USMLE Step 1 Renal
anatomy of bowmans capsule ------- ✔ CORRECT ANSWER ✓✓kidney and ureters are
retroperitoneal
ureters are BEHIND vas deferens, BEHNID uterine artery
water distribution in body compartments ------- ✔ CORRECT ANSWER ✓✓...
glomerular filtration barrier components ------- ✔ CORRECT ANSWER ✓✓Fenestrated capillary
endothelium (size barrier)
Fused basement membrane with heparan sulfate
(negative charge barrier)
Epithelial layer consisting of podocyte foot processes
THE BASEMENT MEMBRANE LAYER IS LOST IN NEPHROTIC SYNDROME - LOST CHARGE BARRIER
--> albuminuria, hypoproteinemia, generalized edema, and hyperlipidemia
BM = type IV collagen, made by visceral
epithelial/podocyte
renal clearance + GFR ------- ✔ CORRECT ANSWER ✓✓CL = UV/P
in mL/min
NL ~ 100 mL/min
creatinine moderately overestimates GFR
(some secretion)
inulin accurately measures GFR
,in pregnancy and early diabetic nephropathy -->
INCR in Cr CL
in elderly and acute/chronic renal dz -->
DECR in Cr CL
effective renal plasma flow (ERPF) ------- ✔ CORRECT ANSWER ✓✓CL = UV/P
use PAH as proxy
ERPF can be estimated using PAH CLEARANCE bc it is both FILTERED and actively SECRETED
(CARRIER MEDIATED TRANSPORT) in the proximal tubule + ALL PAH entering the kidney is
EXCRETED
--> typically underestimates renal plasma flow by 10%
RBF = RPF/(1 - Hct)
filtration fraction + load ------- ✔ CORRECT ANSWER ✓✓FF = GFR/RPF
NL ~ 20%
filtered load = GFR x plasma concentration
modulators of afferent + efferent arteriole ------- ✔ CORRECT ANSWER ✓✓...
effect of plasma protein concentration on GFR, FF ------- ✔ CORRECT ANSWER ✓✓incr [plasma]
= decr GFR, decr FF
,decr [plasma] = incr GFR, incr FF
reabsorption + secretion calcs ------- ✔ CORRECT ANSWER ✓✓excretion rate = U x V
filtered load = GFR x [plasma]
reabsorption = filtered - excreted
secretion = excreted - filtered
glucose clearance ------- ✔ CORRECT ANSWER ✓✓AT NORMAL PLASMA CONCENTRATIONS
GLUCOSE IS COMPLETELY REABSORBED IN PROXIMAL TUBULE BY
Na/glucose COTRANSPORT
DIABETES (~>160) --> GLUCOSURIA
all transporters fully saturated at 350
AA clearance ------- ✔ CORRECT ANSWER ✓✓Na mediated transport in PROXIMAL TUBLE
COMPETITIVE INHIBITION between AAs
--> PROTEINURIA when overloaded
HARTNUPs DZ = NEUTRAL AA TRANSPORTER DEFICIENCY - TRYPTOPHAN TRANSPORTER in
kidney
--> CANT RESORB NEUTRAL AA's - TRYPTOPHAN
--> CANT MAKE 5HT, MELATONIN, NIACIN/NAD+
TRYPTOPHAN DEFICIENCY --> PELLAGRA
, membrane channels in proximal tubule ------- ✔ CORRECT ANSWER ✓✓Early proximal tubule -
contains brush border
Reabsorbs all glucose and AA and most of the bicarbonate, Na, Cl, and water
ISOTONIC absorption
Secretes NH3, buffer for secreted H+
PTH - inhibits Na+/PO4 cotransport --> PO4 excretes
ATII - stimulates Na/H+ exchange --> Na + H2O reabsorption (CONTRACTION ALKALOSIS).
membrane channels in thin descending limb ------- ✔ CORRECT ANSWER ✓✓passive resorption
of H2O via countercurrent multiplier in medulla
concentrates urine in medulla
membrane channels in thick ascending limb ------- ✔ CORRECT ANSWER ✓✓actively reabsorbs
Na+, K+, and C I- and indirectly induces2the paracellular reabsorption of M i+ and Ca +.
Impenneable to H20. Makes urine less concentrated as it ascends.
membrane channels in distal convoluted tubule ------- ✔ CORRECT ANSWER ✓✓Earlydistal
convoluted tubule-actively reabsorbs Na+CI.
