Regions of the brain activated in bladder filling vs rectal distention in healthy adults: A meta‐analysis of neuroimaging studies

Abstract

Aims: Adults with pelvic floor disorders commonly present with overlapping bladder and bowel symptoms; however, the relationship between urinary and defecatory dysfunction is not well understood. Our aim was to compare and determine if overlapping brain regions are activated during bladder filling and rectal distention in healthy adults. Methods: We conducted separate Pubmed searches for neuroimaging studies investigating the effects of rectal distention and bladder filling on brain activation in healthy subjects. Coordinates of activated regions were extracted with cluster-level threshold P < .05 and compared using the activation likelihood estimate approach. Results from the various studies were pooled and a contrast analysis was performed to identify any common areas of activation between bladder filling and rectal distension. Results:We identified 96 foci of activation from 14 neuroimaging studies on bladder filling and 182 foci from 17 studies on rectal distension in healthy adults. Regions activated during bladder filling included right insula, right and left thalamus, and right periaqueductal grey. Regions activated during rectal distention included right and left insula, right and left thalamus, left postcentral gyrus, and right inferior parietal lobule. Contrast analysis revealed common activation of the right insula with both rectal distention and bladder filling.Conclusion: Bladder filling and rectal distention activate several separate areas of the brain involved in sensory processing in healthy adults. The common activation of the insula, the region responsible for interoception, in these two conditions may offer an explanation for the coexistence of bladder and defecatory symptoms in pelvic floor disorders. K E Y W O R D S bladder filling, insula, interoception, neuroimaging, pelvic floor disorders, rectal distention

OAB supraspinal control network, transition with age, and effect of treatment: A systematic review

“…In healthy subjects, the right insula has an interoceptive function of mapping visceral signals, mainly nociceptive inputs, and making them accessible to consciousness 32 and its activation appears to be increasing with bladder filling 19 . Halani et al 8 have also demonstrated through contrast analysis that both rectal and bladder filling among healthy subjects results in activation of the insula, hypothesizing its implication as a supraspinal center in the overlap of bowel and bladder symptoms in pelvic floor disorders. Moreover, in the study of Ketai et al 25 involving 53 OAB and 20 healthy subjects, a statistically significant difference in activation is noted at the level of the insula in OAB patients compared to healthy controls.…”

“…The two most frequent techniques used are positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), and at a lesser extent, single‐photon emission computed tomography (SPECT) 6 . These techniques rely on a local hemodynamic response based on the principle of neurovascular coupling where activated neuronal bundles requiring more oxygen and nutrients induce an increased blood flow in a region of interest (ROI) 7 normally reported in stereoscopic x , y , and z displacement coordinates 8 . Advancement in fMRI has also led to the development of newer techniques such as resting‐state functional connectivity MRI (rs‐fcMRI) requiring no specific task from the patient; on the contrary, exploring intrinsic neuronal functional connectivity at a resting state 9 .…”

“…6 These techniques rely on a local hemodynamic response based on the principle of neurovascular coupling where activated neuronal bundles requiring more oxygen and nutrients induce an increased blood flow in a region of interest (ROI) 7 normally reported in stereoscopic x, y, and z displacement coordinates. 8 Advancement in fMRI has also led to the development of newer techniques such as resting-state functional connectivity MRI (rs-fcMRI) requiring no specific task from the patient; on the contrary, exploring intrinsic neuronal functional connectivity at a resting state. 9 Among healthy individuals, identified ROIs involved in bladder control include the periaqueductal gray (PAG), thalamus, insula, dorsal anterior cingulate, ventromedial cerebellum, orbitofrontal cortex, pons, and the hypothalamus.…”

High Frequency of Concomitant Bladder, Bowel, and Sexual Symptoms in Huntington’s Disease: A Self-Reported Questionnaire Study

“…Functional imaging studies have shown neural control of bladder, bowel, and sexual function to be complex, involving many regions of the brain [ 22 , 23 , 24 , 25 , 26 , 27 , 28 ]. HD is characterized by progressive neuronal loss in the basal ganglia, and atrophy has also been reported for frontal, temporal, insular, and parietal cortical areas in HD [ 29 , 30 ].…”

Past, Present, and Future in the Study of Neural Control of the Lower Urinary Tract

“…Most recent studies focus on functional magnetic resonance images (fMRI) limited to only a handful of subjects [50,51]. While the sensation of bladder distention and urgency has been associated strongly with the thalamus in rats, human studies show involvement of a plethora of other structures [52][53][54][55].…”