Acute renal failure pathophysiology

Revision as of 01:18, 7 January 2013 by Aarti Narayan (talk | contribs)
Jump to navigation Jump to search

Acute renal failure Microchapters

Home

Patient Information

Overview

Historical Perspective

Classification

Pathophysiology

Causes

Differentiating Acute renal failure from other Diseases

Epidemiology and Demographics

Risk Factors

Natural History, Complications and Prognosis

Diagnosis

History and Symptoms

Physical Examination

Laboratory Findings

Electrocardiogram

CT

MRI

Ultrasound

Other Imaging Findings

Other Diagnostic Studies

Treatment

Medical Therapy

Surgery

Primary Prevention

Secondary Prevention

Cost-Effectiveness of Therapy

Future or Investigational Therapies

Case Studies

Case #1

Acute renal failure pathophysiology On the Web

Most recent articles

Most cited articles

Review articles

CME Programs

Powerpoint slides

Images

American Roentgen Ray Society Images of Acute renal failure pathophysiology

All Images
X-rays
Echo & Ultrasound
CT Images
MRI

Ongoing Trials at Clinical Trials.gov

US National Guidelines Clearinghouse

NICE Guidance

FDA on Acute renal failure pathophysiology

CDC on Acute renal failure pathophysiology

Acute renal failure pathophysiology in the news

Blogs on Acute renal failure pathophysiology

Directions to Hospitals Treating Acute renal failure

Risk calculators and risk factors for Acute renal failure pathophysiology

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aarti Narayan, M.B.B.S [2]

Pathophysiology

Pre-renal Failure

Intrinsic Renal Failure

  • Severe forms of hypoperfusion cause ischemic injury to the renal parenchymal cells, especially the renal tubular epithelium. The damaged tubular epithelium get sloughed off and takes 1 to 2 weeks to regenerate.
  • In extreme forms, it results in renal cortical necrosis and irreversible renal failure.
  • Intrinsic renal failure most commonly occurs as a complication of cardiovascular surgery, hemorrhage, sepsis or severe trauma
  • Other forms of insults that can cause intrinsic renal failure are nephrotoxic agents or a pre-existing renal disease.
  • Three stages of intrinsic renal failure have been defined:
    • Initiation phase
    • Maintenance phase
    • Recovery phase

Initiation Phase

  • This phase lasts for hours to days. It involves reduction in glomerular filtration rate from decreased renal blood flow. Ischemic injury to the tubular epithelial cells and renal parenchyma causes the tubular cells to slough off and form casts that block the flow of glomerular filtrate down the nephron.
  • The casts in the renal tubule causes fluid to backleak through the tubular epithelium.
  • Ischemic injury affects the medullary segment of the renal tubule and thick segment of loop of Henle as they as relatively ischemic even under normal basal conditions. These segments have the highest oxygen consumption because of higher ATP dependent solute transport.
  • Depletion of ATP causes inhibition of sodium transport, impairment of water balance, calcium accumulation inside the cells, loss of cell to cell adhesion, injury from oxygen free radicals consequently causing cellular swelling and apoptosis.
  • Restoring renal perfusion at this stage prevents further progression of renal injury.

Maintenance Phase

  • This stage is irreversible and the progression of renal injury cannot be stopped.
  • Renal vasoconstriction is thought to contribute to further reduction in urine output secondary to decrease in glomerular filtration rate. Although vasoactive agents contribute to renal injury, the exact mechanisms leading to the vasoconstriction are still to be explored.

Recovery Phase

  • This stage essentially involves regeneration of renal tubular epithelial cells and restoration of urine output.
  • This phase may be sometimes complicated by a diuretic phase. This diuretic phase occurs to wash out the retained salt and water from the body.

Post-renal Acute Renal Failure

  • Urinary tract obstruction is responsible for less than 5% of cases of acute renal failure.
  • As one kidney can compensate for the other poorly functioning kidney, a bilateral urinary tract obstruction is required for it to cause the kidney's to fail. Hence, conditions like bladder neck obstruction, bilateral ureteric obstruction or unilateral ureteric obstruction with other diseased kidney can cause renal failure.
  • Initial stages may involve a modest increase in renal blood flow, however vasoconstriction superimposes and eventually causes decrease in glomerular filtration rate.

References

Template:WH Template:WS