1. Edward L. Barnes, MD Chief Resident Conference July 5, 2012
Acute Kidney Injury
Edward L. Barnes, MD
Chief Resident Conference
July 5, 2012

2. Outline for Today Workup Pre-Renal Intrinsic Post-Renal
Tubulointerstitial Disease
Glomerular Disease
Post-Renal
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3. Initial Work Up Attempt to define the problem
What is the reason for the Acute Kidney Injury?
Typically broken down into where the etiology is occurring
Pre-Renal
Intrinsic Disease
Post-Renal
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4. Acute Kidney Injury Which situation is worse
Creatinine 1.1 1.6
Creatinine 2.8  3.3
Is a Cr of 1 always normal?
80 yo woman, frail with BMI 18
25 yo man, muscular with BMI 25
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5. Serum Creatinine vs. GFR
Remember this is a non-linear relationship
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6. Case #1
A 65-year-old man is admitted to the hospital because of fever and dysuria. Laboratory studies show a leukocyte count of 12,000/µL, a blood urea nitrogen level of 24 mg/dL, a serum creatinine concentration of 1.4 mg/dL, and pyuria. Empiric treatment with trimethoprim-sulfamethoxazole is started. Three days later, the pyuria and fever have resolved. The leukocyte count is 10,000/µL, blood urea nitrogen level is 24, and serum creatinine is 1.8 mg/dL. Urinalysis shows no leukocytes, casts or crystals.
What are some potential causes of the increase in Cr from 1.4 to 1.8?
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7. Case #1
Which of the following is the most likely explanation for the rise in serum creatinine from 1.4 mg/dL to 1.8 mg/dL?
Acute interstitial nephritis
Acute pyelonephritis
Acute tubular necrosis
Obstructive uropathy
Drug effect with reduced creatinine excretion
Many medications can alter the kidney’s excretion of creatinine itself WITHOUT causing damage or decrease in kidney function. Cimetidine can do this as well. Part of defining the problem is ensuring that it’s really a problem.
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8. Case #2 What else do you want to know?
A previously healthy 74-year-old man is hospitalized with cough and chest pain. On physical examination, the blood pressure is 148/92 mm Hg, heart rate is 75/min, respiration rate is 18/min, and temperature is 37.8 °C (100 °F). The left lower lung field has scattered basilar crackles. The hematocrit is 34% and leukocytosis is present. The serum creatinine concentration is 2.3 mg/dL. Urinalysis shows a pH of 6.0, 1+ proteinuria, and no hematuria or ketonuria.
What else do you want to know?
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9. Case #2
Which of the following is most useful in distinguishing acute from chronic renal failure in this patient?
A. A previous hematocrit
B. Previous serum creatinine concentration
C. Blood urea nitrogen to creatinine ratio D. Microscopic urinalysis E. Renal ultrasonography
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10. Acute Kidney Injury Step One: Define the Problem (History)
Prior Creatinine Measurements
All Medications, New Medications, Herbal Medications, Illicit Drug use
Recent contrast exposure
May have to explicitly ask about imaging
Volume loss, dehydration, decreased po intake
Flank Pain
Hematuria, Dysuria, Anuria
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11. Acute Kidney Injury Step Two: Physical Exam Evaluate for dehydration
Flank Pain
Edema
Tender, lower abdominal mass
Rash
Sinus abnormalities
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12. Acute Kidney Injury Step Three: Labs and Diagnostic Studies
Urinalysis: the liquid kidney biopsy
Urine “Lytes”
Sodium
Creatinine
Urea (if on diuretics)
Serum Chemistry
Fractional Excretion of Na (FENa)
Urine Na x Plasma Cr
Urine Cr x Plasma Na
Renal US allows you to evaluate for obstruction, as indicated by hydronephrosis
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13. Acute Kidney Injury Fractional Excretion of Na (FeNa)
Urine Na x Plasma Cr
Urine Cr x Plasma Na
FeNa <1 = Pre-Renal
FeNa >2 = Intrinsic
FeUrea <35% = Pre-Renal
FeUrea >35% = Intrinsic Disease
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14. Acute Kidney Injury Other Labs to consider:
Urine Protein/Creatinine Ratio
ANA, ANCA
HIV, RPR
Hepatitis Panel
Complement Levels: C3, C4
SPEP/UPEP
Hansel Stain
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15. Urinalysis red - myoglobin / hemoglobin
brown - can be same as above, or ATN
White - infection or chyle
Green - medication induced
Black - alkaptonuria
Other colors - probably a metabolic disorder
low - dilute ~ excess water intake or DI
high - dehydrated with appropriate response or hyperosmolars (contrast, mannitol)
pH- normal is acidic. alkaline ~ RTA (if acidosis is present), or infection with Ureaplasma, proteus or pseudomonas (split urease)
“Pro” = albumin. no other proteins are measured on a UA. So you can have “negative protein” with multiple myeloma
Glucose - threshold of serum 180 before it appears in the urine (or myeloma and faulty membrane)
Ketones - DKA, alcoholism, starvation
LE / Nitrites ~ infection. Negative for both of these makes a UTI fairly unlikely. LE = WBCs, so it can occur in AIN as well.
