View source for Acute kidney injury

==Background==
*Majority of cases of community-acquired ARF is secondary to volume depletion although consideration of pre-renal, post renal, and renal causes are important.
===AKI Staging===
{| {{table}}
| align="center" style="background:#f0f0f0;"|'''AKI Stage'''<ref>Moore PK, et. al. Management of acute kidney injury: core curriculum 2018. Am J Kidney Dis. 2018; 72: 136-148.</ref>
| align="center" style="background:#f0f0f0;"|'''KDIGO'''
| align="center" style="background:#f0f0f0;"|'''UOP'''
|-
| 1||Cr 1.5-1.9x baseline over 7d '''or''' ≥0.3 mg/dL increase over 48hrs||<0.5 mL/kg/hr  for 6-12hrs
|-
| 2||Cr 2.0-2.9x baseline||<0.5 mL/kg/hr for >12hrs
|-
| 3||Cr ≥3.0x baseline '''or''' ≥4.0 mg/dL increase '''or''' initiation of RRT||<0.3 mL/kg/hr for >24hrs '''or''' anuria for >12hrs
|-
|}
===Chronic Kidney Disease Stages===
*Useful if patient's baseline creatinine is unknown
**Stage 1: Kidney damage (e.g. [[proteinuria]]) and normal GFR; GFR >90
**Stage 2: Kidney damage (e.g. [[proteinuria]]) and mild decrease in GFR; GFR 60-89
**Stage 3: Moderate decrease in GFR; GFR >30-59
**Stage 4: Severe decrease in GFR; GFR 15-29
**Stage 5: Kidney failure (dialysis or kidney transplant needed); GFR <15

===Risk Factors===
*[[Contrast-Induced Nephropathy|Radiocontrast agents]]
**Especiallyif GFR <60, hypovolemic 
*Atherosclerosis
*Chronic [[hypertension]]
*Chronic kidney disease
*[[NSAIDs]]
*[[ACEI]]/[[ARB]]
*[[Sepsis]]
*[[Hypercalcemia]]
*[[Hepatorenal syndrome]]

==Clinical Features==
*Acute renal failure itself has few symptoms until severe uremia develops:
**[[Nausea/vomiting]], drowsiness, fatigue, confusion, [[coma]], [[pericarditis]]
*Patients more likely to present with symptoms related to underlying cause:
**Prerenal
***Thirst, orthostatic lightheadedness, decreasing urine output
**Intrinsic
***[[Flank pain]], [[hematuria]]
****[[Nephrolithiasis]]
****Papillary necrosis
****Crystal-induced nephropathy
***[[Myalgia]]s, [[seizures]], recreational intoxication
****Pigment-induced ARF ([[rhabdomyolysis]])
***Darkening urine and edema (esp with preceding pharyngitis or cutaneous infection)
****Acute glomerulonephritis
***[[Fever]], [[arthralgia]], [[rash]] 
****Acute interstitial nephritis
***[[Cough]], [[dyspnea]], [[hemoptysis]]
****[[Goodpasture syndrome]], [[granulomatosis with polyangiitis]] (Wegener's)
**Postrenal
***Alternating oliguria and [[polyuria]] is pathognomonic of obstruction
***Anuria

==Etiologies==
[[File:Differential Diagnosis of Acute Kidney Injury.png|thumb]]
===Prerenal===
*[[Hypovolemia]]
**GI: decreased intake, [[vomiting]] and [[diarrhea]]
**[[Hemorrhage]]
**Pharmacologic: [[diuretics]]
**Third spacing
***[[Pancreatitis]]
**Skin losses: [[hyperthermia]], [[burns]]
**Miscellaneous
***Hypoaldosteronism
***Salt-losing nephropathy
***[[Postobstructive diuresis]]
*[[Hypotension]]
**[[Sepsis]]
**Decreased cardiac output: decompensated [[heart failure]], [[tamponade]], massive pulmonary embolus
**[[Hepatorenal Syndrome]]
***Ischemia/infarction
***[[Valvular Disease|Valvulopathy]]
**Pharmacologic
***[[Beta-blockers]]
***[[Calcium-channel blockers]]
***[[Antihypertensive medications]]
**[[High output heart failure]]
***[[Thyrotoxicosis]]
***AV fistula
*Renal artery and small-vessel disease
**Embolism: thrombotic, septic, cholesterol
**Thrombosis: atherosclerosis, [[vasculitis]], [[sickle cell disease]]
**Dissection
**Pharmacologic
***[[NSAIDs]]
***[[ACEI]]/[[ARB]]
****Observed shortly after initiation of therapy
**Microvascular thrombosis
***[[Preeclampsia]]
***[[Hemolytic Uremic Syndrome (HUS)]]
***[[Thrombotic Thrombocytopenic Purpura (TTP)]]
***[[Disseminated Intravascular Coagulation (DIC)]]
***[[Vasculitis]]
***[[Sickle Cell Disease]]
**[[Hypercalcemia]]

