Shoeny Renal 1 Flashcards
What is the nephron composed of?
Glomerulus Proximal Tubule Loop of Henle Distal Tubule Collecting Duct
What is the function of the Nephron?
Filtration
Blood enters from the renal artery into the afferent arteriole and exits via the efferent arteriole
Substances up to what size can pass through the renal capillaries?
40 K Daltons
Larger substances such as proteins and RBCs, do not usually pass
When might substances larger than 40K daltons pass through the renal capillaries?
Renal damage
The proximal tubule reabsorbs large quantities of?
H20, along with glucose, uric acid, Na, Cl and HCO3
Loop of Henle, after the proximal tubule, reabsorbs what?
Further reabsorbs Na, Cl, and H20
The distal tubule controls what substances from going into the collecting duct?
Distal tubule controls excretion of Na, K, HC03, and H into the collecting duct
The collecting duct regulates the amount of water in the urine to the effect of what hormone?
ADH (anti diuretic hormone)
Substances enter the the nephron through _____. Substances are reabsorbed from the tubule back to circulation via the __________
Substances enter the nephron through peritubular blood (secretion) or from interstitital space.
Substances are reabsorbed from the tubule back to the circulation via the peritubular vasculature.
What are 3 renal function tests?
BUN
Creatinine
Urinalysis
BUN measures what?
Measures concentration of nitrogen (urea) in the serum.
This is a marker of protein metabolism.
When is BUN elevated?
Elevated in renal failure but other causes as well (CHF, acidosis)
Normal range 8-20mg/dl
What is Creatinine?
Catabolic product of creatine-phosphate-skeletal muscle contraction.
Metabolic product of muscle creatine, day to day variation is negligible in healthy kidneys. Rise in creatinine is due to kidney dysfunction or damage- Shows up as decrease in GFR.
Creatinine production depends on what?
Daily production depends on muscle mass
Creatinine is excreted entirely by?
the Kidneys, directly related to renal function
What are normal levels of Creatinine? Elevations suggest what?
Normal is 0.5-1.1 mg/dl
Elevations suggest chronicity of renal disease.
How does Creatinine correlate with renal function?
Creatinine increases are inversely related to renal function.
Doubling of creatinine = 50% decrease in renal function.
Who would have a higher creatinine level? Who would have a lower creatinine level?
Muscle mass matters. People with greater muscle mass generally have a higher creatinine level.
People with lower creatinine would be people with lower muscle mass - neurogenic complications - MS, post stroke, women (generally)
What is glomerular filtration rate? What is the gold standard to measure glomerular filtration rate?
Glomerular filtration rate is an assessment of kidney function occurs in different ways, using the presence of symptoms and signs, as well as measurements using urine tests, blood tests, and medical imaging
Gold standard = Inulin filtration rate
Actuality = Creatinine clearance
What is creatinine clearance an approximation of? What are normal ranges?
Creatinine clearence is an approximation of GFR.
Normal ranges, Male = 107-140, Female = 90-107
What is Creatinine clearance used for?
Assessing kidney function in acute or chronic renal failure.
Monitoring effects of drug therapies.
Monitoring therapeutic drugs and determining dosage.
How do you test creatinine clearence?
Requires 24 hour urine collection
Serum creatinine drawn within 24 hours of urine collection
Creatinine clearence = (Ucr mg/dl x Urine volume ml/min)/(PCr mg/dl)
What is the Cockcroft-Gault Equation?
This estimates creatinine clearance without 24 hour urine studies.
This is useful for renal dosing of medications.
CrCl (ml/min) = (140-age) x wt/(cr x 72)
Multiply by 0.85 if women to correct for mm mass.
What is the MDRD equation? What does it incorportate into its equation?
Modification of Diet in Renal Disease
Incorporates age, sex, and ethnicity into equation.
GFR mls/min = 1.86 x PCr x Age
multiply by 0.742 if female, multiply by 1.210 if African American.
