Tutorial: Kidney function TBL Flashcards
If a patient is dehydrated, the filtrate present in which of these areas will have the highest osmolarity?
In Bowmann’s capsule, we know a lot of water is filtered together with salts so wont have highest osmolarity. We know a lot of salt is pumped out in thick ascending limb and a lot of water moves out of thin ascending limb into medullary interstitium. So when fluid goes through thin ascending limb a lot of water is reabsorbed so osmolarity is highest here.
After this, a lot of water as well salt is reabsrobed in ascending limb, DCT and collecting duct, so the osmolarity is not as high.
The urine samples of different patients were analysed using the urine osmolarity test. Whose sample is likely to have the highest osmolarity?
A and B are both types of diabetes insipidus and we know in both of these, ADH is not present or doesn’t have an effect, so not enough water is being reabsorbed so osmolarity will be low and there will be large urine volumes.
Normally urea from medulllary interstitium enters vasa recta via urea transport channels so it traps urea in interstitium but if this channel ie trapping mechanism isnt present then urea is free and could enter blood vessels or cortex so less osmolarity in interstitium so reduced water reabsorbtion. Need this trapping mecanism in order for urea recycling to occur.
In hepatic cirrhosis, blood vessels dilate so blood pressure goes down which is detected by barorecptors which send signals to hypothalamus for ADH release causing concentrated urine. Hepatic cirrhosis is an example of SIADH.
An athlete after finishing their London Marathon run drank 2L of distilled water. Which of the following statement is correct about their body fluids?
First increases volume of ECF and interstitial fluid
C would require time to occur as takes time for ECF and ICF to equilibrate.
The increase in plasma concentration of which solute will have no effect on ADH production?
Increase in plasma concentration of glucose and salt causes water to follow which is detected by osmoreceptors which then signal to the hypothalamus and stimulate the release of ADH.
For ethanol, it has direct effect on hypothalamus inhibiting ADH release.
Urea is soluble so is able to go through the semipermeable membrane so concentration is the same in both compartments, so no water movement so osmoreceptors don’t detect any change in osmolarity so no ADH release.
Sodium excretion is very limited (less than 1% of filtered load) and several mechanisms exist to tightly regulate it. Increasing sodium excretion reduces water retention. Potassium excretion can vary over a very large range (from 1 to 80% of filtered load). Why doesn’t this variability in potassium excretion have a marked effect on water balance?
Major extracellular ion is sodium, and it is the sodium that dictates the osmolarity.
Potassium is the major intracellular ion, so if change inside cells you change intracellular volume but the main change that is important is changes in extracellular volume.
Why do most diuretics increase potassium excretion?
Diuretics work by changing osmolarity is the tubules. Main effect is to reduce sodium uptake.
All diuretics cause more urine to be passing through the system, so they must increase the flow rate and one of the main factors for potassium excretion is flow. The ones that don’t increase urine flow that affect the later part of the nephron are potassium sparing.
Mr Holmes (65 years old, 75 Kg) is being treated with a loop diuretic and Mr Smith (66 years old, 74 Kg) with a thiazide diuretic for past 3 weeks (assume that the doses of the respective treatments allow an equivalent inhibition of [Na+] reabsorption). Both the individuals are drinking insufficient but equivalent amount of water. Which of the following statement is likely to be true?
Loop diuretics blocks sodium reabsorption in the loop of henle. Reduces movement of sodium into medullary interstitium so less water reabsorption occurs, but also increases sodium in urine so double effect.
Thiazide diuretics block sodium in distal convoluted tubule. If block this you increase sodium in urine, but you don’t decrease the medullary osmolarity.
Ms Sethi, a 25-year-old woman while trekking the Himalayas develops symptoms of dizziness and pain. Following data was collected for her: Blood pH = 7.6, [HCO3-] = 16mEq/L, PCO2 = 25mmHg. Identify her acid-base disorder.
[Normal values: Blood pH = 7.4, [HCO3-] = 24mEq/L, PCO2 = 40mmHg]
pH is high, she is suffering from alkalosis
For respiratory we want lower CO2
From bicarbonate we can see renal compensation has kicked in by bicarbonate excretion.
People at higher altitudes often develop this disorder
Ms Li, a 25-year-old healthy woman on her holiday develops stomach infection with nausea and vomiting. Following data was collected for her: Blood pH = 7.1, [HCO3-] = 16mEq/L, PCO2 = 30mmHg. Identify the compensatory mechanism being used by her body. [Normal values: Blood pH=7.4, [HCO3-] = 24mEq/L, PCO2 = 40mmHg]
You want pH to rise to cause CO2 to go down. So to achieve this, person hyperventilates.
Ms Juan, a 25-year-old woman with a history of asthma, on her holiday develops stomach infection with diarrhoea. Following data was collected for her: Blood pH = 7.1, [HCO3-] = 16mEq/L, PCO2 = 45mmHg. Identify her acid-base disorder.
[Normal values: Blood pH = 7.4, [HCO3-] = 24mEq/L, PCO2 = 40mmHg]
With an acidosis we want pCO2 to go down or bicarbonate to go up and as she has both these things happening it is mixed.
This can happen with asthma and diarrhoea.
First treat for diarrhoea and then renal compensation will kick in and her bicarbonate will go up and metabolic compensation can kick in.
