Urinary tract infection (UTI): Significant bacteriuria in the presence of symptoms of

acute UTI.

Urethritis

Cystitis

Pyelonephritis

Aetiology

• Many different microorganisms can infect the urinary tract but by far the most

common agents are the gram-negative bacilli.

• Escherichia coli cause approximately 80% of acute infections in patients without

catheters, urologic abnormalities or calculi.

• Other gram-negative rods especially Proteus spp and Klebsiella spp and occasionally

Enterobacter spp account for a smaller proportion of uncomplicated infections.

• These organisms plus Serratia spp and Pseudomonas spp assume increasing

importance in recurrent infections and in infections associated with urologic

manipulation, calculi or obstruction.

• They play a major role in nosocomial catheter-associated infections.

• In other women with acute urinary symptoms, pyuria and urine that is sterile (even

when obtained by suprapubic aspiration), sexually transmitted urethritis-producing

agents such as Chlamydia trachomatis, Neisseria gonorrhoeae, and herpes simplex

virus are etiologically important.

• These agents are found most frequently in young sexually active women.

Epidemiology

• Epidemiologically UTIs are subdivided into

Catheter-associated (or nosocomial) infections.

Non-catheter-associated (or community-acquired) infections.

• Infections in either category may be symptomatic or asymptomatic.

• Acute community-acquired infections are very common.

• These infections occur in 1 to 3% of schoolgirls and then increase markedly in incidence

with the onset of sexual activity in adolescence.

• Vast majority of acute symptomatic infections involve young women.

• Acute symptomatic UTIs are unusual in men under the age of 50.

• Development of asymptomatic bacteriuria parallels that of symptomatic infection and is

rare among men under 50 but common among women between 20 and 50.

• Asymptomatic bacteriuria is more common among elderly men and women with rates as

high as 40 to 50% in some studies.

Pathogenesis, Sources of Infection and Factors Affecting Pathogenesis

• The urinary tract should be viewed as a single anatomic unit that is united by a

continuous column of urine extending from the urethra to the kidney.

• In the vast majority of UTIs, bacteria gain access to the bladder via the urethra.

• Ascending of bacteria from the bladder may follow and is probably the pathway for most

renal parenchymal infections.

• In females prone to the development of cystitis, enteric gram-negative organisms residing

in the bowel colonize the introitus, the periurethral skin and the distal urethra before and

during episodes of bacteriuria.

• Hematogenous pyelonephritis occurs most often in debilitated patients who are either

chronically ill or receiving immunosuppressive therapy.

• Metastatic staphylococcal or candidal infections of the kidney may follow bacteremia or

fungemia spreading from distant foci of infection in the bone, skin, vasculature or

elsewhere.

Conditions Affecting Pathogenesis

• Gender and Sexual Activity

The female urethra appears to be particularly prone to colonization with colonic

gram-negative bacilli because of its proximity to the anus, its short length (about 4

cm) and its termination beneath the labia.

Vigorous sexual intercourse may predispose to introduction of bacteria into the

bladder and is temporally associated with the onset of cystitis.

More commonly UTI symptoms in men can be associated with a sexually transmitted

disease such as GC or Chlamydia.

Older men can have UTI symptoms due to prostatitis, kidney stones.

• Pregnancy

UTIs are detected in 2 -8% of pregnant women

Obstruction

• Any impediment to the free flow of urine (tumor, stricture, stone, or prostatic

hypertrophy) results in hydronephrosis and dilation of the ureters and a greatly increased

frequency of UTI.

Neurogenic Bladder Dysfunction

• Interference with the nerve supply to the bladder as in

Spinal cord injury

Tabes dorsalis

Multiple sclerosis

Diabetes and other diseases may be associated with UTI

• The infection may be initiated by the use of catheters for bladder drainage and is favored

by the prolonged stasis of urine in the bladder.

Vesicoureteral Reflux

• Defined as reflux of urine from the bladder cavity up into the ureters and sometimes into

the renal pelvis.

• Vesicoureteral reflux is common among children with anatomic abnormalities of the

urinary tract as well as among children with anatomically normal but infected urinary

tracts.

Bacterial Virulence Factors

• Most E. coli strains that cause symptomatic UTIs in non catheterized patients belong to a

small number of specific O, K, and H sero groups.

• These uropathogenic clones have accumulated a number of virulence genes that are often

closely linked on the bacterial chromosome in ‘virulence islands’

Genetic Factors

• Increasing evidence suggests that host genetic factors influence susceptibility to UTI.

