Mayo Clinic on Digestive Health: How to Prevent and Treat Common Stomach and Gut Problems
By Sahil Khanna
()
About this ebook
Digestive problems are among the most common reasons people see doctors and take medication. This updated fourth edition of Mayo Clinic on Digestive Health is an authoritative yet practical reference manual that includes information on everything from healthy digestion to cancer treatment. The book is packed with helpful advice on treating common digestive conditions and preventing serious disease, with information on:
Belching, bloating and gas • Celiac disease • Colorectal cancer • Constipation and diarrhea • Crohn’s disease and ulcerative colitis • Diverticular disease • Gallbladder disease • Heartburn and GERD • Irritable bowel syndrome • Liver disease • Pancreatic disease • Swallowing difficulties • Ulcers and stomach pain
Also covered are diagnostic testing, mealtime recommendations and self-care tips for relieving discomfort, and the latest information on endoscopic ultrasound, virtual colonoscopy, and the newer minimally invasive treatments for gastroesophageal reflux disease (GERD).
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Mayo Clinic on Digestive Health - Sahil Khanna
Mayo Clinic
Medical Editor
Sahil Khanna, M.B.B.S.
Editorial Director
Paula M. Marlow Limbeck
Senior Editor
Karen R. Wallevand
Senior Product Manager
Daniel J. Harke
Art Director
Stewart (Jay) J. Koski
Illustration, Photography and Production
David A. Factor, Joanna R. King, Michael A. King, Kent McDaniel, Matthew C. Meyer, James D. Postier II, James E. Rownd, Gunnar T. Soroos
Editorial Research Librarians
Abbie Y. Brown, Eddy S. Morrow Jr., Erika A. Riggin, Katie J. Warner
Copy Editors
Miranda M. Attlesey, Alison K. Baker, Donna L. Hanson, Nancy J. Jacoby, Julie M. Mass
Indexer
Steve Rath
Administrative Assistant
Terri L. Zanto Strausbauch
Contributors
Andres J. Acosta, M.D., Ph.D.; Adil E. Bharucha, M.B.B.S., M.D.; Suresh T. Chari, M.D.; Purna C. Kashyap, M.B.B.S.; John B. Kisiel, M.D.; Heather L. LaBruna; Joseph A. Murray, M.D.; Karthik Ravi, M.D.; William Sanchez, M.D.; Jacalyn A. See, M.S., RDN, LD; William J. Tremaine, M.D.; Laura Hamilton Waxman
Cover design by Stewart (Jay) J. Koski
Published by Mayo Clinic Press
Second electronic edition published 2020 by RosettaBooks LLC, New York.
© 2020 Mayo Foundation for Medical Education and Research (MFMER)
MAYO, MAYO CLINIC and the Mayo triple-shield logo are marks of Mayo Foundation for Medical Education and Research. All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher.
The information in this book is true and complete to the best of our knowledge. This book is intended only as an informative guide for those wishing to learn more about health issues. It is not intended to replace, countermand or conflict with advice given to you by your own physician. The ultimate decision concerning your care should be made between you and your doctor. Information in this book is offered with no guarantees. The author and publisher disclaim all liability in connection with the use of this book.
ISBN 978-893005-53-2 (hardcover)
ISBN 978-07953-5289-8 (ebook)
Fourth edition
Contents
PREFACE
PART 1
Digestive health basics
CHAPTER 1
Why your gut matters
Warning signs
Digestion at work
Digestive problems
CHAPTER 2
The gut microbiome
The microbiome explained
The changing gut
When a good gut goes bad
Nurturing a healthy gut
CHAPTER 3
Recipe for healthy digestion
What to eat
What to limit
Your eating habits
Physical activity
Stress
Medications
Understanding digestive disease
CHAPTER 4
Gut feelings
Difficulty swallowing
Chest pain and heartburn
Indigestion
Nausea and vomiting
Belching, bloating and intestinal gas
Abdominal pain
Diarrhea and constipation
Bleeding
Unintended weight loss
CHAPTER 5
Diagnostic tests
Blood tests
Urine and stool tests
X-rays
Computerized tomography
Ultrasound
Endoscopy
Ambulatory acid (PH) probe test
Esophageal muscle function test
Transit studies
Manometry
Defecating proctogram test (defecography)
Breath tests
PART 2
Digestive diseases
CHAPTER 6
Obesity
Why am I overweight?
