Dr Ross Elliot BVSc MMedVet (Surg)
Bryanston Veterinry Hospital.
Tel 011 706 6023
The stomach is generally very forgiving, however if taken lightly gastric surgery can have fatal consequences. The position of the stomach in the cranial abdomen makes exteriorisation difficult.
The stomach is divided into four areas, which are important to identify when performing gastro-intestinal surgery. The cardia is the region where the oesophagus blends into the stomach. The fundus is the large out-pouching of the stomach along the greater curvature. The body of the stomach lies between the fundus and the pylorus and forms the reservoir of the stomach. The pylorus is the distal third of the stomach or the outflow tract. The pylorus is divided into two parts the thin walled antrum of the pylorus and the thick muscular pyloric sphincter.
The greater omentum is attached at the greater curvature and the lesser omentum at the lesser curvature. The greater omentum forms the large leaf of omentum in the abdomen. The lesser omentum forms a part of the hepatogastric ligament.
Healing of the Stomach
Full thickness incisional healing of the stomach occurs rapidly. The stomach has an extensive blood supply making the regular phases of healing rapid. Collagen for repair is not only produced by fibroblasts but the smooth muscle cells of the stomach also contribute to collagen formation. The return of normal gastric strength after incisional trauma is about 14 days.
Generally surgery of the stomach is an emergency and surgical preparation involves patient stabilisation rather than a nil per os period etc. These patients should have fluid and acid base and electrolytes abnormalities corrected prior to surgery.
In elective procedures food should ideally be withheld for 8 hours to allow for gastric emptying. Fasting for longer than 12 hours can actually have negative effects. Increased fasting duration leads to increased gastric acid decreased pH, which can lead to increased gastro-oesophageal reflux.
General Surgical Principles
Remember Halsted’s principles of surgical technique minimise tissue trauma, practise precise haemostasis, preserve the blood supply, use aseptic technique, minimise tension on the tissue, use accurate tissue apposition and obliterate dead space. The stomach is generally very forgiving, however if taken lightly gastric surgery can have fatal consequences. The greatest risk is leakage of gastric content, which can lead to significant morbidity and mortality.
The position of the stomach in the cranial abdomen makes exteriorisation difficult. The supporting ligaments such as the hepato-gastric and hepato-duodenal ligaments can be carefully transected, however it is essential to identify the important structures such as the common bile duct that run in these structures to prevent damage.
The stomach is approached by a ventral midline celiotomy for most procedures. A midline incision of sufficient length is made to allow proper visualisation (no keyhole surgery!). Trying to save time by making a small incision will increase the risk of contamination and postoperative morbidity.
When handling the stomach it is ideal to minimise the use of instruments. Stay sutures are ideal in handling, stabilising and exteriorising the stomach and preventing abdominal contamination. Once the stay sutures have been placed, the proposed area for surgery should be packed off from the rest of the abdomen with moistened abdominal swabs. Put the moistened abdominal swabs down first to contact the serosa and then dry ones on top and adjacent to the bowel to be opened as needed to absorb contamination. Keep tissues moist to protect them and make handling less traumatic.
An avascular area midway between the greater and lesser curvature is the most common site for surgical procedures of the stomach. A stab incision is made in the stomach and a large incision is extended from the stab incision. Note that mucousal eversion is normal and occurs readily. Once surgery has been completed the stomach should be closed in a double layer closure. An inverting suture pattern such as a Cushing, Connell or Lembert should be used. These patterns should not however be used in surgery of the pylorus as they can decrease the outflow diameter of the pylorus. A simple continuous pattern is generally recommended for surgery in this area. If you’re using stay sutures, make sure the incision does not have tension on it when you are closing the stomach because when you let go of the stay sutures your closure will be loose.
Only a monofilament absorbable suture material should be used in the stomach. Multi-filament materials have increased tissue drag and are not ideal for use in the delicate gastric tissues. The most commonly used monofilament materials are Polydiaxanone, Polyglyconate and Poliglecaprone 25. Polydiaxone is not ideal as it shows an increased degradation rate approximately 10 times normal in an acidic environment. Polyglyconate and Poliglecaprone show an initial increase in degradation rate but this stabilises and they are the materials of choice. Chromic catgut shows rapid degradation in gastric juices and should not be used.
Once the incision into the stomach has been closed all instruments and gloves should be changed. A new surgical set is opened and the abdomen closed. Nothing that was used to open the stomach should be used to close the abdomen. The abdomen should be lavaged with warmed ringers lactate. The ringer’s lactate should be warmed by placing it in a hot water bath or incubator. Heating bags up in the microwave can lead to uneven heating of the fluid and burns to the patient
Specific Surgical Procedures
Most gastric disease can be diagnosed by a partial thickness biopsy taken via gastroscopy. However there are some diseases that require a full thickness biopsy, which has to be taken by a celiotomy. To perform this, a small gastrotomy is performed and a full thickness section of stomach is removed and sent for histopathological examination. The gastrotomy site is closed according to general principles.
A gastrotomy is performed to remove foreign bodies from the stomach and linear foreign bodies. It is performed via a midline celiotomy, and through the ventral surface of the stomach. An avascular area is selected between the greater and lesser curvature. Stay sutures should be used used and handled by an assistant to prevent contamination of the abdomen. Closely inspect the deep area of the fundus for foreign bodies as well as the pylorus and cardia. The site is closed as previously described. Always obtain postoperative radiographs to ensure that nothing has been left behind.
