Chapter 25: Urinary System

Question 1

Urinary System:

Answer 1

o	Organs:
o	2 kidneys.
o	2 ureters.
o	1 urinary bladder.
o	1 urethra.
o	Nephrology = study 	of kidneys.
o	Urology = study of entire urinary system.

Question 2

Urine Flow:

Answer 2

o Kidneys make urine.
o Ureters transport urine to bladder.
o Urinary bladder stores urine (regulated by urinary sphincters).
o Urethra transports urine to external urethral orifice and out of body.

Question 3

Macroscopic Anatomy of Kidney:

Answer 3

o	4-5” long, 2-3” wide, 1” thick (bar of soap).
o	Found just above the waist between the peritoneum and posterior wall of abdomen (retroperitoneal).
o	Protected by 11th and 12th ribs with right kidney lower.
o	Renal (fibrous) capsule = transparent membrane maintains organ shape.
o	Perirenal fat capsule = Adipose capsule that protects and anchors.
o	Renal fascia = dense, irregular connective tissue that anchors kidneys to posterior body wall.

Question 4

Internal Anatomy of Kidney:

Answer 4

o RENAL CORTEX:
o Outer, superficial layer, smooth, light in color.
o 90 percent of blood entering kidney perfuses the cortex.
o 80 to 85 percent of kidney nephrons are located in the cortex =cortical nephrons.
o RENAL MEDULLA:
o Inner layer, darker color.
o Contains 6 to 10 Renal pyramids per kidney.
o Renal Papilla = tip of each renal pyramid.
o Renal Column = extensions of cortex between pyramids.
o Renal Lobe = renal pyramid + renal cortex above it + ½ of each adjacent renal column.
o Renal pyramids have a striped appearance because they contain (roughly parallel) renal tubules and ducts.
o Renal papillae contain papillary ducts.
o Minor and Major Calices drain urine from papillary ducts into the renal pelvis then to ureter.

Question 5

Blood Supply to Kidney:

Answer 5

o Kidneys receive 25% of resting cardiac output via renal arteries.
o CO (5.25 L/min)=SV (70 mL/beat) X HR (75 beats/min).
o Thus, kidneys receive more greater than 1 L of blood/minute.
o Renal circulation is unique:
o Afferent arteriole to glomerular capillaries to efferent arteriole.
o Afferent arteriole has larger diameter than Efferent arteriole.
o Each nephron has 2 different capillary beds:
o Glomerular capillaries where filtration of blood occurs.
o High pressure and specialized for filtration.
o Vasoconstriction and vasodilation of afferent and efferent arterioles produce large changes in renal filtration.
o Peritubular capillaries (or vasa recta) carry away reabsorbed substances from filtrate.
o Low pressure, thus adapted for reabsorption.

Question 6

Nerve Supply to Kidney:

Answer 6

o Renal nerves come off of the superior mesenteric ganglion, contain mostly sympathetic postganglionic neurons.
o Enter hilum of kidney and follow branches of renal artery to the afferent and efferent arterioles.
o Regulates blood flow in/out of nephron.

Question 7

Anatomy of Ureters:

Answer 7

o 10-12” long.
o 1 to 10 mm in diameter (think about renal stones!!).
o 3 tunics:
o Mucosa (transitional epithelium with goblet cells).
o Muscularis (inner longitudinal and outer circular layers smooth muscle—3rd layer distally.
o Adventitia.
o Extend from renal pelvis to bladder.
o Retroperitoneal.
o Enter posterior wall of bladder through ureteric orifices.
o Flow results from peristalsis, gravity and hydrostatic pressure.

Question 8

Anatomy of Urinary Bladder:

Answer 8

o Hollow, distensible muscular organ with capacity for 700-800 mL.
o Rugae of urinary bladder allow stretching.
o Trigone is smooth flat area bordered by 2 ureteric orifices and internal urethral orifice.
o Detrusor muscle and internal/external urethral sphincter.

