Pathogenesis of Acute Renal Failure

A.Types: Extrarenal Conditions
a.Prerenal Failure
Decreased renal perfusion
Examples: Dehydration, CHF, Liver failure
b.Postrenal Failure
Renal outflow obstruction
Examples: BPH, Genitourinary tumors
B.Types: Intrarenal Conditions
c.Vascular Injury
Afferent arteriolar vasoconstriction
Results in decreased driving force
Decreased Glomerular filtration
Types
Microvascular (Small vessel thrombosis)
Macrovascular (e.g. Renal Artery Stenosis)
d.Glomerulonephritis
Associated with Hematuria and Proteinuria
e.Acute Interstitial Nephritis
Due to allergic or autoimmune diseases
f.Tubular Injury and Acute Tubular Necrosis
Mechanism
Tubules injured in most but not all acute failure
Obstruction
Abnormal material inspissates and plugs flow
Back-leak
Tubular cells loose integrity
Back-leaks ultrafiltrate
Results in poor waste clearance
Course (3 phases)
Initiation phase (minutes to hours)
Starts with well functioning kidney
Kidney bombarded by potential toxins
Maintenance phase
Established loss of Renal Function
Kidney unresponsive to simple interventions
Recovery phase (weeks to months)
Complete recovery in Acute Tubular Necrosis
Specific Examples
a.Intravenous Contrast Related Acute Renal Failure
b.Renal Ischemia
Tubular obstruction and back-leak
c.Aminoglycoside Antibiotics
Decreased Glomerular Filtration Rate
Tubular cell injury
d.Rhabdomyolysis
Decreased afferent blood flow
Renal tubular obstruction