Complicated urinary tract infection

Personal study digest for a new ID fellow. Recommendations are drawn from the 2025 IDSA cUTI guideline series and localized with the Michigan Medicine UTI CPG (rev 03/2026) and our Complicated UTI CPG (rev 04/2026). The "What's changed" section is reviewer synthesis of newer evidence, each claim cited. Not a substitute for the full guideline.

In one line

The 2025 IDSA guideline is the first dedicated cUTI guideline and redefines "complicated" as infection extending BEYOND the bladder (systemic features) — not by sex or comorbidity. The fellow's three moves: pick a severity-matched empiric agent, switch IV→PO early, and treat short (≈7 days).

◆When to suspect / diagnose

What makes it "complicated" now = systemic / beyond-bladder features: fever, chills/rigors/hemodynamic instability, flank pain, or CVA tenderness. Pyelonephritis and catheter-associated UTI with systemic symptoms are included.
Sex and comorbidity no longer define it. Diabetes, immunocompromise, a urologic abnormality, and male sex do NOT by themselves make a UTI complicated — both men and women can have an uncomplicated UTI (a real departure from the old framing).
Diagnosis still needs symptoms + UA + culture. Pyuria, nitrites, leukocyte esterase, and a positive culture are NOT diagnostic on their own; a negative UA helps rule UTI out. AMS without urinary symptoms is not an indication to culture or treat.
ASB is not UTI — don't treat a positive culture without symptoms (exceptions: pregnancy, or before a urologic procedure with anticipated mucosal bleeding).
S. aureus in the urine without recent instrumentation should prompt a hunt for hematogenous seeding / S. aureus bacteremia.

◆Workup the fellow drives

Replace an existing catheter BEFORE culturing; never culture from the drainage bag. ≥3 organisms suggests contamination.
Review prior cultures (last 3–6 months) — they steer empiric choice and the "avoid what was previously resistant" rule.
Imaging only if not improving — CT if symptoms persist/worsen beyond 72 h or there is concern for stone, obstruction, or abscess; ultrasound preferred in pregnancy / transplant. (IDSA's formal imaging recommendation — clinical question 4 — was not in the released installments yet.)

◆Empiric & definitive therapy

IDSA's empiric logic is a 4-step read: severity → recent cultures → patient-specific risks → local antibiogram. Doses below are the local (our institution/Michigan) defaults for normal renal function.

Scenario	Drug / dose / route	Notes
cUTI, NOT septic, no MDRO risk	Ceftriaxone 2 g IV daily (or oral FQ / TMP-SMX if stable enough for outpatient)	IDSA: 3rd/4th-gen cephalosporin, pip-tazo, or a FQ — NOT carbapenems or novel agents
Septic / septic shock	Cefepime 2 g IV q8h (extended infusion); meropenem if moderate–severe penicillin allergy	Carbapenems reserved for SEPSIS (or MDRO)
ESBL risk / known ESBL	Ertapenem (non-septic) · meropenem (septic, or ESBL + Pseudomonas)	Carbapenem = drug of choice for ESBL; CRE / DTR-Pseudomonas / VRE → ID consult
Oral step-down (preferred)	FQ — cipro 500 mg PO q12h or levo 750 mg PO daily · or TMP-SMX 1 DS PO q12h (2 DS if bacteremic)	High bioavailability + good urinary/tissue levels; preferred for bacteremia, ESBL, and male febrile UTI
Oral β-lactam (only if FQ/TMP-SMX unusable)	Amox-clav 875 mg PO q8h · cefpodoxime 400 mg PO q12h	Less reliable — needs source control, ≥3 d prior IV, and ID input
AVOID in cUTI	Nitrofurantoin · oral fosfomycin	Do not reach renal parenchyma / blood — appropriate for cystitis only

◆Duration & stopping

cUTI: 5–7 days of a fluoroquinolone, or 7 days of a non-fluoroquinolone.
Gram-negative bacteremia (urinary source): 7 days.
Men with febrile UTI + suspected acute prostatitis: 10–14 days (evidence to guide this subgroup is thin).
Count duration from the first effective agent (IV days included). Obstruction, indwelling catheter/stent, poorly controlled diabetes, AKI/CKD, and transplant raise failure risk and warrant closer monitoring but do NOT mandate a longer course — the local exception is renal-transplant cUTI (≥14 d, ID consult per Michigan/our institution).

