Obesity affects almost half a billion people worldwide. It is fast becoming the major killer, overtaking even long-term predators such as tobacco.
Its consequences range from diabetes and cardiovascular disease, which are metabolic in origin, to cancers of the endometrium, breast, and colon. Secondary complications of obesity include diabetes-linked blindness, renal failure, and psychological disturbances.
Conventional Treatments for Obesity
Obesity treatment has long focused on dietary regulation, exercise, and behavioral modification techniques. Some drugs have also been used in the treatment of obesity but are linked with unacceptable adverse effects.
Bariatric surgery is advised in patients with morbid obesity, where the body mass index is 40 or above, or even 35 with other medical conditions. These include techniques which reduce gastric volume, or those which prevent proper digestion.
These are considered to be of high efficacy in selected patient groups, both in reducing obesity and its linked complications. However, with unaltered eating habits, even bariatric surgery may be followed by a gradual return to weight gain.
In this context, gastric artery embolization or bariatric arterial embolization (BAE) is emerging as a powerful tool.
Bariatric Arterial Embolization
The stomach is supplied by left and right gastric arteries, as well as the right gastroepiploic artery, and the short gastric arteries.
Embolization of some vessels in the upper gastrointestinal (GI) tract has been a well-rehearsed practice in the treatment of GI bleeding as in portal cirrhosis with resulting portal hypertension. This technique rarely produces gut ischemia due to numerous collateral vessels in the foregut.
Bariatric arterial embolization refers to percutaneous catheter-directed left gastric artery embolization in order to induce relatively poor blood supply to the fundus, the area of the stomach that produces ghrelin.
At least two branches are occluded, introducing transarterially a sclerosant agent such as morrhuate or polyvinyl alcohol (PVA) beads of varying diameter. While the efficacy of embolization in reducing ghrelin secretion is unchallenged, the effect in terms of weight loss has not been proved as conclusively.
The Importance of Ghrelin in Obesity
The stomach is not merely a storehouse of ingested food, nor a digestive organ. It is also a neurohormonal system. The fundus carries numerous pathways for the nervous regulation of appetite and satiety.
Ghrelin is a peptide hormone released mainly from the fundus of the stomach, which regulates long-term appetite and energy maintenance. It is released under conditions of hunger or starvation and stimulates the brain to initiate food intake. The next major site of ghrelin production is the duodenum, which releases the peptide at up to 20 times lower concentrations than the fundus.
In response to ghrelin secretion, the following actions occur:
- a rise in growth hormone release
- a rise in gastric acid secretion
- Increased gastric motility
- faster gastric emptying
- reduced insulin secretion
Increased ghrelin levels lead to increased adipose tissue deposition and obesity.
Safety Profile of BAE
Complications of the procedure have included:
- Pulmonary embolism
- Perforated gastric ulcers
- Distal esophageal stricture
- Non-target embolization with unintended tissue damage
- Greater safety for the procedure involves various measures such as doing it under CT guidance, using radio-opaque alginate beams which are visualized under fluoroscopic guidance, and a special microcatheter which prevents reflux of the injected material.
Trials are still underway to establish optimum procedural guidelines for patient safety.