Phases of Acute Kidney Injury: Causes and Manifestations

What does acute renal failure (ARF) or acute kidney injury (AKI) mean? To better understand what’s really happening through phases of acute kidney injury, we’ll go into detail about its causes and manifestations. 

We’ll go into the three stages of acute kidney injury, its manifestations, and how to fix them with the acronym, H-D-T-V. We’ll also discuss the three causes of acute renal failure and how to tell the difference between intrarenal and prerenal failure.

Let’s get into it.

Acute Renal Failure & AKI Meaning

The kidneys filter three things – hydrogen ions, blood urea nitrogen, and creatinine. These elements are filtered inside the nephrons, and inside the nephrons are glomeruli. 

The normal glomeruli filtration rate (GFR) is between 85 – 105 ml of blood per minute. 

If this filtration rate drops to 65 ml/min, it means that the kidneys are in trouble, and a diagnosis of acute kidney failure ensues.

Learn more about nursing management and interventions for acute renal failure.

Phases of Acute Kidney Injury (AKI)

There are three main manifestations of acute kidney injury – oliguric, diuretic, and recovery. What happens during these phases?

1. Oliguric Phase 

In this phase, the kidneys are “insulted” by nephrotoxic medications or components, namely:

• Vancomycin
• Gentamicin
• IV contrast

The oliguric phase can be characterized by:

• No urine output
• If there is urine, it would be very little and is very brown
• High urine-specific gravity

You must understand that the kidneys are expected to filter out as much as what you consume or drink. Therefore, if you drink a gallon of water for a day, it’s expected that the kidneys filter and excrete at least a gallon of water within that day. 

Which is why, clients who are drinking a gallon of water and are only peeing 100 ml/day, or taking in 135 ounces but excreting only three ounces are already suffering from oliguria.

Oliguria vs. Anuria

Oliguria occurs when someone has less than 400mL or 17oz of urine output per day. On the other hand, Anuria is when you have no urine output at all.

Oliguria is usually a sign of severe dehydration, and can be accompanied by other symptoms like confusion or lethargy. It could also be a sign of kidney disease, or even cancer.

Anuria can be a sign of kidney failure or urinary tract obstruction. But it can also be caused by certain medications like blood pressure medicine or antidepressants.

2. Diuretic Phase

The second phase of acute kidney injury, known as the diuretic phase, is when the kidneys are compensating. When injured, the body will try to compensate by getting rid of as much fluid as possible. 

So, in this phase, you can expect the following:

3. Recovery Phase

The last phase of acute kidney injury is referred to as the recovery phase which technically means that the kidneys are adequately producing urine and recovering from the trauma. 

However, this does not mean that the kidneys are 100% in perfect condition. The recovery phase mainly implies that the kidneys are properly compensating, and the glomerular filtration rate is around 30 ml/hour.

Other Causes of Acute Kidney Injury

Other than vancomycin, gentamicin, and IV contrast, there are also diabetic drugs like metformin that can cause acute renal failure. These drugs are very toxic to the kidneys due to their half-life. In addition, it takes quite some time for these drugs to be excreted by the kidneys.

Therefore, if your client is taking metformin, it should be discontinued two days before or after the IV contrast so as not to increase insult to the kidneys and prevent acute kidney injury.

Intrarenal vs. Prerenal Failure

Intrarenal failure means that your kidney is actually failing as a result of an injury. As a result, the kidneys aren’t able to filter out waste products from your blood.
Prerenal failure, on the other hand, happens when there’s not enough blood flow to your kidneys, which causes them to fail at filtering out waste products from the body’s blood.

Need More Renal Resources?

There’s plenty to learn about the renal system – for your classes and beyond into your career. 

Along with this overview, you’ll need supplemental resources to retain information better. SimpleNursing offers study guides, quiz banks, videos with rationales, and much more.

Access all the organ learning resources with a free trial today.