Experimental model for study of anorectal sphincter musculature by manometry and computerized tomography in piglets

There seems to be controversy on the anorectal sphincter presentation and anatomical division, as well as on its functional representation. Evaluation of the anorectal sphincter musculature has been achieved through several methods, including anorectal manometry and computerized tomography, but to date there is no experimental model allowing a detailed manometric study of this muscle complex. In this work, we have developed such a model, which should enable the manometric and radiographic study of the anatomical features and functional mechanisms of sphincteric injuries, as well as the assessment of drug effects on the anorectal musculature upon incontinence and constipation. Twenty-two piglets (aged 25–30 days, weighing 5–7 kg) were studied by anorectal manometry (rectoanal inhibitory reflex and vector volume) and computerized tomography (anorectal angle and anal canal length). The data obtained for the rectoanal inhibitory reflex, represented here as the average and standard deviation, were the following: relaxation duration = 14.75 ± 3.62 s, sphincter basal pressure = 41.58 ± 8.20 mmHg, relaxation index = 87.26 ± 11.52%, speed of relaxation = 5.90 ± 2.10 mm/s, and speed of relaxation recovery = 4.03 ± 1.78 mm/s. As for the vector volume, results were as follows: vector volume = 2692.32 ± 1298.12 mmHg² cm, sphincter length = 11.82 ± 2.74 mm, high pressure zone length = 5.09 ± 1.34 mm, maximum pressure = 61.50 ± 20.58 mmHg, and asymmetry index = 43.50 ± 10.03%. Radiographic evaluation led to the following results: anal canal length = 9.61 ± 2.14 mm and anorectal angle = 137.91 ± 7.75°. The experimental model designed here allows both anorectal manometry and computerized tomography to be carried out in the same way it is performed in human beings, as long as animal sedation is strictly controlled.