Stomach

Anatomy

Gastric anatomy may be divided into gross or topographical anatomy of the stomach and histologic or cellular anatomy of its component parts.

Grossly, the stomach is divided into the cardia, fundus, body, and pyloric portions (Figure 91-1). The point where the intraabdominal esophagus blends into the stomach on the left side is termed the cardia. The cardiac notch is formed between the cardia and the blind outpouching of the stomach, termed the fundus. On the medial aspect, the esophagus joins the lesser curvature of the stomach without a distinct anatomic landmark of the junction. The incisura angularis (angular notch) produces an intraluminal protrusion of tissue at approximately the midpoint of the lesser curvature that separates the antrum and the cardia. This angular notch is the area in which the papillary process of the liver lies. During endoscopic examination of the stomach, the incisura angularis is an important landmark.

Figure 91-1 A, Anatomy of the stomach. B, Musculature and named regions of the stomach. (From Evans H, de Lahunta A: Miller’s anatomy of the dog, ed 4, St Louis, 2013, Saunders/Elsevier.)

The body of the stomach lies between the fundus and the pylorus and is the largest component part of the stomach. The distal third of the stomach is the pylorus, which joins the body of the stomach to the duodenum. The pyloric portion of the stomach is divided into the thinner walled pyloric antrum and the area known as the pyloric sphincter, which is defined by the double muscle layer that surrounds it. The greater curvature of the stomach is convex and connects the cardia and pylorus and incorporates the fundus. The lesser curvature also connects the cardia and pylorus but is much shorter than the greater curvature.

Omentum

The greater and lesser omentum are attached to the stomach at the greater and lesser curvatures, respectively. The greater omentum is divided into three portions known as the bursal, splenic, and veil portions (Figure 91-2). The bursal portion attaches along the greater curvature except on the left, where it runs obliquely across the dorsal surface of the stomach and joins the lesser omentum to close the omental bursa. The splenic portion of the greater omentum forms the gastrosplenic ligament, through which the gastroepiploic vessels course to the stomach. A portion of the lesser omentum forms the hepatogastric ligament that passes from the liver to the stomach.

Figure 91-2 A, Components of the gastric attachments of the omentum. Note the gastrosplenic ligament, superficial leaf of the greater omentum, and lesser omentum attachments. The arrow passes through the omental bursa. B, Peritoneal anchor points of the stomach with all of the abdominal viscera removed. Note the right and left triangular ligaments. (From Evans H, de Lahunta A: Miller’s anatomy of the dog, ed 4, St Louis, 2013, Saunders/Elsevier.)

Vasculature, Lymphatics, and Innervation of the Stomach

The arterial blood supply of the stomach originates from the celiac artery, a direct branch from the aorta. The celiac artery divides into its component parts, the splenic, hepatic, and left gastric arteries (Figure 91-3, A). Each of these arteries provides blood flow to a portion of the stomach. The splenic artery gives off tributaries to the left limb of the pancreas and the spleen before becoming the left gastroepiploic artery, which supplies the greater curvature of the stomach and anastomoses with the right gastroepiploic artery. The hepatic artery gives off branches to the liver and gallbladder and then continues as the right gastric artery, which supplies blood to the pylorus and pyloric antrum, after which it anastomoses with the left gastric artery along the lesser curvature of the stomach (see Figure 91-3, A). After the right gastric artery branches from it, the hepatic artery continues as the gastroduodenal artery. The gastroduodenal artery travels to the duodenum, where its branch—the cranial pancreaticoduodenal artery supplies the right pancreatic limb; its branch—the right gastroepiploic artery—supplies the greater curvature of the stomach, as described above. The left gastric artery is a direct branch from the celiac artery that supplies the fundus of the stomach and provides small branches to the caudal esophagus before joining the right gastric artery. The short gastric arteries originate from splenic branches of the splenic artery and anastomose with the gastric branches of the left gastric artery to supply the fundic area of the stomach. The lesser curvature is supplied by the left gastric artery and its anastomosis with the right gastric artery.

Figure 91-3 A, Arterial supply to the stomach. B, Venous drainage of the stomach. (From Evans H, de Lahunta A: Miller’s anatomy of the dog, ed 4, St Louis, in press, Saunders/Elsevier.)

The venous drainage of the stomach to the portal vein is through the gastrosplenic vein on the left and gastroduodenal vein on the right (see Figure 91-3, B). Lymphatic drainage of the stomach is through the gastric and splenic lymph nodes to the hepatic lymph nodes.¹⁵ The stomach is innervated by parasympathetic fibers of the vagus nerves and sympathetic fibers of the celiac plexus.^47a The ventral vagal trunk passes through the esophageal hiatus and then sends small branches to the pylorus, liver, and lesser curvature of the stomach. The dorsal vagal trunk sends branches to the lesser curvature and ventral wall of the stomach and then continues across the celiac plexus to follow branches of the celiac and cranial mesenteric arteries. Sympathetic fibers arise from the celiacomesenteric plexus and follow gastric branches of the celiac artery.

Gastric Morphology and Glandular Organization

Gastric Layers

The stomach wall is composed of four distinct layers; from the external to the internal surface, they are the serosa, muscle, submucosa, and mucosa. The muscular composition of the stomach is divided into three layers. The longitudinal layer passes longitudinally from the esophagus to the duodenum along the greater curvature of the stomach. These longitudinal fibers end before reaching the middle of the body of the stomach on the lesser curvature and the dorsal and ventral surfaces of the stomach. The inner circular layer begins at the cardia, where it forms part of the gastroesophageal (cardiac) sphincter. It extends through the greater curvature, where it is thickest, to the pylorus, where it facilitates the grinding function of the antrum. The circular layer is not present in the fundus. The oblique muscle fibers, which are primarily over the body and fundic areas of the stomach and are adjacent to the submucosa, begin near the cardiac orifice and extend toward the pylorus and greater curvature in each wall. The submucosa is composed of a thin elastic layer of areolar tissue and serves as the critical holding layer during surgical closure of gastric incisions. The mucosal layer is made up of columnar surface epithelium, a glandular lamina propria, and a lamina muscularis mucosa.

