Idea Transcript
Acute kidney injury Acute kidney injury (AKI), previously called acute renal failure (ARF),[1][2] is an abrupt loss of kidney function that develops within 7 days.[3] Its causes are numerous. Generally it occurs because of damage to the kidney tissue caused by decreased kidney blood flow (kidney ischemia) from any cause (e.g., low
Acute kidney injury Synonyms
Acute renal failure (ARF)
blood pressure), exposure to substances harmful to the kidney, an inflammatory process in the kidney, or an obstruction of the urinary tract that impedes the flow of urine. AKI is diagnosed on the basis of characteristic laboratory findings, such as elevated blood urea nitrogen and creatinine, or inability of the kidneys to produce sufficient amounts of urine. AKI may lead to a number of complications, including metabolic acidosis, high potassium levels, uremia, changes in body fluid balance, and effects on other organ systems, including death. People who have experienced AKI may have an increased risk of chronic kidney disease in the future. Management includes treatment of the underlying cause and supportive care, such as renal replacement therapy.
Contents Pathologic kidney specimen showing marked pallor of the cortex, contrasting to the darker areas of surviving medullary tissue. The patient died with acute kidney injury.
Signs and symptoms Causes Classification Prerenal
Specialty
Intrinsic
Nephrology
Postrenal Diagnosis Definition Staging Evaluation Treatment Prerenal Intrinsic Post renal Renal replacement therapy Complications Prognosis Mortality Kidney function Epidemiology History See also References External links
Signs and symptoms The clinical picture is often dominated by the underlying cause.The symptoms of acute kidney injury result from the various disturbances of kidney function that are associated with the disease. Accumulation of urea and other nitrogen-containing substances in the bloodstream lead to a number of symptoms, such as fatigue, loss of appetite, headache, nausea and vomiting.[4] Marked increases in the potassium level can lead to abnormal heart rhythms, which can be severe and life-threatening.[5] Fluid balance is frequently affected, though blood pressure can be high, low or normal.[6] Pain in the flanks may be encountered in some conditions (such as clotting of the kidneys' blood vessels or inflammation of the kidney); this is the result of stretching of the fibrous tissue capsule surrounding the kidney.[7] If the kidney injury is the result of dehydration, there may be thirst as well as evidence of fluid depletion on physical examination.[7] Physical examination may also provide other clues as to the underlying cause of the kidney problem, such as a rash in interstitial nephritis (or vasculitis) and a palpable bladder in obstructive nephropathy.[7]
Causes Classification Acute kidney injury is diagnosed on the basis of clinical history and laboratory data. A diagnosis is made when there is a rapid reduction in kidney function, as measured by serum creatinine, or based on a rapid reduction in urine output, termed oliguria (less than 400 mLs of urine per 24 hours). AKI can be caused by systemic disease (such as a manifestation of an autoimmune disease, e.g. lupus nephritis), crush injury, contrast agents, some antibiotics, and more. AKI often Classic laboratory findings in AKI
occurs due to multiple processes. The most common cause is dehydration and sepsis combined with nephrotoxic drugs, especially following surgery or contrast agents.
Type
UOsm
UNa
FeNa
BUN/Cr
Prerenal
>500
2%
4%
>15
The causes of acute kidney injury are commonly categorized into prerenal, intrinsic, and postrenal.
Prerenal Prerenal causes of AKI ("pre-renal azotemia") are those that decrease effective blood flow to the kidney and cause a decrease in the glomerular filtration rate (GFR). Both kidneys need to be affected as one kidney is still more than adequate for normal kidney function. Notable causes of prerenal AKI include low blood volume (e.g., dehydration), low blood
pressure, heart failure (leading to cardiorenal syndrome), liver cirrhosis and local changes to the blood vessels supplying the kidney. The latter include renal artery stenosis, or the narrowing of the renal artery which supplies the kidney with blood, and renal vein thrombosis, which is the formation of a blood clot in the renal vein that drains blood from the kidney.
Intrinsic Intrinsic AKI refers to disease processes which directly damage the kidney itself. Intrinsic AKI can be due to one or more of the kidney's structures including the glomeruli, kidney tubules, or the interstitium. Common causes of each are glomerulonephritis, acute tubular necrosis (ATN), and acute interstitial nephritis (AIN), respectively. Other causes of intrinsic AKI are rhabdomyolysis and tumor lysis syndrome.[8] Certain medication classes such as calcineurin inhibitors (e.g., tacrolimus) can also directly damage the tubular cells of the kidney
Video explanation of prerenal acute kidney injury
and result in a form of intrinsic AKI.
Postrenal Postrenal AKI refers to acute kidney injury caused by disease states downstream of the kidney and most often occurs as a consequence of urinary tract obstruction. This may be related to benign prostatic hyperplasia, kidney stones, obstructed urinary catheter, bladder stones, or cancer of the bladder, ureters, or prostate.
Diagnosis
Video explanation of intrarenal acute kidney injury
Definition Introduced by the KDIGO in 2012,[9] specific criteria exist for the diagnosis of AKI. AKI can be diagnosed if any one of the following is present: Increase in SCr by ≥0.3 mg/dl (≥26.5 µmol/l) within 48 hours; or Increase in SCr to ≥1.5 times baseline, which has occurred within the prior 7 days; or Urine volume < 0.5 ml/kg/h for 6 hours. Video explanation of postrenal acute kidney injury
Staging The RIFLE criteria, proposed by the Acute Dialysis Quality Initiative (ADQI) group, aid in assessment of the severity of a person's acute kidney injury. The acronym RIFLE is used to define the spectrum of progressive kidney injury seen in AKI: [10][11] Risk: 1.5-fold increase in the serum creatinine, or glomerular filtration rate (GFR) decrease by 25 percent, or urine output