AJR: Ultrasound-guided procedures pose low infection risk

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The incidence of infectious complications after common ultrasound-guided procedures is low, according to a study published in the October edition of American Journal of Roentgenology (AJR).

Ultrasound provides dynamic views in multiple planes and lacks ionizing radiation, making it safe, effective and accurate for interventional procedure guidance, shared John M. Knudsen, MD and lead author, of the department of radiology at Mayo Clinic, in Rochester, Minn. However, data regarding the incidence of infection after ultrasound-guided procedures are lacking.

Knudsen and colleagues sought to investigate the incidence of infection after common ultrasound-guided procedures, including fine-needle aspiration (FNA), drain placement, biopsy, pseudoaneurysm injection, thoracentesis and paracentesis.

The researchers conducted a descriptive review of infections prospectively identified by Mayo Clinic’s infection prevention and control committee (IPAC) and department of radiology to determine the incidence of infectious complications.

Mayo Clinic performed 13,534 percutaneous ultrasound-guided procedures in 8,419 patients from Jan. 1, 2006 to Dec. 31, 2007. Patient ages ranged from 2 months to 99 years (mean age, 57 years), and the population included 4,300 females and 4,119 males.

Knudsen and colleagues used IPAC surveillance data and radiology department reports to identify positive cases of infection. To ensure causality the authors attributed bloodstream infections to the ultrasound procedure if the procedure was performed within 24 hours of the positive culture. They also accessed radiology follow-up chart reviews and surveys at 24 hours, three months and 12 months post-procedure to classify infections.

The researchers grouped infections into two categories: likely related to the procedure or possibly related to the procedure. While likely cases were “unambiguous and almost certainly related … to the procedure,” possible cases were “too far removed … to ensure causality, cultures were not available or infection was less likely related to the procedure when the clinical history was considered,” explained Knudsen. Researchers included possible cases in the study to obtain the most conservative estimate of infectious complications.

Among the 13,534 ultrasound-guided procedures, researchers found 11 likely and three possible procedure-related infections, for an overall incidence of 0.1 percent.  Likely infections included four abscesses, three cases of bacteremia and four cases of peritonitis. Possible infections included one abscess, one bloodstream infection and one urinary tract infection.

“The highest incidence of infections occurred after ultrasound-guided biopsy (0.2 percent, 10/5,487), with biopsy of a hepatic transplant having the highest incidence of infection (1 percent, 2/192),” wrote Knudsen. No infections occurred after thoracentesis and FNA.

Nearly every patient improved on antibiotics alone, reported Knudsen. Although one patient died five days after infection, the cause of death was likely related to the patient’s severe clinical condition.

Knudsen and colleagues acknowledged that the prospective surveillance method may have missed minor infections such as cellulitis. However, they believe their method, which used both IPAC surveillance and radiology data, was “robust” and captured most serious infections.

The incidence of a serious infection after ultrasound-guided intervention is low, concluded Knudsen. “Radiologists can use these data to provide more accurate information to patients when asking for consent before procedures and to reassure their patients,” he added.