1. 
   

   Which patients should be evaluated for secondary causes of hypertension in the inpatient setting?

   
   
2. 
   

   What are the most common secondary causes of hypertension in hospitalized patients?

   
   
3. 
   

   What screening and diagnostic tests are best for each?

   
   
4. 
   

   What specific therapy or therapies are currently recommended?

   
   
5. 
   

   What follow-up should be recommended after discharge?

Hypertension affects 29% of the American public. Its prevalence among hospitalized patients is much higher. Hospitalized patients are older than the general population, and the prevalence of hypertension is 67% in those aged 60 years and older. In addition, hypertension is a major risk factor for the cardiovascular and renal diseases that lead to inpatient admission. Poorly controlled hypertension among general medical inpatients is most often related to other conditions, such as pain, agitation from delirium, and substance withdrawal. Secondary hypertension has a prevalence of less than 5% in the general population, but is more common among inpatients. This is due to three types of selection bias: (1) negative screening for secondary hypertension in outpatients, who are seldom hospitalized for the evaluation and are at low risk of hospitalization for other causes; (2) patients admitted for hypertensive emergencies; and (3) patients with secondary hypertension admitted for diagnostic and therapeutic procedures, often for other diagnoses. For example, 13% of patients undergoing cardiac or peripheral arterial catheterization have a documented stenosis in a renal artery (discovered during “drive-by angiograms”). Secondary causes of hypertension should at least be considered in hypertensive inpatients, especially younger ones. This ensures that these patients are assessed at least once for secondary hypertension during their lifetime. In addition, some causes, such as pheochromocytoma, Conn adenoma, and fibromuscular dysplasia, are amenable to cure, or at least long-term amelioration. This obviates the need to take antihypertensive medications over a long period of time, improving the cost-effectiveness of screening young patients.

The major circumstance in which secondary hypertension leads to hospital admission is a hypertensive emergency (severely elevated blood pressure and acute, ongoing target-organ damage). These patients have a high prevalence of secondary hypertension, and the hypertensive emergency is often the first real clue to the presence of a secondary cause. After stabilization of these patients with short-acting, intravenous antihypertensive drugs, attention should be focused on developing an appropriate antihypertensive drug regimen and excluding secondary hypertension.

Less commonly, patients are admitted electively for diagnostic or therapeutic procedures related to secondary hypertension. Many of these are “23-hour admissions,” and do not require major attention from hospital-based physicians, except those directly involved in the procedure. Examples include patients with possible hyperaldosteronism and bilateral adrenal nodules admitted for adrenal venous sampling, claustrophobic patients with possible pheochromocytoma admitted for magnetic resonance imaging of the abdomen after intravenous sedation, and patients with a high probability of fibromuscular renovascular hypertension sent for renal angiography with possible angioplasty.

Occasionally, secondary hypertension becomes an issue in patients admitted for diagnostic or therapeutic procedures only indirectly related to hypertension. Examples include hypertensives undergoing evaluation of incidentally discovered adrenal masses, individuals who have incidental or “drive-by” renal angiograms after a planned coronary or carotid catheterization, and patients who have an increase of greater than 25% in serum creatinine after administration of an angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB). Hospitalists caring for these patients should pursue appropriate diagnosis and treatment of secondary hypertension before discharge.

The most common secondary causes of hypertension in hospitalized patients are listed in Table 253-1. Despite a perennial enthusiasm in internal medicine for esoteric diseases, it should be noted that the most common type of hypertension in hospitalized patients is still primary (formerly essential) hypertension.

Chronic Kidney Disease

This secondary cause of hypertension differs from the others in at least two respects: it is usually not remediable, and it may be both a cause and a consequence of hypertension. Chronic kidney disease is defined as three months or more of either an estimated glomerular filtration rate (eGFR) of less than 60 mL/min/1.73 m2, or kidney damage defined as pathologic abnormalities, abnormal imaging studies, or elevated blood or urine markers of kidney injury (usually albuminuria > 30 μg/mg creatinine in a first-morning voided urine specimen). In large population-based studies, more advanced stages of chronic kidney disease are linked to greater risks of death and hospitalization. As a result, this secondary cause of hypertension is thought to be about 5- to 10-fold more common in hospitalized patients than in the general United States population.

Testing for chronic kidney disease is part of the admitting process for essentially every inpatient, with a serum creatinine (and in most hospitals, a calculated eGFR, based on the most recent update of the Modification of Diet in Renal Disease equations) and a urinalysis. Occasionally, the urinalysis can be falsely negative for protein if performed on a very dilute sample. If this is suspected, a first-morning voided urine specimen should be obtained to measure the albumin-to-creatinine ratio.

Intensive lowering of blood pressure is an effective means to prevent or delay the progression of chronic kidney disease to end-stage renal disease. Most authorities recommend that patients with chronic kidney diseases should have frequent urinalyses and determinations of eGFR, a lower-than-usual blood pressure goal (< 130/80 mm Hg), and an ACE inhibitor or an ARB as part of their medication regimen, if possible.

Primary Hyperaldosteronism