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Acute Renal Failure causes , diagnosis and treatment

This article is to discuss Acute renal failure regarding definition , causes , diagnosis and treatment .

Definition :
 Sudden onset of deterioration of kidney functions within a period of, days or weeks and results in uremia, it is reversible with treatment of the cause.

acute renal failure

Causes 



i. Pre-Renal   ( correctable, i.e. normal kidney with low perfusion )



  • Hypovolemia 

hemorrhage  , burns , Gastroenteritis (loss of fluids ) .

  •  Shock with normal intravascular volume .
Cardiogenic shock   -  Massive pulmonary embolism .
  • Others
Third spacing e.g. pancreatitis, hepatorenal syndrome.

N.B Drugs that impair renal Auto-regulation e.g ACE inhibitors and NSAIDs increase liability to Pre-Renal   failure .
causes of acute renal failure

ii . Renal causes   (Intrinsic parenchymal renal disease)

• Acute tubular necrosis (ATN).
• Acute interstitial nephritis.
• Acute severe pyelonephritis >>  with papillary necrosis e.g. in D.M.
• Rapidly progressive glomerulonephritis.
• Malignant hypertension.
• Atheroembolic renal disease.

iii . Post-Renal causes    ( Obstruction )

• Bilateral ureteric obstruction.
• Unilateral ureteric obstruction with non functioning or absence of the other kidney.

Clinical Picture 

A. Pre-Renal 
• Manifestations of the cause e.g. marked reduction of blood
pressure with oligurea, decreased skin turger, reduced
jugular venous pressure and dry mucous membranes.

B. Renal 
1- Manifestations of renal failure e.g.
- Oliguria and hypertension.
- Nausea and vomiting.
- Acidotic breathing.
- Weakness and arrhythmia due to hyperkalemia.
- Hypervolemia with development of pulmonary edema.
- Uraemic encephalopathy.
2- Manifestations of the cause :
- Allergic manifestations or rash in acute hypersensitivity
- interstitial nephritis.
- Puffiness in acute G.N.
- Vascular purpura in vasculitis.
- Malignant hypertension.
- Prerenal factors in ATN.

C. Post-renal 

• Patients are usually less severely ill than patients with prerenal or intrinsic renal disease.
• Manifestations of the cause as renal colic, hematuria or anuria (in contrast to oliguria associated with ATN).
• Uremic manifestations may be delayed until BUN > 150 mg/dL and S. Cr > 10 mg/dL.

Investigations 

**  Pre-Renal 
• Increased BUN and creatinine in blood.
• BUN: Cr ratio tends to be high > 20:1.
• Urine Na < 20 mmol/L.
• Urine osmolarity> 500 m.osmol/L.
• Urine analysis showing no cells or cellular casts, but few hyaline or granular casts may be present.
• Sonar is usually normal.

** Renal 
• High urea and creatinine, BUN: Cr ratio is not high.
• Urine sediment is helpful e.g. RBCs, WBCs.
• Eosinophilia and eosinophiluria in hypersensitivity nephritis.
• ANCA and high ESR in vasculitis

Treatment 

Treatment of  Pre-Renal failure 

• Treatment of the cause e.g. blood transfusion, I.V fluid therapy or treatment of heart failure.
• Central venous pressure (CVP) must be monitored to determine the rate of administration of fluids.
• Small dose dopamine may be of value to increase the renal blood flow!?

Treatment of  Renal type of failure 

a -General measures
- Good fluid chart.
- Control blood pressure... 
- NaCH03 for acidosis.
- Low protein diet.
- Glucose/insulin for hyperkalemia.
- Domperidone for vomiting.

b -Treatment of the cause e.g.:
- Pulse steroid therapy in rapidly progressive G.N or vasculitis.
- Stop drugs causing nephrotoxicity.
- Antibiotics for sepsis or pyelonephritis.

c - Dialysis: the indications (see later).

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Tamer Mobarak

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