Definitions

• UTI = presence of signs/symptoms caused + 10⁵ CFU/mL bacteria in culture
• If asymptomatic, it's just colonization!
• Colonization frequently seen in: indwelling/intermittent catheter use, bowel in urinary tract (e.g. ileal conduit/neobladder)
• Uncomplicated UTI = non-complicated UTI in healthy female
• Complicated UTI = presence of
• Anatomic/functional abnormality of urinary tract (BPH, stone, diverticulum, VUR, obstruction, neurogenic bladder, etc.)
• Immunocompromised (diabetes, HIV, steroids)
• Pregnant
• Spinal cord injury (SCI)
• Male
• Pediatric - higher risk of renal scarring from febrile UTI/pyelonephrosis → HTN, renal insufficiency later in life
• Congenital causes: VUR, UPJ obstruction, ureterocele/ectopic ureter (a/w duplicated system), posterior urethral valves (PUV), urachal remnants, neurogenic bladder (spina bifida)
• Indwelling urinary catheter/stent/drain (bacteriuria risk 5%/day)
• Renal insufficiency
• Recurrent UTI = Two separate culture-proven UTIs in 6 months, or three in 1 year
• Can be 2/2 bacterial persistence (stones, foreign bodies (stents), obstruction/diverticulum, bacterial prostatitis) or re-infection (fistula, urine retention, VUR, immunosuppression, sexual activity
• Persistent UTI = UCx remains positive despite abx
• may be 2/2 abx resistance, non-compliance, renal dysfunction limiting urinary excretion of abx, fistula

Ddx

• STI/urethritis, prostatitis
• nephrolithiasis
• OAB (overactive bladder)
• atrophic vaginitis
• neoplasm

Pathogens (ascending infection)

• E. coli most common (80%)
• Adheres with pili/fimbriae - Type 1 pili are mannose sensitive (inhibited by d-mannose); P pili are mannose resistant (typically present in pyelonephritis)
• Staph saprophyticus (5-15%), Klebsiella, Enterobacter, Proteus, Pseudomonas, enterococcus
• Proteus causes xanthogranulomatous pyelonephritis (XGP) - chronic infection of renal parenchyma causing diffuse destruction including beyond Gerota's fascia.
• XGP looks like malignancy; "foam" cells on pathology; must be surgically excised (typically open nephrectomy as kidney is usually non-functioning)
• Staph aureus in urine = hematogeneous spread/there was bacteremia at some point; get blood cultures!
• Fungal - candida
• Viral - adenovirus 11/21, BK virus

History

• Acute cystitis: dysuria, frequency, urgency, suprapubic discomfort, hematuria, cloudy or foul smelling urine
• Spinal cord injury patients can sometimes still tell if they have an UTI (malaise, etc.)
• Pyelonephritis: cystitis + flank pain, n/v, often with fever
• Progresses to acute bacterial nephritis (ABN), abscess
• Risk factors: diabetes, steroid use, diaphragm/spermicide use

Physical exam

• Recurrent UTI - check for atrophic vaginitis, prostatitis, epididymitis, urethral diverticulum, vesico-vaginal fistula

Urinalysis 

• Sample should be clean-catch midstream urine sample in adults; clean cath or suprapubic aspiration in children
• Leukocyte esterase - presence of WBCs (64-90% specific/sensitive)
• Pyuria - > 5 WBCs/HPF (95% sensitive, not specific)
• Sterile pyuria (UCx negative for bacteria) - consider chlamydia, mycobacteria (GU TB), fungus/virus (adenovirus)/protozoa (trich)/parasite (schisto), inflammatory (e.g. interstitial nephritis with eosinophils), tumor
• Can see WBC casts in pyelo
• Nitrites - presence of certain Gram - bacteria (very specific, 50% sensitive)
• e.g. + leukest and - nitrites could be Gram + Enterococcus
• Pseudomonas is Gram - but does not make nitrites
• Urine culture: > 100,000 colonies/ml is diagnostic
• See below for tx of asymptomatic bacteriuria (don't, mostly)
• How to spin urine - 1500-4000 RPM x 3-5 min, decant supernatant, resuspend pellet and drop on slide

