II. Epidemiology

  1. Incidence of Acute Kidney Injury
    1. Overall: 2-3 per 1000 persons
    2. Hospital: 7% of patients
      1. Acute Kidney Injury as primary diagnosis: 504,600 in 2014 U.S. (had been 281,000 in 2006)
      2. Acute Kidney Injury as secondary diagnosis: 2.3 Million in 2014 U.S. (had been 1 Million in 2006)
    3. ICU: Two thirds of patients

III. Definitions

  1. Acute Kidney Injury
    1. Abrupt onset (within 48 hours) and
    2. Reduced Renal Function (Serum Creatinine elevation) and/or
    3. Urine Output decreased and/or
    4. Renal replacement therapy (Dialysis)
  2. Uremia
    1. Blood homeostasis defects related to Renal Failure
    2. Includes Fluid Overload, Hyperkalemia and Metabolic Acidosis
  3. Azotemia
    1. Accumulation of nitrogen waste products in the blood (Blood Urea Nitrogen)

VII. Symptoms: Severe Kidney Injury

  1. Fatigue
  2. Anorexia
  3. Nausea or Vomiting
  4. Weight gain
  5. Edema
  6. Confusion (uremic encephalopathy)

VIII. Signs: Clinical Clues to Kidney injury cause

  1. General
    1. Hemodynamic stability
    2. Volume Status
      1. Tight balance between decreased renal perfusion and Fluid Overload
  2. Cardiovascular exam
    1. Lower Extremity Edema
      1. Congestive Heart Failure
      2. Nephrotic Syndrome
    2. Skin turgur
      1. Tenting in Dehydration
  3. Abdominal exam
    1. Abdominal Aortic Aneurysm
      1. Pulsatile mass
      2. Abdominal bruit
    2. Abdominal Distention
      1. Ascites
    3. Pelvic mass
    4. Prostate enlargement
    5. Distended Bladder
  4. Skin
    1. Rash of drug-induced Interstitial Nephritis
    2. Palpable Purpura
      1. Vasculitis
    3. Non-palpable Purpura
      1. Thrombotic Thrombocytopenic Purpura (TTP)
      2. Hemolytic Uremic Syndrome (HUS)
    4. Livido reticularis
    5. Spider angioma or caput medusae (Cirrhosis)

IX. Stages

  1. Stage 1
    1. Serum Creatinine increased >1.5-2x baseline (or >0.3 mg/dl increase) or
    2. Urine Output <0.5 ml/kg/hour for >6 hours
  2. Stage 2
    1. Serum Creatinine increased >2-3x baseline or
    2. Urine Output <0.5 ml/kg/hour for >12 hours
  3. Stage 3
    1. Serum Creatinine increased >3x baseline or
    2. Serum Creatinine >4.0 mg/dl and acute increase of at least 0.5 mg/dl
    3. Urine Output <0.3 ml/kg/hour for >24 hours (or Anuria for 12 hours)
    4. Requires renal replacement therapy (Dialysis)