Question 9

Location of Urinary Bladder:

Answer 9

o Posterior to pubic symphysis
o Females: urinary bladder is anterior to vagina and inferior to uterus.
o Females: pubic symphysis leads to bladder leads to vagina leads to rectum.
o Males: Pubic Symphysis to Bladder to Rectum.

Question 10

Histology of Urinary Bladder:

Answer 10

o 3 Tunics:
o Mucosa = transitional epithelium with rugae.
o Muscularis: detrusor muscle (3 layers).
o Adventitia (urinary bladder is retroperitoneal).

Question 11

Urination (Micturition):

Answer 11

o MICTURITION = urination = a reflex involving the sacral spinal cord, the parasympathetic and sympathetic nervous systems, and voluntary conscious control.
o Internal urethral sphincter: smooth muscle fibers at OPENING to urethra (involuntary control).
o External urethral sphincter: skeletal muscle (modification of urogenital diaphragm muscle), inferior to internal urethral sphincter, voluntary control.

Question 12

Urinary Incontinence:

Answer 12

o Urinary incontinence = inability to hold urine.
o Normal in 2 or 3 year olds because neurons to sphincter muscles are not developed.
o Stress Incontinence = anything that increases abdominal pressure (coughing, sneezing, laughing, exercising, pregnancy).
o Other causes of incontinence:
o Spinal cord injuries.
o Injury to nerves controlling micturition.
o Damage to external urethral sphincter.
o Irritation of bladder or urethra.
o Obstructed urinary outlet.
o Certain drugs.

Question 13

Macroscopic Anatomy of Urethra:

Answer 13

o Females: 1.5 inches long.
o External urethral orifice is between the clitoris and the vaginal opening.
o Males: 6 to 8 inches long.
o Internal urethral orifice to prostate to urogenital diaphragm to penis.
o Male urethra has dual role of discharging both semen AND urine, but not at the same time.

Question 14

Urethritis:

Answer 14

Inflammation/Infection of urethra (more common in females).

Question 15

Cystitis:

Answer 15

Inflammation/Infection of urinary bladder.

Question 16

Pyelitis:

Answer 16

Inflammation/Infection of renal pelvis and calyces.

Question 17

Pyelonephritis:

Answer 17

Inflammation/Infection of kidneys (very serious, may require IV antibiodics).

Question 18

Summary of Kidney:

Answer 18

o Kidneys filter the blood and return most of the water and solutes to the blood.
o Blood comes into a glomerulus (ball of capillaries), filtration pushes large amounts of plasma and MOST solutes into a capsular space, the rest of the kidney (nephron tubules) is concerned with RECLAIMING the solutes that our bodies want to KEEP, the wastes stay in the tubules and eventually become urine.

Question 19

Kidney Functions:

Answer 19

o	Excrete wastes.
o	Regulate composition of blood.
o	Lytes and osmolarity.
o	Regulate volume of blood.
o	Regulate blood pressure.
o	Renin and RAS system!
o	Secrete hormones.
o	Help regulate acid-base balance.
o	Detoxify free radicals and meds.
o	Gluconeogenesis during starvation.

Question 20

Examples of “Wastes”:

Answer 20

o	Nitrogenous wastes:
o	NH3, Urea, Creatinine, Uric acid.
o	Bilirubin and byproducts.
o	Foreign substances (meds, environmental toxins).
o	Excess vitamins.
o	Excess mineral salts (ions).
o	Excess water.

Question 21

The Nephron:

Answer 21

o Functional Unit of Kidney.
o Each kidney has more than one million nephrons!
o Each nephron:
o 1. Renal corpuscle.
o 2. Renal tubule.
o Function:
o Filtration of blood (renal corpuscle).
o Reabsorption of important solutes within the formed filtrate (renal tubule).
o Secretion of wastes/solutes INTO the filtrate (renal tubule).
o Renal corpuscle = site of plasma filtration.
o Glomerulus contains capillaries where filtration occurs.
o Glomerular (Bowman’s) capsule is double-walled epithelial cup that collects filtrate.
o Visceral Layer of Bowman’s capsule.
o Parietal Layer of Bowman’s capsule.
o Renal tubule:
o Proximal convoluted tubule.
o Loop of Henle dips down into renal medulla.
o Distal convoluted tubule.
o Collecting ducts.

