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  • Question 1 - The last two segments of the nephrons are the distal convoluted tubule (DCT)...

    Incorrect

    • The last two segments of the nephrons are the distal convoluted tubule (DCT) and collecting duct (CD).

      Which cell reabsorbs sodium more in the late DCT and CD?

      Your Answer: Wedge cells

      Correct Answer: Principal cells

      Explanation:

      The main Na+ reabsorbing cells in the late distal convoluted tubule and collecting duct are the principal cells. These make up the majority of the tubular cells.

      The exchange is driven by the Na.K.ATPase pumps on the basolateral membrane.

    • This question is part of the following fields:

      • Physiology
      • Renal Physiology
      1
      Seconds
  • Question 2 - A 71-year-old woman presents with complaints of fatigue and worsening muscle weakness, and...

    Incorrect

    • A 71-year-old woman presents with complaints of fatigue and worsening muscle weakness, and blood tests done shows a potassium level of 2.4 mmol/L.

      Which is NOT a recognised cause of hypokalaemia?

      Your Answer: Excessive liquorice ingestion

      Correct Answer: Type 4 renal tubular acidosis

      Explanation:

      A plasma potassium less than 3.5 mmol/L defines hypokalaemia.

      Excessive liquorice ingestion causes hypermineralocorticoidism and leads to hypokalaemia.

      Gitelman’s syndrome causes metabolic alkalosis with hypokalaemia and hypomagnesaemia. It is an inherited defect of the distal convoluted tubules.

      Bartter’s syndrome causes hypokalaemic alkalosis. It is a rare inherited defect in the ascending limb of the loop of Henle.

      Type 1 and 2 renal tubular acidosis both cause hypokalaemia

      Type 4 renal tubular acidosis causes hyperkalaemia.

    • This question is part of the following fields:

      • Physiology
      • Renal Physiology
      4
      Seconds
  • Question 3 - An ambulance transports a 40-year-old man to the hospital. He ingested a significant...

    Incorrect

    • An ambulance transports a 40-year-old man to the hospital. He ingested a significant amount of aspirin.

      In the early stages of an aspirin overdose, which form of acid-base problem should you anticipate? 

      Your Answer:

      Correct Answer: Respiratory alkalosis

      Explanation:

      When you take too much aspirin, you have a mix of respiratory alkalosis and metabolic acidosis. Respiratory centre stimulation produces hyperventilation and respiratory alkalosis in the early phases. The direct acid actions of aspirin tend to create a higher anion gap metabolic acidosis in the latter phases.
      Below summarizes some of the most common reasons of acid-base abnormalities:

      Respiratory alkalosis:
      – Hyperventilation (e.g. anxiety, pain, fever)
      – Pulmonary embolism
      – Pneumothorax
      – CNS disorders (e.g. CVA, SAH, encephalitis)
      – High altitude
      – Pregnancy
      – Early stages of aspirin overdose

      Respiratory acidosis:
      – COPD
      – Life-threatening asthma
      – Pulmonary oedema
      – Respiratory depression (e.g. opiates, benzodiazepines)
      – Neuromuscular disease (e.g. Guillain-Barré syndrome, muscular dystrophy
      – Incorrect ventilator settings (hypoventilation)
      – Obesity

      Metabolic alkalosis:
      – Vomiting
      – Cardiac arrest
      – Multi-organ failure
      – Cystic fibrosis
      – Potassium depletion (e.g. diuretic usage)
      – Cushing’s syndrome
      – Conn’s syndrome

      Metabolic acidosis (with raised anion gap):
      – Lactic acidosis (e.g. hypoxaemia, shock, sepsis, infarction)
      – Ketoacidosis (e.g. diabetes, starvation, alcohol excess)
      – Renal failure
      – Poisoning (e.g. late stages of aspirin overdose, methanol, ethylene glycol)

      Metabolic acidosis (with normal anion gap):
      – Renal tubular acidosis
      – Diarrhoea
      – Ammonium chloride ingestion
      – Adrenal insufficiency

    • This question is part of the following fields:

      • Physiology
      • Renal Physiology
      0
      Seconds
  • Question 4 - Polyuria and polydipsia develop in a patient with a history of affective disorders...

    Incorrect

    • Polyuria and polydipsia develop in a patient with a history of affective disorders illness who has been on long-term lithium. She has a fluid deprivation test because she is suspected of having nephrogenic diabetic insipidus.

      Which of the following urine osmolality findings would be the most reliable in confirming the diagnosis? 

      Your Answer:

      Correct Answer:

      Explanation:

      The inability to produce concentrated urine is a symptom of diabetes insipidus. Excessive thirst, polyuria, and polydipsia are all symptoms of this condition. There are two forms of diabetes insipidus: Nephrogenic diabetes insipidus and cranial (central) diabetes insipidus.

      A lack of ADH causes cranial diabetic insipidus. Patients with cranial diabetes insipidus can have a urine output of up to 10-15 litres per 24 hours, however most patients can maintain normonatraemia with proper fluid consumption. Thirty percent of cases are idiopathic, while another thirty percent are caused by head injuries. Neurosurgery, brain tumours, meningitis, granulomatous disease (e.g. sarcoidosis), and medicines like naloxone and phenytoin are among the other reasons. There is also a very rare hereditary type that is linked to diabetes, optic atrophy, nerve deafness, and bladder atonia.

