Chapter 34: Acute Kidney Injury and Chronic Kidney Disease

The sources thoroughly cover renal failure, distinguishing between Acute Kidney Injury (AKI) and Chronic Kidney Disease (CKD), and explaining the progressive nature and systemic consequences of kidney dysfunction. AKI is defined as a rapid decline in kidney function, often abrupt in onset and potentially reversible if underlying factors are corrected. AKI is classified into prerenal (caused by decreased blood flow), intrarenal (damage to structures within the kidney, often manifesting as acute tubular injury or necrosis due to ischemia or nephrotoxic agents), and postrenal (obstruction of urine outflow, frequently due to prostatic hyperplasia). The progression of AKI is commonly divided into four stages: onset, oliguric, diuretic, and recovery. CKD, in contrast, results from irreparable, permanent loss of functional nephrons, and is diagnosed by persistent kidney damage or a Glomerular Filtration Rate (GFR) below 60 mL/min/1.73 m2 for three months or more. The main causes of CKD in the United States are hypertension and diabetes. As functional capacity diminishes, the accumulation of nitrogenous wastes (azotemia) leads to uremia, affecting virtually every body system. CKD manifestations include complex fluid, electrolyte, and acid-base disorders, skeletal complications such as renal osteodystrophy and secondary hyperparathyroidism, chronic anemia resulting from impaired erythropoietin production, severe cardiovascular issues like hypertension and left ventricular hypertrophy, neuromuscular problems like uremic encephalopathy and peripheral neuropathy, and altered immune function. Treatment involves measures to retard progression, notably strict control of blood pressure and blood glucose, individualized dietary management (protein, fluid, potassium, and phosphorus restriction), and eventually, renal replacement therapy through hemodialysis, peritoneal dialysis, or transplantation. The chapter also addresses specific management considerations and unique etiologies for CKD in children and older adults.