12-phase flow (12)

1. 1FRAME
   Establish scope — acute (≤14 d) infectious diarrhoea, adult vs pediatric; set the watery-vs-inflammatory and dehydration-severity frame; persistent (>14 d) or surgical-abdomen/IBD mimic forks to a different pathway (IDSA 2017 PMID 29053792; ACG 2016 PMID 27068718)
   inputs: age, symptom_duration
   advance: acute infectious-diarrhoea context confirmed and adult/pediatric set; persistent/mimic rerouted
2. 2ENTRY
   Capture acute diarrhoea ± vomiting, bloody/dysenteric stool, fever + diarrhoea, vomiting-predominant food poisoning, returning traveller, or recent antibiotic/healthcare exposure (C. diff trigger) (IDSA 2017 PMID 29053792)
   advance: one entry trigger present
3. 3CONTEXT
   Age/weight (pediatric dosing), pregnancy, immunocompromise, recent antibiotics/hospitalisation (C. diff), travel, food/sick-contact/outbreak exposure, comorbidity, vitals + vomiting severity; baseline renal/hepatic function for drug dosing (IDSA 2017 PMID 29053792; ISTM/IDSA 2017 PMID 28521004)
   inputs: age, weight, pregnancy_status, hr, sbp, temperature, vomiting_severity, immunocompromise, recent_antibiotic_healthcare_exposure, travel_history, food_exposure_outbreak, comorbidity
   actions: panel.cmp, cascade.labs_command
   advance: vitals + host-risk + exposure history captured
4. 4RED_FLAGS
   Screen severe dehydration/hypovolaemic shock, sepsis/septic shock from invasive enteric infection, bloody diarrhoea + high fever + severe pain/tenesmus (dysentery), suspected STEC/HUS (bloody stool + low/no fever + oliguria + pallor → AVOID antibiotics & antimotility), volume-depletion AKI, intractable vomiting, immunocompromised host (IDSA 2017 PMID 29053792; Wong NEJM 2000 PMID 10874060)
   inputs: sbp, hr, temperature, urine_output, dehydration_signs, bloody_stool
   actions: calc.qsofa, calc.sirs, protocol.septic_shock
   advance: no red flag OR escalation route (IV resuscitation / sepsis bundle / STEC-safe pathway / admission) activated
5. 5INITIAL_WORKUP
   Most cases: clinical only — NO routine stool testing, NO antibiotics (viral self-limited; ACG 2016 PMID 27068718). Test only if inflammatory/bloody/febrile/severe/immunocompromised/traveller/public-health/persistent: stool multiplex PCR (preferred — sens ≥94.5%/spec ≥97%, Buss PMID 25588652) vs culture, Shiga-toxin/STEC, fecal leukocytes/lactoferrin/calprotectin (limited), O&P selectively, C. diff toxin/NAAT if antibiotic/healthcare exposure; CBC/CMP/electrolytes/creatinine/lactate + blood cultures if severe/septic/immunocompromised (IDSA 2017 PMID 29053792)
   inputs: creatinine, electrolytes, cbc, lactate, stool_studies
   actions: workup.acute_diarrhea, panel.cbc, panel.cmp, panel.renal, panel.inflammation
   advance: supportive-only pathway chosen OR targeted stool/lab studies sent
6. 6BRANCHING_WORKUP
   Branch by pivot — watery/non-febrile → supportive, no testing; inflammatory/dysenteric → culture/PCR + consider empiric azithromycin (NOT if STEC suspected); traveller → ETEC/EAEC/protozoal pathway; vomiting-predominant → toxin food poisoning vs acute-vomiting workup; recent abx/healthcare → fulminant-CDI workup; persistent >14 d → chronic-diarrhoea workup; returning-traveller fever → enteric-fever/malaria rule-out (IDSA 2017 PMID 29053792; ISTM/IDSA 2017 PMID 28521004; IDSA/SHEA 2021 PMID 34164674)
   inputs: bloody_stool, travel_history, recent_antibiotic_healthcare_exposure, symptom_duration
   actions: workup.acute_diarrhea, workup.acute_vomiting, workup.fulminant_cdiff, workup.returning_traveler_fever, workup.chronic_diarrhea
   advance: phenotype identified (viral-watery / inflammatory-bacterial / toxin food poisoning / traveller / C. diff / persistent)
7. 7DIFFERENTIAL
   Viral AGE (commonest) vs inflammatory bacterial (Salmonella/Shigella/Campylobacter/STEC/Yersinia/Vibrio) vs preformed-toxin food poisoning vs traveller's (ETEC/EAEC/protozoal) vs C. difficile vs non-infectious mimics (early IBD/UC flare, ischaemic colitis, appendicitis with diarrhoea, DKA/thyrotoxicosis, medication/laxative, overflow, HUS/TTP) (IDSA 2017 PMID 29053792; ACG 2016 PMID 27068718)
