Follow-up for Bosniak category 2F cystic renal lesions.

PURPOSE: To determine percentage of Bosniak category 2F complex cystic renal masses that progress to malignancy based on serial follow-up studies,and to determine if there are demographic and/or imaging features associated with progression. MATERIALS AND METHODS: This retrospective study was institutional review board-approved with waiver of informed consent. Hospital database system was searched from January 1, 1996, to May 1, 2011, for category 2F cysts studied with contrast agent-enhanced computed tomography or magnetic resonance imaging and followed with serial contrast-enhanced imaging. Demographics of patients and imaging features of lesions that progressed were compared with those that did not. The relationship of these features to progression or stability was assessed by using χ(2), Fisher exact, or Cochran Armitage trend tests. RESULTS: Identified in 144 patients (98 men, 46 women; age range, 31-83 years; average, 63 years) were 156 category 2F lesions. Follow-up studies were from 6 months to 13 years (median, 3.6 years; average, 4.2 years). Nineteen of 156 lesions progressed to category 3 or 4 in 6 months to 3.2 years; 17 lesions (89.5% of those that progressed and 10.9% of initial 2F lesions) were malignant and two were benign. To date, no patients had recurrent or metastatic disease. Men had significant risk for progression to malignancy (P = .003). Of 17 category 2F lesions that progressed to malignancy, 12 were endophytic (P = .02). Category 2F lesions with minimally irregular septa (nine of 17; P= .001) or wall (seven of 17; P = .016), and lesions with indistinct parenchymal interface (nine of 17; P < .001) were associated with progression to cancer. A multilobulated border was not associated with progression (P = .999). CONCLUSION: Based on this study, 10.9% (17 of 156) Bosniak category 2F cystic lesions progress to malignancy, and progression occurs within 6 months to 3.2 years.

The Bosniak renal cyst classification: 25 years later.

In the past 25 years, there have been continuous advances in the diagnosis of disease throughout the body owing to the introduction of new technology and the experience gained with its use. However, the imaging and evaluation of complicated cystic lesions of the kidneys frequently remains a difficult problem. The classification of renal cystic lesions suggested 25 years ago, now referred to as the Bosniak renal cyst classification, remains pertinent to the diagnosis and management of these difficult-to-diagnose complicated cystic masses.

Multilocular cystic renal cell carcinoma: comparison of imaging and pathologic findings.

OBJECTIVE: The purpose of this study was to retrospectively correlate the imaging and pathologic features of multilocular cystic renal cell carcinoma (RCC), a low-grade neoplasm that has an excellent prognosis. MATERIALS AND METHODS: Institutional databases were searched for the period between 2001 and 2010 to identify cases of resected renal tumors that had been evaluated with CT or MRI and been analyzed by a uropathologist to confirm the histologic diagnosis of multilocular cystic RCC. The images (nine CT, 14 MRI) were reviewed, and a Bosniak cyst category was assigned. RESULTS: Of 23 confirmed cases of multilocular cystic RCC, imaging revealed seven lesions were Bosniak category IIF, 13 were category III, and three were category IV. Pathologic examination of the category IIF lesions revealed 99% fluid, 0.001-1% clear cells lining the septum, and 0% fibrosis. The category III lesions were 98-99% fluid, 1-2% clear cells, and 0% fibrosis. The category IV lesions were 20-40% fluid, 1-5% clear cells, and 60-80% fibrosis. The patient demographics were similar across groups. Clinical follow-up showed no evidence of recurrent or metastatic disease. CONCLUSION: Multilocular cystic RCC is a rare cystic lesion of the kidney that is low risk to the patient and benign in behavior. It has a variable imaging pattern, the Bosniak category ranging from IIF to IV. As multilocular cystic RCC lesions increase in complexity on images (higher Bosniak category), there is a corresponding increase in the volume of malignant cells lining the tumor and an increase in the presence of vascularized fibrous tissue. Regardless of the imaging appearance, the behavior of these tumors was benign in this study. Clinicians and radiologists should be aware that when this carcinoma is reported to occur, the patient has an excellent prognosis.

MDCT urography with high-volume low-concentration i.v. contrast material, peroral hydration, i.v. furosemide, and i.v. saline: qualitative and quantitative assessment in 100 consecutive patients.

