Incisional hernia swine: Case report

The occurrence of incisional hernias in pigs is poorly described, so the objective of the study is to report a case of incisional hernia in pig treated with polypropylene mesh. A 1 year old male, mixed breed pig weighing 22 kg was treated at the HVU-UFOB. During the anamnesis, the owner reported that the animal had swelling in the abdominal region, having a suggestive diagnosis of umbilical hernia, confirmed by ultrasound. In view of the findings, it was decided to perform herniorrhaphy with direct suture. Ten days after surgery, adequate healing of the surgical wound was verified with the absence of a hernial ring. Fifty-one after surgery, the animal returned with an increase in abdominal volume at the surgery site. On physical examination, the presence of a 12 cm ring and reducible intestinal loops in the hernial sac were identified. After a new ultrasound examination, the diagnosis of incisional hernia was defined. A new herniorrhaphy with polypropylene mesh was chosen. After 10 days, the wound healing was verified. Incisional hernias in pigs are generally related to the animal's age, sex, breed and species, as well as flaws in the surgical technique. Biological or synthetic materials are used for the correction, in order to reinforce safety in the incision line. One year after herniorrhaphy, there was no recurrence, which shows a satisfactory result with the use of the polypropylene mesh.


Introduction
Hernias can be congenital or acquired and consist of defects in anatomical structures that allow abnormal tissue or organ protrusion. Abdominal hernias are characterized by the opening of the musculature of the abdominal wall, classified as ventral or inguinal depending on its location, and reducible or irreducible according to the possibility of returning its content to the original cavity (Nunes, et al., 2019).
Incisional hernias are characterized by defects in the abdominal wall in areas of previous surgical incisions (Markovic, et al., 2016). Incisional hernia is the most common complication of laparoscopic surgeries in humans and some factors such as advanced age, use of corticosteroids, previous surgeries and surgical wound infections are related to the increase in their incidence (Nho, et al., 2012). The risk factors involved in the onset of incisional hernia can be divided into related to patient such as collagen deficiency, factors of the surgical technique such as the incision site, and postoperative factors such as surgical site infection, which is the most related (Sanders & Kingsnorth, 2012).
In pigs' umbilical hernias are frequent defects, can occur due to infections, changes in the development of the region's musculature, and may be related to genetic inheritance or incorrect management of the umbilical cord, with complication of intestinal incarceration Barcellos, et al., 2017). In rarer cases it can be caused due to persistent uracus (Borrás, 1983) since the junction of the umbilical vein, two arteries, yolk sac and uracus form the umbilical cord of the swines (Souza, et al., 2012).
The repair of abdominal hernias is performed through direct suture of the tissue edges or by the application of synthetic or biological surgical meshes. In humans, when compared to the repair performed only with direct suture, which is indicated in cases of defects up to three centimeters, the use of meshes considerably reduces recurrence (Sanders & Kingsnorth, 2012). In humans, the use of meshes is associated with higher rates of infection, chronic pain, and adherence (Rastegarpour, et al., 2016), which presupposes that there is no standard technique for correcting incisional hernias, and patients should be evaluated individually (Claus, et al., 2019). The occurrence of incisional hernias in pigs is poorly described, probably due to the lack of routine in performing abdominal surgeries in this type of production.
The aim of the study is to report a case of incisional hernia in swine treated at the Veterinary Hospital of the Federal University of Western Bahia (HVU-UFOB).

Methodology
The present study was carried out using a qualitative methodology (Pereira, et al., 2018), describing in detail a case of incisional hernia in a pig treated with polypropylene mesh. For this, clinical, anesthetic, and surgical data from the swine patient were used, showing the evolution of the case and the treatment employed, and looking for correlations for the development of the incisional hernia.

