Thursday, May 25, 2017

The Intestines: More Than Twenty-Seven Feet Of Tubing

Do you know how long you can survive without food or water? The answer may vary depending on how well stocked you are to start (and the environment - how hot/dry it is), but on average, we can survive about a month without food, and 10-14 days without hydration. When you think about it, we are all pretty close to death if we ignore our intestines.

The intestines are soft, mucous-coated, muscular tubing that connect the stomach to the anus. The intestine performs different functions depending on where it is along the digestive tract. The small intestine (it's called small because it has a relatively small diameter) is about 22 feet long, and the first foot or so (called the duodenum) is responsible for initiating nutrient absorption. In our previous reviews of the liver and pancreas we learned that food is broken down in the small intestine with the help of bile (a kind of soap produced by the liver) and pancreatic enzymes that are squirted into the small intestine when food passes by.

The duodenum absorbs most of our food's iron and calcium, as well as some minerals, and neutralizes the acidic food mixture from the stomach. The next segment of the small intestine (the jejunum) is responsible for the majority of nutrient absorption including sugars, amino acids, and fatty acids. And the final segment (ileum) absorbs vitamin B12 and reclaims bile. The inner lining of the intestine has microscopic folds that serve to increase the surface area in contact with food, so that nutrients can be actively or passively transported across the wall and into the bloodstream where they can travel to all the cells of the body. If we spread out all the folds, the intestines of one human would actually cover an area the size of a tennis court!
 
The small intestine empties into the colon (which has 3 segments: ascending, transverse, and descending) which is about 5 feet long. The colon primarily extracts liquid from food, absorbing most of its water content. The colon is an important storage system for waste, and is home to thousands of kinds of healthy bacteria that influence and strengthen our immune systems.

