Acute Cholangitis & Cholecystitis — fellow's quick read

Personal study digest for a new ID fellow. Recommendations are from the cited guideline; the “What’s changed since 2018” section is reviewer synthesis of newer evidence, each claim cited. Not a substitute for the full guideline.

Sources digested: Gomi et al. J Hepatobiliary Pancreat Sci 2018;25:3–16 (DOI); Michigan Medicine Intra-abdominal Infection CPG 2023 (local practice comparison)

In one line

TG18 severity grading (I–III) drives empiric antibiotic selection; source control (ERCP for cholangitis, cholecystectomy for cholecystitis) is definitive, and antibiotics run 4–7 days after adequate drainage.

When to suspect / diagnose

Cholangitis: Charcot triad (fever, jaundice, RUQ pain). TG18 diagnostic criteria require systemic inflammation (fever >38°C or WBC >10k or CRP ≥1) + cholestasis or biliary imaging findings.
Cholecystitis: Murphy sign + fever + imaging (gallbladder wall thickening, pericholecystic fluid).
Severity grading matters for antibiotic selection:
- Grade I (mild) — no organ dysfunction, no criteria for Grade II.
- Grade II (moderate) — any of: WBC >18k or <4k, fever ≥39°C, age ≥75, bilirubin ≥5 mg/dL, albumin <0.7×LLN.
- Grade III (severe) — organ dysfunction in any system (cardiovascular, neurological, respiratory, renal, hepatic, hematologic).

Workup the fellow drives

Blood cultures: obtain before antibiotics in Grade II–III cholangitis and Grade II–III cholecystitis. TG18 does not recommend routine blood cultures for Grade I cholecystitis.
Bile cultures: obtain at every biliary procedure (ERCP, PTC, surgery). Common pathogens: E. coli, Klebsiella, Enterococcus, Enterobacter; anaerobes when biliary-enteric anastomosis.
Imaging: abdominal ultrasound first; MRCP or CT if diagnostic uncertainty. ERCP is therapeutic, not primarily diagnostic.

Empiric & definitive therapy

Cholangitis

Severity	Drug / dose / route	Notes
Grade I (mild)	Cefazolin 1–2 g IV q8h, or ceftriaxone 1–2 g IV q24h, or cefotaxime 1–2 g IV q6–8h; ± metronidazole 500 mg IV q8h Alternatives: ertapenem 1 g IV q24h; fluoroquinolone (only if susceptibility confirmed)	Metronidazole only if biliary-enteric anastomosis. FQ only if local E. coli susceptibility known — ESBL strains are often FQ-resistant.
Grade II (moderate)	Pip-tazo 4.5 g IV q6–8h, or ceftriaxone/cefepime/ceftazidime ± metronidazole, or ertapenem 1 g IV q24h	Broader coverage needed. Ertapenem is a reasonable single agent for community-acquired Grade II.
Grade III (severe)	Pip-tazo 4.5 g IV q6h, or cefepime/ceftazidime ± metronidazole, or imipenem 500 mg IV q6h / meropenem 1 g IV q8h ± vancomycin (if Enterococcus suspected)	Add vancomycin for suspected Enterococcus (post-biliary surgery, stent, prior cultures). Carbapenems preferred if ESBL risk.
Healthcare-associated	Same as Grade III + consider VRE coverage (linezolid or daptomycin) if risk factors	VRE risk: prior VRE colonization, liver transplant, prolonged hospitalization. Michigan CPG limits VRE coverage to critically ill liver transplant, prior VRE IAI, or septic shock + VRE colonization.

Cholecystitis

Severity	Drug / dose / route	Notes
Grade I–II	Cefazolin 1–2 g IV q8h, or ceftriaxone 1–2 g IV q24h ± metronidazole	Antibiotics are perioperative only. Discontinue within 24 h of cholecystectomy. Rec 1, level B.
Grade III	Pip-tazo 4.5 g IV q6h, or cefepime/ceftazidime ± metronidazole, or carbapenem	Treat 4–7 days. Rec 2, level D.

