Diagnostic Investigation for Refractory Hypertension with Renal Bruit
This patient requires immediate imaging of the renal arteries to evaluate for renovascular hypertension, as the combination of refractory hypertension and a renal bruit strongly suggests renal artery stenosis as the underlying cause. 1, 2
Initial Basic Screening
Before proceeding to advanced imaging, confirm this is truly resistant hypertension by excluding pseudoresistance and drug-induced causes 1:
- Verify proper blood pressure measurement technique and exclude white coat hypertension with ambulatory or home blood pressure monitoring 1
- Review medication adherence and ensure adequate dosing (including a diuretic at appropriate doses) 1
- Exclude drug/substance-induced hypertension (NSAIDs, decongestants, oral contraceptives, steroids, licorice) 1
Essential Laboratory Workup
Basic blood biochemistry is mandatory and should include 1:
- Serum sodium and potassium (hypokalemia suggests primary aldosteronism)
- eGFR and serum creatinine (assess renal function before contrast studies)
- TSH (exclude thyroid dysfunction)
- Dipstick urinalysis (proteinuria suggests parenchymal disease)
The presence of obesity increases the likelihood of obstructive sleep apnea as a contributing factor, but the renal bruit makes renovascular disease the priority 1.
Definitive Imaging for Renovascular Disease
The renal bruit is a critical clinical clue that strongly predicts renal artery stenosis (P < 0.0005) 2. In patients with refractory hypertension and a bruit, the likelihood of renovascular disease is substantially elevated 2.
Imaging of the renal arteries should be performed using 1:
- Duplex ultrasound (first-line, non-invasive, no contrast)
- CT angiography (if renal function permits; eGFR considerations apply)
- MR angiography (preferred if eGFR <30 mL/min/1.73m² to avoid contrast nephropathy)
The choice depends on local availability and the patient's renal function level 1. Given the obesity, ultrasound quality may be limited, making CT or MR angiography more reliable 1.
Additional Targeted Investigations
Kidney ultrasound should be performed to assess 1:
- Kidney size and symmetry (asymmetric kidneys suggest chronic renovascular disease)
- Cortical thickness
- Evidence of polycystic kidney disease (bilateral masses on examination) 1
Consider screening for primary aldosteronism if hypokalemia is present, as this affects 8-20% of resistant hypertension cases 3. However, the renal bruit makes renovascular disease the more likely diagnosis in this specific patient 2.
Sleep apnea screening (home sleep study or polysomnography) should be considered given the obesity, but this is secondary to ruling out renovascular disease 1.
Critical Clinical Pitfall
Do not empirically start an ACE inhibitor or ARB before imaging in a patient with suspected bilateral renal artery stenosis or stenosis in a solitary functioning kidney, as this can precipitate acute renal failure 4, 5. The combination of refractory hypertension and a bruit raises concern for bilateral disease or disease in a solitary kidney 5.
Referral Considerations
Refer to a specialist center with expertise in renovascular hypertension if renal artery stenosis is confirmed, as management decisions (medical therapy vs. angioplasty vs. surgery) require specialized assessment 1. Refractory hypertension with progressive renal function decline represents an indication for revascularization 1, 5.
The presence of azotemia (elevated creatinine) in addition to refractory hypertension and a bruit makes renovascular hypertension a particularly common and important diagnosis to pursue aggressively 5.