Intra-abdominal fat. Part II: Non-cancerous lesions of the adipose tissue localized beyond organs

Adipose tissue does not belong to the most favorite structures to be visualized by ultrasound. It is not, however, free from various pathologies. The aim of this paper is to make abdominal cavity examiners more familiar with non-cancerous lesions found in intra-abdominal fat. The main focus is lesions that are rarely discussed in the literature. Visceral adiposity is one of important pathogenetic factors contributing to cardiovascular events, metabolic syndrome and even certain neoplasms. That is why this article exposes sonographic features that are the most characteristic of these lesions. The value of ultrasonography in the diagnosis of this pathology is underestimated, and a number of US scan reports do not reflect its presence in any way. Moreover, the article discusses more and more common mesenteritis, the lack of knowledge of which could pose difficulties in explaining the nature of symptoms reported by patients. Furthermore, this review presents lesions referred to in the literature as focal infarction of intra-abdominal fat. This section focuses on infarction of the greater and lesser omentum, epiploic appendagitis, mesenteric volvulus and focal fat necrosis resulting from pancreatitis. These lesions should be assessed with respect to the clinical context, and appropriate techniques of ultrasonography should be employed to allow careful determination of the size, shape, acoustic nature and location of lesions in relation to the integuments and large bowel, as well as their reaction to compression with an ultrasound transducer and behavior during deep inspiration. Moreover, each lesion must be obligatorily assessed in terms of blood flow. Doppler evaluation enables the differentiation between primary and secondary inflammation of intra-abdominal fat. The paper also draws attention to a frequent indirect sign of a pathological process, i.e. thickening and hyperechogenicity of fat, which sometimes indicates an ongoing pathology at a deeper site. This structure may completely conceal the primary lesion rendering it inaccessible for ultrasound. In such cases and in the event of other doubts, computed tomography should be the next diagnostic step.