Acute kidney injury: Difference between revisions
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(table of AKI staging, KDIGO is preferred, specified conditions of dec cardiac output) |
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==Background== | ==Background== | ||
*Majority of cases of community-acquired ARF is secondary to volume depletion | *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=== | ===Chronic Kidney Disease Stages=== | ||
*Useful if patient's baseline creatinine is unknown | *Useful if patient's baseline creatinine is unknown | ||
**Stage 1: Kidney damage (e.g. proteinuria) and normal GFR; GFR >90 | **Stage 1: Kidney damage (e.g. [[proteinuria]]) and normal GFR; GFR >90 | ||
**Stage 2: Kidney damage (e.g. proteinuria) and mild | **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 3: Moderate decrease in GFR; GFR >30-59 | ||
**Stage 4: Severe decrease in GFR; GFR 15-29 | **Stage 4: Severe decrease in GFR; GFR 15-29 | ||
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===Risk Factors=== | ===Risk Factors=== | ||
*[[Contrast-Induced Nephropathy|Radiocontrast agents]] | *[[Contrast-Induced Nephropathy|Radiocontrast agents]] | ||
** | **Especiallyif GFR <60, hypovolemic | ||
*Atherosclerosis | *Atherosclerosis | ||
*Chronic hypertension | *Chronic [[hypertension]] | ||
*Chronic kidney disease | *Chronic kidney disease | ||
*NSAIDs | *[[NSAIDs]] | ||
*ACEI/ARB | *[[ACEI]]/[[ARB]] | ||
*[[Sepsis]] | *[[Sepsis]] | ||
*[[Hypercalcemia]] | *[[Hypercalcemia]] | ||
*Hepatorenal syndrome | *[[Hepatorenal syndrome]] | ||
==Clinical Features== | ==Clinical Features== | ||
*Acute renal failure itself has few symptoms until severe uremia develops: | *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 | **Prerenal | ||
***Thirst, orthostatic | ***Thirst, orthostatic lightheadedness, decreasing urine output | ||
**Intrinsic | **Intrinsic | ||
***Flank pain, hematuria | ***[[Flank pain]], [[hematuria]] | ||
****Nephrolithiasis | ****[[Nephrolithiasis]] | ||
****Papillary necrosis | ****Papillary necrosis | ||
****Crystal-induced nephropathy | ****Crystal-induced nephropathy | ||
*** | ***[[Myalgia]]s, [[seizures]], recreational intoxication | ||
****Pigment-induced ARF ( | ****Pigment-induced ARF ([[rhabdomyolysis]]) | ||
***Darkening urine and edema (esp | ***Darkening urine and edema (esp with preceding pharyngitis or cutaneous infection) | ||
****Acute glomerulonephritis | ****Acute glomerulonephritis | ||
***Fever, arthralgia, rash | ***[[Fever]], [[arthralgia]], [[rash]] | ||
****Acute interstitial nephritis | ****Acute interstitial nephritis | ||
***Cough, dyspnea, hemoptysis | ***[[Cough]], [[dyspnea]], [[hemoptysis]] | ||
****Goodpasture, Wegener | ****[[Goodpasture syndrome]], [[granulomatosis with polyangiitis]] (Wegener's) | ||
**Postrenal | **Postrenal | ||
***Alternating oliguria and polyuria is pathognomonic of obstruction | ***Alternating oliguria and [[polyuria]] is pathognomonic of obstruction | ||
***Anuria | ***Anuria | ||
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[[File:Differential Diagnosis of Acute Kidney Injury.png|thumb]] | [[File:Differential Diagnosis of Acute Kidney Injury.png|thumb]] | ||
===Prerenal=== | ===Prerenal=== | ||
*Hypovolemia | *[[Hypovolemia]] | ||