Case Report
A swine was treated at the HVU-UFOB, male, without breed defined, 1 year old, weighing 22 kg. During the anamnesis, the owner reported that the animal was swelling in the abdominal region ( Figure 1). The physiological parameters were within the normal range for the species. In the specific examination, there was an increase in volume in the abdomen region and during palpation; it was possible to identify structures such as the ring (about 30 cm), sac and hernial content. It was identified as reducible content, intestinal loops, and sensitivity to palpation was noted. Additionally, it was identified in the subcutaneous tissue, in the vicinity of the hernial ring, a spherical mass with about 6 cm in diameter of firm consistency in the region of the umbilical scar. The suggestive diagnosis was umbilical hernia, confirmed by ultrasound examination, which confirmed the presence of the mass heterogeneous being predominantly hypoechogenic with multiple Research, Society and Development, v. 10, n. 3, e55310313727, 2021 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v10i3.13727 4 hyperogenic points dispersed in the structure, but did not contribute to its diagnosis. In view of the findings, it was decided to perform classical herniorrhaphy and explore the site of insertion of the mass (Figure 2). This was followed by celiotomy with a section of the skin and divulsion of the subcutaneous tissue where it was possible to identify the hernia ring measuring 31 cm, the hernia sac, and its contents, in addition to the presence of an abscess of 6.2 cm in diameter. A routine procedure was performed, initiated by opening the hernia sac, section of excess portion, debridement of the edges and synthesis with nylon 1 (Procare®) with Mayo´s double-breasted suture pattern. This was followed by careful dissection of the abscess, which eventually ruptured, but its content was restricted to the field compresses that surrounded it. A fistulous path identified between the abscess and the umbilical scar was also removed. The surgical area was copiously washed with 0.9% saline solution, followed by the reduction of dead space with nylon 2.0 with intradermal pattern and dermorraphy with nylon 1 with Wolf pattern.
Ten days after surgery, adequate healing of the surgical wound was verified, and the stitches were removed. There was an absence of a hernial ring, pain, or discomfort; however, there was intense fibrosis in the muscles. It was observed that the animal had slight muscular atrophy and was unable to support the right posterior limb, being reported by the owner that this fact occurred after the last application of the antibiotic intramuscularly. In the case of a possible injury to the sciatic nerve, hydrocortisone (Gliocort®, 50mg/kg, i.m, SID, for 2 days) was given daily once for two days, intramuscularly, and later was informed by the owner that the animal returned to stand on its member on the same day as the first injection. Research, Society and Development, v. 10, n. 3, e55310313727, 2021 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v10i3.13727 5 Fifty-one days after surgery, the animal returned with an increase in abdominal size at the surgical site. The patient had no clinical changes and weighed 37 kg. On physical examination, the presence of a 12 cm ring was identified, intestinal loops were reducible in the hernial sac, and there was no pain or discomfort. After a new ultrasound examination, the diagnosis of incisional hernia was defined.
We decided for a new herniorrhaphy using a polypropylene mesh to reinforce the muscle wall. The same anesthetic protocol as the previous procedure was performed. During dissection of the hernial ring, intense adherence of the omentum to the hernial sac was identified, which was carefully dissected. After tissue debridement, the musculature was approached with nylon 1 in an "X" pattern, and the polypropylene mesh was subsequently applied, which was fixed using a simple stitch interrupted with nylon 0. The subcutaneous tissue was approached with an intradermal pattern and dermorraphy with Wolf pattern, both with 2.0 nylon thread.
After 10 days, adequate healing of the surgical wound was verified and the stitches were removed, with the absence of a hernial ring, pain, or discomfort (Figure 3). The animal remained in the farm until reaching ideal weight for slaughter, hernia recurrence was not identified.

