🩺 Diarrhoea

Diarrhoea is defined as the passage of three or more loose or liquid stools per day. It is a common presentation in the UK, ranging from self-limiting viral gastroenteritis to life-threatening conditions like colorectal cancer or severe inflammatory bowel disease. Management is primarily focused on assessing and correcting dehydration while identifying the underlying cause through a structured history and appropriate diagnostic testing. Classification into acute, persistent, and chronic helps guide the urgency and type of investigation.

Differentiate between acute (<14 days) and chronic (>4 weeks) presentations. Inquire about the duration, frequency, and character of stool (watery, bloody, or steatorrhoea). Ask about associated systemic symptoms like fever, weight loss, and abdominal pain. Explore risk factors such as travel history, contact with others with similar symptoms, recent dietary changes, and medication history (e.g., antibiotics, NSAIDs, or PPIs). Family history of bowel cancer or IBD is significant.

Assess fluid status immediately by checking skin turgor, mucous membranes, capillary refill time, and lying/standing blood pressure. Abdominal examination should look for tenderness, guarding, or palpable masses suggestive of malignancy or inflammatory bowel disease. Perform a digital rectal examination (DRE) if there is blood, tenesmus, or a suspicion of impaction. Systemic signs such as joint swelling or skin rashes (e.g., erythema nodosum) may point towards an inflammatory aetiology.

Gastroenteritis (viral/bacterial), Irritable Bowel Syndrome (IBS), Inflammatory Bowel Disease (Crohn’s/Ulcerative Colitis), Microsopic Colitis, Malabsorption (Coeliac/Lactose intolerance), Colorectal Malignancy, Hyperthyroidism, and Medication-induced (Metformin/Antibiotics).

Unintentional weight loss, rectal bleeding, nocturnal symptoms, family history of colorectal cancer (under 50), abdominal/rectal mass, and anaemia (iron deficiency).

Stool culture and sensitivity are indicated if the patient is systemically unwell, has blood in the stool, or has recently travelled. Check C. difficile toxin if there is recent antibiotic exposure or hospitalisation. Bloods should include FBC (anaemia/leucocytosis), U&Es (electrolyte derangement/AKI), and CRP. For chronic cases, include Coeliac serology (IgA TTG), thyroid function tests, and faecal calprotectin. If red flags are present, urgent colonoscopy or flexible sigmoidoscopy is required.

Always clarify the consistency of the stool; patients often use 'diarrhoea' to describe frequent but formed movements. Nocturnal diarrhoea is a high-yield 'organic' marker suggesting pathology like IBD rather than IBS. Check for a history of recent antibiotic use (C. difficile) or travel. In elderly patients with 'overflow' diarrhoea, always perform a DRE to exclude faecal impaction. Chronic diarrhoea often requires a malabsorption screen including coeliac serology and faecal calprotectin.

Focus on 'Red Flag' symptoms requiring urgent referral via the 2-week wait pathway. Understand the management of acute dehydration using ORS and the restricted use of antimotility agents like Loperamide (avoid in bloody diarrhoea/suspected C. difficile). Recognise the diagnostic criteria for IBS and the role of faecal calprotectin in primary care.