الفهرس 
Background on Anatomy of the KidneyOnly 14 pages are availabe for public view
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Abstract
AKI is a common clinical problem in critically ill patients that is associated with increased morbidity and mortality. Even a modest impairment in renal function is an independent risk factor for mortality, but the onset of AKI is often not recognized.
Acute kidney injury (AKI) is commonly and increasingly encountered in patients with critical illness. In the past, epidemiologic studies have consistently found that oliguria further increases the risk of death from AKI. Compared with patients outside the intensive care unit (ICU), critically ill patients are more likely to have volume overload as a result of impaired solute and water excretion. Recently, broad changes have occured in ICU practice, such as early goal – directed therapy in sepsis, which may further compound volume overload in ICU patients with oliguric AKI.
Clinical feature and physical examination may aid in providing clues to the cause of AKI. Assessment of urine output is required as patients of AKI are usually oliguric (urine output less than 0.3 ml/Kg/h for at least 24 hours). Anuria (urine volume < 100 ml or complete absence of urine) is rare and usually indicates acute urinary tract obstruction or vascular occlusion, but may complicate severe cases of prerenal or intrinsic renal oliguria. whereas patients with partial urinary tract obstruction can present with polyuria due to impairment of urine concentrating mechanisms.
Intensive care unit patients with oliguric AKI presents a dilemma with limited therapeutic options. These would include optimization of systemic hemodynamics, added fluid therapy, administration of loop diuretics, or finally, the instillation of renal replacement therapy.
Extracorporeal blood purification techniques can be applied to prevent these complications and improve homeostasis. Various techniques of renal replacement therapy include continuous venovenous hemofiltration, intermittent hemodialysis, and peritoneal dialysis, each with its technical variations but with a common fundamental principle of removing unwanted solutes and water through a semipermeable membrane. The membranes used are either biologic (peritoneum) or artificial (hemodialysis or hemofiltration membranes) and have characteristic advantages and disadvantages.
For many years, intermittent hemodialysis (IHD) was the only treatment option for patients with AKI in the ICU. In numerous countries, it is still the most frequently used modality. Continuous venovenous hemofiltration (CVVH) was subsequently proposed as an alternative to IHD in the critically ill, because it was better tolerated by hypotensive patients, and the continuous regulation of fluid and nutritional support and avoided cycles of volume overload and depletion.
Other new approaches to intermittent therapy (so-called hybrid techniques), such as slow extended dialysis, slow low-efficiency daily dialysis, and intermittent extended hemofiltraton, are emerging. These techniques seek to adapt intermittent hemodialysis to the clinical circumstances and increase its tolerance and its clearances. Such hybrid approaches represent a welcome improvement in dialysis support and a clear recognition that acute renal failure patients should not receive the dialysis offered to patients with end-stage renal failure.
Uremia and the need for renal replacement therapy (RRT) among critically ill patients frequently result in complications, such as bleeding, inadequate fluid removal or intravascular volume depletion, and enhanced susceptibility to infections, which can further aggravate the underlying condition. Therefore, the management of AKI in the ICU represents significant ongoing challenge to nephrologists and intensivists.