Establishing stone composition from pure dust: feasibility and analytic yield of FTIR spectroscopy during suction-assisted flexible ureteroscopy.

Abstract

The shift toward dust-only flexible ureteroscopy (FURS) prevents routine metabolic stone analysis due to a lack of retrievable fragments. We evaluated the technical success, analytical yield, and composition profile of Fourier-transform infrared (FTIR) spectroscopy performed on stone dust collected via flexible navigable suction access sheaths (FANS). This prospective single-center study included 109 patients undergoing FURS with FANS for upper tract stone disease. The surgeon aspirated the stone dust slurry into a container. Then, the fluid samples collected were sent to the lab to be centrifuged, washed with distilled water to remove any blood/protein artifacts, incubated until dried, and analyzed using FTIR spectroscopy. Dust aspiration reached a 100% analytical yield (109/109 cases), with all samples giving an interpretable FTIR reading. Calcium-based stones were the most common (64.2%, n = 70), consisting of Calcium Oxalate Monohydrate (51.4%, n = 56) and Calcium Oxalate Dihydrate (12.8%, n = 14). Uric Acid was identified in 26 cases (23.9%), followed by Carbonate-Apatite (6.4%, n = 7), Cystine (3.7%, n = 4), and Struvite (1.8%, n = 2). There was a strong relation between pre-operative CT density and the primary dust component (p < 0.001), with Uric Acid stones displaying significantly lower density (611.8 ± 263.2 HU) than Calcium Oxalate Monohydrate (1146.7 ± 335.7 HU). Aspirating stone dust during FURS provides a viable sample for FTIR spectroscopy, challenging the assumption that dust-only lithotripsy is inadequate for stone analysis and demonstrating a feasible, high-yield alternative when solid fragments are unretrievable.