By Brittany Poulson, MDA, RDN, CD, CDCES 

 Medically reviewed by Sonal Kumar, MD

The digestive system includes the gastrointestinal (GI) tract that runs from the mouth to the anus, the liver, pancreas, and gallbladder. These organs work together to digest (break down) food into individual nutrients to be used throughout the body for energy, growth, and cell repair.

A digestive disease disrupts digestion in one way or another, causing health problems that range from mild to serious. This may include something as common as acid reflux to celiac disease or cancer. 

This article discusses common diseases of the GI tract and when they might be considered serious. It reviews the risks of an untreated digestive condition and what to eat if you have a digestive problem.

Types of Digestive System Diseases

Many different diseases affect the digestive tract. Some conditions are acute (coming on suddenly and lasting only a short time), while others are chronic (lasting a long time). Symptoms may vary from day to day or come and go.

Being aware of your symptoms, when they occur, for how long, and if they are more severe after eating certain foods or performing certain activities can help in identifying the correct cause of your digestive issues.

Gastroenteritis

Gastroenteritis, commonly called the stomach flu, is not influenza but an infection of your gastrointestinal tract caused by viruses, bacteria, parasites, or chemicals. Gastroenteritis caused by a virus is called viral gastroenteritis.1

Many viruses can be spread from person to person and cause infections. Some common viruses that can cause gastroenteritis include norovirus, rotavirus, adenovirus, and astrovirus. 

Symptoms of gastroenteritis usually include:  

• Diarrhea

• Abdominal pain or cramping

• Nausea

• Vomiting

• Fever

• Fatigue

Viral gastroenteritis tends to be acute, usually lasting less than a week. Most people get better on their own without medical treatment. However, more serious cases can lead to dehydration and may require medical treatment.

Gastroenteritis in Children

Rotavirus, adenovirus, and astrovirus most often infect infants and young children, but they can also infect adults. Norovirus can cause infections in people of all ages. Diarrhea is especially dangerous in newborns and infants, leading to severe dehydration in just a day or two, and can be life-threatening.2

Seek medical attention immediately if an infant or child has signs or symptoms of dehydration, such as:

• Being thirsty more than usual

• Urinating less than usual, or no wet diapers for three hours or more

• Lack of energy

• Dry mouth

• No tears when crying

• Decreased skin elasticity

• Sunken eyes or cheeks

Celiac Disease

Celiac disease is a chronic digestive autoimmune disorder that causes damage to the small intestine. In this condition, the immune system reacts to gluten consumed in foods or beverages. Gluten is a protein found naturally in wheat, barley, and rye. It is commonly found in foods such as bread, pasta, cookies, and cakes but can also be found in other foods, beverages, and products.

The main treatment for celiac disease is following a gluten-free diet. Learning to read ingredient lists, as well as knowing the different grains and food products that contain gluten, is important to help in staying gluten-free and preventing damage to the small intestine.

Symptoms of celiac disease may include:

• Abdominal bloating

• Abdominal pain or cramping

• Diarrhea

• Constipation

• Gas

• Nausea or vomiting

• Lactose intolerance due to damage to the small intestine

• Greasy, foul-smelling stools

Research suggests that celiac disease occurs in people who have certain genes.3 A person is more likely to develop celiac disease if a family member also has the condition. In the United States, celiac disease is more commonly diagnosed among White people compared to other racial or ethnic groups. Celiac disease is more common in females than in males.4

(Note that when research or health authorities are cited, the terms for sex or gender from the source are used.)

Constipation and Diarrhea

Constipation and diarrhea are common GI issues. Both are often symptoms of other digestive system problems and can greatly impact quality of life.

Constipation is a condition in which bowel movements are reduced, and you have fewer than three a week. Other symptoms include hard, dry, or lumpy stools that are difficult or painful to pass or a feeling that all the stool has passed.

Causes of constipation include certain medical conditions (especially those that affect the digestive system), changes in physical activity or diet, pregnancy, side effects of medications, and more.5

Constipation in Children

Constipation is common in children. Constipation is the cause of almost 1 in every 20 childhood visits to a healthcare provider.6 In most cases, constipation in children lasts a short time and is not dangerous.

