Experimental models of longitudinal abdominal incisional hernia in rats

Modelos experimentais de hérnias incisionais abdominais longitudinais, em ratos

Abstracts

Abdominal incisional hernias in rats has been produced after resection of a segment of abdominal muscle. In a attempt to create a model of incisional hernia in rats, without resection of abdominal muscle, the following surgical procedures were performed: (a) Rats anesthetized with ether were submitted to a 4 cm long median incision, supra and infraumbilical, followed by dissection of the subcutaneous tissue 1.5 cm laterally to the median line in each side; after, one incision was performed in the linea alba and peritoneum, with the same extension of the skin incision; the skin incision was sutured. (b) Rats were submited to a suprapubic transversal incision and a scissors introduced through this incision and used to dissect the subcutaneous tissue at least 1.5 cm for each side of median line; after, the linea alba and peritoneoum were incised and the transversal skin incision sutured. (c) For control, rats were submitted to a resection of a 2.5 x 4 cm of the abdominal muscles, creating a large defect in the abdominal wall. All the animal, submitted to the three different procedures, developed similar well constituted hernias. We concluded that abdominal incisonal hernias are easily induced in rats after an incision of the abdominal wall, without partial resection of abdominal muscle, since the subcutaneous have been dissected at least 1.5 cm laterally to the median line.

Hernia; Incisional hernia; Eventration


Hérnias incisionais abdominais no rato têm sido produzidas pela ressecção de fragmento dos músculos de parede abdominal. Na tentativa de criar um modelo de hérnia incisional abdominal no rato, sem ressecção de fragmentos de músculo de parede abdominal, os seguintes procedimentos cirúrgicos foram realizados: (a) Ratos anestesiados com vapores de éter foram submetidos à uma incisão longitudinal mediana supra e infra umbilical, de 4 cm de comprimento, seguida do descolamento do tecido celular subcutaneo em uma extensão de 1,5 cm lateralmente à linha mediana; de cada lado; em seguida era feita uma incisão de linha alba e peritonio parietal com a mesma extensão de incisão cutânea; a incisão cutanea era suturada com pontos separados. (b) Ratos foram submetidos à uma incisão transversal, suprapúbica, através da qual se introduzia a tesoura e se descolava o tecido celular sub-cutâneo até 1,5 cm de cada lado da linha média em uma extensão de 4 a 5 cm em direção ao apêndice xifoide; em seguida era feita uma incisão na linha alba e peritônio parietal e suturada a incisão cutânea transversal. (c) Para controle, ratos foram submetidos à ressecção de um fragmento de 3 x 4 cm dos músculos da parede abdominal anterior, criando-se um grande defeito na parede abdominal. Todos os animais submetidos aos três procedimentos desenvolveram hérnias abdominais bem constituídas. Concluiu-se que hérnias abdominais incisionais podem ser facilmente induzidas no rato após incisão da parede abdominal, desde que o tecido subcutâneo seja deslocado lateralmente à incisão em extensão de pelo mínimo 1,5 cm.

Hérnia; Hérnia Incisional; Eventration


4 - ORIGINAL ARTICLE

EXPERIMENTAL MODELS OF LONGITUDINAL ABDOMINAL INCISIONAL HERNIA IN RATS.1 1 Laboratory of Experimental Surgery, Department of Surgery. Escola de Medicina da Santa Casa de Misericórdia de Vitória-EMESCAM-Vitória-Espírito Santo-Brazil 2 MD, PhD. 3 MD.

Danilo N. S. Paulo2 1 Laboratory of Experimental Surgery, Department of Surgery. Escola de Medicina da Santa Casa de Misericórdia de Vitória-EMESCAM-Vitória-Espírito Santo-Brazil 2 MD, PhD. 3 MD.

Fausto E. L. Pereira2 1 Laboratory of Experimental Surgery, Department of Surgery. Escola de Medicina da Santa Casa de Misericórdia de Vitória-EMESCAM-Vitória-Espírito Santo-Brazil 2 MD, PhD. 3 MD.

Ricardo F. da Mata3 1 Laboratory of Experimental Surgery, Department of Surgery. Escola de Medicina da Santa Casa de Misericórdia de Vitória-EMESCAM-Vitória-Espírito Santo-Brazil 2 MD, PhD. 3 MD.

Fabyano R. Dauad3 1 Laboratory of Experimental Surgery, Department of Surgery. Escola de Medicina da Santa Casa de Misericórdia de Vitória-EMESCAM-Vitória-Espírito Santo-Brazil 2 MD, PhD. 3 MD.

Isabel C. A. L. Paulo3 1 Laboratory of Experimental Surgery, Department of Surgery. Escola de Medicina da Santa Casa de Misericórdia de Vitória-EMESCAM-Vitória-Espírito Santo-Brazil 2 MD, PhD. 3 MD.

