Acute cholecystitis in an animal model: findings on color Doppler sonography.

OBJECTIVE: The purpose of our study was to evaluate the color Doppler findings of acute cholecystitis in a controlled canine model. MATERIALS AND METHODS: Fourteen animals had a laparotomy: cystic duct ligation was done in eight, and incision with closure was performed in six control subjects. Animals were scanned in a blinded fashion preoperatively, immediately postoperatively, and on postoperative days 1-5. On postoperative day 5, a hepatobiliary scan was done with 2 mCi (74 MBq) 99mTc-mebrofenin. Blinded histopathology was performed and correlated with imaging. RESULTS: Flow was seen in the wall of each gallbladder at some point during the postoperative course, demonstrating vascular patency. Hepatobiliary scintigraphy confirmed cystic duct status in 12 cases; two animals died before radionuclide imaging was complete. Color Doppler signal decreased in the gallbladder wall in ligated dogs from postoperative day 1 to postoperative day 3 (p = .03 versus controls at postoperative day 2) and increasingly returned by postoperative day 5. Hyperemia was seen in only two cases (both with severe necrotizing cholecystitis) and only at postoperative day 5. Although not statistically significant, a weak trend of increasing flow with more severe pathologic grades of cholecystitis was observed (p = .20). CONCLUSIONS: In this animal model, loss of vascular signal (not hyperemia) at postoperative day 2 was the finding to diagnose early acute cholecystitis, although lack of flow can also be seen in some normal subjects. Flow tended to return by postoperative day 5, and it increased in some of the more severe cases of cholecystitis. Hyperemia was a somewhat useful sign of acute necrotizing cholecystitis.

Lesion visualization by targeted computed tomography liver enhancement in dogs.

RATIONALE AND OBJECTIVES: We conducted a pilot study to determine the potential advantages of using liver-specific targeted computed tomography (CT) contrast agents for lesion detection. METHODS: Eight dogs had liver infarcts created by percutaneous injections of ethanol. Each dog underwent CT scans with four imaging techniques: unenhanced, intravenous contrast enhanced (IVCE), CT arterial portography (CTAP), and targeted liver enhancement with iodipamide ethylester (IDE) particles. Lesions were assessed quantitatively to determine liver-to-lesion density differences and the drop in density across liver edge as a quantitative measure of edge sharpness. Expert readers subjectively analyzed data to determine lesion visibility and edge sharpness. RESULTS: Liver-to-lesion density differences were greatest with CTAP (56.4 +/- 35.5 Hounsfield units [H]) followed by IDE (41.1 +/- 7.0 H), i.v. (22.7 +/- 6.0 H), and unenhanced scans (13.6 +/- 4.1 H; ps < .05 for CTAP versus unenhanced and IDE versus unenhanced). Edges were best defined both subjectively and quantitatively on IDE-enhanced scans. CONCLUSION: Targeted liver-specific contrast agents have potential to increase lesion visibility when compared with standard i.v. contrast enhancement of the liver by increasing lesion edge definition and liver-to-lesion attenuation differences. Further work in animal tumor models, and clinical trials as agents become available, appears justified.