OBJECTIVE: The purpose of this study is to qualitatively and quantitatively assess MDCT urography performed with a high volume of low-concentration (240 mg I/mL) i.v. contrast agent supplemented with peroral hydration, i.v. furosemide, and i.v. saline. MATERIALS AND METHODS: This retrospective evaluation of 100 consecutive normal MDCT urograms was performed for clinical indication of hematuria; patients (76 men and 24 women) were 27-90 years old (mean [± SD] age, 60 ± 15 years). Three radiologists evaluated the degree of opacification across six urinary tract segments (for a total of 1200 measurements per radiologist) on a 4-point scale (0-3). One radiologist measured the maximum short-axis diameter of the proximal, mid, and distal ureters in each patient. Mean opacification scores were calculated for each segment. Radiologist agreement was assessed by kappa coefficient and Spearman rank correlation. Ureteral diameter was correlated to degree of opacification using the Jonckheere-Terpstra trend test. A comparison with published studies using similar scoring methods was undertaken. RESULTS: Of 1200 measured ureteral segments, a total of 24 among the three radiologists were reported as nonopacified. The mean opacification scores ranged from 2.63 ± 0.8 to 3.00 ± 0.8. Calculated kappa coefficients are indicative of substantial agreement (> 0.61). The mean maximal ureteral diameters were 5.44 ± 1.10, 6.32 ± 1.54, and 5.32 ± 1.55 mm for the proximal, mid, and distal ureters, respectively. For all three radiologists, the mean opacification scores increased as distention increased. The Spearman correlation and corresponding p value (p < 0.001) for the association between the distention with the opacification scores show significant correlation. The opacification scores and ureteral distention exceeded published results. CONCLUSION: An MDCT urography technique using high-volume low-concentration i.v. contrast, oral and i.v. hydration, and i.v. diuretic reliably optimizes urinary tract opacification and distention. A positive correlation was found between ureteral distention and opacification.

MRI findings of angiomyolipoma of the renal sinus in 5 cases.

The magnetic resonance imaging (MRI) appearance of 5 cases of angiomyolipoma (AML) centered in the renal sinus is presented. All cases exhibited similar imaging findings, including well-circumscribed margins, minimal perceived enhancement without soft tissue components, insinuation around the renal collecting system, and localized hydrocalicosis with associated localized renal parenchymal atrophy but without generalized hydronephrosis. Findings in some cases included extension out of the renal sinus and presence of aneurysmal vessels. Although identification of a renal parenchymal defect has been reported to be useful for the differentiation of a large exophytic AML from a perirenal liposarcoma, none of the cases in our series demonstrated this finding on MRI. To our knowledge, there have been only 2 previous reported cases showing the cross-sectional imaging appearance of an AML of the renal sinus without a renal parenchymal defect. In view of the shared and characteristic imaging features of the 5 cases in our series, we believe that the diagnosis of this condition can be strongly suggested by MRI despite the absence of a visible parenchymal defect. While histology remains the only way to definitively establish the diagnosis, the typical imaging appearance of this entity should enable conservative management with follow-up imaging in an asymptomatic patient. In some cases, embolization and needle biopsy could be used to avoid a surgical approach.

Pitfalls in renal mass evaluation and how to avoid them.

Characterization of renal masses with computed tomography (CT) and magnetic resonance (MR) imaging is usually clear-cut and accurate. However, potential pitfalls exist in diagnosis of renal masses, and it is necessary to understand these pitfalls to avoid misdiagnosis and possibly unnecessary surgery. Although some of the pitfalls are related to technical factors of the CT and MR imaging equipment, others are related to errors in image interpretation. To maximize detection and characterization of renal masses, the study should include images obtained before and after administration of intravenous contrast material, including images obtained during the nephrographic phase of enhancement. One should be aware of the potential unreliability of absolute Hounsfield unit measurements and of the existence of possible CT pseudoenhancement. When CT results are indeterminate, MR imaging may be helpful in demonstrating enhancement in renal masses. Before diagnosing a renal mass as a malignant neoplasm or suggesting surgery for a renal mass, one should consider alternative benign diagnoses; when appropriate, previous images or a supporting history should be obtained.

CT and MR imaging of complications of partial nephrectomy.