Glands

Glands of the stomach include the cardiac, pyloric, and gastric glands proper. Their composition differs with various regions of the stomach. The cardiac glands are located primarily around the cardia but are also present in the antrum; they produce a serous secretion. The pyloric glands may be found in the pylorus and gastric body; they primarily produce mucus. The gastric glands proper are located in the fundus and body and are composed of parietal, chief, mucous neck, and endocrine cells (Figure 91-4 and Table 91-1). The parietal (oxyntic) cells have two primary functions: to maintain gastric acidic pH (pH, 2–3) by pumping hydrogen ions into the gastric lumen and to produce intrinsic factor, a mucoprotein that binds to B₁₂ to permit its absorption in the distal small intestine. The acidic gastric environment allows activation of gastric enzymes necessary for the breakdown of food. Chief cells secrete pepsinogen, which is converted in the acidic environment to pepsin, which in turn functions to break down proteins. Neck mucous cells secrete mucus that protects other glandular cells from the action of the proteases and the hydrochloric acid. Gastric endocrine cells produce gastrin, histamine, and serotonin.

Table • 91-1

Location and Function of the Secretory Cells of the Stomach

CELL	LOCATION	PRODUCT(S)
Parietal	Body	Acids and intrinsic factor
Mucus	Body, antrum	Mucus
Chief	Body	Pepsinogen
Surface epithelium	Diffuse	Mucus, bicarbonate
Endocrine cells	Body	Histamine Gastrin Serotonin

Figure 91-4 Cell types in the glands of the stomach. (From Ettinger S: Textbook of veterinary internal medicine, ed 7, Philadelphia, 2009, Saunders/Elsevier.)

Physiology

Motility

The stomach functions as a temporary reservoir where digestive juices are added and an area for grinding of food and release of hydrochloric acid. As the fundus fills in response to entry of food into the stomach, the stomach first distends in a caudodorsal direction. Swallowing initiates a receptive relaxation that decreases fundic motor activity and pressure. As the pressure in the fundus builds, gastric accommodation occurs, resulting in further relaxation of the fundus. This decreased motility in the fundus directly slows the gastric emptying rate of fluids. After surgical resection of the fundus in dogs, the rate of gastric emptying of fluids is increased because of a resultant increase in pressure after the same change in volume.

During active digestion, the body of the stomach dilates and motility increases in order to mix food and move it toward the antrum. The pattern of motility in the antrum serves to churn the food by forcing ingesta aborally into the area of the pylorus, and the pylorus closes before completion of the antral contraction. This sequence of events allows only the liquid chyme to pass into the duodenum; the remaining gastric contents are forced retrograde, where additional churning results in breakdown of food into appropriate-sized particles. The gastric emptying rate for solid food is therefore greatly impacted by this coordinated contraction of antrum and pylorus; the emptying rate for liquids is more influenced by fundic motility.94,161

Healing Characteristics

Normal gastric mucosa is undergoing constant renewal. In the stomach, mucosa is protected by normal cytoprotective mechanisms from autodigestion by gastric acid and digestive enzymes. When superficial epithelial injury occurs, it is repaired rapidly by epithelial migration without proliferation. Gastric mucosa erosions heal rapidly by epithelial regeneration.⁶⁸

Injury that extends into the submucosal layer is considered an ulcer and is associated with a fibrotic repair process. Scar formation with fibrous protein synthesis occurs and predominates over wound contraction.⁴⁴ If the depth and duration of gastric insult are minimized, the resultant scar is often resorbed. In long-term injury, a profound fibrotic response may result in permanent scar formation.

Incisional healing differs from the previously described healing process because, although a full-thickness injury is created, it is of short duration. Standard phases of wound healing, including inflammation, debridement, repair, and maturation, occur in gastric healing. In contrast to other healing tissues in which collagen is produced by only fibroblasts, smooth muscle cells of the gastrointestinal tract contribute to collagen production during gastrointestinal wound healing.⁶⁸ Healing in the stomach is enhanced by its extensive and redundant blood supply.

Presurgical Preparation

Indications for gastric surgery and ideal patient preparation for the procedure are frequently incompatible. Preferably, the patient should be physiologically stable; however, the underlying condition requiring surgical correction (e.g., gastric dilatation and volvulus) may preclude complete stabilization. Electrolyte, acid–base, and hydration status should be evaluated and abnormalities corrected before surgery, when possible. Abnormalities in these parameters may be associated with alterations in blood pressure or cardiac function that may require additional supportive care. Preoperative diagnostics and medical management are described later in this chapter in association with specific gastric conditions.

Fasting

Withholding food for a minimum of 8 to 12 hours before surgery has been recommended to ensure an empty stomach and minimize the risk of gastric spillage during the operative procedure. The duration of presurgical fasting required to produce an empty stomach depends on the disease process or reason for surgical intervention. In cases of functional pyloric outflow obstructions, the duration of the required fast may be significantly longer to ensure an empty stomach.

Fasting before gastric surgery, however, may have negative consequences. Longer fasting times in humans and dogs reportedly decrease gastric pH, are linked to a higher incidence of gastroesophageal reflux, and do not reliably decrease gastric content volumes.58,81,110,118,153 Gastroesophageal reflux is an important complication associated with any anesthetic event and with gastric surgery in particular. Wilson et al.¹⁸⁰ documented gastroesophageal reflux in 57% (51 of 90) of dogs undergoing anesthesia for orthopedic procedures, but clinically obvious regurgitation was noted in only 14% of anesthetized patients. These findings suggest that the esophagus is exposed to an acidic environment in more than 50% of anesthetized patients but that this event is clinically evident in only a small percentage of animals. This “silent” exposure of the esophagus to acidic gastric contents may predispose anesthetized animals to esophagitis and esophageal stricture. In a report of 13 cases of postanesthesia esophageal dysfunction, only 46% (6 of 13) of cases were noted to have clinical evidence of regurgitation while under anesthesia.¹⁷⁹ Ten of the 13 dogs developed esophageal stricture, and three were ultimately euthanized. Based on these findings and the findings of Savvas et al.¹⁵³ small amounts of canned food fed 3 hours before surgery may decrease gastric acidity and minimize the occurrence and clinical impact of gastroesophageal reflux while having minimal to no impact on gastric content volume.

