An important study looked at kidney biopsy metrics and adequacy that might be important for the Nephrology world.
To understand adequacy and variation of kidney biopsies done by nephrologists and radiologist, the investigators collected adequacy-associated data (%cortex, glomeruli, arteries, length) from consecutive native and allograft kidney biopsies over a 22-month period. In total, 1332 biopsies (native: 873, allograft: 459) were included, 617 obtained by nephrologists, 663 by radiologists, and 559 with access to on-site division. In summary, proceduralists with access to on-site evaluation had significantly lower inadequacy rates and better division of tissue for light microscopy (LM), immunofluorescence, and electron microscopy than those without access to on-site evaluation. Radiologists in this large study were significantly less likely to have access to on-site evaluation than nephrologists. On multivariate analysis for native kidney biopsies, the effect of having a radiologist perform the biopsy and having access to onsite division were both significant predictors of obtaining greater calculated amount of cortex for LM. Despite the trend for radiologists to obtain more tissue in general, biopsies from nephrologists contained
a greater percentage of cortex and were more likely to be considered adequate for LM (native kidney inadequacy rate for LM: 1.11% vs. 5.41%, P=0.0086).
This is the by far the largest data analysis that could provide useful feedback and/or benchmark data to kidney biopsy proceduralists. It also provides objective data on the critical role of on-site evaluation and division
of tissue for obtaining adequate biopsy tissue appropriately divided for LM, IF, and EM. As treating nephrologists, we feel this is important and can make a major difference in diagnosis and treatment.
Interestingly, in this study, for native kidney biopsies, the effect of having a radiologist perform the biopsy and having access to on-site division were both significant predictors of obtaining a greater calculated amount of cortex for LM. Despite the trend for radiologist obtaining more tissue in general, biopsies from nephrologists had a greater percentage of cortex and were more likely to be considered adequate for LM. Why is that? Cortex obtaining is critical and getting that sample is importantly taught to us as fellows and attendings doing kidney biopsies. If my differential is AIN and ATN, then the cortex-medulla might not make a big difference but for a GN diagnosis, getting a cortex and having enough sample for LM, IF and EM is critical.
In this study, the radiologists’ inadequate for LM rates for native kidney biopsies appeared be independent of on-site evaluation and authors suggest that this could be due to patient selection (with more challenging biopsies sent to radiology), could represent a long-term effect of lack of on-site evaluation, division, and feedback from pathologists, and/
or may be due to other factors. Sonogram assisted vs CT scan guided was not discussed in this study.
This is an important study and a reminder to the Nephrology world to continuing doing kidney biopsies as nephrologists. It is critical to get adequate samples and nephrologists do a better job at that. Having onsite evals of adequacy also allows for this to be better. Educating the radiologists on this important topic is also critical if Nephrologists are not going to be performing this procedure anymore in near future. An article in a high index radiology journal is much needed to raise this important issue.