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Year 1 Urinary > Clinical nephrology > Flashcards

Clinical nephrology Flashcards

1
Q

What would leukocytes in the urine indicate?

A

UTI.

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2
Q

What would nitrites in the urine indicate? Why?

A

Bacteria in significant numbers, especially gram-negative rods such as E-coli. As some bacteria have enzymes converting Nitrates to Nitrites

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3
Q

What would ketones in the urine indicate? (x4)

A

Starvation, fasting, diabetic ketoacidosis or aspirin poisoning.

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4
Q

What would Bilirubin in the urine indicate? (x4) Why?

A

Cirrhosis, gallstones, hepatitis, or tumours of the liver/gallbladder. Overproduction of Bilirubin, reaches termina maxima.

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5
Q

What would very dilute urine indicate pathophysiologically? (x2)

A

Diabetes insipidus or chronic renal disease.

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6
Q

What would glucose in the urine indicate?

A

Diabetes mellitus.

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7
Q

What would proteins in the urine indicate?

A

Glomerular damage.

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8
Q

What would blood in the urine indicate? (x4)

A

Glomerulonephritis (disease affecting of the glomerulus) kidney stones, tumours, infections.

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9
Q

What would urobilinogen in the urine indicate? (x3) Why – what is urobilinogen?

A

Hemolysis (destruction of red blood cells), hepatitis, cirrhosis. Urobilinogen is reduced bilirubin

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10
Q

What pH should urine be?

A

5.

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11
Q

What can be used to estimate the value for glomerular filtration rate?

A

If molecule is freely filtered (meaning SOLUTE is found in the same concentration in the blood as the GF) and not reabsorbed back into the blood or secreted into the tubules, then amount filtered per unit time = amount excreted per unit of time.

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12
Q

If something is freely filtered, how can plasma concentration be estimated?

A

Its concentration in the glomerular filtrate will be the same in the plasma. OF COURSE, THIS CHANGES AS THINGS begin to get reabsorbed and secreted in the PCT, DCT and Loop of Henle.

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13
Q

What equation equates GFR to urine flow rate? How can this be manipulated to calculate a value for GFR?

A

GFR x Plasma concentration of Y (Py) = Urine flow rate (V) x Urine concentration of Y (Uy) FOR FREELY FILTERED SUBSTANCES. THEREFORE, GFR = V x Uy/Py. THIS CAN BE USED TO CALCULATE GFR.

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14
Q

How else can GFR be measured (according to Benji’s notes)?

A

GFR = Puf x Kf. Kf is an arbitrary constant that represents how many nephrons are working e.g. membrane permeability issues may mean nephron is not working…. Puf is ultrafiltration pressure.

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15
Q

What substances can be freely filtered? (x1) Note about natural occurrence?

A

INULIN – a polysaccharide. It is not naturally found in the body, so must be infused if needed for measurement.

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16
Q

How can we use the GFR-plasma concentration equation to estimate someone’s GFR using the following credentials? (Plasma inulin concentration = 0.12 mmol/L, urine inulin concentration = 12 mmol/L, urine flow rate = 1.2 mL/min).

A

GFR = V x Uy / Py. GFR = 0.0012 L/min [1.2 mL/min] x 12 / 0.12 = 0.12 L/min = 120 mL/min. ALWAYS REMEMBER TO CONVERT.

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17
Q

How is renal clearance calculated?

A

The expression we used to calculate GFR from inulin is known as RENAL CLEARANCE of inulin (Cinulin). Hence, we calculate renal clearance for any substance the same way we would calculate GFR for a freely filtered substance – FOR ANY SUBSTANCE Z, RENAL CLEARANCE (Cz) IS CALCULATED AS: Cz = V x Uz/Pz.

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18
Q

What are the requirements for renal clearance of a substance to EQUAL GFR?

A

Substance is freely filtered and neither reabsorbed nor secreted –> its clearance equals GFR!

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19
Q

If the value for renal clearance of a substance is higher and lower than for inulin, then what can be determined about that substance?

A

HIGHER: there is net secretion (more than it is reabsorbed). LOWER: there is net reabsorption (more than it is secreted).

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20
Q

How can renal plasma flow rate be estimated from infusion of a substance?

A

PAH is filtered and (the ~80% that isn’t filtered is actively) secreted into the PCT, virtually none is reabsorbed and the renal vein will CONTAIN NONE (unlike substances like inulin where not all will be ultra-filtrated so will still be found in renal vein). Therefore, PAH clearance can be used to estimate the volume of plasma perfusing the kidneys per unit of time. This therefore tells us the value for RENAL PLASMA FLOW and not GFR.

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21
Q

What is notation for renal plasma flow rate and urine flow rate?

A

RPF and V respectively.

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22
Q

What is the formula for rate PAH enters the kidneys per minute in the renal arteries?

A

RPF (renal plasma flow rate) x PPAH (concentration of PAH in plasma). If there was no PAH in the blood, then rate of entry into kidney would be 0. Multiplication by concentration is significant for quantifying PAH entry.

