Download Acute Renal Failure - Announcements | Hubert Yeargan

Acute Renal Failure
Darrell Gray, II MD
Internal Medicine
Tenwek Hospital
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.
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 2.0.
Last one was 0.9 about a year ago.
Case #3
75yo M with h/o prostate cancer
diagnosed in 2006. 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.
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
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 (100-400mL in 24hrs)
– Anuria (<100mL in 24hrs)
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
Causes of deterioration in renal
function
3 major categories:
1. Pre-renal
2. Intrinsic renal
3. Post-renal
Let’s go through each one…
Pre-renal
Characterized by decreased blood flow to the
kidneys
Common causes:
1. Hypovolemia – ↑ losses, ↓ intake, diuresis
2. Hypotension – from vasodilation (sepsis,
anaphylaxis, BP meds), poor cardiac output (heart
failure; can actually be volume overloaded)
3. ACE inhibitors or ARBs – alterations in efferent
arteriolar constriction change renal blood flow (RBF)
4. NSAIDs – afferent arteriolar constriction ↓ RBF
5. Renovascular – renal artery stenosis,
fibromuscular dysplasia, hepatorenal syndrome
Intrinsic Renal
Damage to the kidney itself
Important causes:
1. Acute Tubular Necrosis (ATN) – contrast dye,
severe hypotension (shock)
2. Acute Interstitial Nephritis (AIN) – medications
(PCNs, sulfa drugs, NSAIDs)
3. Glomerular disease – numerous causes, including
post-strep glomerulonephritis, vasculitis (like
Wegeners), lupus nephritis, HIV, and other entities
like minimal change disease, FSGS, etc.
4. Microvascular thrombosis – TTP, HUS, etc.
5. Embolic – cholesterol emboli (post-cath)
6. Infectious / depositional – pyelonephritis,
nephrocalcinosis
Post-renal
Obstruction of ureter, bladder outlet, or of
urethra
– causes backup of urine and hydronephrosis
Common causes:
1. Bladder neck – BPH, prostate Ca,
neurogenic bladder, anticholinergic meds
2. Ureteral obstruction – lymphadenopathy,
malignancy, nephrolithiasis
3. Tubular – crystal precipitation
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
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?
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)
Casts
Hyaline
Granular, “muddy brown”
= pre-renal cause (usually)
= acute tubular necrosis!
High Yield Test Interpretation
Chemistry
– BUN : Cr ratio – if >20:1, is strongly suggestive of prerenal 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
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 > 180-250mL, data show risk of UTI is increased
– If VERY high (500-1000mL), is clearly c/w post-renal
cause
Treatment by Cause
Pre-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
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.
Don’t forget to . . .
Hold nephrotoxic 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.)
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
Questions?
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.
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
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 2.0.
Last one was 0.9 about a year ago.
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
Case #3
75yo M with h/o prostate cancer
diagnosed in 2006. 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.
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