The Urinary System: Essential Functions and Consequences of Failure

The urinary system (kidneys, ureters, bladder, urethra) is vital for survival. Without it, homeostasis collapses.

Core Kidney Functions

• Filtration: 180 L/day plasma filtered → removes urea, creatinine, toxins, drugs.
• Fluid/electrolyte balance: Regulates Na⁺, K⁺, Cl⁻, HCO₃⁻, Ca²⁺, PO₄³⁻, Mg²⁺.
• Acid-base homeostasis: Excretes H⁺ (as NH₄⁺, titratable acid), reabsorbs/generates HCO₃⁻.
• Blood pressure/volume: RAAS, ADH, natriuretic peptides.
• Erythropoietin: Stimulates RBC production.
• Vitamin D activation: 1α-hydroxylase → calcitriol.
• Gluconeogenesis: During prolonged fasting.

Consequences of Total Renal Failure

• Uremia: Nausea, encephalopathy, pericarditis, neuropathy, bleeding diathesis.
• Hyperkalemia: Cardiac arrest.
• Metabolic acidosis: Hyperventilation, catabolism, hemodynamic instability.
• Volume overload: Pulmonary edema, hypertension, heart failure.
• Anemia: EPO deficiency → fatigue, cardiac strain.
• Renal osteodystrophy: Secondary hyperparathyroidism, fractures.

Renal Replacement Therapy

• Hemodialysis, peritoneal dialysis, kidney transplant.
• Without RRT, death within days–weeks.

The kidneys are master regulators—loss is incompatible with life without artificial support.