      Renal resistance to the action of ADH causes nephrogenic diabetes insipidus. Urine output is significantly increased, as it is in cranial diabetes insipidus. Secondary polydipsia can keep serum sodium levels stable or raise them. Chronic renal dysfunction, metabolic diseases (e.g., hypercalcaemia and hypokalaemia), and medications, such as long-term lithium use and demeclocycline, are all causes of nephrogenic diabetes insipidus.

      The best test to establish if a patient has diabetes insipidus vs another cause of polydipsia is the water deprivation test, commonly known as the fluid deprivation test. It also aids in the distinction between cranial and nephrogenic diabetes insipidus. Weight, urine volume, urine osmolality, and serum osmolality are all measured after patients are denied water for up to 8 hours. At the end of the 8-hour period, 2 micrograms of IM desmopressin is given, and measures are taken again at 16 hours.

      The following are the way results are interpreted:
      Urine osmolality after fluid deprivation : Urine osmolality after IM desmopressin
      Cranial diabetes insipidus
      <300 mosmol/kg : >800 mosmol/kg
      Nephrogenic diabetes insipidus
      <300 mosmol/kg : <300 mosmol/kg
      Primary polydipsia
      >800 mosmol/kg : >800 mosmol/kg

    • This question is part of the following fields:

      • Physiology
      • Renal Physiology
      0
      Seconds
  • Question 5 - The proximal convoluted tubule (PCT) is the first part of the renal tubule...

    Incorrect

    • The proximal convoluted tubule (PCT) is the first part of the renal tubule and lies in the renal cortex. The bulk of reabsorption of solute occurs is the PCT and 100% of glucose is reabsorbed here.

      Which of the following is the mechanism of glucose reabsorption in the PCT?

      Your Answer:

      Correct Answer: Secondary active transport

      Explanation:

      Glucose reabsorption occurs exclusively in the proximal convoluted tubule by secondary active transport through the Na.Glu co-transporters, driven by the electrochemical gradient for sodium.
      The co-transporters transport two sodium ions and one glucose molecule across the apical membrane, and the glucose subsequently crosses the basolateral membrane by facilitated diffusion.

    • This question is part of the following fields:

      • Physiology
      • Renal Physiology
      0
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  • Question 6 - The arterial blood gas (ABG) of a 56-year-old woman shows type A lactic...

    Incorrect

    • The arterial blood gas (ABG) of a 56-year-old woman shows type A lactic acidosis.

      What is the most likely cause of her lactic acidosis?

      Your Answer:

      Correct Answer: Left ventricular failure

      Explanation:

      Lactic acidosis is a common finding in critically ill patients and commonly associated with other serious underlying pathologies. It occurs when pH is <7.35 and lactate is >5 mmol/L. Anion gap is increased in lactic acidosis.

      Acquired lactic acidosis is classified into two subtypes:
      Type A: lactic acidosis due to tissue hypoxia and
      Type B: due to non-hypoxic processes affecting the production and elimination of lactate

      Some causes of type A and type B lactic acidosis include:
      Type A lactic acidosis
      Left ventricular failure
      Severe anaemia
      Shock (including septic shock)
      Asphyxia
      Cardiac arrest
      CO poisoning
      Respiratory failure
      Severe asthma and COPD

      Type B lactic acidosis:
      Regional hypoperfusion
      Renal failure
      Liver failure
      Sepsis (non-hypoxic sepsis)
      Thiamine deficiency
      Alcoholic ketoacidosis
      Diabetic ketoacidosis
      Cyanide poisoning
      Methanol poisoning
      Biguanide poisoning

    • This question is part of the following fields:

      • Physiology
      • Renal Physiology
      0
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  • Question 7 - Urine flow rate = 2 ml/min
    Urine concentration of creatinine = 18 mg/ml
    Plasma...

    Incorrect

    • Urine flow rate = 2 ml/min
      Urine concentration of creatinine = 18 mg/ml
      Plasma concentration of creatinine = 0.25 mg/ml

      What is the estimated glomerular filtration rate (eGFR)?

      Your Answer:

      Correct Answer: 144 ml/min

      Explanation:

      GFR can be estimated by:
      GFR = UCr x V / PCr
      Where:
      UCr = urine concentration of creatinine
      PCr = plasma concentration of creatinine
      V = rate of urine flow

      In this case GFR = (18 x 2) / 0.25 = 144 ml/min

      Note: Creatinine is used to estimate GFR because it is an organic base naturally produced by muscle breakdown, it is freely filtered at the glomerulus, it is not reabsorbed from the nephron, it is not produced by the kidney, it is not toxic, and it doesn’t alter GFR.

    • This question is part of the following fields:

      • Physiology
      • Renal Physiology
      0
      Seconds
  • Question 8 - A 42-year-old male patient, presenting with polyuria and polydipsia symptoms had normal blood...

