Although sensory testing is a regular part of anorectal manometry (ARM), there is debate regarding its therapeutic use. Patients with irritable bowel syndrome (IBS) have long been believed to be more susceptible to rectal balloon inflation. Using various technologies, researchers investigated whether rectal hypersensitivity was a sign of IBS in a sizable population.

Between July 2017 and April 2022, they examined data from individuals who underwent ARM for persistent constipation. Through the Patient Assessment of Constipation Symptoms (PAC-SYM), they gathered information on demographics, disease characteristics, including Rome IV IBS diagnosis and symptom severity, as well as psychological characteristics, such as anxiety/depression (Hospital Anxiety and Depression Scale; HADS) and GI-specific anxiety (Visceral Sensitivity Index; VSI). They compared the findings to ARM sensitivity data that was gathered using high-resolution (HR) and 3D ARM catheters. To homogenize disparities between HR and 3D ARM measures, volume values >75th percentile of the initial sensation, urge sensation, and maximum acceptable volume were designated hypersensitive. To investigate correlations with rectal hypersensitivity, they employed logistic regression.

They included a total of 456 patients (mean age 49.5+/-17.5 years, 90.0% female), the majority of whom fulfilled Rome IV criteria for functional constipation (FC)((n=405, 88.8%) vs n=51 (11.2%) with IBS-C)). Compared to patients with FC, individuals with IBS-C tended to exhibit higher levels of GI-specific anxiety and more severe constipation symptom severity (driven by the abdominal symptoms subscale). Between the groups, there were no differences in the proportion of hypersensitive patients to any threshold. IBS-C was not linked to rectal hypersensitivity at first sensation volume (OR=0.61, 95% CI 0.30-1.15, P=0.14), urge sensation volume (OR=0.75, 95% CI 0.38-1.43, P=0.40), or discomfort volume (OR=0.78, 95% CI 0.38-1.50, P=0.47), according to age-adjusted logistic regression.

They looked for evidence of increased rectal sensitivity to volumetric inflation in IBS patients compared to those with functional constipation in the large cohort of patients undergoing ARM for chronic constipation using two different types of ARM catheter technology, but we were unable to find any. The results suggested that the visceral hypersensitivity assumed to underlie the disease pathogenesis in IBS may not be reflected in rectal sensation.