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ascension from the urethra, lead to urinary tract infection. The urine may also become contaminated with
bacteria through haematogenous means. Bacteriuria may be either symptomatic or asymptomatic but
often leads to pyuria. Pyuria is defined as the presence of pus (white blood cells) in the urine and is
indicative of the inflammatory changes consistent with infection. Bacteriuria without pyuria typically
indicates simple bacterial colonization; however, the converse warrants evaluation for tuberculosis,
stones, or malignancy.
Clinical features
Generally, urinary infections are defined clinically, but are further described by their site of origin. For
example, the term acute pyelonephritis relates to the inflammatory changes resulting from bacterial
infection within the renal parenchyma. Clinical characteristics of this diagnosis include fevers, rigors,
flank pain, bacteriuria, and pyuria in the setting of infection proven by culture. Severe, complicated
infections may produce sepsis, warranting emergent diagnosis and intensive monitoring. Complicated
urinary infections may occur in immuno-compromised patients including those with diabetes, or in any
patient with obstructed urinary system or aberrant urinary anatomy. At times, intra-renal and peri-renal
abscesses may be an endpoint in the evolution of pyelonephritis, potentially warranting operative
drainage.
Cystitis specifically refers to the inflammatory changes in the bladder secondary to bacterial urine
infection. Irritative voiding symptoms such as dysuria, frequency, hesitancy, and urgency (with or
without a component of incontinence) are characteristic of acute cystitis. Prostatic infection may produce
similar symptoms as well as obstructive symptoms including nycturia, incomplete voiding, and a weak
stream.
Pyelitis and urethritis are the terms used for infections of the upper collecting system and urethra
respectively. Urethritis warrants further investigation for sexually transmitted diseases or for anatomical
abnormalities. Sexually transmitted diseases tend to occur more commonly in younger, more sexually
active individuals. Gonococcus sp. and Chlamydia sp. infections are common aetiologic organisms in
patients presenting with urethritis or epididymitis. Coliform bacterial urethritis may be seen with
complicated urinary fistulous disease or associated with anal intercourse. Rates are higher in men than in
women, partially due to the fact that signs and symptoms in men are often more obvious. In these cases,
the examining physician should also screen for other sexually transmitted diseases such as HIV, syphilis,
and hepatitis B and C as well as visually inspect for signs of herpes and condylomata.
Diagnosis
Complete history, physical examination, and laboratory work-up are keys to early diagnosis in patients
suspected of having urinary infection. All patients should have a mid-stream clean-catch collection or
catheter collected urinalysis with microscopic studies and urine culture prior to initiation of antimicrobial
treatment. Urinary symptoms, pyuria, bacteriuria, and evidence of active inflammatory changes in the
urine such as the presence of nitrite and leukocyte esterase may warrant empiric treatment prior to culture
and sensitivity reporting. Urinary infection is less likely in the absence of pyuria and may require urine
culture data for verification. Conversely, pyuria without bacteriuria may indicate an atypical infectious
aetiology such as genitourinary tuberculosis, staghorn calculi5, or other urinary stone disease. Finally,
5 Staghorn calculi: branched stones in the renal collecting system, usually involving two or more calyces.
ICAO Preliminary Unedited Version — November 2009 III-6-9
serum leukocytosis and positive blood cultures may indicate a complicated urinary infection in an acutely
ill patient.
Radiographic studies may be useful in identifying anatomical anomalies in complicated urinary
infections. Some helpful studies include intravenous urography, ultrasonography, computed tomography,
and cystography. In patient groups without contraindications, IVU and contrast enhanced CT are
important tools to evaluate nephroureterolithiasis, obstruction, anatomical aberrations, and renal
enlargement as seen with pyelonephritis. Ultrasonography may aid in the differentiation of epididymitis
from testicular torsion. Fullness of the testicular tail with ipsilateral increased epididymo-testicular blood
flow indicates the diagnosis of epididymitis.
Management
Coliform bacteria possess special virulence factors which allow them to adhere to the urothelium. Once
adherent, the bacteria may ascend or descend the upper or lower urinary tract. Upper tract infections may
range from uncomplicated to complicated, with the former requiring close outpatient follow-up with oral
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Manual of Civil Aviation Medicine 1(153)
