Clinical Signs/Physical Exam

Surgical management of GI FBs varies depending on the type and location of the FB. Sharp FBs, such as straight pins, safety pins, bones, nails, or glass, will usually pass through the GI tract without creating intestinal perforation. Rubber balls, cellophane, or corncobs tend to pass slower or not at all and are more likely to cause complete mechanical obstruction requiring emergency laparotomy.

Gastric FBs can be seen in any age animal but are most common in puppies or kittens because of their indiscriminate eating habits. Common gastric FBs seen in dogs include bones, balls, corn cobs, rope toys, and cellophane wrappers. Linear FBs, such as yarn, tinsel, or string, are more common in cats.

Clinical signs associated with gastric FBs are highly variable. If the structure moves freely about the gastric lumen, sporadic vomiting, inappetence, or weight loss is commonly reported. Occasionally animals are completely asymptomatic. However, if the FB lodges in the pylorus, acute profuse projectile vomiting results and rapid dehydration is often noted. Gastric fluids rich in K⁺, Na⁺, H⁺, and Cl⁻ are lost, sometimes resulting in a hypokalemic hypochloremic metabolic alkalosis.

Animals may be categorized as having either an incomplete (partial) or complete obstruction. Patients with incomplete obstructions caused by intraluminal linear FBs or neoplasia usually present with sporadic vomiting, anorexia, and weight loss, which often progresses in severity over days or weeks. Conversely, complete obstructions caused by FBs, strangulated intestines, acute intussusceptions, or intestinal volvulus usually cause acute bowel distention and more severe clinical signs than in those with partial obstructions. The presence and character of feces is sometimes important in establishing the type of obstruction. Scant stools often indicate an incomplete obstruction is present. Blood or melena may indicate intestinal strangulation, ulceration, neoplasia, or parasitism. Diarrhea, tenesmus, and/or scant amounts of blood‐stained feces are also often seen in patients with intussusception.

Animals may also be categorized as having high (proximal) versus low (distal) obstruction. With proximal (pylorus or duodenum) and complete obstructions, vomiting is often projectile, and the patient has more acute and severe clinical signs with rapid electrolyte changes and dehydration. Duodenal obstruction prevents large quantities of salivary, gastric, pancreatic, or duodenal secretions from contacting the jejunal and ileal mucosal surfaces for reabsorption, resulting in rapid dehydration. The major cause of mortality from upper small intestinal obstruction is severe hypovolemia and electrolyte disturbances. With distal jejunum, ileum, ileocecal junction, and incomplete intestinal obstruction, clinical signs may be more chronic and vague with intermittent anorexia, lethargy, diarrhea, and occasional vomiting. More than half of all the fluids and electrolytes are added in the stomach and duodenum, and the majority of these are reabsorbed by the jejunum and ileum. Obstruction of the distal small intestine spares most of this absorptive surface. Signs with distal obstructions are associated with maldigestion and malabsorption of nutrients.

Animals may also be categorized as having a simple mechanical versus a strangulated (ischemic) obstruction. Distinguishing between simple mechanical and strangulated (ischemic) bowel obstruction is critical because the latter condition requires early and rapid surgical intervention. Mechanical obstructions can be luminal (FBs), intramural (neoplasia), or extramural (adhesions). With simple mechanical luminal obstruction, blood flow to the distended bowel is not completely obliterated, but increased bowel wall tension may cause both histological and physiologic changes. Strangulated obstruction may occur from intraluminal obstruction with local pressure necrosis. More commonly, strangulation obstruction occurs secondarily to mesenteric vascular disruption caused by intestinal volvulus, intussusception, or a strangulated hernia.

Diagnostics

Most importantly, the clinician should consider history and physical exam findings when considering whether a patient needs emergent surgery or not. Abdominal palpation is of utmost importance to evaluate for pain and tenderness in the abdomen. In some cases, foreign material may be palpated on examination. A rectal exam should also be included as part of a thorough physical exam.

Diagnosis of gastric FBs is often made based on plain abdominal radiographs. Focal gas dilation of the small intestines is consistent with intestinal FB obstruction with an 80% greater chance of obstruction if the maximal SI diameter is >2x compared to the height of L5 at the mid‐centrum in dogs.^11,12 In cats, similar ratio measurements are taken with maximum small intestinal diameters compared to the height of the cranial end plate of the second lumber vertebra (L2) on a lateral view radiograph, and cats with ratios <2.0 are more likely to have non‐obstructed intestines.¹³ In cats, the maximal small intestinal diameters should not exceed 12 mm.

