38 Diseases of the Stomach
GDV must be differentiated from simple dilation in which the stomach is filled with gas, fluid, or ingesta. With a GDV, there is a clockwise rotation of the stomach along its long axis, most commonly 180° though 360° twists can be seen. It is possible that the volvulus results in dilation by trapping gas in the stomach or it may be that dilation of the stomach leads to volvulus. It would seem more likely that volvulus occurs first, because, in most cases, after gastropexy (which prevents volvulus) gastric dilation is rarely seen.
GDVs mainly occur in larger breed dogs, though Basset Hounds, Bulldogs, and Dachshunds can occasionally develop this problem as well. Some of the increased risk may relate to chest conformation in that deep-chested dogs are much more likely to have this problem than are barrel-chested dogs. Ingesting large amounts of food or water at one time might lead to distension of the stomach possibly predisposing to a GDV. Eating rapidly is also thought to contribute to an increased risk of GDV. Exercise after eating has also been considered a potential way that torsion can occur though there are few data to support this contention.
After a GDV is established, severe cardiopulmonary compromise occurs. Increased intraabdominal pressure leads to a decreased ability to fully inspire by compromising the function of the diaphragm. Increased pressure also compromises the cardiovascular system. The vena cava is compressed reducing venous return to the heart. The viscera are underperfused and become edematous; if prolonged enough, necrosis can occur, predominantly of the stomach. The short gastric arteries commonly are torn during the volvulus, further compromising blood supply to the stomach. The spleen is also drawn into an abnormal position by the movement of the stomach resulting in splenic congestion and thrombosis. Various substances including endotoxins, myocardial depressant factor, and cytokines are released from the spleen that have a negative effect on systemic cardiovascular function. Shock is a common occurrence as a result. After the stomach is derotated, the tissues are reperfused. This leads to reperfusion injury, mediated mainly by free radicals.
Dogs usually present with a history of regurgitation, though the owners may interpret this as vomiting. The animals are often anxious and uncomfortable. Abdominal distention may be noted by the owners. On physical examination, the animals often present with signs of shock (tachycardia, weak pulses, delayed capillary refill time, hypotension). Respiratory compromise is evident with shallow, rapid breathing. In most cases the tympanic stomach can easily be found; however, there are some cases of GDV where dilation is minimal.
The clinical signs and signalment are often clue enough to establish a tentative diagnosis of GDV, though this needs to be differentiated from a case of simple dilation. This can be done with radiographs (Fig. 38-1) and the pylorus dorsal to the body of the stomach, though in compromised animals it may be prudent to stabilize the dog before radiography. Right lateral is the preferred view to use for diagnosis. Check the radiographs carefully for evidence of free air; this could indicate gastric rupture.
The goal of treating a GDV is to stabilize cardiovascular function and decompress the dilated stomach. After these goals are achieved the dog is taken to surgery to derotate the stomach and perform a gastropexy to prevent recurrence. Cardiovascular status can be improved by placing large bore intravenous catheters (preferably two). Crystalloids are given at shock doses of 90 ml/kg/hr initially. It is also possible to administer colloids in the resuscitation phase such as 7% hypertonic saline in 6% dextran 70, 5 ml/kg given over 5 minutes. Hetastarch can also be used at 5 to 10 ml/kg over 10 to 15 minutes. If colloids are used, the crystalloid requirement will decrease (20 to 40 ml/kg). Rarely will inotropic support with dopamine or dobutamine be needed.
The next primary goal is to relieve the distension. In animals that are having serious respiratory problems, it may be indicated to do this concurrently with fluid therapy. Opinions vary as to how best to decompress the stomach. Stomach tubing has commonly been recommended. There is the risk of esophageal or stomach rupture if done with too much force, though it can occur with minimal force if the tissue is necrotic. Another alternative is trocarization, which is accomplished with 14- to 16-gauge needles or utilizing an over the needle catheter. The area to be trocarized is percussed, tympany should be evident. The area is clipped and prepped and the needle inserted. This will often relieve enough pressure to significantly improve the dog’s cardiovascular status. Decompression in this manner can also make it easier to pass a stomach tube. In my experience, this has been adequate and the dog is stable enough to take to surgery. In rare cases, a temporary gastrostomy can be performed, usually only if there will be significant delay before definitive surgery.
Routine blood work and urinalysis are indicated to rule out concurrent illnesses and to assess for the severity of acid-base and electrolyte abnormalities. Lactate analysis is also helpful. Markedly elevated lactate concentrations are associated with a poorer outcome. Blood pressure should be monitored to assess for efficacy of resuscitation efforts. An electrocardiogram is also recommended. Most arrhythmias develop during anesthesia or postoperatively and do not appear to correlate to outcome. Arrhythmias at presentation do seem, however, to be associated with increased mortality.
Surgery aims to derotate the stomach and perform a gastropexy to prevent recurrence. In addition other procedures may be necessary such as resection of necrotic tissues (especially stomach) or splenectomy. Surgery should be performed as soon as the dog is relatively stable, delay may result in gastric necrosis and other complications.
A midline celiotomy is performed. Often the omentum covers the stomach, a sign of rotation. The stomach is returned to its normal position. If a stomach tube had not been previously passed it is now passed and the stomach lavaged. After this is accomplished, the stomach is assessed for viability. The area along the great curvature is most prone to ischemia. Assessment is subjective and dependent on experience. Areas that are dark gray or black, lack peristalsis, or do not bleed after being incised are probably significantly compromised. Nonviable tissue is either excised via partial gastrectomy or via partial gastric invagination, though the latter is limited to small areas. The spleen should also be assessed for viability. If the spleen is torsed, significant vessel avulsion is present, or the spleen is infarcted, partial or total splenectomy should be performed.
After the stomach has been assessed and any areas of ischemia addressed, a gastropexy is performed. Several methods have been described including belt-loop gastropexy, tube gastropexy, incisional gastropexy, and circumcostal gastropexy. All procedures tend to produce a durable adhesion of the stomach to the body wall. Which technique to use will depend on operator experience and preference.