Weight-loss treatments
Diet
Physical activity and exercise
Behavior changes
Prescription medications
Surgery and endoscopic procedures
Looking ahead
CHAPTER 7
Constipation and fecal incontinence
Constipation
Diagnosing constipation
Treating and managing constipation
Complications of constipation
Fecal incontinence
Diagnosing fecal incontinence
Treating and managing fecal incontinence
CHAPTER 8
Irritable bowel syndrome and food intolerances
A functional disorder
Ruling out other conditions
Over-the-counter medications
Prescription medications
Counseling
Lactose intolerance
Other intolerances
Low-FODMAP diet
CHAPTER 9
Celiac disease
How gluten causes harm
Signs and symptoms
Diagnosing celiac disease
Complications of celiac disease
A new way of eating
When diet isn’t enough
CHAPTER 10
GERD and other esophageal diseases
What’s GERD?
Varied signs and symptoms
What puts you at risk?
Associated conditions
Complications of GERD
See your doctor
Treatment starts with self-care
Medications to treat GERD
Surgery to treat GERD
Cancer of the esophagus
CHAPTER 11
Ulcers and stomach pain
An open sore
Bacteria a common culprit
Diagnosing ulcers
Treatment with Medication
Self-care steps to promote healing
Functional dyspepsia
Lifestyle changes the first step
Stomach cancer
Diagnosis and treatment
CHAPTER 12
Crohn’s disease and ulcerative colitis
Similar but different
In search of a cause
Signs and symptoms
Diagnosing IBD
Medications
Living with IBD
Surgery
Preventing complications
CHAPTER 13
Diverticular disease
Diverticulosis
Diverticulitis
Making a diagnosis
Treating diverticulitis
CHAPTER 14
Gallbladder disease
Gallstones
Gallstone attack
Are you at risk?
Making a diagnosis
Treatment options
Life without a gallbladder
Gallbladder and bile duct cancers
CHAPTER 15
Pancreatic disease
Acute pancreatitis
Diagnosing acute pancreatitis
Treating acute pancreatitis
Chronic pancreatitis
Diagnosing chronic pancreatitis
Treating chronic pancreatitis
Living with chronic pancreatitis
Pancreatic cancer
Treating pancreatic cancer
CHAPTER 16
Liver disease
What does the liver do?
Liver disease
Infectious hepatitis
Alcohol- or drug-induced hepatitis
Nonalcoholic fatty liver disease
Autoimmune disease
Inherited liver disease
Cirrhosis
Liver transplant
Liver cancer
CHAPTER 17
Colorectal cancer
Signs and symptoms
Are you at risk?
Screening
Cancer staging
Treatment
APPENDIX
FODMAP eating plan
The elimination phase
The reintroduction phase
The maintenance phase
IMAGE CREDITS
Preface
Your digestive system may seem easy to understand: You put food in your mouth. Your digestive organs break down the food. Nutrients in the food are absorbed in your intestines, and the rest is eliminated as waste. Sounds pretty simple, doesn’t it?
In fact, the human digestive system is incredibly complex. It acts both as food transporter and food processor, requiring the efficient function of many different organs to transform what you eat and drink into a mixture that fuels good health. Sometimes, things can go wrong, or the process doesn’t work as well as it should.
Mayo Clinic on Digestive Health, Fourth Edition, covers signs and symptoms, causes, diagnostic procedures, and treatment options for the most common digestive conditions, as well as preventive actions to consider. Perhaps you’ve experienced temporary discomfort from heartburn, diarrhea, constipation, nausea or excess gas and are trying to determine what may be triggering your symptoms. Maybe you’re dealing with a common condition such as gastroesophageal reflux disease, peptic ulcers or gallstones and you want information on treatment. If you have a long-term condition, such as Crohn’s disease or celiac disease, you may be seeking coping skills.
