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Three Part Question

In [pregnant patients with suspected appendicitis], how useful is [abdominal MRI] in [ruling in or ruling out acute appendicitis]?

Clinical Scenario

You suspect appendicitis when a 20 year old female, 25 weeks pregnant, presents with right lower quadrant abdominal pain, vomiting, and low grade fever. An abdominal ultrasound is performed, but the appendix was not visualized, and the study is read as inconclusive. Knowing that there is a 25-50% negative laparotomy rate for appendicitis in pregnant patients you are hesitant to recommend surgery. You wonder if an MRI would be helpful in clarifying the diagnosis.

Search Strategy

MEDLINE 1990 to Jan 2009 using EBSCOhost interface. [exp appendicitis/mh or appendectomy or appendix] and [exp magnetic resonance imaging/mh or mri or magnetic resonance imaging] and [exp pregnancy/mh or pregnancy or pregnant]. Limits: Humans, English.

Search Outcome

31 papers were found; 4 relevant studies are reviewed below.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Cobben et al. 2004 Netherlands	12 pregnant patients over 3 year period with clinically suspected appendicitis that underwent MRI. Final diagnosis by surgical findings, pathology, patient follow-up.	Retrospective cohort	Appendix not visualized in 2 patients (16.7%), neither had appendicitis.	Of the remaining 10, sensitivity 100%, specificity 100%.	Small numbers. Unclear follow-up method.
Oto et al. 2005 USA	23 pregnant patients over 30 month period with acute right lower quadrant pain that underwent MRI. Final diagnosis by surgical findings, pathology, medical record review.	Retrospective cohort	Appendix not visualized in 3 patients (13%), one having appendicitis.	When appendix was visualized, sensitivity 100%, specificity 100%.	Small numbers. Limited follow-up data after discharge on 14 patients.
Pedrosa et al. 2006 USA	51 consecutive pregnant patients with suspected appendicitis over 5 year period underwent MRI. Oral contrast given to all patients. Final diagnosis by surgical findings, pathology, clinical follow-up.	Retrospective cohort	Three studies (6%) read as inconclusive.	Overall (including inconclusives) sensitivity 100%, specificity 93.6%.	Some radiologists aware of clinical and ultrasound findings. Imaging studies were later retrospectively reviewed and some interpretations were changed. Low incidence of appendicitis in their population compared to other studies.
Israel et al. 2008 USA	33 pregnant patients over 23 month period with clinically suspected appendicitis that underwent MRI. Final diagnosis by pathology and medical record review.	Retrospective cohort	16 indeterminate studies with appendix non-visualized (48%), one of which had appendicitis.	Of the remaining 17, sensitivity 100%, specificity 100%. If indeterminates included, sensitivity drops to 80%.	Only 5 patients (15%) in 3rd trimester. Radiologists aware of clinical and ultrasound findings. Unclear follow-up method.

Comment(s)

All studies are small in patient numbers and suffer from selection bias. Some studies had incomplete patient follow up. MRI technique, interpretation, and gold standard for diagnosis were not standardized across all studies. In many negative studies, MRI was able to identify an alternative diagnosis to explain the patient’s symptoms. MRI may definitively identify appendicitis or an alternative diagnosis, but inconclusive studies are problematic. Due to the small size of these studies and varied approaches to diagnosis, further study is warranted.

Clinical Bottom Line

In the case of a pregnant patient with suspected appendicitis, MRI is a valuable tool.

References

1. Cobben LP, Groot I, Haans L, Blickman JG, Puylaert J. MRI for clinically suspected appendicitis during pregnancy. AJR Am J Roentgenol Sep;183(3):671-5
2. Oto A, Ernst RD, Shah R, Koroglu M, Chaljub G, Gei AF, Zacharias N, Saade G. Right-lower-quadrant pain and suspected appendicitis in pregnant women: evaluation with MR imaging--initial experience. Radiology 2005 Feb;234(2):445-51
3. Pedrosa I, Levine D, Eyvazzadeh AD, Siewert B, Ngo L, Rofsky NM. MR imaging evaluation of acute appendicitis in pregnancy. Radiology 2006 Mar;238(3):891-9.
4. Israel GM, Malguria N, McCarthy S, Copel J, Weinreb J. MRI vs. ultrasound for suspected appendicitis during pregnancy. J Magn Reson Imaging 2008 Aug;28(2):428-433