A Case Report and Evaluation of Intrauterine Gas of Unknown Origin

Abstract

Introduction

Most reports of intrauterine or endometrial gas have been reported in the setting of underlying gynecologic malignancy or infection. The significance of this case report is to give a presentation of a patient presenting with intrauterine gas who subsequently was identified as having neither an infectious nor malignant cause for such a finding.

Case Presentation

The patient is a 56-year-old postmenopausal woman who presented with “hip pain” and was found to have incidental intrauterine gas on a pelvic computed tomography. She underwent in-office and outpatient hysteroscopies with resection of a submucosal fibroid. Her final pathology was returned as benign, and ultimately no apparent cause for her intrauterine gas was found.

Conclusion

Our case report differs in that our patient was found to have no fistulous abnormalities, was not postpartum or post procedure, and had no evidence of malignancy on permanent pathology. Our primary goal was to evaluate all potential causes for such finding and provide a differential diagnosis that is not commonly presented in current literature reviews. This case report adds to the literature by providing an alternative presentation for incidental intrauterine air that is not commonly reported.

Introduction

The available literature concerning causes and prevalence for intrauterine gas is minimal. Most reports of intrauterine or endometrial gas have been reported in the setting of underlying gynecologic malignancy or infection.¹ However, little is known about the significance of intrauterine gas in the setting of benign pathology. The significance of this case report is to give a presentation of a patient presenting with intrauterine gas who subsequently was identified as having neither an infectious nor a malignant cause for such a finding.

Case Presentation

Our patient is a 56-year-old, postmenopausal woman who presented to the outpatient clinic with complaints of a “uterine mass.” She had previously been seen in the emergency department approximately 5 months prior for complaints of hip pain. She subsequently had a transvaginal ultrasound (TVS) and a computed tomography (CT) abdomen and pelvis scan done at that time (Figure 1), which revealed a uterus measuring 7.1 x 5.4 x 5.5 cm with scattered ring-down artifacts along the endometrial cavity. Additionally, scattered air was observed throughout. The region of the fundus had questionable endometrial thickening measuring up to 2 cm in thickness (Figure 2). Endometrial malignant processes cannot be excluded from the imaging provided.

Figure 1.

A computed tomography abdomen and pelvis scan without contrast showed a sagittal view with diffuse intrauterine air extending from the fundus to the lower uterine segment.

Figure 2.

A transvaginal ultrasound image with a sagittal view revealed a 2.6 x 2.08 x 2.44 cm fundal fibroid.

On her initial evaluation in the office, she was found to have no abnormalities on physical examination. An in-office endometrial biopsy (EMB) was attempted with minimal tissue return. The patient was counseled about the differential diagnoses, including infection versus malignancy. She was recommended for in-office hysteroscopy to evaluate the endometrial cavity and obtain endometrial sampling. Our patient represented 2 weeks later and underwent in-office diagnostic hysteroscopy and was found to have what appeared to be a large submucosal fibroid filling the entirety of the cavity. Findings were reviewed with the patient, and she was offered expectant versus surgical management for her pathology. She ultimately opted for surgical intervention and underwent an operative hysteroscopy and dilation and curettage for removal of the presumed submucosal fibroid. Intraoperative findings included a large submucous fibroid emanating from the left anterior fundal portion of the uterus. This tissue was excised to the level of the uterine wall. Residual tissue was apparent on the uterine wall, which could represent an intramural component of the fibroid. The final pathology report revealed a benign endometrial polyp with submucosal fibroid fragments. No evidence of malignancy was noted on the final pathology reporting. Additionally, there was no commentary made regarding the presence of microbial contributors on pathologic examination.

The patient was discharged home the same day with no immediate postoperative complications. She presented for her postoperative evaluation 3 weeks later with complaints of mild vaginal bleeding for the initial 2 weeks following surgery, which had resolved at the time of her follow-up. Otherwise, the patient recovered appropriately without evidence of complication. She presented for her final evaluation 1 month later for a repeat TVS to assess for residual intrauterine tissue. The patient had no complaints at this final evaluation. The TVS demonstrated no evidence of residual fibroid or intrauterine air.

