Change in bowel habit

• Irritable Bowel Syndrome (IBS): Change in bowel habit with abdominal pain relieved by defecation, associated with bloating.
• Functional Diarrhoea: Chronic diarrhoea without an organic cause, often stress-related.
• Functional Constipation: Chronic constipation with no identifiable organic cause, often with straining or incomplete evacuation.

• Gastroenteritis: Acute onset of diarrhoea with or without vomiting, often associated with recent travel or contaminated food.
• Clostridium difficile Infection: Diarrhoea following antibiotic use, often in a hospital setting, associated with fever.
• Parasitic Infections: Persistent diarrhoea following travel to endemic areas, e.g., Giardia.

• Inflammatory Bowel Disease (Crohn’s Disease, Ulcerative Colitis): Chronic diarrhoea, often bloody, with abdominal pain, weight loss, and systemic symptoms such as fever.
• Diverticulitis: Altered bowel habit with left lower quadrant pain, fever, and raised inflammatory markers.
• Microscopic Colitis: Chronic watery diarrhoea, more common in older adults, often associated with autoimmune conditions.

• Colorectal Cancer: Persistent change in bowel habit, particularly in older adults, often with rectal bleeding, weight loss, and iron deficiency anaemia.
• Small Bowel Tumours: May present with intermittent obstruction, altered bowel habit, and occasionally bleeding.
• Neuroendocrine Tumours: Chronic diarrhoea with flushing, wheezing, and right-sided heart failure.

• Coeliac Disease: Chronic diarrhoea, often with weight loss, iron deficiency anaemia, and dermatitis herpetiformis.
• Chronic Pancreatitis: Steatorrhoea, abdominal pain, and weight loss, often with a history of alcohol excess.
• Lactose Intolerance: Diarrhoea, bloating, and flatulence after consuming dairy products.

• Hyperthyroidism: Diarrhoea, weight loss, heat intolerance, and tremor.
• Hypothyroidism: Constipation, weight gain, cold intolerance, and dry skin.
• Diabetes Mellitus: Diarrhoea with possible autonomic neuropathy, or constipation due to gastroparesis.

Sudden onset may suggest infective or acute inflammatory causes (e.g., gastroenteritis, diverticulitis), while chronic onset suggests functional, inflammatory bowel disease, or malignancy.

Watery stools are common in infective or functional diarrhoea, while bloody stools suggest IBD, ischaemia, or malignancy. Steatorrhoea points to malabsorption syndromes.

Presence of abdominal pain, weight loss, fever, or systemic symptoms may suggest an inflammatory or neoplastic cause.

• Past Medical History: Previous bowel disorders, autoimmune conditions, or surgeries.
• Drug History: Use of medications that may cause constipation (e.g., opioids) or diarrhoea (e.g., antibiotics).
• Family History: Family history of colorectal cancer, IBD, or coeliac disease.
• Social History: Recent travel, alcohol use, diet, and lifestyle factors.

• Full Blood Count: Look for anaemia (e.g., iron deficiency in colorectal cancer or IBD).
• C-Reactive Protein (CRP): Raised in inflammatory conditions such as IBD or diverticulitis.
• Thyroid Function Tests: To identify hyperthyroidism or hypothyroidism.
• Tissue Transglutaminase Antibodies (tTG): For coeliac disease screening.

• Stool Culture: To identify infectious agents in gastroenteritis.
• Faecal Calprotectin: Raised in inflammatory bowel disease, distinguishing from IBS.
• Faecal Occult Blood Test (FOBT): Screening for colorectal cancer.
• Ova, Cysts, and Parasites (OCP): For parasitic infections, especially in travel history.

• Colonoscopy: Gold standard for investigating suspected colorectal cancer or IBD.
• CT Abdomen/Pelvis: Useful in identifying diverticulitis, malignancies, and other structural abnormalities.
• Abdominal Ultrasound: First-line for right upper quadrant pain, e.g., to rule out biliary causes.
• MRI Enterography: Particularly useful in Crohn’s disease to assess small bowel involvement.