Virtual gastroscopy offers endoscopy alternative

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CT gastroscopy, or virtual gastroscopy, is almost equally useful in distinguishing between malignant and benign gastric ulcers, according to research published this month in Radiology.

Although gastric cancer is one of the least common cancers in North America, it is the eighth leading cause of cancer death in the United States. It is the second-most common cause of death due to cancer in Asians from China, Japan and Korea. As with most cancers, early detection is critical to optimal patient outcome.

Patients with gastric ulcers are encouraged to undergo endoscopic and histopathologic follow-up until their ulcers have healed to ensure they are not malignant. However, due to the invasive nature of endoscopy, as well as its cost, many patients opt out of the procedure.

Images of malignant gastric ulcer in 65-year-old woman, with atypical benign morphologic feature of the ulcer base on VG image. (a) VG image shows en face view of ulcer at the low gastric body with even ulcer base (arrow). (b) Endoscopic image shows oblique view of ulcer and an uneven ulcer base (arrow). Image and caption courtesy of the Radiological Society of North America.

Although CT colonography has begun to enjoy mainstream support, CT gastroscopy has not been widely used.

“Gastric CT imaging by means of 3D virtual gastroscopy (VG) and air distention of the stomach now makes better detection of subtle mucosal changes possible, and it can be used to provide images that are almost as detailed as those produced by using endoscopy,” the authors noted.

Researchers from the departments of medical imaging, gastroenterology, internal medicine and pathology at Kaohsiung Medical University in Kaohsiung City, Taiwan, conducted the study of 115 patients with gastric ulcers. All patients were evaluated with endoscopy and VG for the differentiation of malignant and benign gastric ulcers.

Two gastroenterologists conducted the endoscopic exams on the cohort using an end-viewing fiber-optic panendoscope (GIF-XQ240, Olympus). Each gastroenterologist reviewed the endoscopic images, made an evaluation, then met with their colleague to form a consensus. In addition, six biopsy specimens were collected from the edge and base of the ulcer from each patient.

The CT exams were performed on either a 16-slice system (LightSpeed H16, GE Healthcare) or a 64-slice unit (Brilliance 190P, Philips Healthcare). All patients had fasted for at least eight hours prior to the exam, and were given oral gas-producing crystals with water to distend the stomach before the procedure.

CT scans were obtained from the diaphragmatic domes to 2-cm below the lower margin of the air-distended gastric body. Interpreting physicians, who were blinded to the results of endoscopic and pathologic exams, independently created and interpreted the VG images in a 3D workstation. Each of the two gastrointestinal radiologists created and reviewed the VG features and made a record independently and then met with each other to come to a consensus evaluation.

The performance of VG and endoscopy for the diagnosis of benign and malignant gastric ulcers was evaluated by using histopathologic results as the reference standard.

At histopathologic exam, 39 gastric ulcers were benign, while 76 were malignant. VG and endoscopy had sensitivities of 92.1 and 88.2 percent, respectively, for overall diagnosis of malignant gastric ulcers; and specificities of 91.9 and 89.5 percent, respectively, for overall diagnosis of malignant gastric ulcers.

Endoscopy demonstrated better sensitivity in depicting malignancy according to ulcer base, 85.5 percent, compared with VG’s 68.4 percent; however, VG was more specific in depicting malignancy according to ulcer margin, 78.4 percent, compared with endoscopy’s 63.2 percent.

The researchers observed that although endoscopy and VG are almost equally capable of depicting malignancy by using the criteria they studied, the decreased discomfort of a VG exam may make it a preferred means of distinguishing benign from malignant gastric ulcers in the future, particularly for patients who have contraindications to or who are unable to undergo conventional endoscopy.

“The relative reduction in discomfort of the non-invasive VG examination may make it a good potential alternative means for evaluating ulcers,” they concluded.