UTIs behave differently — and are managed differently — depending on the host and the situation. This tab covers urosepsis and the special contexts where the usual "treat the bacteriuria" rules change: the elderly, the catheterised, the spinal-cord-injured, the pregnant, candiduria, and the surgical emergency of periurethral abscess.
Bacteraemia, Sepsis, and Septic Shock
| Term | Definition |
|---|---|
| SIRS | Extremes of body temperature, heart rate, ventilation, and immune response — may follow infection, trauma, thermal injury, or sterile inflammation |
| Sepsis | SIRS + infection (documented or strongly suspected) |
| Severe sepsis | Sepsis + organ dysfunction or tissue hypoperfusion (typically SBP <90 mmHg or MAP <70 mmHg) |
| Septic shock | Sepsis-induced hypotension persisting despite adequate fluid resuscitation (± elevated lactate or oliguria) |
- The earliest metabolic change in septicaemia is respiratory alkalosis — bacteraemic patients hyperventilate even before temperature extremes and chills.
- Gram-negative bacteria predominate (30–80% of cases) over gram-positive (5–24%); anaerobes cause bacteraemia when the source is a post-surgical intra-abdominal abscess or transrectal prostate biopsy. The prime initiator of gram-negative septic shock is endotoxin (LPS) from the bacterial outer membrane; exotoxins can also trigger it, but the bacteria and their cell-wall components are primarily responsible.
- A resistant pathogen is more likely with antimicrobial use in the past month, advanced age, and male sex.
- Management principles: resuscitation, supportive care, monitoring, broad-spectrum antimicrobials, and drainage or elimination of the infective source.
Bacteriuria in the Elderly
- Epidemiology — >20% of women and 10% of men over 65 have bacteriuria.
- Pathogenesis — declining cell-mediated immunity, neurogenic bladder dysfunction, perineal soiling from faecal/urinary incontinence, more urethral catheterisation, and (in women) estrogen-depleted vaginal change.
- Pathogens — E. coli causes 75%; S. saprophyticus is not seen in this population.
- Diagnosis is difficult — most are asymptomatic, concomitant disease masks or mimics UTI, and even severe upper-tract infection may lack fever or leukocytosis. Do not screen for asymptomatic bacteriuria in community-dwelling or long-term-care elderly: RCTs of treatment versus no therapy in nursing-home residents showed no fewer symptomatic episodes and no survival benefit, while treatment increased adverse drug effects, resistant reinfection, and cost.
- Management — do not treat asymptomatic bacteriuria (treating it to improve incontinence is not justified). For symptomatic UTI, give 7 days of therapy with the goal of eliminating symptoms, not sterilising the urine. Bacteriuria is clinically significant and needs prompt therapy when there is a structural abnormality (e.g. obstruction with hydronephrosis) or systemic condition (e.g. severe diabetes). Urea-splitting organisms (Proteus, Klebsiella) form infection stones and can cause severe renal damage; the ammonia they generate is absorbed systemically and may cause encephalopathy or coma at high levels, particularly with obstruction.
Catheter-Associated Bacteriuria
The most common nosocomial infection — 80% of nosocomial UTIs follow an indwelling urethral catheter, and closed drainage is the most effective preventive measure. Most patients are asymptomatic. Treat only when symptomatic (e.g. febrile): obtain a urine culture before starting antimicrobials, and stop the agent within 48 hours of resolution. If the catheter has been in for several weeks, encrustation can shelter bacteria from the drug, so the catheter should be changed.
UTIs in Spinal Cord Injury
- Risk factors — impaired voiding, bladder over-distension, elevated intravesical pressure, obstruction, vesicoureteral reflux, instrumentation, stones, low fluid intake, poor hygiene, perineal colonisation, decubiti/local trauma, and reduced host defence from chronic illness.
- Pathogens — short-term catheterisation is usually a single organism; catheterisation beyond a month is usually polymicrobial.
- Presentation — most are asymptomatic (loss of sensation removes frequency/urgency/dysuria); instead they report flank/back/abdominal discomfort, leakage between catheterisations, increased spasticity, malaise, lethargy, or cloudy/malodorous urine. UTI is the most common cause of fever in the SCI patient.
- Management — clean intermittent catheterisation (CIC) lowers lower-tract complications (low intravesical pressure, fewer stones) and reduces UTI, fever, bacteraemia, epididymitis, and prostatitis. Suprapubic and indwelling urethral catheters reach an equivalent infection rate eventually, though bacteriuria onset may be delayed with a suprapubic catheter (this differs from the NLUTD guidelines, which suggest a lower infection rate with suprapubic). In the absence of reflux, asymptomatic bacteriuria in CIC patients is not a significant risk for renal damage and does not need antibiotics. Treat only symptomatic patients — always culture first (diverse flora, high resistance); an oral fluoroquinolone is the agent of choice for afebrile patients, and an indwelling catheter should be changed to maximise drainage. Prophylaxis is not supported for most neurogenic bladders from SCI.