Metal objects are easily identifiable, and objects such as bones, racket balls, or corn cobs often can be seen without contrast studies. Radiolucent objects causing an obstruction may be more challenging to diagnose. In these cases, barium sulfate may be administered to help delineate the object. Caution should be taken with barium administration, as it should not be used if a GI perforation is suspected or when there is concern for aspiration pneumonia with continuous regurgitation. If free gas is visualized in the abdomen on radiographs, this is an indication of a possible GI perforation, and an abdominal explore is recommended. Linear FBs pass down into the small intestine resulting in “pleating” of the small bowel, although the proximal anchor point is usually located in the stomach (dogs > cats) or under the tongue (cats > dogs).^14–16 This often appears in the right cranial quadrant of the abdomen in the ventral–dorsal (VD) radiograph or cranioventral portion of the abdomen in the lateral view.

Ultrasonography is another diagnostic tool often used to help diagnose GI FBs and is preferred over radiographs by some clinicians. An advantage of ultrasound is that if free fluid is present in the abdomen, the fluid may be aspirated via ultrasound guidance to assess for SP. With the use of radiographs and ultrasound, barium is not commonly used. In recent years, endoscopes have become invaluable in diagnosing gastric FBs, ulcerations, or neoplasms, which were not apparent radiographically.

Treatment Options

In some cases, medical or conservative management may be pursued. This is only an option if the material is small enough to pass through the GI tract or if there is an acute presentation. Rehydration with high rates of IV fluids is a key component of medical management and may help to move the obstruction through the GI tract once the bowel is rehydrated. Prokinetics, such as cisapride or metoclopramide, are contraindicated for use with GI FB obstructions, as these medications will increase the likelihood of GI perforation. Abdominal radiographs are repeated every 8–12 hours to monitor for movement of the foreign material and monitor for progressive gas distention in the bowel. If the patient has progressive vomiting or becomes more painful on abdominal palpation during this time, surgery should be recommended. A potential concern, which owners should be aware of with medical management, is that the foreign material may continue to stay lodged in place, and the bowel may perforate from continued pressure necrosis. Medical management is contraindicated in the case of linear FB obstructions and SP.

Endoscopic FB removal is also an option for gastric FBs in the case of smaller FBs or less numerous FBs. Endoscopes are frequently invaluable for removing FBs, such as silk stockings or rags, which may be easily grasped with forceps. Endoscopy is not ideal with numerous FBs, larger FBs, or FBs that may be linear or lodged in part of the small intestines. Rubber balls or bones cannot usually be removed with endoscopy.

Careful client consultation is important when managing gastric FBs. Surprisingly, sharp FBs, such as nails, straight pins, and bones, will usually pass spontaneously through the entire intestinal tract without causing perforation. The animal should be fed a high‐fiber diet and carefully monitored for the onset of vomiting, abdominal tenderness, or fever. Radiographs should be repeated daily to ensure that aboral passage is occurring. Complete passage usually takes three to four days. With larger FBs, the owner must be made aware that at any time, complete intestinal obstruction may occur that necessitating surgery.

If the FB has a relatively smooth surface and appears as though it is too large to pass distally, induction of vomiting may be considered. Dogs may be induced to vomit with apomorphine or cats with xylazine. Induced vomiting for attempted gastric evacuation of a sharp FB should be approached with great caution because of the danger of the FB lodging in the esophagus. For this reason, some veterinarians will feed cotton prior to inducing emesis. The author’s preference is to not induce vomiting with foreign material due to the concern for the material lodging in the esophagus.

The treatment most commonly used for recovering gastric FBs if spontaneous passage does not occur is gastrotomy. With linear FBs like strings or abrasive FBs like corn cobs, exploration and gastrotomy should be recommended immediately because they rarely pass without causing obstruction or perforation. The prognosis with a gastric FB is considered very good if there is no evidence of perforation.

Preoperative Considerations

The patient should be optimized for anesthesia and surgery. Prolonged stabilization may be limited if in an emergency setting. Ideally, the patient would be physiologically stable and would be rehydrated, and any acid‐base or electrolyte abnormalities would be addressed prior to surgery. A minimum database with a complete blood cell count and diagnostic panel should be performed, along with a urinalysis and coagulation panel depending on the patient. A venous blood gas may also be performed to evaluate for electrolytes and lactate. Electrolyte loss is dependent upon the level of obstruction. With obstructions proximally, gastric fluids rich in potassium (K⁺), sodium (Na⁺), hydrogen (H⁻), and chloride (Cl⁻) ions are vomited, and a hypochloremic, hypokalemic, hyponatremic metabolic alkalosis with dehydration may result. Obstructions distal to the bile and pancreatic ducts result in loss of highly alkaline (HCO₃) duodenal, pancreatic, and biliary secretions, and metabolic acidosis usually results from loss of these bicarbonate‐rich duodenal contents.

