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The role of medullary ischemia in acute renal failure
S N Heyman1, S Fuchs, M Brezis
1Department of Medicine, Hadassah University Hospital, Mt. Scopus, Jerusalem, Israel.
Abstract:
The introduction of new techniques for the determination of renal parenchymal oxygenation and intrarenal microcirculation has elucidated some important aspects in the pathophysiology of acute renal failure (ARF). Data accumulated over the last decade with these techniques, together with improved morphologic evaluation of the kidney, indicate that medullary damage may play a pivotal role in various forms of acute and chronic renal hypoxic and toxic insults. The outer medulla functions normally under hypoxic conditions, as a result of limited regional oxygen supply and high oxygen consumption for urinary concentration. Outer medullary oxygenation is critically balanced by mechanisms designed to adjust oxygen demand and supply, and their insufficiency may lead to ARF with hypoxic medullary damage. In this article, we outline our current concept of the physiologic control of medullary oxygenation and review the clinical conditions that predispose to hypoxic medullary damage, including rhabdomyolysis, hypercalcemia, or the exposure to endotoxin, nonsteroidal anti-inflammatory drugs, radiologic contrast agents, cyclosporine, FK506, and amphothericin. We shall indicate a possible role for medullary oxygen insufficiency in clinical conditions known to predispose to ARF, such as preexisting renal disease, diabetes mellitus, hypertension, atherosclerosis, effective volume depletion, urinary obstruction, or aging, and suggest potential strategies to preserve medullary oxygenation and integrity.
Insights
Medullary damage is key in acute renal failure (ARF). Insufficient oxygen supply to the kidney medulla, especially during hypoxia, can cause ARF and requires strategies to preserve medullary oxygenation.
Area of Science:
- Nephrology
- Renal Pathophysiology
- Medical Physiology
Background:
- New techniques reveal insights into renal parenchymal oxygenation and intrarenal microcirculation.
- Medullary damage is increasingly recognized in acute and chronic renal hypoxic and toxic insults.
- The outer medulla's unique physiology makes it vulnerable to hypoxic damage due to high oxygen demand and limited supply.
Purpose of the Study:
- To outline the physiological control of medullary oxygenation.
- To review clinical conditions predisposing to hypoxic medullary damage.
- To suggest strategies for preserving medullary oxygenation and integrity.
Main Methods:
- Review of accumulated data from the last decade using advanced renal oxygenation and microcirculation techniques.
- Integration of morphologic evaluation of the kidney.
- Synthesis of current concepts in renal physiology and pathophysiology.
Main Results:
- Medullary damage plays a pivotal role in various forms of acute and chronic renal insults.
- Outer medullary oxygenation is critically balanced; its insufficiency can lead to acute renal failure (ARF) with hypoxic medullary damage.
- Identified predisposing clinical conditions include rhabdomyolysis, hypercalcemia, endotoxin, NSAIDs, contrast agents, and immunosuppressants.
Conclusions:
- Medullary oxygen insufficiency is implicated in ARF associated with conditions like diabetes, hypertension, and volume depletion.
- Strategies to preserve medullary oxygenation are crucial for preventing ARF.
- Understanding medullary oxygen dynamics is vital for managing renal health.