Acute Kidney Disease Flashcards
Describe the anatomy of the kidney.
we have two
back, below rib cage, behind peritoneum on both sides of the spine (T12-L3)
4-5 inches long (slightly larger than a fist)
Which structure of the kidney contains arteries, veins, and some nerves?
renal hilum
contains the renal vein, renal artery, and renal nerve
What are the major functions of the kidneys?
filter blood/excrete toxins (major function)
metabolize compounds
secrete hormones (endocrine functions)
maintain pH (HCO3) and electrolyte balance
What is a likely reason that kidney disease is usually silent until advanced?
no pain receptors in the kidney
What is an example of a rare occasion where kidney pain would be present without being in advanced stage of kidney disease?
kidney stones
-scratching the walls of the ureter
Describe blood flow through the kidney.
- renal artery (segmental artery, interlobar artery, arcuate
artery, interlobular artery) - afferent arteriole
- glomerulus
- efferent arteriole
- peritubular capillaries
- renal vein (interlobular vein, arcuate vein, interlobar vein)
What is the normal GFR?
100-120ml/min filtered into tubules
How long does it take to filter all of the blood in the body?
40-50 minutes (5L of blood)
kidneys are constantly working to remove waste
What size of molecules are filtered at the glomerulus?
small molecules (<70 kDa)
-glucose, ions, amino acids, proteins
Describe reabsorption at the proximal tubule.
substantial reabsorption of filtered material
60-70% of filtered Na+
almost all K+
almost all glucose
water reabsorbed passively along Na+ osmotic gradient
Describe reabsorption at the Loop of Henle.
30ml/min of filtrate delivered to the Loop
substantial Na+ and H20 reabsorption:
-Descending Limb: H20
-Ascending Limb: Na+
Describe reabsorption at the distal and collecting tubules.
water channels under control of vasopressin
-stimulates H20 reabsorption without Na+
target for aldosterone
-K+ excretion, Na+ reabsorption
Which part of the nephron plays a role in regulation of pH? How does it regulate pH?
distal and collecting tubules
respond toward acidosis by increasing H+ secretion and HCO3- generation
How much filtrate reaches the ureters?
1-2ml/min
thus, the reabsorption rate is ~99% (we started with 100-120ml/min)
Where does secretion occur in the nephron?
proximal tubule
-many transporters in the proximal tubule
-the transporters are uni or multi directional
Which transporters are involved in drug resistance?
ABC transporters
What is NCC?
thiazide-sensitive NaCl cotransporter
What is ENac?
amiloride-sensitive epithelial sodium channels
Na+ reabsorption at distal tubule
What is one of the most commonly used markers of kidney function/estimating GFR?
serum level of creatinine
What are normal serum creatinine levels?
0.9-1.3mg/dL
Describe creatinine.
produced daily by muscles as part of normal metabolism
easily filtered (levels dont rise unless GFR is reduced)
What would happen to serum creatinine levels as GFR decreases?
less creatinine is excreted
production by muscles continues
=serum creatinine rises
What is the issue of using serum creatinine as a measure of kidney function?
people with low muscle mass will generate less creatinine
thus, creatinine levels will appear normal when GFR is decreased
What is the equation which generates the creatinine clearance (CrCl) to estimate GFR?
Cockroft-Gault equation
CrCl= (140-age) x Ideal Body Weight (kg)/0.814 x Serum Creatinine (ug)
x 0.85 if female
What is the important concept of the Cockroft-Gault equation?
it converts serum creatinine level to an estimated GFR
How do we estimate ideal body weight?
For a 5’0’’ tall person:
-50kg for men
-45kg for women
add 2.3kg for every 1” taller than 5’0”
What is the MDRD equation?
modification of diet in renal disease
can be used to estimate GFR
GFR (ml/min/1.73m²)=175 x (Scr)-1.154 x (Age)-0.203 x (0.742 if female) x (1.212 if African American
What are the consequences of not performing necessary dosing adjustments if renal function is less than optimal?
regular doses will be excreted more slowly, leading to accumulation of drug in the body and risk for adverse drug reactions
What are the major factors determining whether drugs are renally-excreted?
water solubility
-highly soluble=exist freely in the bloodstream, fit through the
glomerulus easier
protein binding
-bound to plasma protein=less likely to be filtered
tubular secretion
-some drugs are concentrated in the urine by active secretion
rather than filtration
What are some drugs that are concentrated in the urine by active secretion rather than filtration?
metformin
furosemide
digoxin
What is the estimated GFR of each stage of CKD?
Stage 1 (kidney damage with normal or GFR): >90
Stage 2 (kidney damage with mild GFR): 89-60
Stage 3A (mild to moderate GFR): 59-45
Stage 3B (moderate GFR): 45-30
Stage 4 (severe GFR): 30-15
Stage 5 (kidney failure): <15 or dialysis
What is proteinuria?
protein in the urine
sign of kidney damage
What is a very common marker of dysfunction in patients with CKD?
proteinuria
True or false: proteinuria can ONLY be elevated with reduced GFR
false
can also be elevated without reduced GFR (damaged glomerulus)
What is a early marker of kidney disease?
low level of albumin in the urine
What are the levels for microalbuminuria? What about macroalbuminuria?
microalbuminuria: 30-300 mg/day
macroalbuminuria: >300 mg/day
What is the advantage of the albumin/creatinine ratio?
a simple spot urine test that accurately predicts microalbuminuria (more convenient than collecting urine for 24hrs)
True or false: albuminuria is a more sensitive marker than total protein
true
What are the ways to measure proteinuria?
urinalysis (most common)
X-ray
MRI
CT
ultrasounds
biopsy
What are the four components of urinalysis closely associated with kidney damage? What are their reference ranges?
specific gravity:
-reference range: 1.005-1.029
protein:
-reference range: negative
epithelial cells:
-reference range: 0-3/HPF
casts:
-reference range: 0-5/HPF
What is AKI? List off some characteristics of this state.
rapid deterioration of renal function within a few hours or a few days
typically diagnosed if either of the following occur:
-rise in SCr by more than 25 uM within 48hrs OR
-decrease in urine output to <0.5 ml/kg/hr for 6hrs
rapidly rising BUN/urea and SCr
diminished urine volume is common (but not necessary)
cause a build-up of waste products in the blood
What are some organs that can be affected by AKI?
brain
heart
lungs
What is the mechanism for developing AKI?
highly complex and overlapping
many mechanisms of AKI are possible
What are the chances of an individual drug causing AKI?
<1%
Who is more susceptible to AKI?
patients with CKD
What are the signs and symptoms of AKI?
too little urine leaving the body
swelling in legs, ankles, and around eyes
fatigue/tiredness
shortness of breath
confusion
nausea
seizure or coma in severe cases
chest pain or pressure
What are the causes of AKI?
pre-renal azotemia:
-reduced glomerular pressure impairing function of tubules
intrinsic renal parenchymal disease:
-direct damage to glomerulus, tubules, or renal vessels
postrenal obstruction:
-obstruction of urine outflow