Other labs

• CBC: Pyelonephritis will usually have elevated WBC count, but negative blood culture
• Blood culture: if mod/sev ill; prominent fever or leukocytosis
• + blood culture a/w abscess, emphysematous pyelonephritis

Indications for imaging

• Uncomplicated cystitis/pyelo generally does not need imaging
• Pediatric UTI 2mo-2yr: RBUS, with VCUG if RBUS abnormal
• Anatomic abnormality or not responding to treatment - consider CT, RBUS, VCUG
• Pyelonephritis - CT if: unstable/septic, immunocompromised (incl. diabetes), known structural abnormality, stone, obstruction, febrile > 72 hrs on abx
• May reveal ABN (poorly defined solid enhancing mass), or abscess (well-defined non-enhancing fluid filled mass)

Antibiotics

• Asymptomatic bacteriuria/pyuria alone is NOT AN INDICATION FOR ABX
• Only treat asymptomatic bacteriuria in
• pregnancy (decreases r/o pyelo, frequency of low birth weight/pre-term, or
• pre-op for GU procedures with mucosal incision/trauma (e.g. TURP)
• No one else!! not even SCI patients

• ^aFluoroquinolones are second-line for UTI - no longer recommended as first-line empirical tx due to side effects (tendon rupture). Moxi and gemi do not have good urinary levels.
• Still first choice for empirical outpatient pyelo tx
• Ampicillin/amoxicillin should not be used for empirical tx due to poor efficacy (unless want Enterococcus coverage)
• ^bBactrim - not for < 2 mo old (causes kernicterus)
• ^cMacrobid/nitrofurantoin - not for < 1 mo old (hemolytic anemia); > 70 yo (pulmonary toxicity); or CrCl < 60. Can also cause liver problems

Obtain test of cure (repeat cx) in: pregnancy, pyelo, complicated/relapsing UTI

UTI in pregnancy

• UTIs occur in 17-20% of pregnancies; asymptomatic bacteriuria in 2-10%, and pyelonephritis in 2-4%
• Uterus obstructs ureters; increased filtration decreases antibiotic levels
• Asymptomatic bacteriuria a/w premature rupture of membranes/preterm labor, chorioamnionitis
• Screen with UCx at 12-16 weeks
• Treat pyelo aggressively with hospitalization, start with CTX 1g daily 
• If pyelo, or two episodes of UTI, or ASB > 100k in pregnancy, consider daily suppression with nitrofurantoin or keflex for the remainder of the pregnancy
• OK to use (pregnancy class B)
• Macrobid (except in 3rd trimester; causes hemolytic anemia)
• Penicillins
• Cephalosporins
• Fosfomycin
• Do not use
• Bactrim (folate issues in 1st trimester, kernicterus in 3rd trimester) - class D
• Fluoroquinolones (cartilage issues) - class C

Symptomatic treatment: OAB meds, Pyridium (urinary analgesic), NSAIDs

Antibiotic prophylaxis

• Suppressive therapy - 6-12 months then re-evaluate?
• TMP 100 mg qd
• Bactrim SS daily or 3x/wk
• Nitrofurantoin 50 mg or 100 mg daily
• Keflex 125 or 250 qd
• Fosfomycin 3g q10d
• Self-start therapy
• Post-coital therapy - take 1 pill post coitus
• Bactrim SS or DS one pill
• Nitrofurantoin 50 or 100 mg

Non-antibiotic prophylaxis

• Urine acidification (with vitamin C)
• Methenamine salts - converted to formaldehyde in acidic urine
• Hipprex 1g PO q12h, methenamine mandelate 1g PO q6h
• Cranberry - mechanism of action is via proanthocyanidins (PACs) - supplement should generally have > 36 mg of PACs to be useful
• Lactobacillus probiotics - insufficient evidence
• D-Mannose?
• All data is stronger for antibiotic prophylaxis vs non-antibiotic