Pseudo-obstruction Assessment With MRI

Inclusion Criteria: * Ability to give informed consent * Sufficient level of English language to understand study information and respond to symptom questionnaires * CASES: a clinical diagnosis of primary or secondary Chronic Intestinal Pseudo-Obstruction, excluding adhesional obstruction. PICs will be asked to send clinical documentation that the diagnosis has been confirmed on crosssectional imaging. * CONTROLS: a Chronic constipation disorder diagnosed according to Rome IV criteria for functional constipation, constipation-predominant irritable bowel syndrome or opioid-induced constipation (diagnostic criteria as listed in Lacy et al 2016) Exclusion Criteria: * Inability to tolerate 400 ml liquid challenge meal (oral or through established gastrostomy; according to self-assessment) * Contra-indication to MRI scanning, such as metal implants, pacemaker etc * Pregnancy declared by candidate (no formal testing) * Inability to stop short-acting medications likely to alter small bowel motility, such as antiemetics, fast release opioids, laxatives, and anti-diarrhoeals, on the day before the study (24h before baseline scan; i.e. a total of circa 30h) as well as antibiotics for three days before the study. This only applies to long-term antibiotics commonly given for dysbiosis (small intestinal bacterial overgrowth). A short course of antibiotics given for acute infections will not be interrupted but the study day will be delayed until the course is finished. Patches, long acting formulations such as slow release medication or depot injection medication will be allowed to continue * Inability to omit parenteral nutrition for 12 hours before the fasting MRI scan (\~16h total) * Medical comorbidity that means subject will not be able to undergo multiple scans e.g. severe respiratory disorder limiting time lying flat; severe musculoskeletal disorder limiting mobility * Previous small bowel resection (excluding ileostomy, insertion of venting tube or percutaneous endoscopic gastrostomy, appendectomy or cholecystectomy). Patients who have had a colectomy for their CIPO will be eligible. * Other gastrointestinal disorder likely to alter small bowel function e.g. uncontrolled coeliac disease, Crohn's disease. A diagnosis of small intestinal bacterial overgrowth will not be a reason for exclusion. PICs will be asked to supply information on resections and comorbidities for CIPO participants.