Is linear gas in the vagina on a computed tomography (CT) scan normal?

Linear Gas in Vagina on CT: Normal or Abnormal?

Small amounts of linear gas in the vagina seen on a single CT section without vaginal distention are normal, occurring in approximately 11% of female patients. 1

Normal vs. Abnormal Vaginal Air Findings

Normal Findings

• Small amounts of air seen on only one CT section
• No distention of the vagina
• Linear air pattern
• Common finding (11% of female patients)

Abnormal Findings

• Distention of the vagina with air
• Air visualized on multiple CT sections/images
• Large amounts of intravaginal air
• Associated with pathological conditions

Clinical Significance of Abnormal Vaginal Air

When large amounts of vaginal air or air on multiple CT sections is detected, this is highly associated with:

1. Enterovaginal or vesicovaginal fistulas 2

   • Often due to gynecological malignancy and radiation therapy
   • Inflammatory bowel disease
   • Other causes include trauma, surgery, or infection

2. Pelvic malignancy 3

   • In a study of 2,800 female abdomino-pelvic CTs, 23 out of 27 patients with large amounts of intravaginal air had pelvic malignancy

3. Non-tumorous pelvic pathology 3

   • Accounts for a smaller percentage of cases with significant vaginal air

4. Iatrogenic causes 1

   • Tampon in place (symmetrical appearance)
   • Recent pelvic examination or instrumentation

Diagnostic Considerations

When significant vaginal air is detected:

• Correlation with clinical history is essential
• Check for recent pelvic examination, instrumentation, or tampon use
• Evaluate for signs of infection or malignancy
• Consider additional imaging if fistula is suspected:
  • CT vaginography may be useful for suspected fistulas 4
  • MRI for better soft tissue characterization

Pitfalls and Caveats

• Do not confuse normal small linear air in vagina with pathological findings
• Presence of a tampon can cause vaginal distention with air but has a symmetrical appearance, distinguishing it from fistulas 1
• In postpartum patients, small amounts of debris and gas in the endometrial cavity are relatively common (20-25%) in the early postpartum period 5
• Gas in the myometrial defect extending from the endometrium to parametrial tissue along with hemoperitoneum suggests uterine rupture 5

Conclusion

When evaluating linear gas in the vagina on CT:

• Small amounts on a single section without distention are normal
• Larger amounts, distention, or visualization on multiple sections warrant further investigation
• Clinical correlation is essential to determine significance and guide management