RESEARCH Asymptomatic bacteriuria Prevalence in the elderly population Yohanes Ariathianto Aim Asymptomatic bacteriuria (ASB) is a may be due to reduced oestrogen and increased To identify the prevalence of common condition seen in primary care vaginal pH from lack of lactobacilli colonisation asymptomatic bacteriuria in the elderly patients. This review aims to identify postmenopause, thereby predisposing women to population and to examine associated the prevalence of ASB in the elderly colonisation by uropathogens.2 risk factors, complications and natural population and to examine its associated Asymptomatic bacteriuria is also more history, and whether treatment improves risk factors, complications and natural common in institutionalised patients, with greater prognosis. history, and whether treatment improves functional impairment compared to community Methods prognosis. dwellers (25–50% of women, 15–35% of men in A literature search of MEDLINE, institutionalised care),4 and in hospitalised elderly PubMed and the Cochrane Library patients (32–50% of women, 30–34% of men).1 It was undertaken of studies published Methods is also common among stroke patients, with ASB from 1980 to 2009. A total of 70 articles A literature search of MEDLINE was undertaken found in 11.8% of subacute and chronic stroke were identified. Emphasis was given using the search terms ‘asymptomatic bacteriuria’ patients.5 to randomised controlled trials, review and ‘elderly’, with the limits of ‘core clinical articles and more recent publications. Aetiology journals’, ‘English language’, ‘human’, ‘aged 65 Results and above’, and ‘studies published from 1980 Asymptomatic bacteriuria is usually caused by Asymptomatic bacteriuria is common to 2009’. This identified 54 articles. Repeating normal flora of the gut, which then ascends up in the elderly, especially among the search using PubMed with identical terms the urethra into the bladder and potentially the institutionalised or hospitalised patients. and criteria revealed an additional 14 articles. kidneys. The commonest causative organism Risk factors include cognitive impairment, Searching the Cochrane Library database is Escherichia coli. Other frequently isolated diabetes mellitus, structural urinary tract abnormalities and indwelling catheters. using the same terms revealed two relevant organisms include Gram negative bacteria such Antimicrobial therapy does not result reviews. Emphasis was given to randomised as Klebsiella pneumonia and Proteus mirabilis, in improved survival or genitourinary controlled trials, review articles and more recent and increasingly, Gram positive organisms such morbidity and may potentially cause publications. Local Australian guidelines were as Enterococcus faecalis, coagulase negative avoidable side effects and the also searched. The information obtained was then Staphylococcus and group B Streptococcus. emergence of resistant organisms. structured under the headings of: prevalence, Among institutionalised patients, P. mirabilis 6 Conclusion aetiology, risk factors, diagnosis, complications, is most frequently isolated, and for patients Bacteriuria is common in functionally and management. with long term urinary catheters, polymicrobial impaired elderly patients. In the bacteriuria is common, often including Prevalence absence of symptoms or signs of Pseudomonas aeruginosa, Morganella morganii infection, routine dipstick screening and Asymptomatic bacteriuria is common among and Providencia stuartii.7 subsequent antimicrobial therapy is not elderly patients in the community, residential aged Risk factors recommended. care facilities and in the hospital setting. The prevalence of ASB increases with age, ranging Several factors are postulated to be associated Keywords: aged; bacteriuria; from 0% in men aged 68–79 years to 5.4% in men with increased ASB (Table 1). Structural urinary asymptomatic states aged 90–103 years in one study,1 possibly related tract abnormalities such as the presence of renal to reduced bactericidal activity of prostatic fluid calculi are thought to predispose bacteriuria by with age.2 This rising prevalence is even more causing irritation and inflammation of the urinary pronounced in women, increasing from 13.6% to tract mucosa, restricting urinary flow which leads 22.4% in the corresponding age bracket.3 This to stasis and obstruction.2 Reprinted from AUSTRALIAN FAMILY PHYSICIAN VOL. 40, NO. 10, OCTOBER 2011 805 RESEARCH Asymptomatic bacteriuria – prevalence in the elderly population Comorbid conditions such Alzheimer dementia, urine culture.10 A subsequent prospective study well to antimicrobial therapy and changing of the Parkinson disease and cerebrovascular disease confirmed that a higher mean PVR is associated collecting bag.16 