Question 22

Blood Vessels Around the Nephron:

Answer 22

o Glomerular capillaries are formed between the afferent and efferent arterioles.
o Efferent arterioles give rise to the peritubular capillaries or vasa recta capillaries.
o Afferent arteriole
o Lined by endothelium.
o Wall includes smooth muscle fibers with alpha-1 adrenergic receptors
o Some modified smooth muscle fibers called juxtaglomerular cells (JG cells), secrete renin.
o Glomerular capillaries:
o Fenestrated capillaries, very porous.
o Basement membrane restricts passage only of large plasma proteins and formed elements.
o Efferent arteriole:
o Lined by endothelium.
o Wall includes smooth muscle fibers with alpha-1 adrenergic receptors.
o Smaller in diameter than afferent arteriole.

Question 23

Histology of Renal Corpuscle:

Answer 23

o Bowman’s capsule surrounds capsular space=double-walled cup with a parietal layer (outer wall), capsular space and visceral layer (inner).
o Podocytes cover capillaries to form visceral layer.
o Simple squamous cells form parietal layer of capsule.
o Glomerular capillaries arise from afferent arteriole and form a ball (fenestrated capillaries!) before emptying into efferent arteriole.

Question 24

Juxtaglomerular Apparatus:

Answer 24

o Structure where afferent arteriole “kisses” the DCT
o Juxtaglomerular (granular) cells are modified smooth muscle cells in arteriole (granular looking cells that secrete RENIN into blood).
o Macula densa found at first part of DCT.
o Mesangial cells.

Question 25

Filtration Membrane:

Answer 25

o Capillary endothelium.
o Basement membranes.
o Filtration slits of podocytes.
o Stops all cells and platelets.
o Stops large plasma proteins.
o Stops medium-sized proteins, but not small ones.
o Any molecule less than 3 nm can pass freely into capsular space (albumin about 7 nm).

Question 26

Glomerular Filtrate:

Answer 26

o Good stuff we want to reabsorb and wastes we want to excrete.
o Water, Electrolytes, Glucose, Fatty acids, Amino acids, Vitamins, Few small proteins/polypeptides.
o Nitrogenous wastes:
o Urea, Creatinine.

Question 27

Histology of the Renal Tubule:

Answer 27

o Single layer of epithelial cells forms walls of entire renal tubule.
o Distinctive features due to function of each region:
o Microvilli, cuboidal versus simple, hormone receptors, transporters.

Question 28

Histology of Proximal Convoluted Tubule:

Answer 28

o	Simple cuboidal epithelium with brush border of microvilli that increase surface area.
o	Longest and most coiled.
o	Over 65 percent of reabsorption occurs:
o	100 percent of most organic solutes.
o	80 percent of HCO3- (bicarbonate ion).
o	65 percent of H20, Na+.
o	55-60 percent of K+ and Cl-.
o	Secretion also occurs:
o	Urea, uric acid, creatinine, NH3.
o	H+, HCO3-, prostaglandins, etc.

Question 29

Reabsorption Routes:

Answer 29

o Paracellular reabsorption (between cells).
o Transcellular reabsorption: material moves through both the luminal (apical) and basolateral membranes of the tubule cell by many transport mechanisms.

Question 30

Transport Mechanisms:

Answer 30

o Apical and basolateral membranes of tubule cells have different types of transport proteins.
o Reabsorption of Na+ is important:
o Several transport systems exist to reabsorb Na+.
o Na+/K+ ATPase pumps sodium from tubule cell cytosol through the basolateral membrane only.
o Water absorbed only by osmosis.

Question 31

Reabsorption of Water by Osmosis:

Answer 31

o Obligatory water reabsorption: occurs when water is “obliged” to follow the solutes being reabsorbed.
o Facultative water reabsorption: occurs in the DCT and collecting duct under the control of antidiuretic hormone.

