A 68-year-old man with prostate cancer on abiraterone presents with muscle weakness and palpitations. ECG shows flattened T waves and prominent U waves. Blood tests reveal: sodium 138 mmol/L, potassium 2.4 mmol/L, bicarbonate 32 mmol/L, chloride 92 mmol/L. Arterial blood gas shows pH 7.52, pCO2 5.8 kPa. What is the underlying mechanism of his electrolyte disturbance?
Q42
A 56-year-old woman with type 2 diabetes and hypertension presents with fatigue and ankle swelling. Blood results show: creatinine 145 μmol/L, eGFR 38 mL/min/1.73m², HbA1c 62 mmol/mol. Urinalysis reveals albumin:creatinine ratio 45 mg/mmol. Which classification of chronic kidney disease does this patient have?
Q43
A 42-year-old man with a history of gout is brought to the emergency department by ambulance after a grand mal seizure. He recently started chemotherapy for Burkitt lymphoma. Blood tests show: sodium 136 mmol/L, potassium 7.2 mmol/L, urea 28 mmol/L, creatinine 420 μmol/L (baseline 95 μmol/L), phosphate 2.8 mmol/L, calcium 1.85 mmol/L, urate 780 μmol/L. ECG shows peaked T waves. What is the most appropriate immediate management?
Q44
A 77-year-old man with CKD stage 3b (eGFR 42 mL/min/1.73m²) presents with 2 days of confusion. Medications include amlodipine, bisoprolol, furosemide, and sodium valproate for epilepsy. Blood tests reveal: sodium 128 mmol/L, potassium 3.8 mmol/L, urea 8.2 mmol/L, creatinine 156 µmol/L (baseline 148 µmol/L), glucose 5.4 mmol/L, serum osmolality 268 mOsm/kg, urine osmolality 520 mOsm/kg, urine sodium 58 mmol/L. Clinical examination shows mild peripheral oedema, BP 158/92 mmHg. Chest X-ray and CT head are normal. Which additional test would be most helpful in determining the underlying cause?
Q45
A 39-year-old woman presents to the emergency department with severe colicky right flank pain radiating to the groin, nausea, and visible haematuria. Non-contrast CT KUB reveals a 5mm calculus at the right vesicoureteric junction and a density measurement of 1200 Hounsfield units. Creatinine is 68 µmol/L, she is apyrexial, and there is no hydronephrosis. Pain is controlled with diclofenac. She wishes to know the likelihood of spontaneous passage and optimal management strategy.
Q46
A 63-year-old man with CKD stage 5 (eGFR 11 mL/min/1.73m²) is being counselled about renal replacement therapy options. He lives alone, works part-time, and wishes to maintain independence. He has well-controlled diabetes, previous myocardial infarction with good LV function, and a BMI of 32 kg/m². He expresses concern about needle phobia and wishes to minimize hospital visits. Which renal replacement modality would be most appropriate to recommend?
Q47
A 52-year-old man undergoes cadaveric renal transplantation for end-stage renal disease secondary to IgA nephropathy. He receives basiliximab induction and is maintained on tacrolimus, mycophenolate, and prednisolone. On post-operative day 5, his creatinine rises from 145 µmol/L to 265 µmol/L. Urine output drops to 0.4 mL/kg/hr. Tacrolimus level is 8 µg/L (target 10-15). Transplant ultrasound shows normal perfusion but mild collecting system dilatation. What is the most appropriate next investigation?
Q48
A 71-year-old woman with diabetes and hypertension presents with progressive confusion over 3 days. Blood tests show: sodium 118 mmol/L, potassium 4.2 mmol/L, urea 3.8 mmol/L, creatinine 76 µmol/L, glucose 6.8 mmol/L, serum osmolality 248 mOsm/kg, urine osmolality 445 mOsm/kg, urine sodium 52 mmol/L. She takes bendroflumethiazide, ramipril, atorvastatin, and metformin. Clinical examination shows moist mucous membranes, no oedema, and blood pressure 138/82 mmHg. What is the most likely cause of her hyponatraemia?
