Renal System Flashcards
Urinary system includes = ?
Renal System
Urinary System Includes:
(a) Two kidneys
- Paired organs lying the rear wall of the abdominal cavity, at level T12 to L3
- Each kidney weighs about 115-170 grams (1% of the body weight), yet receive 20% of cardiac output
(b) Two ureters
(c) Urinary bladder
(d) Urethra
Function of Kidneys = ?
Renal System
Function of Kidneys:
(1) Filter the blood and produce urine
- Removal of metabolic waste products
(2) Regulation of plasma ionic composition
(3) Regulation of plasma volume
(4) Regulation of plasma osmolarity
(5) Regulation of plasma hydrogen ion concentration (pH)
(6) Secondary functions:
- Secrete erythropoietin, which stimulates erythrocytes production by bone marrow.
- Secrete renin, necessary for production of angiotensin 2, a hormone which regulates salt and water balance- control of blood pressure.
- Activate vitamin D3, an important factor in regulating calcium and phosphate levels.
Three areas of macroscopic anatomy of kidneys are = ?
Renal System
Macroscopic Anatomy of Kidneys:
(1) Cortex
- Outer region, just under the kidney capsule
(2) Medulla
(3) Papilla
- Innermost tip of inner medulla and empties into pouch called calyces and then renal pelvis which are extensions of ureter.
Anatomy of Nephron:
- Nephron consist of = ?
Renal System
Anatomy of Nephron:
(a) Nephron:
- Functional unit of Kidney, 1 million nephrons
- Nephron consist of renal corpuscles and renal tubule.
(b) Renal corpuscles:
- Bowman’s capsule
- Glomerulus (glomerular capillary network)
(c) Renal tubule:
- Lined with epithelial cells
- Filtrate travels and becomes modified (absorption and secretion) in the formation of urine
Two classes of nephrons = ?
Renal System
Nephron:
(a) Two classes of nephrons (based on location).
(1) Superficial / cortical nephron:
- Located almost entirely within the cortex
(2) Juxtamedullary nephron:
- 15-20% of all nephrons
- Renal corpuscle is located near the border between the cortex and medulla.
Glomerular Filtration = ?
Renal System
Glomerular Filtration:
- First step in the formation of urine
- As renal blood flow (RBF) enters the glomerular capillaries, a portion of blood is filtered into the Bowman’s space which is the first part of the nephron.
- Fluid that is filtered is called filtrate/ glomerular filtrate / ultrafiltrate.
- Ultrafiltrate contains water and all of the small solutes of the blood but it does not contain blood cells and proteins.
Glomerular Filtration Pressure:
Renal System
Glomerular Filtration Pressure: For glomerular capillaries, net filtrate pressure always favor filtration so direction of fluid movement is always out of the capillaries.
(a) Pressures that drive fluid movement across capillaries are the starling forces.
(b) Two hydrostatic (one in capillary blood and one in interstitial fluid) and two oncotic pressure (one in capillary blood and one in interstitial fluid).
(1) Glomerular capillary hydrostatic pressure:
- Hydrostatic pressure in the glomerular capillaries, (PGC), and Bowman’s capsule oncotic pressure (oncotic pressure in the bowman’s capsule (πBC).
- Favors filtration
- = PGC + πBC = 60 + 0 = 60 mmHg
(2) Bowman’s capsule hydrostatic pressure:
- Hydrostatic pressure in the bowman’s capsule (PBC), and Glomerular oncotic pressure (oncotic pressure in the glomerular capillaries (πGC).
- Opposes filtration
= PBC + πGC = 15 + 29 = 44 mmHg
(c) Oncotic pressure: pressure due to presence of proteins in the blood
(d) Net ultrafiltrate pressure, the driving force, is algebraic sum of 4 starling pressures.
(e) For glomerular capillaries, net filtrate pressure always favor filtration so direction of fluid movement is always out of the capillaries.
Glomerular Filtration Rate:
Renal System
Glomerular Filtration Rate:
(a) Glomerular filtration rate (GFR)
- Volume of plasma filtered per unit of time is called Glomerular Filtration Rate
(b) GFR = Kf [(PGC − PBC) − πGC]
- Kf = filtration coefficient, is the water permeability
- Water permeability per unit of surface area
- Total surface area
- PGC Capillary hydrostatic pressure
- PBC Bowman’s capsule hydrostatic pressure
- πGC Capillary blood oncotic pressure
(c) National kidney foundation, normal GFR ranges from 120-130 ml/min/ 1.73 m2 in young adults
- Varies according to age, sex, and body size
declines with age
Effect of constriction of afferent and efferent arteriole:
- Constriction of afferent arteriole = ?
- Constriction of efferent arteriole = ?
- Increased plasma protien concentration = ?
- Decreased plasma protien concentration = ?
- Constriction of the ureter = ?
