Chapter 55: Adult Renal and Urinary Problems

The kidneys maintain systemic homeostasis through glomerular filtration, tubular reabsorption, and secretion, with the nephron serving as the functional filtration unit. Hormonal regulation via antidiuretic hormone and the renin-angiotensin-aldosterone system controls fluid and electrolyte balance while managing blood pressure and red blood cell production. Clinical evaluation of renal function relies on serum creatinine levels, blood urea nitrogen measurements, glomerular filtration rate calculations, urinalysis findings, and renal biopsy procedures. Acute kidney injury represents sudden, potentially reversible loss of filtration function stemming from prerenal hypoperfusion, intrarenal tubular damage, or postrenal obstruction, progressing through distinct phases from onset through recovery. Chronic kidney disease involves gradual irreversible decline in glomerular filtration rate below 60 milliliters per minute persisting for three months or longer, affecting multiple organ systems and causing complications including hyperkalemia, anemia from erythropoietin deficiency, and metabolic acidosis. When renal function fails, hemodialysis utilizes semipermeable membranes and osmotic principles to remove waste and excess fluid, while peritoneal dialysis employs the peritoneal membrane as the filtration barrier. Kidney transplantation offers an alternative to ongoing dialysis with monitoring for hyperacute, acute, and chronic rejection patterns. The chapter also covers urinary tract infections including cystitis and pyelonephritis, obstructive conditions such as nephrolithiasis and benign prostatic hyperplasia causing urinary obstruction and symptoms, and structural disorders including polycystic kidney disease and hydronephrosis resulting from impaired urine flow.