12-phase flow (12)

1. 1FRAME
   Frame the suspected pediatric appendicitis presentation: age band (< 5 y atypical / 5-10 y / 10-19 y peak / adolescent female with mandatory OB/gyn ddx / adolescent male) drives pretest probability + atypical-presentation index + perforation rate at presentation (~ 80% in < 5 yo; ~ 30% overall; ~ 15-20% in adolescents). Sex + pregnancy status drives mandatory pelvic US + βhCG workup in post-menarchal female. Duration of symptoms drives perforation risk + NOM eligibility (typically < 48 h).
   inputs: age_in_years, sex_at_birth_and_gender_identity, duration_of_symptoms_in_hours
   advance: Age + sex + duration tagged; pretest probability + atypical-presentation framing set; OB/gyn ddx triggered if applicable
2. 2ENTRY
   Recognise via classic clinical features (RLQ pain with anorexia + nausea/emesis + migration from periumbilical region — classic adult triad blunted in peds) OR PAS components (Samuel 2002; 8-component score 0-10) OR atypical presentation (diffuse pain in < 5 yo; pelvic features in adolescent female; flank/back in retrocecal). PAS ≤ 3 low / 4-6 intermediate / ≥ 7 high pretest stratification.
   inputs: pain_pattern_periumbilical_to_rlq_migration, anorexia_pediatric, rlq_tenderness_on_exam
   advance: Appendicitis suspected by clinical features or PAS components or US signature
3. 3CONTEXT
   Age + sex + weight + temperature + vitals + duration of symptoms + pain pattern (paroxysmal vs constant; periumbilical → RLQ migration) + anorexia + nausea/emesis + RLQ tenderness + cough/hopping/percussion tenderness + peritoneal signs + psoas/obturator signs + menstrual + sexual + pregnancy history (post-menarchal female) + prior appendicitis or NOM episode history.
   inputs: age_in_years, sex_at_birth_and_gender_identity, weight_kg, temperature_pediatric, hr_pediatric, capillary_refill_pediatric, pain_pattern_periumbilical_to_rlq_migration, anorexia_pediatric, nausea_emesis_pediatric, rlq_tenderness_on_exam, cough_percussion_or_hopping_tenderness_in_rlq, prior_appendicitis_or_prior_nom_episode, menstrual_history_and_sexual_activity_for_adolescent_female, pregnancy_status_for_female_patient
   advance: PAS components captured; clinical context + risk-factor + sex-specific history documented
4. 4RED_FLAGS
   Perforation / peritonitis (rigidity, guarding, rebound, high-grade fever > 39 °C, free air on imaging) → emergent surgical management; hemodynamic compromise / shock (hypotension by age threshold, tachycardia + poor perfusion, capillary refill > 3 s, mottling, lactate ≥ 4) → ICU + IVF + pediatric surgery NOW; routes to id.sepsis.peds.v1 if Phoenix-2024 criteria met. Atypical-age < 5 yo with any clinical concern → aggressive imaging + surgical consult given ~ 80% perforation rate at presentation. Pregnant patient → multidisciplinary peds surgery + OB + MFM.
   inputs: sbp_pediatric, peritoneal_signs_rigidity_guarding_rebound, temperature_pediatric
   advance: Surgical-emergency criteria evaluated; resuscitation initiated if needed; multidisciplinary consults triggered
5. 5INITIAL_WORKUP
   IV access + NPO + analgesia (morphine 0.05-0.1 mg/kg IV PRN; does NOT obscure abdominal exam) + antiemetic (ondansetron 0.15 mg/kg IV); CBC with diff + CRP + metabolic panel + urinalysis + urine/serum βhCG (mandatory in post-menarchal female); abdominal US first-line (sensitivity ~ 88%, specificity ~ 94% — Doria 2006); PAS scoring documented; pediatric surgery consult triggered based on PAS bucket and imaging. Pelvic US mandatory in adolescent female.
