Dog vomiting blood: gastrointestinal bleeding

Overview

Bleeding is a sign whose source may be the oesophagus, stomach, small intestine or large intestine. It may be acute or longstanding. With occult bleeding, blood cannot be seen with the naked eye. With overt bleeding, blood is visible in vomit or stools.

The medical term for vomiting blood is haematemesis. It can look like bright blood or dark material resembling coffee grounds. Black, sticky, tarry stools are called melaena and contain partly digested blood. Passing bright blood, or haematochezia, usually involves bleeding from the colon, rectum or anal area.

Causes

Damage to the lining can open a blood vessel

A gastrointestinal ulcer is a common cause of bleeding. Normally, mucus, bicarbonate and good blood flow protect the stomach lining. If protection is damaged, acid and digestive enzymes can injure progressively deeper layers of the wall. If damage reaches an arterial wall, bleeding can be heavy.

Non-steroidal anti-inflammatory drugs, or NSAIDs, can directly damage the lining. They can also reduce production of protective prostaglandins. An intestinal tumour, foreign body or chronic inflammation can also cause a bleeding ulcer. Other possible causes include parvovirus and parasites such as hookworms and whipworms. Acute haemorrhagic diarrhoea syndrome, or AHDS, is one differential diagnosis for profuse bloody diarrhoea.

Clotting problems or disease in another organ can maintain bleeding

Low platelets can cause gastrointestinal bleeding without a large local ulcer. Anticoagulant rodenticides and disseminated intravascular coagulation, or DIC, are other possible causes. A dog may have both lining damage and a clotting disorder.

Liver disease, impaired kidney function or Addison's disease may be associated with ulcer formation. Pancreatitis and sepsis can impair the lining through systemic inflammation. Structural blood vessel abnormalities are less common causes of bleeding in dogs.

Risk factors

Stomach ulcers occur in young and adult dogs, but more are identified in adults. Medication and other diseases are central risk factors when assessing ulcer bleeding. Even a selective NSAID intended for dogs does not eliminate the possibility of ulceration or perforation.

Using two NSAIDs together increases gastrointestinal adverse effects. Combining an NSAID with a corticosteroid also increases ulcer risk. Severe systemic illness, major surgery or inadequate circulation can predispose dogs to lining damage. Extreme physical exertion, such as sled dog racing, is another recognised ulcer risk.

Puppies, old dogs and very small dogs dehydrate readily during vomiting and diarrhoea.

Typical symptoms

Signs depend on the amount and duration of bleeding and how long blood takes to pass through the intestine. Obvious blood in vomit or melaena is not always seen, even with significant blood loss.

• Vomit contains red blood or dark coffee-ground material.
• Stools become black, sticky and tarry.
• Fresh, bright blood passes with stools.
• Your dog eats poorly, vomits or has a tender abdomen.
• Your dog becomes tired or weak, or the gums become pale.
• Disease with prolonged bleeding may cause weight loss.

Heavy upper gastrointestinal bleeding can pass rapidly through the intestine and appear as fresh blood in stools. Conversely, slowly moving blood can become black even when bleeding starts lower in the intestine. Swallowed blood from the nose or mouth can cause bloody vomit or melaena despite a source outside the gastrointestinal tract.

Duodenal bleeding may not appear in vomit unless sufficient intestinal contents flow back into the stomach.

Complications and consequences

Blood loss reduces oxygen transport

Ongoing bleeding can cause anaemia, meaning too few red blood cells. With prolonged bleeding, iron stores can become depleted and iron-deficiency anaemia develop. Sudden heavy bleeding can reduce circulating blood volume enough to cause shock. In shock, your dog's limbs may become cold and the pulse weak.

A deep ulcer can perforate the intestinal or stomach wall and cause peritonitis. Spreading infection can lead to sepsis.

Total blood protein may decrease with ulcer bleeding. In iron-deficiency anaemia, red blood cells may become smaller than normal and contain less haemoglobin.

The outlook depends on the cause and severity

The outlook for a mild ulcer is generally favourable if its cause is controlled and treatment starts promptly. Moderate or severe gastrointestinal bleeding requiring transfusion has been associated with mortality of around 29–45%. Mortality in dogs and cats operated on for perforation has been estimated at around 60%. These figures concern severely affected patient groups, rather than every minor episode of blood in stools.

Diagnosis at the vet

Circulation is assessed before precisely locating the bleeding

Your vet first assesses circulation, pulse, mucous membranes and possible shock. In a seriously ill dog, circulation is supported while the cause is investigated. Examination also looks for bleeding elsewhere and tiny spots on mucous membranes. Rectal examination may reveal blood, a tumour or a foreign body.

A blood count checks red blood cells, haemoglobin and platelets. Repeated haematocrit measurements monitor progressing blood loss and treatment response. Clotting tests investigate bleeding associated with factors such as rodenticides or clotting factor deficiency. Biochemistry and urinalysis look for other diseases and consequences of bleeding.

In AHDS, haematocrit may instead be raised despite bloody diarrhoea. Plasma protein may then remain relatively normal. Suspected Addison's disease can be investigated further with an ACTH stimulation test.

