Peritonitis From Ruptured Lipid-Poor Dermoid: Struma Ovarii.

Mature cystic teratoma (MCT) is a common benign ovarian germ cell tumor. It is more predominantly seen in premenopausal women and contains at least two or more well-differentiated germ cell layers. It is termed a dermoid cyst if the ectodermal tissue is the predominant component. The complications of a dermoid cyst include torsion, malignant degeneration, rupture, and infection. The incidence of a ruptured dermoid cyst is around 1%-2% resulting in chemical aseptic peritonitis from spillage of the cyst contents. Usual clinical presentation is with diffuse abdominal or pelvic pain and abdominal distension. Around 93-96% of dermoid cysts demonstrate fat in the cyst cavity however, minimal or no fat poses diagnostic challenges. In this case, we discuss a rare case of spontaneously ruptured lipid-poor and thyroid tissue-rich left ovarian dermoid presenting with chemical peritonitis. Special magnetic resonance (MR) Imaging sequences such as fat saturation imaging, chemical shift imaging, and gradient-echo imaging assist in detecting scant amounts of fat in the cyst cavity or cyst wall.