Anesthetic Considerations

Anesthetic considerations for patients undergoing gastric surgery are closely tied to the underlying disease process. Clinical signs frequently associated with gastric disorders include vomiting and regurgitation; as such, administration of anticholinergics such as atropine or glycopyrrolate should be considered in an effort to reduce gastric secretions. When gastric reflux into the esophagus is considered likely, preoperative administration of an H₂ receptor blocker such as cimetidine, ranitidine, or famotidine may be indicated to decrease gastric pH and minimize esophageal damage. When vomiting is a significant concern, rapid induction (e.g., intravenous propofol) and intubation without delay are indicated to provide immediate airway protection. In cases of obstruction, such as gastric dilatation and volvulus or pyloric outflow obstruction, nitrous oxide should be avoided because of its rapid diffusion into gas-filled organs. Mechanical ventilation may be required in cases in which the abdominal incision must be extended through the diaphragm.

Antimicrobials

Bacterial numbers in the stomach are significantly less than in the remainder of the gastrointestinal tract because of the acidic nature of stomach secretions. In specific cases such as gastric perforation, obstructive disease with possible bacterial overgrowth, and gastric dilatation and volvulus, antibiotics are indicated perioperatively. In other instances when the lumen of the stomach must be entered and the surgeon believes there is an increased risk of contamination, administration of prophylactic antibiotics should be considered.

General Surgical Principles

Several factors are associated with gastric surgery that make it challenging. First and foremost, the risk of gastric content leakage is considerable and may result in significant postoperative morbidity and mortality. Additionally, visualization and manipulation of the stomach is difficult based on its location in the cranial abdomen under the ribs and the presence of restrictive anatomic structures such as hepatogastric and hepatoduodenal ligaments that anchor the stomach in its normal position. Both ligaments may be carefully transected to aid in reflection of the stomach and visualization of the dorsal surface. Unlike the small intestine, however, the stomach cannot be exteriorized completely to allow isolation from the remaining abdomen. If necessary, the approach can be altered to improve exposure.

Approach

When performing gastric surgery, adequate visualization of the stomach is imperative and requires an abdominal incision of sufficient length. Gastric surgery of the small animal patient is most commonly performed through a ventral midline abdominal incision that extends from the xiphoid process of the sternum to a point caudal to the umbilicus and, in many instances, to the cranial extent of the pubis. Because of position of the stomach under the ribs and sternum, extension of the approach via a caudal median sternotomy may be required in some situations to obtain adequate exposure. In the standard ventral midline approach, visualization is maximized by the use of a Balfour retractor to retract the abdominal wall.

In rare instances when exposure of only a portion of the stomach is required, a paracostal approach may be used. A paracostal approach is achieved by making a curved incision approximately 2 cm caudal to the last rib. The underlying muscle layers, including the external and internal abdominal oblique and transversus abdominis muscles, are split longitudinally along the direction of the muscle fibers. When ventral extension of the incision is necessary for visualization, the rectus abdominis muscle may require transection. Closure is achieved with a simple continuous pattern in each muscle layer (Figure 91-5).

Figure 91-5 Paracostal approach. Muscles are bluntly divided between muscle fibers longitudinally. (From Knecht CD, Allen A, Williams DJ, et al: Fundamental techniques in veterinary surgery, ed 3, Philadelphia, 1987, Saunders/Elsevier.)

Minimizing Contamination

Minimizing the risk of and consequences of gastric content spillage is achieved by carefully packing off the stomach from the remaining abdomen using laparotomy sponges moistened with warm sterile saline solution. Stay sutures of 2-0 or 3-0 monofilament suture on a taper needle are placed surrounding the area of interest using large full-thickness bites that will not tear through the gastric wall and are grasped by hemostatic forceps to elevate the stomach before entry into its lumen. Separate instruments should be designated for the clean and the clean-contaminated portions of the procedure and segregated to prevent contamination. After completion of the clean-contaminated portion of the procedure, the used instruments should be removed from the surgical field, and participants in the clean-contaminated procedure should change surgical gloves. The abdomen is lavaged, and clean instruments are used for abdominal closure.

Lavage

The abdominal cavity should be lavaged with sterile saline or lactated Ringer’s solution and suctioned dry after the gastrointestinal tract is closed. Temperature recommendations for lavage solution vary, with 37° C to 39° C (98.6° F to 102.2° F) most commonly reported. Nawrocki et al.¹²⁴ confirmed that lavage of the canine abdominal cavity with room temperature saline 21° ± 1° C (70° ± 3° F) significantly decreased body temperature. Additionally, lavage with a saline solution heated to 43° ± 2° C (110° ± 4° F) significantly increased body temperature compared with body temperature before lavage and with dogs undergoing room temperature lavage.¹²⁴ Increased body temperature may be beneficial to patients undergoing abdominal surgery because core body temperature decreases significantly during these procedures. One concern not addressed in this study, however, was the long-term effect of high temperature lavage solution. Warmer fluids may result in vasodilation and resultant hypotension and an increased risk of adhesion formation.¹⁴³ The surgeon must balance the need for increasing core body temperature before closure with potential detrimental effects of abdominal lavage with fluids 43° ± 2° C (110° ± 4° F).

Gastric Closure

Suture Patterns

The closure technique used for gastric surgery depends on the incision location and indication for the initial incision or resection. Routine closure of a gastric body incision may be achieved with a continuous double-layer inverting closure in which the first suture line is full thickness and the second line incorporates only the serosa and muscular layers. Alternatively, the first suture line may incorporate only the mucosa, and the second line inverts the remaining layers of gastric tissue. Inverting patterns used for these applications include Cushing, Connell, and Lembert patterns. A two-layer closure technique is advantageous because the inner layer provides hemostasis of gastric mucosa and submucosa and the outer layer prevents gastric content leakage.

