Untethered microrobots offer the possibility to perform medical interventions in anatomically complex and small regions in the body. Presently, it is necessary to access the upper urinary tract to diagnose and treat Upper Tract Urothelial Carcinoma (UTUC). Diagnostic and treatment challenges include ensuring adequate tissue sampling, accurately grading the disease, achieving completeness in endoscopic treatment, and consistently delivering medications to targeted sites. This work introduces microgrippers (µ-grippers) that are autonomously triggered by physiological temperature for biopsy in the upper urinary tract. The experiments demonstrated that µ-grippers can be deployed using standard ureteral catheters and maneuvered using an external magnetic field. The μ-grippers successfully biopsied tissue samples from ex vivo pig ureters, indicating that the thin-film bilayer springs' autonomous, physiologically triggered actuation exerts enough force to retrieve urinary tract tissue. The quality of these biopsy samples is sufficient for histopathological examination, including hematoxylin and eosin (H&E) and GATA3 immunohistochemical staining. Beyond biopsy applications, the µ-grippers' small size, wafer-scale fabrication, and multifunctionality suggest their potential for statistical sampling in the urinary tract. Experimental data and clinical reports underscore this potential through statistical simulations that compare the efficacy of µ-grippers with conventional tools, such as ureteroscopic forceps and baskets.