Introduction and surgical anatomy

• Unlike dehiscence of a skin wound, where in many cases the problem can be readily managed with the appropriate local treatment, dehiscence of an esophageal or GIT wound can lead to septic infection such as peritonitis Peritonitis or mediastinitis, severe moribidity and sometimes death. Therefore, technical failures and factors that might increase the risk of wound failure are of great relevance to the surgeon.
• Surgery of the GIT can be considered clean-contaminated at best, with the bacterial population increasing as you progress distally, therefore intraoperative spillage, leakage and wound dehiscence have progressively more severe consequences as you travel from stomach to small intestine to large intestine.
• There are certain aspects to the surgical anatomy of the GI tract that have direct relevence to potential postoperative complications, so these bear review.
• Esophagus: histologically the esophagus consists of four layers, the adventitia, the muscularis, the submucosa (including the muscularis mucosa) and the mucosa but no serosa. The vascular supply to the esophagus is derived from several sources. The cervical esophagus receives its supply largely from the thyroid arteries, the thoracic esophagus from the bronchoesophageal arteries and the distal esophagus from the gastric arteries. The thoracic section of the esophagus is less well vascularized than other areas and great care should be exercised when dissecting in this area. Historically the esophagus has been associated with poorer healing and a higher rate of incisional dehiscence than other portions of the GIT. This has been typically attributed to the lack of a serosa, the segmental nature of the blood supply and the pressure that swallowing places on a surgical incision. However, provided good surgical principles are carefully adhered to there is actually no reason to expect a poorer outcome. The lack of a serosa over the esophagus was held in the past to adversely affect healing by compromising the elaboration of a fibrin seal immediately after wounding. However, the presence of a serosa is not critical in visceral healing and healing of intestinal anastomoses has been demonstrated in experimental dogs regardless of stripping off the serosal layer. Although the segmental nature of the esophageal blood supply is generally quoted as a major contributor to complications, the intramural supply is equally important and should not be overlooked due to concentrating on the segmental extramural supply. There is currently no agreement on the appropriate period of time to withhold food and water postoperatively, nor whether it is necessary to place a feeding tube to bypass the surgical site. At the present time this is largely dictated by individual surgeon preference rather than by a suitable evidence base. The lower esophageal sphincter (LOS) islocated in the region of the gastro-esophageal junction. It is considered to be a physiologic, rather than an anatomic, sphincter and the exact location of the gastro-esophageal junction relative to the diaphragm is variable. This physiologic sphincter is augmented by and works in concert with certain extrinsic anatomic factors to maintain a competent anti-reflux barrier so disruption of any component of the system can lead to morbidity.
• Stomach: the position of the stomach in the cranial abdomen, partially covered by the caudal rib cage and lying in close apposition to the liver with the restrictive hepatogastric and hepatoduodenal ligaments can make access tricky, particularly in large breed or deep chested dogs.
• Small intestine: although the risk of morbidity and mortality from leakage of small intestinal contents is similar to that with gastric contents, the greater mobility of the small intestine makes it easier to isolate the segment that is to be operated on. The exception to this is the distal duodenum and section of small intestine that is tethered by the duodenocolic ligament. The overlapping blood supply between the duodenum and pancreas is essential to appreciate if operating on either of these structures to avoid inadvertent devitalization of adjacent viscera.
• Large intestine: the ascending colon is relatively tethered by its attachments to the mesoduodenum and mesocolon, which makes surgical manipulation more limited. The bulk of the blood supply to the colon comes from the cranial mesenteric artery, which branches as the common colic artery which then subdivides into ilieocolic, right colic, middle colic and left colic branches. These arteries connect to the colon via short vasa recti, with large numbers of anastomoses along the mesenteric border of the colon. During surgery care must be taken to preserve both this rich intramural blood supply, and also the segmental blood supply arising from the aforementioned iliocolic and colic arteries.
• Colorectal junction and rectum: the rectum extends from the pelvic brim caudally to the external anal sphincter. Most of the rectum lies within the peritoneal cavity, although a short section lies retroperitoneal before the junction with the anal canal. This means that dehiscence of a surgiacl incision can potentially lead to very different complications depending on the location. The intraperitoneal portion of the rectum has four layers - mucosa, submucosa, muscularis and serosa. The extraperitoneal (caudal) portion of the rectum lacks a serosa. In dogs, the main blood supply is the cranial rectal artery with the middle and caudal rectal arteries providing varying and usually insignificant supplies. For this reason, it is important to preserve the cranial rectal artery during surgery. In cats the middle and caudal rectal arteries provide a more reliable supply to the intrapelvic rectum. The autonomic nerve fibres of the pelvic plexus innervating the rectum and internal anal sphincter are contained within the bilateral peritoneal reflections at the level of the second coccygeal vertebra in dogs or slightly more caudal in cats. If these are damaged or transected during surgery incontinence may result.

