Internal Medicine Board Review: Secondary Hypertension
Following up on our earlier post this week detailing the new changes in the JNC8 blood pressure target guidelines, we close out #CardioWeek with a look at another high-yield board topic, secondary hypertension. Compared to primary hypertension, secondary hypertension is much less frequently encountered on the wards and in the clinic. Yet, it seems to be a favorite of the makers of the ABIM board exam, USMLE step, and In-training exam. Therefore, it’s absolutely important to be able to distinguish the specific causes of secondary hypertension and their treatments, as appropriate.
Renal Parenchymal Disease:
- Oliguria (< 400 cc or < 6 cc/kg/day)
- BUN / Creatinine ratio < 20:1
- Fraction Excretion of Sodium (FENa > 1)
- Abnormal Urinalysis
- Most Common Cause of Secondary Hypertension
- Systolic-Diastolic Abdominal Bruit
- History of atherosclerosis
- Recurrent Pulmonary Edema
- Muscle Weakness
- Aldosterone / Renin Ratio > 20:1
- A normal or low levels of Renin with high levels of Aldosterone
- Single Lesion or Bilateral Adrenal Hyperplasia
- Moon fascies
- Central obesity
- Abdominal striae
- Paroxysmal / Episodic rising of the blood pressure
- Associated with Multiple Endocine Neoplasia 2A & 2B
- Urinary Metanephrines / vanillylmandelic acid (VMA)
- CT scan or MRI for the diagnosis of tumor
- Iodine-131 metaiodobenzylguanidine (131 I-MIBG) scintigraphy for extra-adrenal masses
- Dry skin
- Cold Intolerance
- Sleep disturbances
- Polyuria, polydipsia, nausea, vomiting, constipation
- Kidney stones
- Calcium Phosphate mostly
- Neuropsychiatric symptoms
- Confusion, depression, psychosis
- Increased blood pressure in the upper extremities / decreased blood pressure in the lower extremities
- Brachial-Femoral pulse delay
- Rib notching
- Mostly young patients with Turner’s Syndrome (X,0)
- Short Stature
- Streak Ovaries (Primary Amenorrhea)
- Webbed neck
- High Palate
- Congenital Lymphedema
Primary hypertension accounts for 90 to 95% of all cases of hypertension. This form of hypertension was historically named Essential Hypertension because it was believed that patients who have a stroke need high blood pressures to maintain cerebral perfusion in this setting, further it was found that hypertension was the principal cause of strokes.
Renovascular disease is the most common cause of secondary hypertension. In the elderly population with vascular diseases history atherosclerotic changes is principal etiological cause, while in younger patients fibromuscular dysplasia is more common.
Other causes responsible for secondary hypertension are renal parenchymal diseases which may present as clinical oliguria with a BUN/creatinine < 20:1 (in contrast with pre-renal azotemia in which the BUN/creatinine ratio is > 20:1).
Pheochromocytoma is characteristic of episodic or paroxysmal hypertension event in relatively young population. Urinary metanephrines are more sensitive than VMA with a posterior identification of the tumor lesion with a CT scan or MRI, or in the case of a extra-adrenal mass, the utilization of Iodine-131 metaiodobenzylguanidine (131 I-MIBG) scintigraphy will be helpful. Remembering to check for the associated pathologies cluster in MEN 2A and 2B.
Coarctation of the aorta is mostly described in patients with Turner Syndrome (X,0) which can be suspected in a female child with short stature, failure to thrive, primary amenorrhea, congenital lymphedema, rib notching in x-rays are due to increased vascularity of intercostal arteries due to the coarctation as it works as an obstructive congenital lesion. It is important to notice that also thyroid and parathyroid diseases can present with hypertension with flare clinical characteristics of each one of this pathologies.
By reviewing the clues above, identify the correct cause of a patient’s secondary hypertension will be a breeze on the ABIM Internal Medicine board, USMLE Step, or medical residency In-Service exams.