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Acute Tubular necrosis (ATN) causes , clinical picture , investigations

This article discusses the case of Acute Tubular necrosis ATN  regarding its definition , aetiology and diagnosis ( clinical picture and investigations ) .

Definition :

acute renal failure with mild to severe damage or necrosis of tubule cells, usually resulting from nephrotoxicity, ischemia after major surgery, trauma (crush syndrome ), severe hypovolaemia, sepsis, or burns.
acute tubular necrosis

Causes of Acute Tubular necrosis

1- Ischemic causes (Prerenal factors if not corrected rapidly).
discussed here ...... 
2- Toxic causes :

A.  Endogenous
 - Hemoglobin (Hemolytic anemia).
 - Myoglobin (Rhabdomyolysis).
 - Bilirubin Nephropathy in obstructive jaundice.

B. Exogenous:
- The dye of I.V.P, CT scan or angiography (contrast nephropathy).
- Drugs: aminoglycosides.
- Toxins of gram - ve septicemia.

How to reach diagnosis in a case of acute tubular necrosis ?

Clinical Picture and Investigations  (3 stages)

1.  Oliguric phase: (2-4 wks)

C/P:
(do not forget manifestation of the cause).
1- Urine volume :  - Oliguria < 400 cc/D.
                            -  Anuria  < 50 or < 100 cdD.
2- GIT   :  Vomiting, nausea.

3- CVS : -  Hypertension.
               -  Hypervolemia -->  pulmonary edema.

4- Metabolic errors :
- High K+   -->    weakness, arrhythmia.
- Acidosis    -->    acidotic breathing.

5- Drowsiness, fits and coma.

Investigations 
1. Creatinine , urea .  :  High
2.  Low pH -, K  high .
3. Hypocalcemia and HyperPhosphatemia  or may be normal.
4. low Hb or may be normal.
5. Urine analysis : Granular casts or tubular casts.
6. Sonar almost normal kidney.

2. Polyuric phase (for 3 - 4 days )
Causes :
1- Relief of tubular obstruction.
2- Regeneration of kidney tubule but they are still unable to concentrate urine.
3- Urea retention (osmotic diuresis)

C/P :

• Improvement of general condition.
• Low Na, High  K due to diuresis.
• Urine output 3-5 L /d.

3. Post diuretic phase:
• Clinical improvement.
• Kidney functions become normal.
• Urine output becomes normal volume, concentrated.
• If the oliguria is not reversible, the diagnosis is cortical necrosis and not ATN and CRF will develop.
• No need for renal biopsy to diagnose ATN.
Treatment of Acute Tubular necrosis : see Here ...
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Tamer Mobarak

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