Clinical Evaluation of Cystic Renal Masses With Bosniak Classification by Contrast-Enhanced Ultrasound and Contrast-Enhanced Computer Tomography

OBJECTIVES

The study aims to compare retrospectively three clinically applied methods for the diagnostic performance of cystic renal masses (CRMs) by contrast-enhanced ultrasound (CEUS) and contrast-enhanced computer tomography (CECT) with Bosniak classification system.

METHODS

A total of 52 cases of Bosniak II-IV CRMs in 49 consecutive patients were diagnosed from January 2013 to July 2022 and their data were analyzed. All patients had been subjected to CEUS and CECT simultaneously. Pathological diagnoses and masses stability were used as standard references to determine whether lesions were malignant or benign. Then 49 CRMs only with pathologic results were classified into group 1 and 2.

RESULTS

A total of 52 CRMs in 49 enrolled patients were classified into 8 category II, 16 category IIF, 15 category III, and 13 category IV by CEUS (EFSUMB 2020), 10 category II, 13 category IIF, 16 category III, and 13 category IV by CEUS (V2019), while 15 category II, 9 category IIF, 13 category III, and 15 category IV by CECT (V2019). Pathological results and masses stability longer than 5 years follow-up performed substantially for CEUS (EFSUMB 2020), CEUS (V2019), and CECT (V2019) (kappa values were 0.696, 0.735, and 0.696, respectively). Among 49 pathologic approving CRMs, wall/septation thickness ≥4 mm, wall/septation thickness, presence of enhancing nodule and the diameter were found to be statistically significant for malignancy. Twenty-two malignant masses were correctly diagnosed by CEUS (V2019), while 21 malignant masses were both correctly diagnosed by CEUS (EFSUMB 2020) and CECT (V2019), and 1 mass was misdiagnosed.

CONCLUSIONS

Bosniak classification of EFSUMB 2020 version might be as accurate as version 2019 CEUS and version 2019 CECT in diagnosing CRMs, and CEUS is found to have an excellent safety profile in dealing with clinical works.

Role of Contrast-Enhanced Ultrasound in Evaluation of Cystic Renal Mass

OBJECTIVES

Contrast-enhanced ultrasound (CEUS) allows excellent delineation of perfusion in septa and nodules without exposure to ionizing radiation or nephrotoxic contrast media. The aim of our study was to evaluate the role of CEUS for the assessment of cystic renal masses and compare its diagnostic performance with that of CECT.

METHODS

Exactly 40 patients diagnosed to have cystic renal masses on CECT scan were prospectively evaluated with CEUS and were assigned a Bosniak class. Based on results of final histopathology and clinical follow-up, internal validity of both CEUS and CECT was evaluated, including agreement between these two modalities.

RESULTS

Out of the 40 patients (mean size 3.1 ± 2.5 cm), 23 patients had benign lesions and 17 patients had malignant lesions. For CEUS, the sensitivity and negative predictive value was 100%, the specificity and positive predictive value was 73.9%. For CECT, the sensitivity and negative predictive value were 88.2 and 83.3%, respectively, whereas the specificity and positive predictive value was 87 and 90.9%, respectively. Both imaging modalities had similar accuracy with fair to good agreement with the final diagnosis (Κ = 0.71 and 0.75 for CEUS and CECT, respectively). Concordance between CEUS and CECT was seen in 29 patients (72.5%) with fair agreement between the two modalities (K = 0.66).

CONCLUSION

CEUS has comparable accuracy with CECT and could be used as screening modality to rule out the presence of complex cystic renal masses without exposure of nephrotoxic contrast media and ionizing radiation.

Outcomes of Bosniak Classification Version 2019 Class IIF Cystic Renal Masses at Imaging Surveillance

BACKGROUND. Bosniak classification system version 2019 (v2019) recommends that class IIF masses undergo follow-up imaging at 6 months, 12 months, and then annually for 5 years. The frequency and timing of upgrade on follow-up imaging are incompletely understood. OBJECTIVE. The purpose of this article is to describe the temporal evolution of Bosniak v2019 class IIF cystic renal masses, with attention to outcomes at 6-month follow-up, the time to class upgrade, and malignant histologic diagnoses. METHODS. This retrospective study included 219 patients (91 women, 128 men; median age, 72 years) with 246 localized class IIF masses from January 2005 to June 2022. Patients underwent both a baseline and at least one follow-up renal-mass protocol contrast-enhanced CT or MRI examination. Two radiologists evaluated masses at all follow-up time points to categorize masses as downgraded (class I or II), stable (localized class IIF), or upgraded (class III or IV, solid, or category T3a, N1, or M1 or higher disease); a third radiologist resolved discrepancies. Incidence rate of upgrade was determined. Histopathologic outcomes were assessed for resected masses. RESULTS. Median follow-up was 28.4 months (IQR, 13.7-59.4 months). At 6-month follow-up, five (2%) masses were downgraded, 241 (98%) were stable, and none were upgraded. On the basis of final follow-up, 14 (6%) masses were downgraded, 223 (91%) were stable, and nine (4%) were upgraded. All upgrade events entailed a class increase to III (n = 7) or IV (n = 2); no mass became solid or developed T3, N1, or M1 disease. Among the nine upgraded masses, median time to upgrade was 53.5 months (IQR, 23.2-63.7 months). Incidence rate of upgrade was 3.006 per 100,000 person-days (95% CI, 1.466-5.516). Ten masses were resected; histopathology was benign in six and malignant in four. Of the four malignant masses, one was upgraded to class III after 15 months of preoperative follow-up imaging, and three remained class IIF on preoperative follow-up imaging. No resected malignant mass developed postoperative recurrence. CONCLUSION. Bosniak v2019 class IIF masses are unlikely to represent aggressive malignancy; only 4% were upgraded over time and never on initial 6-month follow-up. CLINICAL IMPACT. The currently recommended initial 6-month follow-up imaging examination for class IIF masses is of questionable clinical utility.

