Lab Approach to a Patient with Renal Disease Flashcards
Walt
Even though albumin is a small enough protein to pass thru the fenestrations of the renal corpuscle, it doesn’t because….
Why is maintaining protein in plasma important?
….albumin is negatively charged as well as the filter so it repels it back into the circulation
It helps maintain oncotic pressure
Albumin (protein) in urine tested on disptick is a sign of…
…nephrotic syndrome
___% of cardiac output passes thru the kidney per minute
25
Afferent arterioels are branches of the ____ arteries and each supply a single ____
interlobular, glomerulus
Efferent arterioles divide to form the ___
Peritubular microcirculation
Why should you avoid NSAIDS and ASA with vomiting and diarrhea?
These irreversibly block prostaglandins in the endothelium, preventing their release to act as dilators of the afferent arterioles that need to dilate to increase GFR
Factors that impact afferent or efferent arteriole tone (5)
- angiotensin II
- ADH/vasopressin
- prostaglandins
- Endothelins
- Epi/norepi
Endothelin definition
Proteins that constrict blood vessels and raise pressure, kept in balance by other mechanisms but when over-expressed contribute to hypertension
In order to compensate for lowered GFR pressure, we will vaso___ the afferent and vaso___ the efferent arteries
dilate, constrict
Sympathetic innervation of the bladder vs parasympathetic innervation of the bladder
Sympathetic allows for smooth muscle contraction of the bladder, parasympathetic allows for relaxing of internal urethral sphincter
With one kidney removed, blood flow in the remaining kidney will…
…compensate quite well nearly double within a few weeks
Increase hydrostatic pressure in Bowman’s capsule, often due to urethral obstruction, can cause…
…edema of the kidney
Urine volume is a poor indicator of _____
Renal dysfunction
Low urine output may be one of 3 categories
prerenal - the blood before the kidney
intrarenal - within the kidney
postrenal - in the ureters, bladder, or urethra
Polyuria, oliguria, and anuria values in mL/day
poly - >2L
oligo - <500mL
an - 0-100mL
A CBC is beneficial in evaluation of renal function for these 2 reasons
1) checks erythropoietin function
2) checks infection of kidney
The main organ responsible for balancing electroyltes in the body
kidney
Renal threshold
The amount of glucose (190-220mg/dL) of glucose that will result in sugar in the urine
BUN definition
Blood urea nitrogen, waste product of nitrogenous breakdown such as muscle in the body, useful measure in assessing kidney function
Creatinine definition
Breakdown of product of muscle in the body, useful measure in assessing kidney function
4 intrarenal disease possibilities
1) acute tubular necrosis
2) glomerular
3) vascular
4) tubulointerstitial
In a young patient (20’s) with hypertension, need to see if possible pathology source is…
…renal artery stenosis
3 common presentations of renal dysfunction
- hematuria
- proteinuria
- azotemia
Azotemia definition
Increased plasma conc. of BUN in bloodstream, without symptoms
In liver failure, there is a lack of conversion of ammonia to urea, and this can cause a brain disease called…
Hepatic encephalopathy
Uremia definition
Toxic effects felt as wastes accumulate in the body resulting from renal failure, sometimes being excreted thru the skin, typically causese elevated BUN and creatinine
What kills from renal failure?
-hyperkalemia causing arrhythmia of heart and eventual death
BUN normal value range
Between 10-20mg/dL at all times
Primary renal disease sees a ___ in urea, which causes a ____ BUN
increase, increase
What are 4 things that can decrease BUN?
- Overhydration
- liver failure
- neg nitrogen balance
- pregnancy
Normal creatinine level and elevated BUN level indicates a ___renal disease
Pre
BUN/Creatinine ratio
A useful measurement to determine the type of renal disease present
Creatinine is a direct reflection of ____ because it is always ____
Renal filtration rate, filtered
Only __renal disorders will affect creatinine levels
Intra
Rhabdomyolysis definition
An emergency disease that if left untreated leads to kidney failure, indicated by presence of myoglobin in urine, muscle pain, and weakness.
4 causes of elevated creatinine
- rhabdomyolysis
- acromegaly
- myesthenia gravis
- muscular dystrophy
Ceatinine clearance definition
A test that helps determine if kidneys are functioning normally by gauging the amount of creatinine in the urine compared to that in the blood
Serum creatinine concentration is the most common way to estimate ___, what is its relationship to that value?