What does urinalysis consist of?
Consists of dipstick and microscopic analysis.
Color and clarity part of report.
What do the strips measure Urinalysis?
Strips measure specific gravity, pH, glucose, protein, ketones, blood, bilirubin, nitrite, and leukocyte esterase.
What is normal pH of the urine?
Normal 4.5-8
Must be freshly voided to be reliable
Acidic urine vs Alkalinic urine and bacteria
Acidic urine deters bacterial growth
Alkalinic urine - UTI, renal tubular defects.
What is specific gravity and what does it tell you?
Measure of concentration of particles. Correlates well with osmolarity. Sodium is the main contributor to specific gravity.
High = concentrated - dehydration Low = dilute - renal failure, hydration
Is it normal to have ketones in your urine?
No, normal = negative for ketones
What Ketone is measured in the ketone test?
Acetoacetic acid, no hydroxybutyric acid.
Monitors high protein diet.
What disease might have positive ketones in their urine?
May be positive in uncontrolled diabetes.
Ketoacidosis,
Excessive vomiting and dehydration.
Is it normal to have glucose in the urine?
No, normally negative
If glucose is present in urine what does this reflect?
If present in urine, reflects amount of hyperglycemia in plasma.
Renal threshold is generally >300mg/dl
Is it normal to have protein in the urine? What does a protein level in the urine tell you?
No - normally negative
This is a sensitive indicator for kidney function.
If glomerular membrane is injured, protein is elevated.
What are the findings of Nephrotic syndrome?
Proteinuria and edema.
What diseases is proteinuria present in?
Protein elevated in multiple myeloma, pyelonephritis, diabetic nephropathy, glomerulonephritis, CHF, lupus.
Is it normal to have bilirubin and urobolinogen in the urine?
No - normally negative
When does Bilirubin and urobilogen show up in the urine?
Elevated in liver damage, obstruction of the bile duct.
Stage 1 of CKD has a GFR of?
90 or higher, 90-100% of kidney functioning
Stage 2 of CKD has a GFR of?
89-60, 89-60% of kidney function
Stage 3a has a GFR of?
59-45%
Stage 3b has a GFR of?
44-30%
Stage 4 CKD has a GFR of?
29-15%
Kidney failure is GFR less than?
15%
Is it normal to have blood in the urine?
Normal is negative to trace. May not match microscopic as dipstick will pick up lysed cells.
If RBCs are present on a UA, likely protein will be positive as well.
What causes false positive for blood in the urine?
Myoglobin.
What can cause a false negative for blood in the urine?
High doses of Vitamin C can cause false negative.
Painless hematuria with history of smoking makes you think of what?
Bladder carcinoma
Hematuria can be caused by?
Infection, stones etc.
What is luekocyte eseterase? What can it detect in urine? When might it be positive?
Leukocyte esterase is accurate in detecting WBC’s in the urine - 90% accurate
Positive in urinary tract infections.
What is Nitrite? Where would it be positive?
Another test that would be positive in urinary tract infections.
Cause of nitrate being converted to nitrite by the bacteria present. Gram negative organisms produce reductase - like E. coli
What can interfere with a Nitrite test?
Color of urine
What does a Microscopic UA show?
WBC, RBC, epithelial cells and casts - normal - none seen
WBC’s in a microscopic UA means?
infection
RBC in microscopic UA means?
infection, renal calculi
Eosins in microscopic UA mean?
Interstitial nephritis
Hyaline casts present when?
Normal after exercise, can be present with chronic renal failure
Red cell casts in the urine represent what?
Glomerulonephritis, SBE
White cell casts in the urine are from?
Pyelonephritis
Epithelial cells in the urine?
Tubular necrosis
Granular cells in the urine?
Nephrotic syndrome, lead toxicity, glormerulonephritis
Waxy cells in the urine?
Renal failure, - acute tubular necrosis
Crystals in the urine can be a marker of?
stones
