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INTEGRATION HISTOLOGY OF POLYPROPYLENE MESH IN PERINEAL HERNIA IN DOGS – A CASE STUDY L. Oana, C. Ober, C. Peştean, M. Taulescu, V. Miclăuş, C. Cătoi, A. Oros, Daniela Oros
UNIVERSITY OF AGRICULTURAL SCIENCES AND VETERINARY MEDICINE CLUJNAPOCA, ROMANIA, FACULTY OF VETERINARY MEDICINE
Summary In an eight year Doberman dog diagnosed with perineal hernia at physical examination, polypropylene mesh was used to close the rupture of the pelvic diaphragm. The mesh was sutured and anchored to sacrotuberous ligament, coccygeus muscle, levator ani muscle and finally to anal sphincter. Objectives of this study were to evaluate the tissue integration of the prosthetic polypropylene mesh after a long period postoperative. After three years postoperative, polypropylene mesh implanted in perineal area, produced a marked proliferation of connective tissue, collagen fibers, fibrocytes and blood vessels in the implanted area. We conclude that, clinically, polypropylene mesh gives a strong surgical repair of pelvic diaphragm in dogs long time postoperative, by an increasingly organised fibrotic scar, preventing the frequent recurrences appeared after o simple raphya of the hernial ring. Key words: collagen fiber, connective tissue, dog, polypropylene mesh, perineal hernia
diaphragm muscles, possibly of neurologic origin, has been identified in some animals with hernias (Fossum et al., 2007). Herniorrhaphy should always be recommended and the two most commonly used techniques are (1) the traditional, or anatomic reapposition; and (2) the internal obturator roll-up, or transposition technique (Fossum et al., 2007). When internal obturator muscle flap is weak, the technique with polypropylene mesh can be used like the operation of the first choice (Vnuk et al. 2006). The purpose of this study was to evaluate macroscopic appearance and tissue integration of the polypropylene mesh implanted in perineal hernia in a dog, after 2 years postoperative.
Introduction Implantation of prosthetic materials in hernia surgery has become popular worldwide. Polypropylene meshes, first proposed by Usher et al. (1960) in the early 1960s, are the preferred material for prosthetic repair today (DeBord, 1998). However, polypropylene meshes can induce adhesions or even fistula in contact with abdominal or pelvic viscera, or they can become extremely rigid, generating disconfort or pain (Bauer et al., 1999; Besim et al., 2002; Klinge et al., 2002). Perineal hernias occur when the perineal muscles separate, allowing rectal, pelvic, and/or abdominal contents to displace perineal skin (Fossum et al., 2007). The pelvic diaphragm muscles fail to support the rectal wall, allowing persistent rectal distention and impaired defecation. The cause of pelvic diaphragm weakening is poorly understood, but is believed to be associated with male hormones, straining, and congenital or acquired muscle weakness or atrophy. Atrophy of the pelvic
Matherial and methods Case details A 8-year old Doberman male dog was referred to the Department of Anesthesiology and Surgical Propedeutics 174
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After three years, the dog was euthanized because of o chronic pancreatitis with persistent anorexia reluctant to medical management.
because of a large swelling in perineal region. Clinical findings On arrival the dog was alert, without any other problems during routine clinical examination. A large painless swelling was observed in left perineal area. The dog showed periodic difficulty defecating because of a large rectal diverticulum with impacted feces, with no other signs of abdominal pain. The hernia was a recurrence of an anterior perineal hernia resolved by a simple suture of pelvic ring. With the owner’s consent, the technique with polypropylene mesh (D-tek, Polypropylene mesh, Limassol, Cyprus) was decided to be performed.
Fig. 1. Prosthetic mesh fixation
Surgical technique The large intestine was evacuated preoperative with laxatives (Metamucil) and manual extraction. Premedication before surgery was atropine (0.03 mg/kg SC) plus butorphanol (0.3 mg/kg SC). Propofol (5 mg/kg) was administered IV to effect for induction of anesthesia. Endotracheal intubation was done and isoflurane maintained anaesthesia. A curvilinear incision beginning cranial to the coccygeus muscles, curving over the hernial bulge, lateral to the anus, was made. After subcutaneous tissue debridements, the hernial sac was reduced and the muscles involved in the hernia were identified. The mesh was sutured with interupted suture, ventrally to adipous tissue, laterally to sacrotuberous ligament, coccygeus muscle and levator ani muscle and finally to anal sphincter (Fig 1). Five layers of Cushing suture type were placed to rectal diverticulum. The mesh was covered by subcutaneous tissue using absorbable suture material. The skin was sutured with surgical silk. Orchiectomy was done in the prescrotal area. No complications appeared in postoperative interval.
