Step 1 - Consulting Your Physician
The first (and most important) step in the process is consulting your physician about the bowel symptoms you’re experiencing. From here, your provider will investigate your symptoms to help pin down a proper diagnosis and/or plan of action.
Step 2 - Providing A Detailed History
Your provider will ask for details about your clinical history and symptoms. Your history and symptoms form the foundation for a proper diagnosis, any further investigations, and referrals to appropriate specialists as needed.
What Background Information Does Your Doctor Need?
The diagnosis of IBS relies on the collection of information regarding the frequency, onset, and duration of your symptoms. IBS diagnostic questions will revolve around the presence of abdominal pain related to your bowel habits. Your physician will also collect information about your usual stool form using a visual aid called the Bristol Stool Form Scale. This information helps with subtyping IBS and/or identifying primary symptom complaints.
Mental Health Screening
Your physician may ask some routine screening questions to assess for symptoms of depression, anxiety, or other psychosocial challenges. Gut symptoms can be triggered by our mental and emotional experiences, and likewise, our gut symptoms may influence our mental health. This intricate feedback loop between gut and brain makes it essential to screen for these challenges, as appropriate treatment (and referrals to specialists as needed) may help to improve gut symptoms.
Diet
You may be asked to provide information about your diet history to see if something in your diet is triggering your symptoms. Diet triggers your physician or dietitian might pay close attention to include certain dairy products, wheat, caffeine, certain fruits and vegetables, high or low dietary fiber intake, juices, soft drinks, and chewing gum.
Medications & Supplements
Several medications and supplements may impact bowel symptoms. Your doctor will ask about all prescription and over-the-counter medications and supplements you’re taking.
Prior Medical Procedures & Tests
Your physician will ask about prior surgeries, procedures, and relevant diagnostic or laboratory tests.
Alarm Symptoms (Red Flags)
Alarm features may be helpful in ruling out other conditions which can present with IBS-like symptoms. Alarm symptoms you’ll be screened for include:
- Unintended weight loss of >10% in 3 months
- Blood in the stool not caused by hemorrhoids or anal fissures
- Fever
- A family history of colorectal cancer, inflammatory bowel disease, or celiac disease
- Symptom onset after age 50
- Nocturnal bowel movements
- Anemia
- Persistent, daily, watery diarrhea
- Recurrent vomiting
- Severe or progressively worsening symptoms
Other Supporting Information
Your physician may ask about common co-occurring symptoms, conditions, and relevant personal history that’s been associated with a diagnosis of IBS. For example, they may ask about current and early life psychological stressors, or history of prior gastrointestinal infection. While much of this information doesn’t constitute part of the IBS diagnostic criteria, these questions may be helpful to strengthen confidence in an IBS diagnosis and to generate a plan of action.
Bowel Symptom Diary
Type 1
Type 2
Type 3
Type 4
Type 5
Type 6
Type 7
Day 1
Day 2
Day 3
Day 4
Day 5
Day 6
Day 7
Day 8
Day 9
Day 10
Day 11
Day 12
Day 13
Day 14
Step 3 - Physical Examination
Your physician will conduct a thorough physical examination. The purpose of the exam is to screen for findings that may warrant additional investigations while also minimizing the use of unnecessary diagnostic tests. Your physician may look for abdominal tenderness, palpable masses, or distention. A physical examination also includes a digital anorectal exam. A digital exam will be used to investigate:
- The presence of hemorrhoids or anal fissures
- Anal strength particularly in patients with incontinence
- Muscular contraction patterns in the anorectum and pelvic floor muscles which may play a role in provoking bowel habit abnormalities
Step 4 - Limited Investigations As Needed
Depending on your presenting symptoms and personal medical circumstances, your physician may order medical tests to rule out other conditions that can present with symptoms resembling IBS.
It’s important to note that there are no consistently reliable tests for IBS, and the complexity of the disorder makes it unlikely that a singular biomarker test would be able to identify IBS in all cases. 1Also, no disease masquerades as IBS with enough frequency to make testing for that condition feasible in all cases and IBS subtypes.
Many falsely believe that IBS is a diagnosis of exclusion where extensive testing should be carried out to screen for other diseases before a diagnosis is made. But in reality, the use of excessive testing has not been shown to improve patient satisfaction or diagnostic and treatment outcomes. Testing in excess of what’s medically indicated can be costly, invasive, and delay diagnosis and treatment1.
