Title : Inferior rectal nerve block for proctological surgery: A technical note
Abstract:
Background: Day-case proctological surgery is commonly performed under general anaesthesia, which can be cumbersome and inefficient for often short-duration procedures, with prolonged recovery and excessive resource use. The inferior rectal nerve block provides anatomically targeted anaesthesia to the perianal region while avoiding anaesthetising a large area of sensory distribution. It allows for faster recovery, quicker patient turnover, avoids general anaesthetic risks and provides adequate analgesia. This is a new technique currently in use at Oxford University Hospitals for day-case proctological surgery.
Technique: Inferior rectal nerve block can be performed under titrated intravenous sedation administered by an anaesthetist, using agents such as propofol in combination with fentanyl, prior to block administration. A combination of lidocaine 1% (20mls) and Bupivacaine 0.5% (20mls) is used to provide both short and long-acting anaesthesia to make a total of 40mls. Following sedation, the patient is positioned in either left lateral or lithotomy position and the injection site is identified at the anal verge. The needle is inserted at a 45° angle in the anal verge at 9 o’clock and directed posterior-inferiorly towards the natal cleft. Approximately 15mls of local anaesthetic is injected, followed by partial needle withdrawal and redirection superiorly, maintaining a 45° angle and an additional 5mls is injected to ensure circumferential spread along the inferior rectal nerve trajectory. The technique is repeated on the contralateral side at 3 o’clock to complete a total of 40mls of local anaesthetic infiltration.Clinical application: Inferior rectal nerve block is suitable for day-case proctological procedures, including polypectomy, skin tag excision, haemorrhoidal artery ligation operation, fissurectomy and examination of the rectum under anaesthesia. In addition, it can provide effective analgesia in acute presentations such as thrombosed haemorrhoids or severe anal fissures.
Benefits: This technique provides effective intra- and post-operative analgesia, supports efficient theatre turnover in the day-case setting and encourages early patient mobilisation and discharge. Additionally, avoiding general anaesthesia minimises airway manipulation and cardiorespiratory depression which enhances patient safety.
Conclusion: Inferior rectal nerve block provides a safe, anatomically precise regional anaesthesia. It is an excellent option for day-case proctology in appropriately selected patients who are suitable for local anaesthesia and have no contraindications to regional techniques.
