9/16- Acute Kidney Injury (AKD) Flashcards
Knowing a pt’s GFR is how we clinically estimate kidney fct. The serum creatinine is an easy marker to use since it is easy to measure in the blood. However, which of the following properties make the serum creatinine an imperfect marker?
A. Not free filtered by glomerulus
B. Secreted by tubules (overestimates GFR)
C.
Knowing a pt’s GFR is how we clinically estimate kidney fct. The serum creatinine is an easy marker to use since it is easy to measure in the blood. However, which of the following properties make the serum creatinine an imperfect marker?
A. Not free filtered by glomerulus
B. Secreted by tubules (overestimates GFR)
C.
What is acute kidney disease (AKD)?
- Acute damage to kidney
- Syndrome; can be caused by many things
- Usually reversible, but residual kidney damage is possible
- Chronic Kidney Damage (CKD) may result years after AKD
- Diagnosis of AKD hampered by its relative asymptomatic nature in early stages
What are some possible causes of AKD?
- Urinalysis
- BUN
- Creatinine
Damage may or may not be present (can have either damage or functional changes and then gain the other)
- Damage without functional change = AKD
- Damage with functional change = AKD or CKD
What are clinical indicators of kidney injury?
- Urine output
- Blood chemistry
- Estimate of glomerular filtration
- History comaptible with kidney injury
What is the specific definition of AKD?
ONE OF:
- Rise in serum creatinine > 0.3 mg/dL within 48 hours
- Rise in serum creatinine > 1.5x the baseline within previous 7 days
- Urine volume < 0.5 mL/kg/hr for 6 hrs
Creatinine estimates ___
Creatinine estimates GFR
Damage to any part of the nephron results in what?
How does this affect GFR?
Decreased reabsorption
- Tubulo-glomerular feedback ensures that GFR falls to match decreased reabosrption
(Thus decrease in GFR indicates alteration or damage of renal mechanisms)
Case)
- 35 yo pregnant woman found to have placenta percreta
- Emergency C-section and hysterectomy
- 1 wk chronic abdominal pain worse than expected post op
- Sudden drop BP 70/P, altered mental status, O2 desaturation, WBC increases to 17,000, urine output stops, Creat increases form 0.6 to 1.3 mg/dL (1.3 is in normal range!), intubated
Had ruptured colon, fluid challenge, emergent surgical repair, recovery in 24 hours
Diagnostic approach to analyzing AKD: what is the renal rule of 3 (broad overview)?
Acute kidney disease (AKD):
1. Prerenal- not the kidney’s fault
2. Intrinsic/Renal- parenchymal disease of any sort
- Glomeruli
- Tubules
- Space in between glomeruli/tubules
3. Postrenal- urinary obstruction at any level
What is pre-renal AKD? Processes occurring?
In pre-renal states, kidneys are not initially damaged, but can progress to AKD
Pre-renal states without AKD:
- Intense volume reabsorption
- Fall in capillary pressure, decreased glomerular surface area
- Increased reabsorption by tubules
- RAS, Aldo, ADH, SNS activated
- Kidney still anatomically normal (can reverse rapidly with correction)
- If toxin in blood, kidney will inadvertently concentrate it in the tubules; possibly -> renal damage/injury
Pre-renal state, now AKD:
- All of the above physiological changes
- Kidney damage identifiable
- Commonly acute tubular necrosis develops
What are some pre-renal etiologies?
Kidneys function as if pt is hypovolemic
Decreased vascular volume:
- Bleeding
- GI losses
- Insensible losses
- Diarrhea
- Diuresis
Ineffective Circulating Volume
- Sepsis
- Heart Failure
- Cardiogenic shock
- Liver failure
- Pre-eclampsia
COMMON CAUSES of PRE-RENAL STATE
- Hepatorenal syndrome
- Renal Artery stenosis
- Congestive heart failure
- NSAIDS
KEY:
- A pre-renal cause of AKD does not mean volume contraction…
- You may or may not need to give the patient fluid
Pre-renal vs. intrinsic kidney damage compare/contrast in terms of:
- BUN: creatinine ratio
- Urinalysis
- Urine sodium
- FeNa
- Urine Osmolality
- Relatively more BUN in pre-renal than intrinsic damage states
- Pre-renal urinalysis is normal while it contains cellular material, RBC, and WBC in intrinsic damage
- Urine sodium high in intrinsic damage; low pre-renal
- FeNa follows urine sodium trend (higher in intrinsic damage)
- Urine osmolality is greater than serum in pre-renal states but ~ same as serum in intrinsic damage
What is hepatorenal syndrome?
Severe liver failure causing intense pre-renal state
- Kidneys anatomically normal and renal function normalizes after liver transplant
What is renal artery stensosis?
Kidney not perfused; thinks pt is dry
-> pre-renal state
How does CHF -> pre-renal state?
Low cardiac output state and low renal perfusion trigger intense sodium and volume conservation
What can be seen on x-ray? Indications?
KUB (Kidney, Ureters, Bladder)
Indications:
- Calcifiations
- Stones
Simple and inexpensive, but lacks details
What are advantages/disadvantages of renal ultrasound? Indications?
Indications:
- Obstruction
- Parenchymal disease
- Doppler blood flow
Advantages
- Safe, no contrast
- Widely available
- GFR independent
Disavantages
- Doesn’t show ureteral anatomy well
- Lower resolution than CT
What is IVP? Advantages/disadvantages? Indications?
Intravenous pyelography
Indications:
- Hematuria, stones
- Malignancies
- Congenital anomalies
Advantages:
- Simple, inexpensive
- Shows collecting system and bladder wall
Disadvantages:
- Poor parenchymal resolution
- Dye toxicity, renal insufficiency In picture: right side is blocked! (less dye in other side because it has already gone down)
CT scan and MRI: Indications? Advantages/Disadvantages?
Indications:
- Tumors, trauma
- Vascular images
Advantages:
- High resolution
- Non-invasive
Disadvantages:
- Expensive
- Dye toxicity
- Claustrophobia
Renal angiography indications? Advantages/disadvantages?
Indications:
- Renal vascular disease
- Transplant donor
Advantages
- Precise vascular imaging
- Angioplasty
Disadvantages
- Invasive
- Dye nephropathy
- Expensive
