title: Distensibility of the mouse rectum: application of impedance planimetry for studying age-related changes.
abstract: Rectal distensibility is an important parameter for investigation of anorectal function. The aim of the present paper was to study pressure-cross-sectional area (CSA) relations and distensibility of the rectum in mice aged 15-78 weeks using impedance planimetry. A four-electrode probe system located inside a balloon was designed to determine pressure-CSA relations in the mouse rectum. CSA was estimated from measurements of the electrical impedance of saline inside a balloon. The method was validated in studies in vitro showing high accuracy and good reproducibility. The method was applied in measurements of inter- and intra-individual variation and age-related variation of rectal pressure-CSA relations and distensibility. Repeated distension every third day in a cohort of 10 mice did not change the CSA during a 4-week period and there was no long-term effect of repeated measurements. There was an age-related increase in rectal CSA in the distended state until the mice were 26 weeks of age (P = 0.004). The unloaded size of the rectum did not change with age. The distensibility of the rectum did not vary significantly with age, though there was a tendency to a higher distensibility during growth followed by decline with age (P = 0.08). In conclusion, this study presents a simple, minimally invasive in vivo model for repeated evaluation of rectal distensibility in mice. The mouse model will provide a tool for analysing relative changes in rectal biomechanical properties in different future disease models.
authors.affiliation: Surgical Research Unit, Department of Surgery, Aarhus University Hospital, Aarhus, Denmark, Institute of Experimental Clinical Oncology, Institute of Experimental Clinical Research, Aarhus University Hospital, Aarhus, Denmark, Biomechanics Laboratory, Institute of Experimental Clinical Research, Aarhus University Hospital, Aarhus, Denmark.
authors.lastname: Lundby
authors.lastname: Dall
authors.lastname: Gregersen
authors.lastname: Overgaard
authors.lastname: Laurberg