Acute Kidney Disease Flashcards
Explain the kidney
Bean shaped
there are 2
behind the peritoneum
4-5” long; a little bit larger than fist
Location at T12-l3 (FYI)
What is in the medulla?
Contains the nephron and the tubules
What do the minor and major calyx do?
They send waste to the ureter
What are the main fxns of the kidney?
Filter blood/ excrete toxins
Metabolize compds
Secrete hormones (ex. erythropoietin)
Maintain pH (acid-base) and electrolyte balance
Do patients notice their kidney disease?
No, usually silent until advanced stage
Why do patients not experience kidney pain? What is the exception?
Because there are no pain receptors in the kidney
Exception is kidney stones (the stones scratch the ureter and cause pain)
Explain the process of blood flow in the kidney
Renal artery -> arteries start to branch in the pyramid areas -> afferent arteriole -> glomerulus/bowman’s capsule -> efferent arteriole -> peritubular capillaries -> interlobular vein (out)
Explain the flow of blood within the nephron
Glomerulus -> Bowman’s capsule -> prox convoluted tubule -> descending loop of Henle -> Loop of Henle -> ascending Loop of Henle -> distal conv. tubule -> collection duct
What is normal GFR?
100-120 mL/min filtration into tubules
takes 40-50 minutes for total blood filtration
What types of molecules are filtered? Provide examples
Small (<70kDa) are filtered
glucose, nucleic acids, amino acids, electrolytes
How much Na+ is reabsorbed thru the proximal tubule?
60-70% of Na+; water also reabsorbed here due to osmotic gradient
How much filtrate is delivered to the loop of Henle?
30 mL/min
the loop passes thru the medulla of kidney
H20 is permeable in the descending loop; Na+ is permeable in ascending loop
How much filtrate is delivered to the collecting ducts?
5-10 mL/min
What does vasopressin do to the water channels in the distal and collecting duct?
Vasopressin = Antidiuretic hormone
Stimulates water reabsorption alone
What does aldosterone do in the distal tubule and collecting duct?
Causes Na+ reabsorption and K+ excretion
How much filtrate goes to the distal and collecting tubules?
1-2 mL/min
What are some additional fxns of the distal and collecting tubules?
Regulate pH
Respond to acidosis by increasing H+ secrete and HCO3- generation
What can be said about the transporters in the renal proximal tubule?
The transporters can be uni- or bidirectional
What are thiazides?
They are diuretics that act on the NaCl cotransporters
Prevents Na+ reabsorption
What are amilorides?
They are potassium-sparing diuretics which can decrease K+ execration at distal tubule
What is the main marker for kidney function? What is the normal value?
Creatinine levels
Normal: 0.9-1.3 mg/dL
What is the significance of creatinine?
Produced daily by the muscles as part of normal metabolism
Easily unfiltered, so levels don’t rise unless GRF is reduced
Used to estimate GFR
What can be seen as GFR decreases?
Less creatine excreted and creatinine levels rise in the blood
production by muscle still continues
What are the four variables for creatinine clearance?
Age, ideal body weight (kg), serum creatinine (uM), sex
What is an easy way to estimate IBW?
IBW for a 5ft tall person (50kg M; 45kg F)
Add 2.3 kg for every 1” taller than 5’0”
What is MDRD?
Modification of Diet in Renal Disease
We can use MDRD equation to estimate GFR
What are the four variables in MDRD?
Serum creatinine, Age, Sex, African American
How is MDRD useful in drug therapy?
Many drugs require dosage reduction when renal function is less than optimal
If not adjusted, lowered clearance means accumulation of drug
What are some factors that influence whether a drug is renally excreted?
Water solubility
Protein-binding
Tubular secretion
How is CKD severity assigned?
GFR acts as a function of kidney function.
Normal kidney function: GFR is above 90ml/min
Kidney failure: GFR is below 15 (may require dialysis)
What is proteinuria?