For pyloroplasty or gastroduodenal or gastrojejunal anastomosis, an inverting pattern is contraindicated because a reduction in lumen diameter associated with a double-layer inverting pattern cannot be tolerated in these locations. Closure is often performed with an interrupted or continuous appositional pattern that incorporates submucosa.

Suture Material

The choice of appropriate suture material for closure of the stomach is dictated by the need for a material that resists rapid degradation in the acid- and enzyme-rich environment of the gastric lumen for the 14 days necessary to regain gastric wall strength.52,164 Most commonly, monofilament absorbable materials such as polydioxanone, polyglyconate, or poliglecaprone 25 are used. Polydioxanone undergoes a rapid and significant loss of tensile strength in an acidic environment.^57,166 In fact, when incubated in a solution with a pH of 1 for 2 weeks, the tensile strength of polydioxanone was no longer measurable.¹⁶⁶ In a biodegradation study by Tomihata et al.⁵⁷ nine common absorbable sutures were immersed in gastric fluid or a solution with a pH of 2. The half-life of polydioxanone was 10 times shorter at that pH than at a pH of 7.4. Additionally, polydioxanone was the only suture in that study to be significantly negatively impacted in tensile strength by gastric fluid.⁵⁷ In contrast, polyglycolide and poly l-lactide-coglycolide had initial delays in linear absorption, presumably secondary to the coating on each of these materials. In Tomihata’s study, the half-lives in gastric fluid for polyglyconate, poliglecaprone 25, and polydioxanone were 75, 15, and 12 days, respectively, supporting use of polyglyconate or poliglecaprone 25 in gastric surgery.⁵⁷ Based on rapid degradation of chromic and plain catgut in gastric juices, use of these materials is not recommended.¹⁶⁴

Staples

Gastric surgery may be performed with thoracoabdominal, gastrointestinal anastomosis, and skin staplers.10,30,31,80,165 Thoracoabdominal and gastrointestinal anastomosis staplers have been used in gastrectomy, pylorectomy, and gastrojejunostomy procedures.²,³⁰ Because of potential necrosis along the staple line and resultant leakage of gastric content, oversewing of the staple line is recommended.²⁸ Gastropexy for prevention of gastric dilatation and volvulus can be performed with gastrointestinal anastomosis or skin staplers.^10,31,80 In one study, use of a skin stapling device for gastropexy provided results similar to hand-sewn belt loop gastropexy with regard to tensile strength. A significant difference in the time required to perform the procedure was noted; however, the difference was less than 4 four minutes and is likely not clinically relevant.³¹ In a more recent study, gastropexy performed with a gastrointestinal anastomosis stapler was successful in creating a permanent adhesion; in this clinical study, however, the time to perform the gastropexy was not compared with hand-sewn gastropexy.¹⁰

General Surgical Techniques

Gastric Biopsy

Gastric biopsy is indicated in the presence of gross disease of the stomach and when clinical signs are consistent with upper gastrointestinal disease. Endoscopic gastric biopsy is associated with a low morbidity and a low risk of complications. However, in instances when the disease is submucosal or scirrhous in nature, endoscopic biopsy is inadequate because of the inability to obtain a full-thickness gastric wall sample.

Patient preparation before open surgical biopsy of the stomach is as important as the actual technique used to obtain the tissue. Because of its location, the stomach cannot be fully exteriorized to prevent gastric content spillage. Therefore, the stomach must be isolated from the remaining abdominal contents with moistened laparotomy sponges and spillage minimized by preplacement of stay sutures in a manner that permits elevation of the area surrounding the biopsy site. An additional suture may be introduced into the area of the tissue to be biopsied to provide retraction and minimize crush artifact. Alternatively, a simple stab incision may be made into the lumen of the stomach while providing upward retraction with appropriate (e.g., DeBakey) thumb forceps. The incision is then extended with Metzenbaum scissors, and an elliptical full-thickness tissue sample is removed.

Closure of the biopsy site is most commonly achieved with a two-layer pattern. The first layer may be a simple continuous appositional pattern or an inverting pattern such as a Connell or Cushing pattern. A second inverting layer follows the first and incorporates at least the serosal and muscularis layers of the stomach. When placing an inverting pattern, care should be taken to ensure that the inverted gastric tissue does not interfere with outflow from the pylorus. Iatrogenic gastric outflow obstruction has been reported after gastric surgery.⁵⁴

Gastrotomy

The stomach is isolated from the remainder of the abdomen with moistened laparotomy sponges, and stay sutures are placed at the appropriate points. A gastrotomy is performed on the ventral surface of the stomach midway between its lesser and greater curvatures in the area with the least vascularity. The underlying reason for the gastrotomy dictates the location and length of the incision (see section on gastric foreign body removal). Closure of the gastrotomy incision is accomplished in the same fashion as described for closure of a gastric biopsy described above.

Partial Gastrectomy

Partial gastrectomy is most frequently performed to remove necrotic stomach wall associated with gastric dilatation and volvulus or to resect a neoplasm. Partial gastrectomy incorporates many of the same principles as gastrotomy, such as isolation of the stomach with moistened laparotomy pads to prevent gastric content spillage and placement of stay sutures to provide gastric wall retraction and control of gastric contents.

Determining Tissue Viability

When performing partial gastrectomy, it is critical that all nonviable tissue be excised. Viability of gastric mucosa does not predict overall health of the gastric wall; thus, other criteria must be used to assess gastric wall viability. Subjective criteria include gastric wall thickness, as measured by palpation; serosal surface color; evidence of serosal capillary perfusion; and presence of peristalsis.¹¹² Subjective findings consistent with nonviable gastric wall include a wall that is thinner than normal or serosal surface color of grey-green to black. Although subjective criteria proved to be 85% accurate in an experimental model when performed by an experienced surgeon, incorrect interpretation of subjective findings resulted in subsequent gastric perforation or dehiscence of gastrectomy sites in dogs with naturally occurring gastric dilatation and volvulus.¹¹² When wall viability is in question based on subjective criteria, the seromuscular layer can be incised to evaluate arterial vascular supply.

