In the era of routine use of cross-sectional imaging, there is an ever-increasing incidence of small renal masses (SRMs; <4 cm) and not surprisingly, a concomitant increase in surgery for these lesions.¹ Despite the increase in surgical procedures performed, there is a negligible improvement in overall survival.² This is likely due to fact that up to 30% of SRMs are treated with radical nephrectomy, leading to loss of functional nephrons and the sequalae of chronic kidney disease such as the need for dialysis and cardiovascular disease.^3,4 More worryingly, up to 20% of SRMs surgically extirpated are benign on final pathology.⁵ Despite this, the traditional paradigm of surgical extirpation first followed by histological diagnosis continues to persist in the urological community.

Renal mass biopsy (RMB) is a safe, highly sensitive, and specific diagnostic test. A recent bivariate meta-analysis reported a sensitivity of 96.7%, specificity of 94.4%, and a positive predictive value of 98.8%.⁶ In addition to being highly accurate, RMB is a safe procedure, with complication rates ranging from 1.4% to 4.7% and a major complication rate of only 0.46%.⁷ RMB not only provides a histological diagnosis, but also serves as a risk stratification tool with the potential to change management decisions such as proceeding with active surveillance or less invasive ablative treatments. Despite the above, only 8% of urologists perform biopsy in more than 20% of their SRM patients, and 73% of urologists rarely or never perform biopsy.⁸ Common reasons cited for the rare or never RMB approach include concerns that biopsy would not alter management (80%), provide a false-negative (60%), provide a false-positive (10%), result in complications (20%), or seed the biopsy needle tract with malignant cells (8%).⁹ Furthermore, only 2% of urologists perform RMB independent of an interventional radiologist.¹⁰

The current standard of care for RMB includes a core or fine needle aspiration biopsy performed by an interventional radiologist in a hospital-based setting. This is usually followed by 4-24 hours of observation postprocedurally. Recently, multiple studies have shown that incorporating an office-based approach to RMB not only is safe and effective, but also can reduce costs and increase access for patients with SRMs. This raises the question, why aren’t more urologists performing these in the office? Below we summarize the recent literature with regard to RMB in an office-based setting.

Dave et al in 2015 reported their initial 5-year experience of 108 patients who underwent US-guided RMB in an office-based setting.¹¹ Their initial diagnostic rate was 87% with 14 of 108 patients (13%) having a nondiagnostic result. All patients with a nondiagnostic biopsy who were rebiopsied revealed renal cell carcinoma. The overall accuracy for histological subtype was 97.8%, and the histological grade concordance was 53.7%. The surgical complication rate was 2.8%, with all complications being Clavien-Dindo grade I and recognized within 1 hour of the procedure. All patients were discharged after 1 hour of observation, and none required hospitalization. Of the 108 patients biopsied, 25.9% went on to active surveillance based on the biopsy results. Even patients with T1b masses benefited from RMB, with 25% of biopsies revealing histology other than renal cell carcinoma (eg angiomyolipoma, lymphoma). Nine (22.5%) of these patients ultimately avoided invasive surgery as a result of their RMB.

Similarly, our team at the University of California, Irvine in 2021 reported our experience of 72 patients who underwent office-based US-guided RMB.¹² A comprehensive protocol for office-based RMB was provided. This included a prebiopsy consultation and patient selection. Patients with high-quality cross-sectional imaging within 3 months and posterior lesions in nonhilar locations with adequate skin-to-tumor distance were selected for biopsy. All patients were treated with topical 2.5% lidocaine cream (Emla cream) 2 hours prior to the procedure. Biopsy was performed in a prone position under US guidance following the injection of 1% lidocaine along the biopsy tract. A 13.8-cm 18-guage Max-Core biopsy needle through a US probe needle guide was used to target and biopsy the lesions. On average, 3 to 5 cores were taken. Following biopsy, all patients were observed for 1 hour prior to discharge.

The initial diagnostic rate for RMB was 80%, which improved to 93% on repeat biopsy. The overall histological grade concordance was 46% for low (Fuhrman grade I/II) vs high (Fuhrman grade III/IV). Of the patients who underwent RMB, 34.7% went on to active surveillance based on the results of the biopsy. Compared to patients who did not undergo biopsy, the portion of surgically excised benign tumors was 8-fold lower in the RMB group (3% vs 23%). There were no complications in this patient cohort, and only 7% patients required narcotic prescription after the procedure.

Office-based US-guided RMB is a safe and effective procedure. As demonstrated above, RMB can affect management decisions, reduce the number of unnecessary surgical procedures, and in turn reduce morbidity and mortality. A recent study demonstrated that the mean time from diagnosis to definitive management was only 34 days in patients who underwent office-based RMB.¹³ Similarly, Dutta et al reported cost savings of approximately $2,500 USD ($2,129 vs $4,598) for office-based RMB compared to hospital settings.¹⁴ If urologists expand their skill set to include RMB, this can improve patient comfort, reduce costs, and increase patient access and continuity of care. The current paradigm regarding RMB needs to change, and eventually pretreatment RMB for all renal masses can become mainstream. The addition of office-based urologist-directed RMB is certainly an excellent step toward this goal. Time to stop shooting first and asking questions later.