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Urinary tract infection (UTI)


Urinary tract infection (UTI) is defined as the presence of >10^5 microorganisms/ml of urine in the urinary tract in a midstream sample of urine.

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UTIs are quite common worldwide, but more prevalent in the developing and underdeveloped countries. Both makes and females are suffer from urinary tract infections, but females are generally more susceptible to UTIs.

Causes of increased occurrence of UTIs in females :

  • Shorter urethra compared to males. So it is easier for microbes to ascend up and cause an infection
  • Close proximity of the external urethral meatus to the vagina and vulva that are heavily contaminated with bacteria.
  • Sexual intercourse predisposes both males and females to an UTI, but more so for females because of the slightly increased risk of trauma to the urethra during intercourse (also known as honeymoon cystitis).
  • Pregnancy aggravates thi risk of getting an UTI

Other risk factors that may affect both sexes :

  • Incomplete bladder emptying
    a) Bladder outflow obstruction
    b) Neurological problems like multiple sclerosis, diabetic neuropathy.
    c) Vesico-ureteric reflux
  • Foreign bodies like urethral catheter, ureteric stent.
  • Loss of host defenses
    a) Atrophic urethritis and vaginitis in post menopausal women
    b) Diabetes Mellitus

Some common organisms causing urinary tract infections :

  • Escherichia Coli (E. Coli) derived from GI tract. E. Coli is responsible for about 75% of UTIs.
  • Proteus species
  • Staphylococcus saprophyticus and Staphylococcus epidermidis
    a) Staph. Saprophyticus causes UTIs in newly sexually active females.
    B) Staph. Epidermidis is responsible for UTIs associated with indwelling urinary catheters.
  • Enterococcus fecalis
  • Klebsialla
  • Pseudomonas species

Clinical Features of UTIs :

  • Abrupt onset of increased frequency of urination.
  • Dysuria : Painful or uncomfortable urination
  • Urgency : A sudden, almost uncontrollable need to urinate
  • Urine may appear cloudy. May have an unpleasant odor.
  • Hematuria : Blood in the urine
  • Suprapubic pain and tenderness if there cystitis (infection of the urinary bladder).
  • Loin pain and tenderness if there is pyelonephritis (infection in the kidneys and renal pelvis)
  • Systemic symptoms may include fever with chills and rigors

It is important to remember that some patients show no symptoms despite having an UTI. This is known as asymptomatic bacteriuria.

Depending on the location of infection along the urinary tract, UTIs can be divided into Upper UTI and Lower UTI.
Infections of the kidney and ureters are classified as Upper and anything below the ureters are Lower UTI.

Upper UTI commonly presents with fever with chills and rigors and, loin pain and tenderness. Lower UTIs commonly presents as fever, burning sensation during micturition and suprapubic pain.

Long standing upper UTI may cause renal damage. No such risk with lower UTIs.

For upper UTIs, usually parenteral antibiotics for long duration is necessary. For lower UTIs, usually oral antibiotic for short duration is enough.

Some typical features of lower urinary tract symptoms :

  • Voiding (obstructive) symptoms
    a) Hesitancy (worsened if the bladder is very full)
    b) Poor flow, which is unimproved by straining
    c) Intermittent stream : stops and starts
    d) Dribbling, including even after micturition
    e) Sensation of poor bladder emptying
  • Storage (irritative) symptoms :
    a) Frequency
    b) Nocturia : Excessive frequent urination after going to bed
    c) Urgency
    d) Urge incontinence
    e) Nocturnal incontinence (enuresis) : Involuntary discharge of urine after the age at which bladder control should have been established

Laboratory Investigations :

  • Routine examination of urine
  • Culture of a clean catch mid stream sample of urine
  • Full blood count
  • Blood urea, serum electrolytes, serum creatinine
  • Blood culture to detect if septicemia is present
  • Renal ultrasound or CT (if pyelonephritis is suspected)
  • Cystoscopy to evaluate continuous hematuria or if some other bladder lesion is suspected

Treatment :
A full course of appropriate antibiotics should be prescribed to treat UTIs. Specific treatment regimens varies widely depending on the specific organism that is causing the infection and their sensitivity and resistance to the available antibiotics.

In general, trimethoprim is the 1st choice drug for uncomplicated UTIs. Other drugs include amoxicillin, cephalexin, ciprofloxacin, etc.

For complicated UTIs, co-amoxiclav and ciprofloxacin are the first choice drugs. cefuroxime and gentamicin are also used.

Important thing to keep in mind is that, trimethoprim and quinolones like ciprofloxacin should be avoided in pregnant ladies. Drug of choice in pregnant ladies are cephalexin, amoxicillin and co-amoxiclav.

Recurrent Urinary Tract Infections :

If the causative organism persists on repeat culture despite treatment, or if there is reinfection with any organism after an interval, then an underlying cause is more likely to be present and a more detailed investigation may be necessary.

In women, recurrent UTIs are common. So, further investigation is only justified if the frequency of infections are 3 or more per year or if theinfections are unusually severe. Recurrent UTI, particularly in presence of an underlying cause may result in permanent renal damage.

Prophylactic therapy :

If an underlying cause can not be removed, suppressive antibiotic therapy can be used to prevent recurrence and reduce the risk of septicemia and renal damage. Urine should be cultured at regular intervals. A regime of 2 or 3 antibiotics in sequence, rotating every 6 months is used in an attempt to try and reduce the risk of emergence of resistant organisms. Trimethoprim, co-amoxiclav and nitrofurantoin are some commonly used drugs.

Prophylaxis against recurrent UTIs :

  • Adequate fluid intake (at least 2L/day)
  • Regular complete emptying of bladder
  • Good personal hygiene
  • Emptying bladder before and after sexual intercourse

Essentially, we should all try to adopt these habits, regardless of whether one suffers from recurrent UTIs or not.

  • Treatment of underlying cause

Sources :
Davidson's Principles and Practice of Medicine, 22nd edition
D.C. Dutta's textbook of Gynecology, 6th edition
Bailey and Love's Short Practice of Surgery, 26th edition
Goljan Rapid Review Pathology, 4th edition
Taber's Cyclopedic Medical Dictionary, edition 21


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