Principles of GIT surgery

Closure of GIT wounds (suture, handsewn)

Closure of GIT wounds (stapled)

Intestinal wound dehiscence

Effect of early postoperative enteral feeding on visceral healing

Further Reading

Publications

Refereed papers

• Recent references from PubMed and VetMedResource.
• Ellison G W (2011) Complications of Gastrointestinal Surgery in Small Animals. Vet Clin Small Anim 41 (5), 915-934 PubMed.
• Jardel N, Hidalgo A, Leperlier D et al (2011) One stage functional end-to-end stapled intestinal anastomosis and resection performed by nonexpert surgeons for the treatment of small intestinal obstruction in 30 dogs. Vet Surg 40 (2), 216-222 PubMed.
• Banz W J, Jackson J, Richter K et al (2008) Transrectal Stapling For Colonic Resection And Anastomosis (10 cases). J Am Anim Hosp Assoc 44 (4), 198-204 PubMed.
• Shales C J, Warren J, Anderson D M et al (2005) Complications following full-thickness small intestinal biopsy in 66 dogs: a retrospective study. Journal of Small Animal Practice 46 (7), 317-321 PubMed.
• Ralphs S C, Jessen C R, Lipowitz A J (2003) Risk factors for leakage following intestinal anastomosis in dogs and cats: 115 cases (1991-2000). J Am Vet Med Assoc 223 (1), 73-77 PubMed.
• Kirpensteijn J, Maarschalkerweerd R J, van der Gaag I et al (2001) Surgery: Comparison of three closure methods and two absorbable suture materials for closure of jejunal enterotomy incisions in healthy dogs. Vet Quarterly 23 (2), 67-70 PubMed.
• Coolman B J, Ehrhart N & Marretta S M (2000) Use of Skin Staples for Rapid Closure of Gastrointestinal Incisions in the Treatment of Canine Linear Foreign Bodies. J Am Anim Hosp Assoc 36 (6), 542-547 PubMed.
• Crowe D T Jr. (1984) The Serosal Patch. Clinical Use in 12 Animals. Vet Surg 13 (1), 29-38 VetMedResource.

Other sources of information

• Murgia D (2013) Surgery of the small intestine in dogs and cats: part I. Companion Animal 18 (3), 114-119.
• Murgia D (2013) Surgery of the small intestine in dogs and cats: part II. Companion Animal 18 (4), 158-164.
• Brown D C (2012) Small Intestine. In: Tobias K M & Johnston S A (eds) Veterinary Surgery Small Animal. St Louis, Missouri: Elsevier Saunders. pp 1513-1541.
• Cornell K (2012) Stomach. In: Tobias K M & Johnston S A (eds) Veterinary Surgery Small Animal. St Louis, Missouri: Elsevier Saunders. pp 1484-1512.
• Kyles A E (2012) Esophagus. In: Tobias K M & Johnston S A (eds) Veterinary Surgery Small Animal. St Louis, Missouri: Elsevier Saunders. pp1461-1483.
• Williams J M (2012) Colon. In: Tobias K M & Johnston S A (eds) Veterinary Surgery Small Animal. St Louis, Missouri: Elsevier Saunders. pp 1542-1563.