Pregnancy-Specific PPGL Imaging Modality Selection
STEP 1 — Gather Information
Collect gestational age, maternal symptoms (hypertension, palpitations, headache, sweating), biochemical test results (fractionated metanephrines, catecholamines, creatinine-corrected urine), prior imaging findings, and fetal viability status.
STEP 2 — Rule In / Rule Out
If biochemical screening (fractionated metanephrines or catecholamines >3× upper limit) is negative, rule out PPGL and defer imaging; if positive, proceed to imaging evaluation.
STEP 3 — Classify or Stratify
First-line imaging: ultrasound or MRI (both radiation-free). If initial US/MRI is nondiagnostic or further anatomic detail is required for surgical planning, classify as needing advanced imaging.
STEP 4 — Decide
Perform US or MRI as initial study; if advanced imaging is deemed necessary after risk-benefit discussion, obtain informed consent and perform low-dose CT or 123I-MIBG scintigraphy with thyroid blockade (potassium iodide/Lugol’s solution).
Clinical Guardrails / Mimics / Pitfalls
Do not use CT or 123I-MIBG as first-line without attempting US/MRI; avoid gadolinium-based contrast agents in MRI due to fetal safety concerns; never proceed with 123I-MIBG without thyroid blockade and documented informed consent regarding fetal radiation exposure.
Concrete Clinical Example
A 28‑year‑old woman at 18 weeks gestation presents with episodic hypertension and palpitations; urinary metanephrines are 4× ULN. Abdominal ultrasound reveals a 1.5 cm left adrenal lesion; contrast‑free MRI confirms the lesion without metastasis. She is started on α‑blocker therapy and surgical resection is planned for the second trimester.
Source: Clinical Practice Guideline for the Diagnosis and Management of Pheochromocytoma and Paraganglioma, Japan Endocrine Society, 2025, doi:10.1507/endocrj.EJ25-0165