It’s important to know that the absence of hard medical tests and indicators for illness does not equate to a lack of illness. In the case of IBS and other functional bowel disorders (FBDs), the symptom experience *is* the final determining “test” for diagnosis.
Key Takeaways
- Diagnosing IBS is not foolproof, requires a physician, and boils down to 4 key steps.
- Step 1 involves contacting your physician for an evaluation.
- Step 2 is to review all pertinent medical history with your physician. This includes things like symptoms, diet, mental health screenings, medications, alarm symptoms, etc.
- Step 3 requires a physical exam by your doctor
- Step 4 occurs in the case of your doctor requesting additional testing to confirm a medical diagnosis.
- When it comes to testing in IBS, there are no biomarkers that consistently diagnose all forms of IBS. Testing done in IBS is usually done to exclude other possible diseases that present with similar symptoms experienced in IBS.
Diagnosing IBS vs Other Bowel Disorders
Types Of Bowel Disorders
Functional bowel disorders – the category under which IBS falls – are 1 of the 3 major clinical diagnostic categories in the field of gastroenterology. The 3 main categories are described in the table below and include:
- Organic Gastrointestinal (GI) disorders
- Motility disorders
- Functional GI disorders
It’s important to note that overlap can be seen between these three diagnostic domains. What distinguishes the disorders are their defining criteria. For instance, motility disturbances may also be present in IBS, but this is not a defining criterion for IBS to be diagnosed.
Functional bowel disorders are unique in that they are diagnosed primarily from a determined cluster of symptoms that come together to form a clinical diagnosis.
- Tied to structural changes in the GI tract (organ morphology)
- Measured by:
- Tissue analysis (Histology/Pathology)
- Scoping views of the impacted organ (endoscopy)
- Imaging technology (radiology)
- Examples:
- Esophagitis
- Peptic Ulcer
- Inflammatory Bowel Disease (IBD)
- Colon Cancer
- Tied to recurrent problems with GI motility
- Measured by:
- Motility tests, Visceral sensitivity
- Example:
- Gastroparesis (delayed stomach emptying)
- Also called disorders of gut-brain interaction
- Measured by:
- Symptom criteria, motility, psychosocial factors, visceral sensitivity
- Examples:
- IBS
- Functional Constipation
Diagnostic Criteria For IBS & Other Functional Bowel Disorders
The cluster of symptoms used for the diagnosis of IBS and other functional bowel disorders are defined by the Rome Foundation. The Rome Foundation is a multinational organization that brought together hundreds of clinicians and investigators to produce diagnostic criteria, guidelines, and recommendations for the field of gastroenterology2.
The Rome criteria have been published in a series of 4 publications (I, II, III, and IV) with Rome IV being the most current version published in 2016. At present, Rome criteria are the only criteria accepted by regulatory agencies (including the FDA), most academic investigators, and pharmaceutical companies. 3All outlined diagnostic criteria herein for IBS and other FBDs have been sourced from the latest Rome IV publication.
Rome IV Diagnostic Criteria For IBS
Recurrent abdominal pain on average at least 1 day/week in the last 3 months, associated with 2 or more of the following criteria:
- Related to defecation
- Associated with a change in frequency of stool
- Associated with a change in form (appearance) of stool
*Criteria fulfilled for the last 3 months with symptom onset at least 6 months prior to diagnosis4.
Honing The IBS Diagnosis - IBS Subtypes
IBS is broken down into subtypes based on the primary disorder in bowel habits. These subtypes include:
- IBS with predominant constipation (IBS-C)
- IBS with predominant diarrhea (IBS-D)
- IBS with mixed bowel habits (IBS-M)
- IBS Unclassified (IBS-U)
Subtyping is based on predominant bowel habits on days with abnormal bowel movements. Abnormal bowel movements are determined by using the Bristol Stool Form Scale (BSFS) which is pictured below. Abnormal bowel movements include types 1,2,6, and 7.
