Diarrhea is a common presenting complaint in veterinary medicine, affecting ≈7% of dogs presented to small animal practices (Figure).1 Uncomplicated acute diarrhea is typically associated with dietary indiscretion, adverse food reactions, parasites, or bacterial or viral infections. The cause often remains unidentified; however, clinical signs typically resolve independently and rarely recur. In a study of >3,000 dogs with acute diarrhea in a primary care setting, 84% of dogs had mild clinical signs, 15% had moderate signs, and <1% had severe signs.2 A clinical classification scheme has been developed to guide diagnostics and treatment for dogs with acute diarrhea and minimize unnecessary antibiotic use (Table 1).3 Initial diagnostics for mild cases may include baseline data (eg, packed-cell volume, total solids) and fecal examination for parasites.
FIGURE Dog with moderate acute hemorrhagic diarrhea syndrome managed with a rectal catheter
Ask the Expert: How should veterinary patients with acute GI disease be managed?
Initial Treatment
Initial treatment should include supportive medication (Table 2).4-7 Antiemetics (eg, maropitant, ondansetron) are recommended for hyporexia or anorexia, lip smacking, hypersalivation, and/or vomiting. Dipyrone (ie, metamizole) or acetaminophen (ie, paracetamol; dogs only) can be given for outpatient treatment of abdominal pain. Gabapentin or tramadol can be used as oral alternatives for pain management, although gabapentin is primarily indicated for neuropathic pain and can cause sedation, and the variable metabolism and palatability of tramadol may limit efficacy. Opioids (eg, buprenorphine) can be beneficial for hospitalized patients.
Little to no evidence is available for use of over-the-counter antidiarrheals (eg, clay-based products, bismuth subsalicylate) in dogs and cats. Bismuth products have gastroprotectant, antiendotoxic, and weak antibacterial properties in humans, but studies have not been performed in dogs and cats. Bismuth subsalicylate should be used with caution in dogs and avoided in cats because of potential for increased salicylate absorption, and doses in dogs should not exceed 0.25 to 2 mL/kg PO every 8 hours. Routine use of clay-based products (eg, montmorillonite, kaolin) for management of acute diarrhea in dogs and cats is not recommended, as robust clinical data demonstrating a therapeutic benefit are lacking.
NSAIDs should be avoided because of adverse effects on the intestinal barrier, and opioid use should be minimized to prevent decreased GI motility.8,9 GI protectants (eg, proton pump inhibitors) should be reserved for patients with GI hemorrhage and are not considered standard therapy for patients with GI clinical signs.10
Meta-analysis conducted by the European Network for Optimization of Veterinary Antimicrobial Treatment of antimicrobial use in dogs supports that antibiotics are not recommended for dogs with mild or moderate disease.3 For severe cases, parenteral antibiotics (eg, IV ampicillin, IV amoxicillin/clavulanate, IV ampicillin/sulbactam [if not available, IM sulfa-/trimethoprim]) may be considered to treat sepsis caused by translocated bacteria but not to treat diarrhea.3
Dehydrated patients should be hospitalized and administered IV electrolyte-balanced infusions based on hydration status, maintenance requirements, and losses.
Dietary adjustments may be beneficial for most patients (see Diet).
How to Address Clients Who Expect Antibiotics
Explaining a lack of clear indication for antibiotic use can be hard, especially when clients expect to receive a prescription and have seen other doctors routinely use antibiotics for acute diarrhea.
When other treatments will be prescribed before antibiotics, the approach can be framed as delayed prescribing rather than not prescribing. If the patient does not improve with initial treatment, antibiotics may be a reasonable option based on clinical signs and/or test results.
For more details on delayed prescribing and other ways to balance antimicrobial stewardship and client satisfaction, visit Top 5 Antimicrobial Stewardship Practices.
Options When Initial Treatment Is Ineffective
Uncomplicated diarrhea typically lasts 4 to 5 days.3 Expected disease progression should be outlined to pet owners. If a patient’s condition worsens (eg, anorexia, mental deterioration, weakness), follow-up examination is needed to determine whether the initial acute illness was a recurrence of chronic enteropathy, as treatment for these conditions varies. Evaluation of the dysbiosis index and cobalamin and folate concentrations may be helpful.11,12 Extraintestinal causes should be ruled out via urinalysis and measurement of liver enzyme activities, serum bile acids, creatinine, and urea in dogs and cats, as well as basal cortisol in dogs (to exclude hypoadrenocorticism) and thyroxine in cats (to exclude hyperthyroidism).13 Abdominal ultrasonography should be performed to determine whether concurrent disease (eg, pancreatitis) is affecting other organs.
