Efficacy of percutaneous renal biopsy in obese patients under computerized tomographic guidance

The performance of percutaneous renal biopsy under ultrasound guidance in markedly obese patients is associated with technical difficulties because of the production of poor image quality. Fluoroscopy can be potentially used as an alternative guidance method when the kidneys are not visualized sonographically. However, the presence of uremia in an obese patient imposes an additional risk when fluoroscopy is used because of possible nephrotoxicity from the use of radiocontrast dye. Computerized tomography (CT) provides advantages over these two methods because of the production of excellent spatial resolution of images leading to accurate localization of the kidneys. We performed 59 consecutive percutaneous renal biopsies in 58 patients using CT as guidance. The body mass index (BMI) defined as weight in kilograms/(height in meter)2 [Watson et al. 1979], was used to assess the severity of obesity. Twenty-nine patients had Grade 0 (BMI less than or equal to 24.9), 17 had Grade I (BMI 25-29.9), 7 had Grade II (BMI 30-39.9) and 5 had Grade III (BMI greater than or equal to 40) obesity. Thirty-two patients had superimposed uremia of varying degrees. Image quality was maintained in all four groups, and tissues adequate for diagnosis were obtained in 98% of the attempts. Complications were minimal with no deaths, nephrectomies or surgical interventions attributable directly to the biopsy procedure itself. We recommend the use of CT guidance in the grossly obese patients (Grade II or III) when their kidneys are poorly visualized by sonography.