Differential Diagnosis of Vomiting and Diarrhea in Cats

Cat vomiting and diarrhea are among the most common signs that veterinary professionals encounter in feline patients. While these signs might seem straightforward, they can stem from a wide variety of causes, ranging from minor dietary indiscretions to serious systemic diseases.

A methodical diagnostic approach is crucial in determining whether the issue originates in the gastrointestinal (GI) tract or results from a systemic disorder. 

This article will explore the differences between vomiting and regurgitation, how to distinguish small from large intestinal diarrhea, the potential causes, diagnostic strategies, and treatment options. 

Vomiting vs. Regurgitation: Understanding the Difference

One of the initial steps in assessing a cat with suspected GI disease is to distinguish vomiting from regurgitation. Although both are the expulsion of fluid or food, they occur through different mechanisms and represent different pathological conditions.

What is Vomiting?

Vomiting is an active process characterized by abdominal contractions and often preceded by signs such as hypersalivation and lip licking. The expelled material may contain partially digested food, bile, mucus, or even blood, depending on the underlying cause.

Common causes of vomiting in cats include:

• Dietary indiscretion (ingestion of inappropriate or spoiled food)
• Gastrointestinal infections (bacterial, viral, parasitic)
• Toxin ingestion (plants, chemicals, medications)
• Systemic diseases (chronic kidney disease, liver disease, hyperthyroidism)
• Inflammatory bowel disease (IBD)
• Gastrointestinal obstructions (foreign bodies, tumors)

What is Regurgitation?

Regurgitation, on the other hand, is a passive process in which undigested food or fluid moves back up from the esophagus without forceful abdominal effort, usually soon after a meal. It is not triggered by nausea or retching and usually comes from the esophagus, not the stomach.

Common causes of regurgitation include:

• Megaesophagus (dilated esophagus leading to poor food motility)
• Esophageal strictures (narrowing due to scarring or inflammation)
• Foreign bodies lodged in the esophagus
• Neuromuscular disorders affecting esophageal function

Small vs. Large Intestinal Diarrhea: How to Distinguish?

In the assessment of vomiting and diarrhea in cats, one needs to ascertain if the condition is coming from the small or large intestine.

Small Intestinal Diarrhea

Diarrhea from the small intestine typically presents as:

• Large stool volumes
• Weight loss due to malabsorption
• Melena (black, tarry stools) indicating digested blood
• Minimal urgency to defecate

Large Intestinal Diarrhea

Diarrhea from the large intestine tends to cause:

• Frequent defecation with small stool volumes
• Fresh blood (hematochezia) in the stool
• Mucus in the stool
• Straining and urgency to defecate

For a deeper understanding of similar gastrointestinal issues in canines, you may also find our article on Chronic Diarrhea in Dogs insightful.

Common Causes of Vomiting and Diarrhea in Cats

1. Dietary Causes

Cats have delicate digestive tracts, and acute vomiting and diarrhea can be caused by a sudden change in diet or the ingestion of improper food.

Clinical Signs

• Vomiting of partially digested food
• Loose, watery, or semi-formed stools
• Abdominal bloating and discomfort
• Temporary loss of appetite

Diagnosis & Treatment

• History & physical exam to rule out infectious causes
• Supportive care, including temporary fasting (typically not exceeding 12 hours in adult cats).
• Reintroduction of a bland diet (boiled chicken and rice)
• Probiotics to restore gut flora
• Electrolyte replacement in dehydrated cases

2. Food Allergies and Intolerances

A few cats develop persistent vomiting and diarrhea as a result of immune responses to certain proteins. In contrast to dietary indiscretion, food allergies are recurrent and persistent.

Diagnosis & Treatment

• Elimination diet test (8–12 weeks on a new protein or hydrolyzed diet).
• Strict dietary modification, permanently avoiding trigger ingredients.

3. Infectious Causes (Bacterial & Viral)

Bacterial infections in cats may result in very serious gastrointestinal signs with bloody diarrhea, vomiting, fever, and dehydration. Salmonella, Clostridium perfringens, Campylobacter, and Escherichia coli are the most frequently isolated bacterial pathogens of feline gastroenteritis.

Viral Infections (Panleukopenia, Feline Coronavirus, FIP)

Feline panleukopenia virus (FPV), or feline distemper, is a highly contagious viral illness causing abdominal vomiting, hemorrhagic diarrhea, fever, and leukopenia (white blood cell loss). Infected animals lose condition, become dehydrated and recumbent, and refuse food and water.

None of these viral infections have a specific antiviral treatment, and supportive therapy becomes crucial. Intravenous hydration, nutritional supplements, and antibiotics for secondary infection may be indicated.

Chronic Gastrointestinal Disorders

Chronic vomiting and diarrhea may indicate inflammatory bowel disease (IBD) or chronic enteropathy (CE). Both involve persistent GI inflammation, though their causes may differ.

Other Causes of Diarrhea and Vomiting in Cats

Gastrointestinal Obstructions

Intestines can become obstructed by foreign bodies (toys, hairballs, string), which causes vomiting, pain, and failure to produce stool.

Diagnosis & Treatment

• X-rays or ultrasounds confirm obstruction.
• Emergency surgery (enterotomy/gastrotomy) if blockage persists.

Systemic Diseases (Kidney & Liver Disease, Hyperthyroidism)

Systemic diseases (chronic kidney disease, liver disease, hyperthyroidism) can cause chronic vomiting and diarrhea.

Final Words

Feline vomiting and diarrhea can result from various causes, ranging from simple gastrointestinal disturbance to profound systemic illness. Comprehensive diagnostic investigation in the form of dietary trials, laboratory testing, imaging, and fecal analysis is important for successful management.

Would you like to increase your skillset in diagnosing and treating feline chronic enteropathy? Watch our Free Online Veterinary CE Webinar on feline chronic enteropathy.