X. Labs

  1. Renal Function: Criteria for Acute Renal Failure
    1. See Stages above
    2. Serum Creatinine takes 24-72 hours to reach new steady state after Acute Kidney Injury
    3. Serum Creatinine rises >0.3 mg/dl on 2 contiguous days or
    4. Serum Creatinine rises >0.5 mg/dl or
    5. Serum Creatinine rises >1.5 fold above baseline or
    6. Calculated GFR falls >50% below baseline
    7. Obtain 24 hour Creatinine Clearance
  2. Serum Electrolytes
    1. Serum Potassium (Hyperkalemia)
    2. Serum Sodium
    3. Serum bicarbonate (Metabolic Acidosis)
    4. Serum Calcium
    5. Serum Phosphorus
    6. Serum Magnesium
  3. Fractional Excretion of Sodium (FENa)
    1. Requires urine sample prior to IV fluids and Diuretics
    2. FENa >2%: Intrinsic renal disease (e.g. Acute Tubular Necrosis)
      1. Falsely elevated FENa if on Diuretics
      2. Consider Fractional Excretion of Urea (FEUrea) if on Diuretics
      3. An injured Kidney loses the ability to concentrate urine
    3. FENa <1%: Prerenal Failure
      1. Kidney still able to concentrate urine
      2. Not specific for prerenal causes (see FeNa)
  4. Fractional Excretion of Urea (FEUrea)
    1. FEUrea >50%: Intrinsic renal disease (e.g. Acute Tubular Necrosis)
    2. FEUrea <35%: Prerenal Cause
  5. Complete Blood Count (CBC)
    1. Acute Hemolytic Anemia
      1. Obtain Serum Bilirubin fractionated, serum LDH, Haptoglobin and Peripheral Smear (see below)
      2. May suggest Hemolytic Uremic Syndrome or Thrombotic Thrombocytopenic Purpura
    2. Platelets decreased in uremic Platelet Dysfunction
      1. May be accompanied with bleeding, Purpura
    3. Eosinophils increased in interstitial disease
  6. Autoimmune Testing for Glomerular Disease (Glomerulonephritis)
    1. Antinuclear Antibody (ANA)
    2. Antiglomerular basement membrane Antibody
    3. Antineutrophil Cytoplasmic Antibody (ANCA)
      1. See Small Vessel Vasculitis
    4. Antistreptolysin O
      1. Poststreptococcal Glomerulonephritis
    5. Complement Level
      1. Low in some causes of Acute Glomerulonephritis
  7. Percutaneous Renal Biopsy
    1. Indicated for Glomerular or Interstitial disease of unclear cause (esp. when directing management)
    2. May be urgent in certain cases with rapid progression, Oliguria or positive urine sediment
      1. Consult with Nephrology early when intrinsic Acute Kidney Injury is considered
      2. Glucocorticoids and other immunosuppressants as well as plasmophoresis may be indicated based on biopsy

XI. Labs: Urinalysis with Urine sediment examination

  1. Most important single test in identifying Acute Kidney Injury cause
  2. Urine Specific Gravity
    1. Prerenal Failure: Specific Gravity >1.020
    2. Intrarenal Failure: Specific Gravity 1.010 - 1.020
  3. Vascular disease
    1. Urine RBCs often present
  4. Glomerulonephritis, Vasculitis or Multiple Myeloma
    1. Urine RBCs and Red Blood Cell Casts
    2. Granular Casts
    3. Proteinuria (esp. >3 grams)
    4. Acanthocytes (spiked cells or Spur Cells)
  5. Interstitial Nephritis (includes Drug Hypersensitivity)
    1. Pyuria
    2. Eosinophils
    3. White Blood Cell Casts and Eosinophil casts
  6. Tubular Necrosis
    1. Pigmented Granular Casts
    2. Renal tubular epithelial cells and epithelial cell casts
    3. Granular Casts
  7. Prerenal Failure
    1. Hyaline Casts
  8. Rhabdomyolysis
    1. Orthotolidine positive on Urine Dipstick with negative microscopy for Red Blood Cells

XII. Labs: Additional to consider if indicated

  1. Serum Protein Electrophoresis (SPEP) and Urine Protein electrophoresis (UPEP)
    1. Multiple Myeloma
  2. Uric Acid
    1. Postrenal Failure
  3. Serum Creatine Phosphokinase (CPK) and serum myoglobin
    1. Rhabdomyolysis
  4. Blood Cultures
    1. Endocarditis
  5. HIV Test
    1. HIV Nephropathy
  6. Metabolic Acidosis with increased Anion Gap and increased Osmolar Gap
    1. Acute ingestion (Ethylene gylcol, Methanol)
  7. Peripheral Smear for Hemolysis
    1. Autoimmune Vasculitis (e.g. TTP, HUS, SLE)

