Gastric dilatation volvulus
Gastric dilatation volvulus (also known as bloat or a twisted stomach) is a medical condition in which the stomach becomes overstretched by excessive gas content. It is also commonly referred to as torsion and gastric torsion when the stomach is also twisted. The word bloat is often used as a general term to cover gas distension of the stomach with or without twisting. Meteorism, its name derived from the writings of Hippocrates, is now rarely used in English. The condition occurs commonly in domesticated animals, especially ruminants and certain dog breeds.
In dogs, gas accumulation in the stomach is usually associated with volvulus of the stomach, which prevents gas from escaping. Deep-chested breeds are especially at risk. Mortality rates in dogs range from 10 to 60 percent, even with treatment. With surgery, the mortality rate is 15 to 33 percent.
Bloat in dogs is likely caused by a multitude of factors, but in all cases the immediate prerequisite is a dysfunction of the sphincter between the esophagus and stomach and an obstruction of outflow through the pylorus, or a clog. Some of the more widely acknowledged factors for developing bloat include increased age, breed, having a deep and narrow chest, stress, eating foods such as kibble that expand in the stomach, overfeeding, too much water consumption in a small period of time; before or after exercise and other causes of gastrointestinal disease and distress. Studies have indicated that the risk of bloat in dogs perceived as happy by their owners is decreased, and increased in dogs perceived as fearful. This may be due to the physiological effects of the dog's personality on the function and motility of the gastrointestinal system.; alternatively perhaps the dogs become unhappy/uncomfortable as a consequence of the conditions that lead up to exhibiting bloat. Dogs with inflammatory bowel disease may be at an increased risk for bloat.
One common recommendation in the past has been to raise the food bowl of the dog when it eats. However, studies have shown that this may actually increase the risk of bloat. Eating only once daily and eating food consisting of particles less than 30 mm in size also may increase the risk of bloat. One study looking at the ingredients of dry dog food found that while neither grains, soy, nor animal proteins increased risk of bloat, foods containing an increased amount of added oils or fats do increase the risk, possibly due to delayed emptying of the stomach.
As a general rule, bloat is of greatest risk to deep-chested dogs. The five breeds at greatest risk are Great Danes, Weimaraners, St. Bernards, Gordon Setters, and Irish Setters. In fact, the lifetime risk for a Great Dane to develop bloat has been estimated to be close to 37 percent. Standard Poodles are also at risk for this health problem, as are Irish Wolfhound, Doberman Pinschers, Rottweilers, German shorthaired pointer, German Shepherds and Rhodesian Ridgebacks. Basset Hounds have the greatest risk for dogs less than 23 kg/50 lbs.
The stomach twists around the longitudinal axis of the digestive tract, also known as volvulus. Gas distension may occur prior to or after the stomach twists. The most common direction for rotation is clockwise, viewing the animal from behind. The stomach can rotate up to 360° in this direction and 90° counterclockwise. If the volvulus is greater than 180°, the esophagus is closed off, thereby preventing the animal from relieving the condition by belching or vomiting. The results of this distortion of normal anatomy and gas distension include hypotension (low blood pressure), decreased return of blood to the heart, ischemia (loss of blood supply) of the stomach, and shock. Pressure on the portal vein decreases blood flow to liver and decreases the ability of that organ to remove toxins and absorbed bacteria from the blood. At the other end of the stomach, the spleen may be damaged if the twisting interrupts its blood supply. If not quickly treated, bloat can lead to blood poisoning, peritonitis and death by toxic shock.
Symptoms are not necessarily distinguishable from other kinds of distress. A dog might stand uncomfortably and seem to be in extreme discomfort for no apparent reason. Other possible symptoms include firm distension of the abdomen, weakness, depression, difficulty breathing, hypersalivation, and retching without vomiting. A high rate of dogs with bloat have cardiac arrhythmias (40 percent in one study). Chronic bloat may occur in dogs, symptoms of which include loss of appetite, vomiting and weight loss.
A diagnosis of bloat is made by several factors. The breed and history will often give a significant suspicion of bloat, and the physical exam will often reveal the telltale sign of a distended abdomen with abdominal tympany. Shock is diagnosed by the presence of pale mucous membranes with poor capillary refill, increased heart rate, and poor pulse quality. X-rays (usually taken after decompression of the stomach if the dog is unstable) will show a stomach distended with gas. The pylorus, which normally is ventral and to the right of the body of the stomach, will be cranial to the body of the stomach and left of the midline, often separated on the x-ray by soft tissue and giving the appearance of a separate gas filled pocket (double bubble sign).