Protein(albumin) in the urine due to issues in filtration (glomerular dysfunction)
A common marker of CKD
What is acute kidney injury?
Rapid deterioration of renal function within a few hours or days
Cause a build-up of waste products in blood
Affect other organs such as the brain, heart, lungs
Can drugs cause acute kidney injury (AKI)?
Yes, most drugs confer a small chance of AKI (less than 1%)
Patients with CKD are more susceptible to AKI
What are some signs and symptoms of AKI?
Too little urine
Swelling in legs, ankles, and around the eyes
Fatigue or tiredness
Shortness of breath
Confusion
Seizures or coma
What are some causes of AKI?
Pre-renal azotemia *reduced glomerular pressure impairing function of tubules)
Intrinsic renal parenchymal disease (direct damage to nephron and vessels)
Post-renal obstruction
What are some common causes of community-acquired causes of AKI?
Volume depletion
Medication adverse reactions
Obstruction of the urinary tract
What are some common causes of hospital-acquired cases of AKI?
Sepsis
Major surgical procedures
Critical illness onvolving heart or lung failure
Contrast agents
Medication adverse reactions
What is pre-renal azotemia?
It is characterized by an increase in urea and creatinine in the blood due to reduced glomerular pressure, but without signs of tubular damage
Usually reversed if addressed before damage occurs
What causes AKI?
Reduced cardiac output
Hypovolemia
Medications (NSAIDs and RAAS inhibitors)
What are some factors that can reduce GFR?
Afferent vasoconstriction
Reduced cardiac output
How do NSAIDs cause AKI?
Reduction of renal blood flow (via vasoconstriction of afferent arterioles)
Direct injury
What are some common comorbitities with chronic glomerular injury?
Diabetes (glucose toxicity)
Hypertension (Increased fluid pressure)
What causes immune-mediated glomerular injury?
Antigens and antibodies tend to get caught in the structure of the glomerulus (high blood flow and pressure)
Immune system may react to parts of the glomerular apparatus directly (autoimmunity)
What can cause acute tubular necrosis?
Nephrotoxic drugs
Ischemia/Reperfusion
Protein Misfolding
Oxidative stress in mitochondria
What is rhabdomyolysis?
A syndrome resulting from the release of myglobin. Myoglobin can precipitation the renal tubules, halting tubular flow and causing tubular cell necrosis
What is interstitial nephritis?
It occurs when spaces between tubules become inflamed. The inflammation usually causes damage to tubules but spares the glomeruli.
Inflammation can be caused by hypersensitive reactions to drugs
What is ischemia-associated AKI?
The kidney medula operates under relative hypoxic conditions, so it is susceptible to pre-renal azotemia, inflammation, atherosclerosis, and other issues that impact blood flow
What are kidney stones?
Idiopathic hypercalcuria (more than 75% of stones contain calcium)
Stones can also be made from uric acid and is associated with hyperuricemia
Can the formation of kidney stones be perceived?
No, stone formationin the kidney is painless, thus, renal damage and hematuria can occur in the absence of pain
Pain is felt due to the distension of the ureter, renal pelvis or capsule
What are some risk factors associated with kidney stones?
Dehydration
Protein intake
High Na+
*High Ca2+ intake actually may not play a big role
What are some complications associated with kidney stones?
Damage from complete blockage of urine, backup of toxins, and pressure
Infection or abcess
Repeated stones
What is the RIFLE criteria in AKD?
The acronym describes progressively worsening presentation of kidney dysfunction
Risk of renal dysfunction
Injury to the kidney
Failure of kidney function
Loss of kidney function
End-stage renal disease (ESRD)
What are the criteria for Risk from RIFLE?
Increase in SCr more than 1.5x baseline
or
25% decrease in GFR
and
Urine output is below 0.5mL/kg/h for 6 hours
What are the criteria for Injury from RIFLE?
Increase in SCr more than 2x baseline
or
50% decrease in GFR
and
Urine output is below 0.5mL/kg/h for 12 hours
What are the criteria for Failure from RIFLE?
