Water gives boost to gastrointestinal multislice CT imaging

Filling the stomach with water before a multislice CT scan enhances the preoperative characterization and staging of gastric cancer, according to studies from Asia and Europe.

Hollow gastrointestinal structures require distention for proper assessment, and radiologists and other specialists routinely use gas for a number of GI exams. Several studies presented at the 2005 European Congress of Radiology tried using water as an inexpensive and safe means to achieve GI distention. The water-filled MSCT method isn't common yet, but researchers anticipate it may become a widespread practice for GI imaging studies.

"The water-filling technique is likely to be a standard for staging of esophageal and gastric cancer soon, because CT is used anyway, and the water and gas are almost free," said Dr. Wolfgang Schima, an associate professor of radiology at the Medical University of Vienna.

Schima and colleagues from radiology institutions in Austria and the Netherlands prospectively enrolled 57 patients who underwent MSCT and endoscopic ultrasound for the preoperative staging of gastric cancer. They distended the patients' stomachs using 1 L to 1.5 L of water previous to each imaging exam and correlated each modality's results against biopsy.

The "hydro-enhanced" MSCT provided better overall preoperative visualization and staging than did ultrasound, especially in cases of advanced gastric cancer.

Accuracy for staging primary tumors with hydro-enhanced MSCT was 84% compared with 90% for endoscopic ultrasound. MSCT staged lymph nodes with 79% accuracy versus 69% for ultrasound. The numbers for metastatic disease were 97% and 43%, respectively.

The imaging protocols included a 16-slice CT scanner and fiber-optic endoscopy with a 5 to 10-MHz electronic ultrasound array.

In a different study by another Austro-Dutch research team, Dr. Martin Uffmann and colleagues examined 21 patients with endoscopically detected gastric and duodenal lymphoma. Using a similar hydro-MSCT technique, they added up to 1.5 L of flavored methylcellulose to an intravenous spasmolytic.

Their protocol included 16-slice scanning of the entire trunk (lower and upper abdomen and chest), multiplanar reconstructions for interpretation, and correlation of MSCT against biopsy.

The investigators found that hydro-MSCT complemented regular CT staging of gastric and duodenal lymphomas. Although the hydro-MSCT did not match biopsy's characterization accuracy and detail, it helped differentiate between aggressive and indolent lymphoma, according to Uffmann.

In a study from Korea led by Dr. Y. Jeong, investigators enrolled 122 patients with gastric cancer previously diagnosed by endoscopic biopsy. They used another water-distention technique, injected a contrast agent to assess GI vascularity, and measured the thickness of normal and diseased gastric walls for characterization. They found that a gastric wall thickness of 5 mm or greater on hydro-MSCT could indicate advanced gastric cancer.

Endoscopic ultrasound is the current standard of care for GI cancer diagnosis and staging, but it has limitations. Malignant lesions sometimes obstruct certain GI structures, further restraining endoscopic ultrasound's already limited field-of-view.

Hydro-MSCT could offer a complementary imaging approach. It will allow physicians to improve therapy management according to the T and N stages of disease, Schima said.