Evaluation of cystic renal masses: comparison of CT and MR imaging by using the Bosniak classification system

PURPOSE: To compare computed tomography (CT) and magnetic resonance (MR) imaging in the evaluation of cystic renal masses by using the Bosniak classification system. MATERIALS AND METHODS: Images of 69 renal masses in 59 patients (38 men, 21 women; mean age, 60.4 years; range, 30-86 years), who had undergone both CT and MR imaging examinations within 1 year (average, 60.5 days; range, 0-356 days), were retrospectively analyzed by two radiologists in consensus. For each lesion, images were compared for thickness of wall and septa, number of septa, and presence of enhancement. Each mass was categorized (Bosniak classification) first on CT images and then on MR images, and results were compared. Pathologic correlation was available in 25 lesions. RESULTS: On CT images, there were 15 category I, 16 category II, 10 category IIF, 19 category III, and nine category IV lesions. Findings on CT and MR images were similar in 56 (81%) lesions; in 13 (19%) lesions, there were differences. In eight (12%) lesions, MR imaging depicted more septa than did CT, which resulted in an upgrade of the classification at MR imaging in two cases. In seven (10%) lesions, MR imaging depicted increased wall and/or septa thickness compared with CT, resulting in a classification upgrade in six cases. Three lesions had both increased numbers of septa and thickening of the wall and/or septa. In two (3%) lesions, enhancement characteristics at CT and MR imaging were different. One of these lesions also had an increased number of septa. Overall, MR imaging results led to a cyst classification upgrade of seven lesions, from category II to IIF (n = 2), IIF to III (n = 3), or III to IV (n = 2). Pathologic correlation in 25 lesions revealed 20 malignant and five benign lesions. CONCLUSION: CT and MR imaging findings were similar in the majority of cystic renal masses. In some cases, however, MR images may depict additional septa, thickening of the wall and/or septa, or enhancement, which may lead to an upgraded Bosniak cyst classification and can affect case management.     

超声造影结合Bosniak标准在良恶性肾囊性病变鉴别诊断中的价值

目的 评价超声造影鉴别良恶性肾囊性病变的准确性,探讨超声造影结合Bosniak标准分级诊断肾囊性病变的可行性.资料与方法 对30例患者的36个肾囊性病灶进行超声造影,分析良恶性肾囊性病变的超声造影征象;按照Bosniak标准对超声造影的表现进行分级诊断,计算其敏感性、特异性、诊断符合率、阳性预测值、阳性似然比、Kappa值及验后概率,分析该方法分级诊断肾囊性病变的准确性.结果 超声造影可显示常规超声不能发现的囊内分隔及实性结构.超声造影结合Bosniak标准诊断肾囊性病变的敏感性、特异性、诊断符合率、阳性预测值、阳性似然比分别为92.9％、90.9％、94.8％、86.7％、10.2,Kappa=0.83;应用超声造影结合Bosniak标准可提高肾囊性病变良恶性诊断的验后概率.结论 超声造影结合Bosniak标准可以提高鉴别诊断肾囊性病变良恶性的准确性.     

CT与MRI下Bosniak分级对肾脏囊性病变诊断性能的对比研究

目的 比较CT下Bosniak分级和MRI下Bosniak分级对肾脏囊性病变的诊断性能.方法 回顾性分析30例(共42个肾脏囊性病灶)同时具备CT和MRI影像资料,并以术后病理或临床随访作为最终诊断,采用ROC曲线比较二种检查模式的诊断性能.结果 CT下Bosniak分级Ⅰ～Ⅳ级分别为6个、24个、9个、3个,对照病理结果其假阳性病灶数0个,假阴性病灶数14个.MRI下Bosniak分级Ⅰ～Ⅳ级分别8个、18个、10个、6个,对照病理结果其假阳性病灶数0个,假阴性病灶数11个.MRI下Bosniak分级的曲线下面积大于CT下Bosniak分级,前者的特异度和敏感度均高于后者.结论 MRI下Bosniak分级对于肾脏囊性病变的诊断性能高于CT下Bosniak分级,在条件允许的情况下应首先采用MRI下Bosniak分级.     

