Evaluation of Hypertension with Electrolyte Abnormalities and Renal Dysfunction

Primary Aldosteronism

Primary aldosteronism is present in roughly 20 % of patients with resistant hypertension, making it the leading diagnosis to consider in hypertensive individuals with hypokalemia. 1
Hypokalemia usually appears late; many affected patients initially have normal serum potassium, so its presence signals more advanced disease. 1
An elevated serum creatinine often reflects hypertension‑mediated kidney injury caused by chronic aldosterone excess. 1
Screening: the first‑line test is the aldosterone‑to‑renin ratio (ARR); however, hypokalemia can depress aldosterone levels and produce false‑negative ARR results. 2
Confirmation: if the ARR is elevated, verify the diagnosis with a 24‑hour urinary aldosterone measurement performed during high dietary sodium intake. 1

An elevated creatinine may indicate bilateral renal artery disease or ischemic nephropathy in this context. 3
Clinical clues that raise suspicion include:
- Hypertension onset before age 30 or after age 55
- Presence of an abdominal bruit (especially with a diastolic component)
- Accelerated or resistant hypertension
- Acute decline in renal function after initiating an ACE inhibitor. 3
Imaging screening should begin with renal Doppler ultrasound that includes bilateral renal arterial resistive‑index assessment; if suspicion remains high, proceed to CT or MR angiography. 2

Although pheochromocytoma accounts for only 0.1–0.6 % of all hypertension cases, it is over‑represented among patients with resistant hypertension. 1
Typical presentation includes paroxysmal hypertension, headache, palpitations, pallor, and sweating. 1
Electrolyte disturbances may arise secondary to catecholamine‑induced renal dysfunction. 1
Diagnostic testing: measure 24‑hour urinary or plasma metanephrines and normetanephrines. 2

Excess cortisol produces hypertension with hypokalemia via its mineralocorticoid activity. 4
Look for truncal obesity, impaired glucose tolerance, and purple abdominal striae as clinical clues. 3
Screening tests include a 24‑hour urinary free cortisol measurement or a low‑dose dexamethasone suppression test. 2

Glucocorticoid‑remediable aldosteronism (GRA) typically presents in childhood and should be considered in early‑onset severe hypertension with a family history. 4

Measure the aldosterone‑to‑renin ratio as the primary screen for primary aldosteronism, recognizing that hypokalemia and certain antihypertensive agents (β‑blockers, ACE inhibitors, ARBs) can alter the result. 2

Renal Doppler ultrasound is the first‑line imaging modality to evaluate for renovascular disease and assess kidney anatomy. 2
CT or MR angiography is recommended when renovascular hypertension is strongly suspected after ultrasound evaluation. 2
If primary aldosteronism is biochemically confirmed, obtain adrenal CT or MRI to localize an adenoma or hyperplasia. 4

Correct hypokalemia before performing the aldosterone‑to‑renin ratio, because low potassium suppresses aldosterone secretion and can yield false‑negative screening results. 2

The European Society of Cardiology recommends measuring serum creatinine, calculating eGFR using the CKD-EPI equation, and obtaining a urine albumin-to-creatinine ratio (UACR) immediately to evaluate renal impairment in hypertensive patients 5, 6
Serum creatinine with eGFR calculation using the race-free CKD-EPI equation is preferred over MDRD or Cockcroft-Gault 5, 7
Urine albumin-to-creatinine ratio (UACR) on a spot urine sample should be used to quantify proteinuria 5, 6, 7
Complete urinalysis with microscopy should be performed to evaluate for active sediment (RBC casts, dysmorphic RBCs suggesting glomerulonephritis) versus bland sediment typical of hypertensive nephrosclerosis 8
Serum electrolytes, including potassium, should be measured, as hyperkalemia may develop with ACE inhibitor/ARB therapy 7, 9
A 12-lead ECG should be performed to assess for left ventricular hypertrophy and guide treatment choice 5, 6

Chronic kidney disease (CKD) is defined as eGFR <60 mL/min/1.73 m² or albuminuria ≥30 mg/g (≥3 mg/mmol) present for at least 3 months 5
The combination of reduced eGFR and proteinuria indicates greater cardiovascular and renal risk than either abnormality alone 9
Albuminuria can be classified as normal (UACR <30 mg/g), moderately elevated (UACR 30-299 mg/g), or severely elevated (UACR ≥300 mg/g) 7

Renal ultrasound with Doppler examination should be considered in hypertensive patients with CKD to assess kidney structure, determine causes of CKD, and exclude renoparenchymal and renovascular hypertension 5
CT or magnetic resonance renal angiography are alternative options 5

When secondary hypertension is suspected based on clinical presentation, appropriate screening should include renovascular disease screening, primary aldosteronism, pheochromocytoma, Cushing's syndrome, and thyroid disease 10, 8
Renovascular disease screening can be performed using renal Doppler ultrasound, CT angiography, or MR angiography, particularly in older patients, smokers, those with peripheral arterial disease, or unexplained renal insufficiency 10, 8

If moderate-to-severe CKD is diagnosed (eGFR <60 mL/min/1.73 m² or UACR ≥30 mg/g), repeat measurements of serum creatinine, eGFR, and UACR at least annually 5, 6
After initiating ACE inhibitor or ARB therapy, recheck serum creatinine and potassium within 7-14 days 7, 9, 8

Refer to nephrology when eGFR <30 mL/min/1.73 m², uncertainty about the etiology of kidney disease exists, rapidly progressive kidney disease is present, active urinary sediment suggests glomerulonephritis, or difficult management issues arise 7, 8