Does IBS show on a CT scan?

Quick Answer

IBS symptoms are unlikely to show up on a CT scan. A CT scan takes images of your internal organs and tissues using X-rays, looking for abnormalities in their structure. IBS is a functional bowel disorder that does not cause structural changes to the colon that would be visible on imaging. However, a CT scan may be done to rule out other causes of IBS-like symptoms that could show up on a scan, like inflammatory bowel disease, colon cancer or ovarian cancer. Overall a CT scan is not a diagnostic test for IBS, but it may be used to exclude other conditions.

What is a CT Scan?

A CT or CAT scan stands for computed tomography. It is an imaging technique that uses X-rays and computers to take detailed pictures inside the body.

During the test, you will lie inside a large ring-like machine called a CT scanner. The scanner will rotate around your body and take images from different angles. The images are sent to a computer which processes them into cross-sectional views or “slices” of the inside of the body. These images provide more detail than a regular X-ray.

CT scans are painless and non-invasive. They are commonly used to diagnose and monitor many conditions, including:

  • Cancers
  • Heart disease
  • Lung disease
  • Abdominal disorders
  • Musculoskeletal disorders like arthritis
  • Spinal abnormalities
  • Brain disorders
  • Injuries from trauma

A CT scan can provide images of soft tissues, blood vessels, bones and organs. This allows your doctor to assess their structure and look for any abnormalities.

What is IBS?

IBS stands for irritable bowel syndrome. It is a common gastrointestinal disorder that affects the large intestine (colon). IBS causes chronic symptoms like:

  • Abdominal pain or cramping
  • Bloating and gas
  • Diarrhea
  • Constipation
  • Alternating diarrhea and constipation

These IBS symptoms can vary widely from person to person. They tend to come and go in episodes that may be triggered by stress, certain foods, hormonal changes or other factors.

The exact cause of IBS is unknown. It appears to involve several factors:

  • Increased reactivity and contractions of the intestines
  • Inflammation in the intestines
  • Altered gut bacteria
  • Communication problems between the brain and the digestive system

These factors can result in motility problems, more sensitive nerve endings in the colon and an imbalance of gut microbes. Together, this makes the GI tract hypersensitive and overreactive to stimuli in people with IBS.

Importantly, IBS does NOT cause permanent damage or changes to the structure of the large intestine. It is known as a functional bowel disorder, meaning the bowel does not work properly but its structure looks normal.

Can a CT Scan Detect IBS?

Because IBS does not cause visible damage or abnormalities in the colon, it will not show up on a CT scan.

A CT scan creates cross-sectional images of organs and tissues using X-rays. It can only detect anatomical or structural problems. It cannot detect functional issues with how the GI tract works.

The colon tissue of someone with IBS generally appears completely normal on a CT scan. Even during episodes of intense symptoms, a CT scan is unlikely to show any colon abnormalities specific to IBS.

What Will Show Up on a CT Scan for IBS?

A CT scan of the abdomen/pelvis done on someone with IBS will usually show completely normal intestinal anatomy. Potential findings include:

  • Normal colon structure and tissue
  • No inflammation, lesions, masses or strictures in the colon
  • Regular intestinal wall thickness
  • No obstructions in the bowel
  • Normal diameter of rectum and colon
  • No enlarged lymph nodes in the abdomen

The lack of structural abnormalities helps confirm the functional nature of IBS. It rules out inflammatory bowel diseases like Crohn’s disease or ulcerative colitis as the cause of symptoms.

That said, some non-specific findings MAY show up on a CT scan of an IBS patient and include:

  • Stool in the Colon – This can occur if imaging is done during constipation. It does not indicate a problem.
  • Gas Patterns – Intestinal gas may appear if there is excess gas production due to IBS. However, this is a non-specific finding.
  • Diverticula – Some patients, especially the elderly, may have small pouches in the colon called diverticula. These are common and generally harmless.

Overall, there will not be any colon abnormalities on the CT scan that are characteristic of IBS itself. The results should be within normal limits.

Why Do a CT Scan for IBS?

Since a CT scan cannot detect or diagnose IBS, why is it sometimes performed on IBS patients?