Q49
A 59-year-old man with CKD stage 4 (eGFR 22 mL/min/1.73m²) secondary to hypertensive nephropathy is reviewed in clinic. Blood tests show: haemoglobin 96 g/L, MCV 88 fL, ferritin 180 µg/L, transferrin saturation 22%, serum iron 8 µmol/L. He reports increasing fatigue affecting his daily activities. What is the most appropriate next step in managing his anaemia?
Q50
A 48-year-old man with no significant past medical history presents with a 4mm distal ureteric calculus causing mild hydronephrosis. He has mild flank discomfort but is systemically well with normal renal function (creatinine 82 µmol/L), no fever, and white cell count 7.2 × 10⁹/L. Stone analysis from a previous episode showed calcium oxalate composition. Which investigation would be most useful in identifying a metabolic cause for recurrent stone formation?
Renal & Urology UK Medical PG Practice Questions and MCQs
Question 41: A 68-year-old man with prostate cancer on abiraterone presents with muscle weakness and palpitations. ECG shows flattened T waves and prominent U waves. Blood tests reveal: sodium 138 mmol/L, potassium 2.4 mmol/L, bicarbonate 32 mmol/L, chloride 92 mmol/L. Arterial blood gas shows pH 7.52, pCO2 5.8 kPa. What is the underlying mechanism of his electrolyte disturbance?
A. Increased aldosterone activity due to inhibition of 17α-hydroxylase (Correct Answer)
B. Primary hyperaldosteronism due to adrenal adenoma
C. Renal tubular acidosis type 1
D. Gastrointestinal potassium loss
E. Insulin-induced intracellular potassium shift
Explanation: ***Increased aldosterone activity due to inhibition of 17α-hydroxylase***- **Abiraterone** inhibits the **CYP17A1** enzyme, blocking the conversion of pregnenolone and progesterone into cortisol precursors, which leads to a compensatory increase in **ACTH**.- Elevated **ACTH** drives the accumulation of mineralocorticoid precursors like **11-deoxycorticosterone**, resulting in **hypokalemia**, **metabolic alkalosis**, and clinical symptoms such as muscle weakness and palpitations.*Primary hyperaldosteronism due to adrenal adenoma*- While this condition presents with **hypokalemia** and **metabolic alkalosis**, the direct cause in this patient is his **abiraterone** therapy.- Primary hyperaldosteronism is typically characterized by **suppressed renin activity**, which differs from the mechanism induced by abiraterone where ACTH drives mineralocorticoid excess.*Renal tubular acidosis type 1*- **Type 1 (Distal) RTA** is characterized by **metabolic acidosis** (low bicarbonate and pH), which contradicts the patient's **metabolic alkalosis** (high bicarbonate and pH).- Although hypokalemia can be present, the primary acid-base derangement is opposite to that observed in this case.*Gastrointestinal potassium loss*- **Gastrointestinal potassium loss**, such as from diarrhea, typically causes a **hyperchloremic metabolic acidosis** due to bicarbonate loss.- While severe vomiting can cause metabolic alkalosis and hypokalemia, the patient's specific medication (**abiraterone**) points to a more direct endocrine mechanism.*Insulin-induced intracellular potassium shift*- Insulin causes a temporary shift of **potassium into cells**, leading to **transient hypokalemia**.- This mechanism does not account for the profound and sustained **metabolic alkalosis** or the presence of prominent U waves and flattened T waves, which suggest chronic potassium depletion.
Question 42: A 56-year-old woman with type 2 diabetes and hypertension presents with fatigue and ankle swelling. Blood results show: creatinine 145 μmol/L, eGFR 38 mL/min/1.73m², HbA1c 62 mmol/mol. Urinalysis reveals albumin:creatinine ratio 45 mg/mmol. Which classification of chronic kidney disease does this patient have?