Objective data to predict gastric perfusion have been pursued through several methods, including fluorescein dye injection, scintigraphy, and laser Doppler flowmetry.13,121,176 In dogs with gastric dilatation and volvulus, fluorescein injection and scintigraphy were accurate in 58% and 79% of dogs, respectively.^13,176 Results of laser Doppler flowmetry in dogs with gastric dilatation and volvulus were consistent with concurrent subjective findings of the surgeon.¹²¹ Further study is required before this technique has application in clinical decision making.

Gastric Wall Resection and Closure

When performing a partial gastrectomy, care must be taken to ligate the appropriate associated blood vessels. These vessels may be ligated by hand or with a ligate and divide stapler. The closure technique used for partial gastrectomy depends on the location within the stomach and remaining lumen diameter. When the lumen diameter permits and the presence of inverted tissue does not increase the potential for pyloric outflow obstruction, a two-layer inverting pattern is appropriate. When the lumen diameter is not adequate to allow inverting closure, a simple continuous suture pattern is most appropriate.

Gastric Wall Invagination

Invagination has been proposed as an alternative to partial gastrectomy in cases with areas of questionable viability.¹⁰⁶ A simple continuous or inverting suture pattern and a second inverting suture pattern, with bites placed in healthy tissue on each side of the necrotic portion of the stomach, are placed to invaginate the unhealthy gastric wall. The result is apposition of healthy tissue over necrotic tissue without penetration into gastric lumen, thereby decreasing the risk of gastric contents spillage. The devitalized area of stomach wall is then sloughed into the gastric lumen and digested. In an experimental study, gastric compromise was induced through ligation of varying components of the gastric vascular supply and the affected area invaginated.¹⁰⁶ Fourteen days after invagination of the compromised areas, gastric ulcers of varying depths and clinical relevance were reported in the majority of dogs. Based on these results, the authors recommended further study of gastric healing after invagination. One dog developed a gastric ulceration 21 days after invagination that required surgical resection.¹²⁷ Signs of obstruction secondary to the sloughing of large amounts of tissue into the gastric lumen have also been reported.⁵³

Gastropexy

Gastropexy is the creation of a permanent adhesion of the stomach to the adjacent body wall. Gastropexy is most commonly performed for prevention of gastric dilatation and volvulus but is also used in the treatment of hiatal hernia. Gastropexy for prevention of gastric dilatation and volvulus is performed between the pyloric antrum and the right abdominal wall.

A variety of gastropexy techniques have been reported with varying degrees of success. Techniques include incisional, belt-loop, circumcostal, endoscopically assisted, and laparoscopic gastropexy; gastrocolopexy; incisional gastropexy through a grid approach; and incorporating gastropexy, in which the gastric wall is included in the linea alba closure.* The key component to successful gastropexy is incision through the serosal and peritoneal surfaces and into the muscular portion of each anatomic component being joined. For prevention of gastric dilatation and volvulus, the intraabdominal body wall incision of an incisional, belt-loop, laparoscopic, or endoscopic gastropexy is made caudal to the last rib to prevent penetration of the diaphragm and subsequent pneumothorax.

Regardless of the type of gastropexy technique, the goal is to anchor the stomach in as normal an anatomic position as possible. A frequent error in open procedures is securing the gastropexy to the body wall too ventrally because this is the easiest place to visualize and suture.

The results of biomechanical testing for commonly used open gastropexy techniques are similar (Table 91-2).^{55,80,145,174,181} Quantitative results of biomechanical testing must be interpreted carefully because the absolute strength of gastropexy required to prevent development of gastric dilatation and volvulus is unknown. There has not been an experimental study of strength of incorporating gastropexy.

Table • 91-2

Mechanical Testing of Gastropexy Techniques

Incisional Gastropexy

Incisional gastropexy for prevention of gastric dilatation and volvulus is performed by creating a 4- to 5-cm seromuscular incision in the gastric antrum either parallel or perpendicular to the long axis of the stomach. Care should be taken to avoid penetration of the gastric mucosa. Application of pressure from the dorsal surface of the stomach directly opposite the incision site aids in opening the incision and allows visualization of the layers as they are incised. Alternatively, digital pressure or pinching of gastric wall on the ventral surface at the site of the proposed incision may allow separation of the mucosal surface away from the seromuscular layer. A second incision is made through the peritoneum and the transverse abdominis muscle on the lateral or ventrolateral right abdominal wall approximately 2 to 3 cm caudal to the last rib. Incisions cranial to the last rib will penetrate the diaphragm and result in pneumothorax, particularly if the incision is made in the dorsal half of the abdominal wall. Before incising the body wall, it is important to manually appose the stomach to the body wall to estimate the appropriate anatomic site of the incision. Attention to the position dorsal to ventral on the body wall is essential because it is natural instinct to place the incision where it will be easy to visualize and suture instead of in the appropriate anatomic location. Removal of the Balfour retractor and retraction and eversion of the body wall with towel clamps aids in visualization and appropriate incision placement. Gastric and abdominal wall incisions are apposed using 2-0 monofilament absorbable suture in a simple continuous suture pattern beginning with the craniodorsal edges of the incision (Figure 91-6).

Figure 91-6 Incisional gastropexy. A, The body wall is retracted after the Balfour retractor is removed to facilitate visualization. B, After determining the appropriate position based on the normal anatomic location of the stomach, an incision is made through the transverse abdominus muscle caudal to the last rib. A second incision is made through the serosa and muscular layers of the stomach on the ventral surface of the pyloric antrum. The mucosa will bulge from the incision. C, The incisions in the body wall and stomach are apposed using two continuous suture lines with the most dorsal incision closed first to facilitate visualization. D, Completion of the second suture line. (Photographs from Watson K, Tobias KM. Incisional gastropexy. Vet Med 101:213–218, 2006. Drawings from Fossum T, editor: Small animal surgery, ed 3, St Louis, 2002, Mosby/Elsevier.)

