Results of ultrasound-assisted diagnosis of tunnel infections in continuous ambulatory peritoneal dialysis.

The management of catheter-related infections has become a major challenge in continuous ambulatory peritoneal dialysis treatment. Early recognition and discrimination of mere exit site infections from more invasive and catheter menacing tunnel infections (TIs) are of therapeutic importance. As the diagnosis of TI is still based on clinical signs and only indicates advanced infections, we studied the usefulness of the ultrasound examination (UE) of the continuous ambulatory peritoneal dialysis catheter. Examinations were made by a mobile ultrasound unit using a 7.5 MHz transducer. Sixty-two continuous ambulatory peritoneal dialysis patients with an Oreopoulos Zellermann catheter (Oreopoulos-Zellerman Cathete-THWII, Baxter GmbH, Unterschleissheim, Germany) were studied repeatedly between February 1991 and July 1992. Pericatheter fluid collection (with typical sonographic localization) was consistent with surgical findings and histopathologic examination and proved to be a reliable criterion of TIs. The incidence of TIs was significantly higher when using UE (0.35/patient-year) compared with the usual clinical criteria (0.12/patient-year, P < 0.01). Staphylococcus aureus exit site infections were predominant and had the highest risk of concomitant TIs (83%). Eleven of 25 patients with a positive UE lost their catheter due to infectious complications, while no patient with a negative UE underwent operation for infectious reasons (P < 0.01). The peritonitis rate (0.64/patient-year) was markedly increased when UE indicated a TI (1.7/patient-year, P < 0.01). We conclude that sonography is a sensitive tool for the early diagnosis of unsuspected TIs. Sonography is a bedside method used for screening purposes and allows us to control the treatment regimen.