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UROGENITAL > 9. Renal Physiology III - Measurement of Renal Function > Flashcards

9. Renal Physiology III - Measurement of Renal Function Flashcards

1
Q

FUNCTIONS of KIDNEY

A
  • EXCRETION of metabolic waste products and foreign chemicals
  • REGULATION
    (water and electrolytes balance, arterial pressure, acid-base, erythrocyte production, D3 production..)
  • SECRETE, EXCRETE or METABOLISE HORMONES
  • Gluconeogenesis (contributes)
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2
Q

what is RENAL CLEARANCE

A

the VOLUME OF PLASMA that is completely CLEARED of the SUBSTANCE by kidneys per unit of time

(provide useful way of quantitating effectiveness with which kidneys excrete various substances)

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3
Q

we can use RENAL CLEARANCE to quantify:

A
  • RENAL BLOOD FLOW
  • GFR
  • TUBULAR REABSORPTION
  • TUBULAR SECRETION
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4
Q

how much of the CARDIAC OUTPUT (BLOOD) flows through KIDNEYS

A

about 20%

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5
Q

RENAL PLASMA FLOW (RPF) is equal to

A

Renal Blood Flow x (1-Hematocrit)

(hematocrit : volume of red blood cells in blood)

usually 55% of rbf

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6
Q

GFR averages how much of RENAL PLASMA FLOW (filtration fraction = GFR/RPF)

A

20%

(20% of plasma that goes through glomerulus is filtered)

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7
Q

what is the GFR in an average adult human

A

125 ml/min

or 180 L / day

(RPF = 625 ml/min
RBF = 1200 ml/min)

(FF = 125/625 x 100 = 20%)

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8
Q

how much of the FLUID FILTERED is normally REABSORBED

A

OVER 99%

(Urine flow rate is less than 1% of GFR)

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9
Q

CALCULATION to measure RENAL CLEARANCE (clearance rate of a substance) C

A

C = U V / P

U = conc. of substance in urine
V = urine flow rate / volume
P = conc. of substance in plasma

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10
Q

what substance do we use to measure exact GFR where C = GFR

A

INULIN (polysaccharide
(freely filtered, NOT reabsorbed, NOT secreted, not broken down, not toxic)

(clearance rate would be 125 ml/min)

Creatine can be used but will be secreted so overestimate (140 ml/min)

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11
Q

how much of RENAL PLASMA FLOW is actually filtered (GFR)

A

20%

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12
Q

what substance can we use to calculate RENAL PLASMA FLOW where C = RPF

A

PAH (PARA-AMINOHIPPURIC ACID)

  • freely filtered and almost completely SECRETED
    (average of 90% is cleared by kidneys from renal blood stream in single circulation)

C = UV/P = RPF

U= PAH conc in urine
V= urine flow rate
P = PAH conc in plasma

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13
Q

how to calculate RBF when you have RPF

A

RBF = RPF X (1-HEMATOCRIT)

hematocrit = volume rbc in blood

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14
Q

how to calculate EXCRETION RATE

A

U x V

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15
Q

how to calculate Reabsorption Rate

A

(GFR x P) - (U x V)

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16
Q

Clearance rate of Glucose

A

0

(all reabsorbed)

(unless diabetes)

17
Q

Clearance rate of Sodium

A

0.9 - LOW

MOST SODIUM REABSORBED

18
Q

Clearance rate of Sodium

A

0.9 - LOW

MOST SODIUM REABSORBED

19
Q

what would happen to creatinine if GFR levels declined

A

secrete more creatinine from blood so stay same

therefore not accurate marker

20
Q

another marker for GFR

A

SERUM CYSTATIN C concentration

cystatin c - small protein
expressed in all nucleated cells
Freely Filtered
NOT secreted
reabsorbed but catabolised (so not returned to plasma)

21
Q

markers for GFR

A
  • Inulin
  • Creatine (standard surrogate marker)
  • cystatin c
22
Q

3 LAYERS in the FILTRATION BED of the GLOMERULUS

A
  • ENDOTHELIUM
  • BASEMENT MEMBRANE
  • EPITHELIUM - PODOCYTES
    (have foot like-processes which form slit pores)
23
Q

what is PROTEINURIA

A

large amounts of PROTEIN in the URINE

urine dip stick to test

24
Q

what is HAEMATURIA

A

BLOOD in URINE

Urine dip stick to test

25
Q

in URINE MICROSCOPY if there are NO RED BLOOD CELLS what could it be

A

HAEMAGLOBINURIA

26
Q

in URINE MICROSCOPY if there are NO RED BLOOD CELLS what could it be

A

HAEMAGLOBINURIA

or MYOGLOBULINURIA (brown urine)

27
Q

RED BLOOD CELLS in URINE - HAEMATURIA could be due to

A

Infection,
blood loss (cancer)
glomerular bleed / intrinsic kidney disease

GLOMERULAR FILTRATION BED is BROKEN

28
Q

what is ERYTHROPOIETIN

A

GLYCOSYLATED PROTEIN with 165 AMINO ACIDS

GROWTH FACTOR that CONTROLS the RED BLOOD CELL MASS

29
Q

where is ERYTHROPOIETIN PRODUCED

A

90% KIDNEYS - interstitial PERITUBULAR CELLS

and to a lesser extent by liver

30
Q

role of ERYTHROPOIETIN

A

the RATE OF PRODUCTION of RBCs is governed by Erythropoietin

INCREASES RATE

31
Q

when does KIDNEY PRODUCE ERYTHROPOIETIN

A

responds to REDUCED OXYGEN TENSION

  • causes HIGHER RATE of RED CELL PRODUCTION in BONE MARROW
32
Q

when does KIDNEY PRODUCE ERYTHROPOIETIN

A

responds to REDUCED OXYGEN TENSION

  • causes HIGHER RATE of RED CELL PRODUCTION in BONE MARROW
33
Q

relationship between HYPERTENSION (High blood pressure) and kidney disease

A

HIGH BP can CAUSE / CONTRIBUTE TO KIDNEY DISEASE
or
can DEVELOP HYPERTENSION due to KIDNEY DISEASE

( RAAS system - renin from kidneys increases BP
& sodium retention
& sympathetic nervous system)

34
Q

the more advanced RENAL IMPERAIRMENT the more LIKELY..

A

HYPERTENSION

UROGENITAL (19 decks)

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