Long-Term Functional and Oncologic Outcomes of Robot-Assisted Partial Nephrectomy for Cystic Renal Tumors: A Single-Center Retrospective Study

Objectives: To evaluate the outcomes of robot-assisted partial nephrectomy (RAPN) in cystic renal tumors. Materials and Methods: We retrospectively analyzed patients who underwent RAPN for either cystic (n = 46) or solid (n = 271) renal tumors at Fujita Health University between 2010 and 2019. Cystic renal tumors were diagnosed using cross-sectional imaging. Perioperative, oncologic, and functional outcomes were assessed. Results: The median follow-up periods were 38, 41, and 37 months in the total, cystic, and solid groups, respectively. Most patient characteristics were similar among both groups, while the median age of the cystic group was significantly lower than that of the solid group (p = 0.02). Most perioperative variables and complications were comparable between the two groups. There was no significant difference between the groups in perioperative renal function. The estimated glomerular filtration rate preservation rates were 93.1% and 89.2% in the cystic and solid groups, respectively (p = 0.17). The cystic group showed a higher benign histology rate (19.6% vs 7%) and lower Fuhrman grade than the solid group (24.3% vs 15.1% in grade 1, and 73% vs 81.3% in grade 2), although there was no statistically significant difference between the two groups. In the solid group, 10 patients (3.7%) experienced recurrence, and 2 patients (0.7%) died of renal-cell carcinoma, while none of the patients with cystic tumors experienced recurrence. There was no statistically significant difference between the cystic and solid tumors with respect to 5-year recurrence-free survival (p = 0.18), cancer-specific survival (p = 0.55), and overall survival (p = 0.35). Conclusions: RAPN for cystic renal tumors appears to be safe and feasible with perioperative, long-term functional and oncologic outcomes comparable with those in solid tumors. RAPN can be a safe and effective surgical option for cystic renal tumors.

Bosniak Classification of Cystic Renal Masses Version 2019: Comparison of Categorization Using CT and MRI

BACKGROUND. Bosniak classification version 2019 proposed refinements for cystic renal mass characterization and now formally incorporates MRI, which may improve concordance with CT. OBJECTIVE. The purpose of this study is to compare concordance of CT and MRI in evaluation of cystic renal masses using Bosniak classification version 2019. METHODS. Three abdominal radiologists retrospectively reviewed 68 consecutive cystic renal masses from 45 patients assessed with both CT and MRI renal mass protocols within a year between 2005 and 2019. CT and MRI were reviewed independently and in separate sessions, using both the original and 2019 versions of Bosniak classification systems. RESULTS. Using Bosniak classification version 2019, cystic renal masses were classified into 12 category I, 19 category II, 13 category IIF, four category III, and 20 category IV by CT and eight category I, 15 category II, 23 category IIF, nine category III, and 13 category IV by MRI. Among individual features, MRI showed more septa (p < 0.001, p = 0.046, p = 0.005; McNemar test) for all three radiologists, although both CT and MRI showed a similar number of protrusions (p = 0.823, p = 1.0, p = 0.302) and maximal septa and wall thickness (p = 1.0, p = 1.0, p = 0.145). Of the discordant cases with version 2019, MRI led to a higher categorization in 12 masses. The reason for upgrade was most commonly because of protrusions identified only on MRI (n = 4), an increased number of septa (n = 3), and a new category: heterogeneously T1-weighted hyperintensity (n = 3). Neither modality was more likely to lead to a categorization change for either version 2019 (p = 0.502; McNemar test) or the original (p = 0.823) Bosniak classification system. Overall interrater agreement was substantial for both CT (κ = 0.745) and MRI (κ = 0.655) using version 2019 and was slightly higher than that of the original system for CT (κ = 0.707) and MRI (κ = 0.623). CONCLUSION. CT and MRI were concordant in the majority of cases using Bosniak classification version 2019, and category changes by modality were not statistically significant. Interrater agreements were substantial for both CT and MRI. CLINICAL IMPACT. Bosniak classification version 2019 as applied to cystic renal masses has substantial interrater agreement and does not lead to systematic category upgrades with either CT or MRI.

