Azotaemia

Description

Azotaemia refers to an increase in the blood concentrations of urea and creatinine. Azotaemia occurs almost exclusively with renal failure that results in an inability to excrete these two metabolic products.

Clinical Significance

Azotaemia may cause the clinical syndrome of uraemia, affecting multiple organ systems. The causes of azotaemia are usually divided into pre-renal, renal and post-renal:

• Pre-renal azotaemia occurs when the kidney receives insufficient oxygen to maintain its metabolism:
  • Dehydration/hypovolaemia, reducing renal blood flow.
  • Heart failure results in a reduced cardiac output, reducing renal blood flow.
  • Anaemia reduces the amount of oxygen delivered to the kidneys.
  • Portal hypertension may result in splanchnic pooling of blood and reduced renal blood flow.
• Renal azotaemia results from direct insults to the kidney:
  • Exogenous toxins including heavy metals, aminoglycosides, tetracyclines, polymixin B, cisplatin, lilies in cats and grapes in dogs.
  • Endogenous toxins including haemoglobin, myoglobin and calcium.
  • Infection as in pyelonephritis, interstitial nephritis (as caused by Leptospira spp. or granulomatous nephritis (as caused by the dry form of Feline Infectious Peritonitis).
  • Glomerulonephritis and amyloidosis.
  • Neoplasia, including adenocarcinoma in dogs and lymphoma in cats.
• Post-renal azotaemia results from obstructions to the urinary tract:
  • Urolithiasis
  • Rupture of the urinary tract, often due to trauma and causing uroabdomen.
  • Neoplasia, including transitional cell carcinoma of the bladder and prostatic neoplasia.]