Inclusion Criteria:  Age: 2-10 years. Weight: 15-40 kg. Sex: both males and females. ASA physical status: 1-II. Operation: surgery below the umbilicus.  Exclusion Criteria:  Allergic reaction to local anesthetics (LAs). Local or systemic infection (risk of meningitis). Intracranial hypertension. Hydrocephalus. Intracranial hemorrhage. Coagulopathy. Hypovolemia. Parental refusal. Spinal deformities, such as spina bifida or myelomeningocele. Presence of a ventriculoperitoneal shunt because of a risk of shunt infection or dural leak.