Cystic renal masses: Usefulness of the bosniak classification

To determine the usefulness of the Bosniak classification of cystic renal masses, the computed tomographic (CT) and ultrasound findings of 16 pathologically proven cystic renal masses were retrospectively reviewed. All imaging studies were reviewed and categorized utilizing the Bosniak classification without knowledge of the final pathologic diagnosis. There were no category I lesions (classical simple cyst), four category II (minimally complicated), seven category III lesions (more complicated), and five category IV lesions (probable malignant). All category II lesions were benign, all category IV lesions were malignant. Of the seven category III lesions, three were benign and four were malignant. We conclude that the Bosniak classification is extremely useful in the management of cystic renal masses. The opinions expressed herein are those of the authors and are not to be construed as official or as reflecting the views of the Uniformed Services University of the Health Sciences, the Department of Defense, or the United States Navy     

Cystic renal masses: usefulness of the Bosniak classification

To determine the usefulness of the Bosniak classification of cystic renal masses, the computed tomographic (CT) and ultrasound findings of 16 pathologically proven cystic renal masses were retrospectively reviewed. All imaging studies were reviewed and categorized utilizing the Bosniak classification without knowledge of the final pathologic diagnosis. There were no category I lesions (classical simple cyst), four category II (minimally complicated), seven category III lesions (more complicated), and five category IV lesions (probable malignant). All category II lesions were benign, all category IV lesions were malignant. Of the seven category III lesions, three were benign and four were malignant. We conclude that the Bosniak classification is extremely useful in the management of cystic renal masses.     

Complex cystic renal masses: characterization with contrast-enhanced US

PURPOSE: To prospectively compare contrast material-enhanced ultrasonography (US) with computed tomography (CT) in the classification of complex cystic renal masses with the Bosniak system. MATERIALS AND METHODS: Ethics committee approval and written informed consent were obtained. Forty patients (17 women, 23 men; age range, 31-77 years) with 44 complex cystic renal masses detected with conventional US were prospectively examined by using second-harmonic US with a second-generation contrast agent and multiphasic helical CT. Thirty-six patients had one lesion, and four patients had two lesions. Surgical resection in nine patients and imaging follow-up in 31 patients were used to determine the outcome. RESULTS: On contrast-enhanced US images, masses were classified as Bosniak category II (n = 18), IIF (ie, lesions were classified as category II and follow-up was needed) (n = 16), III (n = 7), or IV (n = 3) lesions. On CT images, masses were classified as Bosniak category II (n = 24), IIF (n = 10), III (n = 7), or IV (n = 3) lesions. Interobserver agreement was high (kappa = 0.86, P < .001) for classification with US. Complete concordance between the readers was found for classification with CT. Complete concordance between contrast-enhanced US and CT was observed in the differentiation of surgical and nonsurgical complex cysts. Complete concordance among the three readers in the assessment of vascularity with contrast-enhanced US was found. Interobserver agreement in the evaluation of enhancement on CT images was high (kappa = 0.88, P < .001). Concordance between contrast-enhanced US and CT in the evaluation of vascularization was high (kappa = 0.77, P < .001). CONCLUSION: The study data suggest that contrast-enhanced second-harmonic US is appropriate for renal cyst classification with the Bosniak system.     

Cystic tumors of the kidney in adults: radio-histopathologic correlations

The purpose of this study is to provide an updated pathologic-radiologic classification of cystic renal tumors and to assess imaging diagnostic capabilities. Eighty seven cases of cystic renal tumors explored with multimodality imaging (ultrasonography, CT, MRI, arteriography) and with histopathologic correlation are reported. The most common cystic carcinomas were multilocular cystic renal cell carcinoma (33%) and the pseudocystic necrotic carcinoma (31%), which usually belong to category IV. Less common cystic carcinomas were unilocular cystic renal cell carcinoma (6%) and renal cyst wall carcinoma (6%). The association of thin septa and large locules are suggestive findings for multilocular cystic nephroma, but such criteria are not specific enough to recognize benign multilocular cystic nephroma and to exclude multilocular cystic renal cell carcinoma. Since carcinomatous degeneration may occur within the wall of such tumors, especially in von Hippel Lindau disease, surgery is still required. The results of our study corroborate the Bosniak classification of cystic renal masses: no tumors belonged to the category I or II, all cystic masses which belonged to the category IV were malignant tumors, category III included benign and malignant tumors.     