Rome IV Diagnostic Criteria For IBS Subtypes
- > ¼ (25%) of bowel movements with BSFS types 1 or 2
And - < ¼ (25%) of bowel movements BSFS types 6 or 7
- In clinical practice, a patient report of primarily experiencing constipation (BSFS type 1 or 2 ) may alternatively be used
- > ¼ (25%) of bowel movements with BSFS types 6 or 7 And
- < ¼ (25%) of bowel movements BSFS types 1 or 2
- In clinical practice, a patient report of primarily experiencing diarrhea (BSFS type 6 or 7 ) may alternatively be used
- > ¼ (25%) of bowel movements with BSFS types 1 or 2
And - > ¼ (25%) of bowel movements BSFS types 6 or 7
- Alternatively, in clinical practice, a patient reports experiencing both diarrhea and constipation
- >¼ abnormal bowel movements were constipation and > ¼ were diarrhea
- Patients who meet diagnostic criteria for IBS but whose bowel habits cannot be accurately categorized into one of the 3 groups should be categorized as IBS-U
- Alternatively for clinical practice, the patient reports that abnormal stools (both constipation) and diarrhea are rare.
3Accurately Subtyping IBS
- IBS subtypes can only be confidently determined while off of medications used to treat bowel habit abnormalities.
- Subtyping is more accurate when at least 4 days of abnormal bowel habits are experienced per month.
- Ideally, subtyping is determined based on a daily stool diary with at least 2 weeks of record-keeping
Rome IV Diagnostic Criteria For Non-IBS Functional Bowel Disorders
- Must include 2 or more of the following:
- Straining during more than ¼ (25%) of defecations
- Lumpy or hard stools (BSFS 1-2) more than ¼ (25%) of defecations
- Sensation of incomplete evacuation more than ¼ (25%) of defecations
- Sensation of anorectal obstruction/blockage > ¼ (25%) of defecations
- Manual maneuvers to facilitate more than ¼ (25%) of defecations (e.g., digital evacuation, support of the pelvic floor)
- Fewer than three spontaneous bowel movements per week
- Loose stools are rarely present without the use of laxatives
- Insufficient criteria for IBS
*Criteria fulfilled within the last 3 months with symptom onset at least 6 months prior to diagnosis
- Loose or watery stools, without predominant abdominal pain or bothersome bloating, occurring in more than 25% of stools
- Criteria fulfilled for the last 3 months with symptom onset at least 6 months prior to diagnosis
- Excludes patients meeting criteria for IBS-D
- Recurrent bloating and/or distention occurring on average at least 1 day/week; abdominal bloating and/or distention predominates over other symptoms**
- There are insufficient criteria for a diagnosis of irritable bowel syndrome, functional constipation, functional diarrhea, or postprandial distress syndrome
*fulfilled for the last 3 months with symptom onset at least 6 months prior to diagnosis
**Mild pain related to bloating may be present as well as minor bowel movement abnormalities
- Bowel symptoms not attributable to an organic etiology and that do not meet criteria for IBS, or functional constipation, diarrhea, or abdominal bloating/distention disorders
*Criteria fulfilled for the last 3 months with symptom onset at least 6 months prior to diagnosis
- New or worsening symptoms of constipation when initiating, changing, or increasing opioid therapy, that must include 2 or more of the following:
- Straining during more than ¼ (25%) of defecations
- Lumpy or hard stools (BSFS 1-2) more than ¼ (25%) of defecations
- Sensation of incomplete evacuation more than ¼ (25%) of defecations
- Sensation of anorectal obstruction/blockage > ¼ (25%) of defecations
- Manual maneuvers to facilitate more than ¼ (25%) of defecations (e.g., digital evacuation, support of the pelvic floor)
- Fewer than three spontaneous bowel movements per week
- Loose stools are rarely present without the use of laxatives
Key Takeaways
- The most common subtypes of IBS are IBS-D, IBS-C, and IBS-M
- Accurately subtyping IBS is best done when keeping a 2 week daily stool diary
- There are other functional bowel disorders outside of IBS that should be looked into if you do not meet the core criteria for an IBS diagnosis.
Tests For IBS
Your physician may decide to run tests for IBS or more often than not, to rule out other functional bowel disorders, as well as more serious health issues.
To learn more about this, check out our guide on IBS Tests. In it, we compare 26 of the most popular tests and not only explain what they look for, but also whether they’re worth taking.
