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Acute kidney injury (AKI), previously called acute renal failure (ARF),JOURNAL, Webb S, Dobb G, ARF, ATN or AKI? It’s now acute kidney injury, Anaesthesia and Intensive Care, 35, 6, 843–44, December 2007, 18084974, 10.1177/0310057X0703500601, free, BOOK, Dan Longo, Anthony Fauci, Dennis Kasper, Stephen Hauser, J. Jameson, Joseph Loscalzo, Harrison’s Principles of Internal Medicine, 18 edition, July 21, 2011, McGraw-Hill Professional, is a sudden decrease in kidney function that develops within 7 days,JOURNAL, Mehta RL, Kellum JA, Shah SV, Molitoris BA, Ronco C, Warnock DG, Adeera Levin, Levin A, Acute Kidney Injury Network: report of an initiative to improve outcomes in acute kidney injury, Critical Care, 11, 2, R31, 2007, 17331245, 2206446, 10.1186/cc5713, free, as shown by an increase in serum creatinine or a decrease in urine output, or both.JOURNAL, Ronco C, Bellomo R, Kellum JA, Acute kidney injury, The Lancet, 394, 1949–64, 23 November 2019, 10212, 31777389, 10.1016/S0140-6736(19)32563-2, 208230983, Causes of AKI are classified as either prerenal (due to decreased blood flow to the kidney), intrinsic renal (due to damage to the kidney itself), or postrenal (due to blockage of urine flow).JOURNAL, Mercado MG, Smith DK, Guard EL, Acute Kidney Injury: Diagnosis and Management, American Family Physician, 100, 11, 687–694, 1 December 2019, 31790176, Prerenal causes of AKI include sepsis, dehydration, excessive blood loss, cardiogenic shock, heart failure, cirrhosis, and certain medications like ACE inhibitors or NSAIDs. Intrinsic renal causes of AKI include glomerulonephritis, lupus nephritis, acute tubular necrosis, certain antibiotics, and chemotherapeutic agents. Postrenal causes of AKI include kidney stones, bladder cancer, neurogenic bladder, enlargement of the prostate, narrowing of the urethra, and certain medications like anticholinergics.The diagnosis of AKI is made based on a person’s signs and symptoms, along with lab tests for serum creatinine and measurement of urine output. Other tests include urine microscopy and urine electrolytes. Renal ultrasound can be obtained when a postrenal cause is suspected. A kidney biopsy may be obtained when intrinsic renal AKI is suspected and the cause is unclear.AKI is seen in 10-15% of people admitted to the hospital and in more than 50% of people admitted to the intensive care unit (ICU). AKI may lead to a number of complications, including metabolic acidosis, high potassium levels, uremia, changes in body fluid balance, effects on other organ systems, and death. People who have experienced AKI are at increased risk of developing chronic kidney disease in the future. Management includes treatment of the underlying cause and supportive care, such as renal replacement therapy.

Signs and symptoms

The clinical presentation is often dominated by the underlying cause. The various 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.BOOK, Skorecki K, Green J, Brenner BM, Kasper DL, Braunwald E, Fauci AS, Harrison’s Principles of Internal Medicine,archive.org/details/harrisonsprincip00kasp, limited, 16th, 2005, McGraw-Hill, New York, NY, 978-0-07-139140-5, 1653–63, Chronic renal failure, etal, Marked increases in the potassium level can lead to abnormal heart rhythms, which can be severe and life-threatening.JOURNAL, Weisberg LS, 33811639, Management of severe hyperkalemia, Crit. Care Med., 36, 12, 3246–51, December 2008, 18936701, 10.1097/CCM.0b013e31818f222b, Fluid balance is frequently affected, though blood pressure can be high, low, or normal.BOOK, Tierney, Lawrence M., Stephen J. McPhee, Maxine A. Papadakis, CURRENT Medical Diagnosis and Treatment 2005, 44th, 2004, McGraw-Hill, 978-0-07-143692-2, 871, 22, registration,archive.org/details/currentmedicaldi0000unse,archive.org/details/currentmedicaldi0000unse/page/871, 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.BOOK, Brady HR, Brenner BM, Kasper DL, Braunwald E, Fauci AS, Harrison’s Principles of Internal Medicine,archive.org/details/harrisonsprincip00kasp, limited, 16th, 2005, McGraw-Hill, New York, NY, 978-0-07-139140-5, 1644–53, Chronic renal failure, etal, If the kidney injury is the result of dehydration, there may be thirst as well as evidence of fluid depletion on physical examination. 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.

Causes

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), hepatorenal syndrome in the context of liver cirrhosis, and local changes to the blood vessels supplying the kidney (e.g. NSAID induced vasoconstriction of afferent arteriole). 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.{{cn|date=March 2023}}

Intrinsic or Intrarenal

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.BOOK, Jim Cassidy, Donald Bissett, Roy A. J. Spence, Miranda Payne, Oxford Handbook of Oncology,books.google.com/books?id=WKoQW4G0g14C&pg=PA706, 1 January 2010, Oxford University Press, 706, 978-0-19-956313-5, Certain medication classes such as calcineurin inhibitors (e.g., tacrolimus) can also directly damage the tubular cells of the kidney and result in a form of intrinsic AKI.JOURNAL, Shirali, Anushree, Pazhayattil, George Sunny, December 2014, Drug-induced impairment of renal function, International Journal of Nephrology and Renovascular Disease, 7, 457–468, 10.2147/ijnrd.s39747, free, 25540591, 4270362, 1178-7058,

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

Definition

Introduced by the KDIGO in 2012,JOURNAL, Stevens PE, Levin A, Evaluation and management of chronic kidney disease: synopsis of the kidney disease: improving global outcomes 2012 clinical practice guideline, Ann Intern Med, 158, 11, 825–30, June 2013, 23732715, 10.7326/0003-4819-158-11-201306040-00007, 46171014, 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.

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:JOURNAL, Bellomo R, Ronco C, Kellum JA, Mehta RL, Palevsky P, Acute renal failure - definition, outcome measures, animal models, fluid therapy and information technology needs: the Second International Consensus Conference of the Acute Dialysis Quality Initiative (ADQI) Group, Crit Care, 8, 4, R204–12, 2004, 15312219, 522841, 10.1186/cc2872, free, JOURNAL, Lameire N, Van Biesen W, Vanholder R, Acute renal failure, The Lancet, Lancet, 365, 9457, 417–30, 2005, 15680458, 10.1016/S0140-6736(05)17831-3, 37093076, (File:Acute Renal Failure.svg|thumb|Pathophysiology of acute kidney injury in the proximal renal tubule)

• Risk: 1.5-fold increase in the serum creatinine, or glomerular filtration rate (GFR) decrease by 25 percent, or urine output