Acute Tubular Necrosis

Acute tubular necrosis (ATN) is the most common form of intrinsic acute kidney injury, caused by injury to the renal tubular epithelium from ischemia or nephrotoxins. Despite its historical name, the dominant lesion is often sublethal tubular cell injury rather than frank necrosis, and the term 'acute tubular injury' is increasingly preferred.

Definition

Acute tubular necrosis is intrinsic acute kidney injury resulting from injury to the renal tubular epithelial cells, most often due to ischemia or nephrotoxic exposure, leading to impaired tubular function and a fall in glomerular filtration.

Scope

The entry describes the pathophysiology, principal causes (ischemic and nephrotoxic), and typical course of ATN as the leading intrinsic cause of AKI in hospitalized and critically ill patients. It is a reference on mechanism and natural history and does not prescribe individual management.

Core questions

• What injures the tubular epithelium in ATN, and how does that reduce glomerular filtration?
• How do ischemic and nephrotoxic ATN differ?
• Why is 'acute tubular injury' often preferred to 'acute tubular necrosis'?
• What is the expected clinical course and potential for recovery?

Key concepts

• Tubular epithelial cell injury
• Ischemic ATN
• Nephrotoxic ATN
• Tubular cell sloughing and cast formation
• Tubuloglomerular feedback
• Maintenance and recovery phases
• Muddy brown granular casts

Mechanisms

In ischemic ATN, reduced renal blood flow depletes tubular cells of energy, causing loss of cell polarity, cytoskeletal disruption, detachment of viable and non-viable cells into the lumen, and obstructing casts; back-leak of filtrate and tubuloglomerular feedback further lower glomerular filtration. Nephrotoxic ATN involves direct cellular toxicity from agents that concentrate in or are handled by the tubules. Modern descriptions, summarized by Kellum and Prowle and by Ronco and colleagues, emphasize that much of the epithelial injury is sublethal and potentially reversible, with inflammation and microvascular changes contributing, so the structural 'necrosis' implied by the classic name is often limited.

Clinical relevance

ATN accounts for a large share of intrinsic AKI in the hospital and intensive care unit, and understanding its mechanisms underlies the recognition of ischemic and nephrotoxic insults and the expectation of a maintenance phase followed by potential recovery. This entry conveys the concepts and is not a basis for individual diagnosis or treatment.

Epidemiology

ATN is the predominant cause of intrinsic AKI among hospitalized and critically ill patients, frequently arising in the setting of sepsis, major surgery, hypotension, and nephrotoxin exposure; severity and the presence of multiorgan failure influence the likelihood and completeness of renal recovery.

Evidence & guidelines

The 2012 KDIGO guideline frames the evaluation and supportive management of AKI, including ischemic and nephrotoxic injury. The VA/NIH ATN Study (Palevsky and colleagues, 2008) is a landmark randomized trial in critically ill AKI that found no benefit of more-intensive over less-intensive renal replacement therapy, informing how kidney support is delivered in this setting. Reviews by Ronco and by Kellum and Prowle synthesize current pathophysiology.

History

The clinicopathologic concept of acute tubular necrosis emerged from observations of crush injury and shock in the early-to-mid twentieth century, when tubular damage was linked to acute renal failure. Subsequent work refined the understanding from purely structural necrosis toward a spectrum of sublethal tubular injury, inflammation, and microvascular dysfunction, motivating the alternative term 'acute tubular injury.'

Debates

Is 'necrosis' an accurate descriptor?

Because biopsy and experimental studies often show sublethal injury rather than widespread cell death, many authors argue 'acute tubular injury' better reflects the histology, though 'acute tubular necrosis' remains in common use.

Key figures

• John A. Kellum
• Claudio Ronco
• Rinaldo Bellomo
• Paul M. Palevsky

Seminal works

• ronco-2019
• palevsky-2008

Frequently asked questions

What are the two main causes of acute tubular necrosis?

Ischemia (reduced renal perfusion, as in shock or sepsis) and nephrotoxins are the two principal causes of injury to the tubular epithelium in ATN.

Can the kidney recover after acute tubular necrosis?

Because tubular epithelial cells can regenerate, kidney function often recovers after the injurious insult is removed, although recovery may be incomplete, particularly with severe or prolonged injury.