Ultrasound-guided lateral kidney biopsy in patients unsuitable for the prone position.

Background: Kidney biopsy is the gold standard diagnostic technique for nephrologists. Appropriate patient positioning facilitates physiological stability and access to target anatomy. Factors such as patient weight, size and medical history, including respiratory or circulatory disorders, should guide position selection. However, most kidney biopsies are performed exclusively in the prone position and procedures are often deferred when this is not feasible. Although lateral kidney biopsy has been reported, it remains uncommon and its applications are not well established. We aimed to demonstrate the safety and utility of lateral kidney biopsies. Methods: We retrospectively reviewed patients who underwent lateral kidney biopsy at Toranomon Hospital Kajigaya between October 2015 and February 2025. Vital signs and blood test results pre- and post-biopsy were analysed. Results: Twenty-five patients underwent lateral kidney biopsies; six had abdominal aortic aneurysms (AAAs), 12 had respiratory distress (7 with massive ascites or pleural effusions, 2 with obesity, 2 with organomegaly and 1 with pericardial effusion), 6 had major joint pain (4 thin, 1 with scoliosis and 1 with arthritis) and 1 had stoma. All patients were histologically diagnosed and received appropriate treatment. Vital signs remained stable and only one patient with splenomegaly experienced a bleeding complication, which was not readily predictable and unlikely related to biopsy position. Conclusions: Lateral kidney biopsy offers a viable alternative for the accurate diagnosis of kidney diseases in patients in whom the prone position is challenging, including those with AAA, anasarca-induced respiratory distress or significant joint pain due to body habitus.