Unlike the heart or the lungs, the gallbladder is one of those organs about which people know next to nothing. And no wonder, the gallbladder is little more than a storage sack. What it stores is bile, which is produced by the liver.

So what’s bile? Bile is a substance that contains the enzymes needed to help break down the fat in our food. As we digest our food, the gallbladder excretes bile through the bile ducts and into the intestine, which leads to the stomach, where it helps metabolize (break down) fat.

The gallbladder is very likely to give you problems at some point. There is a period in our lives, usually in our forties, when the changes our body has experienced—either gaining weight or losing weight or undergoing a pregnancy—can affect the gallbladder. The location of the gallbladder is critical to understanding why it can cause problems: it sits on the right-hand side of our abdomen, just underneath the liver and next to the intestines and the pancreas. So it’s anatomically predisposed to feel pressure from these other organs.

The most common disorder of the gallbladder and its bile ducts is gallstones, a condition otherwise known as cholelithiasis. It occurs when the liver begins secreting bile that contains too much cholesterol, which then crystallizes and forms stones in the gallbladder and the bile ducts. Stones can also form due to low levels of bile acids. Most gallstones are cholesterol stones.

How gallstones form is not well understood, but we assume that it has something to do with the way in which our diets alter the quantity or quality of bile we produce. The other possibility is that the gallbladder, since it not only stores but concentrates the bile, possibly removes too much water from the bile, causing some of its constituents to solidify and form gallstones.

More than 20 million Americans have gallstones, and approximately 1 million new cases are diagnosed each year. People over the age of 60 are more likely to develop gallstones than younger people, and women are twice as likely as men to develop them. But most people will walk around with gallstones all their lives and never even know they have them. Sometimes they’re found by chance on X-rays.

When people do report gallbladder pain, it is usually because of gallstones or the inflammation the stones produce. When the gallbladder contracts—to excrete bile—we feel the pressure of the stones inside. So it’s almost like holding a few marbles in one hand; when we squeeze our hand with the marbles, we feel the pressure and some tenderness. Gallbladder pain is usually felt on the right side of the abdomen, just underneath the rib cage, though sometimes it radiates to the back. It’s easy to understand why people often complain of gallbladder pain after eating a fatty meal. It occurs because the body is demanding the excretion of bile to process the fatty foods, so we feel discomfort when the gallbladder, with the stones inside, contracts to excrete the bile.

The pain from a gallbladder problem may subside and then return in a cyclical pattern. This can happen when a stone becomes stuck in the duct system and obstructs the flow of bile, then after a few hours falls back into the gallbladder or passes out through the intestines. But sometimes the pain from the gallbladder can be acute; it’s sudden, constant, and persistent. This is most likely to occur when a stone is jammed into a bile duct, creating a major obstruction, major pain, and a low-grade temperature, as well as nausea and vomiting.

If the main bile duct gets obstructed significantly, you can have an acute buildup of bile, which then backs up into the liver and gets into your bloodstream; this causes a slight jaundice of the skin.

So what to do? If the problem is gallstones, you have to have them removed. The most common solution today is to operate and remove the gallbladder sack, stones, and all via minimally invasive surgery called a laparoscopy, in which a telescope-like instrument plucks out the gallbladder through the smallest possible incision. Conventional gallbladder removal, or cholecystectomy, is a major operation that requires a large incision in the abdomen, thus raising the risk of complications from infection and bleeding.

If a patient does not qualify for surgery, there are still several options available. There are medications, such as chenodeoxycholic, that can be taken orally in an effort to break up the stones; it is excreted to the bile and helps dissolve the gallstone. But these medications are not 100 percent effective, and when people stop taking the medication, the gallstones have a tendency to form again. Another possibility is a lithotripsy, in which external shock waves are used to bombard and shatter the stones; the same method is used to remove kidney stones, albeit usually with greater success than with gallstones.

Still another approach involves injecting strong solutions directly into the gallbladder to dissolve the stones, especially cholesterol-based gallstones, but again, this technique is not totally successful.

By the way, in case you’re wondering, there are no medical or health consequences from losing a gallbladder. The gallbladder is basically a receptacle. Even after it’s removed, the bile is still going to be made by the liver, and it’s still going to go down the tubes into the intestines and into the stomach. The only difference is that fat digestion may be a little less efficient because the bile has not been concentrated by the gallbladder, so if you have your gallbladder removed, you’ll have to be particularly mindful of following a healthful diet.

Click here to check out Dr. Manny's book The Check List (Harper Collins, 2007), from which this article was excerpted.

Dr. Manny Alvarez is the managing editor of health news at FOXNews.com, and is a regular medical contributor on the FOX News Channel. He is chairman of the Department of Obstetrics and Gynecology and Reproductive Science at Hackensack University Medical Center in New Jersey. Additionally, Alvarez is Adjunct Professor of Obstetrics and Gynecology at New York University School of Medicine in New York City.

Dr. Manny Alvarez serves as Fox News Channel's senior managing health editor. He also serves as chairman of the department of obstetrics/gynecology and reproductive science at Hackensack University Medical Center in New Jersey. Click here for more information on Dr. Manny's work with Hackensack University Medical Center. Visit AskDrManny.com for more.