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23
Q

What is the formula for rate of excretion of PAH in the urine?

A

V x UPAH (concentration in urine).

24
Q

What three ways are GFR measured?

A

Inulin clearance, creatinine clearance, 51CrEDTA clearance.

25
Q

What are the advantages and disadvantages of inulin clearance for GFR measurement? (x1 and x3)

A

ADVANTAGES: accurate DISADVANTAGES: time-consuming because requires infusion, requires several blood samples, because of short duration over which measurements are usually made bladder catheterisation is usually required (since voluntary bladder emptying may be incomplete).

26
Q

What are the advantages and disadvantages of creatinine clearance for GFR measurement? (x4 and x3)

A

ADVANTAGES: it is an endogenous substance, released into the blood at a relatively constant rate so plasma concentration is stable – so means catheterisation is not necessary, only one plasma sample is needed. VERY SIMPLE. DISADVANTAGES: 24-hour urine collection, some is secreted into the PCT so can slightly overestimate GFR, AND not very specific because it measures ‘non-creatinine chromogens’ in plasma, but not found in the urine.

27
Q

How is 51CrEDTA clearance measured to estimate GFR?

A

Emits radiation so can be READILY and ACCURATELY quantified in the plasma. The clearance of such substances can be determined by monitoring their disappearance from the plasma after administering a given dose and taking blood samples, thus eliminating need to collect urine. 51CrEDTA is EDTA labelled with a gamma-emitter and administered as a single injection.

28
Q

How does 51CrEDTA clear from the body?

A

Exponentially. Hence, second plot is on a Log scale. [PHOTO 1].

29
Q

What are the advantages of 51CrEDTA? (x2)

A

Injection of a single dose only and collection of 2-3 plasma samples taken at appropriate times after the injection i.e. on the straight line portion of the log-curve.

30
Q

Given that 51Cr EDTA is free to permeate the whole ECF, how do you explain the initial steep phase of the plasma disappearance curve following a single IV injection?

A

When it is initially given intravenously, it is in high concentration in the blood, so more is secreted – hence steep phase. HOWEVER, EDTA freely permeates the ECF, so over time, EDTA moves out of the blood and so cannot be filtered. The straight line represents the point when ECF and blood is at equilibrium.

31
Q

How are urine test strips used?

A
  1. Dip completely to immerse reagent areas in urine and remove immediately. 2. Tap the edge gently perpendicular against the side of the container or blotting paper to remove excess urine. 3. Place the test strip in a horizontal position on the blotting paper to prevent chemicals mixing from adjacent reagent areas. Start the timer. 4. Read the test strip at 45 seconds by holding it over the matching colour charts. Specific gravity should be read at 45 seconds (measure of the concentration of particles in urine – the more dehydrated, the higher the measurement).
32
Q

What is a midstream sample of urine (MSSU)?

A

Obtain a sample of urine from the middle of the bladder.

33
Q

What is it important to get an MSSU?

A

If bacteria are found in the MSSU sample, it means urine is infected. A midstream sample is best as this first bit of urine that you pass may be contaminated with bacteria from the skin, in or around the urethra.

34
Q

Why is it important to immediately replace the lid of the urine dipstick strips container?

A

Prevent contamination of the urine test strips and to prevent reagents on the test strip reacting with contaminants in the air. In particular, the test for nitrates (which indicates the presence of nitrate-producing organisms such as certain bacteria) can react with airborne chemicals.

35
Q

What are the most important findings for each patient?

A

Sample A: high glucose and high ketone production. Blood presence. Sample B: high protein concentration and nitrite levels. Blood presence. Sample C: normal person. Sample D: high pH.

36
Q

What would alcoholism do to the urine?

A

Alcohol intake raises urine pH.

37
Q

What condition would you expect urine to be very dilute?

A

Diabetes insipidus – lots of water, so urine very dilute.

38
Q

What does cloudy urine sometimes suggest?

A

Infection.

39
Q

What are the four functions lost because of renal failure?

A

Loss of excretory function; loss of homeostatic function; loss of endocrine function; abnormality of glucose homeostasis (because kidney can produce glucose and involved in insulin metabolism).

40
Q

What is the consequence of loss of excretory function in the kidneys?

A

Accumulation of waste products.

41
Q

What is the consequence of loss of homeostatic function in the kidneys? (x3)

A

Disturbance of electrolyte balance, loss of acid-base control, and inability to control volume homeostasis.

42
Q

What is the consequence of loss of endocrine function in the kidneys? (x2)

A

Loss of erythropoietin (stimulates RBC production in bone marrow) production and failure to 1 alpha hydroxylase vitamin D (converts into active vitamin D).

43
Q

What is the consequence of abnormality of glucose homeostasis in the kidneys?

A

Decreased gluconeogenesis.

44
Q

What is reflux nephropathy?

A

Kidney damage from urine flowing backward from the bladder to the kidneys.