The standard treatment for renal cell carcinoma for many years was radical nephrectomy, but in the past decade there has been a trend toward elective nephron-sparing surgery. Initially, partial nephrectomy was performed with an open surgical approach; more recently and with increasing frequency, a laparoscopic approach has been used in selected cases. Nephron-sparing surgery with either approach is more complex than is traditional radical nephrectomy and more frequently results in complications. The possible complications of partial nephrectomy include vascular, collecting system, and technical complications as well as recurrent tumor and infection. For prompt diagnosis and appropriate management of these complications, radiologists must be familiar with normal and abnormal features in the postoperative appearance of the kidney at computed tomography and magnetic resonance imaging.

Renal imaging for diagnosis and staging of renal cell carcinoma.

The development and expansion of CT and MRI technology have enhanced the detection and characterization of renal lesions. Although these advancements should lead to earlier diagnosis of renal cell carcinoma with subsequent improved cure rates, the increased imaging has also uncovered many cases that are problematic not only in diagnosis but in management as well. The performance of high-quality examinations combined with growing experience should improve the ability to diagnose and manage these cases successfully. Continued advances in CT and MR technology combined with the current trend toward minimally invasive surgery will continue to expand the role of preoperative imaging and, it is hoped, improve the cure rate of renal cancer.

MR imaging of cystic renal masses.

MR imaging has proven to be an important imaging modality in the evaluation of cystic renal masses. Because it is becoming more widely used, it is necessary to be able to characterize cystic renal masses accurately using MR imaging alone. We review the indications for the use of MR imaging and discuss the findings present in a variety of cystic renal masses. The role of MR imaging in the characterization of cystic lesions of the kidney is summarized and compared with the CT findings in the Bosniak renal cyst classification. It is expected that the increasing experience with the use of MR imaging in cystic renal masses will add to our ability to diagnose and manage these cases successfully.

How I do it: evaluating renal masses.

With modern computed tomography (CT) and magnetic resonance (MR) imaging equipment, the diagnosis of most renal masses is usually straightforward and accurate. The major question to be answered is whether the mass represents a surgical or nonsurgical lesion or, in some cases, if follow-up studies are necessary. This evaluation usually can be accomplished if a high-quality examination is performed, if the clinical history of the patient is kept in mind, if conditions that mimic a renal neoplasm are considered and excluded, and if there is an awareness of the potential pitfalls and limitations of CT and MR imaging. In this article, the authors present their technique in the performance of CT and MR imaging examinations, summarize their approach to the diagnosis of renal masses, review the imaging findings in these lesions, and stress the limitations in renal mass diagnosis.

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.

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.

CT differentiation of large exophytic renal angiomyolipomas and perirenal liposarcomas.

OBJECTIVE: The purpose of our study was to describe the imaging findings and CT characteristics that lead to accurate distinction of large exophytic renal angiomyolipomas from retroperitoneal perirenal liposarcomas, which at times can be confused on imaging studies and even at pathologic examination. MATERIALS AND METHODS: We retrospectively analyzed CT images of 15 large exophytic renal angiomyolipomas and 12 well-differentiated perirenal liposarcomas. Pathologic correlation was available for six of 15 angiomyolipomas and all of the liposarcomas. All examinations were evaluated for lesion size, renal parenchymal defect, enlarged vessels, kidney displacement, lesion encapsulation or margination, associated hemorrhage, and additional angiomyolipomas. The records of patients with tuberous sclerosis or the forme fruste of that condition were excluded from the study. RESULTS: The average size of the angiomyolipomas was 14 x 10 cm. They showed a renal parenchymal defect (n = 15), enlarged vessels (n = 12), renal displacement (n = 14), good margination without a distinct capsule (n = 14), hemorrhage (n = 1), and additional (one or two) angiomyolipomas (n = 4). The average size of the liposarcomas was 18 x 11.6 cm. They showed enlarged vessels (n = 3), renal displacement (n = 11), and encapsulation (n = 4); none showed a renal parenchymal defect, hemorrhage, or associated angiomyolipomas. CONCLUSION: Although large exophytic angiomyolipomas and well-differentiated retroperitoneal liposarcomas may have similar appearances on imaging, careful evaluation for a defect in the renal parenchyma combined with the presence of enlarged vessels in angiomyolipomas should enable accurate differentiation in almost all cases. Achieving an accurate diagnosis can have a significant impact on patient treatment.