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INTRODUCTION: In January 2014 an internal audit was performed at the department of surgery, division of vascular surgery of the Medical University Graz, Austria, to assess the short and long-term outcomes of prosthetic shunt graft implantations performed between December 1998 and December 2013. A 10.8 % explantation rate due to graft infection was detected. The majority of the cases were associated with Staphylococcus aureus. The aim of this study was to clarify whether this constitutes a nosocomial problem. PATIENTS AND METHODS: Between December 1998 and December 2014 a total of 490 prosthetic shunt grafts were implanted. After exclusion of 54 cases, 436 shunts remained for statistical analysis. Genetic analysis (spa typing) was acquired from three new cases with involvement of S. aureus in 2014. The impact of several factors (e.g. sex, institute for dialysis, age, type of prosthesis, implantation surgeon and position of shunt) on the shunt graft infection rate was statistically analyzed. RESULTS: Of the prostheses 14.0 % (61 out of 436) had to be explanted of which 12.4 % (54/436) were due to infection. In 77.8 % (42/54) bacteria were found in blood and/or wound cultures. Staphylococcus aureus was present in 76.2 % (32/42) of the cases with detected bacteria and in all cases was sensitive to methicillin. The infection rate was not significantly dependent on any of the investigated factors; however, the factor "institute for dialysis" had a remarkable pvalue of 0.060 with the infection rate ranging from 8.5 % to 18.2 % depending on the institution. Three different S. aureus protein A (spa) types were found: t015, t359, t6265. The detection of three different spa types means that these patients had different sources of S. aureus so that a nosocomial problem is very unlikely. CONCLUSION: Genetic typing of spa is a suitable technique for distinguishing between nosocomial and community acquired sources of prosthetic shunt graft infections.
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OBJECTIVE: We evaluated the sensitivity and specificity of power Doppler sonography compared with conventional color Doppler sonography and gray-scale sonography in diagnosing patients with acute cholecystitis. SUBJECTS AND METHODS: Seventy-six patients with right upper quadrant pain and 72 healthy volunteers underwent gray-scale sonography, conventional color Doppler sonography, and power Doppler sonography of the gallbladder. The vascularity of the gallbladder wall was scored on a scale of 0 to +3. Histology revealed acute cholecystitis in 55 patients. Histologic specimens and clinical workups showed that the remaining 21 patients suffered from other diseases. RESULTS: Sensitive sonographic features such as the positive Murphy's sign (in 96% of patients with acute cholecystitis), calculi (95%), and a thickened gallbladder wall (73%) lacked specificity (71%, 38%, 67%, respectively) for diagnosing acute cholecystitis. In our study, the sensitivity of power Doppler sonography was 95% compared with 33% for color Doppler sonography in revealing a hypervascularized gallbladder wall. Power Doppler sonography revealed hyperemia within a nonthickened gallbladder wall in four patients with surgically proven acute cholecystitis. Specificity of power Doppler sonography was 86% compared with 95% for conventional color Doppler sonography. False-positive results with power Doppler sonography were caused by pancreatitis, duodenal ulcer, and gallbladder carcinoma. Interobserver variability seemed to play no significant role. No intramural hypervascularity was detected in the volunteer group. In four (4%) of 89 symptomatic patients we could not use power Doppler sonography because of the patients noncompliance. Mean values of the resistive index assessed within intramural vessels of the gallbladder showed no significant differences (p < .001) between patients with acute cholecystitis (0.73) and patients with other diseases (0.71). CONCLUSIONS: Although the sensitivity of power Doppler sonography in diagnosing acute cholecystitis was similar to that of gray-scale sonography, the specificity of power Doppler sonography was significantly higher, which may substantially improve diagnostic confidence. However, the high susceptibility of power Doppler sonography to motion artifacts makes appropriate adjustment of technical parameters much more relevant than with other sonographic imaging. The resistive index within intramural vessels has no clinical use in the diagnosis of acute cholecystitis.