The most common problems that occur with our intestines include:
  1. Ulcers:  food that has been mixed with stomach acid, bile, and strong pancreatic enzymes can be irritating to the intestinal lining. If the lining does not produce enough protective mucous, this highly acidic sludge can cause painful ulcers, chronic bleeding, and eventual anemia.
  2. Muscle contraction issues (too much/too little).  Constipation and diarrhea are both related to food transit time. When intestinal muscles contract slowly, food passes through them more slowly and their water content has more time to be absorbed. Constipation results, with hard stool caused by dryness. Diarrhea, on the other hand, may be caused by overactive muscle contractions that move food along very quickly. Irritable bowel syndrome can be a result of both fast and slow contracting muscles. In rare cases, the bowels can twist on themselves and cut off their own blood supply (called an ileus) or telescope into themselves (called an intussusception). These twists are very painful and represent a surgical emergency.
  3. Malabsorption:  autoimmune diseases (such as Crohn's disease and ulcerative colitis), allergies (such as Celiac disease or gluten allergy) and bowel surgeries (including bariatric surgery) can affect the absorption of nutrients in the intestine. Nutritional deficiencies can cause anemia, with calcium, iron, and magnesium often being too low.
  4. Food Intolerance:  some of us have difficulty digesting milk protein (lactose intolerance), or high fiber foods. Cheese, caffeine, or certain plants (such as soy) can cause bloating, gas, and abdominal pain for some people.
  5. Food Allergies:  food allergies (as opposed to intolerances) are more than uncomfortable, but dangerous. Peanut and shellfish allergies, for example, can cause a rapid immune response that can affect the entire digestive tract, including the mouth and throat, and cause difficulty breathing and sudden swelling.
  6. Wall herniations:  as we age, intestinal walls (especially in the colon) tend to weaken. Small outpouchings called diverticula can trap food and become infected (known as diverticulitis). When antibiotics are not enough, sometimes parts of the colon need to be removed.
  7. Infections:  intestinal infections are very dangerous because of the bacteria that live inside the small intestine and colon. When these bacteria (such as E. coli) get outside the intestine and into the blood stream, they can cause rapid sickness, fever, and even death if not treated quickly. Appendicitis is an infection of a worm-like outpouching near the attachment of the small and large intestines. More common outside the U.S., parasites can be accidentally ingested and cause bleeding or diarrhea, and spores from clostridium difficile (known as c.diff) or cholera bacteria are contagious and may require hospitalization due to severe dehydration.
  8. Polyps and Cancer:  intestines are very active tissues, and they replace the first layer of cells in their lining every four to five days. Since these cells are rapidly dividing and replacing themselves all the time, it makes sense that they are at risk for dividing incorrectly, and causing polyps (growths) to develop. Most cancers develop from inside these polyps, so removing polyps is a priority during colonoscopies.
How can you keep your intestines healthy?
  1. Eat a healthy, high-fiber, low processed food diet.  High fiber diets, lower in red meat have been associated with a reduced risk of colon cancer. Whenever possible, eat whole foods (as opposed to highly processed, canned or pre-prepared food), grains, plants, and lean fish and poultry proteins.
  2. Drink plenty of water.  Water assists in absorption of nutrients and helps to prevent constipation.
  3. Avoid trans fats and charred meat.  Partially hydrogenated oils in baked goods and margarines are absorbed by the intestines and increase the risk of diabetes, heart disease, and stroke. Charred and pickled meats may increase the risk for colon cancer as well.
  4. Get regular colonoscopies starting at age 50, or sooner if you have colon cancer in your family.
  5. Limit alcohol intake.  Alcohol is associated with a higher risk of colon cancer.
  6. Take vitamin supplements if you have a malabsorption problem. For some people who can’t absorb B12 or iron, IV or injectable versions of these vitamins and minerals are available to bypass the gut. For most Americans, all the vitamins and minerals necessary for good health are available in a healthy diet.
  7. Take probiotics. Good gut bacteria are important to maintain, especially after a course of antibiotics. You can restore your gut flora by eating yogurt with live cultures or acidophilus tablets.  Probiotics can reduce your risk of colon infections like C. diff after antibiotic treatments.
  8. Report blood in your stool to your doctor.  Bloody or black stool may be caused by hemorrhoids, ulcers, or colon cancer. Either way, don’t be shy to talk to your doctor right away if you see blood in your stool.
With 25 feet of gut tubing and a tennis court-sized absorptive area, shedding all its inner lining cells every 4-5 days, and moving about 5 pounds of food per day through the system via muscular contractions, the human intestinal tract is an amazing piece of engineering. Keeping it running smoothly can be challenging, but luckily there are effective dietary and over-the-counter medication options to keep us out of most trouble. For other issues, we can rely on our primary care physicians or friendly neighborhood gastroenterologists and surgeons.

References


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Friday, May 19, 2017

The Lungs: You, Yes YOU, Will Probably Be On A Ventilator At Some Point

Have you ever wondered why a person needs to be on a ventilator? Ok, so maybe you haven't. Now that you think about it, though, do you know why? Well, it's usually one of two reasons - either their lungs are damaged and they need help getting air in and out of them, or their nervous system isn't telling the chest muscles and diaphragm to pull the lungs open and closed - perhaps because the person is unconscious, or has a brain or spinal cord injury. Either way, mechanical ventilation (with a bag-valve-mask or machine) is keeping a whole lot of Americans alive. Just think about how many millions of people use it during general anesthesia.

According to the American College of Surgeons, the average American undergoes 3.4 inpatient surgical procedures in their lifetime. Therefore, most of you readers have been (or will be) mechanically ventilated at some point. So let's discuss how this works.

The lungs are basically fluffy sponges with very elastic scaffolding and a network of delicate blood vessels interwoven throughout its tissue. These sponges are stuck on to the chest wall by suction action between their outermost layer (pleura) and an air-tight fluid layer. If you've ever tried to get a flat piece of glass off a wet stone surface, you know the power of that kind of suction.

The lungs are passive. They don't have the ability to move themselves - they are simply sucked open by the vacuum that is created when muscles pull down and out on their pleura. The largest muscle involved in pulling the lungs open is called the diaphragm, and it spans the entire chest - forming a barri
er inside between the chest contents and the abdomen. The diaphragm is triggered to contract by a nerve (called the phrenic nerve) that is stimulated by a part of the brain that doesn't require conscious thought. For this reason, you go on breathing without having to think about it.

