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Surgical Options and Prognosis for the Acute Abdomen: Small Intestine
V.L. Cook
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Take Home Message
Small intestinal resection should be performed in a logical organized manner. Epiploic foramen entrapment has a worse prognosis than other strangulating small intestinal lesions. Horses that require a jejunocecostomy have a worse prognosis than if a jejunojejunostomy or jejunoileostomy is performed.
Surgical Technique
Step 1: Identify and Correct the Problem
If a small intestinal lesion is suspected it is advisable to start by evaluating this first! Ideally systematic evaluation should start with locating the ileum by following the ileocecal band and running the intestine in an oral direction. One of the initial steps should be to palpate the right cranial quadrant for distended loops and locate the epiploic foramen to determine if small intestine is entrapped here. This is important as in these cases great care must be taken to gently manipulate the small intestine to prevent tearing of the portal vessels bordering the foramen. When correcting an epiploic foramen entrapment, feeding some non distended aboral intestine through the foramen first may help to reduce the stretch on the foramen and help reduce the entrapped intestine with less force.
The ileum may be involved in the lesion and therefore may not be readily exteriorized. In some cases access to the small intestine may be improved by exteriorizing the large colon first to allow easier palpation of the dorsal abdomen. If the ileum cannot be exteriorized a loop of small intestine is selected and followed in each direction to determine where the obstruction is occurring. For a strangulating lipoma, the easiest method of correction is to cut the constricting pedicle and this will usually instantly free the remaining small intestine and allow it to be exteriorized. In some heart pounding situations, it is impossible to exteriorize the constriction, and the pedicle must be blindly cut within the abdomen. In these cases great care is taken to first isolate the constricting band and ensure that the intestine itself will not be penetrated. A pair of Metzenbaum scissors can then be guarded and carried into the abdomen to blindly cut the band. Following this procedure, the adjacent mesentery of the affected small intestine should be carefully examined for the presence of iatrogentic rents or tears.
Step 2: Decompress the Intestine
Once the lesion is corrected the surgeon is frequently faced with multiple uncooperative loops of distended small intestine. Prior to performing a resection and anastomosis, gas and fluid that has built up orally to the obstruction must be removed. There are 2 basic choices for accomplishing this: 1) decompression into the cecum or 2) emptying through an enterotomy in the devitalized segment. It is the author’s preference to decompress the small intestine into the cecum. Using this technique there is less risk of contamination with no possibility of spillage of intestinal contents into the abdomen. Fluid contents pass into the cecum and colon, helping hydrate the often dry, firm contents of the colons which have an intact mucosa preventing endotoxin absorption. However, this technique also requires considerable manipulation of the small intestine as its contents have to be run the length of the intestine and through the ileocecal valve. Repeatedly running the small intestine like this is used as a model for the development of ileus in lab animals.1 Additionally, this may result in excess fluid in the cecum and performing a jejunocecostomy, when necessary, more difficult. Alternatively, after placement of an impervious drape under the intestine, an enterotomy may be created along the antimesenteric surface in the devitalized segment to allow fluid to drain directly out of the intestine. Less pressure is created in the distended intestine using this technique. However, once the bowel is open and draining, this segment can no longer be freely moved to allow correct placement of the intestinal segments for the anastomosis. This can be particularly problematic in cases of small intestinal volvulus. Therefore careful planning must be done before creating the enterotomy.
Step 3: Plan the Resection and Ligation of Mesenteric Vessels
Once the intestine is decompressed and the anatomic orientation of the intestine corrected, the appropriate site for the resection is determined. To ensure healthy intestine at the anastomosis it is better to err on the side of caution and remove additional oral intestine that is frequently inflamed and injured due to distention.2 Doyen clamps are placed at 60 degrees across the intestine close to a branch of the jejunal vasculature in order to ensure excellent blood supply to the anastomosis. The 60 degree angle results in a larger lumen size at the anastomosis and ensures excellent blood supply to the antimesenteric surface. A Penrose drain is then tied around the intestine approximately 6” from the Doyens to prevent spillage of ingesta. Once the Doyens are in place, vessels supplying the segment to be resected are double ligated using ligatures, or a ligature and LDS™. Prior to resecting the intestine it is highly advised to start the mesenteric closure particularly with large resections. This also helps ensure that the intestine does not rotate and become misaligned during the resection. A quick method for doing this is to “pleat” the mesentery onto itself. This is significantly quicker than the alternative of whip stitching the edges together.
Step 4: Resect and Anastomose
Once everything is set, the non viable intestine is resected by cutting sharply along the edge of the Doyens using a new scalpel blade. For an end-to-end jejunojejunostomy two stay sutures of #2-0 Vicryl are then placed in the seromuscular layer at the mesenteric and antimesenteric surfaces. The tags are not cut, but are held with hemostats to stretch the lumen and prevent a constriction at the site of the anastomosis. There is debate about whether a 2-layer or 1-layer closure should be performed. In a 2-layer closure the mucosa is first sutured with 3-0 Vicryl in a simple continuous pattern interrupted at 180 degrees. With a 1-layer closure this step is omitted. Then for both techniques, a single inverting Lembert suture is placed, using the suture from the preplaced stay sutures, interrupted at 180 degrees. For a 2-layer closure a Cushing pattern can be used but the author prefers a Lembert to provide better compression across the intestine resulting in an improved seal. [...]
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