Comparison of computed tomography and magnetic resonance imaging in the assessment of complex renal cysts by using the Bosniak classification.

INTRODUCTION AND OBJECTIVES

The Bosniak classification of cystic renal lesions was first published in 1986 based on computed tomography (CT). In the present study, we aimed to investigate the effect of magnetic resonance imaging (MRI) on Bosniak category compared with CT, and to determine how this effect changed the treatment modality in the evaluation of complex renal cysts.

MATERIAL AND METHODS

Data of 144 patients were collected retrospectively. After exclusion criteria, 102 cystic renal lesions with a Bosniak category of at least IIF on CT or MRI between 2013 and 2016 were evaluated by 2abdominal radiologists. The demographic data, Bosniak category, interobserver agreement, and pathologic data of patients who underwent surgery were recorded.

RESULTS

The coherence between MRI and CT was 75.5%. The Bosniak classification of 17 patients was upgraded with MRI, and the treatment modality changed in 10 patients, and they underwent surgery. The Bosniak category was downgraded from III to IIF in 6 patients out of 8 whose Bosniak category was downgraded with MRI and the treatment modality changed. Surgery was performed in one patient out of these 6 patients, and the pathology was reported as benign. Progression was detected in the follow-up at month 18 of 1 patient out of 5, and surgery was performed. The pathology was reported as renal cell carcinoma. The pathology result was reported as RCC in 35 (68.6%) patients out of 51 who underwent surgery. Progression was detected in 7 patients out of 51 who were followed up (13.7%), and the pathology results were reported as RCC. The majority of the malignant tumors were low stage and grade.

CONCLUSIONS

MRI may be successfully used in the evaluation of renal cystic lesions. In particular, the challenging Bosniak IIF and all Bosniak III lesions must be evaluated using MRI before making the decision for surgery. The upgrading of Bosniak category with MRI is more possible compared with CT due to its high-contrast resolution, therefore further studies are required to identify whether it was the cause of overtreatment of Bosniak III lesions.