Minimally invasive gastrointestinal surgery is an ever-evolving field in veterinary medicine. Its use began with hepatic biopsy sample collection and has evolved into hepatic, pancreatic, and gastrointestinal tract diagnostic sampling and therapy. The techniques may be done with mini-approaches, laparoscopy, or laparoscopic-assistance. Some laparoscopic-assisted techniques have progressed to completely laparoscopic, and some laparoscopic techniques have been done with mini-approaches or specialized entry systems such as wound retraction or SILSTM access (introduction of multiple instruments through a single laparoscope port).
Diagnostic Techniques
The first methods developed and used by practitioners new to laparoscopy are collection of samples for diagnosis of gastrointestinal and accessory organ disease. Hepatic sampling is simple, rapid, and safe for generalized, localized, or nodular disease. Samples may be collected for histopathology, culture, and metal analysis. A single port is used for endoscopic viewing with a second for instrument insertion. The instrument of choice is a cup biopsy forceps. Pre-operative diagnostics should be that expected for the patient with hepatic disease and may include CBC, biochemical profile, bile acids, coagulation profile, and abdominal radiographs and ultrasound. Samples can be obtained with the patient in dorsal or lateral recumbency, with dorsal positioning providing the best access to all liver lobes. The cup forceps are used to grasp the liver margin or more central location, hold for hemostasis, and quickly remove a sample of liver. Take multiple samples of different parts of the liver and remember to collect enough tissue for the diagnostics desired. It is important to avoid insertion of the forceps deeper than the angled jaws to avoid trauma to larger hepatic vessels, a problem more commonly associated with Tru-Cut biopsy needle use. Visually monitor for coagulation of the site. Hemostatic gel foam may be used if necessary, but is rarely required, even in patients with a coagulopathy. Monitoring for hemorrhage after sampling as would be done with fine needle aspiration or Tru-Cut sampling and consists of mucous membrane color and refill time, pulse rate, pulse quality, blood pressure, and demeanor.
Pancreatic biopsies can be taken at the same time as the liver, but require the use of punch rather than cup forceps. Using cup forceps results in pancreatic tearing and hemorrhage. Evaluate the entire pancreas for abnormality, and sample appropriate areas that are free from visible vessels. Similar to the liver, grasp and hold the sample prior to extraction in order to cause hemostasis. Visually and postoperatively monitor for hemorrhage as with hepatic sampling. Larger portions of the pancreas can be removed with increasing difficulty and skill of the operator. Pre-tied loop ligatures can be used for excision of one pancreatic limb. Masses of the body of the pancreas can be excised with interlobar dissection similar to open surgery - being certain to evaluate the local lymph nodes and liver, as beta cell tumors are most common and have usually metastasized at the time of diagnosis.
Diagnostic sampling of the gastrointestinal tract is usually done with laparoscopic assistance. Following complete abdominal exploration, exteriorize the segments of the tract to be sampled. Collect full thickness samples of the tract as with open surgery, suture the defects, test the closure, and perform local lavage prior to replacement in the abdomen. Expansion of the port site with a wound retractor or enlargement with sharp and blunt dissection allows for resection anastomosis to be done. Completely laparoscopic resection anastomosis can be done, but is challenging and requires specialized instrumentation.
Gastrointestinal biopsy often is accompanied by regional lymph node biopsy, which may be done with an open technique using laparoscopic assistance. This can be achieved with cup biopsy forceps, but hemorrhage may be problematic. Specialized instrumentation can be used for lymph node excision; however, care must be taken to avoid the vasculature of the associated GI tract.
Therapeutic Interventions
Treatment of the liver, pancreas, and gastrointestinal tract can likewise be achieved with mini-approaches, laparoscopic assistance, or laparoscopy. Liver mass excision can be evaluated with laparoscopic exploration. The mass should be evaluated for resectability, specifically evaluating hilar involvement. Evaluation of the entire abdomen for metastasis is equally important. Dogs with metastatic disease and carcinomatosis can be spared from a xiphoid to pubic incision and the postoperative morbidity by performing laparoscopic exploration. If the liver mass is deemed excisable, conversion to an open surgery may be done.
