Ultrasound gel and infection risk: why sterile gel matters in ultrasound-guided procedures
Ultrasound gel looks like the most harmless item in a clinic. In a diagnostic scan on healthy skin, it is. But when ultrasound stops being just a way of looking and starts guiding a needle or an injection, that gel changes role: if it is not sterile, it can be the door through which bacteria enter the puncture site. The difference between gel for scanning and gel for needling looks small and is large in its consequences.
Looking is not the same as needling
Running the probe over healthy skin to look at a tendon or a joint carries no risk: the gel simply acts as a bridge for the ultrasound. Things change when that same scan guides a needle. In an injection or needle procedure, the needle passes through the skin and can drag along whatever sits on its surface. If the gel is not sterile, it stops being a mere contact medium and becomes a possible vehicle carrying bacteria inside. That is why gel for scanning and gel for a procedure need to be told apart.
A documented problem, not a theoretical one
An outbreak of 119 infections from non-sterile gel
The CDC investigated 119 invasive Burkholderia stabilis infections across 10 states. The source was a non-sterile, multi-use ultrasound gel: cultures of still-unopened product tested positive, and genome sequencing confirmed that the strain in the gel was the same as the strain in the patients.
The contamination came from the factory, not from the clinics, and ended in a nationwide recall of every gel from that manufacturer. The investigation found a pattern: non-sterile gel was being used to "look" before or during percutaneous procedures and, if it is not fully removed from the skin, it drags living bacteria into the puncture site.
Hudson MJ, Park SC, Mathers A, et al. Outbreak of Burkholderia stabilis infections associated with contaminated nonsterile, multiuse ultrasound gel - 10 States, May-September 2021. MMWR Morb Mortal Wkly Rep. 2022;71(48):1517-1521. doi:10.15585/mmwr.mm7148a3
Not an isolated case: 14 outbreaks in three decades
A systematic review gathered 14 outbreaks published between 1991 and 2021 linked to ultrasound gel. Bacteraemia was the most frequent presentation, and in most cases the contamination was intrinsic, from the gel container itself.
That the gel can arrive contaminated at source, rather than through a one-off lapse in the clinic, is the finding that most strongly compels the use of sterile single-use product whenever a needle will follow. The bacterium involved almost always belongs to the Burkholderia cepacia complex, a microorganism that survives well in watery environments.
Angrup A, Kanaujia R, Biswal M, Ray P. Systematic review of ultrasound gel associated Burkholderia cepacia complex outbreaks: clinical presentation, sources and control of outbreak. Am J Infect Control. 2022;50(11):1253-1257. doi:10.1016/j.ajic.2022.02.005
How the bacteria get in
The same bacterium, in the gel and in the blood
In an intensive care unit, 14 patients developed Burkholderia cepacia bacteraemia. Molecular typing showed a 95% match between the bacteria in the blood and those in the gel used to guide catheter placement.
The mechanism is simple: Burkholderia thrives in watery media such as gel, persists and multiplies, and it only takes gel not being fully removed before the puncture for it to be dragged inside. That is why the risk lies not in scanning with ultrasound, but in passing a needle through gel that should never have been at the puncture site.
Abdelfattah R, Al-Jumaah S, Al-Qahtani A, Al-Thawadi S, Barron I, Al-Mofada S. Outbreak of Burkholderia cepacia bacteraemia in a tertiary care centre due to contaminated ultrasound probe gel. J Hosp Infect. 2018;98(3):289-294. doi:10.1016/j.jhin.2017.09.010
What happens in musculoskeletal injections
In ultrasound-guided injections, protocols vary widely
A review gathered 105 clinical trials of ultrasound-guided musculoskeletal injections: half did not describe how the skin was disinfected, and nearly two thirds gave no detail on probe preparation. Serious adverse events were very infrequent.
This should not be overstated: infection after an ultrasound-guided injection is uncommon. But the huge variability in protocols, and how sparsely they are documented even in published studies, is exactly why this technique cannot be improvised and deserves a careful routine in every case.
Alito A, de Sire A, Di Gesù M, et al. Impact of adequate disinfection techniques for ultrasound-guided injections in musculoskeletal rehabilitation: a scoping review. Diagnostics (Basel). 2025;15(7):933. doi:10.3390/diagnostics15070933
The standard of good practice
The guidelines agree: probe sheath and sterile gel
A review of 13 international guidelines found that, although they rest more on infection control principles than on high-quality trials, they all recommend the same thing for percutaneous procedures: a probe sheath and sterile gel.
The exact level of probe disinfection varies from one guideline to another, but the point of consensus is not in question: when ultrasound guides a needle, the gel is sterile and the probe is covered. It is a recommendation grounded in infection control common sense rather than large trials, which is to be expected for an infrequent event.
Peters N, Williamson F, Eley V. Ultrasound transducer disinfection for percutaneous procedures: a review of the evidence supporting guideline recommendations. Australas J Ultrasound Med. 2024;27(4):242-250. doi:10.1002/ajum.12408
The failure usually lies in practice, not in the rules
An audit across 16 emergency departments measured overall compliance with disinfection rules at 66% (95% CI 62.8 to 69.1), with aseptic technique lapses and misuse of gel among the most frequent errors.
The difference between a safe injection and an avoidably risky one lies in details the patient never gets to see. Having a standard is not enough: it has to be applied, step by step, in every procedure. That is where a disciplined technique makes the difference.
Andolfo A, Maatoug R, Peiffer-Smadja N, Fayolle C, Blanckaert K. Emergency ward ultrasound: clinical audit on disinfection practices during routine and sterile examinations. Antimicrob Resist Infect Control. 2021;10(1):25. doi:10.1186/s13756-021-00896-w
Take-home
- For diagnostic ultrasound on healthy skin, ordinary gel poses no problem.
- For any ultrasound-guided injection or needle procedure, the gel must be sterile and single-use: it is the route by which bacteria can get in.
- The documented outbreaks, including one of 119 cases investigated by the CDC, almost always trace back to non-sterile multi-use gel, often contaminated at the factory.
- Infection after a musculoskeletal injection is uncommon, but preventable: it depends on sterile single-dose gel, a probe sheath and aseptic technique.
- The guidelines agree on the standard; when something fails, it is rarely from not knowing it, but from not applying it.
At Avanza Salud we work with sterile technique
In podiatry and physiotherapy we perform ultrasound-guided procedures to the standard the evidence supports: sterile single-use gel, disinfection of the probe and the skin, single-use consumables and aseptic technique from start to finish. Ultrasound used properly makes an injection more accurate and safer, not the other way round. If you are considering an ultrasound-guided procedure, whether in podiatry (for example a hyaluronic acid injection in the foot or ankle) or in physiotherapy (percutaneous needle electrolysis (EPI) and percutaneous neuromodulation of the musculoskeletal system), we will gladly explain, with no obligation, how we perform it and why we take care over every one of these steps.