Periurethral Abscess
A life-threatening infection of the male urethra and periurethral tissues, frequently a sequela of gonorrhoea, urethral stricture disease, or catheterisation. Presenting features are scrotal swelling (94%), fever (70%), acute urinary retention (19%), a spontaneously drained abscess (11%), and dysuria or urethral discharge (5–8%). Management is immediate suprapubic urinary drainage and wide debridement.
Candiduria
Common, particularly with indwelling catheters, diabetes, and recent antibiotics; usually asymptomatic and benign.
- Asymptomatic — remove the indwelling catheter if feasible (clears funguria in 75% within 2 weeks); in catheter-dependent patients, change the catheter and repeat the culture (resolves funguria in 20%). Switch from an indwelling catheter to CIC when possible (indwelling carries a 10× higher candiduria risk). Persistent candiduria warrants a work-up for predisposing factors — post-void residual to exclude retention, and renal ultrasound for hydronephrosis, urolithiasis, fungus balls, and abscess; if none are found, observe with repeat culture over 1–3 months. Obtain fungal blood cultures in critically ill ICU patients with persistent funguria. Treat asymptomatic candiduria only in three groups: neutropenic patients, very-low-birth-weight infants (<1500 g), and patients undergoing urologic manipulation.
- Symptomatic — treat. First-line is oral fluconazole 200 mg daily ×14 days. Nearly all C. albicans and most C. glabrata are susceptible; for resistant strains use flucytosine or amphotericin B.
Bacteriuria in Pregnancy
Anatomic and Physiologic Changes
- Renal size increases (~1 cm) from greater vascular and interstitial volume.
- Hydronephrosis from the obstructive effect of the enlarging uterus (likely the main factor) plus progesterone-mediated smooth-muscle relaxation (reduced ureteral peristalsis, ureteral dilatation, increased bladder capacity).
- Bladder is displaced by the uterus, with increased capacity (progesterone) and possible hypertrophy (estrogen).
- Renal function improves — GFR rises 30–50% and protein excretion increases, so values normal in non-pregnant women may indicate insufficiency in pregnancy; urinary protein is not abnormal until >300 mg/24 h.
- Changes that raise UTI risk: reduced bladder tone (oedema, hyperaemia) and increased upper-tract urine volume as physiologic dilation evolves — both predispose to pyelonephritis.
Complications of bacteriuria in pregnancy include pyelonephritis, prematurity and perinatal mortality, and (conflicting evidence) maternal anaemia. Recurrent UTIs are not a contraindication to pregnancy. In women with renal insufficiency, the degree of impairment is the major determinant of outcome — fetal survival is only slightly reduced with mild/moderate disease, but perinatal mortality is ~4× higher with severe disease. Pathogens are similar to non-pregnant women.
Asymptomatic Bacteriuria
One of the most common infections in pregnancy (prevalence 4–7%, similar to the general population), but it is far more likely to progress to pyelonephritis and, unlike in non-pregnant women, rarely resolves spontaneously without treatment. The risk of progression to pyelonephritis is 1% in non-pregnant versus 20–40% in pregnant women — driven by the anatomic/physiologic changes above and a urinary pH more suitable for E. coli growth at all stages. Treating asymptomatic bacteriuria cuts the pyelonephritis risk to 0–5%.
Diagnosis
Obtain an initial screening urine culture in all pregnant women in the first trimester (urinalysis/reagent strips have significant false-negative rates). If there is no growth, repeat cultures are generally unnecessary, since early no-growth predicts low later risk.
Management
Treat bacteriuria with a full 3–7 day course; hospitalise acute pyelonephritis for initial parenteral therapy.
- Safe agents: penicillins (ampicillin 500 mg QID, amoxicillin 250 mg TID, penicillin V 500 mg QID); cephalosporins (cephalexin 500 mg QID, cefaclor 500 mg QID); fosfomycin; and nitrofurantoin (especially with penicillin allergy, 100 mg QID — discontinue at 35 weeks).
| Avoid in pregnancy | Reason |
|---|---|
| Fluoroquinolones | Damage to immature cartilage |
| Trimethoprim | Megaloblastic anaemia (anti-folate) |
| TMP-SMX | Early teratogenicity; late kernicterus |
| Nitrofurantoin (3rd trimester) | Neonatal haemolytic anaemia |
| Chloramphenicol | "Gray baby" syndrome |
| Erythromycin | Maternal cholestatic jaundice |
| Tetracyclines | Maternal liver decompensation; inhibits fetal bone growth |
Obtain follow-up cultures to document clearance. A positive follow-up must be classified as unresolved infection (select another drug), bacterial persistence, or reinfection (consider antimicrobial suppression or prophylaxis for the rest of the pregnancy). After a single episode of pyelonephritis or two episodes of cystitis, give daily suppression with nitrofurantoin or cephalexin until delivery.