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Renal Failure (Acute Kidney Injury), Emergency Medicine

Basics

Description

- Often asymptomatic and commonly diagnosed with incidental lab findings - Oliguria (<400 mL/d urine production) - Fluid overload: - Dyspnea - Hypertension - Jugular venous distention - Pulmonary and peripheral edema - Ascites - Pericardial and pleural effusion

- Hematologic disorders: - Anemia - Increased bleeding time & platelet dysfunction - Leukocytosis

- HUS or TTP: - UA normal - Anemia - Thrombocytopenia - Schistocytes on blood smear

- Ethylene glycol ingestion: - UA: Calcium oxalate crystals - Anion gap metabolic acidosis - Osmolar gap

- Rhabdomyolysis: - Elevated serum K+, PO4, myoglobin, creatine phosphokinase, uric acid - Decreased serum Ca2+

  • The disorder is now known as acute kidney injury (AKI); the term renal failure is outdated.
  • Changes in glomerular filtration rate (GFR) and urine output (UO) encompassing a spectrum ranging from normal physiologic response to end-stage renal disease (ESRD) and measured by accumulation of nitrogenous by-products.
  • Defined by the RIFLE criteria:3 stages of renal injury:Risk: Increased creatinine (Cr) 1.5 or GFR decrease >25%, UO <0.5 mL/kg/h >6 hInjury: Increased Cr 2 or GFR decrease >50%, UO <0.5 mL/kg/h >12 hFailure: Increased Cr 3 or GFR decrease >75% or Cr ≥4 mg/dL (acute rise of ≥0.5 mg/dL), UO <0.3 mL/kg/h 24 h or anuria 12 h2 stages of outcome:Loss: Loss of renal function >4 wkESRD: Loss of renal function >3 mo
  • The most severe marker defines stage.
  • AKI based upon changes within last 48h; however, must often base on most recent data.
  • Higher RIFLE stages correlate with higher 1 and 6 mo mortality rates for hospitalized patients.

Etiology

  • Prerenal AKI:Caused by renal hypoperfusionRenal tissue remains normal unless severe/prolonged hypoperfusion.
  • Intrarenal AKI:Caused by diseases of the renal parenchyma
  • Iatrogenic AKI causes include:Aminoglycoside antibioticsRadiocontrast material administrationNSAIDsACE inhibitorsAngiotensin receptor blockers
  • Postrenal AKI:Due to urinary tract obstruction (e.g., prostatic hypertrophy, prostatitis)

Diagnosis

Signs and Symptoms

Acute Kidney Injury

  • Often asymptomatic and commonly diagnosed with incidental lab findings
  • Oliguria (<400 mL/d urine production)
  • Fluid overload:DyspneaHypertensionJugular venous distentionPulmonary and peripheral edemaAscitesPericardial and pleural effusion
  • Nausea/vomiting
  • Pruritus/skin changes
  • Confusion/mental status changes

Prerenal AKI

  • Absolute or relative volume deficit
  • Dry mucous membranes
  • Hypotension
  • Tachycardia
  • Low cardiac output
  • Congestive heart failure
  • Systemic vasodilation (e.g., sepsis, anaphylaxis)

Intrinsic AKI

  • Allergic Interstitial Nephritis:FeverRashRecent myocardial infarction
  • Renal vein thrombosis:Nephrotic syndromeCan be associated with pulmonary embolusFlank or abdominal pain
  • Glomerulonephritis, vasculitis
  • Hemolytic uremic syndrome (HUS)
  • Thrombotic thrombocytopenic purpura (TTP):Mild elevation of BUN/CrFeverAltered mental statusAnemia & thrombocytopeniaNeurologic: Coma, seizure, headache, altered mental status
  • Allergic interstitial nephritis fever:

Postrenal AKI

  • Abdominal or flank pain
  • Distended bladder
  • Oliguria or anuria

Complications of AKI

  • Uremic syndrome:Altered mental statusAsterixisReflex abnormalitiesFocal neurologic abnormalitySeizuresRestless leg syndromePericarditisPericardial effusion/cardiac tamponadeIleusPlatelet dysfunctionPruritus
  • Hematologic disorders:AnemiaIncreased bleeding time & platelet dysfunctionLeukocytosis

History

  • Prior history of AKI
  • Medication history including nephrotoxins
  • Weight change

