Renal Physiology and Disorders Quiz. Hammer Ch 16

Renal Disease

• Kidney disease significantly impacts global health, both in developing and developed countries.
• The CDC estimates over 20 million Americans aged 20+ have chronic kidney disease.
• Many suffer from acute kidney injury and other kidney diseases annually.
• Early detection and effective management are crucial in preventing kidney failure and other complications.
• Kidneys are vital for blood filtration and regulation of fluid, acid-base, and electrolyte balance.
• Kidney disease can be a manifestation of other diseases, such as diabetes mellitus, hypertension and autoimmune disorders, such as systemic lupus erythematosus.

Kidney Structure and Function

• Kidneys are vital for maintaining homeostasis under diverse environmental conditions, like freshwater fish, humans, and kangaroo rats.
• Each kidney has millions of nephrons, which are the basic functional units involved in blood filtration and recovery of water and salts from the filtrate.
• Blood flows from the cortex to the medulla.
• Filtration occurs in the glomerulus.
• Nephrons include a renal tubule (proximal convoluted tubule, loop of Henle, distal convoluted tubule and collecting ducts), where substances such as water, salts, and waste are adjusted.

Renal Regulation

• Kidney function is regulated by various systems and processes.
• Water and electrolytes are actively reabsorbed in the proximal tubule, with water passively resorbing with Na+.
• The counter-current multiplier mechanism (in the loop of Henle) concentrates urine.
• The distal tubule and collecting duct (under hormonal control, particularly antidiuretic hormone (ADH) and aldosterone) regulate composition before excretion into the ureter as urine.
• The kidney plays a critical role in blood pressure regulation, sensing blood Na+ and indirectly assessing perfusion pressure of the blood.
• The renin-angiotensin-aldosterone system is crucial in regulating blood volume and pressure

Regulation of Acid-Base Balance

• Kidneys and pulmonary system maintain acid-base balance.
• Bicarbonate plays a critical role in buffer system (H+ + HCO3− → H₂CO₃ → H₂O + CO₂).
• Rapid (seconds to minutes) pulmonary response to imbalance.
• Kidneys' slower response (hours to days) crucial for nonvolatile acid removal.
• Kidney excretion of fixed acids (primarily through ammonium) crucial for maintaining balance
• The kidneys also regulate reabsorption and regeneration of bicarbonate in the proximal tubule.

Metabolic Acidosis

• Metabolic acidosis is the excessive production of endogeneous acids or loss of bicarbonate, or ingestion of exogenous acids.
• Kidneys compensate for acid-base imbalance.
• Factors include tissue ischemia, diabetes, and ingestion of exogenous acids.

Renal Regulation of Ca2+ Metabolism

• Kidneys regulate Ca2+ and phosphate homeostasis, primarily by 1α-hydroxylation of vitamin D3 (production of calcitriol), which increases Ca2+ absorption from the gut, and regulation of phosphate excretion as well as the effect of PTH on Ca2+ balance in urine.

Renal Regulation of Erythropoiesis

• Kidney is the main site of erythropoietin production.
• Erythropoietin stimulates bone marrow production and maturation of red blood cells.

Acute Kidney Injury (AKI)

• AKI is a sudden reduction in kidney function.
• Causes include hypoperfusion, tubular necrosis, obstruction.
• Symptoms include decreased urine output and the accumulation of nitrogenous wastes (e.g., BUN and creatinine).
• AKI impacts overall function across several systems, and this condition warrants critical evaluation.

Glomerulonephritis

• GN involves glomerular damage and encompasses several categories including poststreptococcal glomerulonephritis, other inflammatory and immune-complex diseases, and anti-neutrophil cytoplasmic antibody (ANCA)-associated diseases.
• Symptoms often include hematuria, proteinuria, and progressive renal failure.

Nephrotic Syndrome

• Nephrotic syndrome involves significant proteinuria, hypoalbuminemia, increased lipids, and edema.
• Minimal-change disease, focal and segmental glomerulosclerosis, membranous nephropathy, and membranoproliferative glomerulonephritis are some types.
• Injury to podocytes (the epithelial cells) is a key characteristic.

Renal Stones

• Renal stones are formed when urine components become supersaturated, resulting in crystallization and precipitation.
• Common causes include idiopathic hypercalciuria, hyperuricosuria, hyperparathyroidism, recurrent urinary tract infections, and cystinuria.
• Symptoms often encompass flank pain, often radiating and hematuria.