Monday, February 20, 2012

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.

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.

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.


  1. Hello,
    I have been researching this topic recently, because I believe I was infected with HPV at my gyn clinic after having a transvaginal ultrasound done. This small clinic performs a lot of ultrasounds on patients back to back. I know for a fact that there was no probe cover or condom used, and unsure of "wiping with a towel" was safe.
    What can I do? Or who can I contact to report this issue? Any information would be helpful. Thanks

  2. This just happened to my niece yesterday, and we came across this site. We don't know at this point whether she was infected with anything, but while she was waiting she searched the drawers in the room and found only the gel--no disinfectant or probe covers. I recommended that she report to the state or county health departments in her area.

  3. I am an ultrasound tech and perform transvaginal ultrasounds everyday. The reason you may not see the disinfectant/probe covers in the exam room is because some states require that it be located out of a patient care area--we use a high level disinfectant that can be caustic if it comes in contact with the skin--so we disinfect our probes in separate areas to ensure patient safety. We also store the probe covers in this area and bring them in the room with us. A potential reason that the clinic schedules patients back to back with no time between patients to properly disinfect a probe is typically that they have more than one probe. Usually one probe is soaking in the disinfection chamber while the other is being used. This process takes anywhere from 7-20 minutes. But as a health care professional, I always wonder if patients ever question how this process is completed since it is not readily visible--and believe me--the health care standards are so very stringent on both a state and federal level--just because you cant see it doesnt mean it isnt being practiced--most organizations are checked every 18-39 months by the governing bodies (Joint Commission and a state inspector). They also have to report any incidence of potential post procedural infection--they would have been shut down if they did not comply with the process or if their numbers indicated they may be the source of the infection. It may help to just call and ask to speak to the techologist--I would completely understand if my patient had questions about the process, it is a very important issue for many women!

  4. The issue here is HPV frankly. It's very stubborn and recent studies in the ED show that something like 1 in 10 probes have HPV on them (akin to a recent study that found that 3 in 20 colonoscopies had patient sludge on them after sterilization). And several strains are HR-HPV to boot. It's not clear the loads are enough to cause infection but it also isn't clear it is not.

    I take no comfort in the technologist's reassurance above. With patient ignorance, the lack of visibility and the temptation to cut a sterilization sessions short, all the incentives would be to do a poor job (as in the case of Emergency Departments). I'll add that it would be near impossible as a practical matter to link HPV infection back to bad practices at a particular clinic. HPV infections usually are cleared and the infection to dangerous dysplasia pathway can take decades.

    The truth is that OB GYN has been a rich source of cross-contamination for decades (see metal speculum sterilization). Of course, that's just more business right?