Symptoms of constipation in children include the same symptoms listed previously, as well as:

• Abdominal bloating

• Daytime or nighttime wetting

• Stool in their underwear that looks like diarrhea

• Changing positions to avoid or delay having a bowel movement, including standing on tiptoes and then rocking back on their heels, clenching buttocks, random dance-like movements

Diarrhea is the opposite problem, in which you have more frequent stools, occurring three or more times a day. Stools may be loose and watery.

Causes of diarrhea include digestive tract problems, food allergies and food intolerances, infections, and side effects of medicines.7

Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a chronic condition that affects the large intestine (colon). In the United States, it’s estimated that about 12% of people have IBS.8

IBS comprises a group of symptoms that occur together, including:

• Abdominal pain and cramping

• Abdominal bloating

• Gas

• Diarrhea 

• Constipation

The three subtypes of IBS, depending on the dominant symptom, are: 

• IBS with constipation (IBS-C)

• IBS with diarrhea (IBS-D)

• IBS with mixed bowel habits (IBS-M)

With IBS, symptoms occur without any visible signs of physical damage or disease in the digestive tract. However, symptoms can still greatly impact quality of life.

Conditions Overlapping With IBS

It’s estimated that at least half of people with IBS have at least one comorbid condition (those occurring at the same time).9

Researchers think there is overlap because the causes of these diseases and conditions are similar. Advocating for yourself to receive a proper diagnosis of the condition(s) you have will prove to be very beneficial in the treatment and management of symptoms.

Conditions that might overlap with IBS include:

• Dyspepsia (chronic indigestion or upset stomach)

• Heartburn

• Celiac disease

• Inflammatory bowel disease (IBD)

• Fibromyalgia (chronic pain disorder)

• Interstitial cystitis (group of diseases causing scarring of the lungs)

• Migraine headaches

• Chronic pelvic pain

• Temporomandibular joint disorder (TMD) (group of conditions causing jaw pain and dysfunction)

• Chronic fatigue syndrome (myalgic encephalomyelitis)

• Anxiety and depression

• Endometriosis10 (cells similar to those lining the uterus grow outside the uterus)

Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) includes conditions in which there is chronic inflammation of the GI tract. The two main conditions in IBD are Crohn’s disease and ulcerative colitis (UC).11

The exact cause of IBD is unknown, but researchers think it is the result of genetics and a dysregulated immune system. A dysregulated immune system causes an imbalance among the inflammatory cytokines (inflammatory protein seen in the inflammatory process).12

Crohn’s disease can affect any part of the digestive tract, whereas UC only affects the large intestine and the rectum. Both can cause damage to the lining of the digestive tract. However, in Crohn’s disease, the damaged areas are usually patchy, and in UC the damage is continuous.

Symptoms of IBD include:

• Abdominal pain

• Chronic diarrhea

• Blood in the stool

• Mucus in the stool

• Stool urgency

• Unintentional weight loss

• Fatigue

Colitis

Colitis is inflammation of the colon. Sometimes the cause is unknown, or it may be caused by viral and bacterial infections, medications, Crohn's disease, UC, lack of blood flow, pseudomembranous colitis (bacteria causing inflammation of the colon), or necrotizing enterocolitis (serious intestinal disease) in newborns.13

There are different types of colitis, including Inflammatory (such as in IBD), microscopic (causes chronic watery diarrhea), pseudomembranous (colon inflammation caused by bacterial overgrowth), ischemic (blood flow is restricted or reduced), and allergic colitis (which usually occurs in infants). 

Symptoms of colitis include: 

• Abdominal pain

• Abdominal bloating

• Dark stools, or blood in the stool 

• Continual feeling of needing to have a bowel movement (tenesmus)

• Dehydration

• Diarrhea

• Fever

Diverticular Disease

Diverticular disease includes two conditions—diverticulosis and diverticulitis. Diverticulosis is when small pouches, called diverticula, form in weak spots along the wall of the colon. Usually, the diverticula do not cause symptoms. Diverticula can bleed in some people and cause hematochezia (bright red blood passing through the rectum). And sometimes, the diverticula can become inflamed/infected (diverticulitis).

