How can I differentiate between renal artery stenosis and other causes of secondary hypertension in primary care?

Differentiating renal artery stenosis (RAS) from other causes of secondary hypertension in primary care involves recognising specific clinical clues and utilising initial investigations NICE NG136.

Clinical Indicators Suggesting Renal Artery Stenosis:

• Resistant Hypertension: Hypertension that remains uncontrolled despite optimal doses of three or more antihypertensive agents, including a diuretic, should raise suspicion for secondary causes like RAS [3, Mannemuddhu et al. 2020].
• Sudden Onset or Severe Hypertension: New-onset hypertension, especially if severe or occurring suddenly, particularly in older adults or those without a family history of hypertension, warrants investigation for secondary causes [3, Mannemuddhu et al. 2020].
• Unexplained Renal Dysfunction: The presence of hypertension alongside unexplained kidney dysfunction or a worsening of kidney function after starting angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs) is a strong indicator for RAS [3, Mannemuddhu et al. 2020].
• Recurrent Flash Pulmonary Oedema: Episodes of sudden, severe pulmonary oedema without an obvious cardiac cause can be a clue for renovascular hypertension [ Mannemuddhu et al. 2020].
• Abdominal Bruit: The presence of an abdominal bruit, particularly if it is lateralising, may suggest renal artery stenosis [ Mannemuddhu et al. 2020].
• Asymmetric Kidney Size: If imaging has been performed for other reasons and shows a significant difference in kidney size, this can be a sign of RAS [ Mannemuddhu et al. 2020].

Initial Investigations in Primary Care:

• Blood Pressure Measurement: Measure blood pressure in both arms NICE NG136.
• Blood Tests: Routine blood tests should include electrolytes (sodium, potassium), creatinine, and estimated glomerular filtration rate (eGFR) to assess kidney function [1, 2, 3, Mannemuddhu et al. 2020].
• Urinalysis: Perform urinalysis to check for protein and blood, and consider an albumin:creatinine ratio (ACR) [1, 2, Mannemuddhu et al. 2020]. These tests help identify kidney disease, which is a common feature of RAS and other renal causes of hypertension [1, 2, 3, Mannemuddhu et al. 2020].

While these clues and tests help identify a renal component to hypertension, further specific investigations would be required to confirm RAS and differentiate it from other renal or endocrine causes of secondary hypertension NICE NG136.