Assessment of Urinary Microplastic Concentration in Patients With Urolithiasis: A Prospective Case-Control Study

Urinary stone disease is a common urological condition with a multifactorial etiology. Although established metabolic, dietary, genetic, and environmental factors contribute to stone formation, the potential role of microplastic exposure in urinary stone disease remains insufficiently understood.

In this prospective observational case-control study, patients diagnosed with kidney or ureteral stones and healthy control participants will be evaluated. Following informed consent, demographic and clinical data will be collected. A midstream urine sample will be obtained from each participant for laboratory analysis.

Urine samples will undergo laboratory processing for the detection and characterization of suspected microplastic particles. The analytical process will include centrifugation, Proteinase K treatment, membrane filtration, microscopic examination, image analysis using ImageJ, and Fourier-transform infrared (FTIR) spectroscopy for polymer identification.

In participants with urinary stones, available stone specimens will also be analyzed for stone composition. Imaging-derived stone characteristics, including stone size, localization, and density in Hounsfield units, will be recorded.

The primary objective is to compare urinary microplastic burden between participants with urinary stones and healthy controls. Secondary analyses will investigate the relationships between urinary microplastic burden and stone characteristics, including stone size, density, localization, and composition.

The study does not involve administration of investigational drugs, use of investigational medical devices, or additional invasive procedures. Participation will involve collection of a urine sample and collection of clinical data obtained during routine clinical care.

Inclusion criteria

• Participants will be eligible if they are 18 years of age or older, are able to provide informed consent, and meet the criteria for either the urinary stone group or the healthy control group. Participants in the urinary stone group will have a diagnosis of kidney or ureteral stone disease. Healthy controls will have no current or previous diagnosis of urinary stone disease.

Exclusion criteria

• Participants will be excluded if they are unable or unwilling to provide informed consent, have an active urinary tract infection at the time of urine sample collection, are pregnant, or are unable to provide an adequate urine sample for laboratory analysis. Participants will also be excluded if the urine sample is considered unsuitable or significantly contaminated during laboratory processing.