Our primary objective is to compare the effectiveness of bilateral QLB and epidural analgesia for postoperative management using VAS measured in PACU until 24 hours after surgery in patients undergoing elective open nephrectomies under GA. The secondary outcomes include: The 1st time to rescue analgesia and total amount of opioid consumption throughout the first postoperative day. hemodynamic variables. Any complications as postoperative nausea and vomiting (PONV) and sedation. The sensory block coverage & the Bromage score at 2, 6, 12, and 24 hours after anesthesia recovery and duration of urinary catheter usage. Duration of PACU stay and postoperative duration of hospitalization and Patients' satisfaction.

Open surgery remains basic surgery for patients requiring radical or partial nephrectomy and is associated with a high incidence of intense immediate postoperative pain and chronic pain the months following surgery. The physiopathology of acute pain is explained as it is mediated by inflammatory cell infiltration, activation of the pain pathways in the spinal cord, and reflexive muscle spasm. All these three mechanisms of acute pain are typically ameliorated during the postoperative recovery. Regional anesthesia techniques are commonly enhanced for pain management in open nephrectomy as they decrease parenteral opioid requirements and improve patient satisfaction.

QLB has been introduced as a component of multimodal analgesia for thoracic and abdominal surgeries as:

cesarean section, hip arthroplasty, inguinal hernia repair and nephrectomies. It provides a great spread of local anesthesia which allows anesthesia from T6 - L2 and provides loss of somatic and visceral pain. The QLB was initially described by R.Blanco where the local anesthetic (LA) was injected at the anterolateral aspect of the QL muscle (type 1 QLB). Later, J.

Børglum used the posterior transmuscular approach by detecting Shamrock sign and injecting the LA at the anterior aspect of the QL (type 3 QLB). Recently, R. Blanco described another approach by injecting the LA at the posterior aspect of the QL muscle (type 2 QLB), which may be easier and safer as the LA is injected in a more superficial plane, so the risk of intra-abdominal complications and lumbar plexus injuries is less. Finally, the intramuscular QLB (type 4 QLB) was done by injecting LA directly into the QL muscle. QLBs may be particularly useful in nephrectomy as it lacks the adverse effects associated with patient controlled analgesia including nausea, vomiting, sedation, and respiratory depression, as well as side effects of patient controlled epidural analgesia such as pruritus hypotension, and urinary retention. Our hypothesis is that performing ultrasound guided QLB will be more superior or equal to epidural block in providing postoperative analgesia for patients undergoing open nephrectomy under general anesthesia

Inclusion Criteria:

• Patients of American Society of Anesthesiologists (ASA) class I or II physical status.
• Age:20-60 years old.
• Patients scheduled for open nephrectomies .
• Gender: both

Exclusion Criteria:

• Patient refusal.
• Significant organ dysfunctions (e.g., cardiac, respiratory, renal, or liver disorders).
• Morbid obesity (BMI >35).
• Patient with known hypersensitivity to amide local anesthetics or morphine.
• Patient with any contraindication for intrathecal anesthesia, e.g. coagulopathy.
• Psychiatric disorders, which will make observational pain intensity assessment difficult.
• Pregnancy.
• Skin lesions or wounds at the puncture site of the proposed block .

Any patient fulfilling the inclusion criteria participating in our study .