PURPOSE

Systemic to pulmonary vasculature shunting (SPS) is an important finding to identify the probable site of bleeding, especially in multicentric parenchymal lung disease. The purpose of this study was to evaluate the value of imaging findings, which can locate SPS on dual-energy computed tomography angiography (DECTA), and correlate with digital subtraction angiography (DSA), which was considered as a gold standard.

METHODS

Retrospective analysis of 187 patients (148 males, 39 females, mean age: 43.7 ± 15.1 years) between October 2014 and November 2018 who underwent both DECTA and DSA. Computed tomography angiography was performed using dual-source (80 and 140kV), 2 × 128 slice equipment, using 50-80mL iodinated contrast (400mg iodine/mL). These patients were divided into shunting (group A) and non-shunting groups (group B), based on the presence or absence of signs of shunting on DECTA. Group A had 98 and group B had 89 patients. We analyzed the following imaging signs for identifying SPS: (1) non-tapering pulmonary artery sign, (2) clustering of vessels sign, and (3) significant differential attenuation sign (>25 HU difference in attenuation between segmental pulmonary arteries of shunting side and normal non-shunting side was considered significant). The correlation was done with DSA to identify the presence of SPS.

RESULTS

In 187 patients, 281 lobes were evaluated to look for the signs of shunting from systemic artery to pulmonary vessels on DECTA. A total of 98 patients who showed signs of shunting on DECTA presented 135 lobes with parenchymal, with or without pleural, abnormalities. Of these, 84 patients had one or more aspergilloma in the lobe where shunting was seen. In one patient, a specific artery could not be cannulated due to a tortuous course; hence, all arteries which were seen on CTA causing shunting were also seen on DSA. Non-tapering pulmonary artery segmental branches were seen in 97 (99%) patients, clustering of systemic vessels was seen in 90 (91.8%) patients, and significant attenuation difference was seen in 74 (75.5%) patients. In the rest of the 89 patients, 146 lobes were assessed but no signs of shunting were seen on DECTA. Nine arteries in 8 patients showed shunting on DSA, while the rest did not show any shunting. Digital subtraction angiography correlation showed 96.4%, 100%, 100%, and 93.8% of sensitivity, specificity, positive predictive value, and negative predictive value, respectively, for DECTA in detecting SPS on a per artery basis.

CONCLUSION

The proposed signs on DECTA help in identifying the systemic vessels that cause shunting, and hence, the most likely bleeding site, which aids in planning the endovascular management by targeting specific arteries in case of multicentric disease. Being the gold standard, DSA is an ideal modality for detecting very small SPSs and in classifying the latter.