**GI: decreased intake, vomiting and diarrhea | **GI: decreased intake, [[vomiting]] and [[diarrhea]] | ||
**Pharmacologic: diuretics | **[[Hemorrhage]] | ||
**Pharmacologic: [[diuretics]] | |||
**Third spacing | **Third spacing | ||
***[[Pancreatitis]] | ***[[Pancreatitis]] | ||
**Skin losses: | **Skin losses: [[hyperthermia]], [[burns]] | ||
**Miscellaneous | **Miscellaneous | ||
***Hypoaldosteronism | ***Hypoaldosteronism | ||
***Salt-losing nephropathy | ***Salt-losing nephropathy | ||
***Postobstructive diuresis | ***[[Postobstructive diuresis]] | ||
*[[Hypotension]] | *[[Hypotension]] | ||
** | **[[Sepsis]] | ||
** | **Decreased cardiac output: decompensated [[heart failure]], [[tamponade]], massive pulmonary embolus | ||
** | **[[Hepatorenal Syndrome]] | ||
***Ischemia/infarction | ***Ischemia/infarction | ||
***Valvulopathy | ***[[Valvular Disease|Valvulopathy]] | ||
**Pharmacologic | **Pharmacologic | ||
*** | ***[[Beta-blockers]] | ||
*** | ***[[Calcium-channel blockers]] | ||
***Antihypertensive medications | ***[[Antihypertensive medications]] | ||
**High | **[[High output heart failure]] | ||
***[[Thyrotoxicosis]] | ***[[Thyrotoxicosis]] | ||
***AV fistula | ***AV fistula | ||
*Renal artery and small-vessel disease | *Renal artery and small-vessel disease | ||
**Embolism: thrombotic, septic, cholesterol | **Embolism: thrombotic, septic, cholesterol | ||
**Thrombosis: atherosclerosis, vasculitis, sickle cell disease | **Thrombosis: atherosclerosis, [[vasculitis]], [[sickle cell disease]] | ||
**Dissection | **Dissection | ||
**Pharmacologic | **Pharmacologic | ||
***NSAIDs | ***[[NSAIDs]] | ||
***ACEI/ARB | ***[[ACEI]]/[[ARB]] | ||
****Observed shortly after initiation of therapy | ****Observed shortly after initiation of therapy | ||
**Microvascular thrombosis | **Microvascular thrombosis | ||
***Preeclampsia | ***[[Preeclampsia]] | ||
***HUS | ***[[Hemolytic Uremic Syndrome (HUS)]] | ||
***DIC | ***[[Thrombotic Thrombocytopenic Purpura (TTP)]] | ||
*** | ***[[Disseminated Intravascular Coagulation (DIC)]] | ||
*** | ***[[Vasculitis]] | ||
**Hypercalcemia | ***[[Sickle Cell Disease]] | ||
**[[Hypercalcemia]] | |||
===Intrinsic=== | ===Intrinsic=== | ||
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***Caused by more advanced disease due to the prerenal causes | ***Caused by more advanced disease due to the prerenal causes | ||
*Nephrotoxins | *Nephrotoxins | ||
**Aminoglycosides, [[Contrast-Induced Nephropathy|radiocontrast]], amphotericin, heme pigments ([[ | **[[Aminoglycosides]], [[Contrast-Induced Nephropathy|radiocontrast]], [[amphotericin B]], heme pigments ([[rhabdomyolysis]], hemolysis) | ||
**Obstruction | **Obstruction | ||
***Uric acid, calcium oxalate, myeloma, | ***Uric acid, calcium oxalate from [[Ethylene Glycol Toxicity]], [[Multiple myeloma]] (immunoglobin light chains), [[amyloidosis]] | ||
***Pharmacologic: | ***Pharmacologic: [[sulfonamides]], triamterene, [[acyclovir]], indinavir | ||
*Interstitial diseases | *Interstitial diseases | ||
**Acute interstitial nephritis: typically a drug reaction (NSAIDs, | **Acute interstitial nephritis: typically a drug reaction ([[NSAIDs]], [[Penicillins]] and antibiotics, [[Diuretics]], [[phenytoin]]) | ||
**Infection: bilateral pyelonephritis, | **Infection: bilateral pyelonephritis, [[Legionella]], [[Hantavirus]] | ||
**Infiltrative disease: sarcoidosis, lymphoma | **Infiltrative disease: [[sarcoidosis]], [[lymphoma]] | ||
**Autoimmune diseases: SLE | **Autoimmune diseases: [[SLE]] | ||
*Glomerular diseases | *Glomerular diseases | ||
