and analytic methods are being investigated. In addition to conventional imaging techniques, integration of texture analysis, functional imaging (i.e. diffusion weighted and perfusion imaging) and multivariate diagnostic methods including machine learning have provided promising results for these purposes in research fields, although standardization and external, multi-institutional validations are needed.

Differentiation of Benign From Metastatic Adrenal Masses in Patients With Renal Cell Carcinoma on Contrast-Enhanced CT.

OBJECTIVE: The purpose of this article was to determine whether imaging features on contrast-enhanced CT can differentiate benign from metastatic adrenal masses in patients with renal cell carcinoma (RCC). MATERIALS AND METHODS: Between January 2008 and January 2014, 135 patients with untreated RCC were found to have 163 adrenal masses (102 benign and 61 metastatic) on contrast-enhanced CT including the corticomedullary phase (66 benign and 42 metastatic) or nephrographic phase (56 benign and 33 metastatic) or both. Imaging features of renal and adrenal masses were recorded, including T and N staging components of renal masses, internal texture, CT attenuation values, and attenuation differences between renal and adrenal masses. Logistic regression diagnostic models to differentiate benign from metastatic adrenal mass were constructed using independently significant imaging parameters in the respective corticomedullary and nephrographic phases (corticomedullary phase model and nephrographic phase model). Diagnostic performance of the models was evaluated by ROC analysis. RESULTS: Statistically significant variables for the models were regional lymphadenopathy, perirenal or renal sinus fat invasion (corticomedullary phase model only), adrenal mass size, CT attenuation value of adrenal mass, and absolute value of attenuation difference between renal and adrenal masses. Both models had excellent diagnostic performance; the AUC and optimal sensitivity and specificity for the diagnosis of metastasis were 0.991, 100%, and 92.4%, respectively, in the corticomedullary phase model and 0.947, 81.8%, and 96.4%, respectively, in the nephrographic phase model. CONCLUSION: Differentiation between benign and metastatic adrenal masses in patients with RCC can be achieved accurately by combining multiple imaging features on contrast-enhanced CT.

CT negative attenuation pixel distribution and texture analysis for detection of fat in small angiomyolipoma on unenhanced CT.

PURPOSE: The purpose of the paper is to evaluate if CT pixel distribution and texture analysis can identify fat in angiomyolipoma (AML) on unenhanced CT. METHODS: Thirty-seven patients with 38 AMLs and 75 patients with 83 renal cell carcinomas (RCCs) were evaluated. Region of interest (ROI) was manually placed over renal mass on unenhanced CT. In-house software generated multiple overlapping small-ROIs of various sizes within whole-lesion-ROI. Maximal number of pixels under cutoff attenuation values in the multiple small-ROIs was calculated. Skewness of CT attenuation histogram was calculated from whole-lesion-ROI. Presence of fat in renal mass was also evaluated subjectively. Performance of subjective evaluation and objective methods for identifying fat was compared using McNemar test. RESULTS: Macroscopic fat was identified in 15/38 AMLs and 1/83 RCCs by both subjective evaluation and by CT negative pixel distribution analysis (p = 1.0). Optimal threshold was ≥6 pixels below -30 HU within 13-pixel-ROI. Skewness of < -0.4 in whole-lesion-ROI identified fat in 10/38 AMLs and 0/83 RCCs. By combining CT negative pixel distribution analysis and skewness, fat was identified in 20/38 AMLs and 1/83 RCCs, but the difference to the subjective method was not statistically significant (p = 0.07). CONCLUSION: CT negative attenuation pixel distribution analysis does not identify fat in AML beyond subjective evaluation. Addition of skewness by texture analysis may help improve identifying fat in AML.

Small (< 4 cm) Renal Masses: Differentiation of Angiomyolipoma Without Visible Fat From Renal Cell Carcinoma Using Unenhanced and Contrast-Enhanced CT.