Prophylactic Antimicrobial Use

Prophylactic antibiotics are indicated to reduce the incidence of surgical site infections (SSIs) and are indicated in surgeries with prolonged surgery and anesthesia time and with a risk of contamination, among other factors. In the absence of GI perforation or SP, GI surgery is considered a clean‐contaminated procedure with the risk of an SSI of less than 5%. The GI tract contains both Gram‐positive (>upper GI) and Gram‐negative (>lower GI) organisms. In these cases, the author prefers the use of cefoxitin, a second‐generation cephalosporin that covers more anaerobes and Gram‐negative bacteria found in the GI tract, in addition to Gram‐positive bacteria.

Timing of antimicrobial administration is one of the most important factors when evaluating perioperative antimicrobial prophylaxis. Cephalosporins are time‐dependent and well‐tolerated, achieve targeted serum and tissue concentrations, are broad‐spectrum, have a low incidence of adverse effects, are low cost, and are the preferred prophylactic antimicrobial for most surgical procedures. Dosing regimen should ensure adequate bactericidal drug concentrations are achieved and maintained at the site of invasion before potential contamination and until shortly after completion of surgery. Cefoxitin, similar to cefazolin, should be given at 22 mg/kg IV at induction of general anesthesia (complete administration 30–60 minutes before incision) and repeated every 90 minutes throughout the surgery or up to 12 hours after surgery.

Extended postoperative antibiotics are not indicated unless there is gross GI spillage or the presence of SP causing the surgery to be contaminated, in which case a more broad‐spectrum antibiotic, like ampicillin sulbactam (Unasyn), would be preferred with ultimate selection based on culture/susceptibility results.¹⁷ Postoperative antibiotics are not indicated in cases without contamination or SP, as extended use of antibiotics does not prevent infection, and it also contributes to increased antimicrobial resistance.¹⁸ In addition, extended antibiotic use may mask clinical signs of dehiscence, which may delay treatment of SP and cause a more guarded prognosis.

Stomach

The stomach is divided into four parts: the cardia, fundus, body, and pyloric portions. The cardia is located on the left side where the esophagus joins the stomach. The point where the intraabdominal esophagus blends into the stomach on the left side is termed the cardia. The fundus is an expansive sac that is located dorsal and to the left of the cardia. The body of the stomach is the largest part of the stomach and is set between the fundus and the pylorus, which is located on the right side and joins the stomach to the duodenum and is made up of the antrum and pyloric muscular sphincter. The greater curvature of the stomach is convex and is located on the more caudal aspect of the stomach, whereas the lesser curvature is concave and located at the more cranial aspect of the stomach between the dorsal and ventral aspects. Both the greater and lesser curvatures are where the greater and lesser omentum attach.

The celiac artery is a direct branch from the aorta and supplies the arterial blood flow to the stomach. From the celiac artery, there are three branches (splenic, hepatic, and left gastric arteries), each of which provides blood flow to the stomach. The stomach has an excellent redundant blood supply and subsequently great healing. The portal vein provides venous drainage of the stomach via the splenic vein and gastroduodenal vein.

The GI tract is made up of four layers, listed from the internal surface to the external, and consists of the mucosa, submucosa, muscularis, and serosa. The submucosa is the critical holding layer of the GI tract when performing GI surgery.

Gastrotomy Techniques

For any GI surgery, a full abdominal explore should be performed to evaluate the entire GI tract and abdomen, which entails a ventral midline abdominal incision that extends from the xiphoid and caudal to the umbilicus (Figure 22.1). A Balfour retractor (Figure 22.1) may be used as a self‐retraining retractor to aid in visualization within the abdomen after the falciform ligament has been removed (Video 22.1). It is important to minimize the risk and consequences of gastric content spillage, and there are a number of important steps to aid in this process. First, separate clean instruments from clean‐contaminated instruments. The same instruments used to create the gastrotomy or handle the tissue while the lumen is open should not be used to close the abdomen. Either using clean instruments separated before the procedure or using a new “closing” pack that is opened at the end of the procedure is ideal to reduce contamination. Second, place stay sutures in the stomach to elevate the stomach and avoid spillage (Figure 22.2, Video 22.2). This entails taking large, full‐thickness bites using 2‐0 or 3‐0 monofilament suture on a taper needle between the lesser and greater curvatures of the stomach on either side of where the intended gastrotomy site will be and elevating the stomach with hemostatic forceps holding the stay sutures. Third, thoroughly pack off the abdomen around the proposed surgical site with moist laparotomy sponges for inadvertent leakage (Figure 22.2) and have suction ready and available with a Poole tip. Lastly, remove contaminated instruments from the surgical field, change surgical gloves when closing, and lavage the abdomen with warm sterile saline. Abdominal lavage should occur with warm sterile saline (98.6–102.2 °F), which will not only aid in removing potential contaminates, but also warm the patient.

