Dear Doctor: How necessary is the gallbladder? I recently had two flare-ups of what turned out to be gallbladder attacks. My doctor said that if I have another attack, he would recommend removal of the gallbladder. But don't I need it?

Dear Reader: To begin to answer your question, let's first look at the liver, which is next to the gallbladder. The liver produces bile, which contains bile salts. These salts are secreted into the small intestine after eating, helping to emulsify fats so that they can be absorbed more easily. Some of the bile is also stored in reserve within the gallbladder. While bile is obviously important, the benefit of bile storage in the gallbladder is more complex.

Now we have to look at why your doctor is considering the removal of the gallbladder. Gallstones occur when the bile in the gallbladder is saturated with either cholesterol or bilirubin, formed by the breakdown of red blood cells. In the Western world, having gallstones is quite common. The problem with these stones is that they can lead to inflammation and infection of the gallbladder; they can also get trapped within the duct that leads to the small intestine. Both of these cases require surgery.

However, a gallstone can also block a duct leading from the gallbladder; this occurs when the gallbladder contracts during eating. The contraction of the gallbladder, in addition to the blockage of the duct, leads to increased pressure in the gallbladder and pain in the upper abdomen toward the right side. A fatty meal can cause greater contraction of the gallbladder and thus more pain.

To prevent further attacks of what is termed biliary colic, you could consider staying away from high-fat foods and taking medication to help dissolve the stone. However, the success rate of these combined measures in preventing further attacks is only 30 percent. To prevent more attacks, not to mention the possible complications of gallbladder or bile duct infections, the majority of people opt for the removal of the gallbladder. In fact, each year in the United States, 800,000 people have their gallbladder removed. Among those who have the surgery done electively for biliary colic, 72 percent have a resolution of symptoms; for the others, the symptoms turned out to be unrelated to gallstones.

As for whether the gallbladder is necessary, consider the aftermath of gallbladder removal. Because bile is helpful for the absorption of fats, one would think that gallbladder removal would create a problem in this respect. That's not the case. The liver still produces the bile needed to absorb fats.

One symptom that does increase after gallbladder surgery is flatulence. The reason is unknown, but the symptom doesn't appear to be physiologically serious.

Undoubtedly, there are benefits to having a gallbladder, so make sure your symptoms are related to the organ. That said, you can live a long and healthy life without a gallbladder. Here's the take-home message: Recurrent attacks of biliary colic would indeed seem to warrant removal of the gallbladder, not only to prevent further attacks, but also to decrease your chance of future gallbladder infection.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: My family is planning a trip to Hawaii in a few months, and we've been hearing about a condition called rat lungworm disease. What is it? And is there anything we can do to prevent infection?

Dear Reader: Rat lungworm, a disease that affects the spinal cord and the brain, is caused by a roundworm known as Angiostrongylus cantonensis. It's a parasite, which means it requires a host to live, grow and reproduce. Although rat lungworm disease is most commonly found in Southeast Asia, the Caribbean and certain tropical Pacific islands, it is now established in Hawaii. So far in 2017, at least nine cases of rat lungworm disease have been reported throughout the state.

As with a number of other previously rare or site-specific diseases, international travel, trade and shipping are playing a role in expanding the parasite's reach. In recent years, the roundworm that causes the disease has also been found in Alabama, Florida, Louisiana and California.

The adult form of the roundworm lives in rats, which excrete the larvae in their stool. When snails and slugs feed on infected rat stool, they become carriers of the parasite. Larvae may also be found in freshwater prawns, crabs, frogs and fish. People become infected when they eat raw or undercooked portions of these foods. Some individuals report becoming infected by eating vegetables, fruit or salad greens that were not properly washed and were contaminated by snails or slugs.

Once the larvae enter the human body, they burrow through the walls of the digestive tract and enter the blood vessels. This eventually brings them to the meninges, the membrane that surrounds the brain and spinal cord. But because humans are not appropriate hosts for this roundworm, the larvae soon die.

