Understanding Abdominal Pain in IBD and IBS
Understanding Abdominal Pain in IBD and IBS
Abdominal pain is a central symptom of Inflammatory Bowel Disease (IBD) and Irritable Bowel
 Syndrome (IBS). IBD is an autoimmune disease characterized by inflammation of the
 gastrointestinal tract. IBS does not have clear biomarkers and is diagnosed based on symptom
 reports. The aim of this study is to explore biopsychosocial factors which may perpetuate
 and/or increase the severity of pain in these conditions. The main focus will be on the role
 of top-down brain processes in the experience of abdominal pain.
It remains unclear why a large proportion of people with inflammatory bowel disease (IBD)
 report ongoing abdominal pain during remission or why people with irritable bowel syndrome
 (IBS) develop abdominal pain. One theory is that people with chronic pain have somehow grown
 more sensitive.

 It is assumed that such heightened sensitivity depends both on bottom-up processing and
 top-down processing. Bottom-up processing refers to information that is relayed to the brain
 along so-called afferent fibres. Top-down processing refers to feedback provided by the brain
 to lower areas along efferent fibres.

 The investigators will (1) measure the capacity of people to inhibit pain through top-down
 processing, (2) test if the human pain experience is enhanced due to sustained activation of
 certain afferents, and (3) assess to what extent people are impacted by psychosocial
 inhibition and activation factors. Results of people with IBS in remission will be compared
 with the results of two groups of people with IBD (those with pain and those without) and the
 investigators will explore if their measurements differentiate between groups.

 It is hypothesized that (1) IBS patients and IBD patients with abdominal pain will be less
 able to inhibit their pain compared to IBD patients without abdominal pain (2) IBS patients
 and IBD patients with abdominal pain will score higher on psychosocial inhibition factors and
 lower on psychosocial activation factors when compared to IBD patients without abdominal
 pain. (3) In the total cohort, laboratory measures of pain inhibition will correlate with
 self-reported psychosocial inhibition and activation factors. (4) IBS patients and IBD
 patients with abdominal pain will show more temporal summation compared to IBD patients
 without abdominal pain.
General inclusion criteria:

 -  Aged 18 and over

 -  Sufficient command of written and spoken English

 IBD in remission inclusion criteria:

 -  Proof of diagnosis of IBD (Crohn's disease or ulcerative colitis) for more than 6
 months - - Clear indicators of remission: on faecal calprotectin (≤200 µg/g) or
 measurements of C-reactive protein (CRP; ≤10 mg/dl) within the last 3 months or as
 part of recruitment

 -  No previous episodes of acute or sub-acute obstruction

 IBS inclusion criteria:

 -  Current diagnosis of IBS measured with Rome IV criteria

 -  No serious other bowel diseases

 Exclusion criteria:

 -  Major abdominal surgery in the last 6 months, or 3 or more previous major abdominal
 surgeries

 -  Pregnancy or childbirth in the last 6 months

 -  Any other diagnosed medical condition that may explain abdominal pain, including but
 not limited to known gynaecological conditions such as endometriosis and known
 post-surgical adhesions

 -  Any diagnosed co-morbid medical conditions associated with known neuropathy, such as
 diabetic neuropathy, renal neuropathy, multiple sclerosis

 -  Use of opioids in the last week

 -  Use of anti-depressants used as pain medication in the last month