What are the signs and symptoms of Irritable Bowel Syndrome (IBS)?

Signs and Symptoms of Irritable Bowel Syndrome

IBS is characterized by chronic, recurring abdominal pain or discomfort that is clearly linked to bowel function—either relieved by defecation or associated with changes in stool frequency or consistency—and symptoms must be present for at least 6 months to establish the diagnosis. 1

Core Diagnostic Features

The Rome III criteria define IBS as recurrent abdominal pain or discomfort at least 3 days per month in the past 3 months, associated with two or more of the following: 1

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

Importantly, "discomfort" means an uncomfortable sensation not described as pain, and criteria must be fulfilled for the past 3 months with symptom onset at least 6 months before diagnosis. 1

Common Associated Symptoms (Not Part of Diagnostic Criteria)

While not required for diagnosis, these Manning criteria symptoms are frequently present and help support the clinical picture: 1

• Bloating and visible abdominal distension 1
• Abnormal stool form (hard and/or loose stools) 1
• Abnormal stool frequency (<3 bowel movements per week or >3 per day) 1
• Straining at defecation 1
• Urgency (having to rush to have a bowel movement) 1
• Feeling of incomplete evacuation 1
• Passage of mucus per rectum 1

Temporal Pattern of Symptoms

Most patients experience symptoms intermittently, with flares lasting two to four days followed by periods of remission. 1, 2 The median time to recurrence after symptom improvement is approximately 10 weeks (range 6 to 24 weeks). 3

One critical exception: Patients with continuous, unremitting pain likely have "functional abdominal pain" rather than IBS—an unusual and particularly severe condition requiring early recognition, as these patients respond poorly to conventional treatment and often have severe underlying psychological disturbances. 1

Stool Pattern Classification

IBS subtypes are defined solely by stool consistency using the Bristol Stool Scale: 1

• IBS with constipation (IBS-C): Hard stools >25% of the time and loose stools <25% of the time 1, 2
• IBS with diarrhea (IBS-D): Loose stools >25% of the time and hard stools <25% of the time 1, 2
• IBS-mixed (IBS-M): Both hard and soft stools >25% of the time 1, 2
• IBS-unclassified (IBS-U): Neither loose nor hard stools >25% of the time (approximately 4% of patients) 1, 2

Patients whose bowel habits change from one subtype to another over months and years are termed "alternators." 1

Behavioral and Clinical Features Supporting Diagnosis

These features help distinguish IBS from organic disease in general practice: 1

• Symptoms present for more than 6 months 1
• Frequent consultations for non-gastrointestinal symptoms 1
• Previous medically unexplained symptoms 1
• Patient reports that stress aggravates symptoms (reported by 60% of IBS patients, though also true in 40% of organic disease) 1

Food-Related Symptoms

Many patients report symptom aggravation by meals, with considerable overlap with functional dyspepsia (reported in 42% to 87% of IBS patients): 1, 4

• Epigastric pain, nausea, vomiting, and early satiety are common 1
• Pain aggravated within 90 minutes of eating occurs in 50% of occasions, representing either small intestinal symptoms or exaggerated colonic response to food 1, 4
• Morning rush pattern: Repeated defecation in the morning when stool consistency changes from an initial formed stool to progressively looser stool as colonic contents are cleared 1, 4

Associated Non-Gastrointestinal Symptoms

These symptoms are important because they can result in inappropriate referrals to other specialties: 1

• Lethargy 1
• Backache 1
• Headache 1
• Urinary symptoms: Nocturia, frequency and urgency of micturition, incomplete bladder emptying 1
• In women: Dyspareunia 1

Critical Alarm Features Requiring Further Investigation

These features suggest organic disease rather than IBS and mandate additional workup: 1, 5, 2

• Age >50 years at symptom onset 1, 5, 2
• Short history of symptoms 1, 5
• Documented weight loss 1, 5
• Nocturnal symptoms (waking from sleep with pain or diarrhea) 1, 5, 2
• Male sex 1
• Family history of colon cancer 1, 5
• Anemia 1, 5
• Rectal bleeding 1, 5, 2
• Recent antibiotic use 1
• Fever 5, 2

Demographics and Natural History

• Peak frequency: Third and fourth decades of life 1
• Female predominance: Approximately 2:1 in patients in their 20s and 30s, though this gender bias becomes less apparent in older patients 1, 2
• Persistence: IBS symptoms persist beyond middle life and continue to be reported by a substantial proportion of individuals in their seventh and eighth decades 1, 2

Prognostic Factors

Prognosis depends critically on two factors: 1, 4, 2

• Length of history: Patients with a longer history are less likely to improve 1, 2
• Chronic ongoing life stress: This is the key prognostic factor—no patients with ongoing life stresses recovered over a 16-month follow-up period, compared with 41% recovery in those without such stresses 1, 4, 2

Common Clinical Pitfall

IBS is considered a painful condition. Patients with painless bowel dysfunction should be labeled as having "functional constipation" or "functional diarrhea" rather than IBS, though they may share underlying pathology with their respective IBS subtypes. 1