Diarrhoea
Red Flags — when diarrhoea is not "just a bug"
| Red flag | Why it matters | Action |
|---|---|---|
| Persistent change in bowel habit (≥4–6 weeks) to looser/more frequent stools, esp. 50+, with rectal bleeding / weight loss / iron-deficiency anaemia / abdominal or rectal mass | Colorectal cancer — diarrhoea can be the presenting symptom. | FIT + NICE NG12 colorectal pathway; FBC/ferritin; PR/abdominal exam |
| Bloody diarrhoea | Invasive infection (incl. E. coli O157 → HUS), IBD, ischaemic colitis; anti-motility/antibiotics may be harmful. | Stool tests; avoid anti-motility/empirical antibiotics in possible O157; assess for IBD; refer if needed |
| Dehydration / shock — especially infants, elderly, frail, immunocompromised | Rapid decompensation; electrolyte disturbance; AKI. | Rehydrate; admit if severe / unable to maintain hydration |
| C. difficile (diarrhoea during/after antibiotics or PPI, elderly, recent hospital) | Can cause severe colitis/toxic megacolon. | Stool for C. diff; stop precipitant; treat per guidance; isolate; assess severity |
| Features of IBD — chronic/bloody diarrhoea, nocturnal symptoms, weight loss, raised CRP/calprotectin, mouth/joint/eye/skin signs | Needs specialist diagnosis/treatment; flares can be serious. | Calprotectin/CRP; gastroenterology referral; don't mislabel as IBS |
| Severe abdominal pain / peritonism / systemic sepsis | Surgical abdomen, ischaemic colitis, severe colitis. | Same-day surgical/medical assessment |
🔎 Reframing the bug
Challenge the timeline gently but clearly.
"A bug rarely lasts six weeks, and the weight loss and blood aren't part of a simple bug — so rather than just settling it, I want to find out what's actually going on."🧫 The embarrassing questions
Normalise asking about blood and bowels.
"I'm going to ask some questions people find awkward, and I'll need to examine your tummy and back passage — it's routine and important, and it's the quickest way to keep you safe."⚖️ Thorough, not alarming
Pitch the cancer-pathway tests proportionately.
"Most of the time these tests are reassuring. I'd rather check properly now than miss something — that's just being thorough given your age and what you've told me."👨👩👦 The family history
Acknowledge his father's cancer honestly.
"With your dad having had bowel cancer, I know this might be on your mind — that's another reason to do the right checks now and not just paper over it."- Accepting "it's a bug" and giving symptomatic treatment only
- Not screening red flags / not arranging FIT + bloods
- Not asking about coeliac/medication/infective causes
- Not examining (abdomen ± PR)
Same day / 999
Immediate action- Severe dehydration / shockEspecially frail/elderly/infant → admit
- Severe colitis / peritonism / sepsisSame-day assessment
- Significant GI bleedingUrgent admission
Days–2 weeks
Investigate / refer- Cancer red flagsFIT + NG12 colorectal referral; bloods
- Suspected IBDCalprotectin/CRP; gastroenterology
- C. difficile / significant infectionStool tests; treat; public health
Primary care
Manage / work-up- Acute infective (well, hydrated)Rehydration, hygiene/exclusion, no routine antibiotics
- Chronic, no red flagsBloods, coeliac, calprotectin; consider IBS
- Drug/dietary causeReview medication/diet
- Treating a red-flag presentation as routine
- Missing dehydration in the vulnerable / C. diff after antibiotics
- Omitting PR / abdominal exam in a change of bowel habit
- Not assessing hydration in acute/vulnerable patients
- Not doing FIT/bloods in a red-flag presentation
- Forgetting coeliac serology; ordering calprotectin when alarm features mandate cancer referral anyway
🚩 IBS is a positive diagnosis — and Trevor isn't IBS
The classic error is to reach for "IBS" or "a bug" in a patient with alarm features. IBS is diagnosed positively (typical symptoms, normal investigations, no red flags), usually in younger patients. For Trevor — 58, ≥4 weeks of looser stools, weight loss, rectal bleeding, fatigue and a family history — the formulation is a colorectal-cancer red-flag presentation requiring FIT and the NG12 pathway, with IBD and coeliac also in view. The discipline is to exclude the serious before comforting with the benign.
