Sat27November0556PM 43

A 52-year-old man presented with acute dyspnoea. His past medical history includes three vessel coronary artery bypass surgery for ischaemic heart disease.

Examination revealed widespread inspiratory crackles with chest x ray confirming pulmonary oedema. He was treated with intravenous nitrates and furosemide with symptomatic improvement. Investigations at this stage revealed:

Serum sodium 138 mmol/L (137-144)

Serum potassium 4.2 mmol/L (3.5-4.9)

Serum urea 8.7 mmol/L (2.5-7.5)

Serum creatinine 170 µmol/L (60-110)

Random plasma glucose 10.1 mmol/L (<11.1)

Urinalysis Protein ++

The following day he was switched to oral furosemide at a dose of 80 mg daily and began captopril 12.5 mg twice daily, increased to 25 mg twice daily. Repeat investigations one week later revealed:

Serum sodium 134 mmol/L (137-144)

Serum potassium 5.1 mmol/L (3.5-4.9)

Serum urea 20.7 mmol/L (2.5-7.5)

Serum creatinine 270 µmol/L (60-110)

Fasting plasma glucose 6.0 mmol/L (3.0-6.0)

Which is the next best investigation after emergency treatment in determining the cause of his renal failure?

(Please select 1 option)

Renal isotope scan

Renal biopsy

Magnetic resonance renal angiography This is the correct answer

Doppler of the renal arteries Incorrect answer selected

Captopril renogram

Explanation

This patient has coronary heart disease.

Renal function deteriorated in the presence of an angiotensin-converting enzyme inhibitor (ACEI) and it is important to exclude atheroma of the renal arteries causing renal artery stenosis. Renal angiography, particularly MR angiography is a good way to diagnose renovascular disease without having to administer nephrotoxic contrast. This does not have to be performed as an emergency, but after stopping the ACE-inhibitor and rehydrating the patient. At this point, the risk of gadolinium-induced complications will be decreased.

As gold standard, percutaneous angiography is the investigation of choice, and also enables angioplasty, if indicated.

Renal artery Doppler is prone to more false negative results than angiography.

Answer Statistics

1

1%

2

4%

3

20%

4

71%

5

7%

Times answered: 294