The Connection between IBS and other Bowel Diseases

Written by: Truc Thanh | Last reviewed: June 2016. | Last updated: September 2019

What are other bowel diseases that may be related to IBS?

Symptoms of IBS may be misdiagnosed as symptoms of other bowel diseases. Distinguishing a disease or condition from a different disease that may share similar symptoms is called “differential diagnosis”. Some possible differential diagnoses of IBS symptoms are described below. Red flags for these diseases may include anemia, rectal bleeding, nocturnal symptoms, weight loss, recent antibiotic use, and onset after 50 years of age.1

Bile acid malabsorption (BAM)

Bile acids are produced in the liver and normally about 3%-5% reach the colon to be excreted from the body. In BAM, there is a defect in the system, which causes an increase of bile acids to reach the colon. The bile acids stimulate colonic contractions, leading to chronic watery diarrhea, bloating, and fecal urgency. 2 BAM may present as IBS-D. It typically occurs in adults. More than 25% of people with IBS-D have BAM.3

Inflammatory bowel disease (IBD), such as Crohn's disease, ulcerative colitis

IBD is a chronic, relapsing, inflammatory disorder that affects the gastrointestinal tract. IBD includes Crohn’s Disease and ulcerative colitis.4 Characteristic symptoms of inflammatory bowel disease include diarrhea that has persisted for more than 2 weeks, rectal bleeding, inflammatory mass, weight loss, perianal disease, and fever.3

Colorectal cancer

Colorectal cancer is cancer that originates as a polyp on the inner wall of the colon or rectum, which are parts of the large intestine. Colorectal cancer is more commonly found in older patients who develop IBS-type symptoms for the first time. Some symptoms include passage of blood in the feces, unintended weight loss, pain, and anemia.3

Microcytic or microscopic colitis

Microcytic or microscopic colitis is a general term that includes a family of chronic inflammatory bowel diseases, including lymphocytic colitis and collagenous colitis.5 About 20% of unexplained diarrhea in patients over the age of 70 is because of microcytic colitis. However, microcytic colitis is most common in middle-aged females. Symptoms are typically painless, but include chronic watery diarrhea.3,5 It is believed to be secondary to an abnormal immune reaction that may be triggered by infections, drugs, autoimmunity and/or bile acids.5

Gastrointestinal infection, such as bacterial overgrowth

Small-intestinal bacterial overgrowth is a rare condition. It is more commonly found in patients with a primary or secondary motility disorder, have undergone some type of abdominal surgery, or have impaired immunity. Typical features include maldigestion and maladsorption. The most common symptoms of bacterial overgrowth are bloating and diarrhea, which overlap with symptoms of IBS.3


Diverticula are small bulges through the large intestines. These outward bulges can become inflamed or infected, causing a condition called diverticulitis. The most commons symptoms are left-sided abdominal pain, fever, and tender inflammatory mass in the left-lower quadrant. Symptoms are typically more episodic and acute (occurs abruptly and changes quickly) to subacute (longer duration than acute and less rapid change) during an episode. It is believed that left-sided and bilateral pain may increase the risk for IBS.3

Ovarian cancer

Ovarian cancer is cancer of the ovaries, which are part of the female reproductive system. Women over the age of 40 complaining of increased abdominal girth, bloating, urinary urgency and pelvic pain may be considered for a diagnosis of ovarian cancer.3

Chronic pancreatitis

The pancreas secretes enzymes that play a role in the digestion process. In chronic pancreatitis, the organ is inflamed and over time becomes damaged, impairing the ability to digest food. Most people with chronic pancreatitis experience upper abdominal pain, and other symptoms of chronic pancreatitis may include nausea, vomiting, diarrhea, weight loss, and light colored or oily stools. Chronic pancreatitis are usually caused by heavy alcohol use, cystic fibrosis, autoimmune conditions, a blockage in the pancreatic duct or common bile duct, or hereditary pancreatitis.6,7

Carcinoid syndrome

Carcinoid syndrome is caused by carcinoid tumors, a rare type of cancer that secretes various chemicals into the blood stream. Symptoms of carcinoid syndrome include flushing, abdominal cramps, and diarrhea. Carcinoid tumors occur most often in the gastrointestinal tract or lungs, and treatment involves treating the cancer, which may include surgery or chemotherapy.8

Other possible differential diagnoses of IBS symptoms:1

  • Drug use, such as opiate analgesics, calcium channel blockers, antidepressants
  • Hyperthyroidism
  • Hypothyroidism

By providing your email address, you are agreeing to our privacy policy.

More on this topic