What Causes Bloody Diarrhea in Dogs? Unfortunately, diarrhea is a frequent reason why dogs are seen by their vet. We recognize it by our dog’s frequent trips outside, which often result in watery, mucousy, or sometimes bloody stool. If your dog is having diarrhea and you’re worried about the presence of blood, contact your vet and keep reading to learn more about the possible cause. Are you concerned about your pet?Book a video consultation with an experienced veterinarian within minutes.Professional vet advice onlineLow-cost video vet consultationsOpen 24 hours a day, 365 days a year Book Video Consultation What should I look for if my dog has bloody diarrhea?If you’re noticing blood in the stools, it’s important to differentiate between fresh blood (bright red streaks or blobs) or digested blood (often dark or tarry feces). Fresh blood is usually produced by the large bowel (large intestine), while digested blood is indicative of bleeding in the stomach or small intestine. The color-wheel of poop is a useful guide!Causes of Bloody Diarrhea in DogsIn theory, anything that causes diarrhea can also cause bloody diarrhea. The common causes of diarrhea are discussed in this article. From here, let’s discuss which of these are most likely to cause or progress to bloody stools.1. Irritation of the large bowel by foreign, indigestible materialsIndigestible items that are passed into the large intestine are formed into stools. These items are passed along the large bowel and, particularly if they have rough or sharp edges, can act like sandpaper on the lining of the bowel. Ouch!In some cases, this indigestible material causes bleeding inside the intestines. This is often seen as red streaks or blobs in your dog’s feces. A condition called “colitis” is diagnosed when small amounts of soft, bloody, and/or mucousy stool is produced.Although this diagnosis can have a range of causes, the most common is mechanical irritation. Luckily, this is often corrected with a bland diet and sometimes a medication prescribed by your vet.2. Inflammatory Bowel Disease (IBD)IBD can also cause the signs of colitis described above. However, these symptoms reappear frequently or may be unresponsive to common treatments. IBD can be triggered by the body’s own immune system and/or food intolerance.3. ParvovirusParvovirus is a serious viral infection, often seen in unvaccinated puppies. It causes bleeding throughout the intestines and often causes digested (darky or tarry) blood to be passed. It is a serious condition with a high mortality rate and veterinary treatment must be sought quickly.4. Rectal PolypsRectal polyps are usually benign and treatable with surgery but can cause streaks of fresh blood in the stools. The blood will not respond to standard treatments for diarrhea.5. TumorsTumors of the small and large intestine are uncommon but certainly can cause bloody diarrhea (both types).6. MedicationsSome medications (prescription and over-the-counter) can cause irritation and bleeding in the stomach or intestines. Care should be taken to examine stools regularly if your pet is on anti-inflammatories or antibiotics.Although bloody diarrhea can be alarming, it is often treatable with a few simple remedies. Always consult a vet if your pet has diarrhea, with or without blood. But, if your dog is otherwise happy, active, and has a good appetite, check out some of these Home Remedies while you’re waiting for your appointment!Read more:Gastrointestinal Diets for Dogs and CatsWhat foods are toxic to dogs? Need to speak with a veterinarian regarding your dog's stool or another condition?Click here to schedule a video consult to speak to one of our vets. You can also download the FirstVet app from the Apple App Store and Google Play Stores.