Follow-up CT of moderately complex cystic lesions of the kidney (Bosniak category IIF)

OBJECTIVE: The purpose of this study is to show the use of follow-up CT studies in the management of moderately complex cystic lesions of the kidney (Bosniak category IIF). MATERIALS AND METHODS: The CT scans of 42 moderately complex cystic renal masses (Bosniak category IIF) with follow-up examinations for 2 years or greater or with pathology correlation (n = 3) were retrospectively analyzed by the authors in consensus. The complexity of each lesion was assessed on the basis of the number and appearance of the septa, wall thickness, interface with the kidney parenchyma, presence and amount of calcification, and contrast enhancement characteristics. Lesion size was measured in two dimensions. Follow-up examinations were evaluated for any interval change. RESULTS: The average size of the lesions was 3.9 x 3.6 cm, and the average follow-up time was 5.8 years (range, 2 years-18 years 4 months; median, 5.0 years). Eighteen lesions had fewer than five septa, 16 lesions had between five and nine septa, and eight lesions had more than nine septa. In 39 lesions, the wall or septa or both were slightly thickened, and in a single lesion, the wall and septa were hairline thin. The two remaining lesions were of uniformly high attenuation and completely intrarenal. Forty-one lesions had a sharp interface with the kidney, whereas one had an indistinct interface. Twenty lesions contained calcium. Enhancement was not shown in any lesions except for minimal enhancement of smooth walls or septa of some lesions. Follow-up examinations showed that three lesions had developed more calcification, one lesion had increased in overall size but appeared less complex, and three lesions had decreased in size. In addition, two lesions had become more complex and developed thicker septa, and these lesions proved to be cystic neoplasms. CONCLUSION: Follow-up CT studies are an effective way of managing patients with moderately complex cystic lesions of the kidney (Bosniak category IIF) because the absence of change supports benignity and progression indicates neoplasm.     

Calcification in cystic renal masses: is it important in diagnosis?

PURPOSE: To determine whether the presence of calcifications in cystic renal masses is important in diagnosis and to suggest an approach to the management of calcified cystic renal masses. MATERIALS AND METHODS: Eighty-one cystic renal masses containing calcification in a wall or septum were evaluated by means of review of computed tomographic (CT) images (n = 81), follow-up CT images (n = 28), and results of pathologic examination (n = 40) by the authors in consensus. Images were evaluated for lesion size, amount and morphology of calcification, and any association of calcification with soft-tissue structures. Lesions were categorized according to the Bosniak cyst classification system; the amount of calcification was determined with a subjective grading system. Progression of calcification was qualitatively determined with available follow-up CT scans. RESULTS: Twenty-one lesions were Bosniak category II (benign) and showed small amounts and thin strands of calcification. Nineteen lesions containing more extensive calcification but no enhancing tissue were category IIF. Follow-up CT results available for 16 of these lesions (average follow-up length, 5 years 8 months) showed no substantial change. The three remaining lesions were proved benign at surgery. Twenty-five lesions were category III; surgical intervention was performed in 21 of these (benign, n = 12; malignant, n = 9). Sixteen lesions that contained obvious areas of enhancing soft tissue were category IV and proved malignant at surgery. CONCLUSION: Calcification in a cystic renal mass is not as important in diagnosis as is the presence of associated enhancing soft-tissue elements. This information should enable a reasonable approach to the management of calcium-containing renal cystic lesions.     