PAULO, D.N.S.; PEREIRA F.E.L.; MATA, R.F.; DAUAD, F.R.D.; PAULO, I.C.A.L. - Experimental models of longituninal abdominal incisional hernia in rats. Acta. Cír. Bras. 12(4): 231-4, 1997.

SUMMARY: Abdominal incisional hernias in rats has been produced after resection of a segment of abdominal muscle. In a attempt to create a model of incisional hernia in rats, without resection of abdominal muscle, the following surgical procedures were performed: (a) Rats anesthetized with ether were submitted to a 4 cm long median incision, supra and infraumbilical, followed by dissection of the subcutaneous tissue 1.5 cm laterally to the median line in each side; after, one incision was performed in the linea alba and peritoneum, with the same extension of the skin incision; the skin incision was sutured. (b) Rats were submited to a suprapubic transversal incision and a scissors introduced through this incision and used to dissect the subcutaneous tissue at least 1.5 cm for each side of median line; after, the linea alba and peritoneoum were incised and the transversal skin incision sutured. (c) For control, rats were submitted to a resection of a 2.5 x 4 cm of the abdominal muscles, creating a large defect in the abdominal wall. All the animal, submitted to the three different procedures, developed similar well constituted hernias. We concluded that abdominal incisonal hernias are easily induced in rats after an incision of the abdominal wall, without partial resection of abdominal muscle, since the subcutaneous have been dissected at least 1.5 cm laterally to the median line.

SUBJECT HEADINGS: Hernia. Incisional hernia. Eventration.

INTRODUCTION

Abdominal incisional hernia can induce changes in respiratory function, mainly in patients with great hernias that impair the respiratory mechanics9,11. The mechanisms of these changes are not clear and functional studies of diafragma and abdominal muscles in experimental models of incisional hernias would contribute to better understanding the problem. Experimental models of incisional hernias has been reported in rabbits, dogs and sheeps 1,3,5,8 . In rats, laboratory animals that are easily handled, there are few reports about experimental abdominal incisional hernias. REITH et al 10 e FRANKE et al 6 produced adominal hernias in rats sectioning a square fragment of the muscles of the abdominal wall . The hernias induced were repaired with prothesis. This model of abdominal hernias in rats has been used by several authors to study the repair with different kinds of prothesis, immediattely after the defect was produced 2,4,7,12. In fact those authors did not produce an hernia , but a defect simulating a hernial ring that was closed using a prothesis. This has been an usefull model for study the performance of different kinds of prothesis. However, an incisional hernia induced after ressection of a fragment of abdominal muscles is not similar to abdominal incisional hernias in man, in which there is a section of the abdominal wall, but not a ressection of fragments of this structure.

In this paper we describe models of experimental abdominal incisional hernias in rats without ressection of fragment of abdominal muscles.

METHOD

Male and female wistar rats, weighing 250-350g , housed in plastic cages for seven animals each, receiving food and water ad libitum, were used in the experiments. At least ten animals were submitted to each one of different experimental procedures.

Surgical procedures: The animals were anesthetized with ether and the abdominal skin was depilated and cleaned with iodine alcohol. The surgical procedures will be described for each different model .

a) Median incisional hernia without musclar ressection (figure 1). A 4 cm long supra and infra umbilical median incision was performed in the skin and subcutaneous tissue; after, these structures were dissected approximately 1.5 cm from the linea alba for each side. The linea alba and the peritoneum were sectioned in an extensiom similar to the first incision. The skin was closed with separated 2.0 cotton suture stitches.

Fig. 1
- Drawing showing the basic surgical procedures for induction of an incisional abdominal hernia without abdominal muscle resection. A - After skin incision the subcutaneous tissue is dissected in each side of the median line. B - Incision through the linea alba and peritoneum and suture of skin incision. Observe that the linea alba incision was not sutured (arrows).

b) Median incisional hernia after section of the linea alba through a supra-pubic transversal incision (figure 2 ). A 1.0 cm transversal supra pubic incision was performed in skin and subcutaneous tissue; then a scissors was introduced and the subcutaneous tissue was dissected approximately to 1.5 cm from the linea alba for each side, in an extension of 4 or 5 cm in direction of xiphoid appendix. The linea alba and the peritoneum were sectioned for an extension of 4 cm from the suprapubic incision. The transversal skin incision was closed with separated 2.0 cotton suture stitches.

Fig. 2
- Drawing showing the surgical procedure to induce an incisional hernia with intact skin over the hernial sac. A - A small transverse suprapubic skin incision followed by introduction of scissors to dissect the subcutaneous tissue in direction of xiphoid appendix. B - The linea alba and peritoneum are incised under the intact skin.

c) Control hernias induced by resection of fragment of abdominal muscle. For control, median incisional hernias were induced after ressection of a 3 X 4 cm fragment of abdominal muscles, as described by other authors 6,10.The skin incision was sutured as in (a) and (b).