• A maternal history of UTI is more often found among women who have experienced

recurrent UTIs than among controls.

Clinical Features of UTI

Cystitis

• Patients with cystitis usually report dysuria, frequency, urgency, and suprapubic pain.

• The urine often becomes grossly cloudy and malodorous and it is bloody in about 30% of

cases.

• Physical examination generally reveals only tenderness of the urethra or the suprapubic

area.

• Prominent systemic manifestations such as a temperature of >38.3°C, nausea and

vomiting usually indicate concomitant renal infection as does costovertebral (renal) angle

tenderness.

• However, the absence of these findings does not ensure that infection is limited to the

bladder and urethra.

Acute Pyelonephritis

• Symptoms of acute pyelonephritis generally develop rapidly over a few hours or a day

and include a fever, shaking chills, nausea, vomiting and diarrhea.

• Symptoms of cystitis may or may not be present.

• Hematuria may be demonstrated during the acute phase of the disease if it persists after

acute manifestations of infection have subsided, a stone, a tumor or tuberculosis should

be considered.

• Besides fever, tachycardia and generalized muscle tenderness, physical examination

reveals marked tenderness on deep pressure in one or both costovertebral angles or on

deep abdominal palpation.

• In some patients signs and symptoms of gram-negative sepsis predominate.

• Except in individuals with papillary necrosis, abscess formation or urinary obstruction

the manifestations of acute pyelonephritis usually respond to therapy within 48 to 72

hours.

Urethritis

• Approximately 30% of women with acute dysuria, frequency, and pyuria have midstream

urine cultures that show either no growth or insignificant bacterial growth

• Clinically these women cannot always be readily distinguished from those with cystitis.

• In this situation a distinction should be made between women infected with sexually

transmitted pathogens such as Chlamydia trachomatis, Neisseria gonorrhoeae, or herpes

simplex virus and those with low-count Eschelichia coli or staphylococcal infection of

the urethra and bladder.

Management of UTI

Investigation at Primary Health Care Facility

• Conduct dipstick urine examination (when available).

• The leukocyte esterase ‘dipstick’ method is less sensitive than microscopy in identifying

pyuria but is a useful alternative where microscopy is not feasible.

• Pyuria in the absence of bacteriuria (sterile pyuria) may indicate infection with unusual

bacterial agents such as C. trachomatis, U. urealyticum, and Mycobacterium tuberculosis

or with fungi.

• Alternatively sterile pyuria may be demonstrated in non-infectious urologic conditions

such as calculi, anatomic abnormality, nephrocalcinosis, vesicoureteral reflux, interstitial

nephritis or polycystic disease.

Investigation at Hospital

• Urine Microscopy (Urinalysis)

Microscopy of urine from symptomatic patients can be of great diagnostic value

Microscopic bacteriuria, which is best assessed with Gram-stained uncentrifuged

urine is found in more than 90% of specimens from patients whose infections are

associated with colony counts of at least 105/ml and this finding is very specific.

Bacteria cannot usually be detected microscopically in infections with lower colony

counts (102 to 104/ml).

The detection of bacteria by urinary microscopy thus constitutes firm evidence of

infection but the absence of microscopically detectable bacteria does not exclude the

diagnosis.

When carefully sought by means of chamber-count microscopy, pyuria is a highly

sensitive indicator of UTI in symptomatic patients.

Pyuria is demonstrated in nearly all acute bacterial UTIs and its absence calls the

diagnosis into question.

• Urine Culture

Determination of the number and type of bacteria in the urine is an extremely

important diagnostic procedure

• Specimens

Midstream urine (MSU) specimen

Suprapubic urine specimen (rarely indicated in adults unless unable to void or

introduce a urethral catheter)

Urine obtained by catheterization

Presence of bacteriuria of any degree in suprapubic aspirates or of 102 bacteria per

milliliter of urine obtained by catheterization usually indicates infection

 

Treatment

• The anatomic location of UTI greatly influences the success or failure of a therapeutic

regimen.

• Treatments listed are those to be prescribed before the etiologic agent is known.

Cotrimoxazole (TMP/SMZ)

Furadantin (Nitrofurantoin)

• Gram's staining can be helpful in the selection of empirical therapy.

• Such therapy can be modified once the infecting agent has been identified.

Note: Fluoroquinolones should not be used in pregnancy.

• Gentamicin should be used with caution in pregnancy because of its possible toxicity to

eighth-nerve development in the fetus.

