Renal Flashcards
Prerenal makes up _________ of acute renal failure cases
40-80%
what are common causes of prerenal AKI?
- Hypovolemia
- Hypotension
- compartment syndrome
- RAS
- decrease in cardiac output (CHF)
Decrease in effective arterial blood volume - Cirrhosis
- CHF
what is the prerenal BUN/Cr ratio:
> 20:1
postrenal makes up _______ of AKI cases
5-10%
Post renal BUN/Cr ratio:
10:1 - 20:1
Post renal AKI is likely due to
an obstruction in lower urinary tract
Intrarenal causes of AKI are
- renal ischemia
- nephrotoxic injury
- intrarenal failure can lead to ischemic injury when MAP < 65 or circulation is interrupted for 30 min
- Acute Tubular Injury (ATI or ATN)
- Ischemia (50%)
- Toxins (35%): aminoglycosides, myoglobin, radiocontrast
agents - Interstitial (10%) (AIN)
- Vascular and Glomerular (5%)
- Renal artery occlusion, cholesterol emboli
- GN, thrombotic microangiopathy
Intrarenal BUN/Cr ratio:
< 10:1
Imaging of kidneys to evaluate for obstruction
(hydronephrosis)
– US Renal or CT A&P
Evaluation of Patients with Acute Increase
in Creatinine:
Urinalysis (structure)
–Macroscopic: protein, blood, WBC’s, RBC’s
–Microscopic: cells, casts, crystals
* Urine chemistries (response to stimuli-function)
– osmolality (ADH action)
–fractional excretion of Na+ (FeNa+) or urea
* Blood chemistries: BUN, creatinine
Causes of Low-Perfusion States
- Hypovolemia
– Blood, GI, Renal, Skin
– 3rd Space (bowel, pancreatitis, edema - Cardiovascular: low cardiac output
– Cardiorenal Syndrome type 1 - Distributive (decreased SVR)
– Sepsis
– Hepatorenal
– Vasodilators - Renal
– Renal artery stenosis
– Drugs (ACE inhibitors, non-steroidal)
– Rapid lowering of BP in severe hypertension - Abdominal Compartment Syndrome
Normally, GFR is
maintained until MAP
is
<80mm
NSAID’s, ACEi/ARB,
vascular disease,
CKD, chronically
elevated BP can
impair GFR autoregulation
GFR falls when MAP
falls below limits of
60
Clinical Diagnosis of ATN/AKI
- History and physical exam: use of
aminoglycosides, radiocontrast, trauma, shock - Urinalysis: mild proteinuria (< 1gram/day), tubular
cells, granular casts - Urine chemistries: osmolality <350 mosm/kg
(inability to concentrate), urine Na+ >40 (inability to
conserve Na+), FeNa+>2% despite hypotension or
hypovolemia