There are a few reasons a doctor may order a CT abdomen/pelvis for someone with possible IBS:

  1. Rule out structural causes – Although unlikely, a CT scan helps definitively rule out the possibility of an anatomic abnormality or obstruction causing symptoms.
  2. Exclude other conditions – Diseases like cancer, IBD and diverticulitis can mimic IBS symptoms. A CT scan can help exclude these as the cause.
  3. Evaluate severity – A CT scan may be done on severe or refractory IBS cases to help assess their extent and severity.
  4. Guide treatment – The CT findings may help guide management. For example, ruling out inflammation may indicate anti-inflammatory drugs are unnecessary.
  5. Check for complications – In long-standing IBS, a CT scan can check for any rare complications like bowel obstruction from severe constipation.

So in summary, a CT scan is not used to diagnose IBS itself. Rather, it is one tool that can help exclude certain diagnoses and complications that could explain chronic bowel symptoms incorrectly assumed to be IBS.

Specific Conditions a CT Scan Can Detect or Rule Out

Here is a list of some specific conditions that a CT abdomen/pelvis may be able to detect or exclude as the cause of symptoms mistakenly believed to be IBS:

1. Cancer

  • Colon cancer – CT can detect bowel wall thickening, lesions, masses and lymph node enlargement indicative of colorectal cancer.
  • Ovarian cancer – CT may reveal an ovarian mass or nodules concerning for ovarian cancer metastasis.
  • Other cancers – cancers of the pancreas, uterus, bladder, stomach may also appear on pelvic CT scans.

2. Inflammatory Bowel Diseases

  • Crohn’s disease – CT can show bowel wall thickening, narrowing, strictures, fistulas and abscesses pointing to possible Crohn’s.
  • Ulcerative colitis – Findings may include colon wall thickening and loss of normal contours.

3. Infections

  • Appendicitis – An inflamed, enlarged appendix may be visible.
  • Diverticulitis – Infected, inflamed diverticula in the colon may appear.
  • Abscesses – Intra-abdominal abscess pockets could indicate infection.

4. Bowel obstructions

  • Foreign body obstructions
  • Twisted bowel (volvulus)
  • Hernias that trap intestines
  • Scarring (adhesions) from surgery
  • Strictures or narrowing of intestines

5. Other findings

  • Kidney stones
  • Enlarged organs like spleen or liver
  • Ovarian cysts
  • Uterine fibroids

So in patients with chronic diarrhea, constipation and abdominal pain, a CT scan can help identify or exclude many other possible causes that may be mistaken for IBS. This information then guides treatment and management decisions.

Are there Alternatives to a CT Scan for IBS?

For evaluating IBS, there are a few imaging and endoscopic alternatives to a CT scan. These include:

  • Colonoscopy – This endoscopic test allows direct visualization of the colon lining. Biopsies can be taken. It is considered more sensitive than CT scan for detecting subtle mucosal inflammation or cancers.
  • Flexible sigmoidoscopy – The sigmoid colon can be viewed with this shorter endoscopic procedure.
  • Capsule endoscopy – You swallow a small capsule camera that takes images of the entire GI tract.
  • MRI – Magnetic resonance imaging provides detailed images of soft tissues similar to CT scan.
  • Ultrasound – Ultrasound uses soundwaves to image organs and reveal masses, cysts, stones, etc. It does not visualize the colon well.
  • Barium X-ray – These special X-rays of the abdomen and colon use contrast material to show the intestinal lumen.

Each test has its own pros and cons. colonoscopy allows biopsy samples to be taken and has better sensitivity for subtle findings. However, CT scanning is non-invasive, readily available, and will scan the entire abdomen/pelvis for disease. Your doctor will select the most appropriate studies based on your symptoms, risk factors and need for biopsy specimens.


IBS is a functional bowel disorder that does not cause visible abnormalities or damage to colon tissue detectable by a CT scan. The colon will generally appear entirely normal on a CT scan of a patient with IBS.

However, CT scans are still useful for ruling out certain structural and inflammatory conditions that can mimic IBS, like cancer, IBD and diverticulitis. A CT scan may show findings that point to an alternate diagnosis and allow proper treatment.

While a CT scan cannot confirm an IBS diagnosis, it can provide valuable information that excludes other causes of your symptoms. This helps guide management as a process of elimination. Your doctor may order a CT as one of several tests to evaluate chronic bowel problems attributed to IBS.

Leave a Comment