Urinary tract infection¶

source: Pocket Medicine, 2022
UTI_zh

Definitions¶

Asymptomatic bacteriuria: presence of bacteria in urine without signs or symptoms of infection
Uncomplicated: confined to bladder. No upper tract or systemic infection signs.
Complicated:
- extends beyond bladder (pyelonephritis, renal/perinephric abscess, prostatitis) with symptoms of fever, rigors, malaise, flank pain, CVA tenderness or pelvic/perineal pain.
- More likely to develop bacteremia or sepsis.
- Men, those w/ nephrolithiasis, strictures, stents, urinary diversions, immunosupp, DM, are not automatically complicated.
- Pregnant & renal transplant are considered complicated.

Uncomplicated: E. coli (80%), Proteus, Klebsiella, S. saprophyticus (CID 2004;39:75). In healthy, nonpregnant women, lactobacilli, enterococci, Group B strep, and coag-neg staph (except S. saprophyticus) are likely contaminants (Annals 2012;156:ITC3).
Complicated: as above + Pseudomonas aeruginosa, enterococci, staph (uncommon primary urinary pathogen w/o catheter or recent instrumentation; ? bacteremia w/ hematogenous spread). ↑ multidrug resistance.
Catheter-associated: E. coli most prevalent, candida, Enterococcus, Pseudomonas aeruginosa, other GNR
Urethritis: Chlamydia trachomatis, Neisseria gonorrhoeae, Ureaplasma urealyticum, Trichomonas vaginalis, Mycoplasma genitalium, HSV

Cystitis: dysuria, urgency, frequency, hematuria, suprapubic pain; fever absent. R/o vaginitis if symptoms of cystitis & urethritis. Neurogenic bladder Pts may have atypical symptoms (↑ spasticity, autonomic dysreflexia, malaise).
Urethritis: dysuria, urethral discharge (see “STI”)
Prostatitis
- Chronic: similar to cystitis + symptoms of obstruction (hesitancy, weak stream)
- Acute: perineal pain, fever, tenderness on prostate exam
Pyelonephritis: fever, chills, flank or back pain, nausea, vomiting, diarrhea
Renal abscess: pyelonephritis symptoms + persistent fever on appropriate antibiotics

Urinalysis: pyuria + bacteriuria ± hematuria ± nitrites
Urine culture (clean-catch midstream or straight-cath):
- Obtain culture only if symptoms (although in ill Pts, can include ΔMS, autonomic instability)
- ⊕ if: ≥10⁵ CFU/mL, though <10⁵ but ≥10²/mL may still indicate UTI in some scenarios
- Pyuria & ⊖ UCx=sterile pyuria. Ddx: prior antibiotics, nephrolithiasis, interstitial nephritis, tumor, TB, urethritis (see “STI”)
Catheter-associated: requires (1) symptoms/signs (incl atypical) + (2) urine culture w/ 1 species ≥10³ colonies from clean urine sample (after replacing Foley). Pyuria alone not sufficient to diagnose
Blood cultures: obtain in febrile Pts; consider in complicated UTIs
For all men w/ UTI, consider prostatitis: ✓ prostate exam
CT: consider in severely ill, obstruction, persistent symptoms after 48-72 hours of appropriate antibiotics

Scenario	Empiric Treatment Guidelines (narrow based on urine culture)
Asymptomatic bacteruria	Do not treat. Exceptions: pregnant women, renal transplant, prophylaxis prior to invasive urologic procedures (CID 2019;68:1611).
Cystitis (JAMA 2014;16:1677)	Uncomp: nitrofurantoin × 5 days or TMP-SMX × 3 days or fosfomycin (3 g × 1). Complicated: outpatient fluoroquinolone or TMP-SMX PO × 7-14 days FQ or TMP-SMX superior to β-lactams (_NEJM_2012;366:1028) Inpatient: ceftriaxone or fluoroquinolone; PO if improving, if growing GPC add vancomycin If catheterized remove or exchange catheter.
Prostatitis	FQ or TMP-SMX PO × 14-28 days (acute) or 6-12 weeks (chronic)
Pyelonephritis	OutPt: fluoroquinolone × 7 days or TMP-SMX PO × 14 days (Lancet_2012;380:452) InPt: ceftriaxone × 14 days; if at risk for MDR pathogen cefepime, pip-tazo, carbapenem, or plazomicin (_NEJM 2019;380:729) (Δ IV → PO when clinically improved & afebrile 24-48 hours, tailor to culture)
Renal abscess	Drainage + antibiotics as for pyelonephritis