   inputs: bloody_stool, stool_studies
   advance: infectious AGE phenotype confirmed or alternative diagnosis routed
8. 8RISK_STRATIFICATION
   Dehydration severity tier (mild/moderate/severe — pediatric % weight loss) + sepsis screen (qSOFA/SIRS) + volume-depletion AKI (CKD-EPI 2021) + host-risk modifiers (age extremes, immunocompromise, comorbidity, pregnancy) → disposition + antibiotic decision (IDSA 2017 PMID 29053792; ESPGHAN/ESPID 2014 PMID 24739189)
   inputs: dehydration_signs, sbp, hr, creatinine, immunocompromise
   actions: calc.qsofa, calc.sirs, calc.ckd_epi_2021
   advance: severity tier + host-risk documented and management/disposition fork chosen
9. 9TREATMENT
   Rehydration cornerstone: reduced-osmolarity ORS for mild-moderate (unscheduled-IV OR 0.61, Hahn PMID 11869639); IV isotonic crystalloid (LR/NS) for severe/shock — deficit + maintenance + ongoing losses. Early refeeding, continue breastfeeding. Ondansetron for vomiting limiting ORS (peds ED — OR 0.28 cessation, OR 2.93 avoiding admission; Freedman PMID 16625009, Niño-Serna PMID 32132152; QT caution). Selective antimicrobials: empiric azithromycin (febrile dysentery / moderate-severe traveller's), ciprofloxacin where susceptible, ceftriaxone for severe/bacteraemic/enteric fever/pregnancy, rifaximin (non-invasive traveller's); pathogen-directed de-escalation. Zinc (pediatric LMIC). Loperamide/bismuth ONLY for mild non-bloody non-febrile. C. diff → oral vancomycin/fidaxomicin via dedicated pathway. Anti-patterns enforced: NO empiric abx in STEC (HUS RR 14.3 — Wong PMID 10874060); NO antimotility in dysentery/C.diff/peds-bloody (IDSA 2017 PMID 29053792; ACG 2016 PMID 27068718; ISTM/IDSA 2017 PMID 28521004)
   inputs: dehydration_signs, creatinine, pregnancy_status, bloody_stool, vomiting_severity
   actions: protocol.septic_shock, cascade.fluid, cascade.electrolyte
   advance: rehydration route executed, antiemetic/antimicrobial decision made (incl. anti-pattern exclusions), C. diff routed if applicable
10. 10DISPOSITION
    Outpatient with ORS + return precautions for most (mild-moderate, tolerating PO, no red flag); admit for severe dehydration/shock, sepsis, AKI, intractable vomiting, inability to maintain hydration, significant comorbidity, immunocompromise, social; ICU for septic shock / fulminant disease. Public-health reportable pathogens + outbreak/food-handler considerations (IDSA 2017 PMID 29053792; ACG 2016 PMID 27068718)
    inputs: dehydration_signs, sbp, immunocompromise, vomiting_severity
    advance: destination set (home / ward / ICU) and public-health reporting addressed
11. 11MONITORING
    Hydration status / urine output / weight (pediatric), electrolytes + renal function (AKI, antibiotic dosing), clinical course/response, antibiotic stewardship + QT with ondansetron, HUS surveillance (CBC/smear/creatinine) if STEC, response to de-escalation (IDSA 2017 PMID 29053792; Wong NEJM 2000 PMID 10874060)
    inputs: dehydration_signs, urine_output, creatinine, electrolytes, cbc
    actions: panel.renal, panel.cbc, cascade.electrolyte
    advance: clinical improvement documented or escalation per failure/HUS criteria
12. 12FOLLOWUP
    Most: complete recovery, return precautions, hygiene/food-safety counselling, no routine test-of-cure; public-health reporting + food-handler clearance for reportable pathogens; persistent/post-infectious symptoms → reassess (post-infectious IBS — gi.ibs.core.v1; persistent → chronic-diarrhoea workup); rotavirus-vaccine context (pediatric) (IDSA 2017 PMID 29053792; ACG 2016 PMID 27068718)
    inputs: symptom_duration, food_exposure_outbreak, age
    actions: workup.chronic_diarrhea, calc.phq9
    advance: recovery confirmed or persistent/post-infectious pathway routed, public-health/food-handler addressed, follow-up scheduled