The gastrotomy incision should be made on the ventral aspect of the stomach and equidistant between the greater and lesser curvatures in a region with minimal vasculature. The size and exact location of the incision is dependent on the size and location of the foreign material. After the stomach has been packed off and stay sutures elevated and suction prepared, a stab incision is made into the stomach with a #11 blade and extended to the desired length with Metzenbaum scissors (Video 22.3). The area should be packed off with moist laparotomy sponges, and the author places a green towel just caudal to the stomach, so the foreign material can be placed on the towel once removed, along with the dirty instruments to be removed from the surgical field (Video 22.4). There are several techniques to close the stomach after a gastrotomy is performed. Closure may be performed with a single‐layer appositional pattern making sure to engage the submucosa, the holding layer, in the closure. The author prefers a double‐layer closure with the first layer (Figure 22.3, Video 22.5) being appositional and engaging both the mucosa and submucosa (inner layers of the stomach), and the second layer (Figure 22.4, Video 22.6) being an inverting pattern and engaging the muscularis and serosa (outer two layers of the stomach). Inverting patterns consist of the Cushing (author’s preference), Connell, and Lembert patterns. Recommended suture material is a monofilament, synthetic absorbable suture, such as polydioxanone (PDS^®; PDS II, Johnson & Johnson Medical, New Brunswick, NJ), glycomer 631 (Biosyn) (Biosyn^™, Medtronic, Minneapolis, MN), or poliglecaprone 25 (Monocryl) (Monocryl^®, Johnson & Johnson Medical, New Brunswick, NJ) on a taper‐point needle. The author prefers 3‐0 suture for the stomach unless the patient is a small/toy breed dog or cat, in which case 4‐0 suture may be preferred pending stomach thickness. Stapling equipment, such as the thoracoabdominal (TA) (TA^™ Single Use Reloadable Staplers, Medtronic, Minneapolis, MN) stapler or gastrointestinal anastomosis (GIA) (GIA^™ Single Use Reloadable Staplers, Medtronic, Minneapolis, MN) stapler may be used with partial gastrectomies, which may be indicated with a GDV, and gastric necrosis and will be discussed later with intestinal R&A.

Small Intestine

The small intestine begins with the duodenum, which makes up approximately 10% of the total small intestinal length, begins at the pylorus, and runs caudally in a dorsolateral direction to the right of the midline as the descending duodenum. The mesoduodenum becomes shorter, and at the level of the fifth lumbar vertebra, the duodenum turns medially (caudal duodenal flexure) to the left of the midline in close proximity to the root of the mesentery. The ascending duodenum is closely adhered to the mesocolon by the triangle‐shaped duodenocolic ligament. Immediately cranial and to the left of the mesenteric root, the transition to jejunum begins. Unlike the relatively fixed duodenum with its short mesoduodenum and duodenocolic ligament, the jejunum and ileum are loosely coiled and freely moveable because they are suspended from a long mesentery. The jejunum comprises the bulk of the small intestine. A gross division between the jejunum and ileum is difficult to determine, but the terminal contracted portion of the ileum is characterized by prominent antimesenteric vessels. The ileum is attached to the cecum by the ileocecal fold and lies principally to the right of the midline.

The duodenum is supplied by the cranial pancreaticoduodenal off the celiac artery and the caudal pancreaticoduodenal off the cranial mesenteric artery. The jejunum is supplied by several jejunal arteries, which arise from the cranial mesenteric. The ileum is supplied by the ileocolic artery which arises from the cranial mesenteric, both on its mesenteric and antimesenteric surface. The four tissue layers of the intestine from external to internal include serosa, muscularis, submucosa, and mucosa. The muscular coat consists of a relatively thick outer longitudinal layer and a thinner inner circular layer. At the junction of the small and large intestine, this circular muscular layer is grossly thickened becoming the ileocolic sphincter. The submucosa contains the main vascular supply to the bowel wall, known as the submucosal plexus. It is also rich in collagen and is the layer of greatest suture‐holding capacity.

Enterotomy Techniques

Similar to a gastrotomy, a full ventral midline abdominal incision should be created with the falciform ligament removed, and a full abdominal explore should be performed (Figure 22.1). The entire GI tract should be explored and palpated for irregularities and foreign material prior to any surgical procedure. Once the foreign material is located, the segment of intestines should be assessed. If the foreign material is located in the duodenum, the author recommends attempting to milk the foreign material orad to the stomach to perform a gastrotomy. If the material cannot be milked to the stomach, the surgeon may attempt to milk the foreign material to the jejunum to perform an enterotomy, or perhaps milk to the colon where it will eventually be defecated. If the material is unable to be milked in either direction or excess trauma is being caused to the tissue from manipulation, a duodenotomy should be performed. Foreign material located in the colon should be able to pass on its own, and a colotomy is not recommended. Once the surgeon has determined where the surgical procedure will occur, the segment of intestine should be packed off with moist laparotomy sponges to prevent contamination.

