Renal assessment and physiology of micturition

Question 1

What are 2 situations GFR is useful?

Answer 1

renal disease

drugs

Question 2

What does the total GFR =?

Answer 2

Sum of all filtration by functioning nephrons so progression of disease indicated by decrease in GFR

Question 3

Why is GFR important in terms of drugs?

Answer 3

eg antibiotics removed by filtration - excretion
drug concentration in plasma could become toxic
adjust dose

Question 4

What tests are done to measure GFR (renal function)?

Answer 4

plasma clearance test

Question 5

What does the plasma clearance test measure?

Answer 5

ability of kidney to clear plasma of various substances

Question 6

What is important in plasma clearance tests - plasma or urine?

Answer 6

volume of plasma

Question 7

What is the gold standard for plasma clearance tests?

Answer 7

inulin

Question 8

Why is inulin the gold standard for plasma clearance tests?

Answer 8

no reabsorption or secretion
100% filtered is excreted
not metabolised by kidney
inulin clearance - GFR

Question 9

If substances are filtered and reabsorbed what will their clearance be compared to inulin?

Answer 9

lower

Question 10

If substances are filtered and secreted what will their clearance be compared to inulin?

Answer 10

higher

Question 11

GFR value

Answer 11

125mls/min

Question 12

What causes changes in GFR?

Answer 12

women - 10% less due to SA

lose 1ml/min/year after 30

Question 13

In clinical practice what was the next best after inulin to measure GFR?

Answer 13

radioactive substance handled same as inulin

Question 14

Why is the direct ways to measure GFR not used anymore?

Answer 14

Too complex
injections
expensive

Question 15

What is routinely used to estimate GFR?

Answer 15

creatinine clearance

Question 16

What is creatinine?

Answer 16

endogenous product of muscle creatine breakdown

Question 17

Problem with creatinine clearance to measure eGFR

Answer 17

not a linear correlation

need to lose about 50% of GFR to notice difference in levels

Question 18

3 factors affecting serum creatinine

Answer 18

muscle mass
dietary intake
drugs

Question 19

Normal approx. GFR

Answer 19

100mls/min/1.73m squared

Question 20

Glucose clearance and why

Answer 20

0 - all reabsorbed

Question 21

Urea clearance and why

Answer 21

less than inulin as some is reabsorbed

Question 22

What is PAH used to measure?

Answer 22

renal plasma flow

Question 23

Why is PAH used to measure RPF?

Answer 23

freely filtered and remaining is secreted

more than 90% excreted in 1 transit

Question 24

Renal plasma flow value

Answer 24

660ml/min

Question 25

Penicillin clearance and why

Answer 25

higher than inulin as some secreted

Question 26

How does urine travel from kidneys to ureters?

Answer 26

peristaltic contraction of smooth muscle of ureters

Question 27

Does urine composition change once it leaves the kidneys?

Answer 27

no

Question 28

Bladder muscle name

Answer 28

detrusor muscle - spiral, longitudinal and circular

Question 29

Is the external or internal urethral sphincter a true sphincter?

Answer 29

external

Question 30

Epithelium in bladder

Answer 30

transitional

Question 31

Relations of bladder

Answer 31

midline posterior to pubic bones anterior to rectum and repro. organs

Question 32

What makes up the trigone?

Answer 32

2 vesicoureteric orifices | urethral opening

Question 33

Would urethral and ureter problems cause bilateral or unilateral kidney problems?

Answer 33

urethra - bi, ureter - uni

Question 34

Describe the pressure-volume curve of bladder

Answer 34

characteristic shape long flat segment with initial urine sharp rise as micturition reflex triggered

Question 35

Normal daily urine production

Answer 35

750-2500mls

Question 36

Motor innervation of bladder - parasympathetic

Answer 36

pelvic nerves contract detrusor muscle | S2-4

Question 37

Motor innervation of bladder - sympathetic

Answer 37

hypogastric nerves L1-3 | inhibit bladder contraction and close internal sphincter

Question 38

Main function of hypogastric nerves

Answer 38

prevent semen reflux into bladder in ejaculation

Question 39

Motor innervation of bladder - somatic motorneurons

Answer 39

external urethral sphincter - keep it closed | S2-4

Question 40

Sensor innervation of bladder

Answer 40

stretch receptors --> spinal cord

Question 41

Consequence of activating stretch receptors in bladder

Answer 41

a - parasympathetic flow b - inhibit sympathetic c - inhibit somatic motorneurons to external sphincter d - pathways to sensory cortex - sensation of fullness

Question 42

Volume needed to initiate micturition reflex

Answer 42

300-500mls

Question 43

How is delay of micturition accomplished?

Answer 43

descending pathways which stimulate somatic nerves, inhibit parasympathetic and over ride input from bladder

Question 44

What does voluntary initiation of micturition consist of?

Answer 44

stimulate parasympathetic | inhibit somatic motor neurons

Question 45

What does relaxing pelvic floor muscles do?

Answer 45

may cause sufficient downward tug of detrusor

Question 46

Significance of perineal and external sphincter muscles contracted voluntarily

Answer 46

prevent stopping midstream and prevent urine flow down urethra

Question 47

How does female urethra empty after urination?

Answer 47

gravity

Question 48

How does male urethra empty after urination?

Answer 48

contractions of bulbocavernous muscle

Question 49

3 major types of neural abnormalities of micturition

Answer 49

problems with afferent problems with afferent and efferent interruption of facilitatory and inhibitory descending pathways

Question 50

Significance of neural abnormalities of micturition

Answer 50

bladder contracts but not enough to expel all urine - high residual volume

Question 51

Ways paraplegics can have some control over micturition

Answer 51

rub/pinch thigh - mild mass reflex | mild noxious stimuli on skin