Use of a Rat Model to Study Ventral Abdominal Hernia Repair

The overall goal of this ventral abdominal hernia repair model is to facilitate the assessment of potential hernia repair biomaterials. This method can help answer key questions in the surgical biomaterials field about the suitability and biocompatibility of candidate materials for ventral abdominal hernia repair. The main advantage of this technique is that it utilizes a rat model, thereby allowing the evaluation of hernia repair materials that may be of limited supply.

After confirming the appropriate level of anesthesia of a healthy 250 gram adult rat by toe pinch, apply lubricant to the animal's eyes and subcutaneously administer sterile saline. Use a pair of clippers to shave the ventral abdomen from the pubis to the sternum and from the lateral margins on the ventrum. Apply a moist paper towel to the shaved area to remove the clipped hair, and scrub the exposed skin with an iodoform antiseptic and a 70%ethanol wipe.

After donning the appropriate personal protective equipment, thoroughly scrub both hands with soap and don a pair of sterile surgical gloves. Next, drape the animal. And use a scalpel to make an approximately three to four centimeter vertical incision down the ventral midline to abdominal musculature.

Using forceps, gently lift the abdominal wall and create a small opening through the linea alba. Then, to protect the underlying viscera, insert another forceps through the hole into the abdominal cavity to create an approximately two by two centimeter full thickness defect, cutting approximately one centimeter lateral from each side of the midline on both ends of the linea alba incision. Next, lay a precut two by two centimeter section of implant material over the defect.

Because the abdominal wall will retract laterally upon incision, it is important to establish the general anatomical boundaries, ensuring the creation of a defect in the tissue wall that corresponds to the size of the implant. And use a 4-0 nylon suture to suture the four corners of the bridging material to the abdominal wall in a simple interrupted suture pattern. Secure each edge of the material with three additional equally spaced sutures.

Then examine the entire circumferential edge to ensure significant gaps do not exist. Any unsecured implant margins present an opening through which the abdominal viscera can potentially herniate. Therefore it is essential to make sure that all of the edges are anchored to the body wall.

When the implant is secure, close the skin with surgical staples. Seven to 10 days after the surgery, remove the skin staples. 21 to 28 days after the surgery, the rat is euthanized.

Open the skin and abdominal wall to expose the area of the implant. Note any gross pathological observations, including any adverse reactions and adhesion extent and tenacity to the underlying viscera. Then harvest a wide section of tissue that includes the implant and place the implant site sample into the appropriate fixative for the desired downstream processing procedure if the sample is to be used for histopathological examination.

By 28 days after implantation, the small intestinal submucosa or SIS typically demonstrates a good incorporation into the host tissue. In most cases, residual SIS is apparent, although the tissue must often be explored to identify the implanted material. Histological analysis further confirms the gross pathological observations, illustrating a good tissue incorporation with primarily fibrovascular tissue and very little notable residual SIS in demonstrating the utility of the rat ventral abdominal hernia model.

Once mastered, this technique can be completed in 30 minutes if it is performed properly. While attempting this procedure, it's important to remember to provide adequate postoperative analgesia to the animal. Following euthanasia and harvest of the implant, other methods like mechanical strength testing can be performed to answer additional questions like, is the reparative abdominal defect sufficiently strong?

After watching this video, you should have a good understanding of how to surgically create a ventral abdominal hernia in the rat.