If the patient’s condition does not improve, further treatments may be needed, including dietary fiber supplements (eg, cellulose or psyllium husk, 0.5 g/kg [0.5 teaspoon/kg] per day).14 A second dietary change (eg, to a high-fiber or novel-protein diet) may also be beneficial. Meta-analysis did not find additional benefits associated with probiotics (eg, Lactobacillus spp, Bifidobacterium spp, Enterococcus faecium) used in conjunction with dietary change; however, probiotics may have anti-inflammatory effects in the intestines or may displace pathogens.15-17 If diagnostic tests reveal additional underlying conditions (eg, liver failure, severe nephropathy, hypoadrenocorticism, hyperthyroidism), targeted treatments should be administered.
Spectrum of Care Spotlight
Diarrhea occurs in most animals but is usually mild and brief, so it is understandable that not every client is prepared to spend a lot of money and/or time to diagnose the cause. Sometimes finances are the barrier, but education, personal experience, and other caretaking responsibilities can also play a role in a client’s willingness to pursue diagnostic or treatment plans.
Conversations should be free of judgment and approached with the assumption that the client and veterinary team have the same goal: to help the patient feel better and stay healthy as long as possible. Although true evidence-based recommendations can be difficult in cases in which finances or other barriers limit care, clinical judgment and experience can help narrow down what is essential for the patient. For example, if a dog is not receiving regular parasite preventives, a fecal examination may be an inexpensive and important first step.
For more content on spectrum of care, including concerns about recordkeeping and legal implications, visit our Spectrum of Care center.
Fecal Testing
Fecal testing for parasites may have limited utility in adult dogs and cats with acute diarrhea that live in regions where regular deworming is performed, as deworming effectively minimizes clinically significant parasitic burdens. Fecal shedding of Giardia spp is frequently subclinical, and helminthic or protozoal infections are relatively rare causes of acute diarrhea in adults. Fecal examination should, however, be considered if deworming practices are inconsistent or less routine. In addition, distinguishing subclinical shedding of Giardia spp from clinically relevant infection in dogs with GI signs requires evaluation of additional factors, including persistent or severe diarrhea and response to treatment of clinical signs alone. Fecal examinations are crucial for cases of acute diarrhea in young patients because clinically relevant parasitic burdens are more common in this population.
Testing for bacterial enteropathogens is not beneficial and should be avoided, as incorrect conclusions regarding therapy (eg, unnecessary use of antibiotics) are possible.18,19 Testing for viruses or viral toxins does not appear to be useful in most cases, as there is no therapeutic benefit and no evidence of relevance to acute diarrhea; testing for fecal parvoviral antigen in juvenile, inadequately vaccinated, or neutropenic patients is an exception.20
Diet
Dietary modification is a main therapeutic strategy for patients with acute GI disease; however, the efficacy of different diets has not been compared, making clear recommendations difficult. GI diets, high-fiber GI diets, hydrolyzed or novel-protein diets, and easily digestible diets prepared by owners (eg, chicken and rice) are reasonable options (Table 3). Choice of diet for an individual patient depends on owner finances, as well as owner and patient preference.
Options When Initial & Secondary Treatments Are Ineffective
Patients with diarrhea lasting >7 days are considered to have subchronic disease (ie, diarrhea lasting 1-3 weeks). More intensive diagnostics (eg, imaging) should be performed to rule out rare (eg, subchronic intussusception) and extraintestinal causes, and laboratory results should be monitored. Measurement of basal cortisol in dogs, trypsin-like immunoreactivity in dogs and cats, and serum bile acids in dogs and cats can help rule out hypoadrenocorticism, pancreatic insufficiency, and hepatic insufficiency. Gastroduodenoscopy and colonoscopy with biopsies may help exclude other underlying causes (eg, neoplastic diseases, chronic enteropathies). Treatment should be adjusted based on test results.
Glucocorticoids (eg, budesonide, 1-3 mg/dog or 0.5-1 mg/cat PO every 24 hours; prednisolone, 0.5-2 mg/kg PO every 24 hours) and repeated fecal transplantation may be considered in patients with subchronic disease. Administration of drugs (eg, antibiotics) without a clear indication should be avoided.