**Rapidly progressive glomerulonephritis | **Rapidly progressive glomerulonephritis | ||
***Goodpasture, Wegener | ***[[Goodpasture syndrome]], [[granulomatosis with polyangiitis]] (Wegener's) [[HSP]], [[SLE]], membranoproliferative GN | ||
**Postinfectious glomerulonephritis | **Postinfectious [[glomerulonephritis]] | ||
*Small-vessel diseases | *Small-vessel diseases | ||
**Microvascular thrombosis | **Microvascular thrombosis | ||
***Preeclampsia, [[HUS]], [[DIC]], [[ | ***[[Preeclampsia]], [[HUS]], [[DIC]], [[Thrombotic Thrombocytopenic Purpura (TTP)|TTP]], [[vasculitis]] (PAN, SCD, atheroembolism) | ||
**Malignant hypertension | **[[Malignant hypertension]] | ||
**Scleroderma | **[[Scleroderma]] | ||
**Renal vein thrombosis | **Renal vein thrombosis | ||
*[[Abdominal compartment syndrome]] | |||
*[[Hepatorenal syndrome]] | |||
*[[Cardiorenal syndrome]] | |||
===Postrenal=== | ===Postrenal=== | ||
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***Blood clot | ***Blood clot | ||
**Urethra and bladder outlet | **Urethra and bladder outlet | ||
***Phimosis or urethral stricture (male preponderance) | ***[[Phimosis]] or urethral stricture (male preponderance) | ||
***Neurogenic bladder | ***Neurogenic bladder | ||
**** | ****[[Diabetes mellitus]], spinal cord disease, [[multiple sclerosis]], [[Parkinson's disease]] | ||
****Pharmacologic: anticholinergics, a-adrenergic antagonists, | ****Pharmacologic: [[anticholinergics]], [[alpha antagonist|a-adrenergic antagonists]], [[opioids]] | ||
*Adults | *Adults | ||
**Urethra and bladder outlet | **Urethra and bladder outlet | ||
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***Obstructed catheters | ***Obstructed catheters | ||
**Ureter | **Ureter | ||
*** | ***[[Ureteral calculi]], uric acid crystals | ||
***Papillary necrosis | ***Papillary necrosis | ||
**** | ****[[Sickle cell disease]], [[DM]], [[pyelonephritis]] | ||
***Tumor: Ureter, uterus, prostate, bladder, colon, rectum; retroperitoneal lymphoma | ***Tumor: Ureter, uterus, prostate, bladder, colon, rectum; retroperitoneal lymphoma | ||
***Retroperitoneal fibrosis: idiopathic, tuberculosis, sarcoidosis, propranolol | ***Retroperitoneal fibrosis: idiopathic, [[tuberculosis]], [[sarcoidosis]], [[propranolol]] | ||
***Stricture: TB, radiation, schistosomiasis, NSAIDs | ***Stricture: [[TB]], [[Radiation exposure|radiation]], [[schistosomiasis]], [[NSAIDs]] | ||
***Miscellaneous | ***Miscellaneous | ||
****Aortic aneurysm | ****[[Abdominal aortic aneurysm|Aortic aneurysm]] | ||
****Pregnant uterus | ****Pregnant uterus | ||
****IBD | ****[[IBD]] | ||
**** | ****[[Renal trauma|Renal]] or [[ureter trauma]] | ||
== | ==Evaluation== | ||
*Prerenal | *Prerenal | ||
**BUN/ | **BUN/creatinine ratio > 20 | ||
**FeNa <1% ((urine sodium/plasma sodium) / (urine creatinine / serum creatinine)) | **FeNa <1% ((urine sodium/plasma sodium) / (urine creatinine / serum creatinine)) | ||
***< 2% for neonates | ***< 2% for neonates | ||
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*Urine | *Urine | ||
*Prostate exam | *Prostate exam | ||
* | *[[Urinalysis]], urine sodium, urine creatinine, urine urea | ||
*ECG (hyperkalemia) | *[[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=== | ===Imaging=== | ||
