Acute Renal Failure

   Kidney gets blood from renal arteries ,filter the blood reabsorb some substances back into the blood an excretes waste as urine.acute renal failure are 3 types.pre renal failure,intrinsic renal failure and post renal failure.In prerenal failure ,the kidneys do not get an adequate blood supply , and thus cannot adequately filter the blood.any circumstances that can cause decreased blood volume (hypovolemia) can lead to decreased renal flow(eg hemorrhage,dehydration)atherosclerotic disease of the renal arteries can also decrease flow to one or both arteries.effective volume depletion (cirrhosis and CHF) also causes pre-renal failure. 

    Intrinsic renal failure include disease of glomeruli and tubules.In both hypovolemia and drug/toxin induced renal failure the onset can be acute. Post renal refers to the ureters,bladder and urethra.blockage here can occur from passage of renal stones into the ureters or a tumor in the genitourinary system(bladder prostrate) or adjacent system such as bowel and ovaries.

  

Presentation

The presentation of acute renal failure depends on the underlying cause and the severity. This may be asymptomatic with oliguria (very low urine output). In acute renal failure there is a retention and accumulation of fluids and nitrogenous excretory waste products in the body. This is usually indicated by elevated blood urea and creatinine. This retention of fluids and waste products determine the signs and symptoms. common symptoms of acute renal failure are as follows.

·         Altered urine output.

o   Usually clients will present with oliguria or anuria. Rarely polyuria can occur due to reduced fluid reabsorption by damaged renal tubes or osmotic effect of accumulated metabolites.

o   A sudden anuria indicate an acute obstruction, acute glomerulonephritis or acute renal artery obstruction.

o   A gradual reduction of urine output may suggest urethral sphincter or bladder opening obstruction usually by benign prostatic hyperplasia (usually elderly men)

·         Nausea and vomiting

·         Confusion, anxiety, restlessness and drowsiness

·         Flank pain (slight pain in the back just below the rib cage)

Hypertension is a typical sign of acute renal failure. This is due to fluid accumulation. A large painless bladder may be palpable usually due to urinary retention. Due to fluid overload by acute fluid retention jugular venous distention and peripheral edema can be noticed. In addition crackles on auscultation indicating pulmonary edema can be heard. Apart from these presence of pallor, rashes, bruising: petechiae, purpura, and nosebleeds indicates inflammatory or vascular disease, emboli or disseminated intravascular coagulation which can be the cause for the acute renal failure.

Investigations

Urine output measurement is really helpful in determining the fluid retention. Usually fluid intake and output charts are maintained for in patients to determine daily retention of fluids which is necessary to assess the degree of renal failure and manage treatments. 

A urinalysis is usually done with a dipstick looking for blood, nitrates, leukocytes and protein in urine in all clients with suspected ARF. Then urine osmolality should be checked. Then certain blood tests are done to detect the cause for the ARF including,

·         FBC and blood film – eosinophilia indicates acute interstitial nephritis, cholesterol embolism or vasculitis. Thrombocytopenia and red cell fragments indicate thrombotic microangiopathy

·         Blood urea and creatinine – these will be elevated due to the renal function failure

·         Coagulation studies

·         CRP- detect infections and inflammation

In addition imaging tests like CT and ultrasound scans can be done to see the kidneys and the bladder. The results can indicate if there is any calculi, obstruction or BPH.

Management (McMillan 2015; Workeneh 2014)

1. IV Furosemide
2. Oxygen therapy
3. Dopamine 1-5 mcg/kg/min- vasodilator and decrease absorption of sodium 
4. IV supplements- 10% calcium gluconate 10 mL + Dextrose 50g + Insulin 5U to 10U
5. Dialysis
6. Prevent administration of nephrotoxic drugs

References

• McMillan, J.I. 2015, 'Acute Kidney Inury', retrieved 29 April 2015, <http://www.merckmanuals.com/professional/genitourinary-disorders/acute-kidney-injury/acute-kidney-injury-aki>
• Workeneh, B.T. 2014, 'Acute kidney inury', retrieved 29 April 2015, <http://emedicine.medscape.com/article/243492-overview#aw2aab6b2b3>