Bloat is an emergency medical condition: having the animal examined by a veterinarian is imperative. Bloat can become fatal within a matter of minutes.
Bloat is an emergency that requires treatment by a veterinarian as soon as possible. Some web sites document so-called bloat first aid kits and contain descriptions of the first aid a dog owner can provide at the time an attack of bloat is discovered.    This is not a substitute for immediate veterinary treatment. There is risk of esophagus or stomach rupture if a tube is inserted too forcefully in an attempt to relieve pressure.
It is always advisable to seek veterinary advice before attempting any procedures at home as these may further worsen the animal's condition.
Regardless of the success of an at home treatment, veterinary intervention is always necessary, as the condition carries a poor to grave prognosis without treatment.
Treatment usually involves resuscitation with intravenous fluid therapy, usually a combination of isotonic fluids and hypertonic saline or a colloidal solution such as hetastarch, and emergency surgery. The stomach is initially decompressed by passing a stomach tube, or if that is not possible, multiple trocars can be passed through the skin into the stomach to remove the gas, alternatively the trocars may be inserted directly into the stomach following anaesthesia in order to reduce the chances of infection. During surgery, the stomach is placed back into its correct position, the abdomen is examined for any devitalized tissue (especially the stomach and spleen). A partial gastrectomy may be necessary if there is any necrosis of the stomach wall.
Prevention and reduction of recurrence
Recurrence of bloat attacks can be a problem, occurring in up to 80 percent of dogs treated medically only (without surgery). To prevent recurrence, at the same time the bloat is treated surgically, a right-side gastropexy is often performed, which by a variety of methods firmly attaches the stomach wall to the body wall, to prevent it from twisting inside the abdominal cavity in the future. While dogs that have had gastropexies still may develop gas distension of the stomach, there is a significant reduction in recurrence of gastric volvulus. One study showed that out of 136 dogs that had surgery for bloat, 4.3 percent of those that did have gastropexies had a recurrence, while 54.5 percent of those without the additional surgery recurred. Gastropexies are also performed prophylactically in dogs considered to be at high risk of bloat, including dogs with previous episodes of bloat or with gastrointestinal disease predisposing to bloat, and dogs with a first-order relative (parent or sibling) with a history of bloat.
Precautions that are likely to help prevent bloat include feeding small meals throughout the day instead of one big meal and not exercising immediately before or after a meal.
Immediate treatment is the most important factor in a favorable prognosis. A delay in treatment greater than six hours or the presence of peritonitis, sepsis, hypotension, or disseminated intravascular coagulation are negative prognostic indicators.
Historically, GDV has held a guarded prognosis, with mortality rates approaching 25% to 40% even with treatment; however, a recent study has shown that with prompt treatment and good preoperative stabilization of the patient, mortality is significantly lessened to 10% overall (in a referral setting). Negative prognostic indicators following surgical intervention include postoperative cardiac arrhythmias, splenectomy, or splenectomy with partial gastric resection. Interestingly, a longer time from presentation to surgery was associated with a lower mortality, presumably because these dogs had received more complete preoperative fluid resuscitation and were thus better cardiovascularly stabilized prior to the procedure.
Bloat in cattle
In cattle, bloating is most often caused by the animal eating young and lush pasture, usually if the pasture has a high proportion of legumes (medicks, clover or lucerne (alfalfa)). Legumes contain foaming agents which trap air bubbles in the ruminant's rumen and prevent them from belching to relieve the pressure. This causes a build up of pressure in the rumen which manifests as an obvious swelling on the left side. Signs of bloat in cattle are distended left abdomen, stopping of grazing, lethargy, appearing distressed, difficulty in urinating or defecating, rapid breathing and staggering. In mild and moderate cases an antibloating agent will be administered orally or through a stomach tube and the ruminant should be exercised. In severe cases a wide bore trochar and cannula can be inserted into the rumen on the left flank to release the gas and liquid. In emergency cases of frothy bloat, this may not be enough and a 10–20 cm incision may need to be made in the animal’s side and the froth manually removed. Veterinary care is then needed to clean and stitch the wound and administer an antibiotic to the animal.
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