BY MITCH LESLIE

Open wide for your ultrasound.

More and more patients are hearing these words -- or similar ones -- because more and more doctors are using ultrasound to look at the body from the inside, scanning previously hard-to-see parts of the digestive system like the esophagus and pancreas.

In this technique, known as endoscopic ultrasonography, an ultrasound transducer is fitted to the end of a standard endoscope and slipped down the esophagus and into the stomach. From this novel vantage point, doctors can get a detailed view of the condition of the digestive system.

And the technique is good for more than looking. Guided by ultrasound images, a gastroenterologist can also pluck samples of tissue for biopsy or deliver treatments like gene therapy directly to a tumor. This type of ultrasound is particularly useful for "staging," or determining how far a tumor has progressed.

"It does staging better than a CT scan, better than anything except surgery," said Jacques Van Dam, MD, PhD, a professor of medicine who brought endoscopic ultrasonography to Stanford when he emigrated from Harvard last summer. Van Dam is clincial chief of gastroenterology and hepatology as well as director of endoscopy at Stanford Hospital, which is the only hospital in Northern California using the technique for both diagnosis and treatment.

Good old external ultrasound has taken some great baby pictures and is useful for visualizing organs such as the liver, but it has limitations. Sound waves, upon which ultrasound depends, are blocked by bone and peter out in air, making it difficult to view some of the organs in the chest and abdomen, Van Dam said. For example, the esophagus is shielded by ribs on one side and the air-filled lungs on the other. Likewise, the pancreas is hard to see because it lies between the air-filled stomach and small intestine.

Placing the ultrasound transducer very close to the target organ eliminates this interference. Cardiologists have been doing something similar for years when they perform an echocardiogram -- which is an ultrasound of the heart -- and insert the transducer into the esophagus. For endoscopic ultrasound, the sound waves emanate from a long cap that attaches to the end of the endoscope. Like the scope, the transducer is about 14 millimeters in diameter -- less than the width of a dime.

Patients are awake but sedated as the endscope is inserted into the esophagus and guided into position. An anesthetic spray reduces the discomfort in the throat as they swallow the tube. Van Dam explained that the endscope may have to be in place for more than an hour as the gastroenterologist checks the organs, lymph nodes, blood vessels and any tumors. "There's a lot to see," he said. The endoscope can also be inserted into the rectum and maneuvered into the large intestine to examine that organ.

Diagnosing and treating cancer are the main uses for this kind of ultrasound, Van Dam said. Besides inspecting and staging a tumor, the doctor can see whether the tumor has invaded the surrounding blood vessels. Because the exam can determine if cancer is inoperable, it can spare a dying patient the ordeal of unnecessary surgery, he said. Small needles attached to the endoscope and aimed with ultrasound can suck up tumor cells to be analyzed. The same needles can inject the tumor with drugs and even gene-therapy agents.

Precise aiming also allows delivery of pain-soothing treatments for pancreatic cancer. Patients with this disease endure wracking abdominal and back pain, but narcotics cause unpleasant side effects like sleepiness and constipation, Van Dam said. Using endoscopic ultrasound, a doctor can insert a needle into the celiac plexus, a knot of tissue where the nerves from the pancreas meet before heading to the spinal cord. "It's like a fuse box," Van Dam said, and injecting alcohol into it kills the nerves and eases the pain.

In some ways, endoscopic ultrasound is just like the familiar external variety. The images look the same and can be saved on videotape or as stills.

Endoscopic ultrasound isn't brand new -- it was invented about 15 years ago but has been slow to catch on in the United States. Van Dam said the technology is alien to U.S. gastroenterologists who, unlike their European and Asian counterparts, have usually left ultrasound to the radiologists.

To learn this technique, American specialists have to plunge into unfamiliar subjects like three-dimensional imaging, and only three other university hospitals in California use endoscopic ultrasonography for both diagnosis and treatment -- UC-Irvine, UCLA and UC-San Diego. But, Van Dam added, gastroenterologists are accustomed to the perspective: looking at the body from the inside instead of from the outside.

Van Dam said the ultrasound transmitter doesn't increase the already low risk of endoscopy -- rare complications can include internal bleeding and punctures of the wall of the digestive tract. At the moment, he is directing Stanford's new program in endoscopic ultrasonagraphy, and he expects to do about 250 ultrasounds this year.