Assessment of cystic renal masses in children: Comparison of multislice computed tomography and ultrasound imaging using the Bosniak classification system

To retrospectively compare contrast-enhanced multislice computed tomography (MSCT) and ultrasound (US) imaging for the assessment of cystic renal masses in children using the Bosniak classification system. Twenty-two consecutive patients (age 1 month to 5.2 years, mean 2.4 years) with 24 cystic renal masses (7 benign, 17 malignant) pathologically confirmed after surgical resection underwent both MSCT and US imaging, and were retrospectively analyzed using the Bosniak classification. A senior and a junior radiologist retrospectively and independently reviewed imaging findings. The sensitivity, specificity, positive predictive value and negative predictive values of MSCT and US were assessed using diagnostic statistics. The statistical significance of differences was determined by the McNemar test. Both radiologists accurately predicted lesions of categories I and IV with the Bosniak classification using MSCT and US. All masses classified as Bosniak classes I and II were proven to be benign, and all malignant lesions were correctly characterized in all cases both on ultrasound images and on the contrast-enhanced CT (CECT) images. Two benign multilocular cystic nephromas and one multicystic dysplastic kidney were classified into category III or even IV based on the classification scheme because of their multilocular nature and thick septation. The diagnostic accuracy of CECT was slightly better than ultrasound (CECT vs. US: senior reader, 92% vs. 88%; junior reader, 88% vs. 83%). However, there was no statistically significant difference between the two sets (p > 0.05). The two radiologists had perfect inter-observer agreement on the two modalities. Both MSCT and US provide highly accurate diagnosis for the malignant renal cystic masses in children using the Bosniak classification system, but assessment of benign masses still needs improvement. We would recommend US is the best screening modality in Bosniak I and II, In Bosniak III and IV, MSCT are first the choice.     

肾脏囊性病变的MSCT表现及Bosniak分级在其中的应用

目的：讨论肾脏囊性病变的MSCT表现及Bosniak分级在肾脏囊性病变中的应用价值。方法：前瞻性分析我院肾脏囊性病变Mscr表现同时进行Bosniak分级,其中取得病理证实的有26例,将Bosniak分级结果与病理结果对照。结果：Bosniak Ⅰ级中2例都为良性,Ⅱ级4例都为良性,Ⅱ／F级3例,1例恶性（1／3）,Ⅲ级恶性3例（3／8）,Ⅳ级中9例都是恶性。结论：诊断肾脏囊性病变要注意影像特征,Bosniak分级对于诊断、指导治疗均有帮助,但Bosniak分级对于ⅡF级、Ⅲ级囊性病变存在不足之处。     

Cystic renal masses: accurate Bosniak classification requires adequate renal CT

OBJECTIVE: The objective of this study was to assess the practical usefulness of the Bosniak classification system for separating surgical from nonsurgical cystic renal masses in a large number of patients examined with properly performed renal CT. The study included only patients whose scans were technically adequate to allow proper assignment of the lesion to a category. MATERIALS AND METHODS: The scans of 109 patients were gathered from two large teaching institutions both prospectively and retrospectively, yielding a total of 116 analyzable renal cystic lesions. Eighty-two masses were resected from 77 of these patients, retrospectively categorized by two experienced uroradiologists using the Bosniak classification system, and correlated with pathology reports. A second group of 34 lesions in 32 patients with atypical cysts was followed up prospectively for periods ranging from 3 months to 10 years. RESULTS: The results were similar for the two institutions: 15 resected categories I and II lesions were correctly identified as benign, and all 18 category IV lesions were malignant. Twenty-nine (59%) of 49 pooled category III masses were malignant. No malignancies have been identified in the prospectively monitored group of patients. CONCLUSION: Our results are compared with earlier, smaller series and support those that show that the Bosniak classification system is useful in separating lesions requiring surgery from those that can be safely followed up, provided proper CT techniques are used.     

多层螺旋CT结合Bosniak分级在肾囊性肿物诊断中的价值

目的 评价多层螺旋CT(MSCT)结合Bosniak分级对肾囊性肿物的诊断价值. 资料与方法 回顾性分析经手术、病理证实的109例患者共129个肾囊性占位术前MSCT的影像表现,并根据肾囊性占位的CT征象对其进行Bosniak分级;将MSCT的Bosniak分级结果与病理进行对照分析,判断各个级别中恶性囊肿的发生率;采用logistic回归分析预测Ⅰ～Ⅳ级中恶性肾囊肿的可靠CT征象. 结果 129个囊性肿物中,17个为恶性,112个为良性.对129个Ⅰ~Ⅳ级囊性病灶的CT特征进行logistic回归分析,结果显示实性成分强化是预测恶性肾囊肿的唯一可靠征象. 结论 高分辨CT结合Bosniak分级对大部分囊性肿物能够准确诊断;实性成分强化是预测恶性囊性肿物的唯一可靠征象.     

