US-guided renal transplant biopsy: efficacy of a cortical tangential approach.

PURPOSE: To describe the cortical tangential approach to ultrasonographically (US) guided renal transplant biopsy and evaluate its efficacy in obtaining sufficient cortical tissue.
MATERIALS AND METHODS: This HIPAA-compliant retrospective study was exempted from review by the institutional review board. Informed consent was not required. The number of core biopsy samples, glomeruli, and small arteries obtained during 294 consecutive US-guided renal transplant biopsies in 254 patients (134 men, 120 women; age range, 19-79 years; mean age, 52.2 years) in one department between June 1 and December 31, 2008, were recorded, along with any ensuing complications. Procedural success was assessed according to Banff 97 criteria.
RESULTS: There were 1.2 +/- 0.4 (standard deviation) biopsy core samples taken per case by 11 radiologists using the cortical tangential approach. In 290 cases, biopsy results showed 21.7 +/- 10.1 glomeruli and 5.0 +/- 2.8 small arteries. Two hundred seventy-six (95%) cases were adequate or minimal according to Banff 97 assessment criteria. Of the 14 inadequate cases (5%), six were lacking only one glomerulus to achieve minimal status. Only one biopsy core sample was taken in all 14 inadequate cases and in 233 successful cases (success rate, 85%). None of the 43 cases with two or more biopsy core samples taken were inadequate (success rate, 100%). Two patients (0.7%) had a hemorrhagic complication requiring transfusion, and another four patients (1.4%) experienced a minor self-limiting complication.
CONCLUSION: The cortical tangential approach can be used by a cohort of radiologists to achieve 95% or higher collective success in obtaining cortical tissue during renal transplant biopsy, with few complications. The success rate is higher, without increased complications, when more than one core specimen is taken.