Increase in SCr more than 3x baseline
or
75% decrease in GFR
and
Urine output is below 0.3mL/kg/h for 24 h
What are the criteria for Loss from RIFLE?
Persistant AKI = complete loss of renal function in under weeks
What are the criteria for ESRD from RIFLE?
Complete loss of renal function
What are the strengths and limitations of RIFLE?
Strengths:
Provided good prognostic accuracy
Strongly correlated with length of hospitalization stay, renal replacement therapy
Limitations:
Hard to know what the patient’s baseline SCr is before disease begins
What is the AKIN criteria for AKD?
It is a modified RIFLE criteria
What is the definition of Stage 1 AKD according to the AKIN criteria?
Increase in SCr from 1.5-2x baseline
or
If increase in SCr is greater than 0.3mg/dL in 48 hours
and
Urine output is less than 0.5ml/kg/h x 6h
What is the definition of Stage 2 AKD according to the AKIN criteria?
Increase in SCr from 2-3x baseline
and
Urine output is less than 0.5ml/kg/h x 12h
What is the definition of Stage 3 AKD according to the AKIN criteria?
Increase in SCr from 3x baseline
or
If increase in SCr is greater than 4mg/dL in 48 hours
and
Urine output is less than 0.3ml/kg/h x 12h
What are some strengths and limitations of the AKIN criteria?
Strengths:
Solely based on SCr change, not on GFR change
Limitations:
Does not provide AKI classification if increase of SCr occurs in more than 48h
What are some complications associated with AKI?
Pulmonary edema
Anemia
Chest pain (pericarditis)
Muscle weakness
Hyperkalemia
Metabolic acidosis
Permanent kidney damage
Death
What are some risk factors associated with AKI?
Hospitalization
Aging
CV diseases
Hypertension
Diabetes
Kidney and Liver diseases
Certain types of cancer and their treatments
How can AKI be prevented?
Hard to prevent AKI, but risk can be reduced by making the following changes:
Living a healthy lifestyle
Managing kidney and other chronic conditions
Paying attention to drug labels, especially for the OTCs
What are the functions of kidney dialysis?
Treatment of kidney failure
Perform the normal function of kidney
Remove toxins, wastes, and extra fluid from the blood
What are the types of kidney dialysis?
Hemodialysis
Peritoneal dialysis
Describe the process of hemodialysis
The most common type of dialysis
Blood is removed from body and filtered by a external hemodialyzer
Requires vascular access (AV fistula or AV graft used)
What are the advantages and disadvantages of AV fistula?
Advantages:
A surgery connects an artery and vein in the arm. This operation reduces clotting and infection during dialysis
Disadvantages:
It can take 3-4 months to mature before dialysis can be started
Avoid in people with weak veins (older adults)
What are the advantages and disadvantages of an AV graft?
Advantages:
A tube connects an artery to a vein in the arm and allows for faster recovery vs. AV fistula (matures in 2-3 weeks)
DIsadvantages:
Increased chance of clotting and infection
The tube needs to be replaced as it breaks down from being in the body
What are advantages and disadvantages of vascular access catheter?
Advantages:
Dialysis can be started immediately
Disadvantages:
A catheter needs to be inserted each time because it cannot be left in over a period of days.
After a few catheter insertions, it can damage the veins
What is peritoneal dialysis?
Like all types of dialysis, it removes wastes and toxins from the blood when kidneys are no longer functional
Dialysis fluid is flowed from. abag into the peritoneal cavity via a catheter into the abdomen
The pertioneum acts as a filter, and the solution absorbs wastes and extra fluid
After a few hours, the solution along with the wastes is drained out
What are the two types of peritoneal dialysis?
Continous ambulatory peritoneal dialysis
Automated peritoneal dialysis
Can diuretics help treat AKI?
No clear evidence showing the help of diuretics
How are cancer and AKI associated?
AKI and cancer are associated with aging and will often develop independently at that age
Cancer drugs are also nephrotoxic