Physical Exam

  • Mental status changes/confusion
  • Eyes: Fundoscopy
  • CV exam: Jugular venous distention, S3
  • Lungs: Rales, crackles
  • Abdomen: Flank tenderness, palpable kidneys
  • Edema
  • Skin changes
  • Prone to prerenal AKI
  • Cr will vary by body mass index, so a "normal " range in elderly may represent an elevation.
  • Increased risk of contrast- and medication-induced AKI
  • Prerenal AKI a concern in neonates
  • Anatomic abnormalities
  • Intrinsic renal azotemia
  • Pre-eclampsia/eclampsia
  • Ischemia: Postpartum hemorrhage, abruptio placentae, amniotic fluid embolus
  • Direct toxicity of illegal abortifacients
  • Postpartum TTP, HUS

Essential Workup

  • Electrolytes including Ca, Mg, PO4
  • BUN/Cr
  • Urinalysis (UA):Centrifuged specimen helps to distinguish different etiologies of AKI.Exam for casts, blood, WBCs, and crystals
  • Fractional excretion (FE) of Na and/or urea
  • CBC: Anemia common with chronic disease
  • Postvoid residual volume (>100 mL suggests obstruction) OR
  • Ultrasound to rule out obstruction " especially in older men (e.g., prostatic hypertrophy, prostatitis)
  • ECG

Diagnosis Tests & Interpretation

Lab

Prerenal

UA:

  • Specific gravity >1.018
  • Osmolality >500 mmol/kg
  • Sodium <10 mmol/L
  • Hyaline casts
  • BUN/Cr ratio >20
  • FENA <1%
  • Rapid recovery of renal function when renal perfusion normalized

Intrarenal

  • BUN/Cr ratio <10 " 15
  • FENA >2%
  • Glomerulonephritis, vasculitis:UA with red cell or granular castsComplement and autoimmune antibodies
  • HUS or TTP:UA normalAnemiaThrombocytopeniaSchistocytes on blood smear
  • Nephrotoxic acute tubular necrosis (ATN):UA:Brown granular or epithelial cell castsSpecific gravity = 1.010Urine osmolality <350 mmol/kgUrine Na >20 mmol/L
  • Ethylene glycol ingestion:UA: Calcium oxalate crystalsAnion gap metabolic acidosisOsmolar gap
  • Rhabdomyolysis:Elevated serum K+, PO4, myoglobin, creatine phosphokinase, uric acidDecreased serum Ca2+
  • Tubulointerstitial disease
  • Allergic interstitial nephritis:UA with WBC casts, WBCs, RBCs, and proteinuriaPeripheral eosinophilia

Postrenal

UA:

  • Usually normal
  • May have some hematuria but no casts or protein
  • FENA often >4%
  • Urine osmolality usually <350 mmol/kg

Imaging

  • US:98% sensitive for excluding obstruction
  • Helical CT scan:Without contrast sensitive for obstructionMay detect intrarenal changes
  • Duplex scan for:Renal artery or vein thrombosis
  • Renal arteriogram:Definitive diagnosis of renal artery thrombosis
  • Inferior vena cava and renal vessel venogram for renal vein thrombosis
  • IV pyelogram

Diagnostic Procedures/Surgery

ECG:

  • Hypertension secondary to volume overload may cause ischemia.
  • Sensitive for significant, acute electrolyte changes

Treatment

Pre-Hospital

  • Airway, breathing, and circulation (ABCs):Supplemental oxygen for hypoxia
  • IV NS for volume depletion

Initial Stabilization/Therapy

  • ABCs:
  • Supplemental oxygen for hypoxia
  • IV NS for volume depletion
  • Correct electrolyte disturbances
  • Indications for emergent dialysis:Intractable hypertensionIntractable volume overloadUremic encephalopathy, bleeding, or pericarditisBUN >100 mg/dLIntractable metabolic acidosis (pH <7.2)
  • Avoid nephrotoxic drugs.
  • Monitor UO.

Ed Treatment/Procedures

Prerenal AKI

  • Treat hypoperfusion with IV NS
  • Packed RBC for blood loss or anemia after lack of response after 2 boluses
  • Invasive cardiac monitoring if unable to assess cardiac failure vs. hypovolemia
  • Response to NS good indicator of the degree to which hypovolemia is a factor

Administer NS fluid challenge cautiously to avoid fluid overload in liver failure with ascites.