Discussion
In the literature, the occurrence of incisional hernias in pigs is little reported, probably due to the lack of routine in performing abdominal surgeries in this species. In general, in large animals, an incidence of more than 16% is noted, while in dogs and cats the prevalence is lower, reaching around 6.5%, not being routine in these species. In humans, the incidence of incisional hernias is 4 to 10%, being a common complication of laparoscopic surgeries (Dietz, et al., 2018).
The increase in abdominal volume caused by hernia must be differentiated from abscesses, soft tissue tumors, lymphadenomegaly, hydrocele and osteitis (Simons et al., 2009, Claus et al., 2019 and the diagnosis of incisional hernia can be obtained through association of information about previous surgical procedure together with clinical examination where the composition of a true hernia is identified (Faria, et al., 2016). However, the use of ultrasound examination is justified to confirm and define the surgical approach to be performed (Claus, et al., 2019).
Because of the diagnosis and aiming at a lower cost in the procedure, it was decided to perform classical herniorrhaphy, using a suture pattern to overlap the abdominal muscle walls. Hernia correction can be performed through direct approximation of tissue borders (Read & Bellenger, 2002); however, other authors suggest that direct suturing in humans should be performed only in cases where the hernias are less than three centimeters in order to prevent recurrences (Sanders & Kingsnorth, 2012).
The existence of a restricted abscess with a fistulous path towards the hernia observed at the time of the first surgical procedure suggests a primary inflammatory reaction to the hernia. In piglets, it is common to have fights or aggressive reactions due to issues of inadequate handling or stress. The hernia extension in the reported pig may have been due to management failures, such as umbilical bite, development of an inflammatory reaction at the site and infection, which prevented the proper apposition of the muscle borders in their early life.
Fifty-one days after classical herniorrhaphy, the animal was diagnosed with incisional hernia. The occurrence of incisional hernia is generally related to the age of the animal, sex, breed and species (Faria, et al., 2016), as well as flaws in the surgical technique, mainly related to suturing, concomitant diseases that cause increased intra-abdominal pressure and the animal's behavior, especially when there are too many physical efforts that cause an increase in intra-abdominal pressure on the incision line and favors the rupture of the suture (Schulz, et al., 2003). The recurrence in swine may have been due to the association of some factors such as the rupture of the abscess that contaminated the surgical site (Millikan, 2003), the use of corticosteroids in the postoperative period, which reduces the inflammatory process and consequently delays tissue healing (Rosen, et al., 2008;Gupta, et al., 1999) in addition to the animal's weight gain and quadrupedal position, which increases the tension in the incision line (Schulz, et al., 2003). In addition, the suture pattern used, even being indicated for the correction of hernias in domestic animals, may not have prevented recurrences due to the large extension of the initial hernia ring of 31 centimeters.
The identification of adhesions of the omentum to the muscle wall during the correction of the incisional hernia in the second surgical procedure reinforces the hypothesis of infection at the surgical site (Biondo-Simões, et al., 2018) since this organ protects the abdominal structures against the spread of infection, promoting adherence, vascularization with consequent contribution of defense cells (Nicola, 2019).
For the correction of incisional hernias, biological or synthetic materials are used to reinforce safety in the incision line. Such materials were necessary to correct the hernia of the pig since the direct closure was not effective. Canine diaphragmatic phrenic center has been reported in order to achieve these reconstructive objectives (Azevedo, et al., 2018).
However, in the face of contamination (fistula/adherence), the use of synthetic material is even more justified. The polypropylene mesh is a synthetic material that has ideal characteristics, such as being inert and presenting macropores that facilitate the proliferation of fibroblasts allowing excellent surgical adhesion (Gonzalez, et al., 2004), lower rates of complications and less painful reaction in the post-operative (Gentile, et al. 2016). Its use in the repair of incisional hernia in a cow proved to be effective in reducing tension in the incision line and reducing the recurrence rate (Raghunath, et al., 2017).
No recurrence was observed after one year of herniorrhaphy, which shows a satisfactory result in the use of polypropylene mesh.

Final Considerations
Incisional hernia in swine is a relevant topic, but it is rarely reported in the literature. In this case, satisfactory result was observed using the polypropylene mesh compared to the direct hernia closure, demonstrating fewer complications and no recurrence. It is important to emphasize the necessity of the veterinarian to have knowledge of surgical techniques using synthetic material in the treatment of hernias and the types of synthetic materials used. Finally, in future studies, it is suggested that the etiopathogenesis of incisional hernias be more exploited in the swine species, as well as the influence of surgical technique, the choice of biological or synthetic materials for suture and postoperative pharmacotherapy in decreasing or increasing the incidence of incisional hernia appearance.