Most renal masses can be diagnosed by imaging techniques, but when the nature of the lesion is not distinguishable on imaging, definitive diagnosis often requires biopsy. Richter and associates assessed the diagnostic accuracy of image-guided biopsy of renal masses that were indeterminate by noninvasive imaging techniques.

The retrospective study included 517 cases of renal masses that required image-guided biopsy because of indeterminate findings on renal imaging. Computed tomographic (CT)–guided biopsy was performed in 245 patients, ultrasound-guided biopsy in 82 patients and fluoroscopically controlled biopsy in 190 patients. The authors evaluated the accuracy of CT- and ultrasound-guided biopsy. Patients were followed for five years after the biopsy if the lesion was benign. If the results suggested malignancy, surgical exploration was performed at the time of the biopsy.

CT-guided biopsy led to a diagnosis in 214 (87 percent) of the 245 patients who underwent this procedure. In the 82 patients who underwent ultrasound-guided biopsy, a diagnosis was made in 54 (65.8 percent). Overall, CT- or ultrasound-guided biopsy established a diagnosis in 76.4 percent of the patients. Follow-up revealed that the diagnosis proved to be inaccurate in 1.4 percent of the cases. In 23.5 percent of the patients, the image-guided biopsy was unable to assist a definitive diagnosis with acceptable confidence, and surgical exploration was required.

The authors conclude that a CT-guided biopsy of a renal mass considered to be indeterminate on imaging studies is a safe and reliable method of establishing a diagnosis in most cases. Use of the image-guided biopsy can significantly reduce the management problems physicians face when evaluating patients with renal masses that cannot be definitively identified as solid or cystic.