HIDA Scan Safety in Pregnancy
HIDA scans should generally be avoided during pregnancy and reserved only for situations where the diagnosis cannot be established by safer imaging modalities (ultrasound or MRI/MRCP) and the clinical benefit clearly outweighs the radiation risk to the fetus. 1
Preferred Imaging Algorithm for Suspected Biliary Disease in Pregnancy
First-Line Imaging
- Abdominal ultrasound without contrast is the preferred initial imaging modality throughout pregnancy for evaluating suspected cholecystitis or biliary pathology 1
- Ultrasound avoids radiation exposure entirely and provides reasonable diagnostic accuracy for gallstones and acute cholecystitis 1, 2, 3
Second-Line Imaging When Ultrasound is Equivocal
- MRI/MRCP without gadolinium is the preferred subsequent imaging modality over any radiation-based study 1
- MRI/MRCP can be considered as initial or subsequent imaging in pregnant patients with suspected acute cholecystitis or cholangitis 1
- MRI is not associated with fetal risk and should be used when ultrasound is non-diagnostic 2, 3
- The National Radiological Protection Board considers it prudent to avoid MRI in the first trimester, though no documented harm exists 1
Radiation Exposure Concerns with HIDA Scans
Why HIDA is Problematic in Pregnancy
- HIDA scans are nuclear medicine studies that expose the fetus to ionizing radiation 4
- While the specific fetal radiation dose from HIDA is not listed in the available guidelines, all nuclear medicine procedures carry radiation risk 1
- The cumulative ionizing radiation exposure should be kept as low as possible and less than 50 mGy throughout pregnancy 1
- Fetuses are particularly vulnerable during periods of rapid cell proliferation, migration, and differentiation 4
When HIDA Might Be Considered
- HIDA is considered the gold standard for diagnosing acute cholecystitis in non-pregnant patients 1
- In pregnancy, HIDA should only be used if both ultrasound and MRI/MRCP are equivocal or unavailable, clinical suspicion for acute cholecystitis remains very high, and the diagnosis would significantly alter management in a way that affects maternal or fetal outcomes 1, 2, 3
- With few exceptions, necessary diagnostic tests should not be withheld from pregnant patients, but safer alternatives must be exhausted first 2, 3
Critical Pitfalls to Avoid
- Do not proceed directly to HIDA when MRI/MRCP is available and can provide the needed diagnostic information 1
- Do not assume that radiation-based imaging is absolutely contraindicated—withholding necessary diagnostic tests can lead to maternal morbidity that also harms the fetus 2, 3
- Ensure the patient requires several hours of fasting before HIDA, which may not be feasible or safe in all pregnant patients 1
- Always document informed consent discussing radiation risks versus diagnostic benefits 4, 5