624 Letters to the Editor 7. Okai T, Kobayashi K, Ryo E, Kagawa H, Kozuma S, Taketani Y. Transvaginal sonographic appearance of hemor- rhagic functional ovarian cysts and their spontaneous regression. Int J Gynaecol Obstet 1994; 44: 47–52. 8. Brown DL, Doubilet PM, Miller FH, Frates MC, Laing FC, DiSalvo DN, Benson CB, Lerner MH. Benign and malignant ovarian masses: selection of the most discriminating gray- scale and Doppler sonographic features. Radiology 1998; 208: 103–110. 9. Schelling M, Braun M, Kuhn W, Bogner G, Gruber R, Gnirs J, Schneider KT, Ulm K, Rutke S, Staudach A. Combined trans- vaginal B-mode and color Doppler sonography for differential diagnosis of ovarian tumors: results of a multivariate logistic regression analysis. Gynecol Oncol 2000; 77: 78–86. 10. Redman CWE, Jones SR, Luesly DM, Nicholl SE, Kelly K, Buxton EJ, Chan KK, Blackledge GRP. Peritoneal trauma releases CA 125? Br J Cancer 1988; 58: 502–504. Transvaginal sonographic appearance of anaerobic endometritis The diagnosis of endometritis is often a challenging task, as signs and symptoms are non-specific and the sonographic findings are variable, including thickening and irregularity of the endometrium and fluid or debris accumulated within the endometrial cavity 1 . We report a case in which the diagnosis was suggested by the transvaginal sonographic demonstration of gas within the endometrial cavity. A 39-year-old woman was referred to our hospital for infertility. A transvaginal ultrasound scan revealed a subserous/partly intramural leiomyoma measuring 4 cm on the right uterine cornu. The right ovary was slightly enlarged due to the presence of a luteal cyst. The preoperative CA 125 plasma level was above the normal upper value (113 IU/mL). On bimanual pelvic examination the uterus was found to be enlarged and irregular in morphology. After counseling a laparoscopic myomectomy was scheduled. At laparoscopy both adnexa appeared to have normal morphology and dimensions. The cul-de-sac was obliterated and several endometriotic implants 2–10 mm in diameter were seen dispersed throughout the pelvic peritoneum. The uterus showed a slight prominence on the right side that was thought to be the subserous/intramural myoma identified at sonography. Enucleation of the mass was performed with a monopolar hook; it proved difficult due to the absence of a plane of cleavage from the surrounding myometrium. The incision extended to the endometrial cavity, and a small amount of chocolate- like liquid was seen leaking from the uterus. The myometrium and serosa were sutured. Pathology of the specimen revealed an adenomyoma within several small leiomyomas. Two days after surgery the patient developed pelvic pain and high, remittent fever, and was treated with a combination of antibiotics including tobramicin, ceftriaxon, imipenem and cilastatin. Her general condition worsened as the fever was unresponsive to antibiotics. At transvaginal sonography the uterus was found to be enlarged (longitudinal diameter, 11 cm; anteroposterior diameter, 7 cm; transverse diameter, 7 cm) with an irregular myometrial echogenicity that, in the light of the pathological diagnosis, was considered to be compatible with diffuse adenomyomatosis. The endometrial cavity was filled with a layer of high-level echoes casting a shadow, suggesting the presence of gas accumulated within the endometrial cavity (Figure 1). Both ovaries had normal volume and morphology. Moreover, on power Doppler a highly vascularized complex mass was seen beside the right ovary, with the appearance of an inflamed appendix 2 . No free fluid was detected in the pouch of Douglas. An explorative laparotomy confirmed the presence of a pneumatometra and a pelvic abscess: the uterus appeared enlarged and softened, with a grayish serosal surface, and during the maneuvers a crackling was perceived, as if air were entrapped inside the cavity. Removal of the uterus, both Fallopian tubes, appendix and right ovary was performed. Pathology revealed acute inflammation of the appendix extending to the right salpinx. Acute endometritis was histologically demonstrated by the presence of more than five neutrophils visible per 400 × field in the superficial epithelium, and more than one plasma cell per 120 × field in the endometrial tissue 3 (Figure 2). The patient soon recovered after laparotomy and was discharged from the hospital 14 days later. The presence of gas in the uterine cavity has been reported following spontaneous, uncomplicated vaginal delivery 4,5 . This is a normal finding at least for the first 3 weeks of the puerperium and does not indicate the presence of endometritis. It should, however, be suspected in a patient complaining of fever and pelvic pain in whom a pneumatometra is demonstrated. Although such a condition has been previously documented at Figure 1 Transverse vaginal sonographic image of the uterus. The endometrial stripe is thick and hyperechoic and difficult to delineate with respect to the surrounding myometrium. Several cones of shadow from the endometrium obscure the posterior uterine wall. This appearance is suggestive of the presence of endometritis associated with gas formation (arrow) within the endometrial cavity. Copyright  2003 ISUOG. Published by John Wiley & Sons, Ltd. Ultrasound Obstet Gynecol 2003; 21: 619–625.