Renal System
Effect of constriction of afferent and efferent arteriole:
- RPF = renal plasma flow
- GRR = glomerular filtration rate
(a) Constriction of afferent arteriole:
- RPF = decreased
- GFR = decreased
- Filtration Fraction (GRF/RPF) = no change
(b) Constriction of efferent arteriole:
- RPF = decreased
- GFR = increased
- Filtration Fraction (GRF/RPF) = increased
(c) Increased plasma protien concentration:
- RPF = no change
- GFR = decreased
- Filtration Fraction (GRF/RPF) = decreased
(d) Decreased plasma protien concentration:
- RPF = no change
- GFR = increased
- Filtration Fraction (GRF/RPF) = increased
(e) Constriction of the ureter:
- RPF = no change
- GFR = decreased
- Filtration Fraction (GRF/RPF) = decreased
Basic Exchange Processes:
Renal System
Basic Exchange Processes:
(a) Filtration:
- Across glomerular capillaries into Bowman’s space.
- Glomerular filtration is the bulk flow of protein-free plasma from the glomerular capillaries into the Bowman’s capsule.
- Amount of substance filtered into Bowman’s space per unit time is called filtered load
(b) Reabsorption:
- Water and many solutes (sodium, chloride, bicarbonate, lactate, citrate) are reabsorbed from the glomerular filtrate into the peritubular capillary.
- Transporters in the membrane of epithelial cells.
(c) Secretion:
- Few substances like organic acids, bases, potassium are secreted from peritubular capillary blood to tubular fluid. Mechanism of excreting substances in the urine involves transporters in the membrane of epithelial cells lining the nephron
(d) Excretion: The net result or sum of processes of filtration, reabsorption and secretion
- Excretion: (Filtration- Reabsorption) + secretion
(e) Notes:
- Excretion rate is the amount of substance excreted / unit of time.
- Comparison of filtered load and excretion rate helps determine whether a substance has been reabsorbed or excreted.
Normal values for routine urinalysis = ?
Renal System
Normal values for routine urinalysis:
- Color - yellow amber
- Appearance - clear to slightly hazy
- Volume - 600-2500ml/ 24 hour
- Glucose - negative
- Ketones - negative
- Protein - negative
- Red blood cells - negative
- White blood cells - negative
Renal function tests include = ?
Renal System
Renal Function Tests:
(1) GFR:
- Measured clinically by colleting timed sample of blood and urine, may be done on a 24 hour basis- complicated.
- More labs doing eGFR (estimated GFR)
- Is a measured plasma creatinine in a mathematical formula accounting for age, sex and race
(2) Serum creatinine (creatinine levels in the blood):
- Waste product of muscle metabolism
- Normal 0.6-1.2 mg/dL
- Helps calculate GFR and estimate the functional capacity of the kidney.
- If serum creatinine doubles, indicates that GFR has fallen to one half.
(3) Blood Urea Nitrogen (normal: 7-20 mg/dl):
- Urea nitrogen is the end product of protein metabolism.
- Indicator of liver and kidney function
- 2/3rd of renal function is lost before a significant rise in BUN levels occur.
(4) Ultrasonography:
- Reflection of ultrasonic waves to visualize the deep structures of the body
(5) Radiologic examination (CT, MRI, X ray films):
- Size, shape, position of kidneys, space occupying lesions.
- IV pyelogram - x ray films taken as dye moves
Pathologic indications of altered urinary elimination = ?
Renal System
Pathologic Indications of Altered Urinary Elimination:
(a) Proteinuria: Protien in urine
- Lab = 150 mg/24-hour sample
- Renal failure
- Nephrotic syndrome preeclampsia
- Renal a./v. thrombosis
- Tubulopathy
(b) Glucosuria: Glucose in urine
- Lab = >130 mg/24-hour sample
- Diabetes mellitus
(c) Ketonuria: Ketones in urine (acetone, acetoeactic acid, beta-hydroxybutyric acid).
- Lab = Acetone 20 mg/dl (small), 30-40 mg/dl (moderate), >80 mg/dl (large)
- Diabetes mellitus
- Ketoacidosis
- Starvation
(d) Hematuria: Red bloodcells in urine.
- Lab = >1 RBC/HPF
- Glomerular damage
- Tumors
- Kidney trauma
- UTI
- Acute tubular necrosis
- Urinary tract obstruction
(e) Pyuria: White blood cells in urine
- Lab = 2 WBC/HPF, (+) leukocyte esterase, > 100,000 CFU
- Upper & lower UTI
- Acute glomerulonephritis
- Renal calculi
(f) Bacteruria: Bacteria in urine
- Lab = (+) nitrates
- Upper and lower UTI
Cystic Kidney Disease:
- Characterized by = ?
*
Renal System
Cystic Kidney Disease:
(a) Polycystic kidney diseases are group of disorders characterized by fluid filled sacs or segments that have their origin in the tubular structures of the kidney.
