Clinical meaning
Hemodialysis is a life-sustaining renal replacement therapy that performs the essential functions of the kidneys when they can no longer adequately filter blood, maintain fluid and electrolyte balance, or excrete metabolic waste products. It is indicated when the glomerular filtration rate (GFR) falls below 10-15 mL/min (end-stage renal disease, stage 5 CKD), or earlier if symptomatic uremia develops. The kidneys normally filter approximately 180 litres of plasma daily, producing 1-2 litres of urine. They regulate fluid volume, electrolyte concentrations (sodium, potassium, calcium, phosphorus), acid-base balance, and excrete metabolic waste products (urea, creatinine, uric acid). The kidneys also produce erythropoietin (red blood cell production), activate vitamin D (calcium metabolism), and regulate blood pressure through the renin-angiotensin-aldosterone system. When these functions fail, toxic metabolites accumulate, causing the uremic syndrome. Uremic syndrome manifests with multi-system dysfunction: neurological (encephalopathy, peripheral neuropathy, asterixis), cardiovascular (pericarditis, heart failure from fluid overload, accelerated atherosclerosis), haematological (anemia from erythropoietin deficiency, platelet dysfunction with bleeding tendency), gastrointestinal (nausea, vomiting, anorexia, uremic fetor - ammonia breath), dermatological (pruritus, uremic frost - urea crystal deposits on skin), and metabolic (hyperkalemia, metabolic...