Bloat

Bloat is a medical condition in which the stomach becomes overstretched by excessive gas content. It is also commonly referred to as torsion, gastric torsion, and gastric dilatation-volvulus (GDV) 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. The name comes from the Middle English "blout", meaning soft or puffed, which is from the Old Norse "blautr", meaning soft or soaked. [cite web | title = bloat | work = American Heritage Dictionary of the English Language: Fourth Edition | publisher = Bartleby.com | date = 2000 | url = http://www.bartleby.com/61/80/B0328000.html | accessdate = 2007-05-13 ] Meteorism, its name derived from the writings of Hippocrates, is now rarely used in English. The condition occurs most commonly in domesticated animals, especially ruminants and certain dog breeds.

In dogs, gas accumulation in the stomach may cause or be caused by a volvulus, or twisting, 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.cite journal|author=Aronson, Lillian R.|coauthors=Brockman, Daniel J., Brown, Dorothy Cimino|title=Gastrointestinal Emergencies|journal=The Veterinary Clinics of North America|year=2000|volume=30|pages=558–569] With surgery, the mortality rate is 15 to 33 percent.cite journal |author=Beck J, Staatz A, Pelsue D, Kudnig S, MacPhail C, Seim H, Monnet E |title=Risk factors associated with short-term outcome and development of perioperative complications in dogs undergoing surgery because of gastric dilatation-volvulus: 166 cases (1992-2003) |journal=J. Am. Vet. Med. Assoc. |volume=229 |issue=12 |pages=1934–9 |year=2006 |pmid=17173533 |doi=10.2460/javma.229.12.1934]

Causes

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.cite journal |author=Parton A, Volk S, Weisse C |title=Gastric ulceration subsequent to partial invagination of the stomach in a dog with gastric dilatation-volvulus |journal=J. Am. Vet. Med. Assoc. |volume=228 |issue=12 |pages=1895–900 |year=2006 |pmid=16784379 |doi=10.2460/javma.228.12.1895] 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, 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. [cite journal |author=Glickman L, Glickman N, Schellenberg D, Raghavan M, Lee T |title=Incidence of and breed-related risk factors for gastric dilatation-volvulus in dogs |journal=J. Am. Vet. Med. Assoc. |volume=216 |issue=1 |pages=40–5 |year=2000 |pmid=10638316 |doi=10.2460/javma.2000.216.40] Dogs with inflammatory bowel disease may be at an increased risk for bloat. [cite journal |author=Braun L, Lester S, Kuzma A, Hosie S |title=Gastric dilatation-volvulus in the dog with histological evidence of preexisting inflammatory bowel disease: a retrospective study of 23 cases |journal=Journal of the American Animal Hospital Association |volume=32 |issue=4 |pages=287–90 |year=1996 |pmid=8784718]

Dietary factors

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. [cite journal |author=Glickman L, Glickman N, Schellenberg D, Raghavan M, Lee T |title=Non-dietary risk factors for gastric dilatation-volvulus in large and giant breed dogs |journal=J. Am. Vet. Med. Assoc. |volume=217 |issue=10 |pages=1492–9 |year=2000 |pmid=11128539 |doi=10.2460/javma.2000.217.1492] Eating only once daily [cite journal |author=Glickman L, Glickman N, Schellenberg D, Simpson K, Lantz G |title=Multiple risk factors for the gastric dilatation-volvulus syndrome in dogs: a practitioner/owner case-control study |journal=Journal of the American Animal Hospital Association |volume=33 |issue=3 |pages=197–204 |year=1997 |pmid=9138229] and eating food consisting of particles less than 30 mm in size also may increase the risk of bloat. [cite journal |author=Theyse L, van de Brom W, van Sluijs F |title=Small size of food particles and age as risk factors for gastric dilatation volvulus in great danes |journal=Vet. Rec. |volume=143 |issue=2 |pages=48–50 |year=1998 |pmid=9699253] One study looking at the ingredients of dry dog food found that while neither increased grains, soy, or 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. [cite journal |author=Raghavan M, Glickman N, Glickman L |title=The effect of ingredients in dry dog foods on the risk of gastric dilatation-volvulus in dogs |journal=Journal of the American Animal Hospital Association |volume=42 |issue=1 |pages=28–36 |year=2006 |pmid=16397192]