In the last decade, we’ve seen tremendous advancements in the understanding, early recognition and treatment of many digestive conditions. As an example, today we have a much better understanding of the important role your gut plays — specifically, the bacteria that reside within it — in maintaining your overall health. We’re also seeing a connection between the health of your gut and that of other systems within your body. All of this has led to a lot of speculation and misinformation surrounding what to eat — and what not to eat — for good gut health.
This book addresses a wide range of topics, providing a context for what it takes to keep your digestive system healthy and how to respond when disease occurs. Too often, people wait too long before seeking help from their doctors. In general, the earlier you address a problem, the easier it is to prevent it from becoming serious.
Here’s hoping that this book can help you enjoy a higher quality of life with fewer digestive concerns. And here’s wishing you good digestion!
Dr. Sahil Khanna
Sahil Khanna, M.B.B.S., is an associate professor of medicine at Mayo Clinic College of Medicine and Science and the head of the Comprehensive GI Interest Group within the Division of Gastroenterology and Hepatology at Mayo Clinic, Rochester, Minn. Dr. Khanna is a graduate of the All India Institute of Medical Sciences, New Delhi. He did postdoctoral research at the University of California San Diego, before completing his residency in internal medicine and a fellowship in gastroenterology and hepatology at Mayo Clinic, Rochester. Dr. Khanna’s research and clinical interests include epidemiology, patient outcomes, and emerging therapeutics for Clostridium difficile (C. diff.) infection, a topic on which he has authored several articles and made numerous presentations. Dr. Khanna serves on the editorial board of several journals and has won numerous awards including the Miles and Shirley Fiterman Award, the Mayo Brothers Distinguished Fellowship Award, the Donald C. Balfour Mayo Clinic Alumni Association Research Award, the Hartz Foundation Young Investigators’ Scholarship, and the Most Distinguished Resident Physician Award from the American Association of Physicians of Indian Origin.
Part 1
Digestive health basics
Chapter 1
Why your gut matters
Good health and a healthy gut go hand in hand. Digestion is one of the critical functions your body must perform in order to survive and thrive. The food you eat provides necessary nutrients that supply your cells with sustenance and energy so your body can develop, repair and maintain itself.
When you take a bite of food, what enters your mouth must be transformed before it can nourish your body. That’s the primary function of digestion — to break down food into smaller components and change it chemically so nutrients can be extracted and absorbed into your bloodstream (while the remainder is eliminated as waste). The breakdown of food occurs primarily through the action of digestive juices in your mouth, stomach and intestines, with assistance from the tearing, grinding action of your teeth.
When things go according to plan, the organs of your digestive tract perform a variety of specialized functions in an efficient and timely manner. But like any complex system that contains integrated parts, sometimes the process gets disrupted, and even a slight malfunction can cause problems.
When this happens, you begin to experience signs and symptoms. That’s your body’s way of letting you know something isn’t quite right. Often, the problems are minor and infrequent, but sometimes they can be complex and chronic.
Warning signs
Heartburn, pain, cramps, bloating, nausea, vomiting, diarrhea, constipation, bleeding — these are some of the ways your digestive system alerts you to a problem. And try as you may to ignore what’s happening (or isn’t happening) in your stomach or gut, doing so is virtually impossible.
For some people, the pain, bloating or nausea comes and goes. It may come on sporadically, and sometimes suddenly, and then gradually diminish after a few hours. For others, digestive distress persists and becomes a constant, unwanted companion.
Digestive issues have many possible causes, including infection, inflammation, digestive tract blockages, and lifestyle issues including diet and stress. For many individuals, no matter what they may try to relieve their signs and symptoms, it doesn’t work and the problem persists.
It’s estimated that 60 million to 70 million Americans — perhaps even more — experience some type of digestive issue. Evidence of this is on display in drugstore and grocery store aisles lined with an impressive array of digestive-related medicines and supplements, including antacids, acid blockers, laxatives and fiber supplements.
Over-the-counter medications often help relieve bothersome signs and symptoms, but they aren’t always the answer. If you’re regularly affected by periods of indigestion, pain, nausea or cramps, it’s important that you see your doctor.