Lungs have air tubes that resemble an upside-down tree. The trunk is the trachea (also known as the "wind pipe") and it branches into the right and left lungs and then sub-branches into each of the lobes of the lung, and then has tinier branches that interface with microscopic blood vessels. The tree trunk and branches have muscular walls that can expand and contract to some degree. The walls between the very tips of the "tree branches" and the blood vessels are so thin, that gas can pass through them (most importantly oxygen - needed to fuel all the cells in our body - which is constantly being exchanged for carbon dioxide). Once the gas is exchanged in the blood that is pumping through the lungs, it can be expelled back up through the branches and out of the windpipe as the lungs "snap back" when the chest muscles and diaphragm relax.

Knowing how the lungs work helps to explain the problems that can occur to them at various levels. So let's review the most common lung problems:
  1. The airway and its branches can be blocked. This is usually due to mucous from infections, or from tar build up from smoking. Airways can be blocked by blood (in the case of an injured lung or lung cancer) or water (in the case of drowning). When the airways are plugged with some kind of fluid, it can be life threatening very quickly. Narrow airways may produce a wheezing kind of sound.
  2. The suction holding the lungs open can be broken. This can happen spontaneously (usually in young men) or most commonly from an injury (such as a car accident or a fall that breaks ribs). When air gets into the space between the pleura and the chest wall, the lung usually collapses (either partially or totally) and needs a surgical procedure (such as a chest tube) to fix it. This is called a pneumothorax.
  3. The nerve to the diaphragm can be injured. When the phrenic nerve is irritated, hiccups occur. When the nerve is damaged (or the part of the spinal cord that it stems from is injured) the diaphragm can become paralyzed. Without the main muscle to suck the lungs open, breathing becomes shallow and more difficult.
  4. Blood vessels can be inflamed or get clotted. When blood clots travel through the blood stream to the lungs, they become trapped at the narrowest part of the vessels, causing damage that cannot be repaired. Auto-immune diseases (such as Churg-Strauss syndrome) that affect the tiny blood vessels can cause inflammation that prevents effective air exchange.
  5. Muscles surrounding the air tubes can spasm or clamp down. Allergies or environmental stimuli (like cold air) can trigger the muscular layer of the air tubes to contract, suddenly narrowing the air flow. This causes asthma symptoms. In some cases, chronic inflammation can irritate the muscles, causing an ongoing obstruction to air escape.   
  6. The elastic fibers in the lung "scaffolding" can snap. Toxins found in cigarette smoke (as well as a genetic condition called alpha-1 anti-trypsyn disease) cause the elastic fibers of the lungs to break down over time, reducing the lung's natural elasticity. The lungs stretch out, enlarge, and go limp so that when the vacuum suction is triggered by the diaphragm pulling on them, not much air is exchanged.
The most common lung diseases, and their treatments, will now make perfect sense (I hope):

COPD (chronic obstructive pulmonary disease - which includes emphysema and chronic bronchitis - is almost always caused by smoking). COPD is a combination of three lung issues: problem #1 (mucous and goop in the airways) along with #5 (inflammation causing airway constriction) and #6 (elastic fibers snap with exposure to smoke over time). Treatment includes smoking cessation, anti-inflammatory medications, and puffers that relax the airway muscles. Unfortunately, the elastic fibers cannot be fixed once they are broken. Advanced COPD often causes a cycle of bronchitis due to tiny breaks in the bronchial lining that become regularly invaded by local lung bacteria.

Asthma - asthma is mostly a #5 issue. Treatment includes avoiding asthma triggers and taking medicines that relax (or dilate) those airway muscles. However, inflammation certainly plays a role in asthma, and anti-inflammatories (like leukotriene inhibitors) can be an important part of treatment.

