Magnetically Controlled Capsule Endoscopy

The system has three parts. The capsule itself is a sealed device roughly 11 by 26 millimetres containing one or two cameras, light emitting diodes, a battery, a radio transmitter and a small permanent magnet. Outside the body, a magnetic control unit generates a field that couples with the magnet inside the capsule, and this unit is moved by a robotic arm or a motorised frame so the operator can rotate the capsule, tilt it and lift it through the fluid in the stomach. A recorder worn in a belt receives the images and displays them live to the operator, who steers with a joystick or console while watching the view from inside the stomach. After the gastric examination the capsule is left to travel on through the small bowel, recording continuously, and the images are reviewed afterwards on a workstation.

The examination is done after an overnight fast. Shortly before it begins, the patient drinks water, often with an agent that removes bubbles and one that loosens mucus, so the stomach is distended and the lining is visible through a clear fluid layer. The capsule is swallowed with water and, once it is in the stomach, the operator brings the magnetic unit close and takes control. By moving and rotating the external field, the capsule is walked systematically around the stomach in a defined sequence, examining the cardia, fundus, body, angulus, antrum and pylorus, with the patient turned between positions so that different parts of the stomach come to lie under the fluid or in the air. The operator records still images and clips as the survey proceeds. The gastric part usually takes about 15 to 30 minutes. Magnetic control is then released, the capsule passes through the pylorus and continues through the small bowel by natural peristalsis, transmitting for several more hours. The patient goes home with the recorder and returns it later, and the capsule is passed in the stool and discarded.

This is a diagnostic examination rather than a treatment. It is used to look for gastritis, ulcers, erosions, polyps, submucosal lesions, vascular abnormalities and tumours of the stomach, and it continues on to examine the small bowel, which conventional gastroscopy cannot reach. It helps people who need their stomach examined but cannot or will not undergo a conventional gastroscopy: those with a strong gag reflex, marked anxiety about the procedure, or medical reasons to avoid sedation, and older or frail patients in whom sedation carries risk. It is also used where a population screening programme for gastric cancer needs an acceptable, non-sedated examination. It is not suitable where there is a known or suspected narrowing or obstruction anywhere in the digestive tract, where swallowing is unsafe, in pregnancy, or in patients with a pacemaker or other implanted electronic device, because of the magnetic field.

The clear benefit is comfort. There is no tube, no throat spray, no sedation, no recovery bay and no need for an escort home, and most people describe swallowing the capsule as no more difficult than taking a large tablet. Published comparisons with conventional gastroscopy report good agreement for clinically significant gastric findings when the preparation and the steering protocol are followed. The limitations are equally clear. Nothing can be biopsied, so a finding that needs a tissue diagnosis, such as an ulcer or a suspicious lesion, means a conventional endoscopy is still required, and nothing can be treated, so bleeding cannot be stopped and a polyp cannot be removed. The quality of the examination depends heavily on the preparation and on the operator's technique. The most important risk is retention of the capsule at a narrowing, which is uncommon but may need endoscopic or surgical removal, and patients are asked to confirm that the capsule has passed. Magnetic resonance imaging must not be performed until it has.