Which of the following is NOT a cause of intra-renal AKI?

Intra-renal acute kidney injury (AKI) occurs when there is damage to the kidney's structures, often due to conditions that directly affect the renal parenchyma. Acute tubular necrosis, nephrotoxic agents, and acute interstitial nephritis all fall under this category as they directly damage the kidney tissues.

Acute tubular necrosis is a common cause of intra-renal AKI, primarily resulting from ischemia or nephrotoxicity. Nephrotoxic agents, such as certain medications or toxins, can lead to cellular damage within the renal tubules, contributing to intra-renal injury. Acute interstitial nephritis is characterized by inflammation of the kidney's interstitial tissue and can result from allergic reactions to drugs or infections, also classifying it as an intra-renal cause.

In contrast, renal artery obstruction pertains to issues that originate from the renal blood supply, affecting the kidneys indirectly through decreased perfusion. Such conditions are typically considered pre-renal causes of AKI, as they result from reduced blood flow to the kidneys rather than damage to the kidney tissue itself. Therefore, this option accurately reflects a cause that does not belong to the intra-renal category.