XIII. Imaging: Bedside Ultrasound

  1. See Inferior Vena Cava Ultrasound for Volume Status
  2. See Echocardiogram in Congestive Heart Failure (and Echocardiogram)
  3. See Abdominal Aorta Ultrasound
  4. See Bladder Ultrasound
    1. Evaluate for post-void residual urine >100 ml (Bladder scan, Ultrasound or catheter)
  5. See Renal Ultrasound
    1. Obtain formal diagnostic renal Ultrasound in most patients
    2. Intrarenal Failure: May show parenchymal abnormality
    3. Postrenal Failure: Hydronephrosis

XIV. Evaluation

  1. Step 1: Confirm Acute Kidney Injury criteria
    1. See Creatinine under labs above (as well as stages)
    2. Distinguish from Chronic Kidney Disease with normal fluctuation
  2. Step 2: Assess Urine Output
    1. No Oliguria
      1. Go to step 3
    2. Oliguria
      1. Acute Prerenal Failure
        1. Fractional Excretion of Sodium (FENa) <1%
        2. Distinguish volume overload (e.g. CHF) from Dehydration
      2. Acute Intrinsic Renal Failure or Postrenal Failure
        1. Fractional Excretion of Sodium (FENa) <1%
        2. Go to step 3
  3. Step 3: Renal Ultrasound
    1. Hydronephrosis
      1. Postrenal Failure
    2. Small Kidneys bilaterally
      1. Acute on Chronic Renal Failure
    3. Kidneys of normal size
      1. Go to step 4
  4. Step 4: Urinalysis
    1. Interpret urine sediment for cause of renal parenchymal condition (see Urinalysis above)
  5. Step 5: Additional evaluation
    1. See specific labs as above

XV. Management

XVI. Prognosis

XVIII. Resources

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Related Studies

Ontology: Kidney Failure, Acute (C0022660)

Definition (NCI_CTCAE) A disorder characterized by the acute loss of renal function and is traditionally classified as pre-renal (low blood flow into kidney), renal (kidney damage) and post-renal causes (ureteral or bladder outflow obstruction).
Definition (NCI) Sudden and sustained deterioration of the kidney function characterized by decreased glomerular filtration rate, increased serum creatinine or oliguria.
Definition (CSP) clinical syndrome characterized by a sudden decrease in glomerular filtration rate, usually associated with oliguria and always associated with biochemical consequences of the reduction in glomerular filtration rate such as a rise in blood urea nitrogen (BUN) and serum creatinine concentrations.
Concepts Disease or Syndrome (T047)
MSH D007675 , D058186
ICD9 584, 584.9
ICD10 N17 , N17.9
SnomedCT 14669001, 197653006, 155855008