Symptoms of diverticulitis include:

• Abdominal pain (most commonly in the lower left side)

• Nausea

• Vomiting

• Constipation

• Diarrhea

• Fevers and chills

Diverticulosis is a fairly common condition in the United States. It’s estimated that over 30% of adults between the ages of 50 and 59 and over 70% of those 80 and older have it. However, less than 5% of people with diverticulosis go on to develop the more complicated diverticulitis.14

Acid Reflux

Acid reflux is a common term for gastroesophageal reflux (GER). GER is sometimes called heartburn, reflux, acid indigestion, and acid regurgitation.

GER happens when the stomach contents come back up into your esophagus (food pipe). Many people experience GER now and then. It can occur without causing any symptoms, or, in some cases, it can cause indigestion or a mild burning sensation in the chest.15

Gastroesophageal reflux disease (GERD) is when GER symptoms become more chronic and severe. In the United States, about 20% of people have GERD.15

Untreated GERD can cause more serious complications, such as:

• Esophagitis (inflammation of the esophagus)

• Esophageal stricture (when the esophagus becomes too narrow)

• Barrett’s esophagus (when the tissue of the esophagus becomes salmon colored as a result of changes in the lining of the esophagus cells to look like intestinal cells): Barrett's esophagus increases risk of esophageal cancer.

Symptoms of GERD may include:

• Heartburn or indigestion

• Chest pain

• Nausea

• Difficulty or pain when swallowing 

• Chronic cough

• Hoarseness of the voice

Rectal and Anal Problems

There are several conditions that can affect the rectum and anus, which are at the end of the digestive tract after the colon. These include:

• Anal fissure: This is a small rip or tear in the lining of the anal canal that connects the rectum to the anus. Symptoms include sharp pain from passing stool, bright red blood on the stool, and a small lump or skin tag near the rip or tear.16

• Anal fistula: This is an abnormal tunnel under the skin that connects the anal canal in the colon to an opening on the skin around the anus. Most anal fistulas are formed as a result of an anal gland that has become infected.17 Symptoms of anal fistulas include pain, redness, itching, and swelling of the anus. There may also be fever, chills, fatigue, and pus drainage.

• Hemorrhoids: Also called piles, hemorrhoids are inflamed and enlarged veins around the anus or lower rectum. Hemorrhoids may be external (on the skin around the anus) or internal (on the lining of the anus and lower rectum). Symptoms for external hemorrhoids include anal itching, hard, sensitive lumps near the anus, and pain near the anus when sitting. Internal hemorrhoids can cause rectal bleeding, and sometimes a prolapse (when a hemorrhoid has fallen through the anal opening). Prolapses may cause pain and discomfort.18

• Proctitis: Proctitis is inflammation of the lining of the rectum. There are different types of proctitis, including proctitis in IBD, infectious proctitis (occurring from certain infections, including some sexually transmitted infections (STIs), radiation proctitis (occurring after receiving radiation therapy in the pelvic area), and diversion proctitis (occurring after having a bowel diversion performed, also called an ostomy of the bowel).19 Symptoms of proctitis include tenesmus, diarrhea, constipation, pain in the anus, rectum, and lower abdomen, rectal bleeding, and passing mucus or pus with bowel movements.20

• Rectal prolapse: A rectal prolapse is a condition in which the rectum becomes stretched out and slides out, protruding from the anus. Women age 50 and older are 6 times more likely to have a rectal prolapse than men.21 Symptoms of rectal prolapse include rectal bleeding, tissue bulging from the rectum, and fecal incontinence (not being able to manage bowel movements).