Question 32

Reabsorption of Bicarbonate, Sodium, and Hydrogen Ions:

Answer 32

o Na+ antiporters reabsorb Na+ and secrete H+.
o PCT cells produce the H+ and release bicarbonate ion to the peritubular capillaries.
o Important buffering system.
o For every H+ secreted into the tubular fluid, one filtered bicarbonate eventually returns to the blood.

Question 33

Glucosuria:

Answer 33

o Glucose transporters (SGLTs) can only move “so much” glucose =TRANSPORT MAXIMUM.
o SGLTs can not reabsorb glucose fast enough if blood glucose level is above 200 to 300 mg/dL (highly individual).
o If the TM is exceeded, some glucose remains in the urine (glucosuria). In a healthy person, glucose enters PCT at 125 mg/min).
o Common cause is diabetes mellitus.
o Rare genetic disorder produces defect in transporter that reduces its effectiveness.

Question 34

Histology of Loop of Henle:

Answer 34

o Primary functions:
o Reabsorb another 25 percent of filtrate.
o Create a salinity gradient to concentrate urine.
o Thin segments = simple squamous epithelium.
o Very low metabolic activity.
o Very permeable to water.
o Thick segments = simple cuboidal epithelium.
o Mostly impermeable to water.
o Active transport of salts (Na+, K+, Cl-, Ca++).

Question 35

Transporters in the Loop of Henle:

Answer 35

o Thick segment of ascending Loop of Henle has Na+ K+ Cl- transporters that reabsorb these ions.
o K+ leaks through K+ channels back into the tubular fluid leaving the interstitial fluid and blood with a negative charge.
o Thick segment is impermeable to water.

Question 36

Histology of Distal Convoluted Tubule:

Answer 36

o	Fluid arriving here still contains 25 percent of water and 10 percent of the salts of original filtrate.
o	Simple cuboidal epithelium.
o	Principal cells:
o	Aldosterone receptors.
o	Reabsorb sodium.
o	Secrete potassium.
o	ADH receptors:  H20 channels.
o	Receptors for hm involved in Ca++ metab.
o	Intercalated cells:
o	Secrete H+ (acid-base balance).
o	Reabsorb K+ and HCO3-.

Question 37

Reabsorption of DCT:

Answer 37

o Removal of Na+ and Cl- continues in the DCT by means of Na+ and Cl- transporters.
o Na+ and Cl- then reabsorbed into peritubular capillaries.
o DCT is major site where parathyroid hormone (PTH) and calcitriol stimulate reabsorption of Ca+.

Question 38

Secretion of Hydrogen and Absorption of Bicarbonate by Intercalated Cells:

Answer 38

o Proton pumps (H+ATPases) secrete H+ into tubular fluid:
o Can secrete against a concentration gradient so urine can be 1000 times more acidic than blood.
o Cl-/HCO3- antiporters move bicarbonate ions into the blood:
o Intercalated cells help regulate pH of body fluids.
o Urine is buffered by HPO4 2- and ammonia, both of which combine irreversibly with H+ and are excreted.

Question 39

Histology of Collecting Duct:

Answer 39

o Primary functions:
o Conserving body water, Fine-tuning of lytes , Simple cuboidal epithelium.
o Principal cells
o Aldosterone receptors: Reabsorb sodium, Secrete potassium.
o ADH receptors: H20 channels
o Intercalated cells: Secrete H+ (acid-base balance), Reabsorb K+ and HCO3-.

Question 40

Reabsorption and Secretion in the Collecting Duct:

Answer 40

o By end of DCT, 95 percent of solutes and water have been reabsorbed and returned to the bloodstream.
o Cells in the collecting duct make the final adjustments.
o Strong concentration of urine is possible through the countercurrent exchange system.

Question 41

Several Types of Diuretic Meds:

Answer 41

o Osmotic diuretics (e.g., mannitol, glucose, ketones in the urine).
o Diuretics that inhibit sodium reabsorption:
o Caffeine.
o Inhibit sodium symporters at the DCT.
o HCTZ.
o Loop diuretics act on ascending limb of Loop of Henle (interfere with medullary gradient—very powerful meds).
o Lasix (furosemide).
o Most diuretics have side effects.

