What is the next best investigation for an elderly patient with uncontrolled Hypertension (HTN) and renal artery stenosis, who has undergone multiple lines of drug treatment and has had ultrasonography showing a small left kidney and renal arteriography confirming stenosis?

Management of Renal Artery Stenosis: Next Investigation After Confirmed Stenosis

For a patient with long-standing uncontrolled hypertension, small left kidney on ultrasonography, and confirmed renal artery stenosis on arteriography, balloon angioplasty (option D) is the next appropriate step rather than additional imaging studies.

Diagnostic Confirmation and Treatment Decision

The patient already has:

• Long-standing uncontrolled hypertension despite multiple medication trials
• Ultrasonography showing a small left kidney (suggesting chronic ischemia)
• Renal arteriography confirming renal artery stenosis

At this point, the diagnostic workup is complete, and the focus should shift to treatment rather than additional imaging studies.

Why Not Additional Imaging?

1. Renal CTA (option A) or Renal MRA (option B):

   • These would be redundant since arteriography has already confirmed the stenosis 1
   • Arteriography is considered the gold standard for diagnosis of renal artery stenosis
   • The European Society of Cardiology recommends duplex ultrasound as first-line imaging, followed by MRA or CTA if needed, but the patient has already progressed beyond these steps 1

2. Retrograde pyelography (option C):

   • This technique evaluates the collecting system, not the renal vasculature
   • Not indicated for evaluation of renal artery stenosis 1

Rationale for Balloon Angioplasty

The 2024 ESC Guidelines strongly support balloon angioplasty as the appropriate next step in this clinical scenario:

• For patients with hypertension and hemodynamically significant renal artery stenosis with resistant hypertension, angioplasty should be considered (Class IIa recommendation) 1
• The patient meets criteria for intervention: uncontrolled hypertension despite multiple medications, evidence of renal damage (small kidney), and confirmed stenosis 2
• Small kidney size suggests chronic ischemia but may still indicate viable kidney tissue that could benefit from revascularization 2

Type of Intervention Based on Etiology

The type of intervention depends on the underlying cause of stenosis:

1. For fibromuscular dysplasia:

   • Primary balloon angioplasty without stenting is recommended (Class IIa) 1
   • Has excellent success rates and lower restenosis rates compared to atherosclerotic disease 2

2. For atherosclerotic stenosis:

   • Balloon angioplasty with stenting is recommended (Class IIa) 1
   • Particularly indicated in resistant hypertension with unexplained unilaterally small kidney 1

Assessment Before Intervention

Before proceeding with balloon angioplasty, assessment of kidney viability is important:

Parameter	Signs of Viability	Signs of Non-viability
Renal size	>8 cm	<7 cm
Renal cortex	Distinct cortex (>0.5 cm)	Loss of corticomedullary differentiation
Proteinuria	Albumin-creatinine ratio <20 mg/mmol	Albumin-creatinine ratio >30 mg/mmol
Renal resistance index	<0.8	>0.8

Even with a small kidney, if other viability parameters are favorable, revascularization may still be beneficial 1, 2.

Post-Intervention Management

After balloon angioplasty:

• Initial follow-up at 1 month
• Subsequent follow-up every 12 months or when new symptoms arise
• Monitoring should include renal function tests and duplex ultrasound 1
• Re-intervention may be considered for in-stent restenosis ≥60% detected by duplex ultrasound 1

Potential Complications

• In-stent restenosis (occurs in 15-24% of cases) 2
• Stent fracture (rare but can occur, especially with renal artery entrapment by diaphragmatic crus or mobile kidney with acute angulation) 3
• Acute kidney injury (particularly if bilateral stenosis is present) 2

Conclusion

Based on the most recent guidelines and the patient's clinical presentation with confirmed renal artery stenosis, balloon angioplasty (option D) is the appropriate next step rather than additional imaging studies.