Gastric Contrast Ultrasound in Tumour Assessment

Gastric contrast ultrasonography is gaining attention as an imaging approach for evaluating gastric tumours, including gastric cancer. The method includes oral contrast ultrasonography, which uses an oral agent to improve visualisation of the gastric wall, and double contrast-enhanced ultrasonography, which combines oral and intravenous contrast to assess both structure and perfusion. These techniques address limitations of conventional ultrasound, where gas, food residue and peristalsis can obscure lesions. Compared with gastroscopy, endoscopic ultrasonography and CT, gastric contrast ultrasonography offers a non-invasive, radiation-free and real-time option with lower cost. Its use spans screening, diagnosis, staging and treatment assessment. Clinical uptake remains limited by operator dependence, lack of standardisation and variability across patient groups. Current evidence supports its role as a complementary imaging modality rather than a replacement for established techniques.

Screening and Diagnostic Performance

Oral contrast ultrasonography enhances gastric imaging by filling the stomach with an echogenic agent that reduces interference from gas and residue. This enables clearer visualisation of the gastric wall and its layered structure, as well as the relationship between lesions and adjacent tissues. Double contrast-enhanced ultrasonography extends this by adding intravenous contrast, allowing assessment of vascular patterns and perfusion.

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Evidence shows that oral contrast ultrasonography performs well in screening and lesion detection. A large screening programme reported high specificity and negative predictive value, and a multicentre analysis involving 383,945 patients found no significant difference compared with gastroscopy across sensitivity, specificity and overall accuracy. Detection is higher for lesions presenting as hypoechoic wall thickening but lower for gastric polyps. Performance is influenced by body habitus and acoustic window quality, with better results in non-obese patients.

The technique is suited to screening and pre-endoscopic triage in settings with limited endoscopic capacity, as well as in patients unwilling or unfit for gastroscopy. Gastric wall thickness provides additional value in risk stratification, with increasing thickness associated with higher malignancy risk. An artificial intelligence model based on U-net achieved high accuracy in gastric layer segmentation and lesion classification, supporting further integration of automated analysis.

Staging and Pathological Characterisation

Preoperative staging represents a key application. For T staging, oral contrast ultrasonography enables assessment of tumour invasion into submucosal and muscular layers, while CT remains more effective for evaluating serosal and perigastric involvement. Accuracy varies by stage, with higher performance reported for advanced stages compared with early disease. Combined imaging with CT improves overall staging accuracy compared with either modality alone.

Double contrast-enhanced ultrasonography enhances tumour localisation and margin delineation while providing information on enhancement patterns. Arterial hyper-enhancement and rapid venous washout support staging assessment. It shows improved accuracy over oral contrast ultrasonography in intermediate and advanced stages, while both techniques perform similarly in distinguishing early from more advanced disease. Endoscopic ultrasonography performs better in early-stage assessment, whereas double contrast-enhanced ultrasonography is more accurate in advanced stages. Compared with enhanced CT, double contrast-enhanced ultrasonography shows stronger performance in early disease, while CT remains superior in later stages.

In nodal staging, evidence remains limited. Oral contrast ultrasonography achieves accuracy comparable to CT in some cases, and combining both modalities improves performance. Double contrast-enhanced ultrasonography demonstrates higher sensitivity for lymph node metastasis but lower specificity. In pathological classification, double contrast-enhanced ultrasonography achieves high accuracy and reproducibility in Borrmann classification and shows different enhancement patterns across histological subtypes, including diffuse and undifferentiated disease.

Broader Applications and Current Limits

Applications extend beyond gastric cancer to gastrointestinal stromal tumours and gastric lymphoma. In gastrointestinal stromal tumours, oral contrast ultrasonography identifies tumour origin, shape and boundary characteristics, while double contrast-enhanced ultrasonography adds perfusion assessment. Parameters such as tumour size, arrival time and peak intensity support preoperative risk classification, with high-risk lesions showing faster enhancement and greater intensity.

In gastric lymphoma, imaging characteristics differ between subtypes, and agreement with CT is strong in treatment monitoring. However, oral contrast ultrasonography may require longer intervals to confirm remission due to difficulty distinguishing residual disease from fibrotic changes. Following intravenous contrast, lymphoma typically shows heterogeneous hyper-enhancement with delayed washout, although supporting evidence remains limited.

Several limitations affect wider adoption. Diagnostic performance depends on operator expertise. Oral contrast reduces but does not eliminate artefacts from gas. Gastric peristalsis can affect staging accuracy, particularly in early disease. After neoadjuvant therapy, persistent wall thickening due to fibrosis or inflammation can reduce accuracy. Future development areas include standardised protocols, expanded clinical validation, improved contrast agents, AI-assisted analysis and tele-ultrasound support.

Gastric contrast ultrasonography offers a non-invasive and accessible approach to evaluating gastric tumours across screening, diagnosis and staging. Oral contrast and double contrast-enhanced techniques provide complementary structural and perfusion information and extend imaging capabilities beyond conventional ultrasound. Their role remains supplementary to established modalities such as gastroscopy, endoscopic ultrasonography and CT. Wider adoption will depend on improved standardisation, stronger clinical evidence, enhanced training and continued technological development, particularly in artificial intelligence and image acquisition.

Source: Insights into Imaging

Image Credit: iStock