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.
Bibliography :