A. CKD G3a A3
B. CKD G3b A3 (Correct Answer)
C. CKD G3a A2
D. CKD G3b A2
E. CKD G2 A3
Explanation: ***CKD G3b A3***
- The patient's **eGFR of 38 mL/min/1.73m²** falls into the **G3b category**, which defines a moderate-to-severe reduction in kidney function (range **30–44 mL/min/1.73m²**).
- An albumin:creatinine ratio (ACR) of **45 mg/mmol** is categorized as **A3**, representing **severely increased albuminuria** (>30 mg/mmol).
*CKD G3a A3*
- **G3a** classification is reserved for patients with an eGFR between **45–59 mL/min/1.73m²**, which is higher than this patient's level of 38.
- While the albuminuria (A3) is correct, the **filtration stage (G3a vs G3b)** is underestimated for the patient's actual eGFR.
*CKD G3a A2*
- This option incorrectly states both the **eGFR stage (G3a)** and the **albuminuria stage (A2)** based on the patient's values.
- **A2** represents **moderately increased albuminuria** (3–30 mg/mmol), whereas this patient's ACR of 45 mg/mmol indicates **severely increased albuminuria (A3)**.
*CKD G3b A2*
- While the **G3b** stage correctly identifies the eGFR range of **30–44 mL/min/1.73m²**, the albuminuria stage (A2) is incorrect.
- **A2** is for an ACR of **3–30 mg/mmol**, failing to account for the patient's higher clinical value of **45 mg/mmol**, which is **A3**.
*CKD G2 A3*
- **G2** defines a **mildly decreased GFR** of **60–89 mL/min/1.73m²**, which is significantly higher than this patient's eGFR of 38.
- This stage would imply much better preserved kidney function than what is demonstrated by her **creatinine of 145 μmol/L** and **eGFR of 38**.
Question 43: A 42-year-old man with a history of gout is brought to the emergency department by ambulance after a grand mal seizure. He recently started chemotherapy for Burkitt lymphoma. Blood tests show: sodium 136 mmol/L, potassium 7.2 mmol/L, urea 28 mmol/L, creatinine 420 μmol/L (baseline 95 μmol/L), phosphate 2.8 mmol/L, calcium 1.85 mmol/L, urate 780 μmol/L. ECG shows peaked T waves. What is the most appropriate immediate management?
A. Intravenous calcium gluconate 10 mL of 10% solution (Correct Answer)
B. Intravenous rasburicase 0.2 mg/kg
C. Intravenous sodium bicarbonate 8.4% solution
D. Emergency haemodialysis
E. Intravenous allopurinol 200 mg
Explanation: ***Intravenous calcium gluconate 10 mL of 10% solution***
- This patient has severe **hyperkalaemia (7.2 mmol/L)** with **ECG changes (peaked T waves)**, which is a life-threatening emergency requiring immediate **myocardial membrane stabilization**.
- Calcium gluconate acts within minutes to reduce the risk of **ventricular arrhythmias** and cardiac arrest, though it does not lower the serum potassium level itself.
*Intravenous rasburicase 0.2 mg/kg*
- While rasburicase is the preferred agent for managing **hyperuricaemia** in **Tumour Lysis Syndrome**, it does not address the immediate cardiac risk from hyperkalaemia.
- It acts by converting **uric acid** to allantoin, which is more soluble, but it will not stabilize the heart or lower potassium levels.
*Intravenous sodium bicarbonate 8.4% solution*
- Sodium bicarbonate can sometimes be used to shift potassium intracellularly in the setting of **metabolic acidosis**, but it is not the first-line treatment for **cardiac stabilization**.
- Routine use is generally avoided unless severe acidosis is present, as it can worsen **hypocalcaemia** by increasing calcium binding to albumin.
