What happens in acute renal failure, exactly?

What is it?

Acute renal failure (ARF), also known as acute kidney injury, is an abrupt loss of kidney function that develops within 7 days. It may be presented as a number of symptoms, including fatigue, loss of appetite, headache, and nausea.

New ARF cases affect about 0.1% of the UK population each year. It is, however, common in hospital patients, affecting 3-7% of those admitted and 25-30% of those in intensive care.

What causes it?

There are very many possible causes of ARF. The most common causes are dehydration, sepsis, and the use of some drugs.Other causes include conditions that reduce blood flow to the kidneys, such as low blood volume or pressure and heart failure. People working in agriculture are at a particularly high risk of ARF. This is because their job exposes them to things like dehydration and heat illness.

What happens during it?

The concentrations of different substances in our body need to be in balance in order for every chemical reaction to happen in the right way. The job of the kidneys is to help with this through controlling the amount of water and ions in our body. They do this by filtrating our blood. The blood flows to the glomerulus, and because the blood pressure there is a lot higher than normal, some of the water gets pushed to the Bowman capsule and out of the blood circulation. After this, the fluid travels a while in a “tube”. Some of the water and ions as well as all important molecules like glucose are taken back to the blood, while some substances are also excreted to the fluid from the blood. When this has been done, the fluid becomes urine and is passed on to the bladder.

It is probably not hard to guess why things that cause low blood pressure can be so damaging to the kidneys. If the pressure gradient between the glomerulus and the Bowman capsule isn’t high enough, enough fluid just doesn’t get through. This isn’t so dangerous in terms of the water itself as the vast majority of it is taken back to the blood anyway. It is, however, dangerous in terms of the ions that are now left in the blood. The signaling of nerve cells, for example, relies on the right concentrations of different ions on different sides of the cell membrane. Potassium is an important ion in this process, and both too high and too low levels of it can severely impact this signaling. Our heart contracts because the signals of nerve cells tell is to. Because of all this, the perhaps biggest danger for someone with ARF is how the wrong ion concentrations impact the heart. This also applies to the ARF cases where kidney function isn’t impaired because of low blood pressure but because of, for example, physical damage to the kidneys.

How can it be treated?

The treatment of ARF focuses on treating the underlying cause. Since there is a vast variety of possible causes, there is also a vast variety of possible treatments. It is fairly common, however, to give some fluids intravenously to get the blood pressure up, since low blood pressure is one of the most common causes. Possible complications such as hyperkalemia can also require management. The overall mortality of ARF is quite high at 20%.

 

 

Sources: https://en.wikipedia.org/wiki/Acute_kidney_injury, https://en.wikipedia.org/wiki/Kidney, http://emedicine.medscape.com/article/243492-overview?pa=BiMU%2FbzITOsKHCmlirHpwNeKLYTwyPTMSQUNfwyvgQ8q1pRtnLn%2BxB6XQU7MZT%2BrLCEJNCrbkqLWYvqLrhntWA%3D%3D#a4

 

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