Alec McGinley, MD | PGY1
Article
Walsh Thomas, W., Douglas, J. E., & Rassekh, C. H. (2017). Accuracy of Ultrasonography and Computed Tomography in the Evaluation of Patients Undergoing Sialendoscopy for Sialolithiasis. Otolaryngology–Head and Neck Surgery, 156(5), 834–839.
Background
This study looked to compare the use of CT and US for identification of salivary gland stones or sialolithiasis. Sialoendoscopy is the technique used for direct identification and when indicated extraction of salivary gland stones. CT is used to identify stones and plan for removal but is relatively expensive and comes with the risks of radiation exposure. US has been used to identify stones and has the added benefit of being less expensive and caries no radiation risk, however the scans and their ability to provide useful information are known to be user dependent.
The Study
This was a retrospective cohort study of all patients undergoing sialoendoscopy for suspected sialolithiasis at a single center, by a single provider over a 2.5 year period. Patients were excluded if there procedure was the result of chronic Sjogren’s, radioactive iodine, or oncologic resection. Patients were referred to the center and obtained a combination of CT and/or US imaging at both the study site and outside hospitals. Sialoendscopic identification of stones was considered the ‘gold standard’ in this study.
Results
In total 68 patients were included in the final sample, 17 patients with parotid gland stones and 51 patients with submandibular gland stones. 63 were ultimately identified to have stones on sialonedoscopy. 20 patients had CT only, 4 had US only and 44 obtained both imaging modalities. CT was found to be more sensitive (95% vs 65%), more specific (88% vs 80%) and to have a higher negative predictive value (88% vs 21%). However, the two modalities were found to have comparable positive predictive values (98% for CT vs 96% for US).
Takeaway
Although CT was found to be more sensitive and specific, the high PPV for US indicates the potential for avoiding unnecessary radiation exposure in patients with suspected sialolithiasis. The authors speak to the idea that the two studies can be complementary in identifying stones and planning for intervention. In addition, the potential for use of US in the hands of trained ENT providers as an adjunct to their physical exams could increase the sensitivity and specificity of US and in the future lead to elimination of the need for CT in certain patients.