Page 965 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

696 PART 5: Infectious Disorders

5
CHAPTER Urinary Tract Infections contamination. Significant bacteriuria is defined as ≥10 organisms/mL.
In the presence of urinary symptoms, a count of ≥10 organisms/mL from
2
12
75 Gerard J. Sheehan a woman with pyuria represents true infection. In a catheterized patient
with symptoms or signs of UTI without other explanation, a criterion of
Eoghan de Barra
≥10 organisms/mL represents catheter-associated urinary tract infec-
3
tion (CAUTI). Pyuria, the presence of white blood cells in urine, is best
13
measured with a counting chamber, using a criterion of ≥10 cells/μL;
alternatively a criterion of ≥5 pus cells/high powered field is used. Pyuria
KEY POINTS
has a sensitivity of 96% for symptomatic UTI, but should not be used
• Empiric antimicrobial therapy for acute severe urosepsis should to support a diagnosis of UTI in the catheterized patient. In assessing a
initially include two agents with activity against gram-negative patient with sepsis of unknown source, whether in the community or
bacilli, such as a third- or fourth-generation cephalosporin, aztreo- health care system, whether catheterized or not, the absence of pyuria is
nam, or extended-spectrum penicillin in combination with either useful at excluding a urinary source of sepsis. 13
a fluoroquinolone or an aminoglycoside.
• Where local epidemiology indicates significant prevalence of URINARY TRACT INFECTION DUE TO BACTERIA
extended-spectrum ß-lactamases among Enterobacteriaceae, then
a carbapenem such as imipenem, meropenem, ertapenem, or ■ CLINICAL FEATURES OF ACUTE PYELONEPHRITIS
doripenem is preferred while awaiting definitive cultures.
• Where local epidemiology indicates significant prevalence of carbape- Acute pyelonephritis is a syndrome of fever with evidence of renal
inflammation, such as costovertebral angle tenderness or flank pain, usu-
nem-resistant Enterobacteriaceae, then colistin and a carbapenem
should be chosen while awaiting definitive cultures. ally accompanied by signs of systemic toxicity. In the very elderly or cog-
nitively impaired, acute confusion may be the sole manifestation. Patients
• Urine and blood cultures should be obtained prior to the first anti- with spinal cord injury are especially prone to silent and complicated
microbial doses, which should be given without delay. pyelonephritis associated with urinary obstruction due to calculi. They
• Once the pathogen is identified by a positive urine or blood culture, often will have fever with nonspecific abdominal discomfort, increased
the antimicrobial regimen should be tailored to a single, least toxic spasms, and autonomic dysreflexia. Patients admitted with acute pyelo-
agent with the narrowest spectrum, based on susceptibility data. nephritis who subsequently deteriorate should be urgently investigated
• Patients with severe urosepsis requiring ICU admission should for urinary tract obstruction and for a suppurative focus. Alternatively,
have imaging of the urinary tract on an urgent basis, preferably such deterioration may be due to a resistant urinary pathogen. Features
by computed tomography with intravenous contrast, because sup- that suggest obstruction include renal colic and severe costovertebral
purative complications require drainage as a priority. angle tenderness. Blood and urine cultures should always be obtained
• Percutaneous drainage by an interventional radiologist is generally promptly before therapy, if necessary by a single “in-out” urinary cath-
eterization. Acute renal failure caused directly by pyelonephritis or renal
preferred to drain definitively or stabilize temporarily a patient suppuration is rare and if present, is usually due to sepsis, hypotension,
14
with suppurative complications. or drug toxicity.
• Urinary catheters cause a high incidence (3%-7% per day) of
bacteriuria and candiduria; the latter associated with broad- ■
spectrum antimicrobial therapy. MICROBIOLOGY
• Asymptomatic catheter–associated bacteriuria or candiduria Most (80%) community-acquired UTIs in women are caused by
should not be treated; the only exceptions are transplant and neu- Escherichia coli. Staphylococcus saprophyticus is the second most com-
tropenic patients, and before instrumentation of the urinary tract. mon community urinary pathogen in younger women, but it virtually
• The continued usefulness of a urinary catheter should be reas- never gives rise to sepsis and ICU admission. Enterobacteriaceae other
than E coli (eg, Klebsiella, Proteus, Enterobacter, Citrobacter, Morganella,
sessed on a regular basis, and removal in selected patients should Providentia, Serratia species), Enterococcus species, Pseudomonas aeru-
be considered. ginosa, and Candida species are each uncommon. In men, E coli is
• Fever or sepsis should only be attributed to catheter-associated also the commonest community-acquired urinary pathogen, but other
bacteriuria and treated only after exclusion of other potential Enterobacteriaceae and enterococci are more frequent than in women.
causes of infection. The spectrum changes to more resistant species when UTI arises
in the ICU. Gram-negative bacilli account for about half, consisting
of Enterobacteriaceae such as E coli (21%-23%), Klebsiella (9%), and
Community-acquired pyelonephritis sometimes leads to sepsis syn- Enterobacter species (4%), along with the nonfermenters P aeruginosa
drome and intensive care unit (ICU) admission, especially when it arises (10%) and Acinetobacter baumannii (1%); Candida species account for
in an obstructed urinary tract or when the host defense is compromised 21% to 29% and enterococci for 15%. This predominance of more
15
by poorly controlled diabetes. Bacteremia arises in about 15% of cases, resistant species reflects the more widespread use of broad-spectrum
at a rate of 50 per 100,000 person years, with a 28-day mortality of about antimicrobial agents and the use of urinary catheters in the ICU.
5%. Urinary tract infection (UTI) is also a common sequel of ICU, Bacteriuria or candiduria, acquired through urinary catheterization,
1
because of the use of urinary catheters for in excess of 70% of ICU patient constitutes a reservoir of resistant pathogens, which can occasionally be
days and ranks in the top three or four of ICU-acquired infections. a source of epidemic spread of resistant infection within the ICU.
3,4
2
Although older data suggested that catheter-associated UTI caused Almost all UTIs arise by the ascending route, but in the case of
mortality, more recent studies that control for confounding factors Candida species and S aureus, the kidneys are sometimes seeded
5,6
show no such link. 7-10 In addition the evidence that bacteriuria prolongs through the bloodstream. Over 3 years, only four such bacteremic/
ICU stay or increases cost has also been challenged. Unfortunately fungemic infections were identified, compared to 356 ascending UTIs
11
asymptomatic bacteriuria is frequently screened for and treated, result- in the same period in a Canadian ICU. Isolation of S aureus in a urine
8
ing in harmful and unnecessary antimicrobial therapy. culture should prompt a search for evidence of invasive staphylococcal
Quantitative culture methods distinguish true bacterial multiplica- infection elsewhere. Multiple or single cortical renal abscesses (renal
tion within the urinary tract from a false result due to procurement carbuncle) may be present.

section05_c74-81.indd 696 1/23/2015 12:37:26 PM