🩺 Understanding Acute Kidney Injury in Dogs and Cats: A Silent Threat

By Dr. Roque Antônio de Almeida Júnior, DVM – CRMV-SP 23098
Mogi das Cruzes, Brazil | www.doutordosanimais.com.br

Introduction

Acute Kidney Injury (AKI), also known as acute renal failure, is a sudden decline in kidney function that leads to the accumulation of toxins, metabolic waste, and disturbances in fluid and electrolyte balance.
It is a medical emergency in both dogs and cats, and early recognition can make the difference between complete recovery and irreversible renal damage.

While the clinical presentation may seem nonspecific, understanding the underlying causes and pathophysiological mechanisms is essential for accurate diagnosis and effective treatment.

Pathophysiology of Acute Kidney Injury

The kidneys are vital for maintaining internal balance — filtering blood, excreting waste, regulating electrolytes, and producing hormones such as erythropoietin.
When renal blood flow or tissue integrity is compromised, the nephron (the kidney’s functional unit) begins to fail, leading to decreased glomerular filtration rate (GFR) and tubular dysfunction.

The mechanisms of AKI are often categorized into three main types:

Ischemic AKI – Caused by reduced renal perfusion, often secondary to hypovolemia, dehydration, shock, or anesthesia-related hypotension.
Toxic AKI – Resulting from exposure to nephrotoxic agents such as ethylene glycol, aminoglycosides, NSAIDs, or certain plants.
Infectious AKI – Caused by pathogens like Leptospira spp., which directly damage renal tissue and impair filtration.

In many clinical cases, these mechanisms may overlap, making diagnosis and management more challenging.

Clinical Signs and Diagnosis

The clinical signs of AKI in dogs and cats are often subtle at first.
Common manifestations include:

Lethargy and weakness
Vomiting and anorexia
Dehydration
Oliguria (reduced urine output) or anuria (no urine output)
Halitosis and oral ulcers (due to uremia)

Laboratory findings typically reveal azotemia (elevated BUN and creatinine), electrolyte imbalances (especially hyperkalemia), and urinalysis abnormalities such as proteinuria, casts, or altered specific gravity.

Imaging tools like abdominal ultrasound can help assess renal size, echotexture, and perfusion, aiding in the differentiation between acute and chronic renal processes.

Treatment and Prognosis

Management of AKI aims to:

Restore and maintain renal perfusion
Correct fluid and electrolyte imbalances
Eliminate underlying causes
Support the patient through detoxification and metabolic stabilization

Intravenous fluid therapy remains the cornerstone of treatment, carefully adjusted based on hydration status and urine output.
In more severe cases, diuretics (e.g., furosemide) or dialysis may be necessary to manage persistent anuria or toxin accumulation.

The prognosis depends on the underlying cause, duration of renal insult, and how quickly treatment is initiated.
While some animals may fully recover renal function, others may progress to chronic kidney disease (CKD) despite stabilization.

Prevention and Clinical Awareness

Prevention of AKI relies on awareness and early detection.
Tutores should avoid self-medicating pets with human drugs and ensure adequate hydration, especially in elderly animals or those with preexisting diseases.

For veterinarians, routine monitoring of renal parameters in hospitalized or high-risk patients is essential.
In cases involving nephrotoxic drugs, concurrent fluid therapy and renal monitoring should be mandatory.

Final Thoughts

Acute Kidney Injury remains one of the most critical challenges in small animal internal medicine.
Recognizing early clinical signs and understanding the interplay between perfusion, toxins, and infection are fundamental to preventing irreversible renal damage.

In veterinary medicine, time truly means nephron — every hour counts.
Prompt diagnosis and intervention can transform a potentially fatal event into a story of recovery and resilience.

👨‍⚕️ Authored by:
Dr. Roque Antônio de Almeida Júnior
Veterinarian | CRMV-SP 23098
📍 Mogi das Cruzes – São Paulo, Brazil
🌐 www.doutordosanimais.com.br
📸 @roque_junior_veterinario