*CXR | *[[CXR]] | ||
*Evidence of volume overload, | **Evidence of volume overload, pneumonia | ||
*US | *US: [[renal ultrasound|renal]]/[[bladder ultrasound|bladder]] | ||
**Test of choice in setting of acute renal failure | **Test of choice in setting of acute renal failure | ||
**Bladder size (post-void) | **Bladder size (post-void) | ||
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**Useful to determine cause of post renal failure (identification of abdominal masses etc.) | **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]] | **Should generally not be used with IV contrast due to potential risk for [[Contrast-Induced Nephropathy|CIN]] | ||
**Indicated if | **Indicated if hydronephrosis found on [[ultrasound]] in order to define the location of obstruction | ||
== | ==Management== | ||
''Treat underlying cause'' | ''Treat underlying cause'' | ||
*Prerenal: IVF | *Prerenal: [[IVF]] (or [[pRBCs]] if bleeding) | ||
*Intrinsic: Depends on cause | *Intrinsic: Depends on cause | ||
*Obstruction: | *Obstruction: | ||
**Note: Postobstructive diuresis can result in significant volume loss and death | **Note: Postobstructive diuresis can result in significant volume loss and death | ||
***Typically occurs when obstruction has been prolonged / has resulted in renal failure | ***Typically occurs when obstruction has been prolonged / has resulted in renal failure | ||
***Admit patients | ***Admit patients with persistent diuresis of >250 mL/h for >2hr | ||
**Foley Catheter, consider [[Coude Catheter]] | **Foley Catheter, consider [[Coude Catheter]] | ||
**Suprapubic (if Coude fails) | **Suprapubic (if Coude fails) | ||
===Dialysis=== | ===[[Dialysis]]=== | ||
*Indicated for: | *Indicated for: | ||
**A: Acidosis (severe) | **A: [[Acidosis]] (severe) | ||
**E: Electrolyte abnormality (e.g. uncontrolled hyperkalemia) | **E: [[Electrolyte abnormality]] (e.g. uncontrolled [[hyperkalemia]]) | ||
**I: Ingestions (lithium, ASA, methanol, ethylene glycol, theophylline) | **I: Ingestions ([[lithium toxicity|lithium]], [[salicylate toxicity|ASA]], [[methanol]], [[ethylene glycol]], [[theophylline toxicity|theophylline]]) | ||
**O: Overload (volume) | **O: [[fluid overload|Overload]] (volume) with persistent hypoxia | ||
**U: Uremic pericarditis/encephalopathy/bleeding dyscrasia | **U: [[uremia|Uremic]] [[pericarditis]]/[[encephalopathy]]/[[coagulopathy|bleeding dyscrasia]] | ||
**Also: | **Also: | ||
***Na <115 or >165 mEq/L | ***Na <115 or >165 mEq/L | ||
*** | ***creatinine > 10 | ||
***BUN >100 | ***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== | ==Disposition== | ||
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==See Also== | ==See Also== | ||
*[[Hyperkalemia]] | *[[Hyperkalemia]] | ||
*[[ | *[[Renal ultrasound]] | ||
*[[Hypertensive emergency]] | *[[Hypertensive emergency]] | ||
==External Links== | ==External Links== | ||
* [http://ddxof.com/acute-kidney-injury/ DDxOf: Differential Diagnosis of Acute Kidney Injury] | *[http://ddxof.com/acute-kidney-injury/ DDxOf: Differential Diagnosis of Acute Kidney Injury] | ||
==References== | ==References== | ||
<references/> | |||
[[Category:Renal]] | [[Category:Renal]] |
Revision as of 04:32, 4 May 2020
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
AKI Stage[1] | KDIGO | 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
- 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