OBJECTIVE: The purpose of this study was to evaluate if small (< 4 cm) angiomyolipoma without visible fat can be differentiated from renal cell carcinoma (RCC) using contrast-enhanced CT alone and using unenhanced and contrast-enhanced CT in combination. MATERIALS AND METHODS: Twenty-three patients with 24 angiomyolipomas without visible fat and 130 patients with 148 RCCs underwent unenhanced and contrast-enhanced CT. Demographic data and size, shape, CT attenuation, and heterogeneity (entropy and subjective score) of the renal mass on unenhanced CT and contrast-enhanced CT were recorded. Multivariate logistic regression models were constructed for parameters obtained by contrast-enhanced CT alone and by both unenhanced and contrast-enhanced CT. Demographic data and size and shape of renal mass were used in each model. Sensitivity and specificity were calculated. RESULTS: Logistic regression model from contrast-enhanced CT data included sex, percentage of exophytic growth, entropy, and CT attenuation on contrast-enhanced CT. Model from both unenhanced and contrast-enhanced CT data included age, sex, short-axis diameter, percentage of exophytic growth, lesion-to-kidney CT attenuation difference on unenhanced CT, and CT attenuation on contrast-enhanced CT. The contrast-enhanced CT-based model and combined unenhanced and contrast-enhanced CT-based model differentiated angiomyolipoma from RCC with sensitivity and specificity of 42% and 98% versus 50% and 98%, respectively. CONCLUSION: Combinations of various CT and demographic findings allowed differentiation of angiomyolipoma from RCC.

Small (< 4 cm) Renal Mass: Differentiation of Oncocytoma From Renal Cell Carcinoma on Biphasic Contrast-Enhanced CT.

OBJECTIVE: The purpose of this study was to evaluate whether small (< 4 cm) oncocytomas can be differentiated from renal cell carcinomas (RCCs) on biphasic contrast-enhanced CT. MATERIALS AND METHODS: Forty-three patients with 53 oncocytomas and 123 patients with 128 RCCs (24 papillary subtype and 104 clear cell and other subtypes) who underwent biphasic contrast-enhanced CT were included in the study. Patient demographics and CT tumor characteristics were evaluated in each case. A multinomial logistic regression model was then constructed for differentiating oncocytoma from clear cell and other subtype RCCs, oncocytoma from papillary RCCs, and clear cell and other subtype RCCs from papillary RCCs. The probability of each group was calculated from the model. Diagnostic performance among three pairwise diagnoses and between oncocytoma and any RCC (clear cell and other subtypes and papillary) were assessed by AUC values. RESULTS: Patient age, tumor CT attenuation values and skewness (i.e., histogram analysis of CT values) in both the corticomedullary and nephrographic phases, and subjective tumor heterogeneity were statistically significant variables in the multinomial logistic regression analysis. The logistic regression model using the variables yielded AUCs of 0.82, 0.95, 0.91, and 0.84 for differentiating oncocytomas from clear cell and other subtype RCCs, oncocytomas from papillary RCCs, clear cell and other subtype RCCs from papillary RCCs, and oncocytomas from any RCC (clear cell and other subtypes and papillary), respectively. CONCLUSION: A combination of imaging features on biphasic CT, including tumor CT attenuation values and tumor texture (heterogeneity and skewness), can help differentiate oncocytoma from RCC.

MRI Findings of Inverted Urothelial Papilloma of the Bladder.

OBJECTIVE: The objective of this study was to characterize MRI findings of inverted urothelial papilloma of the bladder. MATERIALS AND METHODS: Data pertaining to 16 patients with 18 pathologically proven inverted urothelial papillomas of the bladder who had undergone MRI were retrospectively collected from seven institutions. The shape and surface characteristics of the tumors were evaluated using T2-weighted MR images. In addition, the signal intensity of inverted urothelial papillomas was visually assessed on T1-weighted, T2-weighted, and DW images and on early and delayed phase contrast-enhanced images. RESULTS: The shape of the 18 inverted urothelial papillomas of the bladder was classified as polypoid with a stalk for 16 tumors (89%) and polypoid without a stalk for two tumors (11%). All stalks were surrounded by urine in the bladder. A total of 15 of the tumor surfaces (83%) were nonpapillary and three (17%) were papillary. All 12 of the inverted urothelial papillomas for which evaluable T1-weighted images were available were isointense with the bladder wall. The lesions had a slightly higher signal intensity than the bladder wall in 15 of the patients (83%) and showed isointensity with the bladder wall in three patients (17%). A total of three patients (17%) had tiny hyperintense foci noted on T2-weighted images. All 16 of the inverted urothelial papillomas examined by DWI had very high signal intensity. All 13 of the lesions for which early phase images were obtained using dynamic contrast-enhanced MRI showed strong enhancement. When compared with early phase images, delayed phase images of the same 13 lesions showed that enhancement was stronger in two lesions (15%), similar in six lesions (46%), and weaker in five lesions (38%). CONCLUSION: On MRI, the typical appearance of inverted urothelial papillomas of the bladder is a polypoid shape with a nonpapillary surface and a thin short stalk surrounded by urine. Cystic foci are also occasionally seen within the tumor.

