renal

what is glomerular filtration rate, what is it used for

what is glomerular filtration rate, what is it used for

volume of blood filtered per minute

• test for supected kidney issues

what are the five basic parts of the nephron

1. glomerulus

2. proximal convoluted tubule

3. loop of henle

4. distal convoluted tubule

5. collecting duct

what is in / not in the glomerulus

• ultrafiltrate

• lack HMW molecules

what is the function of the tubules

to reabsorb and secrete

total urine volume of 0.4-2.0 L / 24 hr

what factors facilitate glomerular filtration

• semipermeable basement membrane

• high pressure in glomerular capillaries as filtration occurs

function of proximal convoluted tubule

• reabsorption: returns valuable substances to the blood

• secretion: secretes products of metabolism

function of loop of henle

aids in reabsorption of water, sodium, chloride

function of distal convoluted tubule

adjusts electrolyte and acid base homeostasis

• ADH and aldosterone

function of collecting duct

final site of concentrating diluting urine

• controls reabsorption of water, sodium, chloride, urea

what is the excretory function of kidney

• getting rid of waste , non protein nitrogen (urea, uric acid)

• excess water and electrolytes

regulatory function of kidney

blood chemical homeostasis

• balance reabsorption and secretion

• Proximal tubule: reabsorption

• renal threshold (capacity of transport system)

what does the distal tubule do

• reabsorption and secretion

• plasma lytes and acid base balance

  • Na , K, H exchange

• aldosterone

describe aldosterone and what it is involved in

Na reabsorption, H and K secretion

• renin angiotensin system

• stimulated by LOW plasma Na and LOW blood flow

function of collecting ducts

ADH increase for water retention/reabsorption

main endocrine function of kidneys

• erythropoietin

  • RBC production

  • chronic renal failure → anemia

• renin-angiotensin

  • blood pressure and aldosterone secretion

what are the four endocrine functions associated with the kidneys

1. renin - angiotensin synthesis

2. erythropoietin - increases RBC number

3. 1, 25-dihydroxy vitamin D3 - active, phosphate and calcium balance and bone calcification

4. prostaglandins- renal blood flow

what are the glomerular diseases

• acute and chronic glomerulonephritis

• nephrotic disease

describe acute glomerulonephritis

• inflammed glomeruli, decreased capillary lumen

• rapid onset of hematuria nad proteinuria

describe chronic glomerulonephritis

• scarring and eventual loss of nephron function

• gradual uremia

describe nephrotic syndrome

• associated with massive proteinuria, hypoalbuminemia, edema, hyperlipidemia, lipiduria

what occurs in tubular diseases

• decreased excretion/reabsorption of the protein of certain substances or concentrating ability

example of tubulat disease

RENAL TUBULAR ACIDOSIS - affects acid base balance

what are renal caliculi

kidney stones

• crystallized substances

acute renal failure

sudden, sharp decline in renal function

can be reversed

soft tissue, MRI, dye allergy, toxin swallowed

chronic renal failure

gradual decline over time

flow rate can go down

medication

renal hypertension

decreased perfusion to kidneys, work hardy

what is the therapy for renal failure

dialysis : removing waste of blood through external, synthetic membrane

transplantation

what does the evaluation of renal function depend on

measurement of waste products in the blood that accumulate when kidneys begin to fail

what is clearance

rate at which creatinine and urea are removed from blood into urine

what is creatinine

endogenous product

• made at constant rate

• only made with glomerular filtration

what is the standard lab method to determine GFR

creatinine clearance rate

what is estimated GFR

• used to predict GFR

• based on serum creatinine

• does not require urine collection

what can be used for clearance measurements

• urea

• cystatin C

• creatinine

why is urea no longer used to measure clearance

not a full clearance assessment

what is cystatin C

LMW protein

• good marker for children and elderly

• may be more sensitive

what makes creatinine more helpful in helping an individual

within-subject variation < between-subject variation

what does GFR measure

• blood volume filtered per minute

• permeability of glomerulus

what do tubular lab tests observe

secretion and reabsorption

what are non-protein nitrogens

• urea

• creatinine

• uric acid

• amino acids

• nucleic acid wastes

what does BUN stand for

blood urea nitrogen

how is BUN made

protein catabolism

amino acid deamination → NH3 → urea cycle → urea

what is an increase in urea called, what can it lead to?

azotemia → uremia

what is BUN involved in

kidney

• urine excretion

• passive reabsorption

  • urine flow rate, hydration

what kind of types of azotemia are there

pre renal, renal , post renal

what is pre-renal azotemia

INC urea , WITHOUT , INC creatinine

• DEC renal blood flow

  • shock, congestive heart failure, DEC renal blood volume

• INC protein catabolism

  • high protein diet

  • fever, upper GI bleeding

• dehydration

  • urea moves with water

  • DEC water excretion → DEC urea excretion

what is renal azotemia

DEC renal function

• INC urea, INC creatinine , INC uric acid

• indicates glomerular / tubular disease

what is post renal azotemia

• urinary obstruction

  • nephrolithiasis (kidney stone)

  • prostate hypertrophy

  • severe infection

  • tumors

what methods are used to determine BUN

• coupled enzyme reaction

• indicator dye (ammonia + pH indicator)

