Session 1: Kidneys & Urine Flashcards
Which part of the excretory system forms the urine?
Kidneys
Provides blood supply for the kidneys
Renal Artery
Provides blood drainage for the kidneys
Renal Vein
Each kidney contains how many Nephrons
1 - 1.5 million neohrons
Major type of Nephrons in the kidney
Cortical
Renal blood flow comes from?
25% of Cardiac output
Total Renal Blood Flow
1200 mL/min
Glomerulus filters out substances of what MW?
<70,000
Normal Glomerular filtration rate
120 mL/min
Specific gravity of ultrafiltrate
1.010
Ultrafiltrate same composition with plasma except for
Plasma protein, protein-bound substances, cells
The filtration barrier of the glomerulus is composed of
Fenestrated Endothelium
Basement membrane
Visceral epithelium
Fenestrated endothelium is also known as
Capillary endothelium
Basement membrane is also known as
Basal lamina
Visceral epithelium is also known as
Podocytes
This controls the regulation of blood flow to and within the glomerulus
Renin-Angiotensin-Aldosterone-System (RAAS)
What is the action of Angiotensin II
Vasodilation (Afferent art.)
Constriction (Efferent art.)
Reabsorption of Na
Release of Aldosterone & ADH
End effect of RAAS
Increase in systemic blood pressure
Example of substances that require active transport in tubular reabsorption
Glucose, amino acids, salts (PCT)
chloride (Asc. LOH)
sodium (DCT)
What substances are passively transported in tubular reabsorption
Water (All parts exc. Asc. LOH)
Urea (PCT, Acs. LOH)
Sodium (Asc. LOH)
Major site of reabsorption (Accounts for >65%)
Proximal Convoluted tubule
Glucose Renal threshold
160 - 180 mg/dL
8.88 - 9.99 mmol/L
What is the specific gravity of fluid leaving the PCT
1.010
Urine concentration begins where?
Descending & Ascending Loop of Henle
This is a selective process which serves to maintain the osmotic gradient of the medulla
Countercurrent mechanism
Explain what happens during the countercurrent mechanism
Water is removed via osmosis in the DESCENDING LOOP OF HENLE (Inc. SG)
Sodium & Chloride are reabsorbed in the ASCENDING LOOP OF HENLE (Dec. SG)
Final concentration begins where?
Late distal convoluted tubule and continues in the collecting duct
Reabsorption of water & sodium in the Distal Convoluted tubule and Collecting ducts is controlled by what?
Hormones (Aldosterone & ADH)
Aldosterone hormone responds to the body’s need for?
Sodium
Aldosterone is secreted & produced by?
Adrenal cortex
Action of Adrenal hormone
Sodium reabsorption
Potassium secretion
ADH/AVP hormone responds to the body’s need for?
Hydration (Water)
ADH/AVP is produced by?
Hypothalamus
ADH/AVP is secreted by?
Posterior pituitary gland
Action of ADH/AVP
Makes the walls of the DCT & CD (collecting duct) permeable or impermeable to water
Refers to the passage of substance from the blood to the filtrate for excretion
Tubular secretion
Major site of secretion
Proximal convoluted tubule
Purpose of tubular secretion
Elimination of products not filtered by the glomerulus
Regulation of the acid-base balance thru secretion of hydrogen ions
Variables used in computing eGFR using the Cockroft & Gault formula, except: (Age, Sex, Weight, BUN)
BUN
PAH Test is a test for?
Tubular secretion & Renal Blood Flow
Greatest source of error in any clearance procedure
Improperly timed urine specimen
Specimen of choice for clearance test
24 hour urine
Standard test used to measure the filtering capacity of the glomeruli
Clearance test
Originally used as the reference method for GFR
Inulin Clearance
Routinely used for screening of GFR
Creatinine clearance
Normal GFR
120 mL/min
Provide estimates of GFR based on the serum creatinine without urine creatinine
Calculated Glomerular Filtration Est8mates
Most frequently used formula for calculated glomerular filtration estimates
Cockroft & Gault (5th ed)
MDRD (6th ed)
Cockroft & Gault variables includes
Age, Sex, Body Weight
Additional variables for MDRD
Blood urea nitrogen, Ethnicity, Serum Albumin
Specific Gravity & Osmolarity tests are used for assessing
Tubular reabsorption tests/ Concentration tests
Fishberg & Mosenthal are examples of?
Water deprivation tests
Normal value for water deprivation test
Urine SG: 1.025
Urine osmolarity: 800 mOsm
Quantitative measurement of renal concentrating ability
Osmometry
1 mol (1000 mOsm’ will lower the freezing point by?
1.86 deg C
What are the 2 types of osmometers in the lab
Freezing point osmometer & Vapor pressure osmometer
Lipemic serum affects
Vapor & Freezing point osmometer
Lactic acid affects
Both vapor & freezing point osmometer
Volatile substances (ethanol) affects
Freezing point osmometer
Major organic component of the urine
Urea
Urine pH in RTA
Consistently alkaline
Major inorganic component in the urine
Chloride
Principal salt in the urine
Sodium Chloride
<0.8 g/d creatinine in the urine may mean
Improperly collected specimen
Urine preservative used for transporting urine specimen for culture
Boric Acid
Capacity for urine specimen container
50 mL
Labels on urine specimens must be placed
On the container and not the lid
After collection, specimens must be sent to the laboratory and tested within?
2 hours
Most routinely used method for preservation
Refrigeration at 2-8 deg c
Boric acid is bacteriostatic at?
18g/L
Excellent sediment preservative used for addis count
Formalin
This fixative used for cytology
Saccomano fixative
This method of preservation do not interfere with chemical tests
Refrigeration
This preservative is used for steroid & hormone analysis
Acids(HCl, glacial acetic acid)
Most commonly received specimen used for routine screening tests
Random urine
Ideal screening specimen and preferred specimen for pregnancy test
First-morning urine test
Preferred specimen for evaluating orthostatic proteinuria
First-morning urine
Preferred specimen for nitrite testing
First-morning urine
Also known as 2nd morning urine
Fasting urine
Preferred specimen for monitoring insulin therapy
2H - post-prandial urine
Addition of urine formed before the start of collection for 24 hour urine collection may lead to
Falsely elevated results
Failure to include urine produced at the end of collection period for 24 hr urine collection may lead to
Falsely decreased results
Specimen of choice for urobilinogen determination
Early afternoon specimen
12hr urine is used for
Addis count
Second specimen for Three-Glass Collection is used as
Control for bladder & kidney infection
In prostatic infection, the 3rd specimen will have
WBC/HPO count & a bacterial count of 10x that of the first specimen
This is a variation of three glass collection
Stamey-Mears Four-Glass collection
Expressed prostatic secretion for Stamey Meats collection is abnormal if
> 10 - 20 WBCs/HPF
In Pre-and Post-massage test bacteruiria is positive if
Post massage specimen is >10x the pre-massage count
This refers to the process that provides documentation of proper sample identification from the time of collection to the receipt of laboratory results
Chain of Custody (COC)
Who are the signatories of COC
collector, courier, laboratory, medical review officer, employer
Volume of urine specimen for Drug Specimen collection
30-45 mL
Temp of urine for drug specimen collection
32.5 to 37.7
Blueing agent is added to the ____________ to prevent specimen adulteration in drug specimen collection
Toilet reservoir
SG of urine specimen in drug specimen collection
1.002 - 1.035
