Introducing a noninvasive, non-surgical, and reversible animal model for fecal incontinence using abobotulinumtoxinA in dogs

Abstract

The aim of this study was to introduce a new animal model of fecal incontinence (FI) by injecting abobotulinumtoxinA in the external anal sphincter (EAS) muscle of dogs which replaces models based on anal sphincter destructions that are invasive, mostly require surgical procedures, expensive, permanent, and painful to the animals. 4 healthy mongrel dogs were used in this study. First, they were received NaCl 0.09% (as control) injections in EAS muscle and effects were assessed by means of Electromyography (EMG) and clinically evaluated by sphincter pinch test and presence of leakage of feces for 2 weeks. Then, they received abobotulinumtoxinA in EAS muscle and reevaluated for 6 weeks to see short-term and medium-term effects of abobotulinumtoxinA injection. Saline had no significant changes in results obtained from EMG, however, there were significant decreases in amplitudes of action potentials after receiving abobotulinumtoxinA in comparison with no injection or saline injection in EAS muscle. Pinch tests were normal after saline injection assessment period, however, then started to be negative, ranging from two days after abobotulinumtoxinA injection to seven days after receiving abobotulinumtoxinA. Animals also had significant presentations of fecal incontinence (leakage of feces and cage contamination with feces) from the 1^st week after receiving abobotulinumtoxinA until the 6^th week after receiving abobotulinumtoxinA. AbobotulinumtoxinA caused paralysis in the EAS and producd FI conditions in dogs. This animal model was an appropriate substitute to the various invasive, expensive and also complicated procedures with an easy, feasible, noninvasive and non-painful single-stage abobotulinumtoxinA injection.

Keywords: AbobotulinumtoxinA; Dog; Electromyography; External anal sphincter; Fecal incontinence.

Fig. 1

Perineal view in the EMG test in dogs. A: The point of insertion of bipolar needle-EMG over the anatomical position of the pudendal nerve (hatched line). B: The point of insertion of “Ground electrode”. C: The position of placement of “Reference electrode” over the inactive region of the perineum, and D: The “Active electrode” positioned over the belly of external anal sphincter muscle

Fig. 2

Perineal view of dogs during injections of saline and abo-botulinumtoxinA. A: The insertion point of Ambu^© Neuroline Inject EMG needle as the cathode electrode over the belly of external anal sphincter. B: The point of insertion of anode electrode in midline, and C: The point of insertion of ground electrode

Fig. 3

schematic change in voltage of amplitudes of EMG tests before treatment and time points after treatment with saline and abobotulinumtoxinA (Bot.).