Acute Kidney Injury

[Also see AKI Staging ]


URINALYSIS FINDINGS
RBC Casts Glomerular disease
  • Nephritic syndrome
  • Glomerulonephritis,
  • Ischemia, or
  • Malignant hypertension
WBC Casts Interstitial disease
  • Pyelonephritis
  • AIN
  • Transplant rejection
Fatty casts (“oval fat bodies”)
  • Nephrotic syndrome
Eosinophils Interstitial disease
  • AIN
Granular Casts Tubular disease
  • ATN
Waxy casts
  • Advanced renal disease/chronic renal failure.
Hyaline Casts Acellular
  • Pre- or post-renal
  • Nonspecific, can be a normal finding, often seen in concentrated urine samples.

 

 


 

EVALUATION OF ACUTE RENAL FAILURE
  Pre-renal Intrinsic (Renal) Post-renal
BUN/ Cr Ratio >20 10-20 10-20
Urine SG >1.020 ~1.010 >1.010 early, <1.010 late
Uosm 
(mOsm/ kg)
>350 ~300 >400 early, 300 late
UNa
(mEq/L)
<20 >30 <20 early, >40 late
 
FeNa
(%)
<1 >2-3 <1 early, >3 late
UCr/PCr Ratio ≥40 ≤20 >40 early, <20 late
Urine Micro Normal hyaline casts ATN: hyaline casts, dark granular casts, renal epi cells or casts Normal hyaline, granular casts
 
  Etiology
Hypovolemic (Shock)
Distributive
Cardiogenic

Treatment
Restore circulatory volume
Fluids
Pressors


CHF
– Cardio-renal syndrome

Cirrhosis
– Hepatorenal Syndrome

Volume Depletion
– Bleeding
– Dehydration
 - GI loss
 - Urine volume loss
 - Cutaneous loss

Drugs
ACEI
  -> vasodilation of postglomerular efferent vessels = glomerular
pressure = may cause azotemia

– ? NSAIDs
 -> afferent vasoconstriction = glomerular perfusion

– BP Meds OD (BP)

- Bactrim
 prevents urine Cr excretion = acute Cr

Acute Tubular Necrosis (ATN)
Etiology
  • Ischemic: usually oliguric
    • Trauma
    • Sepsis
  • Toxic: usually not oliguric
    • Contrast agents
    • Myoglobin (rhabdomyolysis)
    • Hemoglobin (hemolysis)
    • Multiple myeloma
    • Ethylene glycol
    • Drugs (Aminoglycosides)
    • Tumor lysis syndrome
    • Ca
    • Phos
ETIOLOGY
Bilateral renal

Tubular crystals
Calyceal stones

Bilateral ureteric
Multiple stones
Surgical complication
Retroperitoneal blood
Papillary necrosis
Infection
Scaring

Urethral
Prostatic hypertrophy
– Prostate Cancer
Neurogenic bladder
Phimosis
Penile meatal stenosis

 

Treatment Options:
 - Foley Cath (Drain only 1L at a time, wait 15 min. then drain more to prevent bladder spasm)

 

GLOMERULAR
(Urine findings: RBC casts, Hematuria, Proteinuria)

NephrItic: NephrItic syndrome = Inflammatory process. Involves glomeruli, leads to hematuria and RBC casts in urine. Associated with azotemia (an elevation of BUN and serum creatinine levels), oliguria, hypertension (due to salt retention), and proteinuria (< 3.5 g/day).
– Postinfectious glomerulonephritis
– IgA nephropathy
– Thin basement membrane disease
– Hereditary nephritis
– Henoch-Schönlein purpura
– Mesangial proliferative glomerulonephritis
– Rapidly progressive glomerulonephritis
– Fibrillary glomerulonephritis
– Membranoproliferative glomerulonephritis
– Vasculitis
   • Mixed cryoglobulinemia
 

NephrOtic: NephrOtic syndrome = massive prOteinuria (> 3.5 g/day, frothy urine), hyperlipidemia, fatty casts, edema.
– Minimal change disease
– Focal glomerulosclerosis
– Mesangial proliferative glomerulonephritis
– Membranous nephropathy
– Diabetic nephropathy
– Preeclampsia
– IgA nephropathy
– Primary amyloidosis
– Light chain deposition disease
– Benign nephrosclerosis
– Postinfectious glomerulonephritis (later stage)

VASCULAR
  • Vascular disease (acute)
    – Vasculitis
        • Wegener's granulomatosis
    – Thromboembolic disease
    – Hemolytic-uremic syndrome/thrombotic thrombocytopenic purpura
    – Malignant hypertension
    – Scleroderma
  • Vascular disease (chronic)
    – Hypertensive nephrosclerosis
    – Renal artery stenosis
    – Atheroembolic disease
  • Microvascular:
    - Microangiopathic Hemoplytic Anemia
    - ARF
    - Small vessel thrombosis or occlusion
    - Hypertension (malignant)
  • Macrovascular:
    – Renal artery stenosis or thrombosis
    – Atheroembolism secondary to:
      • Atrial fibrillation
      • Aortic disease
      • Acute dissection
INTERSTITIAL
  1. Pyelonephritis
  2. Acute Interstitial Nephritis
    • Pathology
      • Immune mediated
    • Etiology
      • Medications
        • Allopurinol (MCC)
        • PCN, sulfa
        • Diuretics
        • NSAIDs
      • Infection
         
    • Clinical Features
      • Fever, rash, eosinophilia
         
    • Urine
      • Pyuria, WBC casts, eosinophilia (Serum and urine)
         
    • Treatment
      • Treat underlying infection
      • Remove offending drug

 


 

History

Lab

Pathophysiology

Treatment

  1. Treatment will depend on presentation and etiology
  2. Acute renal failure
    • Check ABC's, electrolytes (especially K)
    • Correct any prerenal or postrenal factors (see pathophysiology above)
    • If volume depleted, give fluid
    • If obstruction, relieve obstruction
    • If intrinsic renal failure, consider
      • Furosemide 2-6 mg/kg IV (max 400 mg): high doses increases risk of ototoxicity
      • Mannitol 12.5-25 g IV
      • Dopamine 1-3 mcg/kg/min
      • Treat specific etiology, if known
         
    • If hyperkalemia present, consider
      • Insulin 10 U regular IV with 1 amp D50 W IV
      • Calcium gluconate 10 mL of a 10% solution over 2 minutes
      • Kayexalate 1 g/kg
         
    • Consider dialysis

Disposition

  1. All patients should be admitted to hospital
  2. Early nephrology consultation
  3. Consider dialysis