Pulmonary Embolus (this is another word for blood clot in the lungs). This is a #4 issue. Pulmonary emboli almost always start as a leg clot. The clot can break off and travel to the lungs where it gets wedged into a small space and is trapped, cutting off the oxygen supply to the tissue that the vessel supplies. Leg clots should be treated with prescription blood thinners to prevent pulmonary emboli, because once the lung damage is done, it cannot be repaired. Leg clots occur more commonly in people with sedentary lifestyles or obesity. Women on birth control pills and people with clotting disorders or leg injuries are also at higher risk.
Pneumonia is primarily a #1 type of problem. Bacteria, viruses, or sometimes yeast or fungus can grow in lung mucous, causing pus pockets that can get into the blood stream and make a person very sick. People with pneumonia usually feel rotten, have high fevers, and may have difficulty breathing. Antibiotics should be targeted to the kind of infection that is occurring, and people may need to go to the hospital if breathing becomes difficult. Aspiration pneumonia can occur when a person inhales food into the lung. Interestingly, food usually lodges in the right-sided airway because it is a straight shot down from the mouth.

Bronchitis is primarily a #1 type of problem. Bronchitis refers to an infection of the higher parts of the airway - usually the tree trunk or first branches. It is not usually as serious as pneumonia, and can be treated with antibiotics and anti-inflammatory medications if necessary.

Pulmonary Fibrosis is a #6 type of problem. There are some lung diseases that cause a hardening of the lungs by scar tissue formation. Diseases such as sarcoidosis affect the elasticity of the lungs, making them stiff and hard to aerate.

Lung Cancer is a mix of #1 and sometimes 2 or 4. The most common symptom of lung cancer is coughing up blood. The cancer cells destroy the healthy lung tissue around them and can break the delicate blood vessels or block the air pipes. Depending on where the cancer is located, it may also break into the pleural space and cause a collapsed lung, though this is quite rare.

Pulmonary Edema this is a type 1 and 4 issue. When the heart is not pumping blood effectively, or the blood can't get through the lung because of tissue damage, pressure builds up and the blood vessels leak the fluid portion of the blood into the surrounding area. The lungs become swollen with watery fluid. This is most commonly caused by congestive heart failure.

Although you probably don't spend much time thinking about your lungs, they are an amazing and important part of your body. Luckily, we have developed a lot of strategies to keep them working - from mechanical ventilation, to anti-inflammatory meds, antibiotics and muscle relaxants, to surgical procedures, blood thinners and even lung transplants. But the most important thing you can do for lung health is to quit smoking, because once those fluffy sponges lose their bounce, we still don't have a way to get it back.

References
https://medlineplus.gov/ency/article/000066.htm
http://www.mayoclinic.org/diseases-conditions/copd/home/ovc-20204882
http://www.mayoclinic.org/diseases-conditions/asthma/basics/definition/con-20026992

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Friday, May 12, 2017

The Liver: A Multi-Purpose Factory With Amazing Regenerative Powers

When I think about the liver, I’m often reminded of a comedy sketch from a Monty Python movie. In the sketch, organ donor nurses arrive at a patient’s home, requesting her liver before she is deceased. When the patient complains that she “hasn’t finished with it yet” the nurses launch into a whimsical song about how insignificant humans are compared to the vast size of the universe, and in the end, the patient reluctantly agrees to give them her organ, and the surgery commences in her living room. All completely silly, but the song is quite catchy.
   
But, I digress. The liver is a 3 pound, football-sized organ that sits just under the right rib cage. It is remarkably complex in its function, and does everything from detoxifying the blood (including breaking down medications and dumping them into the intestine where they are removed in the stool), producing blood clotting factors and various proteins, digesting fat and protein (the gall bladder stores soap-like chemicals produced by the liver), and storing glucose, vitamins and minerals, and helping to control metabolism. I think of it as a big, multi-functional factory that we can't live without.