The technique for incisional gastropexy for treatment of hiatal hernia is similar in all respects except that it is performed on the left side of the abdomen. The incision through the seromuscular layer of the fundus corresponds with an incision through the peritoneum and transverse abdominis muscle on the left side of the abdominal wall caudal to the last rib. Care should be taken when making this gastric incision because the gastric wall is not as thick in this area as in the antrum, and penetration of the gastric mucosa is undesirable.

Belt-Loop Gastropexy

Belt-loop gastropexy is a variation on incisional gastropexy. With the belt-loop technique, a seromuscular flap is elevated from the pyloric antrum and passed through a tunnel created between two parallel incisions in the abdominal wall.¹⁷⁷ The seromuscular gastric flap is based along the greater curvature of the stomach and incorporates branches of the gastroepiploic artery in its origin (Figure 91-7). The flap is created by making two parallel incisions approximately 4 cm long and 3 cm apart and connecting these incisions at their most cranial aspect. The resultant seromuscular flap is undermined from the mucosal layer below. Next, two 5-cm–long abdominal wall incisions that penetrate the peritoneum and transverse abdominis muscle are made approximately 3 cm apart. Muscle between the two incisions is undermined, creating a tunnel through which the seromuscular gastric flap is passed. The gastric flap is passed through the tunnel by first bringing the stomach close to the body wall to decrease tension applied to the flap as it is passed and then using a stay suture placed in the free end of the flap to direct the flap through the tunnel. The flap is sutured back to the site from which it was elevated using a simple interrupted or continuous pattern of 2-0 or 3-0 absorbable monofilament.

Figure 91-7 Belt-loop gastropexy. A, A seromuscular flap is raised, originating from the pyloric antrum and incorporating a blood supply in the base of the flap. B, Parallel transverse incisions are made in the transverse abdominus muscle. C, The seromuscular flap is advanced through the “belt loop” created in the abdominal wall. The stomach should be held in close approximation to the body wall as this is accomplished to minimize trauma to the flap. The flap is then sutured back into the area it originated from on the stomach. (Illustrations from Fossum T, editor: Small animal surgery, ed 3, St Louis, 2007, Mosby/Elsevier. Photographs courtesy Dr. Dan Degner.)

Circumcostal Gastropexy

The circumcostal gastropexy technique, originally described in 1982,⁴⁹ has been successfully performed in experimental cases and with clinical cases of gastric dilatation and volvulus. Modifications of the original technique have been described.^34,136 A seromuscular flap is raised from the pyloric antrum similar to the belt-loop gastropexy technique (Figure 91-8). The seromuscular flap may be double or single hinged. When a single-hinged flap is used, it is based from the lesser curvature of the stomach and undermined below the level of the muscularis layer, taking care not to penetrate the gastric lumen. A 5- to 6-cm incision is made directly over the eleventh or twelfth rib at the level of the costochondral junction. A plane of blunt dissection is then established circumferentially in close association with the rib. Care must be taken to avoid creation of pneumothorax or fracture of the rib; both are reported complications of this procedure.^102,183 The seromuscular gastric flap is then passed cranial to caudal through the tunnel surrounding the rib; stay sutures placed in the leading edge of the flap facilitate passage around the rib. The seromuscular flap is sutured back to its origin using 2-0 or 3-0 absorbable suture material.

Figure 91-8 Circumcostal gastropexy. A, Make a single- or double-layered hinged seromuscular flap in the pyloric antrum. B, Make an incision over the eleventh or twelfth rib at the level of the costochondral junction. C, Form a tunnel under the rib using a Carmalt clamp or hemostat. D, Pass the gastric antral flap craniodorsal under the rib and suture it to the original gastric margin or to the other flap. (From Fossum T, editor: Small animal surgery, ed 3, St Louis, 2007, Mosby/Elsevier.)

Gastrocolopexy

Creation of a suture line between the greater curvature of the stomach and the transverse colon has been described to prevent recurrence of gastric dilatation and volvulus.27,42 Gastrocolopexy as reported does not include incision into the seromuscular layer of either the stomach or the colon; instead, the surfaces are scarified and then apposed with nonabsorbable sutures. Whether a permanent adhesion is created is unknown.

Incorporating Gastropexy

An incorporating gastropexy is performed by including approximately 5 cm of gastric wall near the pyloric antrum with the cranial portion of the linea alba closure during apposition of a ventral midline abdominal incision. Abdominal wall closure and gastric incorporation are performed with absorbable suture material.¹¹⁶ As described originally, no incision is made into the seromuscular layer of the stomach. The strength of adhesion formed using this technique has not been evaluated experimentally. Incorporating gastropexy is easy and quick to perform; if subsequent abdominal exploration is required, however, inadvertent penetration of the stomach while entering the abdominal cavity could occur.

Minimally Invasive Prophylactic Gastropexy Techniques

Grid Approach.: Prophylactic right-sided gastropexy may be achieved through a minilaparotomy.¹⁶⁰ This technique is performed by creating a 6-cm vertical skin incision immediately caudal and ventral to the thirteenth rib. An opening is then created through the external abdominal oblique, internal abdominal oblique, and transversus abdominus muscles by blunt dissection along the direction of the muscle fibers. The peritoneal surface is penetrated bluntly, and the gastric antrum is retracted into the surgical field with Babcock intestinal forceps. Visualization of landmarks specific to the stomach, such as pylorus, omental attachments, and gastric vasculature, is critical to ensure that the appropriate portion of the gastrointestinal tract is being anchored to the body wall. After placing stay sutures in the pyloric antrum, a 3-cm longitudinal incision is made through the gastric serosal and muscular layers. Edges of the gastric incision are apposed to the cut edges of the transversus abdominus fascia and muscle with a continuous suture pattern of absorbable monofilament. The more superficial muscle layers are closed individually over the gastropexy site, again with continuous suture patterns.