Question 42

Urine:

Answer 42

o	Average adult produces 1 – 2 L/day.
o	Polyuria = more than 2 L/day.
o	Diabetes mellitus.
o	Diabetes insipidus.
o	Meds (e.g., diuretics).
o	Oliguria = urine output less than 500 mL/day or less than 30 mL/hour.
o	Anuria = urine output less than 50 mL/day.
o	Kidney failure.
o	Circulatory shock.
o	95 percent water, 5 percent solutes.
o	Urea, Na+, K+, PO4, SO4, creatinine, urate.
o	Variable amounts of Ca++, Mg++, HCO3-, toxins, drug metabolites, etc.
o	Osmolarity 50 – 1200 mOsm/L.
o	Specific gravity = 1.001 to 1.028.
o	pH is typically about 6.0 (acidic).
o	Clear—color depends on hydration.

Question 43

Abnormal Findings in Urine:

Answer 43

o	Glucose (glycosuria).
o	Blood (hematuria).
o	Hb (hemoglobinuria).
o	WBCs (pyuria).
o	Protein (proteinuria).
o	Albumin (albuminuria).
o	Excessive Ketones (ketonuria).
o	Excessive Bile pigments (bilirubinuria).

Question 44

Renal Function Tests:

Answer 44

o Urinalysis.
o Blood analysis:
o BUN = blood urea nitrogen (normal: 10 = 20 mg/dL).
o Serum creatinine (normal: 0.7 – 1.2 mg/dL).
o Functional tests:
o Renal clearance tests.
o Glomerular filtration rate (GFR).

Question 45

Filtration:

Answer 45

o 1/5 of the plasma coming into the glomerular capillaries (from the Afferent arteriole) is filtered through the filtration membrane.
o 4/5 of the plasma exits the glomerulus via the Efferent arteriole.
o Kidneys receive 20 to 25 percent of cardiac output, more than 1000 mL/minute.
o 1000 X 0.55 = 550 mL of plasma entering glomerulus each minute.
o 1/5 of this 550 mL is FILTERED through the filtration membrane, about 110 mL/min.

Question 46

Glomerular Filtration Rate (GFR):

Answer 46

o If kidneys are filtering 110 mL/minute, this means that in this 2 hour 40 min class, you have produced 17.6 LITERS of filtrate.
o In a 24-hour period, we typically produce 150 to 180 liters of filtrate, only 1 to 2 liters leaves body as urine.
o This Volume of Filtrate is Possible Because:
o 1. Glomerular capillaries are long, long, LONG with a huge surface area.
• When mesangial cells relax, surface area is maximized.
• When mesangial cells contract, there is a decrease in S.A. and in GFR.
o 2. Filtration membrane is thin and porous…glomerular capillaries are 50X leakier than other body capillaries.
o 3. Blood pressure in the glomerular capillaries is higher than in normal capillaries.
o Normal GFR = total amount of filtrate formed each minute by both kidneys.
o Adult female: 105 mL/minute (about 151 L/day).
o Adult male: 125 mL/minute (about 180 L/day).
o Variables that affect GFR:
o GFR is directly proportional to NFP
o Increase in NFP causes an INCREASE in GFR
o Decrease in NFP causes a DECREASE in GFR
o GFR is also dependent on:
o Surface Area.
o Filtration membrane health and permeability.
o GFR usually is a reflection of changes in glomerular blood pressure (HPg).

Question 47

Filtration:

A Passive Process

Answer 47

o Net filtration is based on pressure differences between:
o BP of glomerular capillaries.
o Osmotic pressure in glomerular capillaries.
o Hydrostatic pressure in the capsular space (HPcs).