Endoscopy and imaging complement one another

X-rays can look for obstruction, a foreign body or free gas suggesting perforation. Ultrasound may reveal a wall change, tumour or ulcer. Normal ultrasound does not exclude an unperforated ulcer, as sensitivity for detecting these is poor.

Endoscopy shows the lining's surface and allows biopsies to investigate underlying disease. It requires anaesthesia, so the patient is stabilised first. An ulcer biopsy is usually taken at the edge to avoid perforating the damaged wall. A conventional endoscope cannot reach the entire small intestine. A capsule camera can help examine areas of lining harder to reach with conventional endoscopy.

In a group of 89 bleeding patients, 24 dogs had occult bleeding. The blood urea nitrogen-to-creatinine ratio did not prove useful for identifying occult bleeding. It also poorly distinguished upper from lower gastrointestinal bleeding. Faecal occult blood testing can supplement investigations, but food and intestinal bacteria can cause false positives.

For a peroxidase-based faecal blood test, your dog may need a meat-free diet for at least 72 hours according to laboratory instructions.

Treatment

Fluids and blood products support circulation

The most urgent treatment goal is stabilising circulation. Fluid therapy corrects dehydration and metabolic disturbances. Heavy blood loss may require red blood cells or whole blood. Transfusion need is decided from bleeding rate, circulation and signs, rather than a single haematocrit result.

Bleeding associated with clotting factor deficiency may require frozen plasma. Antiemetics can control vomiting. Pain can be treated with an opioid painkiller when needed, for example. Your vet chooses medication according to your dog's condition and the cause of bleeding.

The ulcer is treated and its cause removed

A bleeding ulcer is usually treated with a proton pump inhibitor to reduce stomach acid secretion. This reduces acid exposure of the damaged lining and supports healing. Ulcer treatment is often prolonged, although the optimal duration for dogs is not precisely known. Guidance on duration is based partly on human recommendations.

Proton pump inhibitors reduce acidity more effectively than histamine H2-receptor blockers. Combining these medicine groups has not shown added benefit. Sucralfate binds to the surface of damaged lining. Its added benefit alongside a proton pump inhibitor has not been demonstrated.

If an NSAID is suspected of causing bleeding, stop it and contact your vet. A foreign body causing bleeding may need surgical removal. Immune-mediated platelet destruction may require immunosuppressive treatment. A perforated ulcer requires surgery. Surgery may also be needed if medical treatment does not stop the problem.

Bleeding caused by Addison's disease requires hormone replacement for that disease.

Bloody diarrhoea does not automatically require antibiotics

Antibiotics are not recommended for mild bloody diarrhoea in an otherwise well dog without systemic signs. In severe illness, antibiotics are considered if systemic signs persist despite appropriate fluid therapy. Bleeding with perforation, sepsis or severe mucosal barrier damage differs from minor bloody diarrhoea in an otherwise well dog.

Prevention

Prevention considers NSAIDs and the ulcer risk associated with tumours and liver disease. Do not give human painkillers without your vet's instructions. Medicine prescribed for another dog may also be unsuitable. Avoid combining two NSAIDs or an NSAID with a corticosteroid.

Long-term NSAID treatment includes tests and monitoring planned by your vet. Acid suppressants are not automatically prescribed for every dog with liver or kidney disease without other factors increasing ulcer risk.

Store medicines in closed containers out of your dog's reach to prevent accidental ingestion or overdose.

Important for dog owners

Record when blood first appeared, whether it was in vomit or stools and how your dog's condition changed. If possible, photograph unusual vomit or stools to show at the appointment. Compile a list of all medicines, supplements and substances possibly swallowed accidentally. Also report nosebleeds, blood in urine or new bruising.

At discharge, agree on feeding, medication management and the timing of repeat blood tests. Record eating, vomiting, stool colour and energy levels together at home. Renewed heavy bleeding or rapid deterioration needs urgent assessment.

Frequently asked questions

Are black stools always blood?

Black, tarry stools may contain digested blood, called melaena. Activated charcoal, iron and some medicines can also darken stools. Tell your vet about medication and substances eaten. Stool colour is assessed alongside your dog's condition, blood count and other investigations.

Can a dog be bleeding without visible blood?

Occult bleeding cannot be seen with the naked eye. Prolonged blood loss can cause iron-deficiency anaemia. In a group of 89 bleeding patients, 24 dogs had occult bleeding. The blood urea nitrogen-to-creatinine ratio has not proved sufficiently useful for identifying this situation.

Does fresh blood in stools always come from the colon?

Fresh, bright blood usually comes from the colon, rectum or anal area. However, heavy bleeding higher in the gastrointestinal tract can speed passage enough for blood to appear red. Imaging and endoscopy are therefore used to locate bleeding when needed.

Does bleeding always need surgery?

Most gastrointestinal bleeding can be managed medically. However, a perforated ulcer requires surgery. A foreign body, tumour or bleeding unresponsive to treatment may also lead to surgery. Stabilising circulation and, when necessary, transfusion may be needed before the procedure.

How long does treatment for a bleeding stomach ulcer take?

Guidance on ulcer treatment duration is based partly on human treatment data. The optimal treatment duration in dogs is not precisely known. The underlying cause is addressed at the same time. Your vet assesses recovery and further care using test results.