Ultrasound in the Diagnosis of Malignant Pelvic Fistulas: Sonographic Findings in Correlation with Computed Tomography Imaging

Abstract

Even though ultrasound is an extensively used imaging modality, it has not been effectively utilized in the evaluation and diagnosis of malignant pelvic fistulas. In this study, we tried to correlate the accuracy of sonographic findings in identifying malignant fistulas with that of computed tomography (CT) imaging. Thirty-five patients with advanced pelvic malignancies were examined over a period of 2 y. Patients underwent CT of the abdomen and pelvis with intravenous and oral/rectal contrast followed by ultrasound of the abdomen. Sonographic examinations were performed using a standardized protocol with a full bladder. Real-time ultrasound images of the abdomen and pelvis in multiple planes were acquired and stored as both image files and audio-video interleaves (AVIs). On ultrasound, the majority of the fistulas were visualized either as a continuous hyper-echoic tract within a hypo-echoic neoplastic mass (“air contrast sign”) or as multiple discontinuous hyper-echoic foci with “ring down” artifacts. The sensitivity and specificity of ultrasound in the detection of malignant fistulas were 72% (confidence interval [CI]: 52%–87%) and 66% (CI: 22%–95%), respectively. We also reviewed the literature and compared the sensitivities of ultrasound in the detection of various types of pelvic fistulas obtained in previous studies with those in the present study. Results suggest that although ultrasound cannot be used as a primary imaging modality for the detection of fistulas, it can provide the earliest clue to the presence of a malignant fistula.