Variability in measurements of pancreatic cyst size among EUS, CT, and magnetic resonance imaging modalities

Background: Cyst size is an important factor in the management of pancreatic cysts, both in predicting the need for surgery and the frequency of follow-up. Objective: To determine agreement and precision of EUS, CT, and magnetic resonance imaging (MRI) modalities in the evaluation of pancreatic cyst diameter. Design: Retrospective chart review. Setting: Tertiary-care center, January 2000 to June 2009. Patients: This study involved 175 patients presenting for EUS evaluation of pancreatic cysts, with size measured by at least two of the aforementioned imaging studies within a 90-day period. Main Outcome Measurements: Largest cyst diameter from EUS, CT, MRI/MRCP, and surgical pathology. Results: A total of 175 patients underwent EUS. Seventy-three had CT plus EUS, 33 had MRI/MRCP plus EUS, 23 had MRI/MRCP plus CT, and 15 had all imaging studies, occurring within 90 days of each other. Median size differences between studies: EUS and CT (ie, absolute value of size determined by EUS minus size determined by CT) = 4 mm (range 0-25 mm), EUS and MRI = 4 mm (range 0-17 mm), CT and MRI = 3 mm (range 2-20 mm). Median size differences for surgical pathology specimens compared with results of 12 EUS, 13 CT, and 8 MRI/MRCP studies were as follows: EUS and pathology = 9.5 mm (range 0-20 mm), CT and pathology = 5 mm (range 0-21 mm), MRI and pathology = 5.5 mm (range 2-44 mm). Limitations: Interobserver variability and small sample of surgical pathology cysts. Conclusion: There is considerable variation in size estimates of pancreatic cysts by different imaging modalities, which practitioners should take into account when making management decisions. Use of a single imaging modality is recommended during follow-up. The precision of imaging studies for measuring pancreatic cysts must be prospectively defined if change in size is to be reliably used for clinical management.