Question 48

Net Filtration Pressure:

Answer 48

o Factors promoting filtration.
o Blood pressure in glomerulus (blood hydrostatic pressure) PUSHES OUT.
o Anything attracting or PULLING OUT fluid from plasma, like the presence of plasma proteins in the capsular space (capsular osmotic pressure).
o Factors opposing filtration.
o Factors opposing filtration (things that make plasma want to STAY in the glomerular capillaries rather than leave):
o Blood colloid osmotic pressure (osmotic pressure of glomerular capillaries).
o Hydrostatic pressure in the capsular space (pushes fluid back towards the glomerulus).
o NFP = HPg minus OPg minus HPcs.
o NFP = 55 mm Hg minus 30 mm minus 15 mm= 10 mm Hg.

Question 49

Significance of GFR:

Answer 49

o If GFR is too HIGH, filtrate flows too quickly through the renal tubule system.
o Things don’t have time to be reabsorbed…osmolarity of filtrate goes up.
o Good stuff gets lost in urine.
o If GFR is too LOW, not enough of the blood ends up getting filtered
o Waste products don’t end up in urine, stay in blood.
o Osmolarity of filtrate goes down.

Question 50

Regulation of GFR:

Answer 50

o What types of things can be adjusted in a healthy person?
o Adjust blood flow INTO and OUT OF glomerulus.
o Alter glomerular capillary surface area via mesangial cells.
o 3 levels of control to adjust the GFR:
o Renal autoregulation (local control)
o Neural regulation (extrinsic control via sympathetic nervous system).
o Hormonal regulation (extrinsic control via endocrine system).

Question 51

Renal Autoregulation:

Local

Answer 51

o Myogenic mechanism (fast)):
o BP is too high/GFR is too high, so smooth muscle in walls of afferent arteriole get too stretched leads to smooth muscle contraction!
o Tubuloglomerular feedback:
o Macula densa cells are chemoreceptors that detect changes in osmolarity of filtrate; they can release vasoactive chemicals.

Question 52

Neural Regulation of GFR:

Answer 52

o 1. Release of NE from sympathetic neurons interacts with alpha-one receptors on smooth muscle cells of blood vessels.
o At rest, sympathetic stimulation is low and renal autoregulation prevails.
o With moderate sympathetic stimulation, BOTH afferent and efferent arterioles constrict to about the same degree.
o With GREAT sympathetic stimulation, vasoconstriction of the afferent arteriole predominates.
o 2. Sympathetic neurons directly stimulate beta-one receptors of the JG cells, causing the release of RENIN.

Question 53

Factors Increasing Renin Release:

Answer 53

o 1. Direct stimulation of beta-1 receptors by sympathetic N.S.
o 2. Reduced stretch of the JG cells (from a decrease in BP or decrease in blood volume).
o 3. Macula densa cells sense decreased osmolarity in filtrate… paracrine secretion.

Question 54

Factors Decreasing Renin Release:

Answer 54

o 1. Reduced sympathetic N.S. activity.
o 2. Increased BP in afferent arteriole.
o 3. Increased secretion of natriuretic peptides (ANP and BNP) which directly inhibit renin release.

Question 55

Hormonal Control of GFR:

Answer 55

o	1. RAS system.
o	2. Angiotensin II target tissues:
o	Smooth muscle of blood vessels.
o	Adrenal cortex.
o	Hypothalamus.
o	Kidney tubules (PCT).
o	Mesangial cells (contraction).
o	Angiotensin II target tissues:
o	Smooth muscle of blood vessels.
o	Adrenal cortex.
o	Hypothalamus.
o	Kidney tubules (PCT).
o	Mesangial cells (contraction).
o	What are the specific effects? 
o	Increased vasoconstriction.
o	Increased release aldosterone.
o	Increased release ADH.
o	Increased conservation of sodium and water in kidneys.
o	Increased contraction of mesangial cells (decreased SA).

Question 56

Angiotensin II Overall Effects in RAS:

Answer 56

o Maintenance of GFR.
o Increased reabsorption of fluid.
o Increased blood volume.
o Increase blood pressure.

