Suspected Appendicitis in a 22-Week Pregnant Patient
A 24-year-old woman at 22 weeks' gestation presents to the emergency department with 12 hours of periumbilical pain that migrated to the right lower quadrant. Her temperature is 37.9°C, white blood cell count is 14.2 × 10⁹/L, and obstetric ultrasound is normal. Graded compression ultrasound of the right lower quadrant is inconclusive because of bowel gas and the gravid uterus. The emergency physician requests MRI to evaluate for appendicitis. The patient is anxious about 'radiation and dye' and asks whether the scan can hurt the baby. She is comfortable supine for now but has had episodes of light-headedness when lying flat. The MRI slot is 30 minutes on a 1.5 T scanner. The order reads 'MRI abdomen with and without gadolinium' because the ordering clinician wants 'the best look.' No contrast allergy, no renal disease. The patient has an IV but no laboratory results beyond a basic metabolic panel from admission.
1. Should gadolinium be administered as ordered? Explain your reasoning.
Read the worked answer
No. MRI without intravenous gadolinium is the appropriate first-line study for suspected appendicitis in pregnancy when ultrasound is inconclusive. Gadolinium crosses the placenta, and although the evidence for fetal harm is limited, it is reserved for cases in which the diagnosis cannot be made without it and the benefit clearly outweighs the fetal risk. Appendicitis can be evaluated with non-contrast T2-weighted and diffusion-weighted sequences; the ordering clinician's wish for 'the best look' is not by itself an indication.
If a complication such as abscess or perforation is suspected and the non-contrast study is insufficient, discuss the case directly with the radiologist and the obstetric team. A macrocyclic agent could be considered case by case, but it should not be given routinely or simply because it was ordered. Document the decision, the patient's questions, and the fact that the study was converted to non-contrast. Notify the emergency physician before the patient leaves the department so that the change in plan is clear.
2. What protocol, positioning, and safety measures would you use?
Read the worked answer
Use a rapid non-contrast abdomen and pelvis protocol tailored to the appendix: coronal and axial single-shot fast spin-echo T2 sequences, axial T2 with fat saturation, and diffusion-weighted imaging. Keep the study within about 20–30 minutes and avoid unnecessary sequences.
Positioning matters because of the risk of inferior vena cava compression. Place her in a left lateral decubitus position or supine with a wedge under the right hip, and monitor for light-headedness, nausea, or hypotension. If she becomes symptomatic, reposition her and check vital signs. Use earplugs or headphones for acoustic protection, a call bell, and clear instructions. Keep SAR within institutional limits for pregnancy and avoid sedation unless specifically arranged.
Confirm that she has no ferromagnetic implants or other MRI contraindications. Do not give gadolinium. If contrast becomes essential after radiologist review, verify renal function first and document the risk-benefit discussion. Communicate the non-contrast plan to the emergency physician and document her tolerance of the study.
3. How would you explain the study to the patient and document the encounter?
Read the worked answer
Explain that MRI does not use ionizing radiation and that the scan is being done without contrast dye because the non-contrast study is appropriate for appendicitis in pregnancy. Be honest that the machine is loud and may feel warm, that she will have a call bell, and that she should tell you immediately if she feels dizzy or uncomfortable. Invite questions about the baby and correct the misconception that all MRI requires dye.
Document:
- Gestational age and the inconclusive ultrasound result.
- The order as written and the decision to perform MRI without gadolinium.
- The radiologist's involvement in that decision.
- Positioning, monitoring, and any symptoms during the scan.
- The patient's informed understanding and questions.
- Notification of the emergency physician that the study was converted to non-contrast.
If the study is nondiagnostic, document that and discuss the next step with the radiologist and emergency physician rather than automatically adding contrast. The record should make clear that the non-contrast choice was deliberate and safety-based, not an omission.