A dog vomiting dark brown or black is concerning, and depending on the underlying cause, you may need to see your veterinarian. The dark brown vomiting may be indicative of some serious medical conditions that require prompt treatment. Normally, the color of dog vomit tends to vary based on what the dog ate. When a dog vomits on an empty stomach the vomit tends to be bright yellow or slightly greenish due to the presence of bile. Clear vomit instead is seen when the dog brings back up swallowed saliva coming from the stomach. Red streaks of blood in very small quantities are usually suggestive of gastric irritation due to vomiting and are generally not due to any particular pathology. Following are several possibilities as to why a dog may be vomiting dark brown fluid.
Ingesting Something Brown
As mentioned, dog vomit tends to take the color of what a dog may have ingested. Dogs are known for eating the most unexpected things so it's not unusual for them to ingest something brown at times.
If your dog ingested something that is dark brown in color, that may explain why your dog is vomiting brown. Substances that may cause a dog to vomit dark brown may include chocolate (which is toxic to dogs), feces or dirt, but certain foods may look brown too once digested.
When a dog develops an ulcer, the ulcer may bleed. When the bleeding stems from an ulcer in the dog's stomach wall or upper intestine, the blood is digested by stomach acid and therefore assumes a brown color. When dogs vomit the blood, dog owners often refer to it as looking like "coffee grounds." Further proof of a bleeding ulcer is the presence of black, tarry stools, but this is not always present. Ulcers may form in dogs taking aspirin or other non-steroidal anti-inflammatory drugs. When a dog presents with blood in the vomit, whether fresh or digested, it's medically referred to as " "hematemesis."
Other Sources of Bleeding
Bleeding in the digestive tract may also be caused by a blood clotting disorder, metabolic disorders (kidney/liver problems) or a bleeding tumor in the stomach or upper small intestine. Ingestion of rat poison may cause black stools and vomiting of blood. Sometimes, secondary hematemesis can occur when a dog is swallowing blood coming from the mouth, lungs, a nosebleed or after licking blood from a wound. When the dog then vomits this swallowed blood, it may appear as black or dark brown with a coffee ground appearance.
Hemorrhagic gastroenteritis can sometimes cause a dog to vomit digested blood. Because hemorrhages are serious and can lead to anemia, low blood pressure and death, it's imperative to see the vet immediately. Pale gums are a warning sign of excess blood loss.
Another possible cause of a dog vomiting dark brown fluid is a blockage. When a dog vomits dark brown and it's accompanied by a fetid odor, it can mean that the dog ingested feces.
However, dark vomit accompanied with a fetid smell, could mean that the dog is suffering from a total blockage, explains Dr. Rebecca Kirby, a board-certified veterinarian specializing in internal medicine. Blockages may occur as a result of ingesting bone or rawhide or from a growth in the dog's abdomen.
As seen, a dog vomiting dark brown or black can be something as innocent as a dog vomiting back something that was eaten previously or it could signal a serious medical disorder that requires prompt treatment.
When it doubt, it's best to play it safe and see a veterinarian sooner than later.