Renal Function Test Flashcards
(28 cards)
approximately 40% of the filtered urea is reabsorbed, normal values were adjusted to reflect the reabsorption, and patients were hydrated to produce a urine flow of 2mL/min to ensure that no more than 40% of the urea was reabsorbed
Urea Clearance
Involves injection of radionucleotides; not only determines GFR but also enables visualization of filtration in one or both kidneys
Radioisotope Clearance
Radioisotope Clearance:
EXOGENOUS or ENDOGENOUS?
Exogenous
dissociates from HLA at a constant rate and is rapidly removed from the plasma; not reliable in patients with history of immunologic disorders or malignancy
β-2 microglobulin Clearance
small protein (MW 13,359) produced at a constant rate by all nucleated cells, readily filtered by the glomerulus, and reabsorbed and broken down by the renal tubular cells; serum marker recommended for pediatric patients, diabetics, elderly, and critically ill patients
Cystatin C Clearance
reference method; extremely stable substance that is neither reabsorbed nor secreted by the tubules
Inulin Clearance
Inulin Clearance:
EXOGENOUS or ENDOGENOUS?
Exogenous
It is not a normal body constituent, however, and must be infused by IV at a constant rate throughout the testing period
Inulin Clearance
Recommended method and gives an estimation of the degree of renal impairment by disease
Creatinine Clearance
Creatinine Clearance:
EXOGENOUS or ENDOGENOUS?
Endogenous
Equation used to get the creatinine clearance
C = UV/P
tests to determine the ability of the
tubules to reabsorb the essential salts and water that have been non-selectively filtered by the glomerulus.
Concentration test
In Concentration test:
The ultrafiltrate that enters the tubules has a SpGr of 1.010; therefore, after reabsorption one would expect the final urine product to be (MORE/LESS?) concentrated.
more
patients are deprived of fluids for 24 hours prior to measuring the specific gravity
Fishberg Test
compares the volume and SG of day and night samples
Mosenthal Test
used to measure the osmolarity of serum and urine by comparing a colligative property value of the sample with that of pure water
Osmometry
Normal Values or serum and urine in mOsm
275 – 300 mOsm (serum)
50 – 1400 mOsm (urine)
important in determining whether DI is caused by decreased ADH production or lack of renal response to ADH.
U:S Osmolarity Ratio
U:S Osmolarity Ratio
a) should be at least ____ under normal random conditions
b) should reach ____ after controlled fluid intake or ADH injection
a) 1:1
b) 3:1
an expansion of the U:S Osmolarity Ratio; used to determine the ability of the kidneys to respond to the state of body hydration
Free Water Clearance
Calculation of Free Water Clearance
CH2O = V - Cosm
CH2O = free water clearance V = urine volume in mL/min
Free Water Clearance Interpretation of Results
+ value: ___________
0 value: ___________
- value: ___________
+ value: excess water is excreted
0 value: no renal concentration/dilution would be taking place
- value: : less than the necessary amount of water is being excreted
Tests to measure tubular secretion of nonfiltered substances and renal blood flow are closely related in that total renal blood flow through the nephron must be measured by a substance that is secreted rather than filtered through the glomerulus
Tubular Secretion and Renal Blood Flow Tests
not currently performed due to difficulty in standardization and interpretation of results
Phenolsulfonphthalein (PSP)
