To compare the analgesic efficacy of posterior TAP block versus ESPB after PCNL surgery. The hypothesis is that posterior TAP block, as a part of multimodal analgesia, will reduce pain and opioid consumption like ESPB

Percutaneous nephrolithotomy (PCNL) is currently the gold standard for treatment of patients with large and complex renal calculi because it is less invasive than open surgery. The sources of acute pain after PCNL are visceral pain originating from kidneys and ureters, and somatic pain from the site incision. PCNL is usually done in 10th to 11th intercostal space or in the subcostal area. Complete blockade of unilateral spinal nerves from T10 to L2 can provide sufficient analgesia during PCNL. This can be achieved by several regional techniques such as thoracic paravertebral block, transversus abdominis plane (TAP) block, erector spinae plane block (ESPB).

ESPB is an interfascial block which can provide wide sensory blockade from T2-4 to L1-2 that was first described in 2016. ESPB can be performed by injecting the local anesthetic in the deep interfascial plane of the erector spinae muscle with nearly one dermatome for each 3.4 ml of the injected volume. This allows ESPB to provide both visceral and somatic analgesia. TAP block is a regional injection of a local anesthetic agent between the transversus abdominis and internal oblique muscle planes. TAP block affects the sensory nerves of the anterolateral abdominal wall (T6-L1). Various technical modifications in TAP block have been described including lateral, posterior, subcostal, and continuous catheter techniques. The posterior approach should be the preferred technique in clinical practice as it provides longer somatic and visceral analgesia that are not offered with the lateral approach.

Inclusion Criteria:

• Patients scheduled for PCNL under general anesthesia
• ASA status I-II

Exclusion Criteria:

1. Contraindications to regional block (coagulopathy, infection at the needle insertion site or known allergy to amide local anesthetics)
2. Patient who has difficulty understanding the study protocol or patient refusal.
3. Chronic respiratory disease patients.
4. Diabetic patients.
5. Body mass index (BMI) > 30 Kg/m2
6. Routine corticosteroids, pain medication, or anticonvulsant.
7. Psychiatric diseases.