Nitrites ~ ecoli, proteus, pseudomonas, klebsiella
Bilirubin should never be in the urine of a healthy person. suggests liver failure / biliary obstruction
Urobilinogen ~ hemolysis and hepatic necrosis (not obstruction)
Too many squams? View with caution.
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16. Color Rhabdomyolysis (myoglobinuria) Alkaptonuria
Alkaptonuria: Urine turns a dark brown or black color when exposed to air
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17. Color
Pseudomonas
Lee J. N Engl J Med 2007;357:e14.
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18. Urinalysis: Protein Only accounts for albumin
You may need to test for other proteins
Bence Jones protein in suspected Light Chain Disease or Multiple Myeloma
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19. Looking at the Urine
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20. Red Blood Cell Casts Looking at the Urine Indicates glomerulonephritis
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21. Dysmorphic Red Blood Cells
Looking at the Urine
Dysmorphic Red Blood Cells
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22. Calcium Oxalate Crystals
Looking at the Urine
Uric Acid Crystals
Calcium Oxalate Crystals
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23. Putting it All Together
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24. Case #3
48 yo woman with PMH significant for HTN (treated with Lisinopril) presents with a chief complaint of vomiting and weakness. Baseline Cr is 0.8. Laboratory Studies are shown below: Na 140 Urine Na 7 K 3.8 Urine Cr 65 BUN 38 Cr 1.6 What type of Acute Kidney injury does this patient have?
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25. Case #3
FeNa = 0.12%
Pre-Renal
Acute Kidney Injury
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26. Pre-Renal Acute Kidney Injury
Causes:
Dehydration
Shock
Acute Volume Loss (bleeding)
Abdominal Compartment Syndrome
Decompensated Heart Failure
End Stage Liver Disease (Hepatorenal syndrome)
Renal Artery Thrombosis
Anything that decreases blood flow to the kidney
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27. Urinalysis Urinalysis should be relatively normal
If patient is dehydrated, you may see Hyaline Casts
Urine Sediment will otherwise be bland
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28. Treatment Correct the underlying perfusion abnormality if possible
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29. How would you treat this patient?
Case #3
48 yo woman with PMH significant for HTN (treated with Lisinopril) presents with a chief complaint of vomiting and weakness. Baseline Cr is 0.8. Laboratory Studies are shown below:
Na Urine Na 7
K Urine Cr 65
BUN Urine Urea 135
Cr 1.6
How would you treat this patient?
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30. Pre-Renal Acute Kidney Injury
48 yo woman with PMH significant for HTN presenting with:
Severe abdominal pain
Guarding on exam
Bladder pressure as measured by foley catheter is 34 mmHg
Cr is 1.9 (baseline 0.8)
Urine sediment is bland
What is the diagnosis?
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31. Pre-Renal Acute Kidney Injury
48 yo woman with PMH significant for HTN presenting with:
Altered mental status
Hypotension
Blood cultures positive for Pseudomonas aeruginosa
Cr is 2.7 (baseline 0.8)
Urine sediment is bland
What is the etiology of the acute kidney injury?
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32. Pre-Renal Acute Kidney Injury
48 yo woman with PMH significant for HTN, cirrhosis secondary to HCV presenting with:
Altered mental status
Hypotension
Anasarca
FeNa 0% (very low), Urine Na <5
Cr is 2.7 (baseline 0.8)
Urine sediment is bland
What is the etiology of the acute kidney injury?
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33. How would you treat this patient?
Case #4
48 yo woman with PMH significant for HTN (treated with Lisinopril and HCTZ) presents with a chief complaint of vomiting and weakness. Baseline Cr is 0.8. Laboratory Studies are shown below:
Na Urine Na 85
K Urine Cr 65
BUN Urine Urea 135
Cr 2.6
How would you treat this patient?
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34. Pre-Renal Acute Kidney Injury
Case #4
This patient is on chronic diuretic therapy, thus you must calculate the FeUrea:
Urine Urea x Plasma Cr
Urine Cr x Plasma Urea
FeUrea= 14.21%
Pre-Renal Acute Kidney Injury
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35. What is the etiology of this patient’s Acute Kidney Injury?
Case #5
48 yo woman with PMH significant for HTN (treated with Lisinopril and HCTZ) presents with a chief complaint of vomiting and weakness. Baseline Cr is 0.8. Laboratory Studies are shown below:
Na Urine Na 65
K Urine Cr 45
BUN Urine Urea 265
Cr 2.5
What is the etiology of this patient’s Acute Kidney Injury?
