Fetal renal biopsy: technique development

Fetal/neonate kidneys obtained at the time of autopsy were utilized to determine a suitable needle biopsy gauge to obtain renal parenchyma for histologic evaluation. Twenty-one fresh kidney specimens from 11 fetuses/neonates between 16-40 weeks gestation were used to obtain needle biopsies using 20-, 18-, 16-, and 14-gauge biopsy catheters. The specimens were graded according to the presence of normal histologic features of renal parenchyma. Seventy-five renal biopsies were obtained. The biopsy histology was interpreted using a grading system based on the presence of normal features of the renal parenchyma. Sixty-three (84%) of the samples were graded histologically as adequate (cortex or medulla present). Samples with both cortex and medullary structures present (completely adequate) were obtained in 39/63 (62%) of these adequate biopsies. The 14- and 16-gauge biopsy catheters gave the best results, respectively yielding 79 and 69% completely adequate biopsies. This is in contrast to the 20- and 18-gauge catheters that respectively yielded 35 and 25% completely adequate biopsies. Our initial results indicate that adequate kidney biopsies can be obtained. However, the current technique is associated with core sample disruption when the smaller gauge catheters are used. This could account for the low rate of completely adequate samples with the smaller gauge catheters. A different sampling technique is needed to overcome sample disruption, to determine the smallest catheter gauge that will yield a suitable tissue sample for histologic evaluation.