Perioperative Ursodeoxycholic Acid for Renal Protection in Adults Undergoing Partial Nephrectomy for Renal Tumors

The goal of this clinical trial is to learn if ursodeoxycholic acid, also called UDCA, can help protect kidney function in adults undergoing partial nephrectomy for kidney tumors. It will also learn about the safety of UDCA when used around the time of surgery. Before the randomized part of the study begins, the first 6 participants will receive UDCA in a safety run-in phase. These participants will be closely monitored for side effects, laboratory abnormalities, and other medical problems to assess the preliminary safety and tolerability of perioperative UDCA administration. If no unacceptable safety concerns are identified, the study will proceed to the randomized, placebo-controlled phase. The main questions this study aims to answer are: 1. Is perioperative UDCA administration safe in patients undergoing surgery for renal tumors? 2. Does UDCA lower the risk of acute kidney injury within 48 hours after partial nephrectomy? 3. Does UDCA reduce the decline in kidney function after surgery? 4. Does UDCA increase blood levels of UDCA and related bile acids during the perioperative period? 5. What medical problems do participants have when taking UDCA around the time of surgery? 6. Researchers will also evaluate whether UDCA affects urinary biomarkers of kidney injury. Researchers will compare UDCA with a placebo, a look-alike substance that contains no active drug, to see if UDCA can help protect the kidney from ischemia-reperfusion injury during partial nephrectomy. Participants will: 1. Take UDCA or a placebo three times a day from 2 days before surgery until 5 days after surgery. 2. Undergo partial nephrectomy as planned by their treating surgeon. 3. Have blood tests before and after surgery to check kidney function, liver function, and bile acid levels. 4. Participants will provide urine samples before and after surgery for the assessment of kidney injury biomarkers. 5. Be monitored for side effects, surgical complications, and other medical problems during