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36. Intrinsic Acute Kidney Injury
Etiology of Intrinsic AKI:
Acute Tubular Necrosis (ATN)
Contrast Induced Nephropathy (CIN)
Rhabdomyolysis (Pigment Induced Nephropathy)
Acute Interstitial Nephritis (AIN)
Glomerulonephritis (multiple etiologies)
Cholesterol Emboli
Thrombotic Microangiopathy
and more…
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37. What do you want to do next?
Case
23 yo man with no PMH, but was recently treated for Strep Throat presents with fatigue and overall feeling poorly. Physical Exam is normal.
Cr FeNa 2.3%
What do you want to do next?
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38. Post-Streptococcal Glomerulonephritis
Case Continued
Post-Strep Glomerulonephritis
What is your diagnosis?
Post-Streptococcal Glomerulonephritis
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39. Glomerulonephritis
Defined by Red Blood Cell Casts in the urine sediment
Multiple etiologies of Glomerulonephritis exist, will be covered in detail elsewhere
Associations to remember:
Most Common: IgA Nephropathy
GN + Hemoptysis: ANCA or anti-GBM (Goodpasture’s Syndrome)
GN + Purpura: Think Vasculitis
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40. Case #6
54 yo man with PMH significant for HTN, Hyperlipidemia, presented to the MICU after being found down and resuscitated for approximately 20 minutes. After 3 days, patient has now been extubated and is doing well, however his Creatinine continues to rise. Creatinine on admission was 1.2, now 3.5 this morning. Cr 3.5 FeNa 3.5%
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41. What is your diagnosis? Case #6 Continued You spin his urine and find…
Acute Tubular Necrosis, Muddy Brown Casts
Esson ML, Shrier RW. Diagnosis and Treatment of Acute Tubular Necrosis. Ann Intern Med. 5 November 2002;137(9):
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42. Acute Tubular Necrosis
Risk Factors:
Prolonged Hypotension
Nephrotoxic Agents
Classic description: “muddy brown casts”
Treatment
Remove inciting etiology (resuscitate, remove suspected medication)
If patient improves, suspect post ATN diuresis to occur (may take up to 1-3 weeks)
Some patients may progress to End Stage Renal Disease
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43. What is the suspected diagnosis?
Case #7
68 yo man with PMH significant for HTN and Hyperlipidemia, admitted for a STEMI. Patient received PCI with stent to the Right Coronary Artery. Patient is doing well, but on day 3 of admission, Creatinine is noted to be elevated at Baseline Creatinine was 0.9. No new medications other than Plavix.
FeNa: 2.5%
What is the suspected diagnosis?
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44. Contrast Induced Nephropathy
At Risk Patients:
Diabetes Mellitus
Chronic Kidney Disease
Occurs in approximately 3% of the population
Typically occurs hours following contrast administration
Typically transient, improving over 1-3 weeks; however there is potential for progression to ESRD
Prevention
Hydration
Hold nephrotoxic agents (NSAIDs)
Treatment
supportive
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45. Case #8
68 yo man with PMH significant for HTN and Hyperlipidemia, admitted for a STEMI. Patient received PCI with stent to the Right Coronary Artery. Patient is doing well, however overnight, Cr increases from baseline (0.9) to 2.1 and the patient develops a new rash. No new medications other than Plavix.
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46. Case #8 What is this “rash”? Livedo Reticularis What is the diagnosis?
Cholesterol emboli syndrome
Livedo Reticularis
What is the diagnosis?
Cholesterol Emboli Syndrome
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47. Case #9
22 yo man with no PMH presents with nausea, vomiting, and fatigue. The patient is a member of the wrestling team at UNC. Denies taking any new medications or supplements. Cr 2.9 (baseline 0.8) FeNa 2.6% Urine dipstick performed in your office indicates 3+ blood. You examine the urine, and the sediment is bland, no RBC or WBC are seen. What other labs would you want to know? What is the diagnosis?
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48. What is the next test that you want to order?
Case #10
78 yo man with PMH significant for HTN, and Benign Prostatic Hypertrophy. He has been taking over the counter allergy medications. Over the past 24 hours he has developed lower abdominal pain, decreased urine output. On laboratory studies:
Cr 2.3 (baseline 1.0) FeNa 2.5%
Urine Sediment is bland
What is the next test that you want to order?
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49. Presence of Hydronephrosis indicates post-renal Acute Kidney Injury
Renal Ultrasound
Presence of Hydronephrosis indicates post-renal Acute Kidney Injury
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50. Post-Renal Acute Kidney Injury
Hydronephrosis and Acute Kidney Injury is an Emergency
You must relieve the obstruction
Foley Catheter
Nephrostomy Tubes
Next you must identify the cause of the obstruction
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51. The End
Acute Kidney Injury
Pre-Renal
Intrinsic
Post-Renal
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