What Is a Kidney?

The kidneys are a pair of vital organs located in the abdomen of dogs. They perform several essential functions:

  1. Filtration of Blood: Remove metabolic waste products like urea and creatinine.
  2. Water and Electrolyte Balance: Maintain proper levels of sodium, potassium, and water.
  3. Acid–Base Balance: Regulate blood pH.
  4. Hormone Production: Produce hormones such as erythropoietin (stimulates red blood cell production) and renin (controls blood pressure).
  5. Nutrient Conservation: Retain essential nutrients like amino acids and prevent excessive protein loss.

 What Is Kidney Disease in Dogs?

Kidney disease is a condition in which the kidneys lose their ability to perform vital functions, including:

  • Filtering metabolic waste
  • Regulating water and electrolytes
  • Maintaining acid–base balance
  • Conserving nutrients and body proteins

Kidney disease can be acute or chronic.

Definition of Acute Kidney Injury (AKI)

Acute Kidney Injury (AKI), also called acute kidney disease, is a sudden loss of kidney function that develops over hours to days.

  • Often reversible if detected early
  • Caused by toxins, infections, dehydration, or obstruction
  • Leads to rapid accumulation of nitrogenous wastes
  • May cause electrolyte and acid–base imbalance

Clinical signs: sudden anorexia, vomiting, lethargy, decreased urine output (oliguria/anuria), dehydration

1.2 Definition of Chronic Kidney Disease (CKD)

Chronic Kidney Disease (CKD) is a progressive, irreversible loss of kidney function that persists for more than 3 months.

  • Gradual nephron loss over months to years
  • Accumulation of urea, creatinine, and other metabolic wastes
  • Impaired water, electrolyte, and acid–base balance
  • Progressive deterioration over time

Clinical relevance: Most common in older dogs; requires lifelong management.

  1. Occurrence of Kidney Disease

Causes of AKI:

  • Infections (leptospirosis, pyelonephritis)
  • Toxins (plants, chemicals, drugs)
  • Severe dehydration or shock
  • Urinary tract obstruction

Causes of CKD:

  • Progressive nephron loss due to age
  • Chronic infections
  • Repeated dehydration
  • Long-term exposure to toxins or drugs
  • High dietary phosphorus
  • Poor-quality protein
  • Genetic and breed predisposition
  1. Epidemiology of Kidney Disease in Dogs

3.1 Age-wise Prevalence

  • AKI can occur at any age depending on cause (toxins, infections)
  • CKD is primarily seen in adult and geriatric dogs, especially >6–8 years
  • Peak prevalence for CKD: 8–10+ years

3.2 Sex-wise Prevalence

  • AKI: no clear sex predilection; depends on exposure
  • CKD: slight male predominance in Indian studies (~57% males vs. ~43% females)

3.3 Breed-wise Predisposition

Indian Context

  • CKD: Labrador Retriever, German Shepherd, Pomeranian, Doberman, Rottweiler, Great Dane, Dalmatian, Bulldog
  • AKI: any breed can be affected; often small breeds more prone to toxin ingestion

Global Observations

  • Small breeds (Pomeranian, Yorkshire Terrier) in older age show higher CKD prevalence
  • Large breeds may progress faster once disease develops

3.4 Prevalence

  • Worldwide
  • CKD: significant proportion of renal cases; prevalence rises with age
  • AKI: less common but acute cases are critical and need immediate intervention
  • India
  • CKD prevalence in clinical canine cases: ~5–9%
  • AKI prevalence: varies; often hospital-reported cases due to toxins or infections
  1. Compensatory Mechanism and Silent Progression (CKD)
  • Healthy nephrons compensate until ~70% are lost
  • Blood parameters appear normal initially
  • Clinical signs appear late (polyuria, polydipsia, appetite loss)

AKI, in contrast, shows sudden and obvious signs, often requiring emergency care.

Pathophysiology

5.1 AKI

  • Sudden reduction in glomerular filtration rate (GFR)
  • Rapid accumulation of urea, creatinine, and electrolytes
  • Possible electrolyte imbalances (hyperkalemia, hyponatremia)
  • Fluid overload or dehydration depending on urine output

5.2 CKD

  • Gradual GFR decline
  • Protein metabolism disturbance → muscle wasting
  • Phosphorus retention → secondary renal hyperparathyroidism
  • Impaired water balance → polyuria and compensatory polydipsia
  • Acid–base imbalance → metabolic acidosis → muscle catabolism
  • Increased sensitivity to toxins

5.3 Muscle Wasting (Protein–Energy Wasting)

  • CKD complication due to:
  • Reduced appetite
  • Protein catabolism
  • Metabolic acidosis
  • Inadequate essential amino acids
  • Signs: weight loss, reduced muscle mass, weakness
  • Note: Excessive protein restriction worsens muscle wasting
  1. Role of Nutrition

Nutrition is crucial for both AKI and CKD management:

  • AKI: focus on hydration, correcting electrolyte imbalance, and avoiding nephrotoxins
  • CKD: moderate, high-quality protein; ideal amino acids; restricted phosphorus; low sodium; avoid toxins

Goal: Reduce metabolic burden, preserve muscle, and slow progression.

Acute and Chronic Kidney Disease: Definition, Pathophysiology, Epidemiology, and Management

By Dr Vikash Raj , B.V.SC&A.H, MVSC (ANIMAL NUTRITION) (WBUAFS).

Vikashnutrition81@gmail.com