Mock Nephrology Module 4

A 47-year-old man with ESKD secondary to autosomal dominant polycystic kidney disease has been on haemodialysis for 2 years. He is blood group O. His wife wishes to donate a kidney but is blood group A.

HLA crossmatch is negative and there are no donor-specific antibodies.

Which of the following is the most appropriate transplantation pathway?

A 60-year-old woman receives a deceased donor kidney transplant. The donor was a 62-year-old man who died from an intracerebral haemorrhage. Donor CMV serology is positive, and recipient CMV serology is negative.

She receives basiliximab induction, tacrolimus, mycophenolate mofetil, and prednisone.

What is the most appropriate CMV prevention strategy for this patient?

A 66-year-old man with ESKD secondary to hypertensive nephrosclerosis has been on haemodialysis for 5 years. He receives a deceased donor kidney transplant.

The donor kidney had an estimated KDPI (Kidney Donor Profile Index) of 88%.

In the context of the Australian kidney allocation system implemented in May 2021, which of the following principles best justifies allocating this kidney to this recipient?

A 39-year-old woman receives a living donor kidney transplant from her husband. She is on tacrolimus, mycophenolate mofetil, and prednisolone following basiliximab induction.

On day 1 post-transplant, she is anuric. Serum creatinine is 620 µmol/L (reference 45–90 µmol/L). A renal transplant ultrasound with Doppler shows absent arterial and venous flow within the graft.

What is the most appropriate immediate action?

A 51-year-old man is 2 years post deceased donor kidney transplant on tacrolimus, mycophenolate mofetil, and prednisolone. He presents with a creatinine rise from 115 to 168 µmol/L (reference 60–110) over 3 months.

His tacrolimus trough level is 6.2 µg/L. He reports taking all medications regularly.

Renal transplant ultrasound shows a resistive index of 0.85 with turbulent flow at the arterial anastomosis and a peak systolic velocity ratio greater than 3:1 at the anastomosis compared with the proximal iliac artery.

What is the most likely diagnosis?

A 44-year-old woman is being assessed for kidney transplant waitlisting. She has ESKD secondary to lupus nephritis class IV, currently in serological and clinical remission for 3 years. She has had two pregnancies and one previous blood transfusion.

Her CPRA is 85%. She has never received a transplant.

Which of the following factors in her history is the least likely contributor to her current HLA sensitisation?

A 57-year-old man is 6 months post deceased donor kidney transplant. He was CMV D-/R- and received basiliximab induction.

He now presents with fever, cough, and bilateral interstitial infiltrates on chest X-ray.

His white cell count is 2.8 × 10⁹/L (reference 4.0–11.0), with a lymphocyte count of 0.4 × 10⁹/L (reference 1.0–4.0).

He is on tacrolimus, mycophenolate mofetil, and prednisone.

He was taking trimethoprim-sulfamethoxazole prophylaxis but ceased it 2 weeks ago due to hyperkalaemia. CMV PCR is negative.

Which of the following is the most likely opportunistic infection?

A 35-year-old man received a deceased donor kidney transplant 10 days ago. He was induced with anti-thymocyte globulin (ATG) due to a high immunological risk profile (repeat transplant, CPRA 92%).

His donor was EBV seropositive and the recipient was EBV seronegative. He is currently on tacrolimus, mycophenolate mofetil, and prednisolone.

At 8 months post-transplant, he develops cervical lymphadenopathy, night sweats, and an elevated LDH of 580 U/L (reference 120–250).

A CT scan shows widespread lymphadenopathy above and below the diaphragm with splenic involvement.

Which of the following is the most likely diagnosis?

A 52-year-old woman is being evaluated for pre-emptive living donor kidney transplantation.

Her eGFR is 12 mL/min/1.73m² and she has not yet commenced dialysis.

Her sister is a willing and medically suitable donor with compatible blood group and negative crossmatch.

Compared with transplantation after a period of dialysis, which of the following outcomes is most strongly associated with pre-emptive transplantation?

A 49-year-old man is 3 years post kidney transplant on tacrolimus (trough 5.5 µg/L), mycophenolate mofetil 500 mg twice daily (reduced from 1g twice daily due to leucopenia), and prednisone 5 mg daily.

He has stable graft function with creatinine 125 µmol/L (reference 60–110).

