Nephrectomy is a surgical procedure of choice for patients suffering from renal cell carcinoma (RCC). Even though the laparoscopic approach is considered to cause fewer complications and reduce hospital stay, open surgery is still often performed. Open nephrectomy causes significant acute postoperative pain, and it can also lead to the development of chronic postoperative pain. Pain management is important for the overall recovery of patients undergoing major surgery such as open nephrectomy and it is a part of the enhanced recovery after surgery (ERAS) program. In this prospective randomized clinical study, we plan to compare two different approaches to pain management regarding the level of acute pain (first 72 hours), side effects, systemic analgesics consumption, and hospital stay. Our hypothesis are that intrathecal opioid administration significantly reduces acute postoperative pain compared to epidural analgesia in patients undergoing open radical or partial nephrectomy. We also hypothesize that the intrathecal opioid administration is associated with a lower incidence of adverse effects compared to epidural analgesia and shorter ICU length of stay.