Isolated Reticular Infiltrations of the Mesentery and Omentum

Isolated reticular infiltrations of the mesentery and omentum (i.e., those without irregular and nodular thickening) can be challenging on imaging, as it may be impossible to differentiate among the possibilities:

• Inflammation:
• Infection: For example, tuberculosis
• Maliganncy: Lymphoma, mesothelioma, metastases.

Percutaneous biopsy is often requested to guide treatment decisions. However, these types of lesions also present a challenge at biopsy, because they tend to be softer and even more mobile than nodular mesenteric or omental lesions.

Lee and colleagues recently looked at the performance of ultrasound-guided percutaneous biopsy in 45 patients with isolated reticular infiltrations of the mesentery and omentum.

Almost all biopsies were technically successful, with adequate specimens obtained from all but one of their patients. Two patients who were diagnosed with nonspecific inflammation at biopsy went on to be diagnosed with malignancies at surgery (colon and pancreatic carcinoma).

Overall, the diagnostic accuracy of imaging-guided percutaneous biopsy is in the range of 84%-92% (including data from an earlier study by Pombo and colleagues). The sensitivity and specificity for detecting malignancy are 89% and 100%, respectively. The sensitivity and specificity for detecting tuberculosis were 75% and 100%, respectively (the study was performed in Korea). The sensitivity and specificity for detecting nonspecific inflammation were 90% and 83%, respectively.

The image above is from a patient with cirrhosis and ascites who was found to have reticular areas of increased attenuation in the omental fat. Concern for omental caking and mesothelioma was raised at an outside facility. Percutaneous biopsy of the omentum showed chronic inflammation and focal mesothelial hyperplasia without evidence of malignancy.

References

• Lee JK, Baek SY, Lim SM, Lee KH. Reticular Infiltrations Alone without Mass in the Mesentery and Omentum Identified at Contrast-enhanced CT: Efficacy of US-guided Percutaneous Core Biopsy. Radiology. 2011 Oct;261(1):311-7. Epub 2011 Aug 24.
• Pombo F, Rodriguez E, Martin R, Lago M. CT-guided core-needle biopsy in omental pathology. Acta Radiol. 1997 Nov;38(6):978-81.