*Emergency haemodialysis*
- Haemodialysis is the **definitive treatment** for the severe electrolyte derangements and **Acute Kidney Injury (AKI)** seen in this patient's Tumour Lysis Syndrome.
- However, it cannot be initiated instantly; **calcium gluconate** must be given first to protect the heart while the dialysis team and equipment are being prepared.
*Intravenous allopurinol 200 mg*
- Allopurinol is used to block the production of **uric acid** by inhibiting **xanthine oxidase**, primarily as prophylaxis rather than acute treatment.
- It is ineffective at reducing existing high levels of uric acid and has no role in the emergency management of **hyperkalaemic ECG changes**.
Question 44: A 77-year-old man with CKD stage 3b (eGFR 42 mL/min/1.73m²) presents with 2 days of confusion. Medications include amlodipine, bisoprolol, furosemide, and sodium valproate for epilepsy. Blood tests reveal: sodium 128 mmol/L, potassium 3.8 mmol/L, urea 8.2 mmol/L, creatinine 156 µmol/L (baseline 148 µmol/L), glucose 5.4 mmol/L, serum osmolality 268 mOsm/kg, urine osmolality 520 mOsm/kg, urine sodium 58 mmol/L. Clinical examination shows mild peripheral oedema, BP 158/92 mmHg. Chest X-ray and CT head are normal. Which additional test would be most helpful in determining the underlying cause?
A. Chest CT to exclude malignancy
B. Thyroid function tests (Correct Answer)
C. Serum cortisol and ACTH stimulation test
D. Serum valproate level
E. Brain natriuretic peptide (BNP)
Explanation: ***Thyroid function tests***
- This patient presents with **hypotonic hyponatraemia** (Na 128, serum osmolality 268) and **inappropriately concentrated urine** (urine osmolality 520, urine Na 58), consistent with **SIADH** or a similar syndrome of impaired free water excretion.
- **Hypothyroidism** is a well-known, albeit rare, cause of hyponatraemia due to impaired free water excretion and can present with confusion, making **thyroid function tests** essential to exclude this reversible cause.
*Serum cortisol and ACTH stimulation test*
- **Adrenal insufficiency** can cause hyponatraemia, but it typically presents with **hypotension** and often **hyperkalaemia**.
- The patient's **blood pressure is elevated (158/92 mmHg)** and **potassium is normal**, which makes adrenal insufficiency a less likely primary cause in this scenario.
*Serum valproate level*
- **Sodium valproate** is a known pharmacological cause of SIADH, but a serum level would confirm exposure rather than definitively establishing it as the *sole* or *primary* cause of the hyponatraemia, especially when other conditions like hypothyroidism need to be ruled out.
- Management of valproate-induced hyponatraemia usually involves dose adjustment or cessation, and the level itself doesn't guide the initial diagnostic workup for *other* potential underlying causes.
*Brain natriuretic peptide (BNP)*
- **Heart failure** causes **hypervolemic hyponatraemia**, where the body attempts to retain fluid, leading to **low urine sodium** (<20 mmol/L) due to avid renal sodium reabsorption.
- This patient has a **high urine sodium (58 mmol/L)** and a **normal chest X-ray**, which makes heart failure an unlikely primary cause of this specific pattern of hyponatraemia.
*Chest CT to exclude malignancy*
- While **malignancies** (e.g., small cell lung cancer) are classic causes of **paraneoplastic SIADH**, a **normal chest X-ray** reduces its immediate diagnostic priority.
- It is typically considered after more common or readily reversible endocrine causes, like hypothyroidism, have been evaluated, especially given the patient's age and general presentation.
Question 45: A 39-year-old woman presents to the emergency department with severe colicky right flank pain radiating to the groin, nausea, and visible haematuria. Non-contrast CT KUB reveals a 5mm calculus at the right vesicoureteric junction and a density measurement of 1200 Hounsfield units. Creatinine is 68 µmol/L, she is apyrexial, and there is no hydronephrosis. Pain is controlled with diclofenac. She wishes to know the likelihood of spontaneous passage and optimal management strategy.
