How Are CSID, IBS, and IBD Different?

How Are CSID, IBS, and IBD Different?

When you have stomach discomfort, it’s hard to know which gut-health condition is causing you grief. Sucrose intolerance, also called congenital sucrase-isomaltase deficiency (CSID), irritable bowel syndrome (IBS), and inflammatory bowel disease (IBD) all have similar symptoms like bloating, cramping, abdominal pain, nausea, diarrhea, and constipation. As a result, they are often misdiagnosed.

Here is an overview of the key differences between these diseases and the tests doctors use to assist in diagnosis.

Sucrose Intolerance

Definition: Sucrose intolerance, clinically referred to as congenital sucrase-isomaltase deficiency (CSID), is a rare disorder of the small intestine that affects a person’s ability to break down sucrose (sugar) into glucose and fructose because of the absence or low levels of two digestive enzymes: sucrase and isomaltase. Glucose and fructose are the forms of sugar that the body uses for fuel.

Cause: A life-long condition, it is caused by one of several known genetic mutations that can be passed down in families.

Symptoms: The common symptoms of sucrose intolerance — bloating, gas, diarrhea, and stomach pain — occur only after sugar or starch are eaten.

Tests That Aid in Diagnosis: Doctors use several tests to aid in a diagnosis. The gold standard, the disaccharidase enzyme test, involves an upper endoscopy procedure to obtain a biopsy of the small intestine to analyze in a lab. Other tests that assist in diagnosis include:

  • Sucrose Hydrogen Breath Test
  • 13C-Sucrose Breath Test
  • 4-4-4 Simple Oral Sugar Challenge

Do certain foods cause you to experience gas, bloating, and chronic diarrhea?

Irritable Bowel Syndrome (IBS)

Definition: IBS is a disorder of the large intestine. The symptoms of IBS can be painful, but the syndrome does not damage the digestive tract or cause other health issues.

Cause: IBS is caused by a functional problem with how your gut and your brain work together, increasing your sensitivity to food and changing how your bowel functions. Researchers suspect multiple factors are involved, including food sensitivities, stress, hormones, small intestinal bacterial overgrowth (SIBO), mental disorders (anxiety and depression), and gut bacteria imbalances.

Symptoms: The most common symptoms of IBS are diarrhea, constipation, gas, and bloating. Three symptoms that set IBS apart from other diseases are (1) changes in bowel movements, including changes in frequency or pain that get better or worse after movements; (2) changes in stool appearance; and (3) whitish mucus in the stool.

Tests That Aid in Diagnosis: No specific test is available beyond reviewing your symptoms. Your doctor may order blood, stool, or other tests to rule out other health problems.

Inflammatory Bowel Disease (IBD)

Definition: IBD is a group of chronic inflammatory diseases that involve the digestive tract. The most common types of IBD are Crohn’s disease and ulcerative colitis.

Cause: Researchers have identified dozens of genes, viruses, and some bacteria that are associated with Crohn’s disease and ulcerative colitis. For example, Crohn’s disease may be caused by an autoimmune reaction where the body over-reacts to bacteria, resulting in inflammation. 

Symptoms: Diarrhea, abdominal pain, and cramping are common symptoms. Symptoms unique to IBD include the following:

  • feeling tired
  • fever
  • blood in the stool
  • unintended weight loss
  • decreased appetite

Tests That Aid in Diagnosis: To diagnose IBD, doctors use a combination of tests that may include a physical exam, upper and lower endoscopy, colonoscopy, CT scan, an upper GI series, and a stool test.

If you are concerned you might have a digestive disorder, keep track of your symptoms. Consult with your family doctor and consider asking for a referral to a gastroenterologist, a doctor with additional training in digestive diseases. An accurate diagnosis is essential so that you can pursue the right treatment to have the best chance of managing your symptoms.


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Sucrose Intolerance May Be More Common Than You Think