Knowing the root cause of what’s ailing you can help reduce your anxiety, put you more at ease in social situations and allow you and your doctor to work together on a plan to manage the condition and possibly even cure it. Early action on your part may also prevent a serious digestive condition from becoming life-threatening.
• • • • •
Problems by the numbers
Are digestive problems more common today than they were years ago? The answer appears to be yes.
Why are digestive issues on the rise? There could be many reasons, and it’s difficult to point to one or two factors. However, there seems to be a legitimate association between digestion and lifestyle. Some of the increase in digestive-related issues could be linked to increasingly fast-paced lifestyles, unhealthy diets and reduced exercise.
The prevalence of digestive problems is reflected in these general statistics:
More than 60 million Americans experience heartburn at least once a month, and more than 15 million may have heartburn daily.
About 36 percent of Americans have trouble digesting dairy products, a condition called lactose intolerance.
An estimated 15 million Americans experience abdominal pain, gas, and diarrhea or constipation associated with irritable bowel syndrome.
More than 3 million clinic and hospital visits each year are for constipation.
Just under 6 percent of U.S. adults have ulcers.
About 3.5 million Americans are living with hepatitis C, a viral liver infection.
An estimated 135,000 Americans are diagnosed each year with colorectal cancer.
• • • • •
Digestion at work
Your digestive tract is a series of hollow, connected organs including the esophagus, stomach, small intestine and colon. Together they form a long, convoluted passageway extending from the mouth to the anus, where solid waste exits the body. Organs such as the salivary glands, pancreas, liver and gallbladder also serve essential functions in the digestive process.
Along this tract, muscular contractions move food along through successive stages of the digestive process. Valves at critical junctures control the amount of food that can be moved forward and prevent food from moving backward. A network of nerves and glandular cells regulates much of this activity, including the release of enzymes and digestive juices. When food is broken down, nutrients are absorbed into your blood via tiny pores in the intestinal wall. The nutrients are transported in the bloodstream to nourish your body’s cells.
When problems occur, certain signs and symptoms may point to any number of possible causes, making a diagnosis difficult (and your life miserable). The tasks at hand for you and your doctor during a medical visit are to identify all the possibilities and — often through a process of elimination — focus on the most likely cause.
In the sections that follow, we describe the different digestive organs and their relationships to one another. This knowledge may help you better understand the complexities of the digestive process and why problems develop.
Salivary glands
Digestion actually starts even before you take your first bite. The aroma of the food you’re about to eat — or are thinking about eating — is enough to get saliva in your mouth flowing. You have three pairs of large salivary glands, in addition to smaller glands in the lining of your mouth.
When you take a bite of food, your glands pump out saliva containing the enzyme amylase that begins to chemically break down the food. Your teeth crunch and grind the food, while your tongue mixes it with the saliva. These actions transform a bite of food into a bolus — a soft, moist, rounded mixture suitable for swallowing.
You control many aspects of the digestive process at the beginning — what you put into your mouth, how long you chew it and when you swallow. But once you swallow, the rest of the digestive process is controlled by your nervous system.
The digestive tract begins at the mouth and ends at the rectum and includes several internal organs. Food moves through your body along the digestive tract.
Esophagus
When you swallow, muscles in your mouth and throat propel food through a relaxed ring of muscle (upper esophageal sphincter) that connects the back of your throat (pharynx) to your upper esophagus. The esophagus, commonly referred to as the food pipe, is a tube about 10 inches long that connects your throat and stomach.
Gravity alone isn’t sufficient to move food through the esophagus. Help comes from muscles in the wall of the esophagus that move in synchronized waves — one after another — propelling the food toward your stomach. Muscles above the swallowed food contract, squeezing it downward, while muscles below the food relax to allow it to advance without resistance. This pattern of progressive contraction and relaxation is called peristalsis. Peristalsis is a coordinated muscular action that continues through your entire digestive tract.
As food reaches the lower portion of your esophagus, it approaches the lower esophageal sphincter (LES). When you’re not eating, this muscle valve remains tightly closed to keep stomach acid from flowing backward (regurgitating) into your esophagus and causing heartburn. The act of swallowing signals the valve to relax and open in order to let food pass through on its way to your stomach.
