Renal cell carcinoma (RCC) accounts for 2-3% of all cancers and is a common malignancy of the genitourinary tract. Open nephrectomy, performed through midline, subcostal, or flank incisions, remains a standard treatment but often results in significant postoperative pain, leading to respiratory muscle dysfunction, increased pulmonary complications, and prolonged hospital stays.

Acute surgical pain arises from inflammatory responses, activation of spinal pain pathways, and muscle spasms. While postoperative pain typically improves during recovery, some patients develop chronic postsurgical pain (CPSP), lasting at least two months postoperatively.

Opioids and epidural analgesia are commonly used for pain control, but their side effects and invasiveness necessitate safer, effective alternatives. Ultrasound (US)-guided peripheral nerve and field blocks have become integral to multimodal analgesia. One such technique, the **external oblique intercostal plane block (EOIPB)**, was introduced as a modification of fascial plane blocks, targeting anterior and lateral cutaneous nerves (T6-T10). EOIPB offers advantages over quadratus lumborum block (QLB) and erector spinae plane block (ESPB) by being performed in the supine position and providing superior midline analgesia compared to serratus intercostal plane block (SIPB).

Similarly, the transversus abdominis plane (TAP) block, particularly the posterior approach, delivers analgesia from T7 to T12 by anesthetizing anterior and lateral cutaneous nerve branches. While case series suggest EOIPB may be effective for post-nephrectomy pain, comparative studies between EOIPB and posterior TAP block in open nephrectomy:

Aim of the Study:

To evaluate the postoperative analgesic effects of posterior transversus abdominis plane (TAP) block and external oblique intercostal plane block (EOIPB) in patients undergoing open nephrectomy under general anesthesia.

Inclusion Criteria:

• Patients whom diagnosed as having renal carcinoma and scheduled for open nephrectomy under general anesthesia.
• ASA class II- III.
• Age ≥ 18 and ≤ 70 years.
• Body mass index (BMI) less than 40kg/m2.

Exclusion Criteria:

1. Patient refusal.
2. Hepatic and renal insufficiency.
3. Unstable cardiovascular or pulmonary disease.
4. History of psychiatric and cognitive disorders.
5. Patients with known sensitivity or contraindications to the drug used.
6. Patients on regular opioid consumption.