Acute Kidney Injury And Renal Failure Flashcards
What is a AKI?
Caused by progressive azotemia (abnormally high levels of nitrogen-containing compounds in blood)
- kidney is injured and cant get rid of the nitrogen waste properly
Occurs over a few days
All AKI shows oligouria/anuria
- *usually shows BUN:creatinine increases**
- normal ratio is 5-20:1
3 main types
- prerenal
- intrinsic renal
- postrenal
** can be compound (multiple causes) or just one)
Prerenal causes
Almost always caused by hypovolemia in some way shape or form
- sepsis
- diabetes mellitus
- GI losses
- Renal losses
- hemorrhages
the one exception is severe systolic HF which produces cardiorenal syndrome
results in decreased GFR rates, activations of RAAS and elevated BUN:creatinine ratio of 20
*urine levels of sodium will be <20 mEq/L, urine will be >500 oSmoles, and FENa = <1%. (Because the kidney has less filtrate and chronic stimulation of the RAAS system
Intrinsic renal causes
Most commonly caused by acute tubular necrosis (ATN)
- death and physiological damage caused by ischemia from a prerenal AKI
- most common damaged cells = PCT/TAL cells
Additional causes:
1) nephrotoxicity via:
- contrast
- Aminoglycosides
- cisplatin
- heavy metals
- rhabdomyolysis (myoglobin)
- poisons
- hemolytic anemia (hemaglobinuria)
Shows BUN:creatinine ratio of less <20
- high FENa = 2%
- high urine Na+ > 40 mEq/L
- urine osmolality <350 mEq/L
Postrenal causes
Is always a blockage of some sort
- kidney stones
- prostate hypertrophy/cancer
- overplayed bladder
#1 is always prostate hypertrophy in men
Variable lab values**
- but urine will always be <350 osmolarity
Complications of AKI
Massive amounts of different complications Includes:
1) metabolic
- hyperkalemia, hyponatremia, hypocalcemia, hyperphosphatemia, hyperuricemia, metabolic acidosis
2) cardiovascular
- pericardial effusion, HTN, MIs, arrhythmias, pulmonary edema
3) GI
- N/V, malnutrition, GI hemorrhages
4) CNS
- AMS, asterixis, seizures
5) infectiosn
- pneumonia, sepsis
Prerenal lab values
BUN:creatine ratio is almost always >20
- if GI bleed present also = > 40
FRNa (fractional excretion of sodium) will be very low <1%
- also low urine sodium <20 mEq/L
- ** this is because the kidney is trying to conserve sodium to retain water
What is the most common cause of renal AKI?
Acute tubular necrosis
- also is 90% the cause of renal failure
- almost always caused by ischemia or shock of some sort (usually trauma or infectious shock/sepsis)
Intrinsic renal AKI lab values
FENa = high (>1%)
- high urine sodium concentration also (kidney isnt working)
- *however if the patient is taking diuretics (especially loop) the FENa looks normal or low.
Urine sodium = > 40
BUN:creatinine ratio is low <20
Very high water in urine
**FEurea will be high and 100% needs to be monitored if patient is taking diuretics
What kind of casts in urine would signal a pre renal or post renal cause of AKI?
Hyaline casts
** granular or RBC cell casts = intrinsic renal cause
Children vs children renal failure causes
Adults
- 90% ATN
- 10% other
Children
- 50% ATN
- 50% other
Rhabdomyolysis and AKI
Common cause of AKI that causes ATN.
- hyperthermia
- crush injuries
- extreme working out
PSGN lab values
Intrinsic cause of ATI:
- FENa is high
- BUN:creatinine ratio will be low
- Urine sodium will be high
shows red blood cell casts and RBCs in the urine
Treatment = antibiotics for past infection (if you still think its around). give fluids and electrolytes and HTN treatment short term
Acute interstital nephritis
- *WBC casts with eosinophils and direct RBCs and WBCs will be in the urine**
- **if it was pylonephritis/ infectious it would show NO eosinophils in the urine
Is believed to be type 1 or type 4 hypersensitivity reaction to some drugs (such as NSAIDs, PPIs, rifampin, penicillins and sulfa drugs are MOST common)**
- can also be caused by systemic infections, autoimmune reactions (SLE and sarcoidosis are most common) coagulopathies, and mycoplasma infections as well as pyelonephritis and diabetes mellitus
Intrinsic cause of AKI:
- BUN: creatinine ratio is low
- **however creatinine is high
- FENa = 2.5% roughly with high sodium in urine >40 mEq/L
Symptoms:
- fever
- rash
- hematuria
- Pyuria
- costovertebral tenderness
- **eosinophils in urine and eosinophilia = drug-induced AIN needs to be #1
Treatment of AIN induced medication
Usually self-limiting and just stop the meds and symptomatically treat via palliative care
Contrast induced nephropathy
giving IV contrast can cause nephropathy, however it is less dangerous as literature implies
Risk factors:
- diabetes
- multiple myeloma
- hypovolemia
- > 60 yrs
- high loads of contrast
- previous renal injuries/insufficiency **most important
treatment = fluids and monitor
- *N-Acetyl-cystine before IV contrast tanks the risk % of getting this
