AMC MCQ - Australian Medical Council Multiple Choice Questions Renal and Endocrine Disorders Questions and Answers 1 — Questions and Answers
Question 1: A 22-year-old female with type 1 diabetes presents to the emergency department with confusion, nausea, and vomiting. Her blood glucose is 28 mmol/L, pH is 7.15, and serum ketones are elevated. She is tachycardic and hypotensive. What is the most appropriate initial intravenous fluid for resuscitation?
- 0.45% sodium chloride (Half-Normal Saline)
- 0.9% sodium chloride (Normal Saline) (Correct answer)
- 5% Dextrose in water
- Hartmann's solution (Lactated Ringer's)
Correct answer: 0.9% sodium chloride (Normal Saline)
The primary goal in the initial management of Diabetic Ketoacidosis (DKA) is to correct the profound dehydration and restore intravascular volume. According to Australian and international guidelines, 0.9% sodium chloride (Normal Saline) is the standard isotonic fluid of choice for initial resuscitation. [3, 16, 20] This helps to stabilize the patient's haemodynamic status. Other fluids like 0.45% NaCl may be used later once haemodynamics have improved, and dextrose-containing fluids are added only when the blood glucose level falls to prevent iatrogenic hypoglycaemia. [13, 20]
Question 2: A 35-year-old woman presents with a 3-month history of weight loss despite an increased appetite, palpitations, and heat intolerance. On examination, she has a fine tremor and a diffusely enlarged, non-tender thyroid gland. Which of the following patterns of thyroid function tests and antibodies would be most consistent with a diagnosis of Graves' disease?
- Low TSH, High Free T4, High Free T3, Positive Thyroid Peroxidase (TPO) antibodies
- High TSH, Low Free T4, Positive Thyroid Peroxidase (TPO) antibodies
- Low TSH, High Free T4, High Free T3, Positive TSH Receptor Antibodies (TRAb) (Correct answer)
- Normal TSH, Normal Free T4, High Thyroglobulin antibodies
Correct answer: Low TSH, High Free T4, High Free T3, Positive TSH Receptor Antibodies (TRAb)
Graves' disease is an autoimmune condition where TSH receptor antibodies (TRAb) stimulate the thyroid gland, leading to excessive production of thyroid hormones (T4 and T3). This results in primary hyperthyroidism, characterized by a suppressed Thyroid-Stimulating Hormone (TSH) due to negative feedback, and elevated levels of Free T4 and Free T3. The presence of TRAb is the specific pathogenic marker for Graves' disease. While TPO antibodies can also be positive, TRAb are more specific for the diagnosis.
Question 3: A 68-year-old man with Stage 4 Chronic Kidney Disease (eGFR 25 mL/min/1.73m²) due to diabetic nephropathy is found to have a haemoglobin of 95 g/L. His iron studies show a ferritin of 80 µg/L and a transferrin saturation (TSAT) of 15%. Other causes of anaemia have been excluded. According to Australian (KHA-CARI/KDIGO) guidelines, what is the most appropriate next step in managing his anaemia?
- Commence an erythropoiesis-stimulating agent (ESA) immediately.
- Administer a blood transfusion to raise haemoglobin above 100 g/L.
- Recheck haemoglobin and iron studies in 3 months.
- Initiate a trial of intravenous or oral iron therapy. (Correct answer)
Correct answer: Initiate a trial of intravenous or oral iron therapy.
According to Kidney Health Australia - Caring for Australasians with Renal Impairment (KHA-CARI) and KDIGO guidelines, iron deficiency must be corrected before initiating therapy with erythropoiesis-stimulating agents (ESAs). [14, 23, 27] The guidelines suggest a trial of iron therapy if TSAT is ≤30% and ferritin is ≤500 µg/L. [14, 27] In this patient, the TSAT of 15% and ferritin of 80 µg/L indicate iron deficiency. Therefore, the correct first step is to replete iron stores, which may improve the haemoglobin level without the need for ESAs.
Question 4: A 40-year-old patient is diagnosed with primary adrenal insufficiency (Addison's disease). Which of the following electrolyte patterns is most characteristically seen in this condition?
- Hyponatraemia, hyperkalaemia, metabolic acidosis (Correct answer)
- Hypernatraemia, hypokalaemia, metabolic alkalosis
- Hyponatraemia, hypokalaemia, metabolic acidosis
- Hypernatraemia, hyperkalaemia, metabolic alkalosis
Correct answer: Hyponatraemia, hyperkalaemia, metabolic acidosis
Primary adrenal insufficiency (Addison's disease) involves the destruction of the adrenal cortex, leading to a deficiency of both cortisol and aldosterone. Aldosterone deficiency impairs the kidney's ability to reabsorb sodium and excrete potassium and hydrogen ions. [5, 29] This results in the characteristic electrolyte disturbances of hyponatraemia (low sodium), hyperkalaemia (high potassium), and a non-anion gap metabolic acidosis. [5, 36]
Question 5: An 80-year-old man with small cell lung cancer is admitted with confusion. His serum sodium is 118 mmol/L. He is clinically euvolaemic. His serum osmolality is low, and his urine osmolality is inappropriately high (>100 mOsm/kg). His renal and thyroid function are normal. Which additional finding would support a diagnosis of SIADH?
- Low urine sodium concentration (<20 mmol/L)
- High urine sodium concentration (>30 mmol/L) (Correct answer)
- Presence of peripheral oedema
- Recent use of diuretic medication
Correct answer: High urine sodium concentration (>30 mmol/L)
The diagnosis of Syndrome of Inappropriate Antidiuretic Hormone (SIADH) requires a state of euvolaemic hyponatraemia with inappropriately concentrated urine (urine osmolality >100 mOsm/kg). [2, 45, 49] A key diagnostic feature is continued renal excretion of sodium, despite the hyponatraemia, leading to a urine sodium concentration that is typically >30-40 mmol/L. [4, 10, 21] This helps to distinguish SIADH from hypovolaemic hyponatraemia, where the kidneys would avidly conserve sodium, resulting in a low urine sodium concentration.
Question 6: A 75-year-old man develops an acute kidney injury (AKI) 48 hours after a hypotensive episode during surgery. His creatinine has risen from 80 µmol/L to 250 µmol/L and he is oliguric. A urinary catheter is in situ and draining freely. Which set of urinary indices would be most suggestive of pre-renal azotaemia rather than established acute tubular necrosis (ATN)?
- Urine osmolality <350 mOsm/kg, Urine sodium >40 mmol/L, FENa >2%
- Eosinophils present in the urine sediment
- Presence of red cell casts in urine microscopy
- Urine osmolality >500 mOsm/kg, Urine sodium <20 mmol/L, FENa <1% (Correct answer)
Correct answer: Urine osmolality >500 mOsm/kg, Urine sodium <20 mmol/L, FENa <1%
In pre-renal azotaemia, the kidney is hypoperfused but tubular function remains intact. The tubules respond appropriately by avidly reabsorbing sodium and water to conserve volume. This leads to a low urine sodium (<20 mmol/L), a low Fractional Excretion of Sodium (FENa <1%), and concentrated urine (osmolality >500 mOsm/kg). [1, 9] In contrast, in established Acute Tubular Necrosis (ATN), the damaged tubules lose their ability to concentrate urine and reabsorb sodium, resulting in a high urine sodium (>40 mmol/L), a high FENa (>2%), and isosthenuria (urine osmolality ~300-350 mOsm/kg). [34]