Diluting segment --> Makes urine hypotonic
PTH incr Ca/Na exchange --> incr Ca resorption
anatomy of bowmans capsule ------- ✔ CORRECT ANSWER ✓✓kidney and ureters are
retroperitoneal
ureters are BEHIND vas deferens, BEHNID uterine artery
water distribution in body compartments ------- ✔ CORRECT ANSWER ✓✓...
glomerular filtration barrier components ------- ✔ CORRECT ANSWER ✓✓Fenestrated capillary
endothelium (size barrier)
Fused basement membrane with heparan sulfate
(negative charge barrier)
Epithelial layer consisting of podocyte foot processes
THE BASEMENT MEMBRANE LAYER IS LOST IN NEPHROTIC SYNDROME - LOST CHARGE BARRIER
--> albuminuria, hypoproteinemia, generalized edema, and hyperlipidemia
BM = type IV collagen, made by visceral
epithelial/podocyte
renal clearance + GFR ------- ✔ CORRECT ANSWER ✓✓CL = UV/P
in mL/min
NL ~ 100 mL/min
creatinine moderately overestimates GFR
(some secretion)
inulin accurately measures GFR
,in pregnancy and early diabetic nephropathy -->
INCR in Cr CL
in elderly and acute/chronic renal dz -->
DECR in Cr CL
effective renal plasma flow (ERPF) ------- ✔ CORRECT ANSWER ✓✓CL = UV/P
use PAH as proxy
ERPF can be estimated using PAH CLEARANCE bc it is both FILTERED and actively SECRETED
(CARRIER MEDIATED TRANSPORT) in the proximal tubule + ALL PAH entering the kidney is
EXCRETED
--> typically underestimates renal plasma flow by 10%
RBF = RPF/(1 - Hct)
filtration fraction + load ------- ✔ CORRECT ANSWER ✓✓FF = GFR/RPF
NL ~ 20%
filtered load = GFR x plasma concentration
modulators of afferent + efferent arteriole ------- ✔ CORRECT ANSWER ✓✓...
effect of plasma protein concentration on GFR, FF ------- ✔ CORRECT ANSWER ✓✓incr [plasma]
= decr GFR, decr FF
,decr [plasma] = incr GFR, incr FF
reabsorption + secretion calcs ------- ✔ CORRECT ANSWER ✓✓excretion rate = U x V
filtered load = GFR x [plasma]
reabsorption = filtered - excreted
secretion = excreted - filtered
glucose clearance ------- ✔ CORRECT ANSWER ✓✓AT NORMAL PLASMA CONCENTRATIONS
GLUCOSE IS COMPLETELY REABSORBED IN PROXIMAL TUBULE BY
Na/glucose COTRANSPORT
DIABETES (~>160) --> GLUCOSURIA
all transporters fully saturated at 350
AA clearance ------- ✔ CORRECT ANSWER ✓✓Na mediated transport in PROXIMAL TUBLE
COMPETITIVE INHIBITION between AAs
--> PROTEINURIA when overloaded
HARTNUPs DZ = NEUTRAL AA TRANSPORTER DEFICIENCY - TRYPTOPHAN TRANSPORTER in
kidney
--> CANT RESORB NEUTRAL AA's - TRYPTOPHAN
--> CANT MAKE 5HT, MELATONIN, NIACIN/NAD+
TRYPTOPHAN DEFICIENCY --> PELLAGRA
, membrane channels in proximal tubule ------- ✔ CORRECT ANSWER ✓✓Early proximal tubule -
contains brush border
Reabsorbs all glucose and AA and most of the bicarbonate, Na, Cl, and water
ISOTONIC absorption
Secretes NH3, buffer for secreted H+
PTH - inhibits Na+/PO4 cotransport --> PO4 excretes
ATII - stimulates Na/H+ exchange --> Na + H2O reabsorption (CONTRACTION ALKALOSIS).
membrane channels in thin descending limb ------- ✔ CORRECT ANSWER ✓✓passive resorption
of H2O via countercurrent multiplier in medulla
concentrates urine in medulla
membrane channels in thick ascending limb ------- ✔ CORRECT ANSWER ✓✓actively reabsorbs
Na+, K+, and C I- and indirectly induces2the paracellular reabsorption of M i+ and Ca +.
Impenneable to H20. Makes urine less concentrated as it ascends.
membrane channels in distal convoluted tubule ------- ✔ CORRECT ANSWER ✓✓Earlydistal
convoluted tubule-actively reabsorbs Na+CI.
Diluting segment --> Makes urine hypotonic
PTH incr Ca/Na exchange --> incr Ca resorption
