Evaluation of Bladder Wash as an Alternative Specimen for Postmortem Toxicology: Comparison to Screening Results of Urine and Kidney Tissue

ABSTRACT Urine specimens represent the gold standard for screening analyses in forensic toxicology, but they are not always available postmortem. In this case, alternative specimens must be considered. The current study aimed to systematically evaluate bladder wash (BW) as an interesting, but largely unexplored specimen for screening in FT, comparing drug detection in BW against urine and kidney tissue (KT) in authentic cases. The study included 60 consecutive postmortem cases. BW was obtained by injecting 10 mL of a 0.9% NaCl solution into the empty bladder and sampling the entire fluid with the same syringe. KT (ca. 5 g, grinded) was placed into a tube of dialysis membrane and left for dialysis against water (3×, 40–80 mL, 24 h), followed by evaporation/reconstitution. All specimens were analyzed by immunoassay, an untargeted LC–MS$^{n}$ screening approach and a targeted LC–MS/MS analysis. In total, 95 different compounds from the drug classes of, among others, stimulants, opiates/opioids, benzodiazepines, antidepressants, and antipsychotics could be detected. Sensitivity for drug detection in BW using immunoassay or untargeted MS/MS was lower than for urine but comparable to that of KT, which is in line with much lower drug concentrations in these matrices compared with urine. Applying a targeted LC–MS/MS method or a more concentrated sample preparation workflow could increase detection sensitivity in BW. Given the easier handling of BW in the laboratory (identical to urine), its use proved superior to KT and represents a promising new strategy for cases without available urine samples.