Chapter 22_1 flashcards
(24 cards)
Major Functions of the Kidney
Excretion of waste; BP control (RAAS); RBC production (Erythropoietin); Vitamin D synthesis; Drug metabolism/breakdown; Acid-base balance; Electrolyte and water management.
Glomerular Filtration Rate (GFR): Definition & Normal Value
The rate at which the kidneys filter blood per unit of time. Normal GFR is 90 to 120 mL/min.
How Aging Affects GFR
Peak kidney function is at age 30. GFR decreases by 1 mL/minute each year after, which can lead to accumulation of drug metabolites and toxins in older adults.
The Nephron: Basic Function
The basic functional unit of the kidney that filters blood, reabsorbs necessary fluid and electrolytes, and secretes waste products to form urine.
Key Actions of Nephron Sections
Glomerulus: Filtration of blood. Proximal Tubule: Reabsorption of most water and electrolytes. Loop of Henle: Concentrates filtrate. Distal Tubule: Aldosterone reabsorbs Na+ and water. Collecting Duct: ADH reabsorbs water.
Kidney’s Role in Acid-Base Balance
The kidneys maintain blood pH by regulating the excretion and reabsorption of hydrogen ions (H+, acid) and bicarbonate ions (HCO3–, base).
Kidney’s Role in Blood Pressure Control (RAAS)
The Renin-Angiotensin-Aldosterone System (RAAS) is activated by low renal perfusion. This system leads to sodium/water reabsorption and arterial vasoconstriction, which increases blood volume and blood pressure.
Kidney’s Role in RBC Production
In response to low oxygen (hypoxia), the kidneys secrete erythropoietin (EPO), which stimulates the bone marrow to produce red blood cells.
Kidney’s Role in Vitamin D Synthesis
The kidneys synthesize active Vitamin D, which is essential for the GI tract to absorb calcium.
Prerenal Dysfunction: Cause
Caused by decreased blood flow and perfusion TO the kidney. Examples: Severe dehydration, hemorrhage, or shock.
Intrarenal Dysfunction: Cause
Caused by direct damage or injury TO the kidney itself. Examples: Nephrotoxic medications, kidney infections (glomerulonephritis), systemic diseases (diabetes, HTN), or trauma to the kidney.
Postrenal Dysfunction: Cause
Caused by obstruction of urine outflow FROM the kidney. Examples: Kidney stones, enlarged prostate, or tumors blocking the ureters.
Hydronephrosis: Definition
A fluid-filled, swollen kidney that occurs when urine backs up due to an obstruction.
Acute Tubular Necrosis (ATN): Definition
The most common cause of acute kidney injury (AKI), where ischemia and hypoxia damage the renal tubules, causing them to slough off and block urine flow.
Assessment: CVA Tenderness
Costovertebral angle (CVA) tenderness is a classic sign of a kidney disorder, particularly infection like pyelonephritis. It is elicited by firmly tapping on the back over the kidney area.
Assessment: Hematuria vs. Proteinuria
Hematuria: Blood in the urine, often a sign of kidney stones or infection. Proteinuria (or microalbuminuria): Protein in the urine, a key sign of glomerular injury.
Diagnosis: Urinalysis Basics
Examines urine character, biochemistry, and microscopy. Positive results for glucose, ketones, protein, blood, nitrites, or leukocyte esterase can indicate disease.
Diagnosis: Blood Urea Nitrogen (BUN)
Measures nitrogenous waste in the blood. Normal is 5-20 mg/dL. Azotemia is an elevated BUN. Can be elevated due to dehydration or high protein intake, not just kidney dysfunction.
Diagnosis: Serum Creatinine
A muscle breakdown product filtered by the glomerulus. It is a reliable indicator of kidney function. Normal is 0.5-1.5 mg/dL.
Diagnosis: Creatinine Clearance (CrCl)
Measures the GFR by comparing creatinine levels in blood and a 24-hour urine sample. Decreased CrCl indicates decreased GFR and impaired renal function.
Treatment: Hemodialysis
A treatment where the patient’s blood is drawn out of the body, passed through a dialyzer to filter waste, and then returned to the body. Usually done 3 times a week.
Treatment: Peritoneal Dialysis (PD)
A treatment where a dialysis solution is instilled into the patient’s peritoneal cavity. Waste products from the blood diffuse into this solution, which is then drained and discarded. Less common than hemodialysis.
Treatment: Continuous Renal Replacement Therapy (CRRT)
A slower form of dialysis used for critically ill, hemodynamically unstable patients. It filters blood continuously over 24 hours.
Key Term: Oliguria
Low urine output, defined as less than 400 mL per day or less than 20-30 mL per hour.