- Diagnosing IBS/"bug" in the presence of alarm features
- Not naming the need for cancer-pathway referral
- Not referring red-flag change in bowel habit (NG12)
- Not notifying/advising exclusion for relevant infections
Validate — name the expectation and the inconvenience
Six weeks of urgency and frequent loose stools is genuinely disruptive: planning journeys around toilets, broken sleep, worry at work. Trevor's request for a tablet is reasonable from where he sits. Naming it — and the impact behind it — before declining it stops him feeling dismissed and makes the explanation that follows land as care rather than refusal.
"I can hear this has really been getting in the way — rushing to the loo several times a day for six weeks is exhausting, and it makes complete sense that you'd want something to calm it down."Explain — why a "plug" is the wrong first step
Loperamide would treat the symptom and could make Trevor feel better while hiding the very change that tells us something is wrong. With weight loss, blood, fatigue and a family history at 58, the priority is to find the cause. The explanation should be honest about why (bowel cancer is one of the things being checked for) but proportionate (most people tested this way do not have cancer).
"If I just gave you something to slow things down, you might feel better for a while — but it could hide what's causing this. With the weight loss and the blood, I want to find the reason first. Most of the time these checks come back reassuring, but bowel problems like this are exactly what the tests are designed to pick up early."Negotiate — what he gets today
He should leave with something concrete: an examination done today, bloods and a FIT kit, an urgent referral explained, practical advice to manage urgency safely (fluids, knowing where toilets are, keeping a stool and food diary), clear safety-net symptoms, and a date to discuss results. Loperamide is best avoided while the cause is unknown — he has rectal bleeding and red flags — and is only revisited once the investigations have excluded colitis or cancer.
"Here's what I can do today: examine you, send some bloods and a simple stool test, and refer you to the bowel team quickly. Meanwhile, let's make the day-to-day easier — keeping your fluids up and noting down what's happening. And I'll ring you with the results so you're not left waiting and wondering."Glucose-coupled sodium absorption in the small bowel stays intact in most infective diarrhoea, so a solution containing both sodium and glucose drives water absorption even while the gut is secreting. That is why oral rehydration salts (ORS) outperform plain water or sugary drinks in people at risk of dehydration.
Healthy adults: increase usual fluids; ORS for those at risk (older, frail, comorbid). Children under 5: continue breast or formula feeds; offer ORS as supplemental fluid if at risk of dehydration, and avoid fruit juices and carbonated drinks until diarrhoea has stopped (NICE CG84). Admit if unable to keep fluids down or clinically dehydrated and not improving.
Early refeeding supports enterocyte recovery and prevents the nutritional deficit that prolongs illness. Starving the gut is outdated advice. In chronic diarrhoea, specific dietary triggers (lactose, sorbitol and other sweeteners, caffeine, alcohol, high-fat meals) can worsen symptoms and point to a cause.
Acute: small, frequent, plain meals once rehydrated. Chronic: a 2-week food and stool diary (Bristol stool form, timing, nocturnal symptoms, blood). Do not cut out gluten before coeliac serology (NICE NG20). Low-FODMAP diets belong to confirmed IBS and are best dietitian-led (NICE CG61).
Norovirus and many bacterial pathogens spread by the faecal–oral route and remain transmissible for a period after symptoms stop. Alcohol gel does not reliably kill norovirus or C. difficile spores — soap and water does the mechanical work.
Handwashing with soap and water after the toilet and before food; don't prepare food for others; don't share towels; clean toilet surfaces with bleach-based products. Stay off work or school until 48 hours after the last episode (UKHSA). Food handlers, health and care staff and young children are higher-risk groups — some organisms (e.g. STEC/E. coli O157, typhoid) need longer exclusion and clearance samples arranged by the local health protection team. Avoid swimming pools for 2 weeks after Cryptosporidium.
Volume depletion reduces renal perfusion. ACE inhibitors/ARBs remove efferent arteriolar tone, NSAIDs remove afferent prostaglandin dilatation, diuretics deplete volume further, metformin accumulates as eGFR falls, and SGLT2 inhibitors can precipitate ketoacidosis with near-normal glucose when intake falls. Sulfonylureas cause hypoglycaemia if the person is not eating.
"SADMANS" (Sulfonylureas, ACE inhibitors, Diuretics, Metformin, ARBs, NSAIDs, SGLT2 inhibitors): advise temporarily withholding during significant diarrhoea/vomiting or inability to keep fluids down, and restarting drug by drug on a written trigger once recovered (no blanket 24–48-hour rule). Individualise — insulin must never simply be stopped, and heart-failure diuretics may need specialist advice. Check U&E if the patient is unwell or on several of these drugs.
