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Unit 3 PCS > Week 8 - Kidney physiology > Flashcards

Week 8 - Kidney physiology Flashcards

1
Q

What are the functions of the kidney?

A

Kidneys;

  • 1) Maintain salt and water balance
  • 2) Converting Vitamin D to its active form, by adding an OH group to carbon 25 (see vit. d metabolism)
  • 3) Exertion of drugs and non-nutritive materials
  • 4) Blood manufacture as produced erythropoietin hormone Among others!
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2
Q

What are the steps involved in the formation of urine?

A

Remember Going To Toilets Saddens! Glomerular Filtration Tubular Reabsorption Tubular secretion Selective Movement

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3
Q

What is filtered during glomerular filtration?

A

Of the 100% of plasma that enters the glomerulus, 20 % is filtered. Things that are filtered: EVERYTHING IN PLASM MINUS PLASMA PROTEINS i.e. Water Sodium Urea Phenols from food Creatinine

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4
Q

Outline the process of tubular reabsorption

A

See week 8 PcS notes

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5
Q

What substances are secreted and why?

A
  1. H+ ions - regulating acid base balance (If blood too acidic, more H+ is secreted)
  2. K+ ions
  3. Organic anions and cations
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6
Q

How does the reabsoprtion of Na+ at proximal tubule lead to PASSIVE reabsorption of urea, water and Cl-as well as glucose and amino acids?

A
  • Chloride - Relative to Na+ reabsorption.. as it is an anion it follows Na+
  • Water - Follows Na+ down water potential gradient. Passes through aquaporins (water channels)
  • Urea - Active Na+ reabsorption and passive water reabsorption produces a concentration gradient
  • Glucose and amino acids - Na+ dependent secondary active transport
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7
Q

What are the different pressures affecting gloerular filtration at the glomerulus and bowmann’s capsule?

A
  • Hyrdostatic pressure
    1) Glomerular capillary hydrostatic pressure (water/solutes to filtrate)
    2) Capsular hydrostatic pressure (water/solutes out of filtrate to plasma)

Colloid Osmotic pressure

(water/solutes out of filtrate to plasma)

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8
Q

How would you calculate Net filtration pressure?

A

NFP = Glomerular hydrostatic pressure - Capsular hydrostatic pressure - Colloid Osmotic pressure

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9
Q

What does the glomerular filtrate depend on?

A
  1. Hydrostatic pressures
  2. Colloid osmotic pressures
  3. Physical properties of the barrier
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10
Q

Although the glomerular filtration rate depend on age, gender and body size, what is the average value?

A

–Men 130ml/min/1.73m2
–Women 120ml/min/1.73m2

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11
Q

What is Kf?

A

Filtration coefficient, and it depends on

  1. Surface area of glomerulus
  2. Hydraulic properties (liquid movement under pressure)
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12
Q

How is GFR calculated?

A

= Kf X Net filtration pressure

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13
Q

Approximately what is the filtration pressure?

A
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14
Q

What is the clinical relevance of GFR? What can it NOT be used for?

A

Clinical relevance -

  • assess the degree of kidney impairment
  • (as it shows sum of all filtration rates in nephrons)
  • Effectiveness of renal excretion

Not used for a diagnosis! Thats done by

  • Radiological studies
  • Renal biopsy
  • Urine analysis
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15
Q

What does a declining GFR indicate?

A
  • Progression of a diesease process
  • Posiible reduced renal perfusion
  • No exact correlation to loss of kidney nephrons as kidneys can compensate
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16
Q

When measuring GFR, what kind of substance would be an ideal marker, given you cannot measure directly?

A

A substance that is

  1. freely filtered at the glomerulus
  2. not secreted or reabsorbed
  3. Therefore plasma clearance rate volume of plasma cleared of that substance per min = GFR
17
Q

Inulin is a good marker of GFR, would would you calculate GFR using inulin?

A

GFR = Urine concentration of inulin X Urine flow rate

_________________________________

PLasma concentration of inulin

= 125 mg/mL X 1

_____________

1

= 125 ml/min

18
Q

Why would using an endogenous substance like creatinine be better than using Inulin?

A
  • Less time consuming
  • Don’t have to infuse continuously to determine a constant plasma concentration
19
Q

What is creatinine and what are its characteristics in terms of filtration, reabsorption and secretion?

A
  • Derived from skeletal muscle
  • It is freely filtered
  • NOT reabsorbed
  • Some secretion
  • If diet (meat intake), muscle mass etc is constant, creatinine is constant
20
Q

How can yoy improve on creatinine dervived GFR rate?

A

Incorporate demographic changes i.e. using MDRD eGFR;

  1. age
  2. gender
  3. creatinine
  4. ethinicity
21
Q

What is the relationship between MDRD e GFR and measured GFR?

A

Directly proportional relationship

Graph in notes comes from USA patients with renal impairment showing

  • MDRD formula works well at mid GFR levels
  • MDRD formula doesn’t work well at higher levels
22
Q

What things affect creatinine clearance?

A

different muscle mass, (due to age, ethinicity, gender)

23
Q

What does this CT scan show?

A

Acutely swollen and odematous kidney

24
Q

A patient comes in with loin pain and a CT scan is done.. What does this CT scan show?

A

An emphesamatous kidney

25
Q

What are the sites of infection in the Urinary tract?

A
26
Q

What are the symptoms of

  • acute pylonephritis
  • Lower UTI
  • Pyonephrosis, cortical abcess, staghorn calculus
A
27
Q

What is the prevelance of UTIs in women in comparison to men?

A

Women: Occurs more often as shorter urethra

  • infancy
  • preschool
  • middle age

Men: Less often as longer urethra

  • Infancy
  • Old age
28
Q

What host factors increases a person’s suseptibility to getting a UTI?

A

•Congenital abnormalities of the tract
–Vesicoureteric reflux
–Anatomical abnormalities
–Dilatation +/- obstruction
•Acquired abnormalities
–Prostatic enlargement
•Calculi
•Haematuria
– ­ increased Fe

29
Q

Angie has come in to the clinic again after being treated for her UTI with IV antibiotics. She says she is getting the same symptoms she has before..

  • what is the most likely bacteria that has caused re-infection?
  • What drugs might you ask her about that may have been involved in this recurrence?
A
  • Most common is E. Coli, although you cannot be sure until you analyse the patient’s urine
  • 27% of women get recurrent infection!
  • Oral contraceptive pill
30
Q
  • What would you suggest to Angie to prevent a recurrent UTI?
A
  • Voiding frequently (2-3 hours)
  • Voiding before bedtime and after having sex
  • Cranberry juice, for prevention not treatment! Reduced risk of symptoms
31
Q

What investigations may you do on Angie?

A
  1. Cystoscopy
  2. Pre and post mic ultrasound
32
Q

What kind of cells are found at each part of a nephron?

A

Proximal tubule

  • cuboidal cells with microvilli for increased surface area (lots of mitochondria for active transport)
  • Reabsorption occurs here mostly

Distal tubule -

Cuboidal cells

Unit 3 PCS (8 decks)

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