Section VII: Disorders of the Kidney and Urinary Tract
Which of the following is a potential etiology for ischemic acute renal failure?
A. Apoptosis and necrosis of tubular cells
B. Decreased glomerular vasodilation in response to nitric oxide
C. Increased glomerular vasoconstriction in response to elevated endothelin levels
D. Increased leukocyte adhesion within the glomerulus
The answer is E. (Chap. 334) Ischemic acute renal failure has many potential etiologies. Microvascular disorders include increased vasoconstriction from endothelin and other mediators, decreased nitric oxide, prostaglandin- or bradykinin-mediated vasodilation, increased endothelial and vascular smooth muscle cell damage, and increased leukocyte adhesion. Tubular factors include cytoskeletal breakdown, loss of polarity, apoptosis and necrosis, desquamation of viable and necrotic cells, tubular obstruction, and backleak. Inflammatory and vasoactive mediators may affect both tubular and microvascular pathophysiologic mechanisms. (See Figure VII-1.)
FIGURE VII-1 PGE2, prostaglandin E2. From JV Bonventre, JM Weinberg: J Am Soc Nephrol 14:2199, 2003.
All of the following are risk factors for postoperative acute kidney injury EXCEPT:
A. Cardiac surgery with cardiopulmonary bypass
D. Intraoperative hypotension
E. Significant operative blood loss
The answer is C. (Chap. 334) Ischemia-associated acute kidney injury (AKI) is a serious complication in the postoperative period, especially after major operations involving significant blood loss and intraoperative hypotension. The procedures most commonly associated with AKI are cardiac surgery with cardiopulmonary bypass (particularly for combined valve and bypass procedures), vascular procedures with aortic cross-clamping, and intraperitoneal procedures. Severe AKI requiring dialysis occurs in approximately 1% of cardiac and vascular surgery procedures. The risk of severe AKI has been less well studied for major intraperitoneal procedures but appears to be of comparable magnitude. Common risk factors for postoperative AKI include underlying chronic kidney disease, older age, diabetes mellitus, congestive heart failure, and emergency procedures. Gender is not a known risk factor independent of the other factors listed above. The use of nephrotoxic agents including iodinated contrast for cardiac imaging prior to surgery may increase the risk of AKI.
A 57-year-old man with a history of diabetes mellitus and chronic kidney disease with a baseline creatinine of 1.8 mg/dL underwent cardiac catheterization for acute myocardial infarction. He is subsequently diagnosed with acute kidney injury related to iodinated contrast. All ...