Impact of biopsy route, muscle pathway, and cortex target on safety and diagnostic yield in ultrasound-guided renal parenchymal biopsy.

PURPOSE: To compare the safety and diagnostic yield of two ultrasound (US)-guided percutaneous renal biopsy (PRB) approaches, lateral to medial and medial to lateral, which differ in access route, muscle groups traversed, and cortical targets.

METHODS

This retrospective study included 490 patients (mean age: 38.2 ± 21.2 years; 267 men, 223 women) who underwent US-guided PRB between 2019 and 2024 and had abdominal computed tomography (CT)/magnetic resonance imaging (MRI) within 1 year. At the left kidney lower pole level (L3-L4), anterior-posterior thicknesses of the traversed muscle groups were measured on CT/MRI. Complications were classified according to the Society of Interventional Radiology guidelines. Diagnostic yield was categorized as optimal (≥ 12 glomeruli), suboptimal (≥ 3 glomeruli), and pathologist based (diagnostic according to final pathology assessment). Group comparisons were performed using the chi-square test, Fisher's exact test, and t-test.

RESULTS

In 490 PRBs (237 lateral to medial, 253 medial to lateral), the medial-to-lateral approach, despite traversing thicker muscles (35.7 vs. 11.5 mm, P = 0.001), produced smaller hematomas (8.6 vs. 17.3 mm, P = 0.001) with similar complication rates (major: 3.6% vs. 3.4%, P = 0.913; minor: 36% vs. 33.8%, P = 0.608). Diagnostic adequacy was comparable, but optimal yield was higher with the medial-to-lateral route (85.0% vs. 73.0%, P = 0.001).

CONCLUSION

Both approaches demonstrated comparable safety. However, the medial-to-lateral route was associated with smaller hematomas and a higher proportion of optimal biopsies from the lateral cortex, but suboptimal and pathologist-based adequacy remained high in both techniques.

CLINICAL SIGNIFICANCE: When standard lower pole lateral cortex biopsy is not feasible due to cortical scarring, cysts, overlying skin lesions, or anatomic limitations-especially in patients for whom contralateral biopsy is not possible (e.g., solitary or ectopic pelvic kidney, severe unilateral hydronephrosis)-alternative cortical targets must be used. Understanding how different access routes and muscle pathways influence hemorrhage control and diagnostic yield helps operators choose the safest and most effective technique in these situations.