    Incorrect

    • A 42-year-old male patient, presenting with polyuria and polydipsia symptoms had normal blood test results. Upon interview, he had mentioned being in a car accident in which he had a head injury. His polyuria and polydipsia symptoms are most likely associated with which of the following conditions?

      Your Answer:

      Correct Answer: Cranial diabetes insipidus

      Explanation:

      Polydipsia is the feeling of extreme thirstiness. It is often linked to polyuria, which is a urinary condition that causes a person to urinate excessively. The cycle of these two processes makes the body feel a constant need to replace the fluids lost in urination. In healthy adults, a 3 liter urinary output per day is considered normal. A person with polyuria can urinate up to 15 liters of urine per day. Both of these conditions are classic signs of diabetes.

      The other options are also types of diabetes, except for psychogenic polydipsia (PPD), which is the excessive volitional water intake seen in patients with severe mental illness or developmental disability. However, given the patient’s previous head injury, the most likely diagnosis is cranial diabetes insipidus.

      By definition, cranial diabetes insipidus is caused by damage to the hypothalamus or pituitary gland after an infection, operation, brain tumor, or head injury. And the patient’s history confirms this diagnosis. To define the other choices, nephrogenic diabetes insipidus happens when the structures in the kidneys are damaged and results in an inability to properly respond to antidiuretic hormone.

      Kidney damage can be caused by an inherited (genetic) disorder or a chronic kidney disorder. As with cranial diabetes insipidus, nephrogenic diabetes insipidus can also cause an elevated urine output.

      Diabetes mellitus is classified into two types, and the main difference between them is that type 1 diabetes is a genetic disorder, and type 2 diabetes is diet-related and develops over time. Type 1 diabetes is also known as insulin-dependent diabetes, in which the pancreas produces little or no insulin. Type 2 diabetes is termed insulin resistance, as cells don’t respond customarily to insulin.

    • This question is part of the following fields:

      • Physiology
      • Renal Physiology
      0
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  • Question 9 - A 60-year-old man diagnosed with chronic kidney disease has an elevated creatinine level...

    Incorrect

    • A 60-year-old man diagnosed with chronic kidney disease has an elevated creatinine level and a reduced glomerular filtration rate (GFR).

      Which statement concerning glomerular filtration is true?

      Your Answer:

      Correct Answer: Creatinine is freely filtered at the glomerulus

      Explanation:

      Glomerular filtration is a passive process. It depends on the net hydrostatic pressure across the glomerular capillaries, the oncotic pressure, and the intrinsic permeability of the glomerulus.

      The mean values for glomerular filtration rate (GFR) in young adults are 130 ml/min/1.73m2 in males and 120 ml/min/1.73m2in females.

      The GFR declines with age after the age of 40 at a rate of approximately 1 ml/min/year.

      The Cockcroft and Gault formula overestimates creatinine in obese patients. This is because their endogenous creatinine production is less than that predicted by overall body weight.

      Creatinine is used in the estimation of GFR because it is naturally produced by muscle breakdown, not toxic, not produced by the kidney, freely filtered at the glomerulus, not reabsorbed from the nephron, and does not alter GFR.

    • This question is part of the following fields:

      • Physiology
      • Renal Physiology
      0
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  • Question 10 - Which statement accurately describes the osmolality in the various parts of the Henle...

    Incorrect

    • Which statement accurately describes the osmolality in the various parts of the Henle Loop?

      Your Answer:

      Correct Answer: The osmolality of fluid in the descending loop equals that of the peritubular fluid

      Explanation:

      The Loop of Henle connects the proximal tubule to the distal convoluted tubule and lies parallel to the collecting ducts. It consists of three major segments, including the descending thin limb, the ascending thin limb, and the ascending thick limb. These segments are differentiated based on structure, anatomic location, and function.

      The main function of the loop of Henle is to recover water and sodium chloride from urine. When fluid enters the loop of Henle, it has an osmolality of approximately 300 mOsm, and the main solute is sodium.

      The thin descending limb has a high water permeability but a low ion permeability. Because it lacks solute transporters, it cannot reabsorb sodium. Aquaporin 1 (AQP1) channels are used to passively absorb water in this area. The peritubular fluid becomes increasingly concentrated as the loop descends into the medulla, causing water to osmose out of the tubule. The tubular fluid in this area now equalizes to the osmolality of the peritubular fluid, to a maximum of approximately 1200 mOsm in a long medullary loop of Henle and 600 mOsm in a short cortical loop of Henle.

      The thin ascending limb is highly permeable to ions and impermeable to water. It allows the passive movement of sodium, chloride, and urea down their concentration gradients, so urea enters the tubule and sodium and chloride leave. Reabsorption occurs paracellularly due to the difference in osmolarity between the tubule and the interstitium.

      The thick ascending limb is also impermeable to water but actively transports sodium, potassium, and chloride out of the tubular fluid. The osmolality of the tubular fluid is lower compared to the surrounding peritubular fluid. This area is water impermeable. This results in tubular fluid leaving the loop of Henle with an osmolality of approximately 100 mOsm, which is lower than the osmolality of the fluid entering the loop, and urea being the solute.

    • This question is part of the following fields:

      • Physiology
      • Renal Physiology
      0
      Seconds

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