Infectious Risks of Transvaginal Ultrasound

Transvaginal ultrasounds carry infection risks, although published estimates of rates are lacking. With the Commonwealth of Virginia poised to mandate ultrasounds prior to an abortion, and other states certainly to follow, it is important to review the CDC guidelines for the cleaning and disinfection of vaginal probes. There are also other issues at stake, like the doctor-patient relationship. Mandatory reporting of all infections secondary to this procedure should be considered.

UPDATE: Image removed.

From the CDC-HICPAC "Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008"

Vaginal probes are used in sonographic scanning. A vaginal probe and all endocavitary probes without a probe cover are semicritical devices because they have direct contact with mucous membranes (e.g., vagina, rectum, pharynx). While use of the probe cover could be considered as changing the category, this guideline proposes use of a new condom/probe cover for the probe for each patient, and because condoms/probe covers can fail (195, 197-199), the probe also should be high-level disinfected. The relevance of this recommendation is reinforced with the findings that sterile transvaginal ultrasound probe covers have a very high rate of perforations even before use (0%, 25%, and 65% perforations from three suppliers). (199)

One study found, after oocyte retrieval use, a very high rate of perforations in used endovaginal probe covers from two suppliers (75% and 81%) (199), other studies demonstrated a lower rate of perforations after use of condoms (2.0% and 0.9%) (197 200). Condoms have been found superior to commercially available probe covers for covering the ultrasound probe (1.7% for condoms versus 8.3% leakage for probe covers) (201). These studies underscore the need for routine probe disinfection between examinations. Although most ultrasound manufacturers recommend use of 2% glutaraldehyde for high-level disinfection of contaminated transvaginal transducers, the this agent has been questioned (202) because it might shorten the life of the transducer and might have toxic effects on the gametes and embryos (203).

An alternative procedure for disinfecting the vaginal transducer involves the mechanical removal of the gel from the transducer, cleaning the transducer in soap and water, wiping the transducer with 70% alcohol or soaking it for 2 minutes in 500 ppm chlorine, and rinsing with tap water and air drying (204). The effectiveness of this and other methods (200) has not been validated in either rigorous laboratory experiments or in clinical use. High-level disinfection with a product (e.g., hydrogen peroxide) that is not toxic to staff, patients, probes, and retrieved cells should be used until the effectiveness of alternative procedures against microbes of importance at the cavitary site is demonstrated by well-designed experimental scientific studies. Other probes such as rectal, cryosurgical, and transesophageal probes or devices also should be high-level disinfected between patients.

As with other high-level disinfection procedures, proper cleaning of probes is necessary to ensure the success of the subsequent disinfection (205). One study demonstrated that vegetative bacteria inoculated on vaginal ultrasound probes decreased when the probes were cleaned with a towel (206). No information is available about either the level of contamination of such probes by potential viral pathogens such as HBV and HPV or their removal by cleaning (such as with a towel). Because these pathogens might be present in vaginal and rectal secretions and contaminate probes during use, high-level disinfection of the probes after such use is recommended.

References:

195. Fritz S, Hust MH, Ochs C, Gratwohl I, Staiger M, Braun B. Use of a latex cover sheath for transesophageal echocardiography (TEE) instead of regular disinfection of the echoscope? Clin. Cardiol. 1993;16:737-40.

196. Lawrentschuk N, Chamberlain M. Sterile disposable sheath sytsem for flexible cytoscopes. Urology 2005;66:1310-3.
197. Milki AA, Fisch JD. Vaginal ultrasound probe cover leakage: implications for patient care. Fertil. Steril. 1998;69:409-11.
198. Storment JM, Monga M, Blanco JD. Ineffectiveness of latex condoms in preventing contamination of the transvaginal ultrasound transducer head. South. Med. J. 1997;90:206-8.
199. Hignett M, Claman P. High rates of perforation are found in endovaginal ultrasound probe covers before and after oocyte retrieval for in vitro fertilization-embryo transfer. J. Assist. Reprod. Genet. 1995;12:606-9.
200. Amis S, Ruddy M, Kibbler CC, Economides DL, MacLean AB. Assessment of condoms as probe covers for transvaginal sonography. J. Clin. Ultrasound 2000;28:295-8.
201. Rooks VJ, Yancey MK, Elg SA, Brueske L. Comparison of probe sheaths for endovaginal sonography. Obstet. Gynecol. 1996;87:27-9.
202. Odwin CS, Fleischer AC, Kepple DM, Chiang DT. Probe covers and disinfectants for transvaginal transducers. J. Diagnostic Med. Sonography 1990;6:130-5.
203. Benson WG. Exposure to glutaraldehyde. J. Soc. Occup. Med. 1984;34:63-4.
204. Garland SM, de Crespigny L. Prevention of infection in obstetrical and gynaecological ultrasound practice. Aust. N. Z. J. Obstet Gynaecol. 1996;36:392-5.
205. Fowler C, McCracken D. US probes: risk of cross infection and ways to reduce it--comparison of cleaning methods. Radiology 1999;213:299-300.
206. Muradali D, Gold WL, Phillips A, Wilson S. Can ultrasound probes and coupling gel be a source of nosocomial infection in patients undergoing sonography? An in vivo and in vitro study. AJR. Am. J. Roentgenol. 1995;164:1521-4.