• conductimetric

what is the reaction for urea

urea -urease→ NH4 + HCO3

BUN interferences

ammonia

• INC blood ammonia

what can cause increased blood ammonia

contaminated reagents, glassware, water

what specimen is used for BUN

• serum, plasma, pre-diluted urine

• NO anticoagulants that inactivate urease

  • Na fluoride , Na citrate AVOIDED

  • urease drives reaction

what is the reference range for BUN

6-23 mg/dL

how is creatinine made

creatine + ATP → creatine phosphate (high energy)

creatine phosphate + creatine → creatinine (waste)

why is plasma creatinine important

• renal function test

• constant level proportional to muscle mass

  • can be used as a delta check value : varies <10% / day

what is the reference range of creatinine

0.6-1.1 mg/dL

what is the creatinine clearance test

• estimates GFR

  • the creatinine produced = filtered = excreted

• clearance DEC linear to renal function DEC

• monitor/detect renal failure, nephrotoxicity

why is cystatin c clearance important

more accurate GFR in elderly or children

specimen for creatinine clearance

• 24 hr urine creatinine

• serum creatinine drawn at midpoint

what is measured for creatinine clearance test

• urine total volume

• serum creatinine

• urine creatinine

creatinine clearance test interferences

incomplete urine collection

what is the equation of corrected creatinine clearance

Cu/Cs x TV/min x 1.73/SA

what is the reference ranges for corrected creatinine clearance

male : 97-137 mL/min

female : 88-128 mL/min

how is creatinine used for delta checks

• changes around 10% daily

  • investigate , mislabeled sample

when can creatinine NOT be used for delta check

in renal failure or renal dialysis

how is creatinine used for TDM monitoring

nephrotoxic drugs

• gentamicin, tobramycin, amikacin, kanamycin (aminoglycosides)

• cyclosporin, salicylates

what is the specimen for analyzing CREATININE

serum, plasma, pre-diluted urine

what methods can be used for measuring creatinine

• jaffee reaction

• kinetic jaffe reaction

• enzymatic

what is the jaffe reaction

creatinine + alkaline picrate → red-orange

what causes false positive for creatinine

• hemolysis : RBC contents

• ketones, glucose, proteins, ascorbic acid

what causes false negative for creatinine assay

icterus

describe kinetic jaffe reaction , what interefers

• measure reaction rate

• more specific

• ONLY KETONES interefere

describe enzymatic creatinine method

• creatininase or creatine hydrolase

• greater specificity over Jaffe

how is kinetic jaffe different from regular jaffe?

kinetic is MORE specific , this is because ketones are its only interference

what is uric acid

purine metabolism endproduct

• dietary and endogenous

• liver converts purines → uric acid

how can food/diet produce uric acid

extra purines in diet or endogenous nucleic acid → production of uric acid

how is uric acid excreted by kidneys

• glomerulus filters

• proximal tubule reabsorbs most

• distal tubule secretes

uric acid reference range

M: 4.0-8.5 mg/dLF: 2.7-7.3 mg/dL

what kind of foods can trigger gout

foods high in purines

• beef, pork, lamb, beer, seafood, anchovies, spinach, cauliflower

what is gout

• hyperuricemia

• urates precipitaate in joint fluids, renal calculi

• males 30-50 years

• enzyme is deficient or missing

gout primary causes

increased purine production

gout secondary causes

alcohol and drugs

• INC dietary intake

what is associated with hyperuricemia

• INC cell breakdown

  • chemotherapy, LEUKEMIA

• chronic renal disease

  • DEC uric acid excretion

what is hypouricemia associated with

Fanconi syndrome

• defective tubular reabsorption

what are the coupled enzymatic reactions for uric acid

uric acid + O2 → allatonin + CO2 + H2O2

H2O2 + red chromogen → Ox.chromogen (color) +H2O

what interferes with uric acid

bilirubin, ascorbic acid (-)

what other methods are used for analyzing renal function

• urine electrophoresis

• beta2 microglobulin

• myoglobin

• microalbumin

what is urine electrophoresis for

• differentiates acute glomerular nephropathy and tubular proteinuria

• screens for abnormal monoclonal or polyclonal globulins

what does beta2 microglobulin test do

• assess renal tubular function in renal transplant patients with elevated levels indicating organ rejection

what does myoglobin test do

myoglobin clearance , early indicator of myoglobin induced renal failure

what is rhabdomyolysis

condition where myoglobin is excessively broken down

• kidneys cannot clear it

• can lead to acute renal failure

what is microalbuminuria

small amounts of albumin in the urine

what is microalbumin measurement used for

manage diabetes patients due to nephropathy risk

what level of urinary albumin concentration is predictive of diabetic nephropathy

50-200mg/24 hr

what is the risk of nephropathy with type 1 and 2 diabetes

type 1 risk : 30-45%

type 2 risk : 30%

what is involved in water balance

ADH

how is ADH secreted

INC plasma osmolality OR DEC intervascular volume

how does ADH increase water absorption

increases permeability of distal convoluted tubule and collecting ducts to water

what is involved in electrolyte balance

sodium and potassium

what is sodium

• controlled by renin- angiotensin- aldosterone hormonal system

  • excreted from kidneys