1. Darrell Gray, II MD Internal Medicine Tenwek Hospital
Acute Renal Failure
Darrell Gray, II MD
Internal Medicine
Tenwek Hospital

2. Case #1
54yo M with AIDS (CD4 of 39) who presents to Tenwek with altered mental status and neurologic deficits. You do a thorough work-up but discover that you need to obtain a CT scan w/ contrast. His baseline creatinine is 1.4, but he returns from the CT scan and now has creatinine of 2.5, with decreased urine output.

3. Case #2
42yo F with no significant PMH presents to CCC c/o 4 days of nausea, vomiting and diarrhea, with fever to 101OF. She has been unable to keep any food down, and very little in the way of liquids. Her son is in primary school and had similar symptoms 1 week ago. Creatinine is Last one was 0.9 about a year ago.

4. Case #3
75yo M with h/o prostate cancer diagnosed in It was metastatic to his ribs at the time, so he was not a candidate for prostatectomy. He has done well since then on hormone therapy in Nairobi, but presents to clinic today c/o abdominal pain and decreased urine output over the last 5 days, as well as irritability and back pain. His creatinine is 8.5, up from a baseline of 1.4.

5. How does it apply to you?
No matter what specialty you go into, you need to understand the kidneys
Surgery – post-operative renal failure
OB – proteinuria, ureteral reflux, pre-eclampsia, pyelo
Peds – ARF, HUS, polycystic kidney dz, minimal change
Radiology – contrast-induced ARF (what creatinine is safe to give contrast?), nephrogenic fibrosing dermopathy, RAS (dx on angiogram or MRI)
ENT – sinus disease and its connection with pulmonary/renal syndromes like Wegener’s
Pathology – identify underlying disease process

6. Definitions Increase in serum creatinine (1mg/dL = 88.4umol/L)
By > 0.5mg/dL in < 2 weeks time
OR, > 20% increase if baseline creatinine is > 2.5mg/dL
Poor urine output
Oliguria ( mL in 24hrs)
Anuria (<100mL in 24hrs)

7. Tell me more about creatinine
An indirect marker of renal function
Is not elevated in early stages of kidney disease
Will not be raised above normal level until 60% loss of kidney function
Should be used to calculate the creatinine clearance for a more direct estimation of renal function
A small, elderly person may have a totally “normal” creatinine but a decreased creatinine clearance
Clearance declines predictably with age
It’s reflective of underlying muscle mass, which is why it can be deceptively “normal” in the elderly

8. Causes of deterioration in renal function
3 major categories:
Pre-renal
Intrinsic renal
Post-renal
Let’s go through each one…

9. Pre-renal Characterized by decreased blood flow to the kidneys
Common causes:
Hypovolemia – ↑ losses, ↓ intake, diuresis
Hypotension – from vasodilation (sepsis, anaphylaxis, BP meds), poor cardiac output (heart failure; can actually be volume overloaded)
ACE inhibitors or ARBs – alterations in efferent arteriolar constriction change renal blood flow (RBF)
NSAIDs – afferent arteriolar constriction ↓ RBF
Renovascular – renal artery stenosis, fibromuscular dysplasia, hepatorenal syndrome

10. Intrinsic Renal Damage to the kidney itself Important causes:
Acute Tubular Necrosis (ATN) – contrast dye, severe hypotension (shock)
Acute Interstitial Nephritis (AIN) – medications (PCNs, sulfa drugs, NSAIDs)
Glomerular disease – numerous causes, including post-strep glomerulonephritis, vasculitis (like Wegeners), lupus nephritis, HIV, and other entities like minimal change disease, FSGS, etc.
Microvascular thrombosis – TTP, HUS, etc.
Embolic – cholesterol emboli (post-cath)
Infectious / depositional – pyelonephritis, nephrocalcinosis

11. Post-renal Obstruction of ureter, bladder outlet, or of urethra
causes backup of urine and hydronephrosis
Common causes:
Bladder neck – BPH, prostate Ca, neurogenic bladder, anticholinergic meds
Ureteral obstruction – lymphadenopathy, malignancy, nephrolithiasis
Tubular – crystal precipitation

13. How do I apply this to my patient?
History and physical
Dehydration, fevers, vomiting or diarrhea, change in urine output, SOB, Edema, recent procedures, medications??
Vital signs, signs of dehydration, skin rash??
Laboratory data
Urinalysis w/ microscopic analysis, creatinine clearance, urine electrolytes, serology (if suspecting autoimmune process or vasculitis)
Imaging
Renal US or CT, bladder scan

14. High Yield Test Interpretation
Urinalysis – a wealth of information!
Components:
Specific gravity – tells you about dilution or concentration of urine (dehydration?)
Protein – points towards damaged machinery (nephrotic syndrome? Lupus? )
Glucose – glucose diuresis?
Ketones – DKA? Not eating/drinking?
Blood / RBCs – kidney stone? Glomerular disease?
Nitrite – UTI?
Leukocyte esterase – UTI?
WBCs – UTI? Pyelo?
Bacteria – UTI?

