Causes of diarrhea in older dogs



Diarrhea in older or elderly dogs is a frequent reason for a small animal clinic consultation. It is a clinical sign that can appear associated with multiple diseases, not only in the gastrointestinal tract but also associated with other organs and systems. Determining the specific cause of diarrhea will be necessary to establish a specific treatment and control the process.

If you want more information about diarrhea in older dogs, its causes, and what to do, we recommend that you continue reading the following dog57 article. 

What are the types of diarrhea in older dogs?

Before addressing the different causes that can cause diarrhea in older dogs, we need to differentiate between the types of diarrhea that exist.

Depending on the continuity of the process, we are talking about:

Acute diarrhea that lasts less than 3 weeks. They have a strikingly rapid development, which is usually accompanied by putrefaction and the generally poor condition of the animal.

Chronic diarrhea: lasting more than 3 weeks. Intermittent diarrhea is also included in this group. They progress slowly and the general condition of the animal gradually deteriorates.

In addition, depending on the affected intestinal section, diarrhea can also be classified into:

Diarrhea of ​​the small intestine: It is light brown or yellowish in color, the stool increases in size and may show undigested food, foam, digested blood (melena), or fat (steatorrhea).

Large intestine diarrhea: It usually presents with normal color and fresh mucus and/or blood. In this case, the size of the stool is normal, but the frequency of defecation increases.

Knowledge of the chronicity of diarrhea and of the intestinal segment affected will be essential to guide diagnosis in these animals. 

What is the most common cause of diarrhea in dogs?  

Inflammatory bowel disease or inflammatory bowel disease
Inflammatory bowel disease is one of the most common causes of chronic diarrhea in adult dogs and the elderly. It includes a group of diseases characterized by the development of an inflammatory response at the level of the intestinal mucosa. This inflammatory process prevents the absorption of nutrients in the intestine, which increases osmotic pressure at the level of the intestinal lumen, retains water, and causes chronic diarrhea.

To date, it is considered a disease of unknown etiology, that is, of unknown origin. It is believed to be a multifactorial process in which immune, allergy, diet, or dysplastic mechanisms may be involved, although it is not fully known. However, it should be noted that E. coli bacteria have recently been found to be involved in histiocytic ulcerative colitis in boxers.

IBD can affect the small intestine (SI), large intestine (GI), or even both parts:
Small IBD: Chronic diarrhea (with watery, mustard-colored stools), biliary vomiting on an empty stomach, weight loss, and chronic abdominal pain may be seen. Abdominal pain can appear in the form of analgesic positions (prayer position) or in the form of seizures (which can be confused with epileptic seizures)

Major inflammatory bowel disease: Patients with chronic IG diarrhea (with copious mucus and fresh blood), tenesmus (persistent urge to defecate), increased bowel movements, but vomiting and weight loss usually do not occur in this condition.

For a definitive diagnosis of IBD, it is necessary: 

Endoscopy of the affected part of the intestine.

Taking a biopsy of the affected intestinal mucosa for tissue analysis.

The therapeutic management of IBD relies on two pillars:

Diet therapy: A low-fat, low-fiber diet should be eaten with hydrolyzed protein and a 1:5 or 1:10 ratio of omega-3:omega-6 fatty acids.

Pharmacotherapy: It is based on the use of immunosuppressive drugs and anti-inflammatories. The treatment of choice for both types of IBD is prednisone. However, there are other medicines such as cyclosporine, azathioprine, metronidazole, or sulfasalazine, which can be used alone or in combination to treat IBD. In the specific case of the boxer's histiocytic ulcerative colitis, the treatment of choice is the antibiotic enrofloxacin, in which Escherichia coli is involved.

intestinal tumors

Intestinal tumors are another cause of chronic diarrhea in adult dogs and the elderly.

As in inflammatory bowel disease, tumors are also classified according to the section of the intestine in which they affect. In this way we find:
Tumors of the small intestine: especially carcinomas and lymphosarcoma. Both cause chronic diarrhea, vomiting, change in appetite, weight loss, and abdominal pain.

Tumors of the large intestine: can be adenomas, carcinomas, lymphosarcoma, leiomyomas, leiomyosarcomas, or stromal tumors. In these tumors, the presence of fresh mucus and blood in the stool, dysuria (pain when defecation), and tenesmus (a constant need to defecate) can be observed.
The final diagnosis is made by biopsy and histopathological analysis of tissues, as this is the only way to know exactly what type of tumor the animal shows. A biopsy sample can be obtained by endoscopy or exploratory laparotomy.

Treatment depends on the type of intestinal tumor, although it is generally summarized in two strategies: 

Surgical removal: in the case of adenomas and carcinomas. The prognosis is good after surgery.

