What are the symptoms of irritable bowel syndrome (IBS)?

Symptoms of Irritable Bowel Syndrome

The hallmark symptoms of IBS are chronic, recurrent abdominal pain or discomfort that is clearly linked to bowel function—either relieved by defecation or associated with changes in stool frequency or consistency—combined with disturbed bowel habits, present for at least 6 months. 1

Core Gastrointestinal Symptoms

Abdominal pain is mandatory for IBS diagnosis—patients with painless bowel dysfunction are classified as functional constipation or functional diarrhea, not IBS. 1, 2 The pain typically:

• Improves with defecation (suggesting colonic origin) 1
• Occurs at least 3 days per month for the past 3 months 1, 3
• Is colicky in nature and can occur at any abdominal site, though most commonly on the left side 4
• Worsens with eating in many patients 4

Disturbed bowel habits manifest as: 1

• More frequent stools at onset of pain 1
• Looser stools at onset of pain 1
• Changes in stool form or consistency associated with pain onset 1

Additional Common Gastrointestinal Features

These symptoms are not required for diagnosis but strongly support it: 1

• Visible abdominal bloating/distension—typically flat in the morning, progressively worsening throughout the day, peaking by late afternoon or evening, then subsiding overnight 1, 4
• Passage of mucus per rectum 1
• Sensation of incomplete evacuation 1
• Straining at defecation 1
• Urgency 1
• Abnormal stool frequency (<3/week or >3/day) 1

Symptom Pattern and Timing

Most patients experience symptoms intermittently, with flares lasting 2-4 days followed by periods of remission. 1, 2 One critical exception: patients with continuous, unremitting pain likely have "functional abdominal pain"—a distinct, severe condition requiring early recognition as these patients respond poorly to conventional IBS treatment and often have severe underlying psychological disturbances. 1

Non-Gastrointestinal Symptoms

These extra-intestinal symptoms are more frequent in IBS and support the diagnosis: 1, 2

• Constant lethargy/fatigue 1, 4
• Poor sleep 1
• Fibromyalgia 1, 2
• Low backache 1, 4
• Urinary frequency/irritable bladder symptoms 1, 4
• Dyspareunia in women 1, 4
• Chest pain 4
• Nausea 4

Stool Pattern Subtypes

Subtype classification is based solely on stool consistency using the Bristol stool chart: 2, 3

• IBS with constipation (IBS-C): Hard stools (Bristol 1-2) >25% of the time AND loose stools <25% of the time 1, 2
• IBS with diarrhea (IBS-D): Loose stools (Bristol 6-7) >25% of the time AND hard stools <25% of the time 1
• Mixed IBS (IBS-M): Both hard and loose stools >25% of the time 3

Demographic and Temporal Features

Symptom frequency peaks in the third and fourth decades of life, with a female predominance of approximately 2:1 in patients aged 20-40 years (though this gender bias lessens in older patients). 1 IBS symptoms persist beyond middle age and continue to be reported by substantial proportions of individuals in their seventh and eighth decades. 1

Critical Pitfall: Alarm Features That Exclude Simple IBS

The following "red flag" symptoms warrant immediate extended investigation and suggest alternative diagnoses: 2

• Unintentional weight loss 1
• Rectal bleeding (not explained by hemorrhoids/fissures) 1, 2
• Nocturnal symptoms (diarrhea or pain awakening the patient) 1, 2
• Anemia 1, 2
• Fever 5
• Age ≥45-50 years at symptom onset 1, 2
• Short symptom duration (<6 months) 1, 2
• Family history of colorectal cancer, inflammatory bowel disease, or celiac disease 2

Behavioral and Psychosocial Features

Helpful diagnostic behavioral patterns include: 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 1, 2