Breed susceptibility

The five breeds at greatest risk are Great Danes, Weimaraners, St. Bernards, Gordon Setters, and Irish Setters. [cite journal |author=Glickman L, Glickman N, Pérez C, Schellenberg D, Lantz G |title=Analysis of risk factors for gastric dilatation and dilatation-volvulus in dogs |journal=J. Am. Vet. Med. Assoc. |volume=204 |issue=9 |pages=1465–71 |year=1994 |pmid=8050972] In fact, the lifetime risk for a Great Dane to develop bloat has been estimated to be close to 37 percent. [cite journal |author=Ward M, Patronek G, Glickman L |title=Benefits of prophylactic gastropexy for dogs at risk of gastric dilatation-volvulus |journal=Prev. Vet. Med. |volume=60 |issue=4 |pages=319–29 |year=2003 |pmid=12941556 |doi=10.1016/S0167-5877(03)00142-9] Standard Poodles are also at risk for this health problem,cite web | title = Gastric Dilatation-volvulus | work = The Merck Veterinary Manual | date = 2006 | url = http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/23305.htm | accessdate = 2007-04-17 ] as are Doberman Pinschers and Rottweilers. [ [http://dogtime.com/bloat.html Bloat | DogTime - Warning signs to watch for ] ] Basset Hounds have the greatest risk for dogs less than 23 kg.

Pathology

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. [cite web | last = Bright | first = Ronald M. | title = Gastric Dilatation-Volvulus: Risk Factors and Some New Minimally Invasive Gastropexy Techniques | work = Proceedings of the 29th World Congress of the World Small Animal Veterinary Association | date = 2004 | url = http://www.vin.com/proceedings/Proceedings.plx?CID=WSAVA2004&PID=8763&O=Generic | accessdate = 2007-04-17 ] 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.

ymptoms

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). [cite journal |author=Brockman D, Washabau R, Drobatz K |title=Canine gastric dilatation/volvulus syndrome in a veterinary critical care unit: 295 cases (1986-1992) |journal=J. Am. Vet. Med. Assoc. |volume=207 |issue=4 |pages=460–4 |year=1995 |pmid=7591946] Chronic bloat may occur in dogs, symptoms of which include loss of appetite, vomiting and weight loss.cite web | last = Fossum | first = Theresa W. | title = Gastric Dilatation Volvulus: What's New? | work = Proceedings of the 31st World Congress of the World Small Animal Veterinary Association | date = 2006 | url = http://www.ivis.org/proceedings/wsava/2006/lecture25/Fossum4.pdf?LA=1 | format = PDF | accessdate = 2007-04-17 ]

Diagnosis

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).

Treatment

Bloat is an emergency medical condition: having the animal examined by a veterinarian is imperative. Bloat can become fatal within a matter of minutes.

First Aid

A dog owner can sometimes relieve the immediate pressure of bloat by passing a tube down the throat, as an emergency first aid technique. This is not an easy task and cannot readily be improvised; 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. [http://www.kifka.com/Elektrik/BloatFirstAid.htm] [http://www.dachshund.org/bloat_instructions.html] [http://www.moderndogmagazine.com/pdf/FIRST_AID_CARE_FOR_PETS.pdf] This is not a substitute for immediate veterinary treatment. There is risk of esophagus or stomach rupture if the tube is inserted too forcefully, or if the stomach is necrotic. [cite web | title = Gastric Dilatation/Volvulus General Review | work = Small Animal Gastroenterology | publisher = University of Pennsylvania School of Veterinary Medicine | date = 2002 | url = http://caltest.vet.upenn.edu/sagastro/genrev/revgdv.htm#Possible%20Complications | accessdate = 2006-12-05 ]

Veterinary 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. 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).cite journal |author=Rawlings C, Mahaffey M, Bement S, Canalis C |title=Prospective evaluation of laparoscopic-assisted gastropexy in dogs susceptible to gastric dilatation |journal=J. Am. Vet. Med. Assoc. |volume=221 |issue=11 |pages=1576–81 |year=2002 |pmid=12479327 |doi=10.2460/javma.2002.221.1576] 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 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. [cite journal |author=Glickman L, Lantz G, Schellenberg D, Glickman N |title=A prospective study of survival and recurrence following the acute gastric dilatation-volvulus syndrome in 136 dogs |journal=Journal of the American Animal Hospital Association |volume=34 |issue=3 |pages=253–9 |year=1998 |pmid=9590454] 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.cite book | last = Wingfield | first = Wayne E. | title = Veterinary Emergency Medicine Secrets | publisher = Hanley & Belfus, Inc | date = 1997 | id = ISBN 1-56053-215-7 ]

Prognosis

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 factors.

Bloat in cattle

In cattle, bloating is most often caused by the animal eating damp, green alfalfa. New (green) alfalfa hay, especially that made from the first cutting of the year, must be kept from cattle until it has aged for several weeks. When a calf has become bloated, often a section of hose is inserted down the throat and into the stomach to relieve the gas pressure that builds up. A veterinarian should be called for treatment. As with dogs, death of the animal often results if bloat is not quickly treated.

References

External links

* [http://www.veterinarypartner.com/Content.plx?P=A&S=0&C=0&A=672 "Bloat The Mother of All Emergencies" from The Pet Health Library]
* [http://www.canismajor.com/dog/bloat.html Dog Owner's Guide: Bloat]
* [http://www.dogpausebowl.com/Whitepaper_s/28.htm Whitepaper on Healthy Dog Eating]