Travellers' diarrhoea is usually bacterial (e.g. enterotoxigenic E. coli, Campylobacter) and self-limiting, but parasites (Giardia, amoebiasis) cause persistent symptoms, and fever after travel to a malaria area is malaria until proven otherwise.
Pre-travel: food and water hygiene, ORS sachets in the travel kit, typhoid and hepatitis A vaccination where indicated (NaTHNaC country guidance). Post-travel: stool microscopy, culture and ova/cysts/parasites if persistent or bloody; same-day malaria testing if febrile after travel to an endemic area.
Urgency and fear of incontinence drive avoidance — not going out, skipping meals, reducing fluids — which worsens fatigue and dehydration. Practical coping lowers anxiety while the cause is found.
Plan routes with known toilets; a RADAR key or a "Just Can't Wait" toilet card (Bladder & Bowel UK) can help; carry spare underwear and wipes; keep fluids up rather than cutting them to reduce urgency. A fit note with adjusted duties is reasonable if symptoms affect work.
Fluids first; drugs only for selected adults
- Oral fluids little and often; ORS for those at risk of dehydration (older, frail, comorbid)
- Antiemetic for distressing vomiting in adults — dose per SPC
- Loperamide for non-bloody diarrhoea in adults who need short-term relief: 4 mg initially then 2 mg after each loose stool, maximum 16 mg/day (SPC), for a few days only
- Antibiotics not routinely: consider only if systemically unwell, immunocompromised, or a confirmed organism that needs treatment — guided by the stool result and microbiology advice
Review the precipitants, assess severity, then treat
- Review and, where possible, stop the antibiotic(s); review the need for PPIs and other medicines with GI activity (e.g. laxatives)
- Do not offer antimotility drugs such as loperamide
- First episode, any severity: oral vancomycin 125 mg four times a day for 10 days
- Second-line (vancomycin ineffective): fidaxomicin 200 mg twice a day for 10 days
- Relapse within 12 weeks of symptom resolution: fidaxomicin; recurrence after 12 weeks: vancomycin or fidaxomicin
- Refer to hospital if symptoms or signs are severe or worsen rapidly; consider referral or specialist advice if at high risk of complications or recurrence (e.g. age, frailty, comorbidities). Life-threatening infection is managed in hospital with specialist advice
Diagnosis first, then cause-specific therapy
- IBS-D (positive diagnosis, red flags absent, coeliac serology and calprotectin normal): loperamide first-choice antimotility; low-dose tricyclic second-line if laxatives, loperamide or antispasmodics have not helped (NICE CG61)
- Coeliac disease: lifelong gluten-free diet with dietitian — no drug substitute (NICE NG20)
- Bile acid diarrhoea: bile acid sequestrant (e.g. colestyramine) after SeHCAT or a specialist-guided trial
- Microscopic colitis: stop likely culprit drugs; budesonide is the specialist treatment of choice
- IBD: specialist-led induction and maintenance (see ulcerative colitis / Crohn's protocols)
- Pancreatic insufficiency: pancreatic enzyme replacement with meals (dose per SPC / specialist)
- Bloody diarrhoea or high fever (dysentery) — risk of prolonging invasive infection; in suspected STEC (including E. coli O157) antimotility drugs increase the risk of haemolytic uraemic syndrome, and antibiotics should not be started without specialist or public-health advice
- Suspected or confirmed C. difficile or antibiotic-associated colitis — NG199 says do not offer antimotility medicines
- Acute ulcerative colitis / severe colitis — risk of toxic megacolon
- Children — NICE CG84 advises against antidiarrhoeal medicines in under-5s; loperamide is not for acute diarrhoea in young children (SPC)
- Undiagnosed chronic diarrhoea with red flags — masks the symptom that should drive investigation (Trevor)
- High doses — MHRA Drug Safety Update (September 2017): serious cardiac adverse reactions (QT prolongation, torsades de pointes, cardiac arrest) reported with high doses, largely in misuse and abuse; naloxone is the antidote in overdose, with prolonged monitoring because loperamide outlasts it
- Assess dehydration with the CG84 table: "red flag" signs include appearing unwell or deteriorating, altered responsiveness, sunken eyes, tachycardia, tachypnoea and reduced skin turgor; shock (pale/mottled skin, cold extremities, weak pulses, prolonged capillary refill, hypotension, decreased consciousness) needs emergency IV fluids
- No clinical dehydration: continue feeds; encourage fluids; ORS supplementation if at increased risk
- Clinical dehydration: ORS 50 ml/kg over 4 hours plus maintenance, often and in small amounts; IV fluids if shock or ORS not tolerated
- Do not use antidiarrhoeal medicines; antibiotics are not given routinely — only in specific situations (suspected or confirmed septicaemia; extra-intestinal spread of bacterial infection; Salmonella gastroenteritis in a child under 6 months, malnourished or immunocompromised; C. difficile-associated pseudomembranous enterocolitis, giardiasis, dysenteric shigellosis, dysenteric amoebiasis or cholera). Seek specialist advice on antibiotics if recently abroad
- Typical course: diarrhoea usually 5–7 days, stopping within 2 weeks; vomiting usually 1–2 days, stopping within 3 days — longer than this warrants review
"Make each sachet up with exactly the amount of water on the pack — not stronger, not weaker. Sip it little and often, a mouthful every few minutes, rather than gulping. If you or your child can't keep anything down, or stop passing urine, come back the same day."