He is found to have new donor-specific antibodies (DSA) with a mean fluorescence intensity (MFI) of 8,500 against a donor HLA-DQ mismatch.

A protocol biopsy shows early transplant glomerulopathy with peritubular capillaritis and positive C4d staining.

What is the most likely underlying contributor to the development of de novo DSA in this patient?

A 55-year-old man with biopsy-proven membranous nephropathy presents with worsening bilateral lower limb oedema extending to his thighs, abdominal distension with shifting dullness, and dyspnoea on exertion. His weight has increased by 12 kg over 4 weeks.

Investigations reveal:

• serum albumin 15 g/L (reference: 35–50 g/L)
• uPCR 1050 mg/mmol (reference: <30 mg/mmol)
• eGFR 48 mL/min/1.73m²
• serum sodium 132 mmol/L (reference: 135–145 mmol/L)
• serum potassium 3.8 mmol/L (reference: 3.5–5.0 mmol/L)

He has been taking frusemide 80 mg twice daily orally with minimal response.

What is the most appropriate next step in management of his volume overload?

A 68-year-old man, current smoker with 40 pack-year history, presents with bilateral leg oedema and frothy urine over 2 months.

Investigations reveal:

• uPCR 620 mg/mmol (reference: <30 mg/mmol), my
• serum albumin 23 g/L (reference: 35–50 g/L)
• eGFR 64 mL/min/1.73m²
• negative anti-PLA2R antibodies

Kidney biopsy shows subepithelial deposits with IgG-dominant staining and a membranous pattern of injury. Anti-PLA2R staining on the biopsy tissue is also negative.

What is the most important next investigation?

A 35-year-old woman undergoes kidney biopsy for persistent microscopic haematuria and proteinuria (uPCR 150 mg/mmol; reference: <30 mg/mmol) with blood pressure 138/86 mmHg and eGFR 72 mL/min/1.73m² (reference: >90 mL/min/1.73m²).

Biopsy shows mesangial IgA deposition. The pathologist reports the Oxford classification score.

Which histological feature on the Oxford MEST-C classification most strongly predicts irreversible kidney damage?

A 60-year-old man with PR3-ANCA positive granulomatosis with polyangiitis (GPA) achieved remission following induction therapy with glucocorticoids and rituximab 6 months ago.

His creatinine has stabilised at 120 µmol/L (reference: 60–110 µmol/L), eGFR 55 mL/min/1.73m², urine is bland, and CRP is 3 mg/L (reference: <5 mg/L).

PR3-ANCA titre has declined significantly. He is being transitioned to maintenance therapy.

Which of the following maintenance strategies has the strongest evidence for sustaining remission and preventing relapse?

A 42-year-old man presents to the emergency department with cola-coloured urine following an upper respiratory tract infection 24 hours ago. He is normotensive. Urine dipstick is positive for blood (3+) and protein (2+). Renal tract ultrasound is unremarkable.

Which finding on urine microscopy would most strongly suggest a glomerular origin of haematuria?

A 32-year-old woman with systemic lupus erythematosus is diagnosed with Class IV lupus nephritis on kidney biopsy.

She has an eGFR of 52 mL/min/1.73m² (reference: >90 mL/min/1.73m²), uPCR 380 mg/mmol (reference: <30 mg/mmol), and serum albumin 25 g/L (reference: 35–50 g/L).

Her treating nephrologist plans to initiate mycophenolate mofetil and glucocorticoids, and considers adding voclosporin.

Which of the following best describes the pharmacological advantage of voclosporin over traditional calcineurin inhibitors in this setting?

A 70-year-old woman with newly diagnosed MPO-ANCA positive microscopic polyangiitis and biopsy-proven pauci-immune crescentic glomerulonephritis is commenced on induction therapy with rituximab and glucocorticoids.

She has type 2 diabetes (HbA1c 8.2%; reference: <6.0%), osteoporosis with a prior vertebral fracture, and BMI 32 kg/m².

Her treating team is concerned about glucocorticoid toxicity.

Which of the following strategies has the strongest evidence to support minimising glucocorticoid exposure in this patient?