In some people, food doesn’t move down the tract as it should or the LES doesn’t relax, resulting in swallowing difficulties (dysphagia). Dysphagia most often occurs because the esophagus has become narrowed, often due to excessive acid exposure. Narrowing of the esophagus is known as a stricture.
Stomach
Your stomach sits in the upper area of your abdomen, just under your rib cage. A hollow, muscular sac, the typical stomach can expand to hold about a gallon of food and liquid. When your stomach is empty, its tissues fold in on themselves, a bit like a closed accordion. As your stomach fills, the folds disappear.
Your stomach performs two functions in the digestive process. It continues to break food down into smaller pieces, and it acts as a storehouse, gradually releasing food into the small intestine — where most chemical digestion and absorption take place.
Generally, it takes your stomach about four hours to empty after a nutritious meal. It may take six hours or more if the meal has a lot of fat.
Even before food arrives, digestive juices in the stomach begin flowing. At the first sight, smell and taste of food, your brain sends messages along the vagus nerve indicating that food will be arriving soon. The messages trigger the release of a chemical called acetylcholine along the nerves and muscles lining the stomach. This chemical sets off a chain reaction that causes your stomach muscles to start contracting and signals your gastric glands to produce digestive juices.
• • • • •
Appetite, hunger and feeling full
Appetite is that pleasant feeling that lets you know it’s time to eat. Hunger comes later, perhaps when you’ve gone past your normal mealtime and your body tells you so with unpleasant hunger pangs. Appetite and hunger work together to keep you eating regularly.
Your sensations of appetite and hunger are controlled by a part of your brain called the hypothalamus. A portion of the food you eat is converted into blood sugar (glucose). When your blood sugar level drops, the hypothalamus notices and sends nerve impulses along the vagus nerve to your stomach. These impulses trigger the release of gastric juices and set in motion the muscle contractions that produce hunger pangs. You may hear your stomach rumbling as juices and air pass through your intestines. This rumbling sound is normal.
If you aren’t able to eat right away, these sensations gradually wear off and you may not feel hungry again for several hours. But later in the day, when it’s time for your next meal, you may feel famished.
Once you’ve eaten, your brain recognizes when you’re full. As your stomach fills and stretches to its normal capacity, it signals that your hunger has been satisfied (satiety).
• • • • •
By the time food arrives from your esophagus, conditions are ready for the next stage of digestion. The muscles in your upper stomach relax to allow food and liquid to enter. The stomach walls, which are lined with three layers of powerful muscles, then begin churning the food, mixing it into smaller and smaller pieces. Gastric juices released from glands lining the walls of your stomach help break down food into a thick, creamy fluid called chyme. In a normal day, your stomach produces 2 to 3 quarts of gastric juices.
Hydrochloric acid is one of many kinds of gastric juices. This acid would be very corrosive in your stomach if it weren’t for a layer of sticky mucus that acts as a protective force clinging to your stomach walls. Hydrochloric acid kills harmful bacteria and microorganisms swallowed with the food. Gastric juices also contain pepsin, a protein-digesting enzyme. An imbalance in protective forces and damaging forces in the stomach lining can damage the lining, resulting in conditions such as erosion or an ulcer.
Two products that are absorbed directly into your bloodstream from your stomach are aspirin and alcohol, both of which pass quickly through the stomach lining with little trouble.
Once your food is well mixed, rippling waves of muscles in your stomach walls push the stomach contents down toward the pyloric valve, which opens into your small intestine. The pyloric valve, another ringlike sphincter muscle, opens just enough to allow your stomach to release less than an eighth of an ounce of food at a time into the small intestine. The rest of the contents is held back for more mixing.
Small intestine, pancreas, liver and gallbladder
The small intestine is a winding tube about 20 feet long that fills much of your abdomen. It’s here that the chemical breakdown of the food you eat is completed, and where most nutrients are absorbed into your bloodstream. The small intestine is divided into three parts: duodenum, jejunum and ileum (see this illustration).