If the distended segment of intestine is viable, an enterotomy is made. If the tissue has questionable viability, the GI obstruction should first be removed and the intestine assessed for viability prior to determining if a resection needs to be performed. After milking intestinal contents 10 cm to either side of the FB and packing the intestine off from the abdominal cavity with moist laparotomy sponges, the selected bowel is held by the assistant’s fingers or with atraumatic Doyen intestinal forceps. A longitudinal incision is made in the antimesenteric border of the intestine in the viable tissue immediately distal or aborad to the FB. The incision is recommended in this distal location because the tissue is healthy and has not been traumatized by the FB passage, which is ideal for healing. The FB is gently delivered through the enterotomy incision, taking care not to tear the incisional margins.

Closure of the enterotomy incision is usually made in a longitudinal fashion. A variety of closure patterns are acceptable. Simple interrupted (Figure 22.5a) or simple continuous (Figure 22.5b) appositional patterns have sutures placed ~3 mm apart and ~3 mm from the cut edge, taking care to incorporate all layers of the intestinal wall. A modified Gambee pattern incorporates the serosa, muscularis, and submucosa but excludes the mucosa and is helpful in reducing mucosal eversion. If a simple continuous layer is performed, it is important to evaluate tension on the line and ensure the tissues are well‐apposed prior to tying the end knot (Video 22.7). As each loop is placed for a simple continuous line, a curved mosquito hemostat or the curved needle may be used to gently place each loop and invert any mucosa that may be everting from the enterotomy site (Figure 22.6, Video 22.8a–c). Single‐layer enterotomy closures are used because double‐layer closures may cause excessive compromise of the lumen diameter. Recommended suture material is a monofilament, synthetic absorbable suture, such as polydioxanone (PDS; PDS II, Johnson & Johnson Medical, New Brunswick, NJ), glycomer 631 (Biosyn) (Biosyn, Medtronic, Minneapolis, MN), or poliglecaprone 25 (Monocryl) (Monocryl, Johnson & Johnson Medical, New Brunswick, NJ) on a taper‐point needle with 3‐0, 4‐0, or 5‐0 suture. Chromic surgical gut breaks down rapidly in the stomach because of the acidic environment. Also, surgical gut is not a good choice of suture for use in the colon because of that tissue’s slow healing properties and the presence of collagenase, which may speed tensile strength loss of the suture. Prior to closure of the abdomen, the enterotomy site should be draped in omentum to aid in healing. The greater omentum may simply be draped over top of the surgery site (author’s preference) (Video 22.9a) or it may be tacked down over the surgery site with a few simple interrupted sutures (Video 22.9b).

Linear FBs caused by such items as fishing line, sewing yarn, or rope toys present a difficult surgical problem. The trailing end of string FBs often catches over the base of the tongue or in the stomach and acts as an anchor. Intestinal peristalsis moves the FB aborally resulting in bowel plication (Figure 22.7). The string often embeds itself in the mesenteric mucosa and can cause necrosis of the tissue and potentially cut through the wall on the mesenteric border, resulting in peritonitis (Figure 22.8). Linear FBs should be managed by initially identifying and releasing the anchor point. If wrapped around the tongue, the FB should be released prior to laparotomy. More commonly, a gastrotomy is necessary to free the foreign material from its gastropyloric anchor. Multiple enterotomies are then usually required to facilitate the complete removal of the FB. If too few enterotomies are made with too much traction placed on the string, the mesenteric border may be perforated in an area that is difficult to explore and suture. Occasionally, the string has cut through at several locations, and peritonitis is evident. Sometimes, in long‐standing cases, fibrosis has occurred around the FB so that even after its removal, the bowel retains its pleated conformation. In these cases, intestinal R&A may be necessary. Alternatively, the string can be removed by attaching it to a red rubber catheter and pushing it aborally to disengage it from the bowel wall. If successful, the string can sometimes be removed with a single enterotomy (Figure 22.9, Video 22.10a,b).

Assessing Tissue Viability

With complete obstruction, intestinal distention is often severe, and the distended loops of bowel take on a cyanotic appearance. Intestinal viability is best evaluated after (1) decompression of dilated loops of intestine and (2) removal of the FB. If intestinal wall ischemia and necrosis (Figure 22.10) are present, then R&A is performed immediately. However, in most cases of simple non‐strangulated obstruction, bowel viability is maintained, and the visual appearance of dark distended loops of bowel improves rapidly after removal of the obstruction.