• Multiday oral regimens for cystitis in adults are as follows

Cotrimoxazole, 960mg (160mg TMP/800mg SMX) q12h x 3 days

Norfloxacin, 400 mg q12h x 7-10 days

Ciprofloxacin, 250-500 mg q12h for 7-10 days depending on severity and

susceptibility.

Ofloxacin, 200-400mg 12 – 24hourly for 7-10 days

Enoxacin, 200 mg q12h for 7 days for uncomplicated UTI

Macrocrystalline, amoxicillin 500mg q8h for 5-7 days

Note: Some of the drugs mentioned here might not be readily available in primary health

care facilities.

• Oral regimens for pyelonephritis and complicated UTI are either

• Cotrimoxazole 960mg q12h for 10-14 days or

Ciprofloxacin, 500 mg q12h for 10-14 days or

Ofloxacin, 200-300 mg q12h for 14-28 days (in prostatitis) or

Lomefloxacin,400 mg/d for 10-14 days or

• Parenteral regimens are as follows

Ciprofloxacin, 200-400 mg q12h or

Ofloxacin, 200-400 mg q12h or

Gentamycin, 3-5mg/kg per day divided dosing q 8 hours or

Ceftriaxone, 1-2 g/daily or

Ampicillin, 1 g q6h or

Imipenem, 250-500 mg q6-8h or

Note: UTI in men is always considered complicated and treatment should be targeted at

the likely bacteria.

• It is recommended to add Doxycycline 100 mg twice daily for 7 days to the possible

treatment regimens in this population (men).

• If prostatitis is the cause, a prolonged course (14-21 days) of antibiotic therapy is

recommended

Prevention and Prognosis of UTI

Prevention

• Women who experience frequent symptomatic UTIs (3 per year on average) are

candidates for long-term administration of low dose antibiotics directed at preventing

recurrences.

• Such women should be advised to avoid spermicide use soon after intercourse.

• Prophylaxis should be initiated only after bacteriuria has been eradicated with a full-dose

treatment regimen.

• The same prophylactic regimens can be used after sexual intercourse to prevent episodes

of symptomatic infection in women in whom UTIs are temporally related to intercourse.

• Other patients for whom prophylaxis appears to have some merit include

Men with chronic prostatitis.

Patients undergoing prostatectomy, both during the operation and in the postoperative

period.

Pregnant women with asymptomatic bacteriuria

• All pregnant women should be screened for bacteriuria in the first trimester at 12-16

weeks of pregnancy and should be treated if bacteriuria is demonstrated/discovered

(quinolones should not be used in pregnancy).

Prognosis

• In patients with uncomplicated cystitis or pyelonephritis, treatment ordinarily results in

complete resolution of symptoms.

• Cystitis may also result in upper tract infection or in bacteremia especially during

instrumentation but little evidence suggests that renal impairment follows.

• Acute uncomplicated pyelonephritis in adults rarely progresses to renal functional

impairment and chronic renal disease.

• Repeated upper urinary tract infections often represent relapse rather than reinfection and

a vigorous search for renal calculi or an underlying urologic abnormality should be

undertaken.

• Repeated symptomatic UTIs in children and in adults with obstructive uropathy,

neurogenic bladder, structural renal disease or diabetes progress to chronic renal disease

with unusual frequency.

• Asymptomatic bacteriuria in these groups as well as in adults without urologic disease or

obstruction predisposes to increased numbers of episodes of symptomatic infection but

does not result in renal impairment in most instances.                                      

REFFERNCES;

•      Braunwald & Fauci (2001). Harrison’s principles of internal medicine 15th Ed.  Oxford: McGraw Hill

•      Davidson, S (2006). Principles and practice of medicine 20th Ed.  Churchill: Livingstone.

Kumar & Clark (2003) Textbook of clinical medicine. Churchill: Livingstone.

•      Douglas Model (2006): Making sense of Clinical Examination of the Adult patient. 1st Ed. Hodder Arnold

•      Longmore, M., Wilkinson, I., Baldwin, A., & Wallin, E. (2014). Oxford handbook of clinical medicine. Oxford

•      Macleod, J. (2009). Macleod's clinical examination. G. Douglas, E. F. Nicol, & C. E. Robertson (Eds.). Elsevier Health Sciences.

•      Nicholson N., (1999), Medicine of Non-communicable diseases in adults. AMREF

•      Stuart and Saunders (2004): Mental health Nursing principles and practice. 1st Ed. Mosby

•      Swash, M., & Glynn, M. (2011). Hutchison's clinical methods: An integrated approach to clinical practice.