A 64-year-old woman is investigated for progressive renal impairment with creatinine 180 µmol/L (reference: 45–90 µmol/L), eGFR 28 mL/min/1.73m², proteinuria (uPCR 250 mg/mmol; reference: <30 mg/mmol), and microscopic haematuria.

Serum protein electrophoresis shows a small IgG kappa monoclonal band.

Serum free light chain ratio is abnormal (kappa 85 mg/L, lambda 12 mg/L; reference kappa: 3.3–19.4 mg/L, lambda: 5.7–26.3 mg/L).

Bone marrow biopsy shows 4% clonal plasma cells. There are no lytic bone lesions, anaemia, or hypercalcaemia.

Kidney biopsy shows a membranoproliferative pattern of injury with monoclonal IgG kappa deposits.

What is the most appropriate classification of this patient’s condition?

A 40-year-old man with biopsy-proven IgA nephropathy has persistent proteinuria of 1.5 g/day despite 6 months of maximally tolerated ramipril (10 mg daily), an SGLT2 inhibitor, blood pressure 118/74 mmHg, and dietary sodium restriction.

His eGFR is 60 mL/min/1.73m² (reference: >90 mL/min/1.73m²), BMI is 33 kg/m², and HbA1c is 6.8% (reference: <6.0%).

His nephrologist considers immunosuppressive therapy but is concerned about glucocorticoid toxicity.

Which of the following best describes the mechanism by which targeted-release budesonide (Nefecon) reduces proteinuria in IgA nephropathy?

A 50-year-old man with biopsy-proven primary FSGS has nephrotic-range proteinuria (uPCR 650 mg/mmol; reference: <30 mg/mmol), serum albumin 21 g/L (reference: 35–50 g/L), and eGFR 45 mL/min/1.73m² (reference: >90 mL/min/1.73m²). He is commenced on prednisolone and supportive care. His dietitian asks for guidance on daily protein intake.

Which of the following dietary protein recommendations is most appropriate for this patient?

A 28-year-old woman with type 1 diabetes mellitus presents to the emergency department after three days of vomiting and poor oral intake. She had stopped her insulin five days ago.

On examination, she is tachypnoeic with Kussmaul breathing, has dry mucous membranes, and is haemodynamically stable.

Her investigations reveal:

Arterial blood gas:

• pH 7.32
• PaCO2 24 mmHg (reference range 35-45 mmHg)
• PaO2 95 mmHg (reference range 80-100 mmHg)
• HCO3- 12 mmol/L (reference range 22-26 mmol/L)

Serum:

• Na+ 138 mmol/L (reference range 135-145 mmol/L)
• K+ 4.8 mmol/L (reference range 3.5-5.0 mmol/L)
• Cl- 98 mmol/L (reference range 98-106 mmol/L)
• glucose 28 mmol/L (reference range 3.0-5.4 mmol/L fasting)
• albumin 40 g/L (reference range 35-50 g/L)
• urea 10 mmol/L (reference range 3.0-8.0 mmol/L)
• creatinine 120 micromol/L (reference range 45-90 micromol/L)

Urine ketones: 3+

Which of the following best describes the complete acid-base disturbance in this patient?

A 35-year-old man presents with a ten-day history of progressively worsening nausea and non-bilious vomiting. He has a known history of peptic ulcer disease and has not been taking his proton pump inhibitor.

On examination, he is lethargic with dry mucous membranes, reduced skin turgor, and postural hypotension. His investigations reveal:

Arterial blood gas:

• pH 7.52
• PaCO2 42 mmHg (reference range 35-45 mmHg)
• PaO2 98 mmHg (reference range 80-100 mmHg)
• HCO3- 33 mmol/L (reference range 22-26 mmol/L)

Serum:

• Na+ 140 mmol/L (reference range 135-145 mmol/L)
• K+ 2.8 mmol/L (reference range 3.5-5.0 mmol/L)
• Cl- 88 mmol/L (reference range 98-106 mmol/L)

Which of the following is the primary mechanism maintaining the metabolic alkalosis in this patient?

A 62-year-old man with severe chronic obstructive pulmonary disease (COPD) presents to the emergency department with a two-day history of increasing dyspnoea, productive cough with purulent sputum, and fever. SpO2: 78% on room air.

His baseline arterial blood gas from three months ago showed pH 7.36, PaCO2 58 mmHg, HCO3- 32 mmol/L.