A. Extracorporeal shockwave lithotripsy within 48 hours offers best stone-free rate for distal stones
B. The stone will likely pass spontaneously; discharge with analgesia and alpha-blocker, review in 4 weeks (Correct Answer)
C. Stone density >1000 HU indicates calcium composition; immediate ureteroscopy is recommended
D. Conservative management unlikely to succeed; admit for intervention within 48 hours
E. The location suggests spontaneous passage unlikely; arrange elective ureteroscopy in 2 weeks
Explanation: ***The stone will likely pass spontaneously; discharge with analgesia and alpha-blocker, review in 4 weeks***- Ureteral stones **≤5mm** at the **vesicoureteric junction (VUJ)** have a high probability (approximately 70-80%) of **spontaneous passage** within four weeks.- Management of uncomplicated renal colic involves outpatient **medical expulsive therapy (MET)** with an **alpha-blocker** (e.g., tamsulosin), adequate analgesia, and follow-up to confirm stone clearance.*Extracorporeal shockwave lithotripsy within 48 hours offers best stone-free rate for distal stones*- **ESWL** is generally less effective for stones located in the **distal ureter** compared to stones in the upper ureter or kidney due to shielding by the pelvic bone.- Immediate intervention is not recommended for an **uncomplicated 5mm stone** where conservative management is the first-line approach with a high success rate.*Stone density >1000 HU indicates calcium composition; immediate ureteroscopy is recommended*- A high **Hounsfield Unit (HU)** value, such as 1200, suggests a dense stone (e.g., **calcium oxalate monohydrate**), but stone hardness alone does not mandate immediate surgical intervention for stable patients.- **Ureteroscopy** is a definitive treatment if conservative management fails, but it is not indicated as an initial step for small, non-obstructive, uncomplicated stones.*Conservative management unlikely to succeed; admit for intervention within 48 hours*- **Admission** and urgent intervention are typically reserved for complicated cases such as intractable pain, **urosepsis (fever, signs of infection)**, or **acute kidney injury** due to obstruction, none of which are present.- The patient's pain is well-controlled with **NSAIDs**, and there is no evidence of hydronephrosis or infection, making conservative management appropriate.*The location suggests spontaneous passage unlikely; arrange elective ureteroscopy in 2 weeks*- While the **vesicoureteric junction (VUJ)** is a common site for stones to lodge, a 5mm stone that has reached this point still has a good chance of spontaneous passage, especially with MET.- **Elective ureteroscopy** is usually considered for stones that fail to pass after an adequate trial (e.g., 4-6 weeks) of conservative management or for larger stones, not prematurely after 2 weeks for an uncomplicated 5mm stone.
Question 46: A 63-year-old man with CKD stage 5 (eGFR 11 mL/min/1.73m²) is being counselled about renal replacement therapy options. He lives alone, works part-time, and wishes to maintain independence. He has well-controlled diabetes, previous myocardial infarction with good LV function, and a BMI of 32 kg/m². He expresses concern about needle phobia and wishes to minimize hospital visits. Which renal replacement modality would be most appropriate to recommend?