- Myalgias, 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)
- Flank pain, hematuria
- Postrenal
- Alternating oliguria and polyuria is pathognomonic of obstruction
- Anuria
- Prerenal
Etiologies
Prerenal
- Hypovolemia
- GI: decreased intake, vomiting and diarrhea
- Hemorrhage
- Pharmacologic: diuretics
- Third spacing
- 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
- Valvulopathy
- Pharmacologic
- 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
- Microvascular thrombosis
- Hypercalcemia
Intrinsic
- Tubular diseases
- Ischemic acute tubular necrosis
- Caused by more advanced disease due to the prerenal causes
- Ischemic acute tubular necrosis
- Nephrotoxins
- Aminoglycosides, 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
- Rapidly progressive glomerulonephritis
- Small-vessel diseases
- Microvascular thrombosis
- Preeclampsia, HUS, DIC, TTP, vasculitis (PAN, SCD, atheroembolism)
- Malignant hypertension
- Scleroderma
- Renal vein thrombosis
- Microvascular 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
- Anatomic malformations
- Ureter
- Anatomic malformations
- Vesicoureteral reflux (female preponderance)
- Ureterovesical junction obstruction
- Ureterocele
- Retroperitoneal tumor
- Anatomic malformations
- Urethra and bladder outlet
- 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, a-adrenergic antagonists, opioids
- Various locations in GU tract
- Adults
- Urethra and bladder outlet
- BPH
- Cancer of prostate, bladder, cervix, or colon
- Obstructed catheters
- Ureter
- Ureteral calculi, uric acid crystals
- Papillary necrosis
- Tumor: Ureter, uterus, prostate, bladder, colon, rectum; retroperitoneal lymphoma
- Retroperitoneal fibrosis: idiopathic, tuberculosis, sarcoidosis, propranolol
- Stricture: TB, radiation, schistosomiasis, NSAIDs
- Miscellaneous
- Aortic aneurysm
- Pregnant uterus
- IBD
- Renal or ureter trauma
- Urethra and bladder outlet
Evaluation
- Prerenal
- BUN/creatinine ratio > 20
- FeNa <1% ((urine sodium/plasma sodium) / (urine creatinine / serum creatinine))
- < 2% for neonates
- Urine osm >500
- Urine sodium < 20 mEq/L
- Specific gravity > 1.020
- Fractional excretion of urea < 35%
- Microscopic analysis
- Hyaline casts
- Instrinsic
- FeNa >1%
- > 2.5% for neonates
- Urine Osm <350
- Urine sodium > 40 mEq/L
- Specific gravity < 1.020
- Fractional excretion of urea > 50%
- Microscopic analysis
- Acute glomerulonephritis: RBCs, casts
- Acute tubular necrosis: protein, tubular epithelial cells
- FeNa >1%
- Postrenal
- FeNa >1%
- Urine Osm <350
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/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 CIN
- Indicated if hydronephrosis found on ultrasound in order to define the location of obstruction
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)
- Note: Postobstructive diuresis can result in significant volume loss and death
Dialysis
- Indicated for:
- A: Acidosis (severe)
- E: Electrolyte abnormality (e.g. uncontrolled hyperkalemia)
- I: Ingestions (lithium, ASA, methanol, ethylene glycol, theophylline)
- O: Overload (volume) with persistent hypoxia
- U: Uremic pericarditis/encephalopathy/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 SCAPE patient, one may attempt to remove 200-300 cc of blood as a bridge to dialysis[2]
- 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