What injures the liver?
  1. Alcohol:  chronic, excessive alcohol consumption can cause inflammation of the liver cells which can lead to cirrhosis and eventually liver failure.
  2. Obesity: being very overweight can cause fat to be stored in the liver which disrupts its function. "Fatty liver" can cause liver failure in severe cases.
  3. Hepatitis Viruses: there are several viruses that attack the liver cells and can cause severe damage. Hepatitis B and C are the most dangerous, though great strides have been made in treating these viruses, such that hepatitis is now considered curable in most cases.
  4. Medications: the liver is full of enzymes that break down toxins and medications, but some medications can irritate, inflame, or even cause liver failure in large quantities. Acetaminophen is probably the best known liver toxin in large doses.
  5. Gall Stones: gall acts like soap, helping to break down fat and protein in the foods we eat. The extra soap (made by the liver) is stored in a sac called the gall bladder. Sometimes this soap gets a little dry and forms "stones" which can get stuck in the liver and cause pain and infections that can be life threatening. Interestingly, gall is very intensely colored (kind of neon green or yellow) and when it leaks into the blood stream, it can turn the skin yellow – which is what we call "jaundice" and is a sign of liver injury.
  6. Liver Cancer: cancer that starts in the liver is fairly rare, but very dangerous. Because all the blood returning to the heart goes through the liver, it is a common collecting station for other cancers that metastasize from elsewhere. Cancer that has not spread too widely in the liver may still be surgically removed and cured. Because amazingly, the liver is capable of regenerating - and when one of its lobes is removed, we can still survive quite nicely.
  7. Genetic Disorders: there are some genetic diseases that cause large amounts of substances to be stored in the liver (such as iron or copper) which can clog it up and enlarge it and harm its ability to function.
  8. Autoimmune Disease: sometimes the immune system attacks liver cells, resulting in significant damage to the bile ducts and liver tissue.
  9. Parasites: although we don't think much about parasites in the United States, in the rest of the world, over 35 million people suffer from liver fluke parasites (from eating undercooked or raw river fish) that crawl up into the bile ducts and can even cause cancer!
What happens when the liver fails?

Although the liver is a fairly resilient organ, due to the fact that it can actually grow back when it is injured (the only organ that can do this!) sometimes it can become injured beyond repair, and then it goes into full failure with these results:
  1. Blood flow backs up: if the liver is very inflamed and swollen, the blood that usually travels through it very easily cannot get through. This causes a big back up, and under high pressures, the liquid portion of the blood leaks into the belly (called "ascites"), and veins in the neck, face, and belly can become swollen (called "varices" and "telangiectasias").
  2. Gall spills into the bloodstream: causing yellow-looking skin or "jaundice."
  3. The blood stops clotting: due to inability to produce clotting factors, the blood becomes very thin and prone to bleeding. In combination with the back-up I described above, you can see how bleeding is a serious risk in liver failure.
  4. Toxins build up in the blood, causing mental status changes, nausea, confusion, and lethargy.
How can I keep my liver healthy?
  1. Do not drink excessive alcohol.
  2. Maintain a healthy weight.
  3. Be careful to follow dosing instructions on drug facts labels, especially acetaminophen.
  4. If you have gallstones, discuss your options with your doctor. If you have severe right-sided abdominal pain (especially after eating a fatty meal), get that checked out right away. Infected, trapped gallstones can be life threatening.
  5. If you become jaundiced, see your doctor right away.
  6. Practice safe sex - hepatitis C virus is very contagious through sexual contact and/or through contact with infected peoples' blood.
  7. Get vaccinated against Hepatitis A and B before going to countries where they are common.
  8. Don't share needles. Hepatitis C is very contagious.
The good news is that for those with end-stage liver failure, transplantation may be an option. Liver transplants are usually very successfully, though unfortunately there are about 15,000 people on the waiting list for one right now in the United States. I myself have chosen to be an organ donor, and I hope you'll consider it too. Because (heaven forbid) if we are in an accident, at least that way we can give the gift of life to others. I have no doubt that (unlike that comedy sketch) there will not be a man who climbs out of our refrigerator to sing us a song about giving up our livers before we're finished with them!

References
https://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0072577/
http://www.mayoclinic.org/diseases-conditions/liver-problems/basics/causes/con-20025300
http://www.liverfoundation.org/abouttheliver/info/transplant/

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