A. In-centre haemodialysis three times per week
B. Automated peritoneal dialysis (APD) (Correct Answer)
C. Conservative kidney management without dialysis
D. Continuous ambulatory peritoneal dialysis (CAPD)
E. Home haemodialysis
Explanation: ***Automated peritoneal dialysis (APD)*** - **APD** is the most suitable as it uses an overnight **cycler machine**, allowing the patient to remain independent and continue his **part-time work** during the day. - It specifically addresses his **needle phobia** by using a **Tenckhoff catheter** instead of fistula cannulation and significantly **reduces hospital visits** (usually once per month).*In-centre haemodialysis three times per week* - This modality requires frequent **hospital visits** and significant travel time, which contradicts the patient's desire for **independence** and minimized clinical contact. - It involves regular **needle cannulation** of an arteriovenous fistula or graft, which is incompatible with the patient's severe **needle phobia**.*Conservative kidney management without dialysis* - This is typically reserved for elderly patients with significant **frailty**, multiple severe comorbidities, or poor functional status who do not wish to undergo RRT. - Given his **good LV function**, active work status, and lack of severe cognitive impairment, choosing this would prematurely forfeit the potential **survival benefit** of dialysis.*Continuous ambulatory peritoneal dialysis (CAPD)* - CAPD requires performing multiple **manual exchanges** throughout the day, which can be disruptive for a patient who is still **working part-time**. - While it avoids needles, it offers less **lifestyle flexibility** and daytime freedom compared to the automated machinery used in **APD**.*Home haemodialysis* - Although it provides high levels of independence and home-based care, it explicitly requires **self-cannulation** with needles multiple times per week. - This is generally contraindicated or highly stressful for patients with a documented, significant **needle phobia**.
Question 47: A 52-year-old man undergoes cadaveric renal transplantation for end-stage renal disease secondary to IgA nephropathy. He receives basiliximab induction and is maintained on tacrolimus, mycophenolate, and prednisolone. On post-operative day 5, his creatinine rises from 145 µmol/L to 265 µmol/L. Urine output drops to 0.4 mL/kg/hr. Tacrolimus level is 8 µg/L (target 10-15). Transplant ultrasound shows normal perfusion but mild collecting system dilatation. What is the most appropriate next investigation?
A. Transplant biopsy (Correct Answer)
B. Nuclear medicine MAG3 renogram
C. CT angiography of transplant renal artery
D. Increase tacrolimus dose and recheck level in 48 hours
E. Urinary BK virus PCR
Explanation: ***Transplant biopsy***
- A **transplant biopsy** is the **gold standard** for diagnosing acute graft dysfunction early post-transplant, definitively distinguishing between **acute cellular rejection (ACR)**, **antibody-mediated rejection (AMR)**, and **acute tubular necrosis (ATN)**.
- This patient's rapidly rising creatinine and oliguria on day 5, despite a subtherapeutic tacrolimus level, warrant histological confirmation to guide appropriate and specific treatment.
*Nuclear medicine MAG3 renogram*
- This test assesses **perfusion** and **urinary outflow**, which can be helpful for diagnosing **urine leaks** or significant obstruction that might not be fully evident on ultrasound.
- However, the **transplant ultrasound** already showed normal perfusion and only mild collecting system dilatation, suggesting less utility compared to a biopsy for differentiating the underlying cause of acute kidney injury.
*CT angiography of transplant renal artery*
- This investigation is indicated for suspected **renal artery stenosis** or **thrombosis**, which would typically present with abnormal graft perfusion on ultrasound or severe hypertension.
- Since the **ultrasound showed normal perfusion**, and the use of **intravenous contrast** carries a risk of **nephrotoxicity** in a patient with a failing graft, it is not the most appropriate initial investigation.
*Increase tacrolimus dose and recheck level in 48 hours*
- While the **tacrolimus level is subtherapeutic** (8 µg/L vs. target 10-15 µg/L), increasing the dose empirically without a definitive diagnosis is risky, as calcineurin inhibitors can exacerbate **acute tubular necrosis (ATN)**.
- Relying on a dose adjustment delays the critical diagnosis of **acute rejection**, which requires prompt and specific immunosuppressive therapy beyond simply increasing maintenance medication.
*Urinary BK virus PCR*
- **BK virus-associated nephropathy (BKVAN)** typically presents much later in the post-transplant course, usually between **3 to 12 months** after transplantation, when immunosuppression is more established.
- Investigating for BK virus on **post-operative day 5** is premature and highly unlikely to be the cause of this acute and early graft dysfunction.
