A 35 year old woman presents with a 6 month history of intermittent abdominal pain, associated with bloating and usually relieved by defecation. She denies any weight loss or rectal bleeding but sometimes notices mucus in her stools. Over the past 6 weeks she has been buying Buscopan from the chemist which is quite effective. She has always struggled with constipation and has found increasing dietary fibre and fluids little benefit.
Given her likely diagnosis, what would be the next most appropriate step in management?