Current investigations reveal:

Arterial blood gas: pH 7.18, PaCO2 85 mmHg (reference range 35-45 mmHg), PaO2 45 mmHg (reference range 80-100 mmHg), HCO3- 31 mmol/L (reference range 22-26 mmol/L)

Which of the following best explains why the bicarbonate has not increased proportionally to the acute rise in PaCO2?

A 45-year-old man with a recent ileostomy formation for Crohn’s disease presents with lethargy, weakness, and high ileostomy output over the past week. He appears moderately dehydrated.

His investigations reveal:

Arterial blood gas:

• pH 7.28
• PaCO2 27 mmHg (reference range 35-45 mmHg)
• HCO3- 12 mmol/L (reference range 22-26 mmol/L)

Serum:

• Na+ 136 mmol/L (reference range 135-145 mmol/L)
• K+ 3.0 mmol/L (reference range 3.5-5.0 mmol/L)
• Cl- 112 mmol/L (reference range 98-106 mmol/L)
• albumin 38 g/L (reference range 35-50 g/L)

Urine: Na+ 25 mmol/L, K+ 30 mmol/L, Cl- 80 mmol/L

Which of the following is the most appropriate interpretation of the urine anion gap in this clinical context?

A 38-year-old man is brought to the emergency department by ambulance after being found confused in a park. He is known to have alcohol use disorder.

On examination, he is tachypnoeic with visual impairment, reporting blurred vision. His investigations reveal:

Arterial blood gas:

• pH 7.15
• PaCO2 18 mmHg (reference range 35-45 mmHg)
• PaO2 98 mmHg (reference range 80-100 mmHg)
• HCO3- 6 mmol/L (reference range 22-26 mmol/L)

Serum:

• Na+ 140 mmol/L (reference range 135-145 mmol/L)
• K+ 4.5 mmol/L (reference range 3.5-5.0 mmol/L)
• Cl- 102 mmol/L (reference range 98-106 mmol/L)
• glucose 5.0 mmol/L (reference range 3.0-5.4 mmol/L fasting)
• urea 8.0 mmol/L (reference range 3.0-8.0 mmol/L)
• creatinine 150 micromol/L (reference range 60-110 micromol/L)
• albumin 30 g/L (reference range 35-50 g/L)

Measured serum osmolality: 340 mOsmol/kg Calculated serum osmolality (2 x Na + glucose + urea): 293 mOsmol/kg

Which of the following is the most likely toxic ingestion?

A 32-year-old woman presents with two days of nausea, vomiting, and poor oral intake following a three-day alcohol binge. She has a history of chronic alcohol use disorder and poor nutritional intake.

On examination, she is tachycardic and appears dehydrated.

Investigations:

Arterial blood gas:

• pH 7.30
• PaCO2 29 mmHg (reference range 35-45 mmHg)
• PaO2 92 mmHg (reference range 80-100 mmHg)
• HCO3- 16 mmol/L (reference range 22-26 mmol/L)

Serum:

• Na+ 132 mmol/L (reference range 135-145 mmol/L)
• K+ 5.0 mmol/L (reference range 3.5-5.0 mmol/L)
• Cl- 104 mmol/L (reference range 98-106 mmol/L)
• glucose 4.2 mmol/L (reference range 3.0-5.4 mmol/L fasting)
• urea 8.9 mmol/L (reference range 3.0-8.0 mmol/L)
• creatinine 115 micromol/L (reference range 45-90 micromol/L)
• Serum albumin: 10 g/L (reference range 35-50 g/L)

After correcting for the albumin level, what is the most accurate description of this patient’s acid-base disorder?

A 34-year-old woman is referred to the nephrology clinic for investigation of recurrent calcium phosphate nephrolithiasis. She reports fatigue and muscle weakness. She takes no regular medications and has no history of diarrhoeal illness.