Oral step-down

When clinically improved and tolerating PO: fluoroquinolone (if susceptible), amoxicillin-clavulanate, or cephalexin ± metronidazole.

Key prescribing guardrails

Ampicillin-sulbactam: NOT recommended if local E. coli resistance >20%.
Fluoroquinolones: only if susceptibility documented. ESBL producers are frequently FQ-resistant. Michigan CPG notes E. coli FQ susceptibility is only 74% at their institution.
Anaerobic coverage (metronidazole): add for biliary-enteric anastomosis or emphysematous cholecystitis.

Duration & stopping

Cholangitis after adequate drainage: 4–7 days. Rec 1, level C.
Cholecystitis Grade I–II post-cholecystectomy: discontinue antibiotics within 24 hours. Rec 1, level B.
Cholecystitis Grade III: 4–7 days. Rec 2, level D.
Gram-positive bacteremia (Enterococcus, Streptococcus): minimum 2 weeks.
Bacteremia (general): Michigan CPG recommends 7–14 days, with shorter 7-day course acceptable if source controlled + transient + clinical criteria met.
Post-ERCP: Michigan CPG recommends 4 days post-procedure for uncomplicated cholangitis.

Key decisions a fellow owns

Source control timing: ERCP within 24–48 h for Grade II–III cholangitis. Urgent (<12 h) for Grade III with organ failure not responding to initial management.
De-escalation: narrow antibiotics once bile and blood culture results return. Do not broaden for bile culture isolates alone if patient is improving on current regimen.
When to add anti-enterococcal coverage: Grade III with prior biliary instrumentation, biliary stent, or prior enterococcal cultures. Do not add empirically for Grade I.
ESBL risk assessment: prior ESBL isolation, healthcare-associated, recent cephalosporin/FQ use → start carbapenem empirically.
Oral step-down: transition when afebrile ≥24 h, tolerating PO, WBC trending down. Check susceptibility before choosing oral agent.

What’s changed since 2018

Reviewer synthesis — not the guideline. Each item cited.

Short-course antibiotics are non-inferior: An RCT of 4 days vs 8 days in moderate-to-severe cholangitis (N=120) showed equivalent clinical cure (78% vs 80%) and no difference in mortality. Supports treating at the lower end of TG18’s 4–7 day range. Srinu et al. Am J Gastroenterol 2024;119:176–182. DOI PMID 37732816
Ultra-short (1-day) courses under active investigation: The COBRA trial (N=410, 31 centers, Netherlands) testing 1 day vs 4–7 days after adequate ERCP drainage has completed enrollment; results pending. The BOLT-P3 trial (N=210, Japan) is testing 1–3 days vs 4–7 days. COBRA: Overdevest et al. Trials 2026;27(1). DOI PMID 41689066, NCT05750966. BOLT-P3: Masuda et al. Trials 2025;26:324. DOI PMID 40890775
Blood culture alone may suffice for guiding therapy: An RCT (N=428, 12 centers, South Korea) showed blood-culture-only guided antibiotic adjustments were non-inferior to blood + bile culture for organ failure rates in mild-to-moderate cholangitis, with shorter antibiotic duration (−1.5 days) and shorter hospital stay (−1.9 days). Tempers TG18’s emphasis on bile cultures as essential for antibiotic adjustment. Lee et al. Clin Microbiol Infect 2025;31:987–994. DOI PMID 39880122
Early oral switch feasible in bacteremic cholangitis: A small RCT (N=59) showed early IV-to-oral switch was non-inferior to conventional 10-day IV therapy for cholangitis with bacteremia (eradication 93% vs 93%). Predates TG18 but TG18 does not prominently endorse this approach. Park et al. Dig Dis Sci 2014;59:2790–6. DOI PMID 24898101
SIS 2024 IAI guideline update published: The Surgical Infection Society published a comprehensive update covering antimicrobial selection, duration, de-escalation, and stewardship for all IAI including biliary infections. Uses GRADE methodology. The 2010 SIS/IDSA joint guideline is now replaced on the surgical side. Huston et al. Surg Infect 2024;25:419–435. DOI PMID 38990709
IDSA 2024 update (Part 1 only): IDSA published Part 1 of the complicated IAI guideline update (diagnostic imaging of appendicitis). The treatment portion (Part 2) is forthcoming — TG18 cholangitis treatment recommendations have not been superseded by IDSA. Bonomo et al. Clin Infect Dis 2024;79(Suppl 3):S94–S103. DOI PMID 38963819
Still current: TG18 severity grading remains standard. Empiric regimen tiers are broadly consistent with SIS 2024 and the Michigan CPG. No newer Tokyo Guidelines version has been published; TG18 remains operative.
Open: Optimal duration in Grade III cholangitis with septic shock lacks a dedicated RCT. The role of newer beta-lactam/beta-lactamase inhibitor combinations (ceftazidime-avibactam, ceftolozane-tazobactam) in biliary CRE infections remains limited to case series.