Question 48: A 71-year-old woman with diabetes and hypertension presents with progressive confusion over 3 days. Blood tests show: sodium 118 mmol/L, potassium 4.2 mmol/L, urea 3.8 mmol/L, creatinine 76 µmol/L, glucose 6.8 mmol/L, serum osmolality 248 mOsm/kg, urine osmolality 445 mOsm/kg, urine sodium 52 mmol/L. She takes bendroflumethiazide, ramipril, atorvastatin, and metformin. Clinical examination shows moist mucous membranes, no oedema, and blood pressure 138/82 mmHg. What is the most likely cause of her hyponatraemia?
A. Syndrome of inappropriate ADH secretion
B. Thiazide diuretic use (Correct Answer)
C. Cerebral salt wasting
D. Primary polydipsia
E. Adrenal insufficiency
Explanation: ***Thiazide diuretic use***
- **Bendroflumethiazide** is a common cause of profound hyponatraemia in elderly women by blocking sodium reabsorption in the **distal convoluted tubule**, which impairs the kidney's ability to dilute urine.
- The biochemical profile mimics SIADH (low serum osmolality, **urine osmolality >100 mOsm/kg**, and high urine sodium), but the presence of a causative medication makes this the most likely diagnosis.
*Syndrome of inappropriate ADH secretion*
- While the biochemistry matches **euvolaemic hypotonic hyponatraemia**, SIADH is a diagnosis of exclusion that should only be considered after drug-induced causes like **thiazides** are ruled out.
- SIADH is often associated with specific triggers such as **malignancy, CNS disorders, or pulmonary disease**, which are not mentioned in this history.
*Cerebral salt wasting*
- This condition typically follows **neurosurgical procedures** or head trauma and is characterized by significant **hypovolaemia** due to renal salt wasting.
- This patient is clinically **euvolaemic** with moist mucous membranes and stable blood pressure, making this diagnosis unlikely.
*Primary polydipsia*
- In primary polydipsia, the excessive intake of water leads to the excretion of large amounts of very dilute urine, reflected by a **low urine osmolality** (typically <100 mOsm/kg).
- This patient has a **high urine osmolality** (445 mOsm/kg), indicating that her urine is inappropriately concentrated.
*Adrenal insufficiency*
- Primary adrenal insufficiency usually presents with **hypotension** and classic electrolyte abnormalities such as **hyperkalaemia**, which are absent here (potassium 4.2 mmol/L).
- Patients with adrenal crisis are typically **hypovolaemic** and hemodynamically unstable, whereas this patient has a normal blood pressure of 138/82 mmHg.
Question 49: A 59-year-old man with CKD stage 4 (eGFR 22 mL/min/1.73m²) secondary to hypertensive nephropathy is reviewed in clinic. Blood tests show: haemoglobin 96 g/L, MCV 88 fL, ferritin 180 µg/L, transferrin saturation 22%, serum iron 8 µmol/L. He reports increasing fatigue affecting his daily activities. What is the most appropriate next step in managing his anaemia?
A. Commence oral ferrous sulfate 200mg three times daily
B. Arrange blood transfusion to target haemoglobin >110 g/L
C. Commence erythropoiesis-stimulating agent therapy
D. Arrange bone marrow biopsy to exclude myelodysplasia
E. Commence intravenous iron therapy (Correct Answer)
Explanation: ***Commence intravenous iron therapy***
- In patients with **CKD stage 4**, optimizing iron stores is the mandatory first step before initiating **Erythropoiesis-Stimulating Agents (ESAs)** to ensure efficacy.
- **Intravenous iron** is preferred over oral routes in advanced CKD as it bypasses **hepcidin-mediated** absorption blocks and more effectively raises **ferritin** and **transferrin saturation (TSAT)**.
*Commence oral ferrous sulfate 200mg three times daily*
- **Oral iron** is often poorly tolerated due to gastrointestinal side effects and is frequently ineffective in stage 4 CKD due to high **hepcidin levels**.