Question 57

Hormonal Control:

ANP/BNP System

Answer 57

o	Target Tissues: 
o	JG cells of kidney.
o	Hypothalamus.
o	Adrenal cortex.
o	Smooth muscle of arterioles (vasodilation).
o	Collecting ducts.
o	Mesangial cells (relaxation).
o	Effects: 
o	Decreased renin secretion:
•	Antagonizes the RAS system!
•	Decreased ADH release.
•	Decreased aldosterone release.
o	Increased surface area for filtration.
o	Vasodilation of afferent arterioles.
o	Decreased Na+ and H2O reabsorption in collecting ducts.
o	Increased GFR, so increased urine volume.
o	Decreased blood volume.
o	Decreased blood pressure.

Question 58

Summary of ANP/BNP System:

Answer 58

o BNP was first isolated from the brain, but is now known to be produced, stored and secreted from cardiac cells (primarily atria and left ventricle).
o BNP is used as a screening test for heart failure: if BNP > 80 picograms/mL, this indicates heart failure.
o In 2001, the FDA approved BNP as a med for treatment of severe HF (still in trials).
o Also a CNP: C-type natriuretic peptide (made by endothelial cells).
o Also URODILATIN: a natriuretic peptide made by the kidney tubular cells, acts as a local diuretic causing Na+ and water loss.

Question 59

Stages of Chronic Kidney Disease (CKD):

Answer 59

o Chronic kidney dz: GFR less than 60 mL/min for 3 or more months.
o Renal Insufficiency: GFR = 25 – 30 mL/min.
o Renal Failure: GFR = less than 15 mL/min.
o Significant loss of renal function to 10-25 percent of normal.
o ESRF (end-stage renal failure): only 10 percent of renal function remains.
o Hemodialysis.
o CAPD = continuous ambulatory peritoneal dialysis.

Question 60

CAPD:

Answer 60

o	Dialysate (isotonic) fluid is introduced into the peritoneal cavity.
o	Pt’s hypertonic plasma allows excess lytes and wastes to diffuse into the peritoneal cavity into the isotonic solution.
o	Waste fluid is then removed from the peritoneal cavity.

Question 61

Hemodialysis:

Answer 61

o Blood is passed through specialized porous tubing .
o Tubing is passed through an individualized solution that is HYPOTONIC to the patient’s blood.
o Excess solutes/lytes and wastes from pt’s blood diffuse from the blood into the solution.

Question 62

Systemic Effects of Chronic Kidney Disease:

Answer 62

o	Increased blood levels of nitrogenous wastes (urea):
o	Encephalopathy.
o	Anorexia, nausea.
o	Uremic “frost”.
o	Pruritus.  
o	Impaired secretion of lytes:
o	Hyperphosphatemia. 
o	Hyperkalemia.
o	Hypermagnesemia.
o	HTN from fluid retention.
o	Anemia.
o	Hypocalcemia.
o	Metabolic acidosis.

Question 63

Acute Renal Failure:

Answer 63

o Defined as an abrupt (within hours) reduction in renal function.
o Typically associated with OLIGURIA (less than 30 mL/hour of urine output or less than 500 mL/day).
o BUN and creatinine usually elevated.
o MOST TYPES OF ARF ARE REVERSIBLE if diagnosed and treated early enough!
o 1. pre-renal causes.
o 2. intrarenal causes.
o 3. post-renal causes.

Question 64

Etiologies of Acute Renal Failure:

Answer 64

o Pre-renal causes (55 percent of cases of ARF):
o Hypovolemia: Hemorrhage, severe dehydration, burns, inappropriate diuretics.
o Hypotension or hypoperfusion: Septic shock, cardiac failure, sudden stenosis of renal arteries
o Intrarenal causes (40 percent of cases of ARF)
o Acute Glomerulonephritis (infection, Type III hypersensitivities)
o Acute tubular necrosis:
• Rhabdomyolysis or Hemoglobinuria.
• Toxic meds (aminoglycoside antibiotics, i.e., gentamicin, neomycin).
• Toxic chemicals (radiocontrast media for x-rays, paint thinners, acetone, carbon tetrachloride).
• Heavy metal poisoning.
o Post-renal causes (5 percent of cases of ARF):
o Obstructive uropathies.
o Bilateral obstruction of both ureters or bladder obstruction.