Causes and Manifestations of Acute Kidney Injury

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What does acute renal failure (ARF) or acute kidney injury mean?

To get a better understanding of what’s really happening when you have acute kidney injury, we’ll go into details 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 difference between intrarenal and prerenal failure.

Let’s get into it.

The Basics

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. 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.

Signs and Symptoms

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

What you need to understand is that the kidneys are expected to filter out as much as what you’re consuming or drinking. Therefore, if you drink a gallon of water for a day, it is expected that the kidneys usually are filtering and excreting 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.

  1. 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 it can. So, in this phase, you can expect the following:

  • Low specific gravity
  • Very clear urine
  • The body is getting enough fluid and is properly flushing the toxins
  1. 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. 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.

For the other causes of acute renal failure, mainly the three Hs, drop by

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