Definition

Abrupt or recent onset of abnormally increased fecal water and/or solid content.

Pathophysiology

• Caused by imbalance in the absorptive, secretory, and/or motility actions of the intestines.
• Mechanisms of diarrhea: (1) Osmotic-excess molecules in the intestinal lumen draw in water, overwhelming the intestinal absorptive capacity (e.g., diet changes, malabsorption or overeating). (2) Secretory-stimulation of small intestinal secretion that overwhelms the intestinal absorptive capacity (e.g., toxins). Stimulation of the parasympathetic nervous system or exposure to a variety of secretagogues can increase intestinal secretion. (3) Exudative/permeability-leakage of tissue fluid, serum proteins, blood, or mucus from sites of infiltration or ulceration. (4) Dysmotility-hypomotility (ileus) is more common than hypermotility. Hypermotility can be primary (irritable bowel syndrome) or secondary (obstruction, malabsorption leading to intestinal distention). (5) Mixed.

Systems Affected

• Cardiovascular-hypovolemia, tachycardia, pale mucous membranes, prolonged CRT and weak pulses; hypokalemia can cause arrhythmias.
• Endocrine/Metabolic-electrolyte and acid–base abnormalities, dehydration, and prerenal azotemia.
• Gastrointestinal-abdominal pain, hypokalemia can lead to decreased motility.
• Musculoskeletal-hypokalemia can lead to muscle weakness.

Genetics

No genetic basis

Incidence/Prevalence

Acute diarrhea is more common in younger animals and is more likely to resolve on its own. A fairly common problem, especially in dogs with dietary indiscretion.

Geographic Distribution

Some infectious causes (e.g., salmon poisoning) may be regional.

Signalment

• Dogs and cats.
• Any animal can suffer from acute diarrhea; kittens and puppies are most frequently affected.

Signs

Causes

• Systemic illness may also result in diarrhea as a secondary event.
• Dietary indiscretion-ingestion of garbage, non-food material, or spoiled food.
• Dietary changes-abrupt changes in amount or type of foodstuffs.
• Dietary intolerance-malassimilation of food, dietary hypersensitivity.
• Metabolic diseases-hypoadrenocorticism, liver disease, renal disease, and pancreatic disease can cause acute or chronic diarrhea.
• Obstruction-foreign bodies, intussusception, or intestinal/mesenteric volvulus.
• Idiopathic-hemorrhagic gastroenteritis.
• Viral-parvovirus, coronavirus, rotavirus, canine distemper virus.
• Bacterial-Salmonella, Campylobacter, Clostridium spp., Escherichia coli, etc.
• Parasitic-verminous (hookworms, ascarids, whipworms, and cestodes) or protozoal (Giardia, coccidia, Tritrichomonas and Entamoeba).
• Rickettsial-Salmon poisoning (Neorickettsia).
• Fungal-histoplasmosis.
• Drugs and toxins-heavy metals (e.g., lead), organophosphates, nonsteroidal anti-inflammatories, steroids, antimicrobials, antineoplastic agents, etc.

Risk Factors

Young dogs and cats present for diarrhea from dietary indiscretion, intussusception, foreign bodies, and infectious causes more often than older patients.

Differential Diagnosis

• Patients should have a complete physical examination, fecal flotation, and assessment of their hydration status.
• Further diagnostic tests depend on the extent of illness and other clinical signs.

CBC/Biochemistry/Urinalysis

• Generally normal; not necessary unless systemic involvement.
• Can see neutropenia with parvoviral enteritis and marked hemoconcentration with a discordant normal or low-normal plasma protein concentration with C. perfringens and C. difficile-associated hemorrhagic diarrhea.
• Electrolytes are commonly abnormal because of intestinal losses (hypokalemia, hypochloremia, hyponatremia).

Other Laboratory Tests

• Spec cPL (pancreatitis), TLI (EPI), cobalamin, and folate (altered absorption)-the latter are more commonly performed with chronic diarrhea.
• ELISA and IFA fecal testing is available for Giardia and Cryptosporidium spp.
• Diarrhea PCR panel-to evaluate for common specific infectious diseases (e.g., Salmonella, Parvovirus)

Imaging

• Radiographs-generally not necessary in patients with mild illness.
• Abdominal radiographs can help identify or rule out intestinal foreign bodies or obstruction.
• More severe signs (e.g., abdominal pain or persistent vomiting) may increase the likely diagnostic benefit of abdominal imaging.
• Contrast abdominal radiography and ultrasonography may be useful with some patients, especially looking for an obstruction.

Diagnostic Procedures

• Perform fecal flotation for parasites on all patients.
• Because helminth ova and Giardia cysts can be shed in low numbers or intermittently, multiple fecal analyses are recommended, and empiric treatment is advisable. The Giardia ELISA is a sensitive assay and should be combined with fecal flotation to increase the diagnostic yield of Giardia spp.
• Can perform fecal ELISA tests for parvovirus antigen in dogs.
• Endoscopy and biopsy-useful in select cases; more commonly needed in chronic diarrhea.

Pathologic Findings

Dependent on etiology

Appropriate Health Care

Depends largely on the severity of illness; patients with mild illness can often be handled as outpatients with symptomatic therapy; patients with more-severe illness or that fail to respond to therapy should be treated more aggressively.