Histopathological examination Complete anterior abdominal wall was removed for macroscopic and histopathological evaluations. Tumours samples were fixed in buffered formaline 10%, for 24 hours, latter they were wax embaded, and section at 4-5 micrometers thick were processed by using Leica RM 2125 RT microtome. Classical staining like Hematoxilin – Eosin and Tricrom – Mason were the choice. The slides have been evaluated with Olympus BX 51 microscope, the images were captured with Olympus SP 350 photo camera, and processed by using Olympus DP soft.
Results and discussions Histopatological findings At microscopic examination of tissue mass developed in the surgery area, a marked proliferation of good nature fibrous connective tissue was observed. This tissue contains thick collagen bundles oriented parallel and disposed in fascicles which penetrate through prosthetic mesh microfilaments (Fig. 2, 3 and 4) forming with them a strong common structure without areas of tissue laxity. Also, vessels of neoformation in connective tissue mass are observed (Fig. 3). Discrete 175
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inflammatory infiltrate is characterized by a mononuclear proliferation having a nodular aspect. Phenomena of cell necrosis and inflammatory infiltration with polymorphonuclear neutrophils were not observed. Focal of inflammatory cells were not present around the microfilaments, but its were observed at the edge of tissue mass, phenomenon due to an chronic perianal adenitis. Filamentous structure of the prosthetic mesh did not suffered visible microscopic structural damages. Fig. 4. Proliferation of collagen fibers, fibrocytes and blood vessels through microfilaments of prosthetic mesh (white arrow). Rare lymphocytes and hystiocytes dispersed in connective mass TM x 40 (black arrow); (TM x 40).
Fig. 2. Proliferation of connective tissue through and arround microfilaments of prosthetic mesh (white arrow). Nodular focal with mononuclear inflammatory cells (black arrow); (TM x 10).
Fig. 5. Chronic inflammatory infiltrate with mononuclear cells having nodular aspect (white arrow). Connective-vascular proliferation (black arrow) (TM x 20).
The excellent results reported in the literature for the use of prosthetic meshes have made them the method of choice for the repair of abdominal wall defects. These prostheses may currently represent the largest group of alloplastic materials used in medicine (Greca et al., 2008). Long-term investigations of tissue integration of polypropylene mesh is very important, because this kind of material,
Fig. 3. Proliferation of connective tissue through microfilaments of prosthetic mesh (white arrow). Vessels of neoformation (black arrow). (TM x 20).
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widely used, can induce chronic groin pain, adhesions, fistulas or chronic infections (García-Ureña et al., 2007), both in humans and animals. In this study we observed that, polypropylene mesh implanted in perineal area, produced a strong connective tissue proliferation and fibrosis, without any sign of disconfort or recurrence on the part of the dog. The new formed connective fibrous tissue represented a very resistant support for the area of broken pelvic diaphragm. In previous studies, we observed the same phenomena after long term implantation of polypropylene meshes in abdominal region in rabbits, but the connective tissue did not present such density (Ober et al., 2009). Our observations confirm that, the closing of hernial defects with meshes results in a lower recurrence rate (Luijendijk et al., 2000; Morris-Stiff et al., 1998), given that the dog in the study, had a recurrence after the first closure of the hernial ring by a simple raphya.
Conclusions Perineal hernia in dogs can be easy managed using a prosthetic biomaterial such as polypropylene mesh. Polypropylene mesh implanted in perineal area, produces a proliferation of connective tissue, collagen fibers, fibrocytes and blood vessels through, and arround microfilaments of prosthetic mesh. The neoformation connective fibrous tissue represents a very resistant support for the area of broken pelvic diaphragm, preventing the frustrated recurrences.
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