Ppgl Initial Imaging Modality Selection

Initial PPGL Imaging Modality Selection for Tumor Localization

STEP 1 — Gather Information

Collect biochemical test results (fractionated metanephrines/catecholamines ≥3× ULN), clinical presentation (symptoms, hypertension), suspected tumor location based on biochemistry (noradrenaline dominance suggests extra-adrenal/PGL), patient age, pregnancy status, renal function, availability of CT, MRI, 123I-MIBG scintigraphy, and 18F-FDG PET, and any contraindications (iodine allergy, claustrophobia, implanted devices). Proceed to step 2.

STEP 2 — Rule In / Rule Out

Is there a need to avoid ionizing radiation (pregnancy, pediatric patient, or requirement for frequent follow‑up imaging)? If yes, proceed to step 4 for MRI selection; if no, proceed to step 3.

STEP 3 — Classify or Stratify

Is anatomic detail required for surgical planning (e.g., assessing tumor size, exact location, relationship to vessels/organs, or differentiating adrenal vs extra‑adrenal)? If yes, proceed to step 4 for CT/MRI selection; if no, proceed to step 4 for functional imaging selection.

STEP 4 — Decide

• If MRI was chosen in step 2: order contrast‑enhanced MRI of the abdomen/pelvis (or dedicated head/neck MRI if skull‑base PGL suspected).
• If CT/MRI was chosen in step 3:
  • If no contraindication to iodinated contrast and renal function adequate, order contrast‑enhanced CT of the abdomen/pelvis (adrenal protocol).
  • If contrast contraindicated or renal insufficiency, order MRI instead.
• If functional imaging was chosen in step 3:
  • If 123I‑MIBG scintigraphy is available and thyroid blockade can be administered, order 123I‑MIBG whole‑body scan.
  • Otherwise, order 18F‑FDG PET/CT (particularly if SDHx pathogenic variant suspected).
  Schedule the study and inform the patient of preparation requirements.

Clinical Guardrails / Mimics / Pitfalls

Do not rely on functional imaging alone for anatomic localization needed for surgery; do not perform CT with iod contrast in pregnancy without obstetric clearance; do not omit thyroid blockade before 123I‑MIBG to avoid thyroid uptake and medullary thyroid cancer confounders; do not interpret 18F‑FDG PET uptake in the neck/supraclavicular areas without considering brown adipose tissue; do not use MRI if patient has non‑MRI‑compatible implants or severe claustrophobia; do not delay imaging after biochemical confirmation as timely localization guides preoperative α‑blocker titration.

Concrete Clinical Example

A 45‑year‑old man with paroxysmal hypertension, headaches, and palpitations has plasma‑free metanephrines 4× ULN, confirming PPGL. He is non‑pregnant, with normal renal function, and requires anatomic detail for laparoscopic adrenalectomy. Step 1: gathers data. Step 2: no radiation avoidance need. Step 3: anatomic detail required. Step 4: orders contrast‑enhanced CT abdomen/pelvis. Imaging shows a 3.2 cm right adrenal lesion with early arterial enhancement and washout, guiding surgical planning.

Source: Japan Endocrine Society Clinical Practice Guideline for the Diagnosis and Management of Pheochromocytoma and Paraganglioma 2025, Japan Endocrine Society, 2025, doi:10.1507/endocrj.EJ25-0165