It's the presence of these dead larvae in the cerebrospinal fluid that results in harm to humans. They trigger the release of a flood of white blood cells known as eosinophils, one of whose jobs is to attack foreign substances. This outpouring of white blood cells results in severe inflammation known as eosinophilic meningitis.

Symptoms, which can include headache, stiff neck, hypersensitive skin, visual disturbances, fever, nausea and vomiting, vary from person to person. The disease lasts from one week to several months and resolves on its own. In rare cases, it can result in coma or death.

As for what you can do to protect yourself, the state of Hawaii and the Centers for Disease Control and Prevention offer the following advice:

-- Thoroughly wash all salad greens, raw fruit or vegetables under running water.

-- The snails and slugs that carry rat lungworm larvae can be quite small and easy to miss. This means you must wash leafy greens piece by piece, both front and back. Be sure to examine them closely before adding them to a meal.

-- When dining out, ask your server whether all fresh produce is carefully cleaned.

-- If you order freshwater prawns or fish, ask that they be cooked to an internal temperature of at least 165 degrees.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I recently had an annual physical and everything seemed normal. But the bottoms of my feet feel as if they're on fire. What could be the cause? And what can I do?

Dear Reader: The symptoms that you describe sound typical for polyneuropathy (sometimes termed peripheral neuropathy). Polyneuropathy is usually related to degeneration of the part of the nerve cell (the axon) that conducts nervous impulses between nerve cells. Nerve cells with longer axons -- the ones that go to the feet -- are affected first, and the burning and tingling symptoms, often first noticed at night, can interfere with sleep.

Diabetes is the most common cause of polyneuropathy. Constant elevations of blood sugar lead to decreased blood flow to the nerves and, potentially, nerve inflammation. This affects the nerves' ability to process sensation and, when diabetes is severe and longstanding, can lead to the complete loss of sensation in the feet. Symptoms can subside once blood sugar is under control. This seems an unlikely diagnosis in your case because, if you had diabetes, your doctor would have mentioned it.

Low thyroid levels (hypothyroidism) also can lead to polyneuropathy. Initial symptoms can be a burning or loss of sensation in the feet. Rarely, this can also lead to muscle weakness in the legs. Your doctor may have already checked your thyroid level with a blood test during your physical. If caused by hypothyroidism, the symptoms would improve with thyroid hormones.

B12 deficiency -- detectable by a blood test -- is a possible cause as well, but it's generally found only among people who are malnourished, following a vegan diet or who have problems absorbing B12 in the small intestine. While rare, B6 deficiency can also cause polyneuropathy; a more common cause of polyneuropathy is B6 toxicity from mega doses of B6.

Conditions like HIV and Lyme disease can lead to polyneuropathies, as can an elevation of immunoglobulins seen in bone marrow conditions such as multiple myeloma and Waldenstrom macroglobulinemia. The latter can be assessed by checking the blood's immunoglobulin levels.

Exposure to certain medications, chemotherapies or heavy metals can cause polyneuropathy as well. One widely available toxic chemical, alcohol, also can lead to nerve damage in the lower legs. In a survey of 107 patients with chronic alcoholism, 32 percent suffered from neuropathy in the lower legs. This alcohol-induced nerve dysfunction can also affect the nerves to the muscles, causing weakness, as well as the nerves to both the bladder and intestines, causing urinary and bowel problems.

Lastly, polyneuropathies can occur in genetic disorders. These are often diagnosed by a neurologist and identified only after other causes have been ruled out. Even after an exhaustive search, a reason for the neuropathy may not be found.

I would make mention of these symptoms to your doctor. If you drink alcohol consistently and heavily, you should stop. Similarly, if you're taking large doses of B6, stop this as well.

In any case, polyneuropathy should not be ignored. It often has a cause that needs to be investigated further.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)