Standard clinical subjective criteria for establishing intestinal viability are color (palor) (Figure 22.10), arterial pulsations (Video 22.11), thickness (palpation), and the presence of peristalsis, the four Ps. Of these parameters, experimental data has shown peristalsis to be the best and most dependable determinant of viability, although depending on the severity and chronicity of the obstruction, the intestines may have severe ileus. The “pinch test” should be performed on questionable bowel to determine if smooth muscle contraction and peristalsis can be initiated.

Intestinal Resection and Anastomosis

Intestinal R&A is a common procedure performed in small animal surgery in order to remove non‐viable or diseased intestines with a reported incidence of dehiscence between 3% and 28%.^7–10 Currently, anastomoses in small animals are commonly performed with either a traditional handsewn technique or surgical stapling device.

When the bowel is devitalized, R&A is necessary. The mesenteric vessels to the affected bowel are isolated and ligated between ligatures (Video 22.12). The arcuate vessels located along the mesenteric boundary are then ligated. Alternatively, a small handheld vessel sealing device that both cauterizes and cuts is an option and decreases surgical time (Video 22.12). At least 1.5 cm of viable tissue is included in the proximal and distal boundaries of the devitalized tissue to be removed. Intestinal contents are milked proximally and distally and held by an assistant’s fingers or with Doyen intestinal forceps to reduce the risk of spillage and contamination. Carmalt or other crushing clamps are placed in the area of intestine to be resected at an ~45° angle away from the long axis of the intestine (if lumen size needs to be increased at one end) or placed straight across the intestines (if there is no need to increase lumen size) (Figure 22.11a). A scalpel blade is used to excise the bowel along the outside of the crushing clamp (Video 22.13). The mesentery is then transected, and the excised bowel is removed from the surgical field. Up to 80% resection of the small intestine is consistent with quality of life. Resections greater than 75–80% may result in weight loss, cachexia, hypoproteinemia, and chronic diarrhea from short bowel syndrome.^19–21 The author also recommends avoiding resection of the ileocecocolic junction if possible, as resection will result in long‐term diarrhea.

Differences in luminal diameter sometimes make end‐to‐end anastomosis difficult. The lumen diameter of the smaller segment can be enlarged by (1) cutting the tissue back at a more acute angle as discussed above, (2) making a longitudinal incision along the antimesenteric border creating a spatulated opening, or (3) “fudging” the suture placement and placing the sutures farther apart on the larger lumen side and closer together on the smaller lumen size for cases of mild lumen disparity.

A variety of suture patterns have been used successfully for end‐to‐end intestinal anastomosis in the small animal patient; currently, approximating patterns are recommended. Properly performed approximating patterns (1) create an increased lumen diameter when compared to everting or inverting patterns, (2) give rapid and precise primary intestinal healing, and (3) minimize the potential for postoperative adhesion formation. Everting anastomosis is not recommended due to narrowing and stenosis of the lumen, as well as delayed mucosal healing, prolonged inflammatory response, and increased adhesion formation. Inverting anastomoses have the advantage of a more leak‐resistant serosa approximation but decreases the lumen diameter. Inflammation is more severe and the healing time of inverting patterns is delayed when compared to approximating techniques. Despite these disadvantages, inverting techniques may be considered for use in colonic R&A where the high bacterial content of feces makes leakage of the anastomosis extremely dangerous.

Simple interrupted approximating and simple continuous techniques are the most commonly used techniques for approximating end‐to‐end anastomosis. Eversion of mucosa from the bowel edge can be overcome by incising the mucosa with Metzenbaum scissors or by using a modified Gambee suture pattern. Regardless of the suture technique used, it is critical to secure the submucosa, which is the layer of greatest strength. The author recommends using a simple interrupted or simple continuous approximating anastomosis for handsewn R&A’s.

