Updated: 1/29/2019

Acute Kidney Injury

Topic
Review Topic
0
0
Questions
3
0
0
Evidence
3
0
0
Snapshot
  • A 54-year-old man is admitted to the cardiac care unit after coronary angiography and revascularization secondary to unstable agina. Approximately 1 week after the procedure he is found to have a "bluish" discoloration of the first and second digits of the foot. Laboratory testing is significant for an elevated serum creatinine. A urinalysis is benign. (Renal atheroemboli)
Introduction
  • Clinical definition
    • acute reduction in glomerular filtration rate (GFR)
      • recall that GFR represents the sum of the filtration rates of nephrons
        • therefore, GFR reflects functioning renal mass
  • Epidemiology
    • risk factors
      • hypertension
      • chronic kidney disease
      • dehydration and volume depletion
      • diabetes
      • chronic liver or lung disease
  • Etiology
    • prerenal causes
      • decreased renal perfusion (e.g., hemorrhage, congestive heart failure, and diuretic use)
    • intrarenal causes
      • acute tubular necrosis
        • ischemia and toxic causes
      • interstitial nephritis
      • glomerulonephritis
      • vasculitis
      • hemolytic uremic syndrome
      • cholesterol emboli
    • postrenal causes 
      • urinary flow obstruction (e.g., benign prostatic hyperplasia and nephrolithiasis)
      • post-operative secondary to bladder manipulation and anesthesia
        • bladder scans should be performed followed by urinary catheterization
  • Pathogenesis
    • based upcome etiology (look at etiology)
  • Prognosis
    • lower rates of recovery in patients > 65 years of age
    • increased risk of end-stage renal disease, chronic kidney disease, and mortality
Presentation
  • Symptoms
    • may be asymptomatic
    • oliguria
    • anuria
    • polyuria
    • confusion
  • Physical exam
    • hypertension
    • edema
    • decreased urine output
Imaging
  • Renal ultrasound
    • indication
      • initial imaging study for assessing acute kidney injury
        • can assess for renal size and hydronephrosis
        • to assess for postrenal obstruction
Studies
  • Labs
    • increase in serum creatinine by ≥ 0.3 mg/dL within 48 hours
    • blood urea nitrogen (BUN):creatinine ratio
    • urinalysis
      • dipstick
        • to assess for protein, glucose, leukocyte esterase, hemoglobin and myoglobin, and specific gravity
      • microscopy
        • for example
          • red dysmorphic cells suggests a glomerular etiology (e.g., glomerulonephritis)
          • muddy brown casts suggests tubular necrosis
          • white blood cell casts suggest pyelonephritis or acute interstitial nephritis
    • fractional excretion of Na+ (FeNa+)
      • if patient is on diuretics use FeUrea
    • urine osmolality and Na+
 
Studies To Assess For Prerenal, Intrarenal, and Postrenal Acute Kidney Injury (AKI)
Studies
Prerenal AKI Intrarenal AKI
Postrenal AKI
Urine osmolality (mOsm/kg)
  • > 500
  • < 350
  • < 350
FeNa+
  • < 1%
  • > 2%
  • < 1% in mild cases
  • > 2% in severe cases
Urine Na+ (mEq/L)
  • < 20
  • > 40
  • > 40
Serum BUN/Cr
  • > 20:1
  • < 15:1
  • Variable
 
Differential
  • Acute gastrointestinal bleeding
  • Rhabdomyolysis
  • Medication-induced impairment of creatinine secretion
    • cimetidine
    • trimethoprim
    • pyrimethamine
Treatment
  • Treatment is dependent on the etiology of AKI and its consequences
    • for example
      • a patient who is hyperkalemic and not responding to medical treatment should be dialyzed
      • a patient with a history of excessive fluid loss (e.g., diarrhea and vomiting) should be given intravenous fluid
Complications
  • Hyperkalemia
  • Metabolic acidosis 
  • Uremic encephalopathy and platelet dysfunction
  • Anemia
  • Chronic kidney disease
 

Please rate topic.

Average 4.1 of 9 Ratings

Thank you for rating! Please vote below and help us build the most advanced adaptive learning platform in medicine

The complexity of this topic is appropriate for?
How important is this topic for board examinations?
How important is this topic for clinical practice?
Questions (3)
Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Volume  
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Urine  
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2
Calculator

Question locked
Sorry, this question is for
PEAK Premium Subscribers only
Upgrade to PEAK

(M2.RL.84) A 63-year-old man undergoes uncomplicated laparascopic cholecystectomy for acute cholecystitis and is admitted to the surgical ward for postoperative management. On postoperative day 1, routine laboratory studies reveal an increase in serum creatinine to 1.46 mg/dL from 0.98 mg/dL before the operation; BUN is 37 mg/dL, increased from 18 mg/dL on prior measurement; K is 4.8 mEq/L and CO2 is 19 mEq/L. The patient has an indwelling urinary catheter in place, draining minimal urine over the last few hours. Which of the following is the most appropriate next step in management? Review Topic

QID: 104531
1

Obtain urinalysis

0%

(0/0)

2

Evaluate urinary catheter for obstruction

0%

(0/0)

3

Administer IV fluid bolus

0%

(0/0)

4

Obtain bilateral renal ultrasonography

0%

(0/0)

5

Initiate emergent hemodialysis

0%

(0/0)

M2

Select Answer to see Preferred Response

PREFERRED RESPONSE 2

(M2.RL.42) A 70-year-old man was diagnosed two days ago with a myocardial infarction and underwent percutaneous coronary intervention to reperfuse his left anterior descending artery. Two days later his creatinine is noted to be elevated (despite being normal the day before) and he complains of a "rash" on his foot (Figure A). Which of the following would most likely be found in laboratory studies? Review Topic

QID: 104489
FIGURES:
1

Hyponatremia

0%

(0/20)

2

Hypokalemia

0%

(0/20)

3

Granular urinary casts

55%

(11/20)

4

Elevated white blood count in urine

5%

(1/20)

5

Eosinophiluria

35%

(7/20)

M2

Select Answer to see Preferred Response

PREFERRED RESPONSE 5
ARTICLES (4)
POSTS (1)
Topic COMMENTS (23)
Private Note