SCA: in acute diarrhoea, the prescription that scores is hydration advice plus safety-netting — not an antibiotic. Naming ORS and explaining "little and often" shows you know what actually prevents harm.
"This slows the bowel down — it doesn't treat the cause. Don't use it if you see blood, have a fever, or have been on antibiotics recently. Never take more than the maximum on the pack: very high doses can affect the heart rhythm."
SCA: the examiner is watching whether you prescribe loperamide reflexively. Declining it for bloody diarrhoea, suspected C. difficile or a red-flag presentation — and explaining why — scores in both Tasks and Relating to Others.
"This antibiotic works inside the bowel to clear the C. diff infection. Take it four times a day for the full 10 days. Wash your hands with soap and water — alcohol gel doesn't kill the spores. Tell any doctor who prescribes you antibiotics in future that you've had C. diff."
SCA: after treating, close the loop — stop or review the causative antibiotic, review the PPI, never add loperamide, and give a specific severity safety-net (fever, worsening pain, distension, blood, dehydration).
"This is a more targeted antibiotic used when the infection hasn't cleared or has come back quickly. Take it twice a day for 10 days and keep up your fluids."
Knowing that NG199 puts vancomycin first and fidaxomicin second (with metronidazole no longer first-line) is a common AKT and SCA discriminator.
"This binds the bile that's irritating your bowel. Mix it well with water or juice. It also stops other tablets being absorbed, so take your other medicines at least 1 hour before or 4–6 hours after it."
Bile acid diarrhoea is under-recognised and often mislabelled as IBS-D. Asking about gallbladder or ileal surgery is a high-yield history point.
"This is a steroid that works mainly on the bowel lining with less effect on the rest of the body. Symptoms can come back when it's stopped, so we'll plan the course with the hospital team."
If a colonoscopy is "normal" but watery diarrhoea persists, ask whether biopsies were taken — microscopic colitis is invisible to the naked eye.
Work, exclusion and money
For acute infective diarrhoea, occupation changes the advice: food handlers, health and care workers and those who care for young children or vulnerable adults must stay off until 48 hours after the last episode, and some organisms need longer exclusion with microbiological clearance (UKHSA). This can mean lost income for zero-hours or self-employed workers — acknowledge the pressure, but don't bend the rule. For chronic urgency, a fit note recommending adjusted duties or access to toilets can keep someone working.
"I know being off costs you. The 48-hour rule protects the people you serve and your colleagues — if it's a problem with your employer, I can put it in writing."Driving and DVLA
Diarrhoea itself does not usually require DVLA notification. What matters is fitness at the time: dizziness from dehydration, fatigue from anaemia, or sedating medicines such as codeine. Urgency can make long journeys and professional driving hazardous. If Trevor later needs bowel surgery, he should not drive until he can safely perform an emergency stop — and a Group 2 (HGV/PCV) driver should check current DVLA guidance for any condition-specific rules.
"If you feel light-headed or wiped out, don't drive until that's settled. And if your job involves driving, let's think about how urgency affects that while we get to the bottom of it."Family and inherited risk
Trevor's father's bowel cancer shapes both his fear and his risk. If a cancer or a hereditary pattern is found, his children and siblings may need counselling about screening. Partners often carry the worry too — inviting them to results appointments can help. Families also matter for infection control: household hygiene limits spread of norovirus and C. difficile.