Bosniak分级在MRI诊断肾脏复杂囊性病变中的应用

目的：探讨Bosniak分级在MRI诊断肾脏复杂囊性病变中的应用.方法：41例经病理证实的肾脏复杂囊性病变,恶性28例,良性13例.观察其MRI表现,进行Bosniak分级.并与病理及手术结果进行对照.结果：恶性、良性两组分隔数量大于4的病变比例分别为67.9%和23.1%,差异有显著性意义（P=0.007）.恶性组中囊壁或分隔增厚的病变中88.2%可见不规则增厚,明显高于良性组的28.6%（P=0.009）.9例病变实性成分大于25%,6例有假包膜征象,病理证实均为恶性.恶性、良性组中病变有明显强化分别占85.7%扣23.1%,差异有显著性意义（P〈0.001）.强化征象诊断恶性的敏感度、特异度和符合率分别为82.6%、76.9%和82.9%.恶性组Ⅱ～Ⅳ级病变和Ⅱ～ⅡF级病变比例分别为89.3%和10.7%,良性组为30.8%和69.2%,差异有显著性意义（P〈0.001）.结论：增强仍是MRI Bosniak分级和良性鉴别的最可靠征象,囊壁和分隔的增厚、实性成分比、分隔数量及假包膜等征象也有重要诊断价值.     

卵巢勃勒纳瘤的CT表现及病理特点

目的：探讨卵巢勃勒纳瘤的CT表现及病理特点,提高对卵巢勃勒纳瘤的影像诊断及鉴别诊断水平。方法：搜集经手术病理证实的6例卵巢勃勒纳瘤患者的临床及影像资料,对肿块的位置、大小、结构、钙化及强化程度等CT表现以及对其病理改变进行回顾性分析。6例勃勒纳瘤均行根治切除术,术后未行放化疗,随访时间为术后3年。结果：6例肿瘤均位于单侧,形态不规则,密度不均,其中5例为良性,1例为交界性。良性者CT表现为囊实性,以囊性为主,内见分隔;其中4例增强后实性部分及分隔呈轻度强化表现,囊性成分无强化;3例合并卵巢囊腺瘤。1例交界性病灶呈实性改变,增强后呈中等度强化。全部病例中肿瘤实性部分均可见钙化。术后3年内CT随访6例患者均无明显复发及转移征象。结论：囊实性肿块的实性部分广泛多形性钙化及常合并卵巢囊性瘤为卵巢勃勒纳瘤的CT特点,有助于其诊断和鉴别诊断。     

Computed tomography of ovarian masses

A retrospective analysis of CT images in 138 histologically proven ovarian masses in 100 patients was undertaken to evaluate the usefulness and limitation of CT in the diagnosis of ovarian tumors. Benign masses were purely cystic in 98 (94.2%) and had solid component (including thickened walls, thickened septa, papillary projections) in five of 104 lesions (4.8%) on CT. These five masses, which are classified as benign solid tumors, could not be differentiated from malignant tumors by either the size of the solid portion or the intensity of contrast enhancement. In the malignant tumors a solid portion was detected in 32 of 34 tumors (94%). When a solid component is detected in an ovarian mass, the mass should be considered malignant although a few cases will be benign solid tumors. In Krukenberg tumors, which were all of gastric origin, the solid component was so large that it occupied more than one-half the mass. Therefore, if the solid portion of the ovarian mass is large on CT, upper gastrointestinal study should be performed to rule out Krukenberg tumor.     