15. High Yield Test Interpretation
Urine microscopy
Under-appreciated and under-utilized
Can give you incredibly valuable information about underlying processes
Analysis of “casts”
“Sediment”
Bland = no significant casts
Active = red cell casts, white cell casts, “muddy brown” or granular casts
Hyaline casts = often pre-renal, or CKD (“waxy casts”)
Can point towards pyelo (white cell casts), glomerulonephritis (red cell casts)

16. = pre-renal cause (usually)
Casts
Hyaline
= pre-renal cause (usually)
Granular, “muddy brown”
= acute tubular necrosis!

17. High Yield Test Interpretation
Chemistry
BUN : Cr ratio – if >20:1, is strongly suggestive of pre-renal azotemia
Urine sodium and creatinine
Allows you to calculate the fractional excretion of sodium (FeNa)
If < 1%, this is c/w pre-renal cause
If >2%, this is c/w intrinsic renal cause
Urine urea
Useful when patients on diuretics to calculate FeUrea
<35% suggests pre-renal cause

18. High Yield Test Interpretation
Urine eosinophils
Very specific for acute interstitial nephritis
Bladder scan
A rudimentary ultrasound device that gives a mL reading of urinary bladder content
Have patient void, then scan bladder, or insert foley and record “post-void residual” volume if no machine
High post-void residual is suggestive of prostatism or neurogenic bladder
If > mL, data show risk of UTI is increased
If VERY high ( mL), is clearly c/w post-renal cause

19. Treatment by Cause Pre-renal Intrinsic renal Volume expansion
Normal saline, to enhance renal perfusion (or LR)
Follow chemistry (BUN, creatinine), urine output
Hold BP meds to ensure good renal perfusion (within reason)
Intrinsic renal
If AIN, stop potentially offending agent
Or, if active sediment, consider special studies (lupus labs, ANCA for vasculitis, etc)
Supportive care, especially for ATN
Watch lytes, UOP (beware post-ATN diuresis!)
Biopsy as last resort, if indicated

20. Treatment by Cause (cont’d)
Post-renal
Foley placement! (if you can; sometimes it’s not so easy)
Follow BUN, creatinine
Should improve slowly over several days
If not improved, consider abdominal imaging for mass lesion compressing bladder outlet, ureters, etc.

21. Don’t forget to . . . Hold nephrotoxic meds Renally dose the meds
Stop ACE inhibitor / ARB – these can be harmful in acute renal failure
No NSAIDs
Renally dose the meds
Can have catastrophic consequences
Example: morphine has a toxic, renally cleared metabolite, morphine 6-glucoronide; can cause seizures in ARF
Lots of medicines need to be re-dosed (antibiotics like cipro or Keflex or Zosyn or Vanc, zantac, neurontin, atenolol, lovenox, etc.)

22. When to Start Dialysis? At what creatinine should you begin HD?
Trick question; creatinine doesn’t matter
An easy acronym: AEIOU
Acidosis – metabolic
Electrolytes – hyperkalemia
Intoxication – if dialyzable (lithium…)
Overload – pulmonary edema, CHF…
Uremia – pericarditis, “frost,” AMS

23. Questions?

24. Case #1
54yo M with AIDS (CD4 of 39) who presents to Tenwek with altered mental status and neurologic deficits. You do a thorough work-up but discover that you need to obtain a CT scan w/ contrast. His baseline creatinine is 1.4, but he returns from the CT scan and now has creatinine of 2.5, with decreased urine output.

25. Questions Is this renal failure? What type is it most likely to be?
What tests might you order?
How would you manage this?
Answers: Yes, ATN from contrast, urine microscopy to look for “muddy brown” / granular casts, supportive care
Bonus: how might you have prevented this? (intern level)
Pre-hydration and N-acetylcystine (Mucomyst) prophylaxis

26. Case #2
42yo F with no significant PMH presents to CCC c/o 4 days of nausea, vomiting and diarrhea, with fever to 101OF. She has been unable to keep any food down, and very little in the way of liquids. Her son is in primary school and had similar symptoms 1 week ago. Creatinine is Last one was 0.9 about a year ago.

27. Questions Is this renal failure? What type is it most likely to be?
What tests might you order?
How would you manage this?
Answers:
Yes
pre-renal from dehydration / volume depletion
Orthostatic vitals, BUN:Cr ratio, FeNa
Give fluids (saline saline saline!), follow creatinine

28. Case #3
75yo M with h/o prostate cancer diagnosed in It was metastatic to his ribs at the time, so he was not a candidate for prostatectomy. He has done well since then on hormone therapy in Nairobi, but presents to clinic today c/o abdominal pain and decreased urine output over the last 5 days, as well as irritability and back pain. His creatinine is 8.5, up from a baseline of 1.4.

29. Questions Is this renal failure? What type is it most likely to be?
What tests might you order?
How would you manage this?
Answers:
Yes
Post-renal, from prostatic obstruction
Bladder scan or post-void residual; renal ultrasound
Foley placement, give fluids, follow UOP and creatinine