Anki cards minted this run

F: What antibiotic duration does TG18 recommend for acute CHOLANGITIS after adequate biliary drainage? B: 4–7 days.
A 2024 RCT (Srinu, AJG) showed 4 days non-inferior to 8 days in moderate-severe cholangitis; treat at the SHORT end of TG18’s range when source controlled.
F: When should antibiotics be DISCONTINUED after cholecystectomy for Grade I–II acute cholecystitis? B: Within 24 HOURS post-cholecystectomy.
TG18 Rec 1, level B. Multiple RCTs confirm post-operative antibiotics add no benefit in uncomplicated acute cholecystitis.
F: When does TG18 recommend adding empiric METRONIDAZOLE to biliary infection coverage? B: When a biliary-ENTERIC ANASTOMOSIS is present (or emphysematous cholecystitis).
Intact sphincter of Oddi keeps anaerobes out; a prior hepaticojejunostomy or Whipple breaks that barrier.
F: Why does TG18 restrict empiric FLUOROQUINOLONE use in biliary infections to cases with confirmed susceptibility? B: Because ESBL-producing Enterobacterales — increasingly common in biliary infections — are frequently FQ-RESISTANT.
Michigan CPG reports E. coli FQ susceptibility only 74%. A FQ prescribed empirically may miss the dominant pathogen.

Sources

1. Gomi H, Solomkin JS, Schlossberg D, et al. Tokyo Guidelines 2018: antimicrobial therapy for acute cholangitis and cholecystitis. J Hepatobiliary Pancreat Sci 2018;25:3–16. DOI
2. Michigan Medicine Intra-abdominal Infection CPG 2023 (institutional; no DOI).
3. Srinu D, Shah J, Jena A, et al. Conventional vs short duration of antibiotics in patients with moderate or severe cholangitis: noninferiority RCT. Am J Gastroenterol 2024;119:176–182. DOI PMID 37732816
4. Lee TS, Choi JH, Lee JM, et al. A randomized non-inferiority trial investigating antibiotic adjustments based on blood culture in acute cholangitis. Clin Microbiol Infect 2025;31:987–994. DOI PMID 39880122
5. Overdevest AG, Sieswerda E, Haal S, et al. COBRA trial: 1 day vs 4–7 days antibiotic for acute cholangitis after ERCP — study protocol. Trials 2026;27(1). DOI PMID 41689066
6. Masuda S, Imamura Y, Kimura K, et al. BOLT-P3 trial: short-term antibiotic treatment in acute cholangitis — study protocol. Trials 2025;26:324. DOI PMID 40890775
7. Park TY, Choi JS, Song TJ, et al. Early oral antibiotic switch vs conventional IV therapy for acute cholangitis with bacteremia. Dig Dis Sci 2014;59:2790–6. DOI PMID 24898101
8. Huston JM, Barie PS, Dellinger EP, et al. SIS Guidelines on the Management of Intra-Abdominal Infection: 2024 Update. Surg Infect 2024;25:419–435. DOI PMID 38990709
9. Bonomo RA, Tamma PD, Abrahamian FM, et al. 2024 IDSA CPG Update on Complicated IAI: Diagnostic Imaging. Clin Infect Dis 2024;79(Suppl 3):S94–S103. DOI PMID 38963819