Peptic Ulcers

A peptic ulcer, or stomach or duodenal ulcer, is a sore on the lining of your stomach or duodenum (the first part of the small intestine). It is sometimes called peptic ulcer disease. In the United States, it’s estimated that 1% to 6% of people have peptic ulcers.22

Peptic ulcers can lead to bleeding in the digestive tract, a hole in the wall of the stomach or duodenum, ulcers in nearby organs, and blockage that stops food from moving into the duodenum. Two common causes of peptic ulcers include an infection with Helicobacter pylori (H. pylori) bacteria and high doses or chronic use of nonsteroidal anti-inflammatory drugs (NSAIDs), such as Advil or Motrin (ibuprofen) and Aleve (naproxen).23

Symptoms of a peptic ulcer include: 

• Abdominal pain or discomfort in the upper part of the abdomen

• Feeling full soon after starting a meal or overfull after eating a normal-sized meal

• Indigestion

• Nausea

• Vomiting

• Abdominal bloating

• Belching

• Passing black or tarry stool

• Vomiting blood

Colon Polyps and Cancer

Colon polyps are growths on the lining of the colon and rectum. Most polyps are not harmful or cancerous, but some may develop into cancer over time. This is why colonoscopies are so important. Removing polyps can help prevent colorectal cancer.

Most often, there are no symptoms of colon polyps. If a colon polyp is causing symptoms, they may include:

• Rectal bleeding

• Dark-colored stools or blood in the stool

• Fatigue due to anemia (a low number of healthy red blood cells)

In the United States, it’s thought that between 15% and 40% of adults have colon polyps. Men and people aged 45 or older are more likely to have colon polyps.24 However, people with a strong family history of colon cancer in a parent or sibling or with hereditary polyposis syndrome (inherited condition marked by an increased risk of developing polyps) may require colonoscopy at an earlier age and more frequently.

Pancreatitis

Pancreatitis is inflammation of the pancreas. The pancreas secretes digestive enzymes into the small intestine. It also produces the hormones insulin and glucagon that regulate sugar metabolism.

Common causes of acute pancreatitis include gallstones and chronic alcohol consumption. Other causes include medications, infections, trauma, tumors, and more.25

Symptoms of acute pancreatitis commonly include upper abdominal pain, which can be sudden and severe. They are likely to need emergency medical attention. Other symptoms can include:26

• Abdominal swelling and tenderness

• Nausea

• Vomiting

• Fever

• Rapid heart rate

When Is a Digestive System Disease Serious?

Common digestive problems, such as constipation, diarrhea, and heartburn, are issues that many people experience every so often. These conditions often improve on their own or with over-the-counter (OTC) treatments.

However, if your symptoms get worse or don’t go away, it might be necessary to schedule an appointment with a healthcare provider. Depending on the severity of your condition, you may need a referral to see a specialist, such as a gastroenterologist who specializes in digestive health.

Seek medical treatment if you are experiencing any of the following:

• Ongoing or unusual abdominal pain, bloating, or gas

• Ongoing or severe heartburn

• Pain or difficulty when swallowing

• A feeling of food stuck in your esophagus

• Choking on food

• Continuous nausea or vomiting

• Chronic diarrhea

• Chronic constipation

• Unable to have complete bowel movements

• Black stools or blood in the stool

• Oily, greasy, or foul-smelling stool (steatorrhea)

• Loss of appetite

• Unintentional weight loss

• Extreme fatigue

• High Fever

Risks of Untreated Gut Problems 

Getting a proper diagnosis is the first step in figuring out your digestive issues. This will help you receive appropriate treatment, which is crucial to managing your symptoms and preventing complications. 

Untreated digestive issues may worsen symptoms, which can greatly impact your quality of life. Healthcare costs can also increase with more complicated conditions. Over time, untreated gut problems can lead to serious complications like dehydration, malnutrition, cancer, and even death. 

If you suspect you have a digestive disease, seek medical treatment as soon as possible. A healthcare provider can create a care plan best suited to treat your symptoms. Treatment may include medication, dietary supplements, dietary and lifestyle changes, surgical procedures, or psychological interventions such as cognitive behavioral therapy.

What to Eat If You Have a Digestive System Disease

Oftentimes when you have a disease of the digestive system, you will need to modify your diet. What you eat and what you avoid eating depend on which condition you have.

Discuss any modifications with a healthcare provider to ensure they are appropriate for your condition. Dietary modifications can vary greatly depending on the condition that is being treated.

