Transcript renal failure and hemodialysis

RENAL FAILURE
DEPARTMENT OF PHYSIOLOGY
DR.TAYYABA AZHAR
ACUTE RENAL FAILURE
DEFINETION:
• Acute renal failure defined as abrupt decline
in renal function with ↑ creatinine and ↑
BUN over period of several days.
Classification
• The causes of acute renal failure can be
divided into three main categories:
• 1. Acute renal failure resulting from decreased
blood supply to the kidneys; this condition is
often referred to as prerenal acute renal
failure
• Reflects the fact that the abnormality occurs
in a system before the kidneys.
• This can be a consequence of heart failure
with reduced cardiacoutput and low blood
pressure or conditions associated with
diminished blood volume and low blood
pressure, such as severe hemorrhage.
• Some Causes of Prerenal Acute Renal Failure
Intravascular volume depletion
• Hemorrhage (trauma, surgery, postpartum, gastrointestinal)
• Diarrhea or vomiting
• Burns
Cardiac failure
• Myocardial infarction
• Valvular damage
Peripheral vasodilation and resultant hypotension
• Anaphylactic shock
• Anesthesia
• Sepsis, severe infections
Primary renal hemodynamic abnormalities
• Renal artery stenosis, embolism, or thrombosis of renal artery
• or vein
• 2. Intrarenal acute renal failure
Resulting from abnormalities within the kidney
itself, including those that affect the blood
vessels, glomeruli, or tubules.
• 3. Postrenal acute renal failure
Resulting from obstruction of the urinary
collecting system
Some Causes of Intrarenal Acute Renal
Failure
Small vessel and/or glomerular injury
• Vasculitis (polyarteritis nodosa)
• Cholesterol emboli
• Malignant hypertension
• Acute glomerulonephritis
Tubular epithelial injury (tubular necrosis)
• Acute tubular necrosis due to ischemia
• Acute tubular necrosis due to toxins (heavy metals, ethylene
• glycol, insecticides, poison mushrooms, carbon tetrachloride)
Renal interstitial injury
• Acute pyelonephritis
• Acute allergic interstitial nephritis
Physiologic Effects of Acute
Renal Failure
• A major physiologic effect of acute renal
failure is retention in the blood and
extracellular fluid of water, waste products of
metabolism, and electrolytes. This can lead to
water and salt overload, which in turn can
lead to edema and hypertension.
• Increases in plasma potassium concentration
(hyperkalemia) to more than about 8 mEq/L
(only twice normal) can be fatal.
• Patients with acute renal failure develop
metabolic acidosis, which in itself can be
lethal or can aggravate the hyperkalemia.
• In the most severe cases of acute renal failure,
complete anuria occurs.
• The patient will die in 8 to 14 days unless
kidney function is restored or unless an
artificial kidney is used to rid the body of the
excessive retained water, electrolytes, and
waste product of metabolism.
Chronic Renal Failure:
An Irreversible Decrease
in the Number of Functional
Nephrons
• Chronic renal failure results from progressive
and irreversible loss of large numbers of
functioning nephrons.
• Some Causes of Chronic Renal Failure
Metabolic disorders
• Diabetes mellitus
• Obesity
• Amyloidosis
Hypertension
Renal vascular disorders
• Atherosclerosis
• Nephrosclerosis-hypertension
Immunologic disorders
• Glomerulonephritis
• Polyarteritis nodosa
• Lupus erythematosus
Infections
• Pyelonephritis
• Tuberculosis
Primary tubular disorders
• Nephrotoxins (analgesics, heavy metals)
• Urinary tract obstruction
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Renal calculi
Hypertrophy of prostate
Urethral constriction
• Congenital disorders
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Polycystic disease
Congenital absence of kidney tissue (renal hypoplasia)
Glomerular
sclerosis
Glomerular
pressure
and/or
filtration
Arterial
pressure
Vicious Circle of Chronic Renal
Failure Leading to End-Stage
Renal Disease
• Removal of large portions of the kidney
initially causes adaptive changes in the
remaining nephrons that lead to increased
blood flow, increased GFR, and increased
urine output in the surviving nephrons.
• The exact mechanisms responsible for these
changes are not well understood but involve
hypertrophy (growth of the various structures
of the surviving nephrons)
• Most common causes of endstage renal
disease.
In the early 1980 glomerulonephritis in all its
various forms was believed to be the most
common initiating cause of end-stage renal
disease. In recent years, diabetes mellitus and
hypertension have become recognized as the
leading cause of end-stage renal disease
Most Common Causes of End-Stage Renal Disease
(ESRD)
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Cause Percentage of Total ESRD Patients
Diabetes mellitus
44
Hypertension
26
Glomerulonephritis
8
Polycystic kidney disease
2
Other/unknown
20
Treatment of Renal Failure
by Dialysis with an
Artificial Kidney
• Severe loss of kidney function, either acutely
or chronically, is a threat to life and requires
removal of toxic waste products an restoration
of body fluid volume and composition toward
normal. This can be accomplished by dialysis
with an artificial kidney.
• A better treatment for permanent loss of
kidney function is to restore functional kidney
tissue by means of a kidney transplant.
Basic Principles of Dialysis.
• The basic principle of the artificial kidney is to
pass blood through minute blood channels
bounded by a thin membrane.
• On the other side of the membrane is a
dialyzing fluid into which unwanted
substances in the blood pass by diffusion.
• there is no phosphate, urea, urate, sulfate,
or creatinine in the dialyzing fluid; however,
these are present in high concentrations in the
uremic blood.
• Therefore, when a uremic patient is dialyzed,
these substances are lost in large quantities
into the dialyzing fluid.
• Most artificial kidneys can clear urea from the
plasma at a rate of 100 to 225 ml/min, which
shows that at least for the excretion of urea,
the artificial kidney can function about twice
as rapidly as two normal kidneys together,
whose urea clearance is only 70 ml/min.
• The artificial kidney is used for only 4 to 6
hours per day,three times a week.
• The artificial kidney cannot replace some of
the other functions of the kidneys, such as
secretion of erythropoietin, which is necessary
for red blood cell production.