A 38-year-old woman presents with hypertension (BP 158/98 mmHg) detected 6 months ago. She is on amlodipine 5 mg daily with suboptimal control. Clinical examination reveals an abdominal bruit. Serum creatinine is 1.4 mg/dL (baseline unknown). Which investigation is most appropriate to confirm the suspected diagnosis of renovascular hypertension?

Explanation

## Investigation of Choice for Suspected Renovascular Hypertension ### Clinical Context The patient presents with: - **Young age** (38 years) with hypertension - **Abdominal bruit** (suggests renal artery stenosis) - **Suboptimal response** to single antihypertensive - **Elevated creatinine** (suggests renal compromise) These features strongly suggest **renovascular hypertension**, most commonly due to fibromuscular dysplasia in young women or atherosclerotic disease in older patients. ### Why CT Angiography is the Investigation of Choice **Key Point:** CT angiography of renal arteries is the **gold standard non-invasive imaging** for diagnosing renovascular hypertension in most clinical settings. | Investigation | Sensitivity | Specificity | Advantages | Limitations | |---|---|---|---|---| | **CT angiography** | 94–98% | 90–94% | High sensitivity/specificity, rapid, assesses renal parenchyma, widely available, no operator dependency | Radiation, contrast (risk in renal impairment) | | Duplex ultrasound | 85% | 92% | No radiation, no contrast, non-invasive | Operator-dependent, poor in obesity, time-consuming | | Captopril renography | 80–90% | 85% | Functional assessment, lower radiation | Less sensitive than CT/MRA, poor in renal insufficiency | | Renal artery pressure gradient | 100% (diagnostic) | 100% | Gold standard for hemodynamic significance | Invasive, reserved for when intervention planned | ### High-Yield Points **Key Point:** In this patient with **renal insufficiency (Cr 1.4)**, CT angiography with careful hydration and **iso-osmolar or low-osmolar contrast** is safer than captopril renography (which loses sensitivity when GFR < 60). **Clinical Pearl:** The **abdominal bruit** is a clinical red flag for renal artery stenosis and warrants imaging. Presence of bruit + young age + hypertension = think fibromuscular dysplasia (most common cause in women < 50 years). **Mnemonic: ABCD for Renovascular HTN Screening** - **A**brupt onset (< 30 or > 55 years) - **B**ruit (abdominal or flank) - **C**ontrol failure (resistant hypertension) - **D**eteriorating renal function (especially with ACE-I/ARB) ### Why Other Options Are Not First-Line 1. **Captopril renography** — Functional test, but sensitivity drops significantly when creatinine > 1.3 mg/dL. Better for screening in normal renal function. 2. **Duplex ultrasound** — Operator-dependent, time-consuming, poor sensitivity in obese patients. Useful as initial screening in experienced centers, but not standard. 3. **Renal artery pressure gradient** — This is **invasive** (requires renal artery catheterization). Reserved for patients in whom intervention (angioplasty/stenting) is already planned. Not a diagnostic test; it assesses **hemodynamic significance** of a stenosis already identified on imaging. [cite:Harrison 21e Ch 297]