{'fraction_non_alphanumeric': 0.02135958395245171, 'fraction_numerical': 0.00687221396731055, 'mean_word_length': 5.418355184743742, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Incidental Finding of Decidualized Vesical Endometriosis in an Asymptomatic Obstetrical Patient

A 38-year-old woman, gravida 4, para 2012, presented for routine obstetric anatomic sonography at a gestational age of 20 weeks 1 day. The patient had 2 previous full-term vaginal deliveries and a gynecologic history notable for left salpingo-oophorectomy because of a mature cystic teratoma. A detailed second-trimester anatomic survey was performed according to American Institute of Ultrasound in Medicine guidelines.1 The fetus appeared normal, and there was no suspicion of placenta previa. However, the sonographic findings included a projection into the maternal bladder, first seen on transabdominal sagittal images of the maternal cervix (Figure 1A). This area was reevaluated several times during the course of the transabdominal evaluation and did not appear to change or settle throughout the 20-minute examination. Transvaginal sonography was then performed to better interrogate this suspicious mass. It appeared heterogeneous in echo texture, measuring 2.0 × 2.5 × 1.2 cm, involved the bladder wall, and projected into the bladder cavity. A 3-dimensional rendering was done to look at the polypoid extensions of the mass (Figure 1B). Vascularity was noted when interrogated with color Doppler imaging (Figure 1, C and D). At the time of the sonographic examination the patient reported no history of dysuria, hematuria, or changes in urinary frequency. The differential diagnosis included a benign bladder wall polyp or, less likely, malignancy. The patient remained asymptomatic and was seen 2 weeks later for a cystoscopy. At this time, the patient disclosed that her father had a history of both prostate and bladder cancer. On cystoscopy, the mass was 3.0 cm in size with avascular lobular bumps; it appeared to be pushing the urothelium anteriorly. It was located at the posterior wall of the bladder a few centimeters from the trigone, to the left of the midline. The mass did not have the normal erythematous vascular tissue, as seen in endometriomas, and was thought to be either a leiomyoma of the uterus or bladder; however, malignancy could not be ruled out because biopsy was not performed . Secondary to possible trauma from the cystoscopy, the patient started to have gross hematuria with a clot and intermittent urinary frequency. She underwent a second cystocopic examination 4 weeks later. The size of the main lesion was unchanged; however, the two edematous areas now had a more cauliflower-like appearance. An uncomplicated excisional biopsy was performed after informed consent approval because of the risk of preterm labor, and multiple frozen sections were sent for pathologic examination. The pathologic report confirmed two separate sections containing decidualized tissue with calcification and rare attenuated epithelial cells, consistent with endometriosis. No malignancy was identified. The patient recovered from the biopsy and underwent serial sonographic examinations to ensure no regrowth of the mass. Endometriosis is defined as the presence of endometrial glands and stroma outside the uterine cavity. Vesical endometriosis is rare and occurs in 1% of women with pelvic endometriosis. There are a few reported cases of vesical endometriosis in pregnancy.2–4 Symptoms of vesical endometriosis, which are not specific and may be attributed to recurrent cystitis, include catamenial frequency, urgency, pain at micturition, and vesical tenesmus.5 In symptomatic premenopausal patients, given negative urine culture results, vesical endometriosis should be strongly considered.6 On sonography, vesical endometriosis can appear polypoid or as localized bladder wall thickening. The endometrial tissue may protrude through the hyperechoic layers of submucosa and serosa, simulating bladder cancer; however, it is usually still covered by a rim of serosa and submucosa. There can also be moderate blood flow noted, which can increase during pregnancy.2 The sonographic appearance of vesical endometriosis can make it difficult to distinguish from other conditions in the pregnant patient because of decidualization. Decidualization involves hypertrophy of the endometrial stromal cells, leading to thickening of the normal endometrium induced mainly by progesterone to accommodate pregnancy. Formation of ectopic decidua (deciduosis) is well documented, especially in the ovaries, and can occur in endometriosis tissue or in the normal subceolomic mesothelium. The rapid growth and increased vascularization of ovarian endometriosis with decidualization may mimic malignancy.7 Similarly, rapid growth and increased vascularization can lead to differential diagnostic challenges in vesical endometriosis. The differential diagnosis of a bladder mass in pregnancy includes a benign bladder polyp, bladder leiomyoma, bladder cancer, and placenta percreta. Bladder cancers typically originate from the transient epithelium and occur on the floor of the bladder. Bladder cancer grows in a papillary and multicentric fashion, similar to the appearance of the mass in our patient. A previous review of cases comparing the sonographic appearance of vesical endometriosis and bladder cancer differentiated them on the basis of the thin hyperechoic bladder wall that typically covers the endometrial tissue in endometriosis (Figure 1C).2 In contrast, the