Summary
Summary Renal Failure
- Course
- N164 (N164)
- Institution
- Samuel Merritt University
Renal Failure & Kidney Issues: Complete guide to understanding and managing acute and chronic renal failure, dialysis, and related therapies.
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N164: Managing Care of Adults IIIRenal Failure Ch. 51 W3
" Blood flow to the kidneys, around 1200 mL/min, accounts for 20% to 25% of the cardiac output
• Kidneys
o The kidney is responsible for urine formation, the outcome of a complex, multistep process of filtration, reabsorption, secretion, and
excretion of water, electrolytes, and metabolic waste products.
o Kidney is efficient in getting rid of endogenous and exogenous waste products
• Endogenous = Creatinine, bilirubin, urea, uric acid
• Exogenous = Medications (e.g., Motrin)
o Kidney maintains homeostasis by regulating fluid, electrolyte,
and acid-base balance
• Renal Parenchyma
o Parenchyma → Actual tissue of the kidney
o Cortex → Outer layer of the parenchyma (kidney)–lies
peripherally under the capsule
o Medulla → Inner layer
• Consists of a number of pyramids (around 10-14)–
separated from each other by an inward extension of the
renal cortex called the renal columns.
• Papillae → The apices (tops) of these pyramids, through
which urine passes to enter the calyces.
o The minor calyces widen and merge to form major calyces, which form a funnel-shaped sac called the renal pelvis.
o The minor and major calyces transport urine to the renal pelvis, from there it drains through the ureter to the bladder.
o The renal pelvis can store a small volume of urine (3 to 5 mL).
• Nephron
o The functional unit of the kidney
o Approx. 1 million nephrons per kidney
o Composed of:
• Renal corpuscle (glomerulus)
• Bowmans capsule
• Tubular system
o After age 40, amount of nephrons decrease 10% every 10 years
• Glomerulus
o Urine formation begins at the glomerulus, where blood is filtered
o The glomerulus is a semipermeable membrane that allows filtration
o Amount of blood filtered each minute → Glomerular Filtration Rate (GFR) ≈ 125 mL/min
o Afferent Arteriole → brings blood to the glomerulus
o Efferent Arteriole → brings the blood out of the glomerulus
o Renal arteries change based on our BP or the chemicals that we take (constrict or dilate)
• IV contrast → Induces renal artery vasoconstriction
, o The hydrostatic pressure of the blood within the glomerular capillaries causes a portion of blood to be filtered across the semipermeable
membrane into Bowman capsule. There, the filtered portion of the blood (glomerular filtrate) begins to pass down to the tubule. Filtration is
more rapid in the glomerulus than in ordinary tissue capillaries because the glomerular membrane is porous. The glomerular filtrate is similar
in composition to blood except that it lacks blood cells, platelets, and large plasma proteins. Under normal conditions, capillary pores are too
small to allow the loss of these large blood components. However, in many kidney diseases, capillary permeability increases, which allows
plasma proteins and blood cells to pass into the urine.
• Bowmans Capsule
o Cup-like sac, surrounding the glomerulus,
o Where filtered blood begins to pass down to the tubule
• Tubules and Collecting Ducts
o Primary functions
• Reabsorption of some fluid and electrolytes
• Secretion/Excretion of nonessential products (e.g., waste products, H+ ions)
Functions of Nephron Segments
• Medications
Segment Function
o Loop of Henle
Glomerulus Selective filtration
• Furosemide [Lasix]
Proximal tubule Reabsorption of 80% of electrolytes and water, glucose,
° Loop diuretic → Blocks the reabsorption of
amino acids, HCO3–
sodium and potassium
Secretion of H+ and creatinine
• Bumetanide [Bumex]
Loop of Henle Concentration of filtrate
° Loop diuretic → Blocks the reabsorption of
Reabsorption of Na+ and Cl– in ascending limb and water
sodium and potassium
in descending loop
° More potent than Lasix, 40x more powerful
+ Distal tubule Reabsorption of water (regulated by ADH) and HCO3–
° Check Potassium (K ) and BP
Regulation of Ca2+ and PO42 — by parathyroid hormone
o Distal Convoluted Tubule
Regulation of Na+ and K+ by aldosterone
• Hydrochlorothiazide [HCTZ]
Secretion of K+, H+, ammonia
° Thiazide diuretic → Blocks reabsorption of
Collecting duct Reabsorption of water (requires ADH)
sodium-chloride (Na+ + Cl-)
° Check BP before/after
• Renin
o Important in BP regulation
o Hormone made and secreted by the kidney’s juxtaglomerular cells
o Renin is released into the bloodstream in response to decreased renal perfusion, decreased arterial BP, decreased ECF, decreased serum Na+
concentration, and increased urinary Na+ concentration.
o Renin activates the RAAS system
• RAAS System
o Renin converts angiotensinogen (from the liver) to angiotensin I
o Angiotensin I is then converted to angiotensin II by angiotensin-converting enzyme (ACE)–Released by the lungs
• ACE is found on the inner surface of all blood vessels, with especially high levels in the vessels of the lungs
o Angiotensin II stimulates the release of aldosterone from the adrenal cortex
• Aldosterone → Retains Na+ and H2O, excretes K+ (↑BP)
• This causes Na+ and water retention, leading to increased ECF volume
• Angiotensin II → Potent vasoconstrictor, causes increased peripheral vasoconstriction
o An elevated BP inhibits renin release.
o Excessive renin production caused by impaired renal perfusion may be a contributing factor in causing hypertension.
• Erythropoietin (EPO)
o Hormone made in the kidneys
o Stimulates RBC production in the bone marrow
• Secreted in response to hypoxia and decreased renal blood flow
o A deficiency of erythropoietin occurs in kidney failure, leading to anemia.
• Vitamin D
o Hormone that we obtain in the diet or make by the action of ultraviolet radiation on cholesterol in the skin.
• These forms of vitamin D are inactive
o Go through 2 more steps to become metabolically active → 1st step occurs in the liver; 2nd step occurs in the kidneys
• Kidneys covert Vitamin D into the active form of Vitamin D
• Essential for the absorption of calcium from the gastrointestinal (GI) tract
• The patient with kidney failure (also called renal failure) will have a deficiency of the active metabolite of vitamin D and problems with
calcium and phosphate balance.
• Insulin
o Kidney metabolizes insulin to maintain normal glucose levels and insulin levels
• Patients with kidney disease tend to have hyperinsulinemia → may lead to blood sugar problems
• Bicarbonate (HCO3-)
o Kidneys releases bicarb in response to acidosis
• Bicarb acts as a buffer in acidotic states
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