Differentialdiagnose fokaler Nierenläsionen in CT und MRT

The great majority of renal masses are found incidentally as a result of the use of ultrasonography, computed tomography (CT) and magnetic resonance imaging (MRI). If ultrasonography is not diagnostic CT or MRI should be initiated to differentiate lesions of the kidney that need surgical intervention from those that do not and from those that need follow-up examinations.Cystic renal masses are characterized by using the Bosniak classification, including category IIF. In solid lesions of the kidney first non-surgical lesions as well as lymphoma, renal infarction and nephritis should be excluded. Identifying fatty components in renal lesions is very important because in angiomyolipoma they are almost always present.CT and MRI are exellent for tumor detection. Careful evaluation of imaging finding combined with the patient′s history should assist the radiologist in making the proper diagnosis or recommending the appropriate treatment in most cases.This article provides a review about renal masses, the imaging methods for their evaluation and their characteristic features at CT and MR imaging. Different lesions are demonstrated like xantogranulomatous pyelonephritis, acute pyelonephritis, renal infarction, lymphoma, angiomyolipoma, renal oncocytoma, cystic lesion and polycystic disease the kidney, echinococcosis, renal cystadenoma, metastases, renal cell carcinoma (RCC), and multiple bilateral RCC in patients with Hippel-Lindau-Syndrome.This article should help to differentiate complex cystic lesions of the kidney by using the Bosniak-classification, especially Bosniak Category IIF. Solid masses should be characterized and the major question to be answered is whether the mass represents a surgical or nonsurgical lesion or if follow-up studies are necessary.     

Cystic renal tumors: US and CT findings

Cystic renal tumors represent a variety of lesions in which both solid and liquid components coexist. These lesions may be either benign or malignant and include the multilocular cystic nephroma (MCN), the renal cell carcinoma (RCC), and the papillary adenocarcinoma (PAC). The MCN is a rare neoplasm formed of multiple loculated cystic masses divided by septa. The tumor is benign, although there are some rare reports of malignant cases. The RCC and the PAC may appear with cystic patterns. This is rather uncommon for the RCC, which inside has a unilocular or multilocular cystic appearance, if the necrotic component is large. PAC is an infrequent renal tumor, which has a greater tendency to appear as a large mass with a unilocular large cystic space. The ultrasonography (US) and computed tomographic (CT) features of 27 cystic tumors are presented. Both US and CT allowed the recognition of the cystic components, the septa, and the vegetations. The two imaging techniques made it possible to distinguish the tumors into “unilocular” and “multilocular” masses: the former correspond to RCC and PAC, the latter to MCN and RCC. CT added some information on calcified or partially calcified tumors. CT more than US enabled the differentiation between the malignant RCC and the benign MCN for which conservative surgery may be indicated. The two techniques did not allow the differentiation between RCC and PAC, which has different prognostic behavior.     

Role of Interface Sign and Diffusion-Weighted Magnetic Resonance Imaging in Differential Diagnosis of Exophytic Renal Masses

PurposeWe aimed to investigate the role of interfaces of exophytic solid and cystic renal masses on magnetic resonance imaging (MRI) and the added value of diffusion-weighted imaging in differentiating benign from malignant lesions.MethodsThe Institutional Review Board approved this retrospective study, and informed consent was waived. A total of 265 patients (109 [41%] women and 156 [59%] men) with a mean age of 57 ± 12 (standard deviation) years were enrolled in this study. Preoperative MRI (n = 238) examinations of patients with solid or cystic renal masses and MRI (n = 27) examinations of patients with Bosniak IIF cysts without progression were reviewed. Solid/cystic pattern, interface types and apparent diffusion coefficient (ADC) values were recorded by 2 radiologists. The diagnostic performance of combining normalized ADC values with interface sign were evaluated.ResultsAmong 265 renal lesions (109 cystic and 156 solid), all malignant lesions (n = 192) had a round interface. No malignant lesions showed an angular interface. For prediction of benignity in cystic lesions, sensitivity (82.86% vs 56.16%), negative predictive value (92.50% vs 85.71%), and accuracy (94.50% vs 87.92%) ratios of angular interface were higher compared to all (solid plus cystic) lesions. The best normalized ADC cutoff values for predicting malignancy in lesions with round interface were as follows: for all (solid plus cystic), ≤ 0.75 (AUROC = 0.804); solid, ≤ 0.6 (AUROC = 0.819); and cystic, ≤ 0.8 (AUROC = 0.936).ConclusionsAngular interface can be a predictor of benignity for especially cystic renal masses. The evaluation of interface type with normalized ADC value can be an important clue in differential diagnosis especially in patients avoiding contrast.