may also potentially predispose to ASB through with urinary tract infection in asymptomatic male Diagnosis their adverse effects on bladder motility and patients.11 continence.8 Diabetes mellitus also increases The presence of an indwelling catheter, Despite guidelines (Table 2), making a diagnosis the risk of ASB by potentially causing neurogenic especially long term, has been shown to of ASB, and hence deciding not to prescribe bladder, diabetic microangiopathy and impaired independently increase risk of ASB, with a antibiotic treatment, is challenging in clinical immune system from hyperglycaemia.2 Primary prevalence of 9–23% in short term catheterisation practice, especially in elderly patients. Many biliary cirrhosis, for a reason that is yet to be fully and 100% in long term catheterisation (>30 elderly patients, whether due to language understood, also increases the risk of ASB (annual days).12 barriers or cognitive impairment, are unable to incidence 35%).9 In a study of community dwelling elderly, give a reliable history. They also frequently have A high postvoid residual (PVR) volume may also urinary incontinence (OR: 2.99, 95% CI: 1.60–5.60), multiple comorbid conditions with nonspecific contribute, with a PVR >180 mL in asymptomatic reduced mobility (OR: 2.68, 95% CI: 1.42–5.03) and systemic manifestations such as lethargy, men having 87% positive predictive value and oestrogen treatment (OR: 2.20, 95% CI: 1.09–4.45) weakness and loss of appetite, and hence it is 94.7% negative predictive value of a positive were factors that were independently associated often difficult to ascertain if these symptoms are with ASB.13 It remains unclear however, if these due to bacteriuria. Table 1. Factors associated with the factors had any direct causal effect on ASB or This difficulty is especially true for residents presence of asymptomatic bacteriuria if they were only associations. In particular, of long term care facilities. A qualitative survey oestrogen therapy may have been prescribed in conducted in Canada found there are multiple Physiological Pathological these patients in an attempt to prevent recurrent triggers for ordering a urine culture, many of Age Neurological disease, symptomatic urinary tract infection, hence the which were nonspecific symptoms such as eg. Alzheimer disease, association found between ASB and oestrogen increased irritability, aggressiveness and, ‘not Parkinson disease, stroke treatment. being themselves’. Physicians frequently rely Gender (female Diabetes mellitus, Chronic constipation is also a risk factor for on the judgment of nursing staff when making a more than primary biliary cirrhosis male) lower urinary tract symptoms, and possibly ASB, decision whether or not to order a urine culture. Reduced mobility likely due to its potential to induce progressive However, some of the information that the Urinary tract abnormality neuropathy in the pelvic floor and causing urinary decisions were based on was often incomplete (eg. calculi, prostate retention. A 9 year follow up study has shown or unreliable due to staff working hours and poor enlargement, high PVR a clinically significant association between documentation of patients’ histories.17 volume) constipation and urinary incontinence (OR: 1.46, In addition, due to language barriers or Indwelling urinary 95% CI: 1.34–1.58).14 Chronic constipation can cognitive impairment, elderly patients are often catheter also lead to overflow faecal incontinence and unable to produce clean-catch urinary samples, Constipation perineal soiling which further increases the risk of resulting in contaminated and difficult to bacteria ascending up the urinary tract and causing interpret samples.18 Other signs of infection such 15 Table 2. Diagnosis of asymptomatic infection. Constipation is also a risk factor for as fever and leukocytosis is found less commonly bacteriuria based on IDSA guidelines7 purple urine bag syndrome, a rare phenomenon in elderly patients, therefore the absence of occurring typically in elderly catheterised female leukocytosis does not reliably exclude the Lack of signs and symptoms of urinary 19 tract infection patients. Although this phenomenon can be presence of infection. associated with urinary tract infection, it responds Urine dipstick is not a good diagnostic Diagnosis based on urine specimen collected in manner that minimises contamination Table 3. IDSA grades of recommendation7 For asymptomatic men – single voided urine specimen with one bacterial species A–I: Good evidence to support recommendation for use; should always be offered and isolated in quantitative count ≥100 000 evidence is from more than one properly randomised controlled trial cfu/mL A–II: Good evidence to support recommendation for use; should