For example, if you are diagnosed with celiac disease, you will need to avoid all foods and beverages containing gluten or that may have been cross-contaminated with gluten. Depending on the severity, you may even need to avoid some medications and other products that might contain gluten, such as toothpaste, makeup, lip balms, or lotions.

In severe cases of other digestive conditions, such as diverticulitis, you may need to restrict what you are eating to only clear liquids, then advance your diet to full liquids, before slowly adding in regular foods once symptoms have improved. 

A registered dietitian (RD) or registered dietitian nutritionist (RDN) specializing in digestive health can help you navigate what foods and beverages to consume and which might be triggers for you to avoid.

Summary

Diseases and conditions of the digestive tract include gastroenteritis, celiac disease, constipation, diarrhea, IBS, IBD, colitis, diverticular disease, acid reflux, pancreatitis, problems of the anus and rectum, colon polyps, and cancer.

If symptoms of a digestive condition worsen, last longer than usual, or new symptoms start to develop, this could be a sign of a more serious condition and the need for immediate medical attention.

If left untreated, digestive problems can lead to complications such as dehydration, malnutrition, cancer, or death. Knowing what to eat with a digestive condition will depend on the condition you have. Meeting with a dietitian specializing in digestive health can help you know what to eat to better manage your condition.

26 Sources

National Institute of Diabetes and Digestive and Kidney Diseases.  Definition & facts for viral gastroenteritis (“stomach flu”)

National Institute of Diabetes and Digestive and Kidney Diseases. Symptoms & causes of viral gastroenteritis (“stomach flu”).

National Institute of Diabetes and Digestive and Kidney Diseases. Symptoms & causes of celiac disease.

National Institute of Diabetes and Digestive and Kidney Diseases. Definition & facts for celiac disease.

National Institute of Diabetes and Digestive and Kidney Diseases. Symptoms & causes of constipation.

National Institute of Diabetes and Digestive and Kidney Diseases. Definition & facts for constipation in children.

National Institute of Diabetes and Digestive and Kidney Diseases. Symptoms & causes of diarrhea.

National Institute of Diabetes and Digestive and Kidney Diseases. Definition & facts for irritable bowel syndrome.

International Foundation for Gastrointestinal Disorders. Overlapping conditions with IBS.

International Foundation for Gastrointestinal Disorders. IBS in women.

National Institute of Diabetes and Digestive and Kidney Diseases. Definition & facts of microscopic colitis.

Centers for Disease Control and Prevention. What is IBD?

National Library of Medicine. Colitis.

National Institute of Diabetes and Digestive and Kidney Diseases. Definition & facts for diverticular disease.

National Institute of Diabetes and Digestive and Kidney Diseases. Definition & facts for GER & GERD.

American Society of Colon and Rectal Surgeons. Anal fissure.

Johns Hopkins Medicine. Anal fistula.

National Institute of Diabetes and Digestive and Kidney Diseases. Symptoms & causes of hemorrhoids.

National Institute of Diabetes and Digestive and Kidney Diseases. Definition & facts for proctitis.

National Institute of Diabetes and Digestive and Kidney Diseases. Symptoms & causes of proctitis.

American Society of Colon and Rectal Surgeons. Rectal prolapse.

National Institute of Diabetes and Digestive and Kidney Diseases. Definition & facts for peptic ulcers (stomach or duodenal ulcers).

National Institute of Diabetes and Digestive and Kidney Diseases. Symptoms & causes of peptic ulcers (stomach or duodenal ulcers).

National Institute of Diabetes and Digestive and Kidney Diseases. Definition & facts for colon polyps.

Krishna SG, Kamboj AK, Hart PA, Hinton A, Conwell DL. The changing epidemiology of acute pancreatitis hospitalizations: a decade of trends and the impact of chronic pancreatitis. Pancreas. 2017;46(4):482-488. doi:10.1097/MPA.0000000000000783

National Pancreas Foundation. Acute pancreatitis causes and symptoms.

By Brittany Poulson, MDA, RDN, CD, CDCES
Brittany Poulson, MDA, RDN, CDCES, is a registered dietitian and certified diabetes care and education specialist.