Infracoccygeal Botox for Dyssynergia

Background: Constipation is a common problem, affecting up to 20% of the population during their lifetime. Some patients respond poorly to standard treatments such as laxatives. A subgroup of these have dyssynergic defaecation where the muscles that control bowel movements fail to relax during pushing, preventing evacuation of stools. Currently, the mainstay of treatment requires muscle retraining by a therapist using a technique called biofeedback. Patients in whom biofeedback has failed are left with few options, one of which includes Botox injection into the pelvic floor muscles involved in the defaecation process. However, current method of injection is inaccurate and often requires anaesthesia. The investigators propose a novel technique for Botox delivery which reduces the risks and associated costs. Objectives: 1. The primary objective is to demonstrate technical feasibility of percutaneous infracoccygeal Botox injection as an alternative to transanal puborectalis muscle injection for the treatment of dyssynergic defaecation. 2. The secondary objectives are to assess the safety and acceptability of this technique, and to derive pilot clinical effectiveness data to inform future studies. Methods: The investigators will carry out Botox injection into the puborectalis muscle under ultrasound guidance in the outpatient department. This will be done by percutaneous injection below the coccyx where the puborectalis has been demonstrated to be easily accessible. An electromyography of the puborectalis is obtained before the injection to demonstrate proof of mechanism. The investigators will collect data using a combination of questionnaires, patient baseline data, and anorectal physiology test results before and after the treatment. Outcomes: * Feasibility: procedure duration, rate of identification of puborectalis by ultrasound scan and pre-injection EMG, procedure limitations, and successful injection rate * Safety: rate of adverse events * Acceptability: p