Vai trò của X-quang cắt lớp vi tính trong chẩn đoán tụ dịch ổ bụng sau mổ

Roles of computed tomography in diagnosis of postoperative abdominal fluid collections

SUMMARY

Objectives: The purpose of this study was to determine whether the separate computed tomographic imaging features or their combination with clinical and laboratory parameters could distinguish infected from noninfected abdominal fluid collections after surgery.

Materials and Methods: The cross-sectional descriptive study included 68 consecutive patients who underwent portal venous phase CT on 64 and 128 multidetector CT at the University Medical Center HCMC from 01/2014 to 03/2017. Imaging findings included attenuation (Hounsfield unit – HU), entrapped gas, wall enhancement and thickness, fat stranding, and volume of fluid collections. Clinical and laboratory parameters included diabetes and C-reactive protein. The standard of reference for the presence of infection was microbiological Gram stain and culture of fluid samples. A scoring system from 1 to 10 included diabetes: 2 points; CRP ≥ 100mg/L: 1 points; attenuation of fluid collections ≥ 20HU: 4 points; entrapped gas: 3 points.

Results: CT imaging features (attenuation of fluid collections, entrapped gas) was significantly associated with the presence of infection. Sensitivities of these features varied between 56.5-87%, specificities between 68.2-81.8%, LR(+) 2.74-3.1, LR(-) 0.19-0.53. Multiple logistic regression analysis revealed attenuation of fluid collections and entrapped gas as significant independent predictors of infection (p<0.01), consecutive OR were 166.1 (95% confedence interval [CI], 7.52-3670) and 14.77 (95% CI, 1.44- 392.78). Based on using the CT-clinical-laboratory scoring system, scores of 3 or lower had a 100% negative predictive value, scores of 6 or higher had an 86,8% positive predictive value and scores of 7 or higher had a 96,7% positive predictive value for diagnosing infected fluid collections. Receiver operating characteristic analysis revealed an area under the curve of 0.86 (95% CI, 0.77- 0.94) for the score.

Conclusion: Based on computed tomographic imaging features alone for distinguishing infected from noninfected abdominal fluid collections is still limited. CT had a low capability to confirm and could not be used to rule out the presence of infection. The application of the CT-clinical-laboratory scoring system may improve the ability to predict infected fluid collections after abdominal surgery.

Key Words: postoperative, abdominal cavity, fluid collections, abscess, computed tomography (CT).