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10 Stomach Symptoms You Should Never Ignore

They can signal cancer, COVID-19 or another serious disease

man holding his stomach in pain

Srdjan Radevic / EyeEm / Getty Images

En español |Everyone has stomach issues from time to time, and occasional digestive discomfort is not usually something to worry about. That said, doctors note that there are a few gastrointestinal symptoms that you shouldn’t write off, because they could signal something serious.

“I’ve seen many cases where patients have waited way too long before seeking medical attention,” says Christine Lee, M.D., a gastroenterologist at the Cleveland Clinic.

With studies showing that the coronavirus can cause gastrointestinal symptoms, patients have even more reason to take nausea, vomiting and prolonged diarrhea seriously, doctors say.

Here are 10 symptoms you should never ignore and what they may mean.

1. Prolonged diarrhea (especially if paired with fever, cough or loss of taste and smell) 

Diarrhea and other gastrointestinal symptoms can be among the first signs of COVID-19 infection, appearing before more well-known symptoms such as cough or fever, says Brennan Spiegel, M.D., director of health services research for Cedars-Sinai Medical Center in Los Angeles.

“Don’t wait for a cough or shortness of breath to get tested for COVID” if you have diarrhea, nausea/vomiting or abdominal pain that lasts more than a day, Spiegel says.

Studies show that as many as half of COVID-19 patients have gastrointestinal symptoms, and about 15 to 20 percent have only gastrointestinal symptoms. Diarrhea is the most frequently reported GI symptom, followed by nausea/vomiting and abdominal pain. People who test positive for the omicron variant also report diarrhea as a symptom, according to the ZOE COVID Study app.

Spiegel’s research found that COVID-19 patients with diarrhea typically have four to five bouts a day.

“One bout of diarrhea may not mean anything,” Spiegel says. “But if you’re having three or four per day and it is going on two days and you have no history of diarrhea, it’s a good idea to talk to your doctor, whether we’re in a pandemic or not.”

If it’s not COVID-19, prolonged diarrhea could signal another type of infection or an underlying condition like ulcerative colitis or irritable bowel syndrome.

2. Blood in your stool

Whether it's bright red, maroon or black, seeing blood in the toilet can be frightening. Fortunately, it's usually not life-threatening, says Nicholas E. Anthony, M.D., a gastroenterologist at Atrium Health in Charlotte, North Carolina. The most common causes are hemorrhoids and anal fissures (tears in the lining of the anus). But blood in your stool can also be one of the first symptoms of colon cancer, especially if it's accompanied by a change in your bowel habits or the shape of your stool. Since colon cancer is more common among those over age 50, it's especially important for older adults to see a doctor without delay. Other possible causes of bleeding are colon polyps, inflammatory bowel disease, colitis and diverticulosis.

3. Severe cramps after eating 

Severe cramping is a warning sign of a bowel obstruction — a serious condition that requires immediate medical treatment. It’s also a classic symptom of irritable bowel syndrome (IBS), a chronic digestion disorder that has been on the rise since the start of the COVID-19 pandemic. Experts aren’t sure how COVID-19 is linked to IBS, Spiegel says. It could be that the virus changes the gut microbiome or the lining of the intestinal system, triggering IBS. Or the boost in cases could be caused by pandemic-related stress and anxiety. Other IBS symptoms include abdominal pain (often related to bowel movements), bloating, gas, diarrhea or constipation. 

4. Difficulty swallowing

If you feel like your food is getting stuck in your throat or it hurts as it's going down, that can be a sign of something serious. “The big thing we worry about is esophageal cancer,” Anthony says. Esophageal cancer is more common in adults over 55 and three or four times more likely to occur in men than women, according to the Centers for Disease Control and Prevention. Other things that can cause discomfort when you swallow include an infection, an ulcer, a sore or scar tissue (which can develop if you have chronic acid reflux). In addition, a growing number of people are being diagnosed with eosinophilic esophagitis (EOE), a chronic allergic inflammatory disease that is a major cause of swallowing issues. To pinpoint the cause of your problem, your gastroenterologist will probably insert a tube with a camera attached to it down your throat in a procedure called an endoscopy.