GFR, the change in serum creatinine is inversely related logarithmically (i.e. creatinine from 1 to 2 is GFR 1 to .5)
24 hr urine collection definition, what are some issues with it?
Gold standard test for measuring kidney function, involves having patient pee first thing in morning and then collect every following urination up until completing first pee the next morning, patient compliance is the biggest issue with it
Normal range for GFR
85-115 mLs/min
Each year after age 40, there is a reduction of ___ mL/min per year of GFR
.75
Inulin clearance definition and function
A lab test using a compound called inulin that is only filtered by kidney, and is therefore a 100% accurate test of GFR, no longer done anymore
Healthy individuals without chronic illness can have unlimited ___ intake because it doesn’t have comorbidity associated with it. In theory, intake of this should equal ___ of it
Salt, excretion
Fractional excretion of Na+ in urine is extremely useful in distinguishing the most 2 common causes of acute kidney injury, what should it be in euvolemic patients in Na+ balance with normal renal function?
- prerenal azotemia
- acute tubular necrosis
<1%, if >1% can conclude it is acute tubular necrosis
UNLESS on diuretics
Specific gravity of serum, what is urine typically?
1.010, somewhere above that unless over hydrating then it will be diluted and lowered
Prerenal azotemia vs ATN BUN/Creatinine ratio
> 20, 10-20
Prerenal azotemia vs ATN urinalysis
normal or with hyaline casts, brown granular casts and cellular debris
Prerenal azotemia vs ATN specific gravity
> 1.020, =1.010
Prerenal azotemia vs ATN osmolarity
> 500 (conc.), <350
Prerenal azotemia vs ATN fractional excretion of sodium
<1, >1
Positive heme without positive blood on urinalysis, is indicative of this disease…
…rhabdo
+1 or +2 urine glucose on urinalysis is indicative of serum glucose levels of…
190-220
Leukocyte esterase on urinalysis indicates….
nitrite reduction on urinalysis indicates…
WBC in urine
Infection
Bright red blood tainted urine indicates the bleed is coming from the ___, while dark red indicates it is coming from the ____
lower urinary tract, kidney
A urine specimen that does not test positive via urinalysis for urobiligen is ___ a urine specimen that tests positive for bilirubin via urinalysis is ___
bad, bad
Sulfosalicylic acid test for protein definition
Tests for nonalbumin forms of protein in urine
Micral test for microalbuminuria definition
The gold standard test for early detection of glomerular disease, test for microalbumin in the urine
Microscopic urine analysis detects for these 3 things
- cells
- crystals
- casts
In a blood positive urinalysis, diabetic, kidney infected, metabolic, or kidney stone patient, what should be ordered alongside a urinalysis?
Microscopic urine analysis
Red cells on a microscopic urine analysis is indicative of what anatomic location? What about red cell casts and what disease? What about white cell casts and what disease? What disease state is about white blood cells in urine? What do muddy brown casts in urine indicate?
Renal pelvis down, nephron (glomerulonephritis), nephron (pyelonephritis), bladder infection, tubular damage
Blood present at start of stream and then becomes clear indicates…
Blood present through the middle of the stream indicates…
Blood present at the end of the stream indicates…
- urethral bleeding
- bladder or above
- prostate and trigone bleeding
Common prerenal diseases (4)
- azoemia
- congestive heart failure
- hypovolemia
- hemorrhage
Healthy BUN:Cr ratio
between 10:1 and 20:1
Common postrenal kidney diseases (2)
- severe acute tubular necrosis
- obstruction
Common intrinsic renal diseases (3)
- glomerulonephritis
- proteinuria
- nephrotic syndrome
Orthostatic proteinuria
Benign condition frequently seen in children where proteinuria is seen after periods of standing but not sitting, can be tested for by sampling first urine in morning
What kidney conditions would you use ultrasound to detect? (3) Why is this the preferred imaging modality?
- hydronephrosis
- kidney stone
- renal artery stenosis
No radiation
Significant bacteruria is when there are ____ml of a single organism
100,000 (nonpregnant patient)
