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 in an Elderly Patient with Uncontrolled Hypertension

The next investigation for this elderly patient with uncontrolled hypertension, small left kidney, and confirmed renal artery stenosis should be balloon angioplasty (option D). This is the most appropriate next step based on current guidelines for managing renovascular hypertension with confirmed stenosis.

Rationale for Balloon Angioplasty

The patient presents with several key clinical features that strongly support proceeding directly to intervention:

1. Long-standing hypertension resistant to multiple drug treatments
2. Small left kidney on ultrasonography (suggesting chronicity and potential viability concerns)
3. Confirmed renal artery stenosis on arteriography

According to the 2024 ESC Guidelines for the Management of Elevated Blood Pressure and Hypertension, renal artery angioplasty and stenting may be considered in patients with:

• Resistant hypertension
• Hypertension with unexplained unilaterally small kidney
• Hemodynamically significant atherosclerotic renal artery stenosis 1

The patient meets these criteria, making balloon angioplasty the appropriate next step rather than additional diagnostic imaging.

Why Not Additional Imaging?

The other options (Renal CTA, Renal MRA, and Retrograde pyelography) would be redundant at this point:

• Renal CTA (Option A) or Renal MRA (Option B): These imaging modalities would typically be used to confirm suspected renal artery stenosis. However, the patient has already undergone renal arteriography, which is considered the gold standard for diagnosis of renal artery stenosis. The ESC guidelines state that when DUS-based suspicion of RAS exists, MRA or CTA are recommended 1, but in this case, we already have definitive arteriographic confirmation of stenosis.

• Retrograde pyelography (Option C): This procedure evaluates the collecting system of the kidney but does not provide additional information about vascular stenosis. It would not be helpful in this clinical scenario.

Therapeutic Approach

The 2024 ESC guidelines specifically recommend:

1. For atherosclerotic renal artery stenosis: Renal artery angioplasty with stenting should be considered in patients with resistant hypertension and hemodynamically significant stenosis 1

2. For fibromuscular dysplasia: Renal artery angioplasty without stenting is the recommended approach 1

Given that this is an elderly patient with long-standing hypertension, atherosclerotic renal artery stenosis is the most likely etiology, and balloon angioplasty with possible stenting would be the appropriate intervention.

Assessment of Kidney Viability

Before proceeding with intervention, it's important to assess kidney viability. According to the European Heart Journal, signs of kidney viability include:

• Renal size >8 cm (non-viable if <7 cm)
• Distinct renal cortex (>0.5 cm)
• Albumin-creatinine ratio <20 mg/mmol
• Renal resistance index <0.8 1, 2

The small left kidney in this patient may indicate reduced viability, but the decision to proceed with angioplasty should consider the overall clinical picture, including the severity of hypertension and failure of medical management.

Post-Procedure Management

After balloon angioplasty:

• Initial follow-up at 1 month and subsequently every 12 months 1
• Regular monitoring of blood pressure and renal function
• Continued antihypertensive therapy as needed
• Monitoring for restenosis, which occurs in 15-24% of cases 2

Potential Pitfalls

1. Failure to confirm hemodynamic significance before intervention
2. Risk of acute kidney injury following the procedure, especially if bilateral stenosis exists
3. Potential for restenosis requiring repeat intervention
4. Stent fracture in vessels with significant mobility or entrapment by diaphragmatic crus 3

In conclusion, balloon angioplasty is the appropriate next step for this elderly patient with uncontrolled hypertension, small left kidney, and confirmed renal artery stenosis, as it directly addresses the underlying cause of hypertension rather than pursuing additional diagnostic studies.