Chemotherapy: in lymphosarcoma. In these cases, despite treatment, the diagnosis is maintained. 

intestinal polyps 

Intestinal polyps are hyperplastic polyps of non-cancerous origin that usually appear in the mucous membrane of the colon or rectum, and sometimes in the small intestine. They are single or multiple pedunculated masses, which usually show ulcerated gastrointestinal mucosa.

These benign tumors frequently appear in middle-aged dogs and can produce the following symptoms:
Chronic diarrhea.

Tenesmus: the constant need to defecate.
Hematochezia: bleeding in the rectum.
Melena: dark-colored stools due to the presence of digested blood.

Its diagnosis requires endoscopy, biopsy, and histopathological analysis to confirm that it is a non-neoplastic lesion.

The treatment of polyps in the intestine is surgical and consists of removing the affected part of the intestine.

chronic kidney disease 

Chronic kidney disease is a disease characterized by the progressive and irreversible loss of kidney function. It is one of the most important diseases that affect dogs of old age. So much so, that it is the third leading cause of death in these animals.

Although it is a disease that affects the kidneys, it produces very diverse symptoms that can affect multiple organs and systems, including the digestive system. Among other things, in dogs with chronic kidney disease, there is an accumulation of urea and creatinine in the blood (azotemia), which can lead to the appearance of diarrhea.

Although it is an incurable disease, renal prophylaxis should be initiated to slow the progression of the disease, as well as symptomatic treatment to relieve the animal's clinical signs (including diarrhea). Specifically, the therapeutic management of chronic kidney disease includes:

Medical treatment: The electrolyte balance and acid-base balance should be restored by fluid therapy, as well as the treatment of hypertension with vasodilators.

Nutritional therapy: A "renal diet" should be provided that contains high levels of omega-3 fatty acids, antioxidants, and soluble fiber, as well as low levels of sodium, phosphorous, and protein.

Liver diseases

Bile salts are essential for the formation of micelles and absorption of fats at the intestinal level. When there is liver disease that reduces the production of bile salts or prevents bile from reaching the intestine (cholestasis), proper digestion of fats does not occur and a picture of diarrhea appears in the small intestine.

Specifically, diarrhea usually presents with other nonspecific clinical signs (such as vomiting, frequent urination, polydipsia, or weight loss) in the initial stage of the disease, before symptoms suggestive of liver disease (such as jaundice, ascites, or hepatic encephalopathy) appear. . ).

Therapeutic management in this case is aimed at determining a specific treatment for diseases of the liver or bile ducts that cause diarrhea, and may include:

Pharmacological and/or surgical treatment.

Liver protectors: such as ursodeoxycholic acid, silymarin, etc.
Diet management: a specific diet should be tailored to each patient, although in general it will be an easily digestible diet rich in easily digestible carbohydrates and moderate in fat.

exocrine pancreatic insufficiency

The etiology that we must not forget in dogs with diarrhea is exocrine pancreatic insufficiency. During this disease, there is a deficit in the synthesis and secretion of pancreatic enzymes necessary for the digestion of carbohydrates, proteins, and fats.

The lack of these enzymes prevents nutrients from being digested and absorbed, resulting in dyspepsia and malabsorption syndrome. As a result, the following symptoms may be observed:

Chronic diarrhea in the small intestine.
Noticeable weight loss.
River appetite: It is common for them to develop polyphagia, macrophages, and pica behavior.

Therapeutic management consists of the contribution of pancreatic enzymes mixed with food. It is a lifelong treatment, although the prognosis is good and animals usually improve significantly after starting given the enzymes.

other reasons

In this dog57 article, we describe the main reasons that can cause diarrhea in older dogs. However, other pathogens can also produce this clinical sign in dogs, regardless of their age:

Sudden changes in diet: Dogs have a digestive system that is particularly sensitive to changes in diet. For this reason, when we make a change from one feed to another, it is important to mix the new feed with the previous feed and to increase the amount of the new feed as the animal tolerates it. In the case of home rations, whenever new food is introduced, it should be done in small quantities

Improper diet: Diarrhea occurs frequently when caregivers share food with their pets. For this reason, the contribution of any food that is not part of the dog's usual diet should be avoided, to avoid the appearance of changes in the digestive system.

Infectious gastroenteritis: bacterial (such as salmonella) and viral (such as canine tuberculosis
Intestinal parasites: protozoa, nematodes, or nematodes, in those animals that do not deworm properly. 

This article is informational only, at we do not have the authority to prescribe veterinary treatments or make any kind of diagnosis. We invite you to take your pet to the vet in case he is under any kind of condition or discomfort.

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