Download Kidney functions

Kidney Function Tests
(KFT)
Related terms
• Nephr/o, ren/o
• Hydro/o
• Cyst/o
Kidney
Nephritis
Water
Bladder
• Cystitis inflammation of bladder
• Cystectomy removal of bladder
• Pyel/o
• Ur/o -uria
Renal collecting duct
Urine
• Hydronephrosis Abnormal condition involving back up
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of urine into the kidney
Nephrosis A noninflammatory degenerative disease of the
renal tubules
Nephrolith A kidney stone .
Urethritis Inflammation of the urethra, the final pathway
for urine in both sexes.
Nocturia Frequently getting up and urinating during the
night.
Enuresis Involuntary release of urine, most often in
reference to "bedwetting”.
Anuria Complete stop of urine flow
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Dysuria Painful urination
Nocturnal enuresis Bed wetting during sleep
Nocturia Urination at night, not bed wetting
Oliguria Scanty (small) production of urine
Polyuria Condition of excessive urination
Urinepyuria high pus cells in urine
Hydronephrosis Dilation and pooling of urine in
the renal pelvis and calyces of one or both kidneys
caused by an obstruction of urine flow.
• Urinary tract infection (UTI)
Invasion of pathogenic organisms (commonly bacteria)
in the structures of the urinary tract, especially the
urethra and bladder
– Symptoms include dysuria, urinary frequency, and
malaise
Kidney functions :
 Regulation of water and electrolyte balance.
 Regulation of acid base balance.
 Regulation of arterial blood pressure.
 Excretion of metabolic waste products and
foreign chemicals.
 Hormonal Function : Secretion of
erythropoietin
Functional units :
The nephron is the functional unit of the
kidney . Each kidney contains about one
million nephrons.
The nephron is composed of glomerulus and
renal tubules .
The nephron performs its function by ultra
filtration at glomerulus and secretion and
reabsorption at renal tubules.
Nephrons and Blood vessels
Renal diseases :
 Many diseases affect renal function.
 In some, several functions are affected.
 In others, there is selective impairment of
glomerular function or one or more tubular
function .
 Most types of renal diseases cause
destruction of complete nephron.
Routine kidney function test include the
measurement of :
Serum creatinine.
Creatinine clearance.
Serum urea.
Both serum creatinine and creatinine clearance are
used as kidney function tests to :
Give an idea about the severity of the disease.
Confirm the diagnosis of renal disease.
Follow up the treatment.
Serum creatinine (55-120 mol/L in adult):
• Creatinine is the end product of creatine
catabolism .
• 98% of the body creatine is present in the muscles
where it functions as store of high energy in the
form of creatine phosphate.
Creatinine in the plasma is filtered freely at the
glomerulus and secreted by renal tubules (10 % of
urinary creatinine).
However, creatinine is not reabsorbed by
the renal tubules.
Plasma creatinine is an endogenous
substance not affected by diet.
Plasma creatinine remains fairly constant
throughout adult life.
Creatinine clearance :
• The glomerular filtration rate (GFR) provides a
useful index of the number of functioning
glomeruli.
• It gives an estimation of the degree of renal
impairment by disease.
• Creatinine clearance is usually about 110 ml/min in
the 20-40 year old adults.
• Clearance is the volume of plasma cleared from the
substance excreted in urine per minute.
• It could be calculated from the following equation:
Clearance (ml / min ) =
U
x
P
U = Concentration of creatinine in urine  mol /l
V = Volume of urine per min
P = Concentration of the substance in serum  mol /l
V
Serum creatinine is a better kidney function
test than creatinine clearance because :
• Serum creatinine is more accurate.
• Serum creatinine level is constant
throughout adult life.
Creatinine clearance is only recommended in
the following conditions:
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Patients with early ( minor ) renal disease.
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Assessment of possible kidney donors.
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Detection of renal toxicity of some nephrotoxic
drugs.
Serum Urea ( 2.54-6.6 mmol/L) in adult:
•Urea is formed in the liver from ammonia released
from deamination of amino acids.
•As a kidney function test, urea is inferior to serum
creatinine because:
•High protein diet increases urea formation.
•Any condition of increased proteins catabolism
will increase urea formation.
Dialysis
• In medicine, dialysis (from Greek "dialysis", meaning
dissolution, "dia", meaning through, and "lysis", meaning
loosening) is primarily used to provide an artificial
replacement for lost kidney function in people with renal
failure.
• Dialysis may be used for those with an acute disturbance in
kidney function (acute kidney injury, previously acute renal
failure) or for those with progressive but chronically
worsening kidney function–a state known as chronic kidney
disease stage 5 (previously chronic renal failure or endstage kidney disease).
Hemodialysis
• In hemodialysis, the patient's blood is then pumped
through the blood compartment of a dialyzer,
exposing it to a partially permeable membrane.
• The dialyzer is composed of thousands of tiny
synthetic hollow fibers.
• The fiber wall acts as the semipermeable
membrane. Blood flows through the fibers, dialysis
solution flows around the outside the fibers, and
water and wastes move between these two solutions
Hemodialysis
• The cleansed blood is then returned via the circuit
back to the body.
• Ultrafiltration occurs by increasing the hydrostatic
pressure across the dialyzer membrane. This usually
is done by applying a negative pressure to the
dialysate compartment of the dialyzer. This pressure
gradient causes water and dissolved solutes to move
from blood to dialysate, and allows the removal of
several litres of excess fluid during a typical 3 to 5
hour treatment.
Peritoneal dialysis
• In peritoneal dialysis, a sterile solution containing glucose
is run through a tube into the peritoneal cavity, the
abdominal body cavity around the intestine, where the
peritoneal membrane acts as a semipermeable membrane.
• The peritoneal membrane or peritoneum is a layer of tissue
containing blood vessels that lines and surrounds the
peritoneal, or abdominal, cavity and the internal abdominal
organs (stomach, spleen, liver, and intestines).
Peritoneal dialysis
• The dialysate is left there for a period of time to absorb
waste products, and then it is drained out through the tube
and discarded.
• This cycle or "exchange" is normally repeated 4-5 times
during the day, (sometimes more often overnight with an
automated system).
• Ultrafiltration occurs via osmosis; the dialysis solution
used contains a high concentration of glucose, and the
resulting osmotic pressure causes fluid to move from the
blood into the dialysate.
Hemofiltration
• Hemofiltration is a similar treatment to
hemodialysis, but it makes use of a different
principle.
• The blood is pumped through a dialyzer or
"hemofilter" as in dialysis, but no dialysate is used.
• A pressure gradient is applied; as a result, water
moves across the very permeable membrane rapidly,
"dragging" along with it many dissolved substances,
importantly ones with large molecular weights,
which are cleared less well by hemodialysis.
Hemofiltration
• Salts and water lost from the blood during this
process are replaced with a "substitution fluid"
that is infused into the extracorporeal circuit
during the treatment.