===Intrinsic===
*Tubular diseases
**Ischemic acute tubular necrosis
***Caused by more advanced disease due to the prerenal causes
*Nephrotoxins
**[[Aminoglycosides]], [[Contrast-Induced Nephropathy|radiocontrast]], [[amphotericin B]], heme pigments ([[rhabdomyolysis]], hemolysis)
**Obstruction
***Uric acid, calcium oxalate from [[Ethylene Glycol Toxicity]], [[Multiple myeloma]] (immunoglobin light chains), [[amyloidosis]]
***Pharmacologic: [[sulfonamides]], triamterene, [[acyclovir]], indinavir
*Interstitial diseases
**Acute interstitial nephritis: typically a drug reaction ([[NSAIDs]], [[Penicillins]] and antibiotics, [[Diuretics]], [[phenytoin]])
**Infection: bilateral pyelonephritis, [[Legionella]], [[Hantavirus]]
**Infiltrative disease: [[sarcoidosis]], [[lymphoma]]
**Autoimmune diseases: [[SLE]]
*Glomerular diseases
**Rapidly progressive glomerulonephritis
***[[Goodpasture syndrome]], [[granulomatosis with polyangiitis]] (Wegener's) [[HSP]], [[SLE]], membranoproliferative GN
**Postinfectious [[glomerulonephritis]]
*Small-vessel diseases
**Microvascular thrombosis
***[[Preeclampsia]], [[HUS]], [[DIC]], [[Thrombotic Thrombocytopenic Purpura (TTP)|TTP]], [[vasculitis]] (PAN, SCD, atheroembolism)
**[[Malignant hypertension]]
**[[Scleroderma]]
**Renal vein thrombosis
*[[Abdominal compartment syndrome]]
*[[Hepatorenal syndrome]]
*[[Cardiorenal syndrome]]

===Postrenal===
*Infants and children
**Urethra and bladder outlet
***Anatomic malformations
****Urethral atresia
****Meatal stenosis
****Anterior and posterior urethral valves
**Ureter
***Anatomic malformations
****Vesicoureteral reflux (female preponderance)
****Ureterovesical junction obstruction
****Ureterocele
****Retroperitoneal tumor
*All ages
**Various locations in GU tract
***Trauma
***Blood clot
**Urethra and bladder outlet
***[[Phimosis]] or urethral stricture (male preponderance)
***Neurogenic bladder
****[[Diabetes mellitus]], spinal cord disease, [[multiple sclerosis]], [[Parkinson's disease]]
****Pharmacologic: [[anticholinergics]], [[alpha antagonist|a-adrenergic antagonists]], [[opioids]]
*Adults
**Urethra and bladder outlet
***BPH
***Cancer of prostate, bladder, cervix, or colon
***Obstructed catheters
**Ureter
***[[Ureteral calculi]], uric acid crystals
***Papillary necrosis
****[[Sickle cell disease]], [[DM]], [[pyelonephritis]]
***Tumor: Ureter, uterus, prostate, bladder, colon, rectum; retroperitoneal lymphoma
***Retroperitoneal fibrosis: idiopathic, [[tuberculosis]], [[sarcoidosis]], [[propranolol]]
***Stricture: [[TB]], [[Radiation exposure|radiation]], [[schistosomiasis]], [[NSAIDs]]
***Miscellaneous
****[[Abdominal aortic aneurysm|Aortic aneurysm]]
****Pregnant uterus
****[[IBD]]
****[[Renal trauma|Renal]] or [[ureter trauma]]

