Feline Ingestion of Poisonous Plants – NAVLE Study Guide

Overview and Clinical Importance

Plant toxicosis represents a significant cause of morbidity and mortality in cats, with lilies (Lilium and Hemerocallis species) being the most dangerous and frequently tested plant toxin on the NAVLE. Cats are uniquely susceptible to certain plant toxins, and the ASPCA Animal Poison Control Center reports that plant ingestions consistently rank among the top ten toxin exposures in felines. Understanding the clinical presentation, pathophysiology, and treatment of plant toxicoses is essential for every veterinarian.

Section 1: Lily Toxicosis - The Most Critical Plant Poisoning

Toxic Lily Species

The Lilium and Hemerocallis genera contain species that cause acute nephrotoxicity in cats. All parts of these plants are toxic, including petals, leaves, pollen, and even the water in the vase.

Nephrotoxic Lilies (TRUE Emergency)

Non-Nephrotoxic "Lilies" (Different Toxin Profiles)

Pathophysiology of Lily Nephrotoxicity

The exact nephrotoxic compound in lilies remains unidentified, but research has confirmed it is a water-soluble compound present in all parts of the plant. The aqueous fraction of flowers is more potent than leaf extract. The toxin is rapidly absorbed from the GI tract and targets the renal tubular epithelium, specifically the proximal convoluted tubules.

Key Pathologic Features:

• Acute tubular necrosis (ATN) affecting primarily proximal convoluted tubules
• Tubular epithelial cell degeneration with cytoplasmic vacuolation
• Sloughing of necrotic cells into tubular lumens forming casts
• Basement membrane typically remains INTACT (allows potential regeneration)
• Ultrastructural: Mitochondrial swelling, megamitochondria formation
• Pancreatic acinar cell degeneration may also occur

Timeline of Clinical Progression

Diagnosis

There is NO specific diagnostic test to confirm lily ingestion. Diagnosis is based on:

• History of known or suspected lily exposure
• Compatible clinical signs and timeline
• Clinicopathologic findings consistent with acute tubular necrosis
• Identification of plant material in vomitus or GI contents
• Post-mortem histopathology showing proximal tubular necrosis

Treatment Protocol

Decontamination (Within 2-6 hours)

• Emesis induction: If ingestion is recent and cat is not vomiting; use alpha-2 agonists (dexmedetomidine) or hydrogen peroxide (1-2 mL/kg, max 45 mL)
• Activated charcoal: 1-2 g/kg PO with a cathartic (sorbitol) after antiemetic administration
• Antiemetics: Maropitant 1 mg/kg SC or ondansetron 0.5 mg/kg IV before charcoal to prevent aspiration

Aggressive Fluid Therapy (Critical)

• IV fluid diuresis: 2-3x maintenance rate (approximately 4-6 mL/kg/hr) for minimum 48-72 hours
• Fluid type: 0.9% NaCl or Plasmalyte preferred; avoid lactated Ringer's if hyperkalemic
• Goal: Maintain urine production greater than 2 mL/kg/hr
• Monitor: Body weight, hydration status, respiratory rate, urine output (urinary catheter recommended)

Monitoring

• Serial renal values (BUN, creatinine) every 12-24 hours
• Electrolytes (especially potassium)
• Urinalysis including urine specific gravity
• Blood pressure

If Anuric Renal Failure Develops

• Peritoneal dialysis or hemodialysis may restore function if tubular basement membrane is intact
• Prognosis is guarded to poor once anuria develops

Prognosis

Section 2: Sago Palm (Cycad) Toxicosis - Hepatotoxicity

Overview

Cycad palms (Sago palm, Coontie palm, Cardboard palm) contain multiple toxins that cause severe hepatotoxicity. While more commonly reported in dogs, cats are also susceptible. All parts of the plant are toxic, but seeds contain the highest concentration of toxin. Even with aggressive treatment, mortality approaches 50%.

Toxic Principles

Clinical Signs

Early Signs (within 15 minutes to several hours):

• Vomiting (often severe and persistent)
• Diarrhea (may be bloody)
• Hypersalivation
• Abdominal pain

Late Signs (24-48+ hours - indicating liver failure):

• Icterus (jaundice)
• Coagulopathy (epistaxis, melena, petechiae)
• Ascites
• Hepatic encephalopathy (seizures, ataxia, altered mentation)
• Hypoglycemia

Treatment

• Decontamination: Emesis (if recent and asymptomatic), activated charcoal with cathartic
• IV fluid therapy: Support hydration and perfusion
• Hepatoprotectants: S-adenosylmethionine (SAMe), N-acetylcysteine, silymarin (milk thistle)
• GI protectants: Sucralfate, famotidine or omeprazole
• Antiemetics: Maropitant, ondansetron
• Coagulopathy management: Vitamin K1, fresh frozen plasma if needed
• Monitor: Liver enzymes, bilirubin, PT/PTT, blood glucose for 72+ hours

Section 3: Autumn Crocus (Colchicum autumnale) - Multisystem Toxicity

Overview

Autumn crocus (also called meadow saffron or naked lady) contains colchicine, a potent alkaloid that inhibits microtubule formation and cell division. This causes severe multiorgan toxicity with potential for bone marrow suppression. All parts of the plant are toxic, with leaves and seeds containing the highest concentrations.

Mechanism of Toxicity

• Colchicine binds tubulin and prevents microtubule polymerization
• Inhibits cell division, particularly affecting rapidly dividing cells
• GI epithelium, bone marrow, and hair follicles are most susceptible
• Also causes vascular damage and increased capillary permeability

Clinical Signs

Treatment

• No antidote exists - treatment is supportive
• Decontamination: Emesis if very recent, activated charcoal (colchicine undergoes enterohepatic recirculation so repeated doses may help)
• Aggressive IV fluids: Combat shock and dehydration
• GI protectants and antiemetics
• Blood products: For severe bone marrow suppression/coagulopathy
• Respiratory support: Oxygen supplementation as needed

Section 4: Oleander - Cardiac Glycoside Toxicity

Overview

Nerium oleander is an ornamental shrub containing cardiac glycosides (oleandrin, digitoxigenin) similar to digoxin. All parts of the plant are toxic, including the water in which cuttings have been placed. Toxicity can also occur from smoke inhalation if the plant is burned.

Mechanism of Toxicity

• Cardiac glycosides inhibit Na+/K+-ATPase pump
• Increased intracellular sodium leads to increased intracellular calcium
• Increased cardiac contractility initially, but automaticity and conduction abnormalities develop
• Hyperkalemia common due to impaired cellular potassium uptake

Clinical Signs

• GI signs: Vomiting, diarrhea, abdominal pain, anorexia, hypersalivation
• Cardiac signs: Bradycardia (most common), various arrhythmias (AV block, ventricular arrhythmias), hypotension
• Neurologic: Weakness, tremors, seizures
• Other: Oral ulceration, death

Treatment

• Decontamination: Emesis, repeated activated charcoal (undergoes enterohepatic recirculation)
• IV fluids: Avoid calcium-containing fluids (LRS) as calcium worsens cardiac glycoside toxicity
• Cardiac monitoring: Continuous ECG
• Antiarrhythmics: Atropine for bradycardia; lidocaine for ventricular arrhythmias
• Digoxin-specific Fab fragments (Digibind): Antidote that binds and inactivates cardiac glycosides; expensive but effective

Quick Reference: Plant Toxicoses Comparison