Nursing Care

• Fluid therapy and correction of electrolyte imbalances is the mainstay of treatment in most cases.
• Can give crystalloid fluid therapy (PO, SC or IV) as required.
• Aim to return the patient to proper hydration status (over 12–24 hours) and replace ongoing losses.
• Severe volume depletion can occur with acute diarrhea; aggressive fluid therapy may be necessary.
• Use potassium supplementation (potassium chloride 20–40 mEq/L) in most patients, but not during shock fluid therapy. Hypokalemia can worsen ileus.

Activity

Animals should have limited activity until the diarrhea has stopped.

Diet

Patients with mild illness that are not vomiting can be managed with a fat-restricted, digestible intestinal diet, either homecooked (boiled rice and chicken in 4:1 ratio) or low-fat cottage cheese (1%) and rice or a commercial prescription intestinal diet.

Client Education

• Limiting exposure to garbage, foods other than the patient's normal diet, and potential foreign bodies.
• Proper puppy and kitten vaccination and deworming schedules.

Surgical Considerations

Patients with obstructions may require surgery to evaluate the intestine and remove the foreign objects.

Drug(s) Of Choice

• Antidiarrheal drugs can be classified as motility-modifying drugs, antisecretory drugs, or intestinal protectants.
• Motility-modifying drugs generally operate by increasing segmental motility and thus increasing transit time (i.e. narcotic such as loperamide; 0.1 mg/kg PO q8–12h in dogs; 0.08 mg/kg PO q12h in cats) or by decreasing forward motility (i.e., anticholinergics); these medications are not necessary in mild disease, as it is generally self-limiting. Do not use these medications longer than 1–2 days because of adverse effects.
• Acute diarrhea that does not resolve with antidiarrheal drugs merits further investigation.
• Anthelmintics (e.g., fenbendazole 50 mg/kg PO q24h for 5 days) and antiprotozoal drugs (e.g., metronidazole 10–20 mg/kg PO q12h for 5 days) are recommended as empiric treatment for patients with acute diarrhea or those with positive fecal analyses. Can use coccidiostatic (e.g., sulfadimethoxine, ponazuril) drugs if fecal analysis warrants.
• Antibiotic therapy is unnecessary for most cases of mild illness and may actually exacerbate the diarrhea.
• Patients with bacterial enteritis, severe illness, concomitant leukopenia, or suspected breakdown of the gastrointestinal mucosal barrier (as evidenced by blood in the feces) should be treated with antimicrobial agents.
• Probiotics may also be useful (Lactobacillus, Enterococcus). Probiotics have been shown to shorten the duration of acute, nonspecific diarrhea in some studies. Use probiotics from premium pet food companies in light of studies showing suboptimal quality of probiotics that have not undergone rigorous testing.

Contraindications

• Anticholinergics in patients with suspected intestinal obstruction, glaucoma, or intestinal ileus.
• Narcotic analgesics-can cause CNS depression; undesirable in patients with more severe illness that are already depressed or lethargic.
• Narcotic analgesics in patients with liver disease and bacterial or toxic enteritis.

Precautions

• Most cases of acute mild diarrhea resolve with minimal treatment; be cautious of excessive diagnostics and overtreating.
• Almost any drug can produce adverse effects (often including diarrhea and vomiting); these may be more severe than the initial problem.
• Cats can be sensitive to subsalicylates and should not be given high or frequent doses.

Possible Interactions

• Long term use of metronidazole can lead to neurologic complications.
• Some animals are sensitive to sulfa containing mediations used for treatment of Coccidia.

Alternative Drug(s)

Kaolin pectin

Patient Monitoring

• Most acute diarrhea resolves within a few days.
• If clinical signs persist, additional diagnostics and treatments may be necessary.
• Upon completion of medication, recheck patients that exhibited parasites by fecal analysis.

Prevention/Avoidance

• Animals should be fed a consistent high-quality diet.
• Owners should attempt to control indiscriminant eating and monitor for foreign body ingestion.

Possible Complications

• Intussusception is thought to be associated with increased intestinal motility.
• Monitor for this complication in patients with acute diarrhea, especially young dogs with parvoviral enteritis and parasitism.

Expected Course and Prognosis

Most cases of acute diarrhea resolve spontaneously without treatment or with minimal treatment.

Associated Conditions

Acute vomiting commonly occurs concurrently with acute diarrhea.

Age-Related Factors

• Young dogs and cats present for diarrhea from dietary indiscretion, intussusception, foreign bodies, and infectious causes more often than older patients.
• Younger and smaller animals are also more prone to dehydration and may require more-aggressive fluid therapy.

Zoonotic Potential

• Campylobacter jejuni is a zoonosis; however, most other Campylobacter spp. are non-pathogenic.
• Some strains of Giardia are zoonotic; however, this is uncommon.
• Parasitic larvae can cause visceral larval migrans (ascarids) and cutaneous larval migrans (hookworms) in humans, particularly children.

Pregnancy/Fertility/Breeding

Always be cautious using medication in pregnant animals.

See Also

• Diarrhea, Antibiotic Responsive
• Vomiting, Acute

Abbreviations

• CNS = central nervous system
• CPV = canine parvovirus
• CRT = capillary refill time
• ELISA = enzyme-linked immunosorbent assay
• EPI = exocrine pancreatic insufficiency
• Spec cPL = canine pancreatic lipase
• TLI = trypsin-like immunoreactivity

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