What is the next investigation for an elderly patient with uncontrolled Hypertension (HTN) and renal artery stenosis, who has undergone ultrasonography showing a small left kidney and renal arteriography?

Next Investigation for Elderly Patient with Uncontrolled HTN and Renal Artery Stenosis

The next investigation for this patient with uncontrolled hypertension and renal artery stenosis should be Renal MRA (Magnetic Resonance Angiography). 1

Rationale for Choosing MRA

The patient presents with several key findings that strongly suggest renovascular hypertension:

• Long-standing uncontrolled hypertension despite multiple medication trials
• Small left kidney on ultrasonography (suggesting chronic ischemia)
• Confirmed renal artery stenosis on renal arteriography

At this point, the diagnostic algorithm requires further characterization of the stenosis to determine appropriate management:

1. MRA is recommended by guidelines: The 2024 ESC guidelines specifically state that "In cases of DUS-based suspicion of RAS or inconclusive DUS, MRA or CTA are recommended" with a Class I, Level B recommendation 1

2. Advantages of MRA over other options:

   • Provides detailed anatomical information about the degree and location of stenosis
   • Can assess kidney viability (important for treatment decisions)
   • Does not require iodinated contrast (beneficial in a patient who may have compromised renal function)
   • Has high sensitivity (90-100%) for detecting significant renal artery stenosis 2, 3

Why Not the Other Options?

• Renal CTA: While also recommended by guidelines as an alternative to MRA 1, CTA involves radiation exposure and iodinated contrast, which may further compromise renal function in this patient with likely renovascular disease

• Retrograde pyelography: Not indicated for evaluation of renal artery stenosis; it evaluates the collecting system rather than vascular structures 1

• Balloon angioplasty: This is a therapeutic intervention, not a diagnostic test. It would be premature to proceed directly to intervention without proper characterization of the stenosis and assessment of kidney viability 1

Assessment of Kidney Viability

MRA will help determine kidney viability, which is crucial for treatment decisions. According to the 2024 ESC guidelines 1, signs of kidney viability include:

• Renal size >8 cm
• Distinct renal cortex (>0.5 cm)
• Albumin-creatinine ratio <20 mg/mmol
• Renal resistance index <0.8

The small left kidney noted on ultrasonography may indicate poor viability (<7 cm is considered non-viable), which would impact treatment decisions.

Next Steps After MRA

Based on MRA findings, the management algorithm would proceed as follows:

1. If MRA confirms >70% stenosis or hemodynamically significant 50-70% stenosis with viable kidney:

   • Consider renal artery revascularization (Class IIa recommendation) 1

2. If bilateral stenosis is confirmed:

   • Revascularization should be considered (Class IIa recommendation) 1

3. If stenosis is <70% without hemodynamic significance:

   • Continue optimal medical therapy 1

MRA has demonstrated high specificity (91-98%) and sensitivity (84-100%) in multiple studies, making it an excellent non-invasive diagnostic tool for this clinical scenario 4, 3, 5.