The phrase ‘resection and anastomosis’ can send a shiver of anticipatory dread through many a fearless veterinarian. This is a reasonable response, given that so many things can go wrong and each one of them alone could result in surgical failure. This article is NOT a step-by-step for completing an anastomosis. There are many resources with detailed descriptions of various techniques. Instead, I would like to simply focus on how to occlude the intestine during the procedure. This seemingly small step is actually pretty critical in your overall success.
Why do we need to occlude the intestine to perform a resection and anastomosis or enterotomy? Simply put, to prevent contamination of the abdomen from leakage of intestinal contents. Most bowel pathology results in reduction of progress of intestinal contents, whether caused by an acute foreign body or chronic intestinal neoplasm.
In the event of a complete obstruction, the upstream (oral) intestinal segment may be severely dilated with chyme just waiting for an opportunity to evade your moist lap sponges, paper over-drapes and active suction. The downstream (aboral) intestine may be empty or mostly empty, but can still have enough potential contamination that it warrants occlusion during the procedure.
Intuitively, you probably guess that the best means for occlusion is a pair of fingers, and you would be correct. A properly prepared (sterile scrub, gown, gloves, cap and mask) assistant with enough knowledge to apply just the right amount of pressure is better than any fancy instrument. Two fingers gently occluding the bowel oral and aboral to the proposed resection or enterotomy can also position the bowel for the surgeon. That assistant can communicate any impending crisis of contamination. The intestinal vasculature and wall loves the assistant’s hands more than any instrument. Unfortunately, that second set of hands is not always an option.
What other choices are there? Several instruments have been developed over the years to help control contamination. The most common in veterinary literature are Doyen intestinal forceps which come in both curved and straight varieties. The three most striking features of non-crushing intestinal forceps are: 1) when closed there is still a gap between the blades of the instruments, 2) longitudinal grooves running the length of the blades and 3) the blades are generally light-weight. Each of these features help forceps such as Doyens occlude the lumen without resulting in crush damage to intestinal wall. It is important when placing the Doyens across a loop of intestine that you avoid the tips closing on the intestinal vasculature. The clamp should be closed to the fewest ‘clicks’ possible on the locking ratchet mechanism to reduce trauma to the bowel. Other varieties of non-crushing intestinal forceps include Kocher forceps, Scudder forceps and Glassman forceps. Some surgeons prefer to slide sterilized rubber sleeves over the jaws of non-crushing forceps to further minimize trauma. These sleeves create a smooth contact surface against the bowel.
Are there any non-metallic choices? A simple method is to use a ¼ inch Penrose drain in tourniquet style around the bowel. Taking care not to damage the vasculature, a small (3-5mm) window is made in the mesentery close to the bowel using a blunt instrument (such as a Mosquito hemostat) and a section of Penrose drain is drawn through. I like to rinse the Penrose first with sterile saline to decrease the amount of sterile talc that comes in contact with the intestinal mesentery. The drain is then tightened down on the antimesenteric side and clamped with a hemostat – only contacting the drain. This method does the least harm to the bowel wall and surface, but is also the least effective in preventing liquid from leaking from the cut end of the bowel. If the bowel has very good motility, it can overcome the tourniquet effect of the Penrose drain and force chyme through. One standard Penrose drain can be divided in two and used on both the oral and aboral segments. After completion of your enterotomy closure or anastomosis, the drain pieces are removed. Usually the small window in the mesentery does not require closure, but occasionally you will need to put a single interrupted suture of some small (4-0) absorbable suture. Other than a slightly higher risk of leakage compared to intestinal clamps such as Doyens, the other risk with the Penrose approach is to inadvertently pinch the intestinal wall with the hemostat when tightening the drain.
With any method of intestinal occlusion, it is important to inspect the bowel after removal of the clamp, drain or fingers for any damage to the wall or vasculature integrity. Ideally, within 2-3 minutes you should not be able to identify where the bowel had been occluded.
Paying close attention to proper occlusion of oral and aboral bowel during any procedure that requires opening of the intestinal tract is an important part of a successful surgery.