English Kidney Failure, Acute, RENAL FAILURE ACUTE, RENAL SHUTDOWN ACUTE, Acute renal failure NOS, Acute renal failure, unspecified, ARF, acute renal failure, acute renal failure (diagnosis), ARF (acute renal failure), Failure kidney acute, Kidney failure acute, Renal failure acute, Renal shutdown acute, Acute kidney failure NOS, Acute and unspecified renal failure, Acute kidney failure, unspecified, Kidney Failure, Acute [Disease/Finding], Acute Kidney Failure, Kidney Failures, Acute, Acute Renal Failure, Renal Failure, Acute, Acute Kidney Failures, Acute Renal Failures, Renal Failures, Acute, kidney failure acute, Failure;renal;acute, syndrome acute renal failure, acute renal failures, renal failure acute, acute renal shutdown, acute failure kidney, acute kidney failure, arf, failure acute renal, acute failure renal, acute renal insufficiency, Acute renal failure, Acute renal failure NOS (disorder), Acute renal failure (disorder), Acute kidney failure, AKI, Acute kidney injury, Acute renal failure syndrome, ARF - Acute renal failure, Acute renal failure syndrome (disorder), Acute renal failure syndrome, NOS
French INSUFFISANCE RENALE AIGUE, Insuffisance rénale aiguë, Ligo-anurie aiguë, Insuffisance rénale aiguë, non précisée, SIDERATION RENALE, Défaillance rénale aigüe, Défaillance rénale aiguë
Portuguese INSUFICIENCIA RENAL AGUDA, Insuficiência renal aguda NE, Falência renal aguda, PARALIZACAO RENAL, Insuficiência renal aguda
Spanish INSUFICIENCIA RENAL AGUDA, Fallo renal agudo, Insuficiencia renal aguda no especificada, FALLO RENAL AGUDO, Insuficiencia renal aguda
Dutch niet-gespecificeerd acuut nierfalen, acuut falen nier, Acute nierinsufficiëntie, niet gespecificeerd, acuut nierfalen, Nierfalen, acuut, Acute nierinsufficiëntie, Insufficiëntie, acute nier-, Nierinsufficiëntie, acute, Renale insufficiëntie, acute
German akutes Nierenversagen, akutes Nierenversagen, unspezifisch, Versagen der Niere akut, Nierenausfall akut, Akutes Nierenversagen, nicht naeher bezeichnet, NIERENEMBOLIE, NIERENVERSAGEN AKUT, Renales Versagen, akutes, Akutes Nierenversagen, Nierenversagen, akutes, Nierenversagen akut
Italian Insufficienza renale acuta, non specificata, Insufficienza renale acuta
Japanese 急性腎不全、詳細不明, 急性腎不全, 急性腎機能停止, キュウセイジンフゼンショウサイフメイ, キュウセイジンキノウテイシ, キュウセイジンフゼン
Swedish Njursvikt, akut
Finnish Munuaisten äkillinen vajaatoiminta
Czech Akutní selhání ledvin, Renální selhání akutní, Akutní renální selhání, Akutní renální selhání blíže neurčené, akutní selhání ledvin, ledviny - selhání akutní
Korean 상세불명의 급성 콩팥(신장)기능상실, 급성 콩팥(신장)기능상실
Hungarian acut veseelégtelenség, Acut veseelégtelenség, Acut veseelégtelenség, k.m.n., Acut veseleállás
Norwegian Akutt nyresvikt

