Figure 6 (a, b, c, d, e, f, g, h, i, j)
In both surgeries, the cutaneous sutures were covered with Terramicyn spray postoperatively. After the first surgery, the mare was given 8000 IUs of antitetanic serum subcutaneously. Antibiotic therapy was provided with an intravenous injection of sulphate gentamicin (6.6 mg/kg bwt) and penicillin-streptomycin (at a dose of 9.000 IU benzylpenicillin and 11,3 mg of dihydrostreptomycin/kg) injected intramuscularly once a day for five successive days. Flunixin meglumine was given at a dose of 1.1 mg/kg bwt on the day of the surgery, and phenylbutazone in an oral formulation at a dosage of 4.4 mg/kg bwt was administered for three successive days. The wound was dressed three times a day with gentamicin cream. In addition, the mare was given a mash diet to soften the faecal mass which was continued by the owner for 40 days. The quantity of hay was reduced and was then gradually reintroduced. A week after the surgery, the patient was discharged. The case was followed up for 8 months, and no recurrences or complications were observed.
Discussion: Perineal hernia is a pathology requiring surgery which occurs as a rsult of weakness of the components of the pelvic diaphragm . For the most part, it develops in old uncastrated male dogs, even if the cause of the condition still remains unclear. Females have a lesser incidence related to the greater strength, size and area of the rectal attachment of the levator ani muscle. These differences are associated with the load placed on the pelvic diaphragm muscles during parturition. In contrast, in large animals, cases of a perineal hernia had only been recorded in female patients . The anatomical and pressure differences which could lead to perineal weakness could be the causes of a perineal hernia in horses, buffalo and cows . The characteristic clinical signs reported, such as tenesmus, straining in urination, and constipation refer to dogs. In the present case, only chronic weight loss and high recurrence bulging were present. A 6-cm-long defect opening on the left side and a 4-cm-long opening on the right side were identified by palpation of the swelling between the levator ani and the coccygeus, and the internal obturator and the external anal sphincter muscles. In fact, in dogs, the levator ani is thought to be the most common muscle atrophied during this condition and, in many cases, it is in fact absen . Therefore, the diagnosis was reached by means of clinical presentation, perineal palpation and ultrasound examination. In this mare, the ultrasound examination revealed hyperechogenic muscle fibres and hyperechogenic foci within the pelvic diaphragm muscles. In addition, on the left side, a hyperechogenic structure was identified, probably corresponding to a bowel loop segment with hypoechoic content. For this reason, ultrasonography of a suspected perineal hernia in equids is highly recommended recommended prior to surgery. The disorder requires surgical treatment to prevent complications, such as reversible displacement or, even if less likely, permanent bowel incarceration . In fact, even if the hernia content was reducible, the main concern regarding the patient was bowel segment entrapment and eventual strangulation.
In the present case, the first surgical approach was standing appositional herniorrhaphy. Moreover, the standing surgery allowed maintaining the anatomical symmetry. For the second surgery, semimembranosus muscle transposition, which represented an original approach, was opted for. In the literature regarding small animal surgery, the most commonly used muscle transposition technique is that which involves the internal obturator muscle . In this mare, this method could not beutilised due to the severe atrophy of the muscle belly. Other procedures included gluteal and semitendinosus muscle transpositions which, in the present case, could not be carried out owing to the size and the different muscle anatomical disposition of the perineal area. In addition to muscle transposition techniques, the use of implants, such as polypropylene mesh and acellular dermal matrix, to cover the pelvic diaphragmatic defect is frequent in small animals. This approach has a low recurrence rate and is technically easy . In addition, the use of mesh implants is very useful when there is weakness of internal obturator muscle flap, especially in bilateral cases . In particular, polypropylene mesh is considered to be one of the best materials for hernia repair; it promotes host tissue healing with the same strength as that of normal tissue, provides resistance to infection, elicits no enhanced inflammatory response, and inhibits adhesions or fistula formation (Al-Akraa, 2015). Moreover, in 1989, Clarke stated that the advantages of this method of repair included less tension, less deformity of the external anal sphincter and helped in the closure of the ventral aspect of the hernia . Frequent problems observed in dogs related to the use of mesh include wound infection, rectal prolapse and breakdown of the integrity of the implant . There is one reported case of a perineal hernia in a buffalo which illustrates the use of polypropylene mesh without associated complications . In horses, synthetic mesh is used in order to repair large abdominal incisional hernia defects. The major associated complications are drainage/infection, peritoneal adhesions and bowel abrasion . In the present case, using a mesh to close the perineal hernia was not taken into consideration. In fact, the most caudal thigh muscles of the mare were well developed, and, considering the number of complications associated with mesh implantation, including the possibility of prosthetic contamination, semimembranosus muscle transposition turned out to be the most suitable choice. In this patient, the Authors’ choice was to use muscular transposition, despite the bilateral condition. In the Authors’ opinion, the tension created by the double repair did not affect the effcacy of the herniorraphy, and the likelihood of possible contamination was less. However, additional cases are necessary to evaluate the effectiveness of using implants for a perineal hernia in horses. Some of the potential postoperative complications of a surgical hernia repair are wound dehiscence, rectal prolapse, urinary tract dysfunction, faecal incontinence or tenesmus, and recurrent herniation. The latter occurred accidentally after the first surgery; on the contrary, no complications were reported following the second surgery.
Conclusion : A case of perineal hernia in a mare is herein reported. Despite the rarity of this condition in equids, it should be considered as a possible differential diagnosis for perineal swellings. Clinical signs, swelling, and the results of palpation and ultrasound examination should be taken into consideration when considering a final diagnosis of perineal hernia. Considering that a perineal hernia requires surgical management, standing semimembranosus muscle transposition turned out to be the most effective technique for rsolving this case.
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