Padronização da técnica de biópsia renal em felinos: rendimento glomerular de acordo com calibre da agulha, trajetória e região de coleta

Abstract

Renal biopsy is an effective procedure for diagnosing kidney diseases, guiding therapeutic decisions, and establishing prognosis; however, a minimum of 5–20 glomeruli is required for diagnostic adequacy. This study aimed to standardize the feline renal biopsy technique by identifying the ideal needle gauge and trajectory, as well as the renal region that maximizes glomerular yield while minimizing complications. Five feline cadavers without renal abnormalities were used. Four animals underwent renal biopsy using Tru-Cut needles (14G, 16G, and 18G) at the cranial pole, caudal pole, and lateral margin, following caudocranial and lateromedial trajectories (Tru-Cut group). One animal had its kidneys sectioned for virtual analysis, which involved glomerular counting using ImageJ software (virtual biopsy group), simulating biopsy samples obtained with specific needle gauges and renal regions. Statistical analysis included Friedman and paired Wilcoxon tests to compare needle gauges, intraclass correlation coefficient (ICC) to assess reproducibility, and logistic regression with generalized estimating equations (GEE) to evaluate complications such as needle transfixation and sample fragmentation. The results demonstrated a consistent hierarchy of glomerular yield: 14G > 16G > 18G, with statistically significant differences among all gauges. The caudocranial trajectory yielded a higher number of glomeruli than the lateromedial trajectory. Analysis by renal region showed that the lateral region consistently presented higher mean glomerular counts for the 16G and 18G needles. The ICC indicated moderate to good reproducibility for the 16G needle, whereas the 18G needle showed greater variability. The 16G needle was associated with a lower risk of sample fragmentation compared to the 18G, while the 14G needle caused macroscopic renal lesions in all punctures. The virtual biopsy model reproduced the hierarchical pattern among needle gauges but overestimated glomerular yield, indicating that technical factors reduce sampling efficiency. It was concluded that, in felines, renal biopsy should be performed in the lateral renal region, using a caudocranial trajectory and a 16G needle, in order to maximize glomerular yield and minimize the risk of complications.