==Evaluation==
===Work-up===
*Urine
*Prostate exam
*[[Urinalysis]], urine sodium, urine creatinine, urine urea
*[[ECG]] (hyperkalemia)
*Chronic renal failure features
**Anemia, thrombocytopenia
**Iron studies with low Fe, low TIBC, low iron saturation, normal ferritin
**Secondary rise in PTH, high phos, low calcium

===Imaging===
*[[CXR]]
**Evidence of volume overload, pneumonia
*US: [[renal ultrasound|renal]]/[[bladder ultrasound|bladder]]
**Test of choice in setting of acute renal failure
**Bladder size (post-void)
**Hydronephrosis
**IVC collapsibility (prerenal)
*CT
**Useful to determine cause of post renal failure (identification of abdominal masses etc.)
**Should generally not be used with IV contrast due to potential risk for [[Contrast-Induced Nephropathy|CIN]]
**Indicated if hydronephrosis found on [[ultrasound]] in order to define the location of obstruction

===Diagnosis===
{| {{table}}
| align="center" style="background:#f0f0f0;"|'''Finding'''
| align="center" style="background:#f0f0f0;"|'''Prerenal'''
| align="center" style="background:#f0f0f0;"|'''Intrinsic'''
| align="center" style="background:#f0f0f0;"|'''Postrenal'''
|-
| BUN/creatinine ratio||>20||< 12||12-20 (normal range)
|-
| [[FeNa]]^||
*<1% 
*< 2% for neonates
||
* >1% 
*> 2.5% for neonates
||
*>1%
|-
| Urine osm|| >500|| <350||
|-
| Urine sodium ||< 20 mEq/L||> 40 mEq/L||
|-
| Specific gravity ||> 1.020|| < 1.020||
|-
| Fractional excretion of urea ||< 35%|| > 50%||
|-
| Microscopic analysis||
*Hyaline casts
||
*Acute glomerulonephritis: RBCs, casts 
*Acute tubular necrosis: protein, tubular epithelial cells 
*Interstitial nephritis: eosinophils
||
|}

^ (urine sodium/plasma sodium) / (urine creatinine / serum creatinine)

==Management==
''Treat underlying cause''
*Prerenal: [[IVF]] (or [[pRBCs]] if bleeding)
*Intrinsic: Depends on cause
*Obstruction:
**Note: Postobstructive diuresis can result in significant volume loss and death
***Typically occurs when obstruction has been prolonged / has resulted in renal failure 
***Admit patients with persistent diuresis of >250 mL/h for >2hr 
**Foley Catheter, consider [[Coude Catheter]]
**Suprapubic (if Coude fails)

===[[Dialysis]]===
*Indicated for:
**A: [[Acidosis]] (severe)
**E: [[Electrolyte abnormality]] (e.g. uncontrolled [[hyperkalemia]])
**I: Ingestions ([[lithium toxicity|lithium]], [[salicylate toxicity|ASA]], [[methanol]], [[ethylene glycol]], [[theophylline toxicity|theophylline]])
**O: [[fluid overload|Overload]] (volume) with persistent hypoxia
**U: [[uremia|Uremic]] [[pericarditis]]/[[encephalopathy]]/[[coagulopathy|bleeding dyscrasia]]
**Also:
***Na <115 or >165 mEq/L
***creatinine > 10
***BUN >100
*See [[Dialysis catheter placement]]
*See [[Austere peritoneal dialysis]]

===Phlebotomy to Treat [[Pulmonary Edema]]===
*Possible last ditch effort to tide patient over to formal dialysis if hours away
*If traditional pulmonary edema treatments are not working for [[Sympathetic crashing acute pulmonary edema (SCAPE)|SCAPE]] patient, one may attempt to remove 200-300 cc of blood as a bridge to dialysis<ref>Eiser AR et al. Phlebotomy for pulmonary edema in dialysis patients. Clin Nephrol. 1997 Jan;47(1):47-9.</ref>
*If Hb too low, may consider temporary venous tourniquets on each leg proximally q30 min to reduce preload volume to the heart, alternating legs

==Disposition==
*Admit

==See Also==
*[[Hyperkalemia]]
*[[Renal ultrasound]]
*[[Hypertensive emergency]]

==External Links==
*[http://ddxof.com/acute-kidney-injury/ DDxOf: Differential Diagnosis of Acute Kidney Injury]

==References==
<references/>

[[Category:Renal]]