Background & aims: Abuse history is common in irritable bowel syndrome (IBS) and is associated with greater pain reporting, psychologic distress, and poorer health outcome. These effects may be mediated by enhanced responses to aversive visceral stimuli. We investigated the effects of IBS and abuse history on pain reporting and brain activation in response to rectal distentions.
Methods: Ten female patients with IBS and 10 controls were included. Half of patients in each group reported a history of abuse. Brain functional magnetic resonance imaging (fMRI) images and pain ratings were obtained during rectal distentions. Statistical parametric mapping identified activation in subregions of the dorsal cingulate cortex and covariation with rated pain.
Results: (1) Distention-elicited pain correlated with anxiety and activation of the posterior (PCC) and middle (MCC) dorsal cingulate subregions. (2) Subjects with a history of abuse showed greater activation in the left MCC (P = .022; t = 5.61) and PCC (P = .033; t = 5.00) than subjects without abuse. (3) Those with IBS and abuse reported greater pain than all others (P = .004), had more activity in the left MCC (P = .021; t = 5.29) and PCC (P = .049; t = 4.81), and had less activity in the left supragenual anterior cingulate (sACC) (P = .01; t = 4.86).
Conclusions: Pain ratings during rectal distention are associated with activation of dorsal cingulate regions implicated in homeostatic afferent processing, and prior abuse enhances this activation. Patients with IBS and abuse report more pain, greater MCC/PCC activation, and reduced activity of a region implicated in pain inhibition and arousal (sACC). These findings suggest a possible explanation for the clinical observation of greater pain reporting and poorer outcome in IBS patients with a history of abuse.