Retrospective analysis of contrast-enhanced computed tomographic findings related to obstructive shock due to ascending aortic dissection.

OBJECTIVE: The objective of this study was to evaluate contrastenhanced computed tomography findings related to obstructive shock due to ascending aortic dissection (AAD). METHODS: The computed tomography findings in 9 AAD patients with shock, 11 AAD patients without shock, and 18 control subjects were evaluated for (1) pericardial effusion, (2) diameter of the inferior vena cava, (3) periportal hypodensity, (4) retrograde reflux of contrast material, (5) aortic and visceral enhancement, and (6) other factors (peripancreatic edema, bowel thickening/dilatation). RESULTS: Patients with shock showed the highest ratio of pericardial effusion, periportal hypodensity, and retrograde reflux of contrast material; largest inferior vena cava diameter; stronger aortic enhancement in both the arterial and portal phases; lowered splenic and pancreatic enhancement in the arterial phase; and stronger visceral (especially adrenal) enhancement, except for the renal medulla in the portal phase. CONCLUSIONS: Computed tomography findings related to obstructive shock due to AAD reflected impaired diastolic filling, decreased cardiac output, and flow redistribution in visceral organs.

High b-value diffusion-weighted MRI in differentiation between benign and malignant polypoid gallbladder lesions.

BACKGROUND: Several studies have reported the effectiveness of high b-value diffusion-weighted MR imaging (DWI) in the abdominal region, and have found that various malignant tumors may show high signal intensity on DWI, reflecting their high cellularity and/or their long relaxation time. The value of ADC measurement has also been documented for the diagnosis of several abdominal malignancies. PURPOSE: To retrospectively evaluate the usefulness of high b-value DWI in differentiating between benign and malignant polypoid gallbladder lesions. MATERIAL AND METHODS: The study population consisted of 10 benign (three hyperplastic polyps and seven adenomas) and 13 malignant (all adenocarcinomas) polypoid gallbladder lesions. DWI was evaluated by two observers. Qualitatively, the signal intensity of the lesions on DWI was visually evaluated and categorized as iso, high, or very high. Quantitatively, the ADC values of the lesions were measured from ADC maps. Statistical analysis was performed using a two-tailed Fisher's exact test and the Mann-Whitney test, respectively. RESULTS: Qualitative analysis revealed a statistical difference (P = 0.0041). Six of 10 benign lesions were categorized as iso, and the remaining four were categorized as high. In the 13 malignant lesions, one was categorized as iso, five as high, and seven as very high. The ADC values of the malignant lesions (1.34 ± 0.50 × 10(-3) mm(2)/sec) were significantly lower than those of the benign lesions (2.26 ± 0.44 × 10(-3) mm(2)/sec) (P = 0.00016). CONCLUSION: High b-value DWI may be useful for differentiating between benign and malignant polypoid gallbladder lesions by the visual assessment of DWI and ADC measurement.

Magnetic resonance imaging of large chromophobe renal cell carcinomas.

PURPOSE: The objective of this study was to clarify the magnetic resonance imaging (MRI) findings of large chromophobe renal cell carcinomas. MATERIALS AND METHODS: Five patients diagnosed pathologically with chromophobe renal cell carcinoma are included. MRI findings were retrospectively evaluated for the tumor contour, uniformity and hypointensity of the rim of the tumor on T2-weighted images, "microscopic fat," enhancement degree and pattern on dynamic study, and necrosis in the tumor, among other findings. RESULTS: The tumor size ranged from 4.8 to 13.7 cm (mean 7.9 cm). The tumor contour was well defined in four patients. All but one tumor showed a hypointensity rim, and all tumors had a heterogeneous appearance on T2-weighted images. "Microscopic fat" was detected in one case. All tumors demonstrated low enhancement compared to that of the renal cortex. All tumors showed heterogeneous enhancement on postcontrast images. Necrosis was seen in four. Hemorrhage and renal vein thrombosis was seen in one. CONCLUSION: Chromophobe renal cell carcinomas of large size tend to have a heterogeneous appearance on postcontrast and T2-weighted images, a well-defined tumor contour with a hypointensity rim on T2-wighted images, and lower enhancement than that of the renal cortex. Tumor necrosis is easily apparent, and "microscopic fat" may be observed.