Her investigations reveal:

Arterial blood gas:

• pH 7.30
• PaCO2 28 mmHg (reference range 35-45 mmHg)
• HCO3- 14 mmol/L (reference range 22-26 mmol/L)

Serum:

• Na+ 140 mmol/L (reference range 135-145 mmol/L)
• K+ 2.5 mmol/L (reference range 3.5-5.0 mmol/L)
• Cl- 118 mmol/L (reference range 98-106 mmol/L)
• albumin 40 g/L (reference range 35-50 g/L)
• creatinine 80 micromol/L (reference range 45-90 micromol/L)

Urine:

• pH: 7.0
• Na+ 40 mmol/L
• K+ 35 mmol/L
• Cl- 20 mmol/L

Renal ultrasound: Bilateral medullary nephrocalcinosis

Which type of renal tubular acidosis is most consistent with these findings?

A 30-year-old woman who is 28 weeks pregnant with a known history of type 1 diabetes mellitus is admitted to the intensive care unit after discontinuing her insulin one week ago.

She reports several days of severe nausea and vomiting and is noted to be tachypnoeic.

Her investigations reveal:

Arterial blood gas:

• pH 7.55,
• PaCO2 21 mmHg (reference range 35-45 mmHg),
• PaO2 70 mmHg (reference range 80-100 mmHg),
• HCO3- 18 mmol/L (reference range 22-26 mmol/L)

Serum:

• Na+ 136 mmol/L (reference range 135-145 mmol/L)
• K+ 3.5 mmol/L (reference range 3.5-5.0 mmol/L)
• Cl- 70 mmol/L (reference range 98-106 mmol/L)
• urea 11.4 mmol/L (reference range 3.0-8.0 mmol/L)
• creatinine 106 micromol/L (reference range 45-90 micromol/L)
• CO2 19 mmol/L

Which of the following best describes this patient’s acid-base disturbance?

A 55-year-old man with obesity hypoventilation syndrome presents for routine outpatient review. He has been stable over the past three months with no acute illness. His body mass index is 52 kg/m2. He uses nocturnal non-invasive ventilation. He is haemodynamically stable and comfortable at rest.

Arterial blood gas:

• pH 7.36
• PaCO2 60 mmHg (reference range 35-45 mmHg)
• PaO2 62 mmHg (reference range 80-100 mmHg)
• HCO3- 33 mmol/L (reference range 22-26 mmol/L)

Which of the following values most closely represents the expected bicarbonate if this were a simple acute respiratory acidosis with the same PaCO2?

A 42-year-old previously well man presents to the emergency department after five days of severe vomiting secondary to small bowel obstruction.

On examination, he has postural hypotension with a systolic blood pressure drop of 30 mmHg on standing, heart rate of 120 bpm, and markedly diminished skin turgor. His peripheries are cool and mottled.

Investigations:

Serum:

• Na+ 140 mmol/L (reference range 135-145 mmol/L)
• K+ 3.4 mmol/L (reference range 3.5-5.0 mmol/L)
• Cl- 77 mmol/L (reference range 98-106 mmol/L)
• HCO3- 9 mmol/L (reference range 22-26 mmol/L)
• creatinine 350 micromol/L (reference range 60-110 micromol/L)
• lactate 12 mmol/L (reference range less than 2 mmol/L)
• albumin 40 g/L (reference range 35-50 g/L)

Arterial blood gas:

• pH 7.23
• PaCO2 22 mmHg (reference range 35-45 mmHg)

Which of the following best explains the metabolic acidosis despite prolonged vomiting?

A 42-year-old man with a history of alcohol abuse disorder is brought to the emergency department obtunded, after his partner found an empty bottle of automotive antifreeze beside him. 

On examination he is drowsy (GCS 10), tachypnoeic (respiratory rate 32/min), heart rate 118/min, blood pressure 105/65 mmHg.

Investigations:

• Venous blood gas: pH 7.08 (7.35–7.45)
• HCO₃⁻ 8 mmol/L (22–32), pCO₂ 22 mmHg
• Sodium 140 mmol/L (135–145),
• Chloride 100 mmol/L (95–110)
• Point-of-care (blood gas analyser) lactate 14 mmol/L (0.5–2.2)
• Glucose 6.0 mmol/L (3.0–7.8)
• Creatinine 130 µmol/L (60–110)
• Osmolar gap 28 mOsm/kg (<10)

A diagnosis of ethylene glycol poisoning is made, and fomepizole is commenced.

However, the intensive care registrar is concerned about the very high lactate of 14 mmol/L and asks whether this reflects severe tissue hypoperfusion requiring escalation of resuscitation.

Which of the following is the most appropriate next step?