IS Case 385: Appendicitis with periappendiceal abscess - MR appearance

Sam McCabe, MD

2009 URMC Imaging Sciences
Publication Date: 2010-03-02


Patient is a 51-year-old male with right lower quadrant abdominal pain with palpable abnormality. MRI was requested to evaluate for a mass.


MR images demonstrated a distended appendix with mural enhancement and a small rim-enhancing periappendiceal abscess.


Appendicitis with periappendiceal abscess - MR appearance


Acute appendicitis is common and most often diagnosed by CT. In the setting of a pregnant patient with a nondiagnostic focused US evaluation, however, MRI should be the exam of choice if available. Laboratory values as well as physical exam findings are often unreliable in the pregnant patient, and 11 of 12 US evaluations for appendicitis were nondiagnostic in one small series. If a normal or inflamed appendix can be visualized by MR, appropriate treatment can be expedited and unnecessary diagnostic laparotomy avoided.

In our example, the finding of acute appendicitis was unexpected. The patient was an adult male with a suspected mass. In the setting of a pregnant patient, the use of IV Gadolinium based contrast agents is strongly discouraged. Although no harmful effects to the fetus have been reliably established, the safety of such agents has not been proven. There are no known harmful biologic effects associated with MRI itself, however the unequivocal safety of MRI in pregnancy has not been proven and pregnant patients should be informed of this prior to imaging. Risks to the fetus associated with the ionizing radiation of abdominal CT are felt to be greater than any theoretical risk MR may pose.

Fat suppressed T2-weighted images in at least two orthogonal planes will provide the most diagnostic utility because these sequences will improve contrast between inflammatory edema and adjacent normal abdominal fat.


  1. Cobben LP, Groot I, Haans L, Blickman JG, Puylaert J. MRI for clinically suspected appendicitis during pregnancy. AJR Am J Roentgenol. 2004 Sep;183(3):671-5. PMID: 15333354
  2. Oto A, Srinivasan PN, Ernst RD, et al. Revisiting MRI for appendix location during pregnancy. AJR Am J Roentgenol. 2006 Mar;186(3):883-7. PMID: 16498125

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