Application of Bifurcated Semitendinosus Muscle Transposition for Treatment of Fecal Incontinence in Two Dogs

Simple Summary Fecal incontinence is a condition characterized by an inability to control defecation, due to either a failure of the large intestine to contain colorectal contents or a failure of the anal sphincter to resist the rectal propulsive forces. Surgical intervention is often necessary to treat severe cases. This study presents a modified semitendinosus muscle flap technique for anal sphincter augmentation in two canine patients with fecal incontinence: a 4-year-old mixed breed dog and a 19-year-old English Cocker Spaniel. The semitendinosus muscle was bifurcated and transposed around the anus. The resulting two muscle bundles completely encircled the anorectum, leading to a complete reconstruction of the external anal sphincter. Both dogs regained fecal continence following surgery. This new technique requires a shorter length of harvested muscle flap and is a relatively simple surgical procedure compared to conventional surgeries. So, it may be a viable surgical option for anal sphincter incontinence in dogs. A 4-year-old mixed breed dog and a 19-year-old English cocker spaniel dog were evaluated for fecal incontinence. The second dog's fecal incontinence was associated with the anal mass. In both dogs, reconstruction of the external anal sphincter was required to gain fecal continence. Especially in the dog with an anal mass, the whole musculature involved in fecal continence was removed with the affected anorectum. Conventional surgical treatments for fecal incontinence have limitations in terms of muscle flap length and complexity of the surgical procedure. A modified surgical technique using the semitendinosus muscle was devised in the present study to overcome these limitations. The distal part of the semitendinosus muscle was bifurcated to make two muscle bundles, used to completely encircle the anorectum. These muscle bundles were sutured to the surrounding rectal muscle and the pelvic diaphragm to simulate the function of the external anal sphincter. Three months after surgery, both dogs showed significantly improved fecal continence without severe complications, such as infection, dehiscence, or lameness of the limb where the semitendinosus muscle was harvested. The outcomes of the two dogs supported the acceptability of the bifurcated muscle flap for anal sphincter augmentation. In addition, this report showed the possibility of more diverse applications of semitendinosus muscle in dogs.