Select initial imaging modality for PA evaluation
STEP 1 — Gather Information
Collect confirmed PA diagnosis (positive screening and confirmatory test), assess need for adrenal venous sampling, check serum creatinine/eGFR, pregnancy status, and prior contrast allergy.
-> If any absolute contraindication to CT (pregnancy or eGFR <30 mL/min/1.73m2) is found, advance to Step 2; otherwise, proceed to Step 3.
STEP 2 — Rule In / Rule Out
Is there an absolute contraindication to CT (pregnancy or eGFR <30 mL/min/1.73m2)?
- Yes: Rule out CT; proceed to evaluate MRI suitability.
- No: Rule in CT as feasible initial imaging.
-> If CT ruled out, go to Step 3; if CT ruled in, go to Step 4.
STEP 3 — Classify or Stratify
Assess MRI availability and safety (no non-MR compatible implants, avoid gadolinium in pregnancy unless essential).
-> If MRI suitable, proceed to order MRI; if MRI not available or contraindicated, consider non-contrast CT with reduced sensitivity and proceed to Step 4.
STEP 4 — Decide
Select the imaging modality: CT if feasible (from Step 2) or MRI if CT contraindicated and MRI suitable (from Step 3); otherwise, use non-contrast CT.
-> Order the chosen imaging study and schedule.
Clinical Guardrails / Mimics / Pitfalls
Do not use CT as initial imaging in pregnant patients due to fetal radiation risk; do not omit intravenous saline hydration in CKD stage G4 or higher before contrast CT to mitigate contrast-induced nephropathy; do not rely on MRI if not readily available causing unnecessary delay in AVS planning; do not use non-contrast CT for adenoma detection as sensitivity drops significantly.
Concrete Clinical Example
A 52-year-old man with hypertension, spontaneous hypokalemia, ARR 350, PAC 80 pg/mL, and positive saline infusion test has no pregnancy or severe CKD (eGFR 68 mL/min/1.73m2). He undergoes contrast-enhanced abdominal CT as the initial imaging study, which reveals a 1.2 cm left adrenal nodule, guiding subsequent adrenal venous sampling.
Source: Japan Endocrine Society clinical practice guideline for the diagnosis and management of primary aldosteronism 2021, Japan Endocrine Society, 2022