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5. Unexplained weight loss (especially if accompanied by abdominal pain)

Weight loss when you haven't changed your diet or exercise habits is a common symptom of many serious illnesses, including cancer, Lee says. “Most people gain weight as they get older because their metabolism slows down,” she says. “If you're losing weight without much effort, that's a red flag.” See a doctor if you've dropped 5 percent or more of your body weight within six to 12 months. Although it is a symptom of some types of cancer, a 2014 study published in the journal American Family Physician found that in patients over 65, such weight loss is often due to other causes, like peptic ulcers, celiac disease, inflammatory bowel disease or an overactive thyroid.

6. Chronic or prolonged constipation (especially if you're having pain)

Almost everyone experiences occasional bouts of constipation, and studies show that it's especially prevalent among older adults. Constipation is typically defined as three or fewer bowel movements per week. It may not seem like a big deal, but if your constipation isn't treated, over time the stools in your colon can become so large and solid that your body can't remove them — and that can be painful or even deadly, Anthony warns. “If it goes longer than seven days, I want to see you,” he says. Constipation can be caused by a wide variety of issues, including certain medicines, a diet low in fiber, and medical conditions such as irritable bowel syndrome, thyroid issues, diabetes or, in rare cases, colorectal cancer.

7. Sudden, intense abdominal pain

A sharp pain that doesn't let up can indicate acute appendicitis (if it's on your lower right side), diverticulitis or a serious infection. The context is important, Lee says, because muscle cramps and other issues can also manifest as sharp pain. “If you're an athlete rock climbing and you get a sharp pain in your abdomen that only lasts a second, you probably just pulled a muscle,” she says. If it's something serious, she explains, usually the pain keeps escalating and doesn't let up.

8. Frequent, severe or worsening heartburn 

Occasional heartburn — a burning, uncomfortable sensation in your chest — is common among older adults and can usually be treated with over-the-counter medications. But if your heartburn is frequent and worsening, or if it’s not responding to medication, you may have gastroesophageal reflux disease (GERD), a disorder in which the valve between your stomach and esophogus doesn’t close properly. Left untreated, GERD can lead to complications including erosion or narrowing of the esophagus, or a precancerous condition called Barrett’s esophogus. In rare cases, severe heartburn can also indicate a more serious condition such as esophageal cancer or a hiatal hernia.

9. Swollen abdomen 

It’s not unusual to feel bloated after you eat a big meal. But there’s a difference between bloating and distension, an actual increase in measured abdominal size. “Do you literally see your belly puffing out? Is it bigger in circumference?” Spiegel asks. If the answer is yes — and the symptom persists after you’ve had plenty of time to digest a meal — it can be a sign that excess fluid or gas is forming in small intestines as the result of an obstruction, inflammation, bacterial overgrowth or a gastrointestinal disease.  

10. Feeling full after eating very little

If you feel stuffed even though you didn’t eat much, the most common cause is gastroparesis, a condition in which food stays in the stomach longer than it should. It can happen when a severe illness “stunts the electrical system of the stomach,” Anthony says, so gastroparesis can be a long-term side effect of COVID-19. Influenza, stomach surgery and diabetes can also trigger the condition. Although it can resolve on its own, your doctor can prescribe medications that will stimulate your stomach to contract and help speed digestion. If it’s not gastroparesis, other more serious causes of early satiety include an ulcer, an obstruction or a tumor.  

If you don't have one of the above symptoms, don't let that keep you from seeing a gastroenterologist if you suspect that something's wrong, Lee says. The earlier you detect a problem, the more options you have and the better your chances of success at managing it.

"The longer I do this, the more I realize that it doesn't matter what the textbook says — patients know their bodies,” Lee says. “If something is not normal for you, then it is a red flag, even if it's not on the list of top five. If something bothers you, you should get it checked out.”

Editor’s note: This story, published February 11, 2020, was updated to include additional symptoms as well as long-term side effects related to COVID-19.

Michelle Crouch is a contributing writer who has covered health and personal finance for some of the nation's top consumer publications. Her work has appeared in Reader's Digest, Real Simple, Prevention, The Washington Post and The New York Times.