RESULTS

There was no mortality among the operated rats.The hernias appeared in all animals and start to be noticeable 72 hours after surgery and two weeks later all animals submitted to the surgical procedures described presented hernias with different volumes (figure 3 ). The hernias induced without ressection of fragment of abdominal muscle were similar in volume to that induced after partial ressection of that muscle.The animals sacrificed between four and eight weeks presented hernias with all the elements: hernial ring, hernial sac and the content, represented by intestinal loops with omental adhesions to the hernial sac .(figure 3B)

Fig. 3
- Abdominal incisional hernia in rat induced without resection of abdominal muscle. A - Lateral view of a well developped hernia. B - Opened hernial sac showing the hernial ring (arrows) and an omental adhesion (arrow heads).

The development of the hernia when we did the skin incision and dissected the subcutaneus tissue before section of the linea alba was similar to that observed when a fragment of abdominal muscle was ressected. Also the result was similar when the linea alba was sectioned through a transverse suprapubic incision, after the dissection of subcutaneous tissue.

DISCUSSION

Our results showed that an abdominal incisional hernia can be easily induced in rats by performing an incision in the abdominal wall, with section of the linea alba, after dissection the subcutaneous tissue. It is not necessary to ressect fragment of the abdominal muscles, as did by some authors, but the dissection of the subcutaneous tissue is imperative. In fact, in animals in which the incison was performed but there was not the dissection of subcutaneous tissue, the hernia did not develop or, when developed ,were very small (data not showed). The dissection of subcutaneous appears necessary to facilitate the early protusion of intestinal loops, producing mechanical effect that impair the fast cicatricial process in the linea alba incision.

We think that these models we presented, without ressection of fragment of abdominal muscles, are better models for incisional hernia than that with partial ressection of abdominal muscle.

The induction of hernia sectioning the linea alba after introduction of the scissors through a small transverse suprapubic incision is less traumatic because the skin is not sectioned in the median line. In this procedure is also imperative the dissection of subcutaneous tissue. This model , similar to one proposed by Lazaro da Silva in dogs (personal communication) , is not similar to the incisional hernias observed in humans, in which there is section of the skin during the incision.

CONCLUSION

In conclusion, our results showed that an incisional abdominal hernia can be easily induced in rats , without ressection of fragment of abdominal muscle, since the subcutaneous tissue has been dissected 1 to 2 cm laterally to the incision. This model of incisional hernia in rats is more resembling the incisional hernias observed in man than that induced after adominal muscle ressection.

PAULO, D.N.S.; PEREIRA, F.E.L.; MATA, R.F., DAUAD, F.R.D.; PAULO, I.C.A.L. - Modelos experimentais de hérnias incisionais abdominais longitudinais, em ratos. Acta. Cír. Bras. 12(4):231-4, 1997.

RESUMO: Hérnias incisionais abdominais no rato têm sido produzidas pela ressecção de fragmento dos músculos de parede abdominal. Na tentativa de criar um modelo de hérnia incisional abdominal no rato, sem ressecção de fragmentos de músculo de parede abdominal, os seguintes procedimentos cirúrgicos foram realizados: (a) Ratos anestesiados com vapores de éter foram submetidos à uma incisão longitudinal mediana supra e infra umbilical, de 4 cm de comprimento, seguida do descolamento do tecido celular subcutaneo em uma extensão de 1,5 cm lateralmente à linha mediana; de cada lado; em seguida era feita uma incisão de linha alba e peritonio parietal com a mesma extensão de incisão cutânea; a incisão cutanea era suturada com pontos separados. (b) Ratos foram submetidos à uma incisão transversal, suprapúbica, através da qual se introduzia a tesoura e se descolava o tecido celular sub-cutâneo até 1,5 cm de cada lado da linha média em uma extensão de 4 a 5 cm em direção ao apêndice xifoide; em seguida era feita uma incisão na linha alba e peritônio parietal e suturada a incisão cutânea transversal. (c) Para controle, ratos foram submetidos à ressecção de um fragmento de 3 x 4 cm dos músculos da parede abdominal anterior, criando-se um grande defeito na parede abdominal. Todos os animais submetidos aos três procedimentos desenvolveram hérnias abdominais bem constituídas. Concluiu-se que hérnias abdominais incisionais podem ser facilmente induzidas no rato após incisão da parede abdominal, desde que o tecido subcutâneo seja deslocado lateralmente à incisão em extensão de pelo mínimo 1,5 cm.

DESCRITORES: Hérnia. Hérnia Incisional. Eventration.

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  • 1
    Laboratory of Experimental Surgery, Department of Surgery. Escola de Medicina da Santa Casa de Misericórdia de Vitória-EMESCAM-Vitória-Espírito Santo-Brazil
    2 MD, PhD.
    3 MD.

Publication Dates

  • Publication in this collection
    31 May 2001
  • Date of issue
    Dec 1997
Sociedade Brasileira para o Desenvolvimento da Pesquisa em Cirurgia Al. Rio Claro, 179/141, 01332-010 São Paulo SP Brazil, Tel./Fax: +55 11 3287-8814 - São Paulo - SP - Brazil
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