   inputs: cbc_with_diff_pediatric, crp_pediatric, metabolic_panel_pediatric, urinalysis_pediatric, urine_or_serum_bhcg_for_female, abdominal_ultrasound_pediatric_first_line
   actions: panel.cbc, panel.renal
   advance: IV access + NPO + analgesia given; labs + βhCG + US obtained; PAS bucket documented; surgical consult initiated if PAS ≥ 7 or imaging-positive
6. 6BRANCHING_WORKUP
   Source-directed: MRI if US non-diagnostic + persistent clinical concern (preferred over CT in peds + pregnancy per ACR Appropriateness Criteria; ALARA); CT if US + MRI unavailable + persistent concern or complex perforation/abscess characterization (low-dose pediatric protocols); pelvic US for adolescent female (ovarian torsion + PID + ectopic + hemorrhagic cyst differentiation); type-and-screen if surgical management likely; lactate if shock physiology suspected; STI workup if sexually active adolescent female with PID features.
   inputs: abdominal_mri_if_us_non_diagnostic, pelvic_ultrasound_for_adolescent_female, type_and_screen_pediatric, lactate_pediatric
   advance: Pre-surgical workup ready if surgical management indicated; alternative diagnoses excluded
7. 7DIFFERENTIAL
   Mesenteric adenitis (post-viral; commonly mimics appendicitis in younger child); acute gastroenteritis (vomiting + diarrhea preceding pain pattern); Meckel's diverticulitis (rare; nuclear medicine scan post-recovery); constipation (KUB shows fecal loading); urinary tract infection (pyuria + bacteriuria); pyelonephritis (CVA tenderness + UA + urine culture); ovarian torsion (adolescent female; pelvic US with Doppler; surgical emergency); pelvic inflammatory disease (sexually active adolescent female; cervical motion tenderness; CDC 2021 STI); ectopic pregnancy (positive βhCG; pelvic US); ruptured / hemorrhagic ovarian cyst (pelvic US); mittelschmerz / dysmenorrhea (physiologic; menstrual history); diabetic ketoacidosis (rare presentation with abdominal pain; check BG); inflammatory bowel disease (chronic pattern); intussusception (younger band 6 mo - 3 y; target sign on US — `peds.intussusception.v1`).
   advance: Mimics excluded by US + βhCG + clinical features; appendicitis diagnosis confirmed or alternative pathway entered
8. 8RISK_STRATIFICATION
   Tier 1 (life-threatening — emergent surgery): perforation with free air + peritonitis + hemodynamic compromise / shock. Tier 2 (severe — image-guided drainage OR emergent surgery): perforated with organized abscess in stable patient; atypical age < 5 yo with ~ 80% perforation rate; PAS ≥ 7 high-pretest with high-grade fever + leukocytosis. Tier 3 (severe — surgical management standard): PAS ≥ 7 + imaging-positive uncomplicated; family declines NOM. Tier 4 (moderate — imaging + decision branch): PAS 4-6 intermediate; US first-line; MRI/CT if non-diagnostic. Tier 5 (mild — discharge/observe): PAS ≤ 3 low; NPV ~ 95%; return precautions or observation × 12-24 h. Tier 6 (NOM): uncomplicated + no abscess + no fecalith + symptoms < 48 h + hemodynamically stable + family/patient prefers NOM (Minneci 2020 + APSA 2020). Adolescent female: OB/gyn ddx workup mandatory. Pregnant patient: multidisciplinary peds surgery + OB + MFM.