Update on MRI of Cystic Renal Masses Including Bosniak Version 2019

Incidental cystic renal masses are common, usually benign, and almost always indolent. Since 1986, the Bosniak classification has been used to express the risk of malignancy in a cystic renal mass detected at imaging. Historically, magnetic resonance imaging (MRI) was not included in that classification. The proposed Bosniak v.2019 update has formally incorporated MRI, included definitions of imaging terms designed to improve interobserver agreement and specificity for malignancy, and incorporated a variety of masses that were incompletely defined or not included in the original classification. For example, at unenhanced MRI, homogeneous masses markedly hyperintense at T₂ -weighted imaging (similar to cerebrospinal fluid) and homogeneous masses markedly hyperintense at fat suppressed T₁ -weighted imaging (approximately ≥2.5 times more intense than adjacent renal parenchyma) are classified as Bosniak II and may be safely ignored, even when they have not been imaged with a complete renal mass MRI protocol. MRI has specific advantages and is recommended to evaluate masses that at computed tomography (CT) 1) have abundant thick or nodular calcifications; 2) are homogeneous, hyperattenuating, ≥3 cm, and nonenhancing; or 3) are heterogeneous and nonenhancing. Although MRI is generally excellent for characterizing cystic renal masses, there are unique weaknesses of MRI that bear consideration. These details and others related to MRI of cystic renal masses are described in this review, with an emphasis on Bosniak v.2019. A website (https://bosniak-calculator.herokuapp.com/) and mobile phone apps named "Bosniak Calculator" have been developed for ease of assignment of Bosniak classes. LEVEL OF EVIDENCE: 5 TECHNICAL EFFICACY STAGE: 3.

Bosniak Classification Version 2019 of Cystic Renal Masses Assessed With MRI

OBJECTIVE. The purpose of this study was to determine how use of Bosniak classification version 2019 affects categorization and overall accuracy of MRI evaluation of cystic renal masses with tissue pathologic analysis as the reference standard. MATERIALS AND METHODS. MR images of 50 consecutively registered patients with tissue pathologic results from 2005 to 2019 were retrospectively reviewed by two abdominal radiologists. Each radiologist independently assigned a category based on the original and Bosniak classification version 2019 systems. Interreader agreements (kappa statistic) for both were calculated, and consensus reading was performed. Tissue pathologic analysis was used as the reference standard to determine whether a lesion was benign or renal cell carcinoma. RESULTS. Fifty-nine cystic renal masses were characterized as 38 renal cell carcinomas and 21 benign lesions on the basis of the results of tissue pathologic analysis. By consensus, according to the original Bosniak criteria, the renal masses were classified into three category I, five category II, four category IIF, 25 category III, and 22 category IV lesions. By consensus, according to the version 2019 criteria, the renal masses were classified into three category I, two category II, 12 category IIF, 18 category III, and 24 category IV lesions. Overall sensitivity and specificity for identifying renal cell carcinoma were 95% and 81%, respectively, with the original classification system and 100% and 86%, respectively, with version 2019. Weighted interreader agreement was moderate for both the original system (κ = 0.57) and version 2019 (κ = 0.55). CONCLUSION. Use of Bosniak classification version 2019 system improves sensitivity and specificity for malignancy among cystic renal masses characterized with MRI. Most lesions that changed categories were reclassified as Bosniak category IIF.

Robot-assisted partial nephrectomy confers excellent long-term outcomes for the treatment of complex cystic renal tumors: Median follow up of 58 months

OBJECTIVES

To analyze long-term outcomes of robot-assisted partial nephrectomy for treatment of complex cystic renal tumors.

METHODS

We retrospectively analyzed the data of patients who underwent robot-assisted partial nephrectomy for cystic (n = 32) and solid (n = 263) renal masses at Severance Hospital, Seoul, Korea. The primary outcome was assessment of perioperative safety for cystic tumor. Secondary outcomes were evaluation of long-term oncological and functional results.

RESULTS

Patients' clinical and demographic characteristics were similar among both groups. The median follow up of cystic and solid masses were 58 and 46 months, respectively. Cystic masses were more likely to have low Fuhrman grade 1 and 2 (P = 0.03), and shorter operative time (P = 0.04) compared with solid masses. There was no statistically significant difference regarding warm ischemia time, estimated blood loss, trifecta achievement, length of hospital stay, complication rates and renal function preservation (P > 0.05) between groups. In the solid group, 12 patients (4.1%) recurred, and six patients (2%) died from metastatic renal cell carcinoma, whereas the patients in the cystic group did not have any local or distance recurrence, and the survival rates were 100%. The 5-year cancer-free survival (P = 0.77), cancer-specific survival (P = 0.65) and overall survival (P = 0.83) rates were similar between the groups.

CONCLUSION

Robot-assisted partial nephrectomy appears to be safe and feasible treatment for complex cystic renal masses. It confers excellent long-term oncological outcomes. Robot-assisted partial nephrectomy should be the treatment of choice for complex cysts whenever feasible.