Partial Gastrectomy or Gastric Wall Invagination
These procedures are commonly performed to remove non-viable gastric tissue after gastric dilatation/volvulus. It incorporates many of the basic surgical principles such as stay sutures and packing off the abdomen to isolate the stomach and prevent contamination with gastric content. The big difficulty is deciding on which tissue is viable and non-viable. This is a very subjective assessment and multiple factors should be taken into account. The colour of the stomach, palpation of wall thickness, capillary refill time and peristalsis should all be taken into account when deciding on gastric wall viability.
There is no difference in outcome between performing a gastric invagination or a gastrectomy. A gastrectomy tends to take a bit longer and thus increase surgical time, however the benefit is that all the necrotic tissue is removed and will not be a cause of problems in the future if the animal survives. To perform a gastrectomy a zone between viable and non-viable stomach wall is selected, usually starting in the area just near the cardia. Stay sutures are placed and the non-viable section removed placing more stay sutures as you go. These are held by an assistant to prevent contamination of the abdomen with gastric content. The ventral and dorsal surface of the viable stomach is now sutured in a two-layer closure with an inverting pattern. Basic principles apply for the lavage and closure of the stomach and abdomen.
The gastric invagination procedure is quicker and thus making the surgical time shorter, however in patients that survive there is the risk of a large non-healing gastric ulcer in the portion of the stomach wall invaginated that requires long term treatment or repeat surgery. This procedure is performed by selecting the same zone between viable and non-viable tissue and then placing an inverting suture to invert the non-viable stomach wall into the lumen of the stomach. It is best to start at the cardia for ease of suturing. Basic principles apply for lavage and closure.
Gastropexy is the gold standard in preventing gastric dilatation volvulus form occurring or recurring. A gastropexy by definition, is the formation of a permanent adhesion from the stomach to the adjacent body wall. The most common indication for a gastropexy is to prevent gastric dilatation volvulus (GDV), however it is used in the treatment of hiatal hernias.
Gastropexy for GDV is generally performed between the pylorus and the right body wall. There are a fair number of different techniques that can be performed. These are the circumcostal, belt loop, incisional, laparoscopic and tube gastropexy to name a few. The strength of the first two is nearly double that of an incisional. However these two take longer to perform and have increased associated discomfort and pain.
Another important factor is to make the incision in the stomach through the seromuscular layers leaving only the mucosa intact. It is essential not to penetrate the mucosa. This can lead to motility disorders abscessation and draining tracts. The incision in the body wall should penetrate the muscle layer to ensure adequate adhesion formation. The two incisions should be around 4-5 cm in length. The same principles apply to the other techniques for performing gastropexy. Release abdominal wall incision traction or close the Balfour retractor; as this will allow anatomical apposition of the two sites
For treatment of hiatal hernias a gastropexy of the fundus to the left body wall, an oesophagopexy and closure of the hiatus in the diaphragm are performed. Basic principles as for a pyloric gastropexy are applied here just a change in the position it is performed.
Pyloroplasty and Pyloromyotomy
Pyloroplasty is performed for alleviation of gastric outflow obstruction. The most commonly performed pyloroplasty performed is a Y-U pylorolasty. A full thickness Y shaped incision into the pylorus is made using basic principles. This is then closed in a U shaped closure, thus increasing the diameter of the outflow tract. A Heineke- Mikulicz Pyloroplasty is simple to perform but will not increase the outflow tract as much as a Y-U. This is performed by making a full thickness longitudinal incision in the pylorus. This is then closed in a horizontal closure. A simple interrupted or continuous suture should be performed and not an inverting suture as this can decrease outflow tract diameter.
A pyloromyotomy is simpler to perform but does not allow for inspection and taking of samples of the pylorus. It is performed by a partial thickness incision through the seromuscular layers leaving the mucosa intact. This is then left un-sutured to allow the pylorus to dilate. Its use is restricted to a handful of applications.
It is advised to continue fluid therapy until the animal is eating and drinking. If there is a protracted period of anorexia expected post surgery then a feeding tube should be placed. An oesophagostomy tube is idea and simple to place after surgery. Oral intake should be initiated no longer than 7 hours post surgery. This is essential for healing of the intestinal system as eating stimulates stimulates peristalsis and aids in recovery.
There is no need for postoperative antibiotics in gastro-intestinal surgery, unless there was an established peritonitis prior to surgical treatment. No antibiotic will stop a leak in the intestinal system or treat the effects – they will only delay its discovery. The recommended protocol is pre-operative antibiotics 30 minutes prior to surgery then every hour during surgery.
There is no evidence to justify continuing antibiotics after surgery. Any vomiting should be investigated as soon as possible as it can be an early sign of intestinal breakdown. In cases of vomiting it is indicated to l perform serial abdominal scans to check for free abdominal fluid and monitor the patients’ temperature for pyrexia. Prokinetic agents are useful post operatively and will often stop the vomiting caused by ileus. In cases of gastric invagination use of long-term proton pump inhibitors and coating agents are indicated.