Simple interrupted and continuous patterns can be performed by taking bites through all layers of the intestinal wall, approximately 3 mm from the tissue edge and 3 mm apart, with extraluminal knots. By engaging slightly more serosa than mucosa, the everted mucosal edge is forced back into the lumen using either a curved mosquito hemostat or the end of a curved needle. To place a modified Gambee suture, the needle is inserted through the serosa 3 mm from the edge of the incision and is passed through the muscularis and submucosa. Resistance is felt as the needle penetrates the collagen‐dense submucosa. The needle is then directed toward the cut surface, so as to emerge at the junction of the submucosa and mucosa and pulled through. The needle is inserted into the second intestinal end at the mucosa–submucosa junction and passed through the submucosa, muscularis, and serosa in an arc to exit 3 mm from the cut surface. The suture is pulled just taut enough to appose tissues; if the suture is pulled too tightly, it will cut through the muscularis. The modified Gambee pattern works well to provide adequate submucosal apposition while inverting the mucosa. The Gambee suture depends on correct identification and inclusion of submucosa in each bite; inexperienced surgeons may be more likely to miss the submucosa, resulting in suboptimal leak pressures. A simple full‐thickness closure pattern is therefore the preferred choice for enteric closure among novice and infrequent surgeons. The amount of force applied to the knot is decided by the surgeon and is based on surgeon experience, stretch of the suture, and deformation of tissue. The rule of thumb is that tissues should be well‐apposed without being crushed. Poor apposition results in healing by second intention, which is not ideal, but overcompensation by crushing tissues between the sutures inhibits angiogenesis and impedes healing as well.

Simple interrupted – The anastomosis (Figure 22.12, Video 22.14a–c) begins at the mesenteric border with one to three interrupted sutures, because the presence of fat in this area makes suture placement most difficult and leakage is most likely to occur. A second suture is placed on the antimesenteric border with the third and fourth sutures placed at the 90° quadrants, respectively. Several more sutures are placed between each of the four quadrant sutures at ~3 mm intervals.

Simple continuous – The anastomosis consists of two separate lines of suture (Figure 22.11b,c). The first suture strand is placed beginning at the mesenteric border because the presence of fat in this area makes suture placement most difficult and leakage is most likely to occur, and the suture tag after tying the knot is held with a hemostat to provide a tag to which the other strand will be tied. A second suture strand is placed on the antimesenteric border. Each suture strand completes half the anastomosis with a simple continuous pattern to meet the other line of suture. These suture strands may be tied separately or may be tied to the suture tag of the opposite line. Often, the author will place an additional two simple interrupted sutures at the mesenteric border.

Recommended suture material is a monofilament, synthetic absorbable suture such as polydioxanone (PDS; PDS II, Johnson & Johnson Medical, New Brunswick, NJ), glycomer 631 (Biosyn) (Biosyn, Medtronic, Minneapolis, MN), or poliglecaprone 25 (Monocryl) (Monocryl, Johnson & Johnson Medical, New Brunswick, NJ) on a taper‐point needle with 3‐0 or 4‐0 suture. After the anastomosis has been completed, the mesenteric defect (Figure 22.11c) is closed with a simple continuous pattern taking care not to include the mesenteric vessels within the sutures. The anastomosis is then covered with a pedicle of greater omentum (Figure 22.13). The omentum with its abundant vascular and lymphatic supply is critical to the successful healing of the intestinal wounds, especially in patients with peritonitis.^22–24 A serosal patch²⁵ can also be created by suturing an adjacent, healthy intestinal loop over the defect or suture line with simple continuous or interrupted sutures. Serosal patches are not commonly performed, and care should be taken to not create a tight hairpin turn with the intestinal loops, which may create a future site for obstruction.

Stapling Techniques

In addition to a handsewn end‐to‐end anastomosis, the most commonly used stapling technique used to perform an anastomosis is a functional end‐to‐end stapled anastomosis (FEESA) using a linear cutting GIA™ stapler for the vertical staple line and a TA™ stapler for the transverse staple line (Figure 22.14). Modifications to this technique, including the use of a GIA™ stapler for the transverse staple line,²⁶ which obviates the need to utilize more than one stapler type, or oversewing of the TA™ staple line with suture, which facilitates inversion of the everted TA™ staple line, have been described.^27–30 Each limb of the GIA™ stapler is placed within the lumen of the intestines both orally and aborally, and the antimesenteric borders are pressed together (Figure 22.15a, Video 22.15). The linear cutting GIA™ is then used to simultaneously staple and cut, creating three rows of staples on either side of the newly created lumen (Figure 22.15b). Next, the linear staple lines should be offset,³¹ and either the GIA™ (three rows of staples) or a TA™ (two rows of staples) stapler can be used to seal off the remaining opening and create the transverse staple line (Figure 22.16). Placement of a crotch suture (Figure 22.17, Video 22.16a,b) is recommended to control tension and prevent separation of apposed jejunal limbs to increase leakage pressures or reduce tension.^32,33 The TA™ staple line has been identified as the most common site of dehiscence or leakage, so reinforcement of the transverse staple line with an oversewn pattern (Figures 22.18 and 22.19, Video 22.17) may be warranted. Also, as with any surgical procedure in the GI tract, an omental wrap is recommended over the R&A site to aid in healing (Video 22.18). Recent studies have shown a decreased rate of dehiscence with oversewn FEESAs compared to non‐oversewn,²⁷ as well as increased leak pressures when using an inverting Cushing pattern.^28–30

