Perioperative UDCA to Protect Kidney Function in Partial Nephrectomy

1\. Inclusion Criteria

Patients must meet all of the following criteria to be eligible for inclusion in the study:

1. The patient has fully understood the study and has voluntarily signed the informed consent form (ICF);
2. Male or female patients aged 18 to 75 years, inclusive, at the time of signing the ICF;
3. Imaging diagnosis consistent with stage T1 renal tumor, as assessed by MRI or CT;
4. No definite collecting system invasion on preoperative MRI or CT assessment;
5. The patient is scheduled to undergo partial nephrectomy (PN) or renal tumor enucleation after clinical evaluation by the physician and full discussion with the patient;
6. Preoperative assessment indicates that main renal artery clamping with warm ischemia is planned;
7. The surgery will be performed by a surgeon with experience in at least 50 cases of PN or renal tumor enucleation, and renal artery clamping will be performed using standardized vascular clamp application;
8. Screening eGFR ≥30 mL/min/1.73 m², calculated using the CKD-EPI equation;
9. No history of allergy or intolerance to UDCA or other bile acid preparations, and no UDCA contraindications or biliary tract-related diseases that, in the investigator's judgment, would make the patient unsuitable for UDCA treatment;
10. The subject is willing and able to comply with the scheduled visits, treatment, laboratory tests, and other study-related procedures required by the protocol.

2\. Exclusion Criteria

Patients meeting any of the following criteria will be excluded from the study:

1. Emergency surgery, defined as surgery required for medical reasons within 24 hours;
2. Patients who are considered preoperatively to have a significant risk of bleeding, or whose surgery is expected to require complex renal reconstruction, and who are judged by the investigator to be unsuitable for participation in this study;
3. Patients for whom non-standard ischemia techniques, such as selective/segmental arterial clamping or zero-ischemia techniques, are planned preoperatively;
4. Patients with a history of renal surgery on either kidney or previous kidney transplantation;
5. Solitary kidney;
6. History of major abdominal organ surgery within 1 year before surgery, which, in the investigator's judgment, may affect the conduct of the current surgery, safety assessment, or evaluation of study endpoints;
7. Active lesions or clinically significant imaging abnormalities in either kidney that may substantially affect renal function assessment or perioperative AKI risk evaluation, including but not limited to renal artery stenosis, polycystic kidney disease, chronic pyelonephritis, severe hydronephrosis, or renal atrophy;
8. Use of UDCA, chenodeoxycholic acid, bile acid sequestrants, or other drugs that may significantly affect bile acid metabolism within 1 month before screening;
9. Continuous or systemic use of nephrotoxic drugs for more than 1 week within 3 months before screening, including but not limited to nonsteroidal anti-inflammatory drugs and aminoglycoside antibiotics;
10. Continuous or systemic use of drugs that may significantly affect the gut microbiota or bile acid metabolism within 1 month before screening, including antibiotics, probiotics, high-dose glucocorticoids, immunosuppressants, potent laxatives, or antidiarrheal agents;
11. Participation in another interventional clinical study within 3 months before screening, or ongoing treatment with another investigational drug or device;
12. Uncontrolled active infection during the screening period, including but not limited to urinary tract infection, pulmonary infection, intra-abdominal infection, or systemic infection;
13. Uncontrolled blood pressure abnormalities during the screening period, including mean seated SBP ≥180 mmHg or DBP ≥110 mmHg; symptomatic hypotension, SBP \<90 mmHg, or hypovolemia as judged by the investigator;
14. History of New York Heart Association (NYHA) class III-IV heart failure, or hospitalization due to heart failure/fluid retention within 6 months before screening;
15. Hepatic impairment, defined as meeting any of the following criteria: history of hepatic encephalopathy, history of esophagogastric varices, history of portocaval shunt surgery, Child-Pugh class C hepatic impairment, ALT or AST \>3 × ULN, or total bilirubin \>2 × ULN during the screening period;
16. Diseases or surgical history that may significantly affect the absorption, distribution, metabolism, or excretion of the study drug, including but not limited to:

1\. history of active inflammatory bowel disease within the previous 6 months; 2. history of major gastrointestinal surgery, such as gastrectomy, gastrointestinal anastomosis, or bowel resection; 3. history of gastrointestinal ulcer and/or gastrointestinal or rectal bleeding within the previous 6 months; 4. history of pancreatic injury or pancreatitis within the previous 6 months; (17) Pregnant or breastfeeding women; (18) Women of childbearing potential who have a positive pregnancy test during the screening period, or who are unwilling to use effective contraception during the study; (19) Patients with a history of other malignancies are excluded, except for malignancies confirmed to have been cured or in remission for ≥5 years, radically resected basal cell carcinoma or squamous cell carcinoma of the skin, or carcinoma in situ at any site； (20) Any other severe or uncontrolled medical disease, psychiatric disorder, or laboratory abnormality that may increase the risk associated with study participation, affect subject compliance, or interfere with the interpretation of study results, including but not limited to organ failure, active or uncontrolled immunodeficiency disease, active or uncontrolled HBV/HCV/HIV infection, cognitive impairment, or severe psychiatric disorder.