(b) Single / multiple; cysts of varying size (microscopic to several cms) - replace functional tissue - progressive nature - loss of renal function- renal failure.
(c) May be inherited or acquired (most forms are hereditary)
(d) Autosomal dominant = most common
Autosomal dominant polycystic kidney disease (ADPKD):
- What gene is effected = ?
Renal System
Autosomal dominant polycystic kidney disease (ADPKD):
- Autosomal dominant polycystic kidney disease (ADPKD), account for 10% of the cases of end stage renal disease (ESRD).
- 4th leading cause of ESRD; usually appear between the ages of 30-40 years
- Thousands of large fluid filled cysts are derived from every segment of the nephron.
- Mutation in PKD1 (85%) and PKD 2 (15%) gene.
- Progression is slow
- Kidneys enlarged and contours of the kidney distorted
Nephrotic syndrome:
- What is it = ?
- Pathogensis = ?
Renal System
(a) Inflammation occludes the glomerular capillary lumen and damage the capillary wall.
(b) Collection of clinical findings resulting from increase in glomerular permeability and loss of plasma proteins in the urine.
- Massive proteinuria (>3.5 g/day)
- Hypoalbuminemia (largest proportion lost is albumin)
- Generalized edema
- Dyspnea
- Hyperlipidemia (cholesterol >300mg/dL, triglycerides are elevated, LDLs are elevated), increased risk of atherosclerosis
- Lipiduria
- Urine: dark, cloudy
(c) Pathogensis:
- Hyperlipidemia due to compensatory protein synthesis including lipoproteins.
Pass too much protein.
Chronic kidney disease (CKD):
- Most common causes = ?
Renal System
Chronic kidney disease (CKD):
(a) In US, more than 30 million people (NIH) or 1 in 9 adults have CKD
(b) Gradual irreversible loss of renal function
(c) Alteration of kidney function or structure for greater than or equal to 3 months duration.
(d) Most common causes are:
- Diabetes Mellitus (44%)
- Hypertension (27%)
- Glomerulonephritis (8%) (inflammation of glomeruli)
- Cystic kidney disease and other (5%)
- Urine obstructions, renal artery stenosis, toxin exposure (lead, chemotherapy, NSAIDS), sickle cell disease, SLE, smoking, aging.
Chronic kidney disease (CKD):
- What is it = ?
Renal System
Chronic kidney disease (CKD):
(a) Gradual loss of nephron function with progressive deterioration of GF,
- Tubular reabsorption capacity and endocrine function of kidneys.
(b) Kidneys unable to adequately regulate fluid volume, electrolytes, pH balance, vitamin d conversion, hormone synthesis, remove metabolic waste products from blood
(c) Normal adult GFR is 125 ml/min
(d) CKD - defined as GFR less than 60ml/min for 3 months or longer.
(e) Kidney failure: NFK define kidney failure as:
- GFR <15 mL/min, accompanied by most of signs/ symptoms of uremia.
- Need to start renal replacement therapy (dialysis or transplantation).
Chronic kidney disease (CKD):
- Stages = ?
Renal System
Chronic kidney disease (CKD) - Stages:
Stage #1:
- No overt symptoms of impaired renal function are evident
- Unaffected nephrons undergo structural and physiologic hypertrophy to make up for the lost ones (kidneys have amazing compensatory capability)
- Early manifestations include hypertension and anemia
- Increase in BUN and creatinine
Stage #2:
- Small amount of albumin is excreted in the urine
- With proper control of hypertension and blood glucose levels- might not progress
Stage #3
- Albumin levels increase in urine and decrease in blood - edema
- Levels of BUN and creatinine increase, accumulation of waste products in the blood called azotemia.
Stage #4 & #5:
- Complications appear
- Proteinuria
- Progressive increase of BUN and creatinine levels , patients are hypertensive
Stage #5:
- Kidneys cannot excrete toxins, maintain pH, fluid electrolyte function, secrete important hormones (renin, vitamin D, erythropoietin).
- Uremia (toxins not removed from blood): nausea, vomiting, anorexia, lethargy, sensory and motor neuropathy, impaired heart function, seizures, all systems affected- with no treatment- coma/ death.
HemoDialysis:
- What is it = ?
HemoDialysis:
(a) Complications: infection, catheter malfunction, dehydration caused by excess fluid removal
Peritoneal Dialysis:
Renal System
Peritoneal Dialysis:
(a) Peritoneal dialysis (can be done independently at home)
(i) Continuous ambulatory peritoneal dialysis
- Dialysis fluid is inserted into the abdomen, followed by drainage, repeat with fresh dialysis up to four times a day.
- Can move normal
(ii) Continuous cycle assisted peritoneal dialysis
- Special machine fills and empties abdomen of dialysis fluid
- At night during sleep, might take 7-10 hours
(iii)Serious complication: peritonitis
