UTI Flashcards
Common causes of pyelonephritis
• ascending (usually GN bacilli) or hematogenous route (usually GP cocci)
• causative microorganisms:
- gram positives (haematogenous): Enterococcus faecalis, S. aureus, S. saphrophyticus
- gram negatives (ascending): E. coli (most common), Klebsiella, Proteus, Pseudomonas, Enterobacter
• common underlying causes of pyelonephritis
- stones, strictures, prostatic obstruction, vesicoureteric reflux, neurogenic bladder, catheters, DM, sickle-cell disease, PCKD, immunosuppression, post-renal transplant, instrumentation, pregnancy
Px of pyelonephritis
Fever, loin pain +/- dysuria/frequency/urgency
• rapid onset (
Ix for pyelonephritis
MSU: E coli 80%.
CT: low perfusion, swollen kidney
• U/A, urine C&S
• CBC and differential: leukocytosis, left shift
• imaging indicated if suspicious of complicated pyelonephritis or symptoms do not improve with 48-72 h of treatment
- abdominal/pelvic U/S (kidney may be diffusely dilated with vessels enlarged. Hyperechoic) C.f. if an abscess there is a collection of hypoechoic /dark ball that does not have any shadowing. Abscess is HYPOdense on CT. Kidneys are more hypodense than liver in general.
- CT
• nuclear medicine: DMSA scan can be used to help secure the diagnosis
- a photopenic defect indicates active infection or scar; if normal alternative diagnoses should be considered
Rx of pyelonephritis
- hemodynamically stable: outpatient oral ABx treatment ± single initial IV dose (see Table 8)
- severe or non-resolving: admit, hydrate, and treat with IV ABx (see Table 8)
- emphysematous pyelonephritis: consider emergent nephrectomy after IV ABx started and patient stabilized
- renal obstruction: admit for emergent stenting or percutaneous nephrostomy tube
Define uncomplicated & complicated UTI
Uncomplicated UTI: structurally & functionally normal
Complicated UTI: infection in a pt with a structural/functional abnormality that reduces efficacy of antibiotics
Who gets UTI & why?
Infants: Anatomica/congenital, foreskin
Children: Dysfunctional voiding
Young adults: Sexual activity
30-60yo:Prostatic obstruction, pregnancy, vaginal prolapse, catheters
Elderly: Incontinence, catheters, hospital acquired
What are the risk factors for UTI?
Bacterial factors:
• E.coli:
○ Subgroups/serogroups O, H, K: high adherence. Produce haemolysins initiating cell invasion & make iron available to bacteria.
○ K capsular Antgen: protects against phagocytosis by neutrophils
○ Pili fimbriae: P. pili more likely in pyelonephritis & type I pili more likely in lower UTI (cystitis).
○ Ligand at the end of pili binding with glycolipids & glycoprotein receptors on cell surface of uroepithelial cells
Host factors
• Unobstructed urinary flow (mechanical wash out)
• Urine factors:
○ Osmolality/organic acid/pH acidic urine/urea
○ Tamm Horsfall proteins (low adherence of bacteria to the wall)
○ Muco polysaccharide/Glycosaminoglycan prevents penetration
• Cells secrete Interleukin 8 & Mucosal IgA: recruit neutrophils
• Se + urinary antibodies produced by kidney: increased opsonisation, phagocytosis & reduced bacterial adherence
• Periurethral flora (lactobacilli) low colonisation by virulent bacteria
• Urinary retention/stasis/reflux due to obstruction/neuro conditions/diabetes/pregnancy/FB/catheters/stents
Px of UTI
- Dysuria/frequency/strangury/urgency/lower back pain (c.f. loin pain)/haematoria
- Cloudy/foul smelly urine
- Temp/fever rare
Ix of UTI
Urinalyasis: leucocyte esterase, nitrites (degradation of nitrates to nitrites)
MSU (mid stream urine): M + C&S, micro (increased WCC, bacteriuria), culture (>10^5-10^6 CFU/ml)
Recurrent infections:
• MSU
• Se glucose (random)
• Urinary tract imaging: US - PVR volume/hydro/calculi
• Cystoscopy: intravesical pathology (especially in men as it is very rare to have recurrent infections)
Rx of UTI
Antibiotic considerations:
• Infecting pathogen S/R
• Patient factors: allergies, underlying disease, liver/renal, diabetes, site infection, pregnancy, outpatient/inpatient
• Arbitrary dose/duration
• Prophylactic antibiotics
• Suppressive antibiotics; suppress bacterial persistence
Protocol: 7 days of antibiotics but usually by 3 days it resolves.
Antibiotics e.g. bactrim, fluoroquinolone, nitrofurantoin (macrodentin), aminoglycosides, cephalosporins, penicillins
Rx of recurrent UTIs
- Increase fluids intake to increase urine output to flush
- Cranberry supplements (increase GAG preventing bacterial adherence in kidneys)
- Hygiene issues (wipe front to back not viceversa)
- Post coital: voiding & Antibiotics (a single dose of ceflex post coital within 20-30min. If feel an infection coming, short sharp Abx for 3 days; ceflex or macrodantin)
- Prophylactic Abs (2-3 months 1 capsule/day. Then take a break and see what happens)/home supply
- Topical periurethral oestrogen (post menopausal) -> change the urothelium and predispose women to infections.
Describe bactrim as Abx for UTI
common Abx used in urology; sulfamethoxazole/trimethoprim
• Interferes with bacterial metabolism of folate
• Not effective for enterococcus/pseudomonas
• SE: rash, GI upset, leukopaenia, thrombocytopaenia, Stevens Johnson syndrome
• CI: G6PD deficiency, pregnancy
Describe fluoroquinolones as Abx for UTI
- Interfere with DNA gyrase, prevents bacterial replication
- Not effective for staphylococci
- SE: GI upset, dizziness, Achilles tendon tenderness
- CI: pregnancy
Describe nitrofurantoin as Abx for UTI
- Used as a prophylactic Abx
- Inhibits bacterial enzymes & DNA activity
- Not effective for Pseudomonas & proteus
- Covers Staph & enterococci
- SE: GI upset, peripheral polyneuropathy, hepatotoxicity, pulmonary interstitial changes
Describe aminoglycosides as Abx for UTI
- many bad side effects & now less popular
• Inhibit bacterial RNA & DNA synthesis
• SE: Nephro/oto toxicity (ear poisoning). If normal kidney function -> careful use within the normal dose. SE generally irreversible.
