Acute renal failure

Acute renal failure: Complete Overview

Acute renal failure is an acute and reversible deterioration of renal function which develops over a period of days and weeks. Acute renal failure is also known as acute kidney failure or acute kidney injury. Acute renal failure symptoms begin to appear when your kidney suddenly stops performing its function within the days or weeks. Kidneys become unable to filter the waste products from your body.

Thus, dangerous waste products begin to accumulate in your body and cause Chemical toxicity inside your body. It is a reversible failure, you can correct it properly if diagnosed early. If it is neglected, it can be fatal. This acute kidney failure is most common in those patients who are already hospitalized particularly patients of intensive care units.

Etiology of Acute Renal Failure

Causes of Acute renal failure can be divided into three major categories, depending on the site of the kidney involved

1- Pre-renal acute Renal failure

Due to decreased cardiac output in cardiac failure, volume depletion, decrease capillary refilling and vasodilation are the pre-renal causes due to which kidneys are inadequately perfused and have reduced GFR.

2- Intrinsic Renal failure

Vasculitis or microangiopathic hemolytic states, injury of renal tubular cells, acute tubular necrosis due to toxins or ischemia, infections, drugs, and vascular causes are the main causes of renal failure.

3- Post-renal failure

In this type, acute Renal failure is basically due to obstruction of the entire urinary tract at any point ( from kidney uptown urethra).

Pre-Renal Acute Renal Failure

About 70% of acute Renal failure is caused by pre-renal failure. It is also known as pre-renal azotemia. It is due to hypoperfusion of kidneys caused by volume depletion or decreases vascular ability. As it is reversible, it can be easily reversed by the restoration of renal blood flow. If this hypoperfusion persists, it can undergo ischemia causing intrinsic renal failure. There is no renal parenchymal damage in pre-renal causes.

Pre-renal Causes

It includes:

  • Volume deficit
  • Cardiogenic shock
  • Chronic liver disease
  • Decrease systemic vascular resistance
  • Intravascular hemolysis

Signs & Symptoms

The patient has following acute Renal failure symptoms due to pre-renal azotemia presents with the complaint of

  • Decrease urine output
  • Irregular heartbeat
  • Weakness, fatigue
  • Fluid retention and swelling around ankles or feet
  • Shortness of Breath


Pre-renal azotemia can be diagnosed with

  • Taking Proper history
  • Clinical findings
  • Increase plasma creatinine and urea level
  • Urine sodium < 20 meq/L
  • Urine osmolarity > 500 mosm/kg
  • Serum BUN : creatinine ratio > 20:1

Treatment Of Pre-renal azotemia

It can be restored by replacing the blood, plasma, or normal Saline and start antibiotics if the cause is hypovolemia or sepsis. Ask the patient to avoid nephrotoxic drugs. Maintain serum electrolytes especially sodium and potassium.

Intrinsic Renal Failure

It is the most common type of renal failure which is characterized by renal tubular necrosis which results in poor absorption and filtration mechanism.
Acute renal failure due to intrinsic renal failure can be caused by

Acute tubular necrosis

Renal Tubular injury due to

  • Ischemia
  • Hypotension
  • Antibiotics such as aminoglycosides
  • Certain chemicals
  • Heavy metals like mercury


It may be

Acute glomerulonephritis

Acute interstitial nephritis

It is usually drug-induced.

Vascular disease

  • Polyarteritis nodosa
  • Atheroma kidney

Signs & Symptoms

Patients with intrinsic renal failure present with the complaint of
Oliguria i.e increase urine output (unlike the pre-renal Acute renal failure symptoms)
Weakness, fatigue, Confusion, Fluid retention and swelling of ankles


Intrinsic Renal failure can be diagnosed by proper history, physical examination, clinical findings, and level of creatinine, urine, and sodium in blood and plasma. In renal azotemia,
Urine sodium > 20 meq/L

  • Urine osmolarity < 500 mosm/kg
  • Serum BUN : creatinine ratio < 20:1

Post-Renal Failure

In this type of failure, obstruction of the urinary tract is present at any site of its course.

Signs & Symptoms

Patients present with the following acute Renal failure symptoms due to post-renal

  • azotemia
  • hematuria,
  • loin pain,
  • difficulty in micturition,
  • nocturia or renal colic.

Like Pre-renal azotemia, patients of such type also present with decreased urine output.


Proper history

The Clinical features

Obstruction of the urinary tract can be visualized by cystoscopy or pyelography ( retrograde or antegrade).


Obstruction of the urinary tract should be removed by medication, surgery or radiotherapy.

Investigation Needed For Acute Renal Failure Symptoms/ Acute Kidney Failure

Following investigations are necessary to find out the acute kidney failure and its type. These are

  • Urine output measurement

Measurement of 24-hour urine output must be recorded to find out the renal failure.

  • BUN (blood urea nitrogen is the measurement of nitrogen level in blood)
  • Urinalysis ( a sample of urine)
  • CBC (complete blood count)
  • RFTs (renal functions test)
  • CT scan of the kidney
  • Kidney ultrasound

Complications of Acute Kidney Injury

Acute kidney failure can lead to many complications if left undiagnosed or untreated. These can be:

  • Infections
  • Hyponatremia
  • Hyperkalemia
  • Fluid overload
  • Anemia
  • Malnutrition due to poor absorption
  • Bleeding problems
  • Cardiac arrhythmias
  • Gastrointestinal disorders

How These Complications Of Acute Kidney Failure Can Be Managed?

Management is different for different complications. The common complications and their management is discussed below

1- Infections

These patients of renal failure are at high risk of getting infections. Your doctor first identifies the cause and source of infection, then ANTIBIOTICS are given according to involved organism.

2- Hyponatremia

It is due to excessive intravascular fluids in case of an inappropriate amount of intravascular fluids. It can be restored by Restricting the oral fluid intake and restrictions of hypnotic solutions.

3- Hyperkalemia

Mild hyperkalemia

It can be corrected by restrictions of dietary potassium intake and by giving the potassium binders.

severe hyperkalemia

Severe hyperkalemia is a medical emergency. It can be treated with calcium gluconate, 1-2 ampules of sodium bicarbonate, beta 2- agonists, kayexalate, and glucose and insulin.

4- Malnutrition

It is the most dangerous complication of acute kidney failure. Therefore, it is necessary to provide basic calories in the form of carbohydrates. Proteins should be given in a small amount.

5- Bleeding Problems

Some patients may have anemia due to hemolysis, hemodilution, or reduced erythropoiesis. While some may suffer from bleeding disorders due to clotting factors abnormalities or platelets dysfunction. But still, all are reversible. These disorders can be managed by blood transfusion, estrogen therapy, cryoprecipitates infusion, and dialysis.

HP Thoughts: Internal disorders have an impact on your overall bodily (and mental) functions. One life-threatening illness is this one — Uremic Encephalopathy.

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