Endoscopically Assisted Gastropexy.: Endoscopically assisted prophylactic gastropexy has been reported in dogs and is achieved with the dog in left oblique recumbency.40,41 A gastroscope is passed into the stomach, and the stomach is insufflated. While the pyloric antrum is viewed through the gastroscope, the right abdominal wall is palpated to identify the appropriate anatomic location for gastropexy. The stomach is stabilized with stay sutures: number 2 polypropylene suture on a cutting needle (needle length, 76 mm) is passed from the right external body wall into the gastric lumen immediately caudal to the thirteenth rib and back out through the skin, incorporating a minimum of 2 cm of gastric tissue. The needle is viewed endoscopically as it passes in and out of the stomach lumen to ensure that it is engaging the pyloric antrum, and the resulting stay suture is secured with a hemostat. A second stay suture is similarly placed 5 cm aborally from the first suture. An incision is then made through the body wall between the two stay sutures to the level of the stomach. Unlike the grid dissection, muscle layers are transected, not bluntly dissected. Visualization is assisted through placement of Gelpi retractors, and a longitudinal incision is made through the gastric serosa and muscular layers. The edges of the gastric incision are apposed to cut edges of the transversus abdominus muscles, as described previously for the grid gastropexy procedure. The muscle layers, subcutaneous tissues, and skin are closed routinely, and the stay sutures are removed.

Laparoscopic Gastropexy.: Laparoscopic and laparoscopic-assisted gastropexy have been reported for prevention of gastric dilatation and volvulus in dogs.80,113,144–146 Laparoscopic visualization ensures appropriate stomach positioning. Mayhew et al.¹¹³ reported two techniques for total laparoscopic gastropexy. Three portals are used to achieve either technique, with all ports placed on the ventral midline. The first port is placed approximately 1 cm caudal to the umbilicus. An instrument port is placed 3 to 4 cm caudal to the xiphoid, and the final port is positioned midway between the first two portals and directly medial to the proposed gastropexy site. After all portals have been established, the camera is introduced through the middle portal. A stay suture is introduced through the body wall, grasped intracorporally, inserted through the pyloric antrum, and returned through the body wall adjacent to the entry site of the needle. This stay suture is used to hold the antrum in apposition with the body wall. An incision is made into the transversus abdominus muscle with endoscopic Metzenbaum scissors at the site of the proposed gastropexy. The serosal and muscular layers of the stomach are then incised in the same orientation as the incision in the body wall. The gastric wall and body wall incisions are opposed with either a suture–assist device and laparoscopic needle holders or via intracorporeal hand suturing. An important technical consideration in both of these intracorporeal procedures is the need to initially introduce adequate lengths of suture to complete the suture lines and the need for the surgeon to have training and experience in either procedure.

Stapled gastropexy can also be performed laparoscopically.⁸⁰ Using laparoscopic instruments, Hardie et al.⁸⁰ created subserosal tunnels in the pyloric antrum and right body wall. A laparoscopic stapler was inserted in the tunnels and used to appose, staple together, and divide the pyloric and body wall tissues, creating a permanent gastropexy with two staple lines.

With the laparoscopic-assisted gastropexy technique, the laparoscope is used to identify the portion of the stomach to be incorporated into the pexy and to bring it to a body wall incision, permitting a smaller exposure than the grid technique.145,146 A camera port is established on the midline 2 to 3 cm caudal to the umbilicus. A second working port is established lateral to the right margin of the rectus abdominus muscle and 3 cm caudal to the last rib (Figure 91-9). Laparoscopic Babcock forceps are introduced through the right port and used to grasp the pyloric antrum and retract it to a position adjacent to the body wall. Forceps and associated cannula are withdrawn while maintaining traction on the pyloric antrum, exteriorizing the antrum through the body wall opening created for the port. The incision in the abdominal musculature is extended to approximately 4 cm in length, and stay sutures are placed in the pyloric antrum. Gastric serosal and muscular layers are incised longitudinally, and cut edges are apposed to the cut edges of the transversus abdominus muscle. The stay sutures are removed, and the muscle layers, subcutaneous tissue, and skin are closed routinely.

Figure 91-9 Laparoscopic-assisted gastropexy. A, The antrum is grasped midway between the greater and lesser curvatures at approximately 5 to 7 cm orally from the pylorus. The laparoscopic Babcock forceps is placed perpendicular to the long axis of the stomach. The Babcock forceps, its right-side trocar cannula, and the antrum are exposed through the lengthened cannula’s incision. B, Cruciate retraction sutures are placed approximately 4 cm apart at the ends of a planned seromuscular incision. The seromuscular layer is incised (3.5 to 4.0 cm) down to the gastric mucosa, and a dissection plan is developed between these two layers in both directions from the initial incision. C, The seromuscular layer is sutured to the peritoneum and transversus abdominis. The oblique muscles are closed as an independent layer over the gastropexy. GM, gastric mucosa; SM, seromuscular layer of the stomach; TA, transversus abdominis muscle. (From Rawlings CA, et al: A rapid and strong laparoscopic-assisted gastropexy in dogs. Am J Vet Res 62:871, 2001.)

Pyloromyotomy and Pyloroplasty

Pyloric surgical techniques are focused on removing outflow obstruction and normalizing gastric outflow. Several techniques have been described, including the Fredet-Ramstedt pyloromyotomy, Heineke-Mikulicz pyloroplasty, and Y–U pyloroplasty.

Fredet-Ramstedt Pyloromyotomy

Fredet-Ramstedt pyloromyotomy is performed by making a longitudinal incision through serosa and muscularis of the ventral pylorus. The incision should be centered over the pylorus and extend 1 to 2 cm orad and aborad. When performed correctly, the gastric mucosa is not penetrated; however, its submucosal surface should protrude through the incision. This partial-thickness incision is left open, permitting enlargement of the pylorus in cases in which restriction is limited to the serosa or muscularis (Figure 91-10). Because pyloromyotomy does not allow visualization of the gastric mucosa, relieve restrictions associated with mucosal or submucosal disease, or provide a means for full-thickness biopsy of the stomach wall, its use is limited.

