Symptoms and Diagnosis of IBS

Symptoms of Irritable bowel syndrome (IBS) are often non-specific, including diarrhea, abdominal pain, bloating, postprandial fullness and constipation.

The diagnostic approach should begin with a detailed medical history to correlate the symptoms of the patient with those typical of IBS. The patient should also be asked for a subjective assessment of the severity and impact of symptoms on daily life in order to gain an understanding of the disease burden for the patient. Exclusion of other potential causes in order to avoid mis-diagnosis.

The Rome III criteria [1,2] are the gold standard for IBS diagnosis. The system was developed to classify functional gastrointestinal disorders of the digestive system in which symptoms cannot be explained by the presence of structural or tissue abnormality. The criteria instead classify disorders based on clinical symptoms, outlined as:

Recurrent abdominal pain or discomfort at least 3 days/month in the last 3 months associated with two or more of the following:

1. Improvement with defecation
2. Onset associated with a change in frequency of stool
3. Onset associated with a change in form (appearance) of stool

UK NICE IBS guidelines [3,4]

The National Institute of Clinical Excellence produced guidance on the diagnosis and management of IBS in 2008. These were updated in 2015 and state that IBS is characterized by the presence of abdominal pain or discomfort, which may be associated with defecation and/or accompanied by a change in bowel habit. This guidance provides further clarification by confirming that symptoms of IBS may include disordered defecation (constipation or diarrhea, or both) and abdominal distension, usually referred to as bloating. Other features such as lethargy, nausea, backache and bladder symptoms are common in people with IBS, and may be used to support the diagnosis.

Despite the availability of Rome III diagnostic criteria, it may still be challenging for healthcare professionals to differentiate IBS from organic disease such as bowel cancer or inflammatory bowel disease, bile acid diarrhea, celiac disease/NCGS or gastrointestinal food allergy. For example, research suggests that undetected celiac disease is present in more than 4% of patients with typical IBS [3]. A detailed case history should be taken and if suspicion arises or red flags are noted then patients should be referred for the appropriate tests or investigations.

Red flag symptoms

The presence of certain ‘red flag’ symptoms in a patient presenting with suspected IBS may indicate an alternative diagnosis and therefore prompt further investigation by the clinician [4]. Such symptoms are outlined below:

• Unintentional and unexplained weight loss
• Rectal bleeding
• Family history of bowel or ovarian cancer
• A change in bowel habit to looser and/or more frequent stools persisting for more than 6 weeks in a person aged over 60 years
• Unexplained anemia
• Abdominal masses
• Rectal masses
• Inflammatory markers for inflammatory bowel disease