Irritable Bowel Syndrome Clinical Presentation
History and Physical Examination
A meticulous history is the key to establish a diagnosis of irritable bowel syndrome, which comprises a range of manifestations and aggravation factors.  The Rome criteria provide the construct upon which questions are based (see Diagnostic Considerations).
Altered bowel habits
Constipation results in complaints of hard stools of narrow caliber, painful or infrequent defecation, and intractability to laxatives. Diarrhea usually is described as small volumes of loose stool, with evacuation preceded by urgency or frequent defecation. Postprandial urgency is common, as is alternation between constipation and diarrhea. Characteristically, one feature predominates in a single patient, but significant variability exists among patients.
Descriptions are protean. Pain frequently is diffuse without radiation. Common sites of pain include the lower abdomen, specifically the left lower quadrant. Acute episodes of sharp pain are often superimposed on a more constant dull ache. Meals may precipitate pain, and defecation commonly improves pain. Defecation may not fully relieve pain, however.
Pain from presumed gas pockets in the splenic flexure may masquerade as anterior chest pain or left upper quadrant abdominal pain. This splenic flexure syndrome is demonstrable by balloon inflation in the splenic flexure and should be considered in the differential of chest or left upper quadrant abdominal pain.
Patients frequently report increased amounts of bloating and gas. Quantitative measurements fail to support this claim. People with irritable bowel syndrome may manifest increasing abdominal circumference throughout the day, as assessed by computed tomography (CT) scan. They may also demonstrate intolerance to otherwise normal amounts of abdominal distention.
Additional symptoms consistent with irritable bowel syndrome
Clear or white mucorrhea of a noninflammatory etiology is commonly reported. Epidemiologic associations with dyspepsia, heartburn, nausea, vomiting, sexual dysfunction (including dyspareunia and poor libido), and urinary frequency and urgency have been noted. Symptoms may worsen in the perimenstrual period, and fibromyalgia is a common comorbidity. Stressor-related symptoms may be revealed with careful questioning (emphasize avoidance of stressors).
Symptoms inconsistent with irritable bowel syndrome
Symptoms not consistent with irritable bowel syndrome should alert the clinician to the possibility of an organic pathology. Inconsistent symptoms include the following:
Onset in middle or older age
Acute symptoms (irritable bowel syndrome is defined by chronicity)
Anorexia or weight loss
The patient with irritable bowel syndrome has an overall healthy appearance but may be tense or anxious. The patient may present with sigmoid tenderness or a palpable sigmoid cord.
Criteria for Diagnosis
A consensus panel created and continually updates the Rome diagnostic criteria to provide a standardized diagnosis for research and clinical practice. The Rome IV criteria for the diagnosis of irritable bowel syndrome (IBS) were released in 2016 and require that patients have had recurrent abdominal pain on average at least 1 day per week during the previous 3 months that is associated with two or more of the following  :
Related to defecation (may be increased or unchanged by defecation)
Associated with a change in stool frequency
Associated with a change in stool form or appearance
Unlike the Rome III criteria, the Rome IV criteria only require abdominal pain in defining this condition; “discomfort” is no longer included owing to its ambiguity and different meanings across cultures and languages. 
Supporting symptoms include the following:
Altered stool frequency
Altered stool form
Altered stool passage (straining and/or urgency)
Abdominal bloating or subjective distention
Four bowel patterns may be seen with irritable bowel syndrome, and these remain unchanged in the Rome IV classification.  These patterns include the following:
IBS-D (diarrhea predominant)
IBS-C (constipation predominant)
IBS-M (mixed diarrhea and constipation)
IBS-U (unclassified; the symptoms cannot be categorized into one of the above three subtypes)
The usefulness of these subtypes is debatable. Notably, within 1 year, 75% of patients change subtypes, and 29% switch between constipation-predominant IBS and diarrhea-predominant IBS. The Rome IV criteria differ from the Rome III criteria in basing bowel habits on stool forms solely during days with abnormal bowel movements rather than on the total number of bowel movements. 
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