12-phase flow (12)

1. 1FRAME
   Establish scope — acute colonic diverticulitis episode vs subacute recovery/recurrence review; left-sided vs right-sided; exclude pregnancy/non-colonic mimics requiring divergent pathway (ASCRS 2020; WSES 2020)
   inputs: age, sex
   advance: episode vs recovery context set and pregnancy status known
2. 2ENTRY
   Capture LLQ (or RLQ for right-sided) pain ± fever, altered bowel habit, leukocytosis, or CT trigger; or recurrent-disease problem-list entry for recovery review (AGA CPU 2021)
   advance: one entry trigger present
3. 3CONTEXT
   Vitals, focused HPI (pain location/duration, bowel habit, prior episodes), immunocompromise/transplant/steroid screen, pregnancy, NSAID/opioid/smoking history, allergies, renal function (ASCRS 2020; AGA CPU 2021)
   inputs: age, sex, temperature, hr, sbp, creatinine, immunocompromise, prior_episodes, pregnancy_status
   actions: panel.cmp
   advance: vitals + key history + comorbidity/immune status captured
4. 4RED_FLAGS
   Screen generalised peritonitis, free air, septic shock, immunocompromise with diverticulitis, obstruction, and brisk lower-GI bleed — each forks management away from the outpatient pathway (WSES 2020; ASCRS 2020)
   inputs: sbp, hr, temperature, lactate
   actions: calc.qsofa, protocol.septic_shock, workup.acute_abdomen
   advance: no peritonitis/shock OR escalation route (OR / drainage / ICU) activated
5. 5INITIAL_WORKUP
   CBC + CRP + CMP + lactate + urinalysis + β-hCG; contrast-enhanced CT abdomen/pelvis is the diagnostic standard (sens ~94%, spec ~99%) — confirms Dx, stages modified Hinchey, finds abscess/free air/fistula/obstruction; US/MRI if CT contraindicated (ASCRS 2020; WSES 2020)
   inputs: wbc, crp, lactate, ct_abdomen_pelvis, us_or_mri_abdomen
   actions: workup.diverticulitis, panel.cbc, panel.inflammation, panel.renal
   advance: CT (or US/MRI) + inflammatory markers returned and modified Hinchey stage assigned
6. 6BRANCHING_WORKUP
   Stage-driven branch — uncomplicated (Hinchey 0–Ia) → outpatient pathway; abscess (Ib/II) → size-based IR drainage decision; III/IV peritonitis → emergency surgery; fistula (colovesical workup — CT cystogram/cystoscopy), obstruction (SBO/LBO branch), or lower-GI bleed (distinct sibling) routes (ASCRS 2020; WSES 2020)
   inputs: pneumaturia_fecaluria
   actions: workup.diverticulitis, workup.acute_abdomen, workup.sbo_partial_complete, workup.lgib
   advance: phenotype identified (uncomplicated / abscess / perforation-peritonitis / fistula / obstruction / right-sided / bleed)
7. 7DIFFERENTIAL
   Confirm diverticulitis vs colorectal cancer mimicking diverticulitis (CRC prevalence ~1.9% overall, ~7.9% complicated, ~1.3% uncomplicated — colonoscopy after resolution), IBD, appendicitis (right-sided), ischaemic/infectious colitis, gynaecologic pathology, diverticular bleeding (painless — distinct entity) (AGA CPU 2021; Rottier CGH 2018)
   inputs: ct_abdomen_pelvis
   advance: diverticulitis confirmed or alternative diagnosis routed
8. 8RISK_STRATIFICATION
   Modified Hinchey stage (0/Ia/Ib/II/III/IV) + uncomplicated-vs-complicated fork + host-risk modifiers (immunocompromise, frailty, significant comorbidity, sepsis); CRP >150 mg/L raises complicated probability (Mäkelä 2015 PMID 25665622); qSOFA/SIRS for sepsis (WSES 2020)
   inputs: wbc, crp, sbp
   actions: calc.qsofa, calc.sirs
   advance: Hinchey stage + host-risk tier documented and management fork chosen
9. 9TREATMENT
   Uncomplicated (Hinchey 0–Ia, immunocompetent, tolerating PO): observation + analgesia + clear liquids, selective/NO antibiotics (AVOD PMID 22290281/31386199; DIABOLO PMID 29700480 — equivalent recovery/complications/recurrence). Antibiotics reserved for immunocompromise, sepsis, significant comorbidity, frailty, refractory. Complicated: abscess <4 cm → IV antibiotics; ≥4 cm → IV antibiotics + image-guided percutaneous drainage; Hinchey III/IV → resuscitation + emergency surgery (Hartmann vs primary anastomosis ± diverting loop ileostomy; laparoscopic lavage controversial — SCANDIV/LADIES/DILALA). Anti-patterns enforced: mesalamine/rifaximin/probiotics NOT for prevention (ASCRS 2020; AGA CPU 2021; WSES 2020)
   inputs: creatinine, crp, immunocompromise
   actions: protocol.septic_shock
   advance: stage-appropriate plan executed (observation / oral abx / IV abx ± drainage / emergency surgery)
10. 10DISPOSITION
    Outpatient if Hinchey 0–Ia + immunocompetent + tolerating PO + reliable follow-up + no significant comorbidity; admit for complicated disease / abscess / failure of outpatient management / immunocompromise / inability to take PO; OR for III/IV; ICU for septic shock / faeculent peritonitis (ASCRS 2020; WSES 2020)
    inputs: sbp, immunocompromise
    advance: destination set (home / ward / IR suite / OR / ICU)
11. 11MONITORING
    Outpatient: clinical re-check 48–72 h, return precautions; expect improvement <72 h. Inpatient: vitals q4h, serial abdominal exam, CRP/WBC trend at 48–72 h, repeat imaging if no improvement (failure of drainage / new abscess); post-op recovery (ASCRS 2020; AGA CPU 2021)
    inputs: wbc, crp, temperature
    actions: panel.inflammation
    advance: clinical improvement documented or escalation per failure criteria
12. 12FOLLOWUP
    Subacute recovery: interval colonoscopy 6–8 wk after resolution if no quality colonoscopy within ~1 yr (CRC yield ~1.9%, higher in complicated) — exclude malignancy/IBD; lifestyle (high-fibre diet, physical activity, weight, smoking cessation; nuts/seeds NOT restricted — debunked myth, counsel patient); individualised elective-surgery shared decision (NOT episode count) for smouldering/chronic, fistula, stricture, immunosuppressed, or inability to exclude cancer; chemoprophylaxis anti-pattern (no mesalamine/rifaximin/probiotics) (AGA CPU 2021; ASCRS 2020)
    inputs: recent_colonoscopy, prior_episodes, age
    actions: workup.colorectal_screening, calc.phq9
    advance: interval colonoscopy decision made, lifestyle counselling delivered, elective-surgery decision documented, follow-up scheduled