- Guidelines generally favor **IV iron** in non-dialysis CKD patients who cannot tolerate or fail to reach targets on oral therapy, or when rapid correction is needed.
*Arrange blood transfusion to target haemoglobin >110 g/L*
- **Blood transfusions** should be avoided in CKD patients unless there is acute instability or severe symptoms, as they increase the risk of **HLA sensitization**.
- Sensitization can significantly complicate future **renal transplantation** prospects by making it harder to find a compatible donor.
*Commence erythropoiesis-stimulating agent therapy*
- While **ESA therapy** treats the erythropoietin deficiency of CKD, it should not be started until **iron deficiency** is fully addressed to prevent "functional" iron deficiency.
- Starting an ESA without adequate iron often leads to a poor **haemoglobin response** and requires higher, potentially toxic doses of the drug.
*Arrange bone marrow biopsy to exclude myelodysplasia*
- A **bone marrow biopsy** is invasive and unnecessary here as the **normocytic anaemia** and biochemical profile are classic for **CKD-related anaemia**.
- This procedure is reserved for cases where the cause of anaemia remains **unexplained** after thorough initial investigation or failure to respond to standard therapy.
Question 50: A 48-year-old man with no significant past medical history presents with a 4mm distal ureteric calculus causing mild hydronephrosis. He has mild flank discomfort but is systemically well with normal renal function (creatinine 82 µmol/L), no fever, and white cell count 7.2 × 10⁹/L. Stone analysis from a previous episode showed calcium oxalate composition. Which investigation would be most useful in identifying a metabolic cause for recurrent stone formation?
A. Serum calcium, phosphate, parathyroid hormone, and vitamin D levels
B. 24-hour urine collection for calcium, oxalate, citrate, uric acid, and volume (Correct Answer)
C. Fasting plasma glucose and HbA1c
D. Serum uric acid level
E. Urinary pH measurement on spot sample
Explanation: ***24-hour urine collection for calcium, oxalate, citrate, uric acid, and volume***
- This is the **gold standard** for identifying metabolic risk factors in patients with **recurrent stones**, allowing for the assessment of **hypercalciuria, hyperoxaluria, and hypocitraturia**.
- It provides a comprehensive profile that guides specific medical and dietary interventions to prevent future **calcium oxalate** stone formation, which is the stone type this patient had previously.
*Serum calcium, phosphate, parathyroid hormone, and vitamin D levels*
- While these tests help screen for **primary hyperparathyroidism** and other bone-metabolism disorders, they do not identify other common metabolic causes like **hyperoxaluria** or **hypocitraturia**.
- This assessment is narrower in scope than a 24-hour urine collection and is usually secondary or supplementary to a comprehensive urine metabolic profile in recurrent stone formers.
*Fasting plasma glucose and HbA1c*
- These tests screen for **diabetes mellitus**, which is associated with metabolic syndrome and an increased risk of uric acid stones or calcium stones, but they do not directly identify the specific metabolic imbalances leading to **calcium oxalate** stone formation.
- They are not part of the standard initial **metabolic evaluation** for recurrent nephrolithiasis specifically targeting the urinary environment.
*Serum uric acid level*
- Serum uric acid levels do not reliably reflect **urinary uric acid excretion**, which is the relevant factor for uric acid stone formation or for promoting calcium oxalate stone formation.
- Although elevated **uricosuria** can promote calcium oxalate stone formation by acting as a nidus, its assessment requires a 24-hour urine collection, not a spot serum test.
*Urinary pH measurement on spot sample*
- A spot urinary pH sample is highly variable depending on diet, hydration status, and time of day, making it unreliable for diagnosing chronic conditions like **renal tubular acidosis** or consistently acidic urine that promotes stone formation.
- A **24-hour urine pH** measurement is required to accurately assess the overall urinary environment and detect persistent abnormalities that promote stone crystallization over a full cycle.