"Would it help to bring someone with you when we go through the results? And depending on what we find, there may be things worth your children knowing about too."Embarrassment and masculinity
Men of Trevor's age often minimise bowel symptoms and delay presenting; rectal bleeding and the PR examination are particular barriers. Normalising the conversation, using plain words, offering a chaperone and explaining why the examination matters all increase uptake. Returning the FIT kit is another point where embarrassment causes delay — a clear explanation of how simple it is helps.
"Doctors talk about bowels all day — nothing you tell me will surprise me. The stool test is a tiny sample on a stick; it's much easier than people expect."Waiting for results
The interval between referral and diagnosis is often the most anxious part. Uncertainty feeds catastrophising, poor sleep and avoidance. Knowing exactly how and when results will be given, and who to call, reduces distress. The NHS Faster Diagnosis Standard aims for a diagnosis or all-clear within 28 days of an urgent referral.
"It's normal to worry while you wait. The aim is that within four weeks you'll know one way or the other. If the wait is getting to you, ring — you don't need a new symptom to call."Food, social life and identity
Chronic diarrhoea changes how people eat and socialise — skipping meals before going out, avoiding restaurants, drinking less fluid. A diagnosis such as coeliac disease or IBD brings lifelong change: gluten-free eating, flares, medication. Signpost support (Coeliac UK, Crohn's & Colitis UK, Bowel Cancer UK) and a dietitian when the cause is known.
"Once we know what this is, we'll make a plan that lets you get back to eating out and living normally — there's good support available for every one of the likely causes."Today — Examine, test, refer, safety-net
Abdominal and PR examination (chaperone offered and documented). FBC, ferritin, U&E, LFTs, CRP, TFTs, coeliac serology (tTG-IgA + total IgA, on gluten). FIT kit issued with clear return instructions. Suspected cancer pathway referral per local FIT pathway (don't delay if strong clinical concern). Stool culture/C. difficile only if indicated. Written safety-net; results process agreed; tell him the practice will chase.
Within 1–2 weeks — Results and FIT return
Confirm the FIT was returned and resulted; review bloods. Treat iron deficiency if present (and remember iron-deficiency anaemia is itself a lower-GI cancer red flag). Positive coeliac serology → refer for biopsy and keep eating gluten. Check the referral has been received and the patient has an appointment. Unreturned FIT → proactive contact.
By ~4 weeks — Diagnosis or all-clear
Faster Diagnosis Standard: diagnosis communicated or cancer ruled out within 28 days of referral. If cancer confirmed: support, fit note, cancer care review, family implications. If colonoscopy normal: confirm biopsies were taken (microscopic colitis), and continue the chronic diarrhoea work-up — calprotectin, bile acid diarrhoea, pancreatic insufficiency, medication review.
6–8 weeks — Symptom and treatment review
If a benign cause is treated (coeliac, IBD, bile acid diarrhoea, microscopic colitis, drug withdrawal): check response, weight, haematinics, hydration. If IBS is diagnosed after negative investigations: positive explanation, subtype-directed management (NICE CG61). Persisting unexplained symptoms → gastroenterology.
Longer term — Condition-specific
Coeliac: annual review (symptoms, adherence, weight, bloods per NICE NG20; bone health; vaccination for hyposplenism). IBD: shared-care monitoring and surveillance per specialist. IBS: review as a relapsing condition; any new alarm feature restarts the cancer pathway. Family history: discuss relatives' screening where indicated.
Memory rule — diarrhoea monitoring
At every contact: duration (acute vs now chronic?); red flags (blood, weight, anaemia, mass, nocturnal symptoms); hydration and U&E in the vulnerable; sick-day drugs withheld and restarted correctly; results owned (FIT, bloods, stool, referral); and antimotility use (quantity, contraindications).