Discussion

Little is published in current literature about intrauterine air and gas; thus, deciding what to do when found can prove to be challenging for the clinician. When intrauterine air or gas is demonstrated on a CT scan, it most commonly indicates an underlying malignancy or abscess. One retrospective study reviewed 15 patients with intrauterine gas found incidentally on CT. Of the 15 patients, 10 had underlying malignant uterine neoplasms, 2 had colonic carcinoma, and 3 were without evidence of malignancy though indeterminate for etiology.¹ This study suggested intrauterine bacterial metabolism of necrotic neoplastic tissue was the likely cause of intrauterine gas if the patient had an underlying uterine malignancy.¹ Additional differential diagnoses include persistent undiagnosed pelvic inflammatory disease, endometritis, and benign neoplastic degeneration.

If suspecting underlying uterine malignancy, adenocarcinoma of the endometrium is the most common histology and type of uterine cancer. Approximately 75%–90% of endometrial carcinoma presents with abnormal uterine bleeding.² Patients can also present with thickened endometrium, which is often incidental on CT or magnetic resonance imaging. Generally, an EMB will sufficiently capture the diagnosis of uterine cancer if at least 50% of the endometrium is affected by disease. The sensitivity for this method of diagnosis is up to 90%. However, a dilation and curettage procedure, with or without hysteroscopy, is a reasonable method to evaluate these patients but comes at a higher cost, both directly and indirectly. It is unclear at this time the true incidence of intrauterine air in the presence of underlying endometrial carcinoma.

If an EMB is unsuccessful, hysteroscopy remains a reasonable alternative for sampling. When offering an in-office hysteroscopy, the patient should be carefully selected, and appropriate counseling should occur, including indications, risks, benefits, and alternatives. Following the in-office hysteroscopy, which demonstrated a submucosal fibroid, the patient decided on surgical intervention for further treatment of her uterine fibroid via an outpatient operative hysteroscopy and dilation and curettage. A hysteroscopic tissue removal system was used, which allowed for removal of the lesion with tissue resection and specimen extraction.³ This method allowed for a more complete lesion removal and a shorter operative time compared to traditional intrauterine pathology removal with wire loop resectoscope. Randomized trials have demonstrated higher patient satisfaction and faster recovery for office-based hysteroscopies compared to alternative in-hospital procedures.^3,4 It is, again, important to note that intrauterine procedures are contributors to intrauterine air on imaging in the postoperative setting only.

Another possibility for gas production is secondary to microscopic leiomyoma degeneration; however, there is little available information regarding this theory. One case report found a patient with a submucosal fibroid that had undergone necrotic degeneration. The patient ultimately formed a pyomyoma with Bacteroides fragilis infection and subsequent sepsis. As with our report, gas production was evident on imaging,⁵ again, lending to the idea that infection is a common contributor even when systemic signs are absent, as with our patient. Unfortunately, our patient did not undergo specimen culture at the time of resection. It remains unclear if our patient harbored any microbial contributors to her intrauterine gas.

Lastly, intrauterine gas is a common finding by ultrasound in the postpartum period.⁶ Gas is more likely to be found if delivery occurs via Cesarean section or in delivery involving intrauterine manipulation compared to a normal vaginal delivery.^2,6 This air can be related or suspicious for postpartum endometritis; however, ultrasound evidence of air is not diagnostic for endometritis. Postpartum endometritis is primarily a clinical diagnosis based off the presence of 2 of the following signs or symptoms: fever, pain, or tenderness of the uterus or abdomen without other recognized sources, or purulent drainage from the uterus. However, no TVS is required for this diagnosis.

Conclusion

Currently, intrauterine or endometrial air/gas has a greater association with underlying malignancy due to necrotic tissue breakdown and subsequent gas production. Other reported associations have been noted with gynecologic tract fistulas or postprocedural status, or in postpartum patients. Our case report differs in that our patient was found to have no fistulous abnormalities, was not postpartum or post procedure, and had no evidence of malignancy on permanent pathology. Additionally, we do not believe the location of the fibroid to have any mass effect on the internal os of the cervix and subsequent passage of air via the vagina. Our primary goal was to evaluate all potential causes for such a finding and provide a differential diagnosis that is not commonly presented in current literature reviews. There is little to no literature in which intrauterine air is found to not have an association with the above-mentioned etiologies.

Fortunately, for our patient, her pathology returned entirely benign. However, caution should continue to be exercised when intrauterine gas is present. Patients should be counseled that the most likely cause of such a finding is underlying malignancy and/or infection,^7,8 and complete evaluation should occur. Patients with inadequate endometrial sampling should undergo more invasive procedures, such as dilation and curettage, for complete analysis. Tissue and endometrial cultures can be considered at the time of sampling to rule out superimposed infections. Any diagnosed contributor should be treated appropriately, and reimaging should occur following interventions.