Intrarenal AKI

  • Glomerulonephritis:Glucocorticoids or plasma exchange
  • ATN:
  • Hyponatremia: Free water restriction
  • Hyperkalemia:Sodium polystyrene sulfonate (SPS) or calcium polystyrene sulfonate (CPS) for asymptomatic patient with K+ >5.5 mEq/LFor K+ >6.5 mEq/L or ECG abnormalities consistent with hyperkalemia:Albuterol via nebulizerDextrose and insulinFurosemide if patient not anuricCalcium stabilizes myocardium in severe hyperkalemiaCalcium gluconate for awake patientCalcium chloride for patient without pulseDialysis for intractable hyperkalemia
  • Metabolic acidosis:Consider sodium bicarbonate for pH <7.2 or HCO3 <15 mEq/L in chronic diseaseHyperphosphatemia:Calcium carbonateAluminum hydroxideMyoglobinuria " aggressive fluid resuscitation with NS
  • Calcium is only indicated by ECG for widened PR, QT, or QRS intervals. Peaked T waves alone are not an indication.
  • Sodium bicarbonate is a considerable sodium load; use caution in anuric/oliguric patients.

Medication

  • Albuterol: 10 " 20 mg via nebulizer
  • Aluminum hydroxide (amphojel): 0.5 " 1.5 g PO
  • Calcium carbonate (Os-Cal): 0.250 " 3 g PO
  • Calcium gluconate: 10 mL of 10% solution over 5 min IV (may repeat q5min)
  • Calcium chloride: 10 mL of 10% solution
  • Dextrose: D50W 1 amp (50 mL or 25 g) (peds: D25W 2 mL/kg) IV
  • Furosemide: 20 " 400 mg IV push
  • Insulin: 0.1 U/kg regular IV with dextrose (decrease dose by 50% for severe renal and/or liver disease)
  • Sodium bicarbonate: 1 " 2 mEq/kg IV
  • SPS (Kayexalate) or CPS: 1 g/kg up to 15 " 60 g PO or 30 " 50 g retention enema in sorbitol q6h

Diuretics (in the absence of volume overload) and dopamine are not recommended in AKI.

Follow-Up

Disposition

Admission Criteria

  • New-onset AKI
  • Hyperkalemia/significant electrolyte abnormalities
  • Fluid overload with hypoxia/congestive heart failure
  • Uremia
  • Altered mental status

Discharge Criteria

  • Stable
  • Normal electrolytes

Issues for Referral

Refer to primary physician for progressive AKI in an otherwise stable patient.

Pearls and Pitfalls

  • Insulin dose for hyperkalemia should be reduced for significant liver or renal disease so as to avoid hypoglycemia.
  • NSAIDs to be avoided with any degree of AKI
  • SPS has a considerable sodium load; CPS is preferred when volume overload is a concern.
  • Avoid contrast if possible in AKI, as it may worsen renal function.

Additional Reading

  • Andreoli S. Acute kidney injury in children. Pediatr Nephrol. 2009;24:253 " 263.
  • Kellum JA. Acute kidney injury. Crit Care Med. 2008;36(suppl):S141 " S145.
  • Rahman M, Shad F, Smith MC. Acute kidney injury: A guide to diagnosis and management. Amer Fam Physician. 2012;86(7):631 " 639.

See Also (Topic, Algorithm, Electronic Media Element)

Codes

ICD9

  • 584.5 Acute kidney failure with lesion of tubular necrosis
  • 584.9 Acute kidney failure, unspecified
  • 997.5 Urinary complications, not elsewhere classified
  • 584.8 Acute kidney failure with other specified pathological lesion in kidney
  • 283.11 Hemolytic-uremic syndrome
  • 585.6 End stage renal disease

ICD10

  • N17.0 Acute kidney failure with tubular necrosis
  • N17.9 Acute kidney failure, unspecified
  • N99.0 Postprocedural (acute) (chronic) kidney failure
  • N17.8 Other acute kidney failure
  • D59.3 Hemolytic-uremic syndrome
  • N18.6 End stage renal disease

SNOMED

  • 14669001 Acute renal failure syndrome (disorder)
  • 35455006 Acute tubular necrosis (disorder)
  • 36225005 Acute renal failure due to procedure
  • 429489008 Acute renal failure due to obstruction
  • 111407006 Hemolytic uremic syndrome (disorder)
  • 301814009 Post-renal renal failure
  • 46177005 End stage renal disease (disorder)