◆Key decisions a fellow owns

Don't treat ASB; kill the reflexive "AMS → urine culture." Diagnostic stewardship is the highest-yield move in UTI.
Source control — remove/replace the catheter; relieve obstruction (urology for obstructive cUTI; ID + urology for perinephric abscess).
Switch IV→PO once improving + tolerating PO + an effective oral agent exists — do not reflexively finish a full IV course.
ID consult for MDROs (CRE, DTR-Pseudomonas, VRE) and for the patient who is not improving (re-check bug–drug match, unresolved source, and the diagnosis itself).

What's changed (vs the prior 2010 IDSA UTI guideline)

Reviewer synthesis of newer evidence — not the guideline. Each claim cited.

First dedicated IDSA cUTI guideline — and the first to address men. The 2010 document covered only uncomplicated cystitis/pyelonephritis in women. cUTI is now classified by systemic vs localized presentation, aligning with the EUA's 2025 reclassification. CID 2025 (doi:10.1093/cid/ciaf459) · Bonkat, Eur Urol Open Sci 2025;75:44 (doi:10.1016/j.euros.2025.03.010)
IV→oral switch now explicitly endorsed for cUTI including pyelonephritis and bacteremic UTI — efficacy depends on therapeutic levels, not the route. Old practice assumed a full IV course. CID 2025 (doi:10.1093/cid/ciaf461)
Short courses are standard — 7 days even WITH gram-negative bacteremia. Reinforced by BALANCE: 7 d non-inferior to 14 d for bloodstream infection (90-d death 14.5% vs 16.1%), and the urinary tract was the commonest source (42%). NEJM 2024 (doi:10.1056/NEJMoa2404991; PMID 39565030)
Empiric choice is severity-stratified. Reserve carbapenems for septic cUTI; reserve novel β-lactam/β-lactamase-inhibitors, cefiderocol, and plazomicin for documented resistance — not empiric use. CID 2025 (doi:10.1093/cid/ciaf460)
A new cUTI agent the guideline's evidence base just predates: cefepime-enmetazobactam (Exblifep) — FDA-approved 22 Feb 2024 for cUTI/pyelonephritis, non-inferior and superior to pip-tazo (ALLIUM). Recency-sensitive — confirm local formulary. FDA Drug Trials Snapshots: Exblifep
Still investigational: cefepime-taniborbactam (CERTAIN-1 positive vs meropenem) remains FDA-unapproved as of early 2026 (the 2024 CRL was manufacturing/CMC-only). Recency-sensitive. CIDRAP / Urology Times, 2024–2026
New oral agents — but for UNcomplicated UTI only, not cUTI: gepotidacin (Blujepa, FDA 25 Mar 2025) and sulopenem etzadroxil/probenecid (Orlynvah, FDA Oct 2024). Know they exist; do not use them for cUTI. FDA approvals 2024–2025
Local guidance is current: Michigan (rev 03/2026) and our institution (rev 04/2026) CPGs already encode the 2025 reclassification and short courses, correctly avoid nitrofurantoin/fosfomycin for cUTI, and reserve carbapenems for septic/MDRO presentations.

◆Anki cards minted this run

cUTI classification — beyond-bladder / systemic features define "complicated"; sex and comorbidity do not.
Empiric carbapenem use gated by SEPSIS / MDRO; non-septic cUTI → cephalosporin, pip-tazo, or FQ.
Gram-negative bacteremia of urinary source = 7 days (BALANCE, NEJM 2024).
IV→PO switch criteria for cUTI including pyelonephritis / bacteremic UTI.

Held (cap reached): cefepime-enmetazobactam as the newest cUTI agent; "avoid nitrofurantoin/fosfomycin in cUTI" (classic, and a related ESBL oral-step-down card is already in the deck).

Sources: IDSA cUTI 2025 — Introduction & Methods (CID 2025, doi:10.1093/cid/ciaf459); Selection of Antibiotic Therapy (doi:10.1093/cid/ciaf460); Timing of IV-to-Oral Transition (doi:10.1093/cid/ciaf461); Duration of Antibiotics (doi:10.1093/cid/ciaf462). BALANCE (NEJM 2024, doi:10.1056/NEJMoa2404991; PMID 39565030). Cefepime-enmetazobactam — FDA Drug Trials Snapshots: Exblifep (ALLIUM). EUA classification — Bonkat, Eur Urol Open Sci 2025;75:44 (doi:10.1016/j.euros.2025.03.010). Michigan Medicine UTI CPG (rev 03/2026). Our institution Complicated UTI CPG (rev 04/2026).