Anal fistulae
Anal fistulae, known as perianal fistulae in dogs, are most common in German Shepherd Dogs. They are characterized by draining tracts in the skin around the anus. The cause is unknown. Surgical treatment is common, but recently use of cyclosporine in combination with ketoconazole has been shown to be effective.

Bilious vomiting syndrome
Bilious vomiting syndrome is vomiting in response to bile-induced inflammation of the stomach. Bile salts interfere with the gastric mucosal barrier, allowing acid to irritate the stomach lining and cause gastritis.

Bloat
Bloat (also known as gastric torsion or gastric dilatation-volvulus (GDV)) is an emergency condition in dogs, seen most commonly in deep-chested large and giant breed dogs. The disease is characterized by the presence of a large amount of gas in the stomach and twisting of the stomach along its axis. Treatment for shock and then surgery is usually necessary.

Exocrine pancreatic insufficiency
Exocrine pancreatic insufficiency is the inability to properly digest food due to a lack of digestive enzymes made by the pancreas. This disease is found frequently in dogs

Foreign body
Foreign body is an object foreign to the body that becomes lodged in the gastrointestinal tract (or other part of the dog). Dogs are susceptible to gastrointestinal obstruction due to their ability to swallow relatively large objects and pass them through the esophagus. Foreign bodies most commonly become lodged in the stomach because of the inability to pass through the pyloric sphincter, and in the jejunum.

Hemorrhagic gastroenteritis
Hemorrhagic gastroenteritis is a disease of dogs characterized by sudden vomiting and bloody diarrhea. The symptoms are usually severe and can be fatal if not treated. It is most common in young adult dogs of any breed, but especially small dogs such as the Toy Poodle and Miniature Schnauzer.

Inflammatory bowel disease (IBD)
Inflammatory bowel disease (IBD) is a group of diseases in dogs that are idiopathic and characterized by the presence of inflammatory cell infiltrates in the stomach and/or intestinal walls. It is a common condition. Signs include vomiting, diarrhea, and weight loss. Treatment is with dietary modification and use of medications such as corticosteroids, metronidazole, sulfasalazine, and azathioprine.

Intussusception
Intussusception is characterized by telescoping of one part of the gastrointestinal tract into another part, forming an obstruction. It is most common in dogs six to eight months old. Surgery is necessary for treatment.

Lymphangiectasia
Lymphangiectasia is an intestinal disease of dogs characterized by chronic diarrhea and loss of proteins such as serum albumin and globulin. It is considered to be a chronic form of protein-losing enteropathy. Breeds commonly affected include the Soft-Coated Wheaten Terrier, Norwegian Lundehund, Basenji, and Yorkshire Terrier.

Megaesophagus
Megaesophagus is a disease of the esophagus characterized by low motility and dilation. Most cases in adult dogs are idiopathic. It is the most common cause of regurgitation in dogs. Other causes of megaesophagus include myasthenia gravis, lead poisoning, and Addison's disease.