Hello Awesomites! :)
This post on Urinary Tract Infection (UTI) is brought to
you by our passionate MSGA Calvin Ong K.Y. and me, Upasana Y.
The following parts can be infected in an UTI:
- Kidney
- Urinary bladder
- Ureter
Infections of urethra is known as Urethritis, which is dealt under different clinical syndromes. Infection of
the urethra is mainly caused by N. gonorrhoeae, C. trachomatis, M. genitalium. T. vaginalis, HSV, and adenovirus can also cause urethritis.
Pathogens
Escherichia coli - It is the most common urinary
pathogen.
Proteus, Klebsiella, Pseudomonas species and Staphylococcus aureus are associated
with hospital acquired infections because their resistance to
antibiotics favor their selection. Catheterization and
gynecological surgery increase risk for these infections.
Proteus infections are associated with renal
stones. Proteus produces a potent urease which acts on ammonia, rendering the
urine alkaline.
S. saprophyticus infections are found in sexually active
young women.
Candida infection is usually seen in diabetic
patients and in the immunosuppressed.
M. tuberculosis is carried in blood to kidney from another site
of infection. (eg. respiratory TB)
Polymicrobial bacteruria is due to fistulas, urinary retention, infected stones or catheters.
Pathogenesis of UTI
1. COLONIZATION
- Pathogens colonizes the periurethral area and ascends through urethra upward
towards the bladder.
2. UROEPITHELIUM
PENETRATION - Fimbria allow bladder epithelial cell attachment and
penetration. Bacteria continue to replicate and may form biofilm.
3. ASCENSION -Bacterial
toxins may also play a role by inhibiting peristalsis (reducing the flow of
urine)
4. PYELONEPHRITIS
5. ACUTE KIDNEY INJURY
Risk factors of UTI
IATROGENIC/DRUGS-
- Indwelling catheter
- Antibiotic use
- Spermicides
BEHAVIOURAL-
- Voiding dysfunction
- Frequent or recurrent sexual intercourse
ANATOMIC/PHYSIOLOGIC-
- Vesicoureteral reflux
- Female sex (short urethra ~4cm)
- Pregnancy (progesterone mediated smooth muscle
relaxation to the bladder and ureters and compression of ureters by the
uterus)
GENETIC-
- Familial tendency
- Susceptible uroepithelial cells
- Vaginal mucus properties
Route of spread
- Ascending route
- Hematogenous
- Lymphatic
Signs & Symptoms of
Urinary Tract Infection
Urinary tract affected:
1. Urethra – cause
urethritis
-Burning and pain with
urination
(Urethritis is classified as an STI and not UTI by many textbooks)
2. Bladder – cause
cystitis
-Painful urination
-Frequent and persistent
urge to urinate
-Lower abdomen discomfort
-Cloudy/Strong-smelling
urine
3. Kidneys – cause
pyelonephritis
-Flank pain (Upper back
and side)
-Fever
-Chills
-Nausea and vomiting
Diagnostic Testing for
Urinary Tract Infections:
Types of urine Samples
-Mid stream Urine sample
-Catheter specimen of
urine during cystoscopy
-Suprapubic aspirate
-Early morning urine (TB
of urinary tract)
-Initial flow
(Urethritis, prostatitis)
Test
1. Urine microscopy
-Pyuria (pus presented
in urine + elevated white blood cells in urine)
-Hematuria (red blood
cells in urine)
RBCs
may be found in the urine during menstruation in a woman’s urine sample, thus
leading to a false positive result.
-Motile bacteria –
E.Coli, Proteus, Pseudomonas
-Non-motile bacteria –
Klebsiella
-Presence of cocci –
Staphylo-, Strepto-, Enterococci
**Presence of WBC casts
indicates pyelonephristis rather than cystitis
**If urine sample
contains abundant squamous epithelial cells - sample is contaminated and results are not
reliable
2. Urine dipsticks
-Use different chemicals
reagants on a strip that is dipped in urine to diagnose urinary tract diseases
-E.g. of dipstick result
(positive leukocyte esterase, positive nitrite, positive haemoglobin)
3. Urine culture
-Culture of mid-stream
urine – Blood agar, Mac Conkey agar
-Midstream void - ≥1 × 105 CFU/μL is consistent with infection
-Samples collected via
catheterization -≥1 × 102 CFU/μL is
consistent with infection
**Contamination of
samples may occur when urine passes through outer third of urethra
**Therefore, numeric
threshold of colony-forming units (CFU) per millilitre is used to confirm
infection.
4. Imaging test:-
It is not routinely done
in case of UTI.
Ultrasonography is indicated
-Obstruction in urinary flow
-Stones
-Measurement of bladder
residual volume in BPH
-Recurrent UTI
-Pyelonephritis or
hematuria.
KUB is most useful in suspected case of urolithiasis.
Computed tomography urography is used to view the kidneys and
adjacent structures, and may be considered to further evaluate patients with
possible abscess, obstruction, or suspected anomalies when ultrasonography is
not diagnostic.
If urinalysis is unrevealing, cystoscopy can be performed to evaluate for
bladder cancer, hematuria, and chronic bladder symptoms.
Urodynamic studies can be performed for persistent voiding
symptoms.
Intravenous urography - for hematuria evaluation if CT urography is not available.
Men with UTI
US with abdominal
X-RAY and flow rate
- No abnormality detected - no further
imaging
- Abnormal upper tract
- Abnormal lower urinary tract - further investigation
(e.g.cystoscopy,urodynamics or transrectal US)
We are grateful to our
teachers. :)
- Upasana Y. and Calvin
Ong K.Y.
