MRI and Microbiota Analysis in Constipation

Inclusion Criteria: * Meets Rome III Criteria for diagnosis of Functional Constipation5 on questionnaire (NB. Both those who do and do not meet IBS criteria will be eligible) * At least one bowel motion per week while taking usual laxatives * Able to give informed consent * Aged 18 or older Exclusion Criteria: * History declared by the candidate of other pre-existing gastrointestinal disorder, including but not limited to: * Inflammatory Bowel Disease * Coeliac Disease diagnosed in the last year * Pancreatitis * Cancer of the gastrointestinal tract * Any reported history of gastrointestinal resection (excluding appendicectomy or cholecystectomy) * Presence of an intestinal stoma * Pregnancy declared by candidate (no formal testing) * Contraindications for MRI scanning i.e. metallic implants, pacemakers, history of metallic foreign body in eye(s) and penetrating eye injury * Reported alcohol intake of \>28 units/ week with daily drinking * Any use of a product containing ispaghula or psyllium in the 4 weeks prior to consent * Unable to avoid use of dihydrocodeine or morphine during the study * If taking other regular opiates such as codeine, fentanyl or Oxycodone, participants should be able to maintain a stable dose throughout the study * Any reported history of hypersensitivity or significant adverse reaction to ispaghula, maltodextrin or bisacodyl * Unable to stop drugs and other agents used primarily for their laxative effect, during periods of screening, washout, baseline and treatment (maximum 15 days - rescue medication will be provided). * Antibiotic or prescribed probiotic treatment in the past 4 weeks * Inability to lie flat or exceed scanner limits of weight \<120kg * Poor understanding of English language * Participation in any medical trials for the past 3 months * Any condition where the candidate is likely to require a course of antibiotics in the next 3 months e.g. severe chronic respiratory disease, recurrent urinary tract infection, lower limb ulceration * Judgement by the PI that the candidate who will be unable to comply with the full study protocol e.g. Diabetes, severe COPD During the screening 2 weeks off laxatives * No bowel motions recorded during screening period * ≥3 complete spontaneous bowel motions (CSBMs - bowel motion with the feeling of complete evacuation, without the use of rescue therapy in the preceding 24 hours) per week