Ontology: Kidney Tubular Necrosis, Acute (C0022672)

Definition (NCI) Acute renal failure caused by the cell death of the renal tubules. Causes include nephrotoxins, cytotoxic drugs, and antibiotics.
Definition (MSH) Acute kidney failure resulting from destruction of EPITHELIAL CELLS of the KIDNEY TUBULES. It is commonly attributed to exposure to toxic agents or renal ISCHEMIA following severe TRAUMA.
Concepts Disease or Syndrome (T047)
MSH D007683
ICD10 N17.0
SnomedCT 23697004, 197649009, 35455006
English Acute Kidney Tubular Necrosis, Kidney Tubular Necrosis, Acute, Lower Nephron Nephroses, Lower Nephron Nephrosis, Nephron Nephroses, Lower, Nephron Nephrosis, Lower, Nephroses, Lower Nephron, Nephrosis, Lower Nephron, LOWER NEPHRON NEPHROSIS, ATN - Acute tubular necrosis, Acute renal failure with tubular necrosis, TUBULAR NECROSIS ACUTE, lower nephron nephrosis, Renal tubular necrosis acute, Nephrosis lower nephron, Kidney Tubular Necrosis, Acute [Disease/Finding], acute tubular necrosis, acute renal tubular necrosis, acute necrosis tubular, Lower nephron nephrosis, Acute Tubular Necrosis, Acute tubular necrosis, Tubulorrhexis, Acute renal tubular necrosis, Acute tubular necrosis (disorder), Acute tubule necrosis, insufficiency; renal, acute, with necrosis, tubular, insufficiency; renal, with tubular necrosis (acute), kidney; insufficiency, acute, with necrosis, tubular, kidney; insufficiency, with tubular necrosis (acute), Acute tubular necrosis, NOS, Acute Renal Failure with Tubular Necrosis
Dutch nefrose in het onderste nefron, acute tubulusnecrose, acute tubulaire nefrose in het onderste nefron, acute niertubulusnecrose, insufficiëntie; nier, acuut, met necrose, tubulus, insufficiëntie; nier, met tubulusnecrose (acuut), nier; insufficiëntie, acuut, met necrose, tubulus, nier; insufficiëntie, met tubulusnecrose (acuut), Acute nierinsufficiëntie met tubulusnecrose, ATN, Acute tubulusnecrose, Lower-nephron necrosis, Necrose, acute tubulus-, Niertubulusnecrose, acute, Tubulusnecrose, acute
French Néphrose du néphron inférieur, Nécrose tubulaire rénale aiguë, Nécrose tubulaire aiguë, Néphrite tubulaire aigüe, Néphropathie tubulo-interstitielle aiguë, Néphropathie tubulo-interstitielle aigüe, Tubulo-néphrite aigüe, NEPHROSE LOCALISEE AU TUBE DISTAL, Néphrite tubulaire aiguë, Tubulo-néphrite aiguë
German akute Nierentubulusnekrose, Nephrose Tubulus, Nierentubulusnekrose akut, Tubulusnephrose, Akutes Nierenversagen mit Tubulusnekrose, NEPHROSE TUBULAER BEDINGT, Akute Tubulusnekrose, Nierentubulusnekrose, akute
Italian Nefrosi tubulare, Necrosi tubulare renale acuta, Necrosi tubulare acuta, Necrosi tubulorenale acuta
Portuguese Nefrose do nefrónio inferior, Necrose tubular aguda, Necrose renal tubular aguda, NEFROSE DA ALCA DE HENLE, Necrose Tubular Aguda, Nefrose do Néfron Inferior
Spanish Necrosis tubular aguda, Nefrosis de la nefrona inferior, Necrosis tubular renal aguda, Nefrosis de la Nefrona Distal, NEFROSIS NEFRONA INFERIOR, necrosis tubular aguda (trastorno), necrosis tubular aguda, necrosis tubular renal aguda, tubulorrexis, Necrosis Tubular Aguda
Swedish Njurkanalnekros, akut
Japanese キュウセイジンニョウサイカンエシ, カブネフロンネフローゼ, 尿細管壊死-急性, 下部ネフロンネフローゼ, 急性尿細管え死, 急性尿細管壊死, 急性腎尿細管壊死, 腎尿細管壊死-急性
Finnish Äkillinen munuaistiehyeiden kuolio
Czech Nefróza dolního nefronu, Akutní tubulární nekróza, Akutní renální tubulární nekróza, akutní tubulární nekróza, akutní parenchymatózní renální selhání, ledviny - tubulární nekróza akutní
Korean 세뇨관 괴사를 동반한 급성 콩팥(신장)기능상실
Polish Ostra nekroza kanalików nerkowych, Ostra martwica kanalikowa, Martwica cewek nerkowych ostra, Ostra niewydolność nerek z martwicą cewek, Ostra martwica cewek nerkowych
Hungarian Acut renalis tubularis necrosis, Alsó nephron nephrosis, Acut tubularis necrosis
Norwegian Akutt tubulær nekrose

Ontology: Uremia (C0041948)