Other hepatic treatments include cholecystectomy for biliary mucocele or chronic cholecystitis. Note well that extrahepatic ductal involvement or biliary obstruction has not yet been treated with laparoscopy, as evaluation of the extrahepatic biliary tract and lavage of all lobar ducts is a challenge. Thus far, cholecystectomy is limited to disease of the gall bladder alone. The dissection requires 4 ports: endoscopic, retractor, and 2 instrument portals. The liver and gall bladder are retracted toward the diaphragm, and dissection begins at the cystic duct, which is isolated and ligated with endoscopic clips. Transection of the duct is followed by ligation with a pre-tied loop ligature placed on the side of the duct remaining with the patient. Alternatively, intra-corporeal knots can be placed. Reliance on clips alone is not recommended, as dislodgement would lead to bile peritonitis. The gall bladder is then dissected free from the hepatic fossa using monopolar cautery and a dissection tip or a harmonic scalpel to control hemorrhage. Hepatic biopsy and culture should also be done.
Partial pancreatectomy for insulinoma has been described above under pancreatic biopsy - special care should be taken during the exploratory prior to resection of the pancreatic mass, as metastasis is typically present at the time of diagnosis, and metastatic lesions are also active. Resection of all insulin-secreting masses is the goal of surgery for insulinoma.
Gastrointestinal resection anastomosis has also been described above, again, care should be taken to evaluate for metastatic disease prior to excision of any mass lesion. Conversion to open surgery or use of a wound retractor for the resection is simplest, as specialized instrumentation is required for completely laparoscopic resection anastomosis. The most common reason for gastrointestinal surgery is foreign body removal. It is vital to perform a complete evaluation of the entire GI tract, as parts of the same foreign body or other foreign material may be causing GI damage, removal of the first foreign body identified will not solve all of the problems in those cases. Gastric foreign bodies can be removed with laparoscopic assistance. The foreign body is located, and the stomach brought to the body wall for the gastrotomy and removal of all foreign material in the stomach. Complete gastric evaluation must be done to ensure removal of all foreign material. The stomach is closed routinely, the site lavaged, and the stomach is then returned to the abdomen. Intestinal foreign bodies are similarly removed, but the site is typically tested for leakage prior to local lavage and replacement in the abdomen.
Gastric surgery for the prevention of Gastric Dilatation Volvulus (GDV) involves gastropexy, which can be done completely laparoscopically but is more easily done with laparoscopic assistance. The endoscope is used to locate the pyloric antrum for exteriorization through an instrument port placed 2–3 cm caudal to the costal arch and lateral to the rectus abdominis muscle. The instrument port is placed after transillumination of the body wall at the site to locate the rectus muscle and avoid subcutaneous vasculature. A 10 mm atraumatic grasping forceps is used to lift the antrum with the fold created by the graspers oriented longitudinally from orad to aborad. The instrument port site is widened to at least the width of the gastropexy, and the antrum is brought to the site for stay suture placement. Proper orientation of the stomach must be maintained to avoid kinking the gastric outflow tract, which would lead to outflow obstruction. An incision is made in the seromuscular layer, which is sutured to the transversus abdominis muscle in 2 simple continuous rows of monofilament, absorbable suture. Care must be taken to avoid penetration of the gastric mucosa, which could lead to peritonitis or localized infection. The external abdominal oblique muscle, subcutis, and skin are then closed.
Supportive measures for systemic or GI disease usually include attention to nutrition in critical patients. Laparoscopy can be used to place a jejunostomy tube in the duodenum, and the tube is advanced into the proximal jejunum to avoid pancreatic stimulation upon usage. A port is placed through the right abdominal wall adjacent to the duodenum. Similar to gastropexy, grasping forceps bring the duodenum to the port site, which is lengthened for placement of stay sutures. A purse string suture is placed in the antimesenteric surface of the duodenum, and a stab incision made for passage of the feeding tube. The tube should be advanced aborad into the proximal jejunum, and the duodenum secured to the body wall to decrease the risk of leakage. The remainder of the body wall, subcutis, and skin are then closed. Placing feeding tubes in the jejunum was more commonly associated with orad direction of the tube, which is not desirable. The tube should remain in place for 12–24 h prior to feeding.
Following any laparoscopic procedure, the entire abdomen should be evaluated for hemorrhage or inadvertent trauma, both should be treated prior to abdominal desufflation and closure of the port sites. Decreasing intra-abdominal pressure will allow subclinical hemorrhage to become visible prior to abdominal closure, as the pressure may diminish hemorrhage from the abdominal vasculature. Laparoscopy can be used to perform abdominal exploration and many surgeries that would typically require a large laparotomy. Decreased morbidity and more rapid recovery are expected in healthy patients, and diminished morbidity is desired in critical patients. The learning curve associated with laparoscopy is steep, and diagnostic techniques are usually attempted early in that learning phase. As skill is acquired, more therapeutic interventions such as gastropexy are learned, with the most difficult procedures (such as cholecystectomy) are last to be perfected. Practice with trainers and skill tests using inanimate objects will help to retain laparoscopic skills between surgeries.