Intro to KIDNEY DISEASE AND RENAL LAB TESTS Flashcards
what is fxnal unit of kidney?
name 3 exchange processes in the nephron
● Kidneys receive blood supply from the renal arteries ○ 20% of cardiac output ● Functional unit of the kidney = nephron ○ 1 million nephrons/kidney ○ Filter the blood and produce urine ● 3 exchange processes in the nephron ○ Glomerular filtration ○ Reabsorption ○ Secretion
MAIN FUNCTIONS OF THE KIDNEYS (3)
● Regulation
○ Fluid volume, osmolarity, blood pressure, electrolyte concentrations and acidity
● Excretion
○ Metabolic end products, urea, toxins and drugs
● Synthesis
○ Renin, erythropoietin, Vitamin D3
ACUTE KIDNEY INJURY VS. CHRONIC
KIDNEY DISEASE
● AKI : An acute decrease in kidney function or Glomerular Filtration Rate (GFR) over a period of hours, days or even weeks and is associated with an accumulation of waste products and (usually) volume.
● CKD: A progressive loss of kidney function over a period of months or years
● Patients who experience AKI are at risk of developing CKD. Patients who have CKD are at risk of AKI
define azotemia
– an accumulation in the blood of nitrogenous waste products (blood urea nitrogen [BUN] and creatinine)
define hematuria
presence of blood in the urine
define oliguria
reduced urine output defined as approximately 100-400ml in 24 hours
define anuria
< 100ml of urine in 24 hours
define pyuria
presence of white blood cells or pus in the urine specifically defined as > 10 WBCs/ml
• Reflects the presence of inflammation more so than infection
Proteinuria
a persistent protein in the urine
• Reflects loss of the normal glomerular impermeability to filtration of plasma proteins
• Albuminuria
what is criteria for ideal marker for kidney fxn assessment
○ Stable concentration in plasma
○ Physiologically inert
○ Freely filtered at the glomerulus
○ NOT secreted, reabsorbed, synthesized, nor metabolized in the kidney
○ Amount secreted at the glomerulus is equal to the amount excreted in the urine
● Glomerular Filtration Rate (GFR) cannot be measured directly
what is SERUM CREATININE (50-110 UMOL/L)
- Metabolic by-product of muscle
- Serum concentration primarily determined by patient’s muscle mass
- Almost exclusively eliminated by glomerular filtration
- Inverse relationship between serum creatinine and kidney function
what is serum creatinine affected by?
Affected by: • Age • Gender • Weight • Malnutrition • Muscle Wasting • Amputation/Paralysis • Hydration ● Not a sensitive measure of kidney function ● Rate of change is variable depending on baseline function ○ Generally not immediate
what can lead to decreased SCr
● Paralysis, low activity level
● Elderly
● Decreased muscle mass
● Cirrhosis
what can lead to increased SCr?
● Renal causes
● Large dietary protein intake
● Vigorous exercise
● Increased muscle mass
what other ways can you assess kidney fxn?
● Serum Creatinine ● Estimation of Creatinine Clearance ○ Cockcroft-Gault Equation ● Estimation of GFR (Glomerular Filtration Rate) ○ Modification of Diet in Renal Disease (MDRD) ○ CKD-EPI ○ Schwarz Equation (Children) ● Measured 24-hour creatinine clearance
COCKCROFT-GAULT EQUATION
● Validation:
○ 249 patients, 96% male, age 18-92, with/without CKD
○ Stable Creatinine (fluctuation <20%), 2 x 24h measured CrCl
● Limited generalizability in many patients you’ll encounter
CREATININE CLEARANCE
equation?
what hapens to CrCl as age or weight increases?
● Cockcroft-Gault
●Cockcroft-Gault formula** (Using SI units!)
CrCl (ml/min)=
[140-age] x Wt (kg)/SCr (µmol/L) x 1.2 (for males)
■↓ CrCl with ↑ age
■↑ CrCl with ↑ weight
CREATININE CLEARANCE VS.
GLOMERULAR FILTRATION RATE
● Both are estimates of renal function
● CrCl
○ Surrogate marker of renal function
○ More often used to determine drug dosages
● GFR
○ Used to stage chronic kidney disease (more in upcoming lectures)
○ Reported by the lab when a serum creatinine is measured
BLOOD UREA NITROGEN (2.9-8.2
MMOL/L)
what is it dependent on?
Concentration of nitrogen (as urea) in the serum
• Dependent on urea production which occurs in the liver, glomerular filtration, and tubular reabsorption
• In conjunction with other laboratory data, it can be used to monitor hydration, renal function, protein tolerance and catabolism
• Also used to predict the risk of uremic syndrome in patients with severe renal failure
what causes elevated BUN? (4)
- high protein diets
- upper GI bleeding
- dehydration/volume depletion
- Acute kidney injury (and CKD)
what causes decreased BUN? (3)
• typically low BUN does not have pathophysiological
consequences
• May be low in malnutrition or who have profound
liver damage
• fluid overload (dilution)
URINALYSIS
3 things that macroscopic analysis loks at
General appearance:
Colour
• Varies from normally clear to dark yellow or amber, depending on the concentration of solutes
Turbidity – cloudiness or haziness • Can occur if urates or phosphates crystalize or precipitate in the urine
• Large numbers of WBC or RBC present
Foamy appearance
• Presence of protein or bile acids
URINALYSIS
MICROSCOPIC ANALYSIS normally how many: microorganisms RBC WBC epithelial cells casts crystals
▪ Microorganisms (zero to trace) ▪ RBC (1 to 3/HPF) ▪ WBC (0-2/HPF) ▪ Epithelial cells (0 or 1/HPF) ▪ Casts ▪ Cylindrical masses of glycoproteins that form in tubules ▪ Normal = a few clear casts ▪ Abnormal ▪ Hyaline (sometimes normal) ▪ Cellular casts (WBC, RBC, epithelial) ▪ Granular casts ▪ Crystals (normally = none)
CHEMICAL ANALYSIS
Urine Dipstick • Protein (zero to trace) • pH (4.6-8) • Specific Gravity (1.010-1.025) • Others: bilirubin, leukocyte esterase, nitrite, glucose and ketones Electrolytes • Urine Sodium (varies widely) • %FeNa - Fractional excretion of Sodium • Potassium (varies widely)
URINE PROTEIN/ALBUMIN
what does it assess?
○ Glomerulus is normally impermeable to large protein molecules such as albumin
○ Normally <100mg/24 hours
○ Three ways to measure protein - Urinary Albumin or Protein Excretion Rate (UAER or UPCR)
■ 24-hour urine collection
■ Estimated 24-hour urine excretion using a 4-hour timed urine collection
■ Urine dipstick
○ Albumin:Creatinine (ACR) Ratio (<2.0 mg/mmol)
○ Random urine spot test
○ Bottom line: Albuminuria/Proteinuria (specifically ACR) are helpful biomarkers to assess the progression of chronic kidney disease.
CAUSES OF TRANSIENT ALBUMINURIA
● Recent major exercise
● Urinary tract infection
● Febrile illness
● Decompensated congestive heart failure
● Menstruation
● Acute severe elevation in blood glucose
● Acute severe elevation in blood pressure
HOW SHOULD PHARMACISTS USE
RENAL LAB TESTS?
○Determine level of kidney function and
selection/dosing of certain types of medication.
○To monitor for adverse effects of some
medications
○Confirm type of acute kidney injury in
conjunction with patient history, other signs and
symptoms
○Confirm staging of chronic kidney disease and to
monitor progression