Definition (CSP) excess in the blood of urea, creatinine and other nitrogenous end products of protein and aminoacid metabolism; also, the constellation of signs and symptoms of chronic renal failure.
Definition (MSH) A clinical syndrome associated with the retention of renal waste products or uremic toxins in the blood. It is usually the result of RENAL INSUFFICIENCY. Most uremic toxins are end products of protein or nitrogen CATABOLISM, such as UREA or CREATININE. Severe uremia can lead to multiple organ dysfunctions with a constellation of symptoms.
Concepts Disease or Syndrome (T047)
MSH D014511
ICD10 N19
SnomedCT 266616000, 197656003, 44730006
English Uremias, URAEMIA, URAEMIA OF RENAL ORIGIN, UREMIA, UREMIA OF RENAL ORIGIN, Uraemia NOS, uremia, uremia (diagnosis), Uraemia of renal origin, Uremia of renal origin, Uremia [Disease/Finding], Uremia NOS, Uraemia, Uremia (disorder), urea in blood; high, Uremia, NOS, Uraemia, NOS, Uremia, uraemia
French UREMIE, Urémie d'origine rénale, UREMIE D'ORIGINE RENALE, Urémie
Portuguese UREMIA, Uremia de origem renal, UREMIA DE ORIGEM RENAL, Uremia
Spanish UREMIA, Azotemia, Uremia de origen renal, UREMIA DE ORIGEN RENAL, uremia (trastorno), uremia, Uremia
German URAEMIE, Uraemie, Uraemie renalen Ursprungs, URAEMIE RENALER GENESE, Harnvergiftung, Urämie
Dutch uremie, uremie van renale oorsprong, ureum in bloed; hoog, Uremie
Italian Uremia di origine renale, Uremia
Japanese 尿毒症, 腎性尿毒症, ジンセイニョウドクショウ, ニョウドクショウ
Swedish Uremi
Finnish Uremia
Czech Uremie, Uremie z renálních příčin, urémie, uremie
Croatian UREMIJA
Polish Mocznica
Hungarian Vese eredetű uraemia, uraemia, Uraemia
Norwegian Urinforgiftning, Uremi

Ontology: Azotemia (C0242528)

Definition (MSH) A biochemical abnormality referring to an elevation of BLOOD UREA NITROGEN and CREATININE. Azotemia can be produced by KIDNEY DISEASES or other extrarenal disorders. When azotemia becomes associated with a constellation of clinical signs, it is termed UREMIA.
Concepts Disease or Syndrome (T047)
MSH D053099
SnomedCT 445009001, 282151000009107
English AZOTEMIA, Azotemia (disorder), Azotaemia, Azotemia [Disease/Finding], azotaemia, azotemia, Azotemia (finding), Azotemia
Portuguese AZOTEMIA, Azotemia
Italian Azotemia, Presenza di urea nel sangue, Azotemia prerenale
Spanish Azotemia, AZOEMIA, azoemia, azoemia (trastorno), Azoemia, Uremia
German Azotämie, AZOTAEMIE, Azotaemie
French Azotémie, HYPERAZOTEMIE
Japanese 高窒素血症, コウチッソケッショウ
Czech azotémie, Azotemie
Finnish Atsotemia
Swedish Azotemi
Polish Azotemia
Hungarian azotaemia, azotémia
Norwegian Azotemi
Dutch azotemie

Ontology: Acute kidney injury (C2609414)

Definition (MSH) Abrupt reduction in kidney function. Acute kidney injury encompasses the entire spectrum of the syndrome including acute kidney failure; ACUTE KIDNEY TUBULAR NECROSIS; and other less severe conditions.
Concepts Injury or Poisoning (T037)
MSH D058186
Spanish Lesión renal aguda, Lesión Renal Aguda
English Acute kidney injury, Acute Kidney Injury, Acute Renal Injuries, Renal Injury, Acute, Acute Kidney Injuries, Acute Renal Injury, Renal Injuries, Acute, Kidney Injury, Acute, Kidney Injuries, Acute, Acute Kidney Injury [Disease/Finding]
Portuguese Lesão renal aguda, Lesão Renal Aguda
Dutch acuut nierletsel
German akute Nierenschaedigung, Akute Nierenschädigung, Akute Nierenschaedigung, Akute Nierenverletzung
Czech Akutní poranění ledvin, ledviny - akutní poškození, akutní poškození ledvin, AKI
Japanese 急性腎不全, キュウセイジンフゼン
French Lésion rénale aiguë, Atteinte rénale aigüe, Atteinte rénale aiguë, Lésion rénale aigüe
Italian Lesione renale acuta
Hungarian Acut vesesérülés
Polish Niewydolność nerek ostra, Ostra niewydolność nerek, Ostre uszkodzenie nerek, Zaburzenia funkcji nerek ostre, Ostre zaburzenia funkcji nerek, Uszkodzenie nerek ostre, Ostra dysfunkcja nerek, Ostra niedomoga nerek
Norwegian Akutt nyreskade, Nyreskade, akutt