Volume 18 Number 1 Winter/Spring 2001

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inside-out ultrasound

A new way to view the digestive system.

BY MITCH LESLIE

OPEN WIDE FOR YOUR ULTRASOUND. * More patients are hearing these words -- or similar ones -- because 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 an endoscope and slipped down the esophagus and into the stomach.

And the technique is good for more than looking. Guided by
ultrasound images, a gastroenterologist can pluck tissue samples for biopsy or deliver treatments directly to a tumor. This type of ultrasound is especially useful for "staging," or gauging how far a tumor has advanced. "It does staging better than a CT scan, better than anything except surgery," says professor of medicine Jacques Van Dam, MD, PhD, who brought the technique to Stanford when he came from Harvard last summer. Now Van Dam is clincial chief of gastroenterology and hepatology, and director of endoscopy at Stanford Hospital -- 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 says. 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. With an endoscope a doctor can place the ultrasound transducer very close to the target organ and eliminate this interference.

Patients are awake but sedated as the endscope is inserted into the esophagus and guided into position. The sound waves emanate from a long cap at the end of the endoscope. Like the scope, the transducer is about 14 millimeters in diameter -- less than the width of a dime. An anesthetic spray reduces the discomfort in the throat as they swallow the tube. Van Dam explains 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 says. 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 says. 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, Van Dam says. 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 says. 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. 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 this country. Van Dam says the technology is alien to U.S. gastroenterologists who, unlike their European and Asian counterparts, have usually left ultrasound to the radiologists. Only three other university hospitals in California use endoscopic ultrasonography for both diagnosis and treatment -- University of California-Irvine, UCLA and UC-San Diego. To learn the technique, gastroenterologists have to plunge into unfamiliar subjects like three-dimensional imaging. But, Van Dam adds, gastroenterologists are accustomed to the perspective: looking at the body from the inside instead of from the outside. And the ultrasound transmitter doesn't increase the already low risk of endoscopy, he adds.

Now that Stanford's program in endoscopic ultrasonagraphy is rolling,Van Dam expects the team to do about 250 ultrasounds this first year. SM