   inputs: age_in_years, duration_of_symptoms_in_hours, sbp_pediatric, peritoneal_signs_rigidity_guarding_rebound, pregnancy_status_for_female_patient
   advance: Tier assigned + medical/surgical/NOM pathway chosen + admit vs OR vs discharge vs observation decision documented
9. 9TREATMENT
   Pre-op resuscitation: isotonic IV fluid (NS 20 mL/kg over 30-60 min, repeat × 1-2 PRN; max ~ 60 mL/kg total before reassessing for fluid overload) + NPO + analgesia (morphine 0.05-0.1 mg/kg IV PRN) + antiemetic (ondansetron 0.15 mg/kg IV). Pre-op antibiotic single dose at induction: ceftriaxone 50 mg/kg IV + metronidazole 10 mg/kg IV OR pip-tazo 80-100 mg/kg IV (pip component) single dose. Laparoscopic appendectomy is standard for uncomplicated cases (timing within 12-24 h; no benefit to emergent < 6 h surgery if antibiotic cover in place); open appendectomy reserved for complicated or hemodynamically unstable. Perforated appendicitis: emergent surgery (free perforation + peritonitis + shock; within 6-12 h) OR image-guided drainage of organized abscess in stable patient → interval appendectomy 6-8 weeks; broad-spectrum antibiotics × 5-7 d post-op (pip-tazo OR ceftriaxone + metronidazole; vancomycin add-on if MRSA risk). NOM: amoxicillin-clavulanate 25-45 mg/kg/day PO × 7 d OR pip-tazo IV × 24-48 h → PO step-down; eligibility uncomplicated + no abscess + no fecalith + symptoms < 48 h + hemodynamically stable + family/patient prefers NOM (Minneci 2020 + APSA 2020).
   inputs: weight_kg, sbp_pediatric, abdominal_ultrasound_pediatric_first_line
   actions: panel.renal
   advance: Resuscitation complete; pre-op antibiotics given; surgical management OR NOM pathway chosen; post-op or post-NOM monitoring plan in place
10. 10DISPOSITION
    Uncomplicated laparoscopic appendectomy → inpatient ward 24-48 h LOS; perforated appendicitis → inpatient ward 5-7 d LOS OR PICU if septic / hemodynamically unstable; NOM → outpatient or short admission 24 h IV → discharge home with PO antibiotics + structured follow-up (24-48 h, 7 d, 1-3 months); observation for PAS 4-6 imaging-equivocal → 12-24 h re-eval with repeat exam ± imaging.
    inputs: sbp_pediatric
    advance: Disposition + level of care set; post-op or NOM monitoring plan in place
11. 11MONITORING
    Post-op uncomplicated: vitals q4h × first 24 h then per protocol; serial abdominal exams q4h; diet advance from clear liquids → regular as tolerated; pain management with transition to PO acetaminophen ± ibuprofen ± opioids PRN; wound inspection daily; early ambulation; bowel function (flatus + first BM) documented before discharge. Post-op perforated: as above + IV antibiotic course continuation × 5-7 d + drain monitoring if applicable + serial labs (CBC + CRP + metabolic panel) + watch for post-op abscess (rising CRP + persistent fever + worsening exam → CT for evaluation). NOM: vitals q2-4h first 24 h; serial abdominal exams; CRP + WBC trend; transition to PO antibiotics; discharge home with structured follow-up; family education on return precautions (return of pain, fever, vomiting → ED).
    inputs: rlq_tenderness_on_exam, temperature_pediatric
    advance: Recovery progressing; diet advanced; pain controlled; discharge criteria approaching
12. 12FOLLOWUP
    Post-op uncomplicated: pediatric surgery follow-up at 2-4 weeks for wound check + scar inspection + bowel function review; activity progression per surgeon; school return typical 1-2 weeks. Post-op perforated: pediatric surgery follow-up at 2-4 weeks; pediatric infectious disease follow-up if prolonged antibiotic course; nutrition follow-up if extensive resection. NOM: structured pediatric surgery + pediatrician follow-up at 24-48 h, 7 d, 1-3 months; ~ 30% recurrence within 1 year (Minneci 2020) → re-presentation pathway with low threshold for surgical management; family education on recurrence signs (return of RLQ pain, fever, vomiting → ED). Interval appendectomy 6-8 weeks if abscess drained (no consensus on optimal timing; centers vary 4-12 weeks). Adolescent female: ongoing primary care + gyn follow-up if indicated. Pregnant patient: ongoing OB + MFM follow-up; preterm labor surveillance.
    advance: Follow-up scheduled + return precautions delivered + interval appendectomy queued if abscess drained