Pathophysiology
The mechanisms involved in the etiology of AKI are as follows:
endothelial injury from vascular perturbations
direct effect of nephrotoxins
abolishment of renal autoregulation
formation of inflammatory mediators (Figure 2)
Necrosis and apoptosis of tubular cells lead to tubular obstruction, which contributes to the reduction of GFR.18 In addition, elevated intracellular calcium levels from tubular damage cause a series of cellular-level alterations that culminate in increased tubuloglomerular feedback, and thus, diminished GFR.18
Vascular compromise causes increased cytosolic calcium, elevated endothelial injury markers, and production of inflammatory mediators (eg, tumor necrosis factor α, interleukin 18, intercellular adhesion molecule 1), which result in reduced GFR.18
These pathophysiologic mechanisms are perpetuated by a persistent imbalance between the mediators of vasoconstriction and -dilatation that result in intrarenal vasoconstriction and, eventually, ischemia. The vasoconstrictors include angiotensin II, endothelin, thromboxane, and adenosine. The vasodilators include prostaglandin I2 and endothelial-derived nitric oxide.
High levels of vasoconstrictors and low levels of vasodilators cause continued hypoxia and cell damage or cell death. Endothelial-derived nitric oxide is under investigation as a potential therapeutic option to help break this cycle of ischemia.19
Continued research into the pathophysiology of AKI may yield potential targets in the clinical management of this syndrome.