Which feature best distinguishes primary (essential) hypertension from secondary hypertension due to renal artery stenosis?

Question

Accepted Answer

C. Presence of an abdominal systolic-diastolic bruit on auscultation. ## Distinguishing Primary from Secondary Hypertension (RAS)

### Key Discriminating Feature

**Key Point:** An abdominal systolic-diastolic bruit (or continuous bruit) is a hallmark finding of renal artery stenosis (RAS) and is absent in primary hypertension. This bruit reflects turbulent flow across the stenotic lesion.

### Why This Discriminates

The presence of a vascular bruit is a **specific clinical sign** for RAS:
- Heard best in the epigastrium or flank
- Systolic-diastolic (continuous) pattern indicates significant stenosis
- Sensitivity ~50–60%, but **high specificity** for RAS when present
- Absent in primary hypertension (no structural vascular lesion)

### Comparison Table: Primary vs. Secondary (RAS) Hypertension

| Feature | Primary Hypertension | RAS-Induced Hypertension |
| --- | --- | --- |
| **Abdominal bruit** | Absent | Present (systolic-diastolic) |
| **Age of onset** | Usually >40 years | Can occur at any age; sudden onset suspicious |
| **Renal function** | Normal initially | May be abnormal; asymmetric renal size |
| **LVH** | Common (both have it) | Common (both have it) |
| **Nocturnal dipping** | Often preserved | May be lost (both can lose it) |
| **Plasma renin activity** | Low-normal | Elevated |

**High-Yield:** The **abdominal bruit** is the single most useful bedside discriminator. Its presence should prompt imaging (duplex ultrasound, CT angiography, or MR angiography) to confirm RAS.

### Clinical Pearl

A newly detected bruit in a patient with hypertension, especially if hypertension is sudden-onset or resistant to therapy, is a red flag for RAS and warrants urgent vascular imaging.

**Mnemonic: BRUIT = Best Reason for Ultrasound In renal artery Tension** (secondary hypertension)

Answer

A. Nocturnal blood pressure dipping pattern preserved

Answer

B. Elevated serum creatinine and reduced GFR

Answer

D. Left ventricular hypertrophy on echocardiography

Which feature best distinguishes primary (essential) hypertension from secondary hypertension due to renal artery stenosis?

Explanation

Distinguishing Primary from Secondary Hypertension (RAS)

Key Discriminating Feature

Why This Discriminates

Comparison Table: Primary vs. Secondary (RAS) Hypertension

Clinical Pearl

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Feature	Primary Hypertension	RAS-Induced Hypertension
Abdominal bruit	Absent	Present (systolic-diastolic)
Age of onset	Usually >40 years	Can occur at any age; sudden onset suspicious
Renal function	Normal initially	May be abnormal; asymmetric renal size
LVH	Common (both have it)	Common (both have it)
Nocturnal dipping	Often preserved	May be lost (both can lose it)
Plasma renin activity	Low-normal	Elevated