Renal, Fluids, Electrolytes & Acid-Base · Topic 7 of 22

UTI, Pyelonephritis & Urosepsis

Renal & GU · urinary tract infection

UTI, Pyelonephritis & Urosepsis

Treat symptoms, not bacteriuria: decide whether infection has left the bladder, pick empiric therapy by sepsis status, and keep courses short.

Key numbers

Short courses for improving pyelonephritis5–7 days

01 · What it isComplicated UTI = infection beyond the bladder

Uncomplicated UTI is confined to the bladder in an afebrile patient; complicated UTI has spread beyond it — pyelonephritis, febrile or bacteremic UTI, catheter-associated UTI, or prostatitis.

02 · The ruleDo not treat asymptomatic bacteriuria

Do not screen for or treat asymptomatic bacteriuria — including in older adults, diabetes and chronic catheters — except in pregnancy and before urologic procedures that cause mucosal bleeding.

03 · DoShort courses for improving pyelonephritis

For complicated UTI or pyelonephritis that is improving on effective therapy, treat 5–7 days with a fluoroquinolone or 7 days with another agent, rather than 10–14 days; 7 days also for gram-negative bacteremia.

Presentation

What you'll see

Older or catheterized patients: sepsis without urinary symptomsOlder adults and patients with a catheter or neurogenic bladder may present with sepsis or delirium and no urinary symptoms.

Pyelonephritis: fever, flank pain, CVA tendernessCystitis causes dysuria, frequency, urgency and suprapubic pain; pyelonephritis adds fever, chills, flank pain, costovertebral angle tenderness, nausea and vomiting.

Diagnosis & monitoring

Work-up

Culture urine in complicated or high-risk UTICulture urine in men, pregnancy, suspected pyelonephritis or sepsis, recurrent UTI, recent instrumentation or immunosuppression; typical cystitis in women can be treated on urinalysis alone.

Do right now

In this order

First moves

Urosepsis: blood cultures, lactate, then antibiotics

→

Choose empiric cUTI therapy by sepsis status

→

Drain an obstructed infected urinary tract

→

Narrow to culture, then switch to oral

Why each step

Urosepsis: blood cultures, lactate, then antibioticsA septic patient with suspected UTI needs blood and urine cultures, CBC, lactate, BUN and creatinine, then prompt empiric antibiotics and the sepsis bundle.

Choose empiric cUTI therapy by sepsis statusEmpiric complicated UTI therapy: with sepsis, a 3rd/4th-generation cephalosporin, carbapenem, piperacillin-tazobactam or fluoroquinolone; without sepsis, a cephalosporin, piperacillin-tazobactam or fluoroquinolone — reserve carbapenems.

Drain an obstructed infected urinary tractAn obstructed infected tract needs drainage (stent, nephrostomy or catheter) for source control; perinephric or cortical abscesses may need surgical drainage.

Narrow to culture, then switch to oralNarrow to a targeted agent once culture susceptibilities return, and switch from IV to oral when the patient is improving, can take oral medication and an effective oral option exists.

Management

Orders

Cystitis: nitrofurantoin, TMP-SMX or fosfomycin must knowUncomplicated cystitis in women: nitrofurantoin 100 mg BID × 5 days (avoid if CrCl < 60 mL/min), TMP-SMX 160/800 mg BID × 3 days, or fosfomycin 3 g once; fluoroquinolones are not first-line.

Outpatient pyelonephritis: oral fluoroquinoloneOutpatient pyelonephritis (oral intake, no sepsis, obstruction or immunosuppression): ciprofloxacin 500 mg BID × 7 days or levofloxacin 750 mg daily × 5–7 days when local resistance is under 10%.

Not improving by 72 hours: image the tractMost patients defervesce within 72 hours of effective therapy; image the urinary tract (ultrasound or CT) if not responding, or with stones, prior renal surgery, recurrent or complicated infection — looking for obstruction or abscess.

CAUTI: replace the catheter, then cultureCatheter-associated UTI (catheter in place > 2 days): test only symptomatic or high-risk patients, replace the catheter and culture the new one, and treat as for pyelonephritis.

Pregnancy pyelonephritis: admit, no fluoroquinolonesPyelonephritis in pregnancy is treated inpatient with an IV cephalosporin, aztreonam or ampicillin plus gentamicin; avoid fluoroquinolones and TMP-SMX.

Men with cystitis: 7 days, no nitrofurantoinMen with cystitis always get antibiotics guided by culture — TMP-SMX or trimethoprim for 7 days; avoid nitrofurantoin (poor prostatic penetration) and consider prostatitis.

The rules

Know these

Check prior cultures and fluoroquinolone exposureBefore choosing empiric therapy, avoid any antibiotic to which a previous urine isolate was resistant, and avoid fluoroquinolones if the patient received one in the past 12 months.

Cystitis or pyelonephritis?

Commonly confused

Where	Confined to the bladder
Findings	Dysuria, frequency, urgency, suprapubic pain; afebrile
Urine culture	Usually not needed in women
Empiric drug	Nitrofurantoin, TMP-SMX or fosfomycin
Duration	Single dose to 5 days

Teach & follow up

Patient education

Prevent CAUTI: remove catheters earlyThe best CAUTI prevention is avoiding indwelling catheters and removing them as soon as possible; prefer intermittent catheterization and a closed system; prophylactic antibiotics are not recommended.

More detail

Reference

Show 5 reference facts

Phenazopyridine relieves severe dysuria for no more than 2 days; it turns urine red-orange and is contraindicated in renal insufficiency.

Febrile UTI in men with suspected acute bacterial prostatitis may need 10–14 days of therapy.

Pyuria = ≥ 8 WBC/µL of uncentrifuged urine; a positive nitrite is highly specific but insensitive; bacteria without pyuria usually means contamination.

Pyelonephritis from hematogenous spread rather than ascent is characteristic of Staphylococcus aureus, Pseudomonas, Salmonella and Candida.

For cystitis with allergy or resistance to first-line drugs, newer oral options include gepotidacin and sulopenem etzadroxil/probenecid.

Pearl

No symptoms, no antibiotics — except in pregnancy and before a urologic procedure that breaches the mucosa.

Sources · Merck Manual Professional — Bacterial Urinary Tract Infections (UTIs) (Mar 2026) · Trautner BW et al. IDSA 2025 Guideline on Complicated Urinary Tract Infections · Merck Manual Professional — Catheter-Associated Urinary Tract Infections (Mar 2026) · Starter sheet built from the verified AGACNP fact map (facts reviewed 2026-10-15).