Rhabdomyolysis and Acute Kidney Injury
What is Acute Kidney Injury (AKI)?
According to Medscape, AKI is an abrupt or rapid decline in renal filtration function. The term acute kidney injury (AKI) has recently replaced acute renal failure (ARF). Some of the references on this website refer to ARF, but we will mainly refer to the overarching AKI. There are currently two main classification systems for AKI, the Acute Dialysis Quality Initiative's RIFLE and the Acute Kidney Injury Network (AKIN) criteria [20]. Below are some examples of classifications of AKI:
Though there are differences between the classifications that are available, there is a trend in classification due to serum creatinine levels.
How Does Rhabdomyolysis cause AKI?
Follow the myoglobin! Myoglobin is a hemoprotein just like hemoglobin. Myoglobin contains one heme group (and, thus can only hold one O2) and is found in striated muscle cells as an oxygen repository; whereas, hemoglobin contains four heme groups and is found in the blood stream as an oxygen delivery system. When the muscle cells die in rhabdomyolysis, all of their contents (including the myoglobin) are spilled into the body cavity where they can enter the bloodstream. Below is one method of how the myoglobin enters the kidney and begins to injure it:
 AKI: RIFLE ClassificationTable from [1] |  AKI: AKIN ClassificationTable from [22] |  AKI ClassificationTable from [23] |
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This figure was made from information given in Daher Ede et al. [3].
This pathway shows the entrance of the myoglobin into the kidney and one way in which it can cause damage. It is important to note that there are other mechanisms by which myoglobin can cause kidney injury. These are expressed in the following figure:
This diagram was made from information found in [7-15]. It shows the mechanisms by which myoglobin, when released from the muscle cells, can cause damage to the kidney. Both dehydration and pH amplify the effects of myoglobin. NO stands for nitric oxide. NO3- stands for Nitrate. ATP stands for adenosine triphosphate. GFR stands for glomerular filtration rate. AKI stands for acute kidney injury. ARF stands for acute renal failure. Both AKI and ARF have been used here because of the variation of usage. More information on endothelin receptors, vasodilation, vasoconstriction, ischemia, hypocalcemia, Tamm-Horsfall protein, and pigmented casts can be found on the definitions page.
Extra Resources:
The following videos provide more in-depth information regarding acute renal failure.