22-04: Kidney Biopsy

Indications for percutaneous needle biopsy include (1) unexplained AKI or CKD; (2) unexplained proteinuria and hematuria; (3) previously identified and treated lesions to guide future therapy; (4) systemic diseases associated with kidney dysfunction, such as systemic lupus erythematosus (SLE), anti-GBM disease (Goodpasture syndrome), and granulomatosis with polyangiitis (eFigure 22–3), to confirm the extent of renal involvement and to guide management; and (5) kidney transplant dysfunction, to evaluate for transplant rejection or other causes of AKI. Importantly, kidney biopsies should only be performed if the results will influence the treatment plan or facilitate discussion about prognosis; patients unwilling to accept therapy based on biopsy findings should not undergo kidney biopsy. Relative contraindications include a solitary or ectopic kidney (exception: transplant allografts), horseshoe kidney, ESRD, congenital anomalies, and multiple cysts. Absolute contraindications include an uncorrected bleeding disorder; severe uncontrolled hypertension; renal infection; renal neoplasm; hydronephrosis; or uncooperative patients, including those who are unable to lie flat for the procedure.

Prior to a kidney biopsy, patients should not use medications that prolong clotting times, and blood pressure should be less than 160/90 mm Hg. Blood work should include hemoglobin concentration, platelet count, prothrombin time, and partial thromboplastin time. After a biopsy, hematuria occurs in nearly all patients, although less than 10% will have macroscopic hematuria. Patients should remain supine for 4–6 hours postbiopsy and should be closely monitored when the hemoglobin is more than 1 g/dL lower than baseline by 6 hours postbiopsy.

Percutaneous kidney biopsies are generally safe. The major risk is bleeding, which may occur up to 72 hours postbiopsy. More than half of patients will have at least a small hematoma; approximately 1–5% of patients will experience significant bleeding requiring a blood transfusion. Anticoagulation therapy should be held for 5–7 days postbiopsy if possible. The risks of nephrectomy and mortality are about 0.06–0.08%. When a percutaneous needle biopsy is technically not feasible and kidney tissue is deemed clinically essential, a closed biopsy via interventional radiologic techniques or open biopsy under general anesthesia can be performed.