45
Q

PATIENT: elderly woman, lethargic, weakness and anorexia, clinically volume depleted resulting in severe hypotension, elevated plasma urea and creatinine makes diagnosis of renal failure. This is complicated by hyperkalaemia (K+), hyponatraemia (Na+), metabolic acidosis, and anaemia. ULTRASOUND shows two shrunken kidneys: What causes the symptoms of lethargy and anorexia? (x3)

A
  • FAILURE OF EXCRETION: accumulation of nitrogenous waste products (urea) also tells us that she has accumulation of other ‘medium-sized’ molecules such as hormones and peptides.
  • FAILURE OF HOMEOSTASIS: acidosis, hyponatraemia, volume depletion (low blood pressure).
  • FAILURE OF ENDOCRINE FUNCTION: anaemia.
46
Q

What are the two salt/water imbalances that can be seen in chronic renal disease patients?

A
  1. Renal dysfunction makes it more difficult to excrete salt and water. This leads to tendency to RETAIN SODIUM AND WATER, leading to:
    • Hypertension.
    • Oedema.
    • Pulmonary oedema.
  2. Renal dysfunction affecting predominantly the deeper tubule interstitium (tubulointerstitial disorders) means that the concentrating mechanisms have been damaged – so salt and water is not reabsorbed, and hence patients LOSE SODIUM AND WATER. This leads to:
    • Inability to increase sodium reabsorption, when sodium is depleted, so patients suffer hyponatraemia.
    • Osmotic diuresis (increased urine production) – caused by high concentration of small molecular weight waste substances which cannot be reabsorbed. Therefore, osmotic pressure increases in the tubule and water is retained in the tubules.
    • This inappropriately high loss of salt and water results in volume depletion which causes the low blood pressure.
47
Q

What are the implications of acidosis? (x3 bullet points) Cause?

A

CAUSED by decreased excretion of H+ ions and by retention of acid bases in the tubules.

  • There is a tendency for hyperkalaemia: where H+ move into intracellular compartments and exchanged for K+ (H+/K+ exchange mechanism).
  • Another compensation mechanism is increasing CO2 loss through the lungs – results in Kussmahl respiration (air hunger) where patient hyperventilates to try and remove the acid in the blood.
  • Exacerbates anorexia and increases muscle catabolism.
48
Q

What are the implications of hyperkalaemia? (x2 bullet points) Cause?

A

CAUSED by failure of distal tubule to secrete potassium. Exacerbated by acidosis – causes shift of potassium from intracellular to extracellular spaces.

  • Can cause cardiac arrhythmias (usually initial loss of p waves, high t waves and bradycardia) and arrest.
  • Can affect neural and muscle activity (high K+ can weaken or even paralyse muscles).

Clinical features of hyperkalaemia are dependent on the chronicity of the hyperkalaemia.

49
Q

What are the implications of decreased erythropoietin?

A

Produced in the kidneys. Hence, kidney failure results in decreased levels – results in anaemia.

50
Q

What are the implications of low 1-25 Vit D levels?

A

Result in poor intestinal calcium absorption, hypocalcaemia (short term) and hyperparathyroidism (longer term).

51
Q

What are the causes of hyperparathyroidism from chronic renal failure? (x3)

A
  1. Phosphate retention.
  2. Low levels of calcitriol (form of active Vit D) and can be caused by phosphate retention.
  3. Hypocalcaemia (caused by phosphate retention and low calcitriol).
52
Q

How does chronic kidney disease result in elevated cardiovascular disease risk? (x4)

A

CKD has a huge association with increased CV disease risk. It can lead to:

  • Hypertension.
  • Secondary cardiac effects.
  • Endothelial effects.
  • Lipid abnormalities.

We are not certain about the mechanisms; we just know these associations.

53
Q

PATIENT: elderly woman, lethargic, weakness and anorexia, clinically volume depleted resulting in severe hypotension, elevated plasma urea and creatinine makes diagnosis of renal failure. This is complicated by hyperkalaemia (K+), hyponatraemia (Na+), metabolic acidosis, and anaemia. ULTRASOUND shows two shrunken kidneys: How is our patient INITIALLY managed? (x4)

A

Intravenous normal saline to correct fluid depletion, intravenous sodium bicarbonate to correct acidosis, intravenous insulin and dextrose to lower plasma potassium (by driving K+ ions back into cells) and DIALYSIS.

54
Q

PATIENT: elderly woman, lethargic, weakness and anorexia, clinically volume depleted resulting in severe hypotension, elevated plasma urea and creatinine makes diagnosis of renal failure. This is complicated by hyperkalaemia (K+), hyponatraemia (Na+), metabolic acidosis, and anaemia. ULTRASOUND shows two shrunken kidneys: How is our patient managed in the LONG TERM? (x4)

A
  • Remain on regular haemodialysis for severely renal-compromised patients.
  • Low potassium diet.
  • Erythropoietin injections to correct anaemia.
  • 1,25 Vitamin D supplements to prevent hyper-parathyroid bone disease.
55
Q

What is the problem of measuring plasma creatinine as an assessment of kidney function?

A

It varies between men and women, across different ethnicities and build of an individual.

Year 1 Urinary (8 decks)

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