Duodenum Food released from your stomach passes into the duodenum. This is the location where the chemical breakdown of food is the most intensive. Here, digestive juices converge from the pancreas, liver and gallbladder and mix with juices secreted from the walls of the small intestine to carry out the breakdown.
The lining of the duodenum contains enzymes — for example, lactase — that can break down simple sugars, such as lactose, into double sugars, such as glucose and galactose. The duodenum, however, absorbs only small amounts of nutrients through its intestinal walls. Muscular contractions continue moving food waste through the digestive tract.
Pancreas The pancreas is a soft, pink-colored gland that’s located behind the stomach. The pancreas is shaped a bit like a fish, with a wide head, a tapering body and a narrow tail.
In addition to other secretions, the pancreas produces two important types of digestive substances. They are:
Digestive enzymes that are secreted into your upper duodenum and help break down your main energy sources — proteins, carbohydrates and fats
The hormones insulin and glucagon, which are secreted into your bloodstream and help regulate your metabolism, including levels of blood sugar (glucose)
Liver The liver is a large organ located just under your rib cage on the right side of your abdomen. It’s a virtual chemical factory that performs hundreds of functions. Those functions include storing the nutrients from digested food, as well as filtering and processing potentially toxic substances you consume, such as alcohol, chemicals and most medications.
The liver also produces bile, a yellowish-green solution that helps break down fat so that it can be absorbed into your blood. Bile is what gives your stools their brown, green or yellowish color. This variation in color is normal. Stools that appear red or black, however, may indicate bleeding within the digestive tract.
Gallbladder Your gallbladder is a small, translucent sac that lies adjacent to your liver. The organ is a key part of the biliary tract, a system for transporting bile to the small intestine. The gallbladder functions as a reservoir for bile produced in your liver before the fluid drains into the duodenum.
Bile is produced continuously in your liver, even when your body isn’t digesting food. Excess bile is turned into a more concentrated, potent solution in the gallbladder when some of the water that makes up bile is absorbed. When food passes into your duodenum, a hormone signals the gallbladder to release its stored bile.
Jejunum and ileum The middle section of the small intestine is called the jejunum. It is within this middle section where many nutrients are absorbed from food and pass into your bloodstream.
The final section of the small intestine is called the ileum. The primary duty of the ileum is to absorb remaining nutrients from food waste. Absorption of vitamin B-12, an essential vitamin, occurs in the last few feet of the ileum, called the terminal ileum. Bile acids also are absorbed in the terminal ileum. When bile acids aren’t removed, they pass into the large intestine and may cause diarrhea.
The jejunum and ileum contain a variety of bacteria that aid in food digestion and nutrient absorption. Researchers are finding that a healthy balance of bacteria is beneficial not only to good digestion but also to your health in general (see Chapter 2).
The journey of food through the small intestine generally takes between 30 minutes and three hours, depending on the composition of your meal.
Colon
The colon is also known as the large intestine. Its job is to store and remove all food waste that your body can’t digest.
The colon is shorter than the small intestine but its diameter is greater and almost completely frames your small intestine. There are four sections of the colon: ascending, transverse, descending and sigmoid.
Food enters your colon through what’s known as the ileocecal valve, located at the end of your small intestine. This muscular valve prevents food waste from returning to the ileum. By the time food waste reaches the colon, your body has absorbed nearly all of the nutrients it can.
What remains are water, electrolytes such as sodium and chloride, and waste products such as plant fiber, bacteria and dead cells shed from the lining of your digestive tract.
During the time that food waste passes through your colon, your body absorbs nearly all of the water from the waste. The remaining residue (stool) is usually soft but formed. It’s also loaded with bacteria, which are useful to your body as long as your colon wall remains intact.
These bacteria cause certain food products to ferment, producing gas. This gas (flatus) is mainly an odorless mixture. The odors come from certain foods, especially those rich in sulfur, such as garlic and cabbage, or those with sulfur-based preservatives, such as bread, beer and potato chips.
As the food residue moves through your colon, muscle contractions separate and condense the waste into smaller segments. After each meal, considerable movement takes place in the