Radiographic appearance of pyometra on computer tomography mimicking pelvic abscess

Pyometra is an uncommon gynecologic condition. We report a case of pyometra in a 64-year-old woman with cervical carcinoma. The pyometra appeared as a pelvic abscess on computer tomography (CT) and transrectal ultrasound guided drainage was performed twice before the correct diagnosis was made. A 64-year-old woman with diabetes mellitus was admitted to a medical ward because of hypoglycemia and vomiting in February 2002. Physical examination revealed a distended but nontender abdomen. She was afebrile and her white cell count was 10.5×109/L. Abdominal X-ray with oral contrast showed dilated small bowels. CT of the abdomen and pelvis revealed a 5-cm-diameter fluid collection with a 3.5-mm-thick wall in the central pelvis involving the pouch of Douglas (Figure 1). No comment was made on the size and appearance of the uterus, tubes and ovaries. The provisional diagnosis was pelvic abscess and the patient was transferred to the surgical ward. Pelvic CT showing a thin wall fluid collection in the central pelvis. The patient was put on broad-spectrum antibiotics and the abdominal distension partially resolved. Ultrasound-guided transrectal aspiration of the thick pelvic collection was difficult and only 5-mL pus could be drained. Another CT scan performed 5 days later revealed similar findings. The uterus was again not mentioned in the report. A second attempt at ultrasound-guided transrectal aspiration yielded 40 mL of pus but the drainage was incomplete. A transabdominal ultrasound scan performed 18 days after the first aspiration procedure revealed a 4-cm-diameter loculation behind the bladder in the pelvis. Further drainage, transabdominally or transrectally, was not advisable because of the intervening loops of bowel. A gynecologist was consulted 33 days after the initial presentation. The patient did not complain of any vaginal discharge or postmenopausal bleeding. Speculum examination revealed an atrophic vagina and cervix with no pus or blood. The uterus appeared enlarged on pelvic examination. Transvaginal ultrasound examination revealed a hypoechogic collection in the uterine cavity. The diagnosis of pyometra was confirmed as pus was drained from the uterine cavity after passing a Pipelle endometrial sampler into the uterus. Drainage was completed by dilatation of the cervix to Hegar 9 under general anesthesia. Uterine curettage was performed at the same time to rule out intrauterine pathology. Histological examination of the uterine curettage showed squamous epithelial fragments with severe dysplasia. Microbiological examination of the pus revealed no growth. Colposcopic examination and biopsies revealed CIN III and VAIN III. Loop electrosurgical excision was performed and the foci of severe squamous dysplasia and early stromal invasion were noted. In view of stage 1a1 cervical carcinoma, extensive VAIN III and poor diabetic control, the patient was treated with brachytherapy. The patient remains well with no evidence of recurrent disease 1 year after the treatment was completed. Transrectal drainage is usually used to treat prostatic abscesses in men and appendiceal abscesses in children (1). It has also been used to drain pelvic abscesses resulted from pelvic inflammatory disease (PID) or gynecologic surgery in women (2). Transrectal drainage provides a better access to pelvic abscesses that are located too posterior to be amenable by the transvaginal approach. Patients' tolerance to the transrectal approach also seems to be better (3). In the present case, the pyometra was mistaken as a deep pelvic abscess and was drained twice transrectally. Indeed, the clinical presentation in this patient was not typical for pelvic abscess as she did not have high fever, abdominal tenderness or marked leukocytosis. On the contrary, patients with pyometra are usually afebrile, presented with vaginal discharge or bleeding, and their white cell count is usually normal (4). Correct diagnosis was not made in this patient because she did not have gynecologic symptom such as vaginal bleeding or discharge. Clinicians should note that pyometra resulted from blockage of the cervical canal resulting in accumulation of secretion in the uterine cavity. In most cases the cervical blockage is incomplete and patients would notice occasional vaginal discharge. However, in patients with carcinoma or previous radiotherapy, the cervical blockage can be complete and patients may not have symptoms of vaginal discharge (5). Pyometra might have been expected to appear on the scan as a fluid collection bounded by a thick myometrial wall. However, with progressive distension of the uterus, overstretching and thinning of the myometrial wall follows. Pyometra often appear, therefore, as a collection bounded by thin surrounding walls and simulate pelvic abscesses. A high index of suspicion should be raised when pelvic collection is noted in the absence of an identifiable uterus. Although the uterus is atrophic and small after menopause and may not be obvious on CT, identification of the uterus is always possible with transvaginal ultrasound. There are few data in the literature regarding whether a pelvic abscess should be drained by the transrectal/trans-vaginal or abdominal route. The advantages of the former are avoidance of general anesthesia and the procedure can be repeat if necessary with little risk. However, it may be difficult to distinguish between a pelvic abscess and other disorders such as torsion of an ovarian tumor base on clinical features alone. Inadvertent drainage of an ovarian tumor may lead to spillage of its contents into the abdominal cavity, which is undesirable. Therefore, it is better to reserve transvaginal or transrectal drainage for cases of postoperative abscess.