Needle Size and the Risk of Kidney Biopsy Bleeding Complications

To the Editor: The percutaneous renal biopsy is an essential tool in the diagnosis and evaluation of kidney disease. Most renal biopsies are performed under direct ultrasound guidance with automated biopsy needles, techniques that have substantially reduced the risks of the procedure. However, the kidney biopsy still carries a considerable risk of bleeding complications. Although certain risk factors for bleeding, including hypertension, acute kidney injury, female sex, and older age, have been well documented, the association between the biopsy needle size and the rate of bleeding complications is unclear. Major complications, including hemorrhage requiring transfusion, angiographic intervention, nephrectomy, or death, have been reported in only around 2%–8% of renal biopsies, whereas minor complications, such as hematoma, are seen in anywhere from 17% to 33%. Hematoma formation found on renal ultrasound is a direct assessment of post-biopsy bleeding and may be a more sensitive measure of bleeding than overt anemia or hemodynamic instability. At our institution, post-biopsy ultrasounds are routinely obtained as standard of care after kidney biopsy. We therefore conducted a retrospective cohort study of patients who underwent kidney biopsy, using postbiopsy hematoma as the endpoint of interest when comparing 14G versus 16G needles. The study was conducted at Brigham and Women’s Hospital in Boston, MA, between August 2014 and January 2016. We captured all biopsies that were performed under the supervision of a single nephrology attending, allowing for minimal variation in how procedures in our cohort were supervised and performed. The biopsies captured comprise the large majority of the ultrasound-guided renal biopsies conducted during the period of the study. During the period of the study, the standard of care switched from the use of 14G to 16G needles, based on anecdotal observations of excessive numbers