Staple size selection – The staples utilized by the GIA™ and TA™ stapler are color‐coded based on staple size. The use of intestinal stapling is limited in application due to fixed staple heights. Too small of a staple size may result in compression of the microvasculature in the intestinal wall or failure to engage the submucosa, whereas too large of a staple may fail to create leak‐resistant apposition of the intestinal ends. These limitations must be considered when utilizing surgical staples in addition to their purported benefits of reduced surgical time, ability to address lumen disparity, decreased need for tissue handling, and ease of use for the novice surgeon.^7,29,34–36 The surgical stapling devices (TA™ and GIA™) and staple sizes presently used in small animals for FEESAs have been adopted from human medicine. Guidelines for their use in veterinary medicine were directly translated from man without formal investigation into differences in intestinal thickness, vascularity, and surgical indications in our small animal patients. For this reason, blue staple cartridges, with a closed staple height of 1.5 mm, were historically used in veterinary medicine, with reservation of the larger green staples (closed staple height of 2.0 mm) for gastric surgery. It has recently been reported that canine small intestinal thickness ranges between 2.06 and 3.13 mm in healthy dogs, which is thicker than human intestines (mean mural thickness of 1.5 mm), indicating that green staple cartridges with a closed staple height of 2.0 mm may be indicated.²⁹ The author routinely uses green staple cartridges when performing FEESA in small animal patients.

Handsewn Versus Stapled Anastomosis

Surgeon preference, equipment availability, patient intestinal size, and location of the intestinal resection often dictate whether a handsewn anastomosis or stapled anastomosis is performed. Studies have shown that both handsewn and FEESA have similar dehiscence rates⁷ and similar leak pressures.²⁹ Stapled anastomoses or FEESAs have been shown to have faster surgical times^7,29 when compared to handsewn anastomoses, and they may be preferred to address luminal disparity.^35,36 Most recently, FEESAs have been shown to have decreased dehiscence rates in the face of preoperative SP.^37,38 Literature in human medicine has shown that handsewn anastomoses have decreased dehiscence rates when compared to stapled anastomoses in trauma patients, which is likely attributed to intestinal edema and fixed staple heights.^39,40 Therefore, the author recommends considering factors such as preoperative SP, intestinal wall edema, patient stability, and other intraoperative factors when deciding whether to perform a handsewn or stapled anastomosis.

Gastrointestinal Biopsies

When full‐thickness intestinal biopsy samples are needed for histopathologic evaluation, an elliptical incision is made in the antimesenteric border of the bowel. With a longitudinal incision with a longitudinal closure, there is no tension on the suture line, but it may reduce the lumen diameter. With a longitudinal incision with a transverse closure, there is more tension on the suture line than with other techniques, but it maintains lumen diameter. With the transverse biopsy technique, a full‐thickness wedge of tissue (~3–4 mm × 1–2 mm) is removed by incising transversely with a #11 or #15 scalpel blade. The defect is closed with interrupted sutures. This permits removal of a small wedge of tissue without damage by thumb forceps, and the transverse orientation prevents bowel stenosis. The author’s preference is to do a punch biopsy technique (Figure 22.20a, Video 22.19) using either a 4‐ or 6‐mm skin punch biopsy instrument depending on the size of the bowel and a sterile wooden tongue depressor. With this technique, the surgeon places the antimesenteric border of the bowel against the tongue depressor and pushes the punch biopsy instrument down full thickness into the antimesenteric margin. The punch biopsy site is then closed transversely with simple interrupted sutures (Figure 22.20b). The surgeon should inspect each biopsy sample to ensure that all intestinal layers are represented, particularly mucosa.

Leak Testing

The intraoperative leak test is often recommended to assess security of enteric suture lines, identify imperfections in closure technique, and prevent postoperative leakage.⁴¹ One method to perform a leak test is to simply milk the intestinal contents to the suture line and observe for leakage at the surgery site. This may be challenging if the bowel is empty. Alternatively, both ends of the segment of bowel may be occluded with either digital pressure or Doyen forceps and saline injected into the lumen of bowel with a needle attached to a syringe (Figure 22.21, Video 22.20). The segment can be gently manipulated while observing the incision line for any leaks. All anastomoses can be made to leak with sufficient pressure. Traditionally, the leak test should be performed with a 22–25 gauge needle and 12 cc syringe holding an approximately 10 cm loop of bowel with Doyen forceps or fingers and injecting approximately 10 mL of water, known as the “rule of 10s.” It is important to remember, however, that all incisions will leak with enough force. Alternatively, a curved hemostat can also be used to gently probe along the incision line and evaluate for defects (Video 22.21), which is the author’s preference.⁴²