Figure 91-10 Pyloromyotomy. A, Myotomy is considered for pyloric widening if pyloric musculature is thickened but mucosa and submucosa are normal. B, A longitudinal incision is made through the muscular layer, and all muscular fibers are transected. C, When properly performed, mucosa and submucosa bulge through the incision. (Modified from Birchard SJ, editor: Saunders manual of small animal practice, ed 3, Philadelphia, 2006, Saunders/Elsevier.)

Heineke-Mikulicz Pyloroplasty

Heineke-Mikulicz pyloroplasty is similar to pyloromyotomy in that a longitudinal incision is made in the ventral surface of the pylorus; however, the incision is created full thickness and then closed transversely (Figure 91-11). Stay sutures can be placed in the middle of either side of the longitudinal incision and retracted to provide apposition for the transverse closure; alternatively, stay sutures can be placed at each end of the incision and pulled together to provide the same effect. Closure is achieved with 2-0 or 3-0 absorbable monofilament suture material in an appositional pattern. Heineke-Mikulicz pyloroplasty permits full-thickness gastric wall biopsy and resection of small masses or thickened tissues along the incision.

Figure 91-11 Pyloroplasty. A, A full-thickness longitudinal incision, centered over the pylorus and extending 1 to 2 cm orad and aborad, is made. B, The pyloric area is inspected visually, and tissue is taken for histopathologic examination. C, Stay sutures placed at the midpoint along each side of the incision are retracted. The incision is closed transversely using an appositional closure pattern. D, Finished closure of the pyloroplasty. (Copyright © 1974, 1980, 1988, 2001 United States Surgical. All rights reserved. Reprinted with permission of United States Surgical, a division of Tyco Healthcare Group LP.)

Conventional and laparoscopic pyloromyotomy and pyloroplasty have been described.11,126,151 In one study, gastric emptying of solids was significantly enhanced in dogs undergoing pyloroplasty, but pyloromyotomy did not significantly change gastric emptying relative to preoperative values.¹⁵¹ Other studies have reported no change to slowed gastric emptying after these pyloric procedures.¹²⁶

Y–U Advancement Pyloroplasty

Y–U advancement pyloroplasty increases pyloric outflow tract diameter by advancing a portion of the pyloric antrum into the region of the pyloric sphincter. A Y-shaped full-thickness incision is centered over the pylorus. The incision for the body (or main stem) of the Y is made through the antimesenteric border of the duodenum, and the incisions for the arms of the Y extend into the pyloric antrum (Figure 91-12). The arms of the Y should curve slightly to form a U-shaped flap instead of a sharp V to maximize vascular supply to the enclosed tissue. Visualization of the outflow tract, mucosal resection, and full-thickness biopsy may be performed before closure. The U-shaped flap is then advanced forward using stay sutures at its tip and sutured into the most aboral portion of the incision at the duodenum using 2-0 absorbable monofilament suture material in an appositional pattern.

Figure 91-12 Y–U pyloroplasty. A, The pylorus is identified and isolated using moistened laparotomy sponges. B, The full-thickness Y incision is made. The body of the Y begins 1 to 2 cm aborad from the pylorus and extends through the pylorus, and the arms of the Y extend onto the pyloric antrum. C, After removal of tissue for biopsy, the curved center of the U is advanced into the farthest extent of the original incision and sutured into place using an appositional pattern. (Drawings from Slatter DH, editor: Textbook of small animal surgery, ed 3, St Louis, 2003, Saunders/Elsevier. Photos courtesy Karen Cornell.)

Gastroduodenal Anastomosis

Pylorectomy with gastroduodenal anastomosis (Billroth I) is performed in animals with pyloric outflow obstruction that cannot be treated with routine pyloroplasty techniques. Indications include neoplasia confined to the pyloric region, ulceration of the outflow tract, and some cases of pyloric hypertrophy. When neoplasia is suspected, a 1- to 2-cm margin of normal tissue should be removed with the abnormal tissue.

Pyloric resection is technically more challenging than other techniques involving the pylorus and requires detailed knowledge of regional anatomy. The bile duct, pancreatic ducts, and vascular supply to the stomach and duodenum must be identified before any surgical excision (see Figure 91-1). The bile duct is best identified by manual expression of the gallbladder: bile can be detected as it descends through and dilates the bile duct as it approaches the duodenum.

Stay sutures are placed in the duodenum and stomach to facilitate retraction and minimize potential leakage. Atraumatic tissue forceps are used proximal and distal to the site of resection to minimize leakage of gastrointestinal contents. The hepatogastric ligament can be transected to facilitate caudoventral retraction of the pylorus; however, care should be taken to avoid bile duct transection deep and lateral to this area. Inadvertent transection of the bile duct has been reported during this procedure.¹⁷² A minimum of 5 to 10 mm of healthy tissue should be maintained between the duodenal level of excision and the opening of the bile duct to prevent inadvertent damage or obstruction.¹⁷² Branches of the right gastric and right gastroepiploic blood vessels supplying the area to be resected are ligated and transected. Omental and mesenteric attachments are ligated and divided. After making sure the area is packed off from the rest of the abdomen with laparotomy sponges, the pylorus is removed with Metzenbaum scissors or a scalpel. If a significant discrepancy in lumen diameter is created by this resection, the surgeon may choose to incise the antimesenteric border of the duodenum to increase its diameter or close a portion of the gastric antrum to narrow gastric diameter to facilitate anastomosis (Figure 91-13). End-to-end anastomosis of the stomach and duodenum is performed with a one- or two-layer appositional pattern using a simple interrupted or simple continuous pattern of 2-0 or 3-0 absorbable monofilament suture. No difference in leakage was reported when one- and two-layer closures were compared.¹⁷²