| What | Monitor | Timing | Action threshold |
|---|---|---|---|
| FIT | Result and kit return | Chase within 1–2 weeks | ≥10 µg Hb/g → suspected cancer pathway referral (NICE NG12). Kit not returned → contact patient. FIT <10 but ongoing concern or red flags → do not dismiss; follow local pathway and safety-net or refer |
| FBC / ferritin | Hb, MCV, ferritin | Baseline; after iron replacement | Iron deficiency → treat and investigate cause (lower GI and coeliac); anaemia without iron deficiency in over-60s is also a FIT criterion (NICE NG12, updated April 2026; HTG690) |
| U&E | Creatinine, potassium, sodium | If dehydrated, frail, or on SADMANS drugs | Rising creatinine / AKI → withhold nephrotoxic drugs, rehydrate, consider admission; restart each drug on its own written trigger once eating and drinking normally and renal function recovering |
| Coeliac serology | tTG-IgA + total IgA | Once, while on gluten | Positive → gastroenterology for biopsy; continue gluten until then. IgA deficient → IgG-based test (NICE NG20) |
| Faecal calprotectin | Level vs local pathway thresholds | When cancer not suspected | Raised → suspected IBD pathway per local guidance; normal with typical symptoms supports IBS (NICE HTG320) |
| C. difficile treatment | Stool frequency, temperature, pain, distension | Review within days of starting | Not improving or signs of severe disease → hospital assessment; relapse within 12 weeks → fidaxomicin (NICE NG199) |
| Loperamide (if used) | Quantity used; OTC purchases; cardiac symptoms | Each review | Exceeding maximum dose, palpitations or syncope → stop and assess (MHRA, Sept 2017) |
| Children (CG84) | Dehydration signs, urine output, weight | Same day if concern | Red-flag signs → specialist assessment; shock → emergency. Diarrhoea >7 days or vomiting >3 days → review |
- Prescribing loperamide to a red-flag/bloody-diarrhoea patient instead of investigating
- No public-health/exclusion advice in infective cases
- No safety-net or result follow-up
Who you are
Trevor Hughes, 58. About 6 weeks of looser, more frequent stools (3–4 times a day), sometimes urgent. You assumed it was a stomach bug that's hung around. If asked, you've lost about 5kg without trying, seen some blood mixed in once or twice, and feel more tired than usual. No foreign travel, no recent antibiotics, no obviously unwell contacts. Your father had bowel cancer in his 60s. You eat normally (including bread/pasta). You came hoping for something to settle your stomach and didn't really want a fuss.
Hidden concerns (reveal if explored)
Cancer fear (main, often unspoken): your dad's bowel cancer is at the back of your mind; you've half-avoided thinking about the blood. If the doctor is calm and thorough, you're relieved to be taken seriously.
Embarrassment: you're a bit reluctant to talk about blood/the back passage but will if the doctor is matter-of-fact.
Wanting a quick fix: you'd prefer a tablet, but accept investigation when the reasoning is explained.
Clinical details if asked
- ~6 weeks looser/more frequent stools, urgency; blood mixed in once or twice; ~5kg unintentional weight loss; increased fatigue
- No travel, no recent antibiotics/PPI, no clear unwell contacts, no fever
- Father had bowel cancer in his 60s; you eat gluten normally
- No severe pain; tolerating fluids; passing urine normally (not dehydrated)
- On examination: happy to consent to abdominal and PR exam with a chaperone
Reactions at key moments
- On "six weeks is too long for a bug": pauses, takes it on board.
- On the FIT/bloods/referral: slightly anxious but reassured by the calm, clear explanation.
- On the family history being mentioned: admits it's been worrying you.
- On PR exam: a bit embarrassed but consents when it's explained.
- Challenge line: "Can't you just give me something to stop it? I'm sure it's nothing serious."
Resolution: Trevor is well served if the GP: (1) refuses to inherit the "bug" label, recognising 6 weeks of changed bowel habit with weight loss, rectal bleeding, fatigue and a family history as a colorectal-cancer red-flag presentation; (2) screens the red flags, examines (abdomen + PR), and arranges FIT + bloods (FBC/ferritin/coeliac/CRP); (3) refers on the NG12 colorectal pathway and avoids simply prescribing loperamide; (4) explains the reasoning calmly — thorough, not alarmist — and acknowledges the family-history worry; (5) safety-nets and arranges result follow-up. He is poorly served if given an anti-motility and sent away, or falsely reassured it's "just a bug".
Usually infective/self-limiting. Assess dehydration; oral rehydration; no routine antibiotics/stool tests; stool test if bloody/systemic/travel/immunocompromised/public-health. Anti-motility caution (not in bloody/O157/C. diff).
Work-up: FBC/ferritin, CRP, coeliac serology (on gluten), TFTs; FIT; faecal calprotectin (IBD vs IBS). Examine incl. PR.
Persistent change in bowel habit, 50+, rectal bleeding, weight loss, iron-deficiency anaemia, mass → FIT + NICE NG12 colorectal pathway. IBD (bloody/nocturnal, raised calprotectin/CRP) → gastroenterology. Coeliac → confirm + dietitian. IBS = positive diagnosis after excluding red flags. C. diff after antibiotics/PPI → stool + treat. Public-health notification/exclusion for relevant infections.