Urinary Tract Infection in the Elderly Patient: Epidemiology, Presentation, and Treatment
Author: Michelle Blanda, MD, FACEP, Associate Professor of Emergency Medicine, Northeastern Ohio Universities College of Medicine/Summa Health System, Akron, OH.
Peer Reviewer: Rita Kay Cydulka, MD, FACEP, Associate Professor, Department of Emergency Medicine, Case Western Reserve University, MetroHealth Medical Center, Cleveland, OH.
Elderly patients represent a heterogeneous group, ranging from individuals in the community who are clinically well and fully functional to those who are impaired, non-communicative, immobile nursing home residents. A common cause for emergency presentation in this age group is infection.
Urinary tract infections (UTIs) with respiratory infections are the most common cause of bacteremia in the elderly.1-4 This is true for the community-dwelling elder, as well as for the institutionalized elderly patient. For the emergency department (ED) physician, this diagnosis often is a challenge. UTIs in the older population may present in an obscure manner. Patients in this age group tend to have multiple medical problems and can present with multiple somatic complaints. Conversely, physicians must be careful to not prematurely assign the diagnosis of UTI to a patient who actually has a different source of infection or another problem.
The emergency physician must be able to make appropriate decisions about diagnosis and treatment of UTIs for the geriatric patient. This article will discuss definitions associated with UTI. Epidemiology and risk factors in the elderly and morbidity and mortality will be reviewed. Pathophysiology, diagnostics, and treatment considerations for the older patient will be examined. Special attention will be given to institutionalized patients and the use of catheters.
— The Editor
Definitions
A variety of definitions is used to describe infections involving the urinary tract. (See Table 1.) These definitions hold true for all age groups and for both sexes. Bacteriuria simply means bacteria in the urine with no evidence of actual tissue invasion. UTI is defined as bacteriuria with evidence of host injury that is clinically manifested by the presence of symptoms.5 For this paper, UTI and symptomatic bacteriuria will be used interchangeably. Symptomatic bacteriuria usually will present with urgency, dysuria, and frequency. It also may present with lower abdominal pain, fever, and malaise. Asymptomatic bacteriuria is bacteria in the urine in a patient without any obvious symptoms. Pyuria is the presence of white blood cells in the urine and is commonly associated with bacteriuria.
| Table 1. Definitions/Common Terms |
| • Bacteriuria: Bacteria in the urine |
| • Complicated UTI: UTI associated with anatomical, functional, or pharmacological factors predisposing patients to persistent infections, recurrent infections, or treatment failures |
| • Uncomplicated UTI: Symptomatic bacteriuria without anatomical, functional, or pharmalogical factors |
| • Recurrent infection: Infection with different organisms |
| • Relapse: Infection with the same organism |
| • Pyuria: Presence of white blood cells in the urine |
| • Pyelonephritis: Infection of the kidneys |
Pyelonephritis is an infection involving the kidneys. It is characterized by symptoms of UTI associated with flank pain, costovertebral angle tenderness, and fever. It usually is an infection that ascended from the bladder. Sometimes it is caused by sequelae from a partially or untreated UTI. Recurrent UTI distinguishes itself from relapse because a different organism causes it. For the discussion that follows, we will use the definitions provided here to present previous literature findings and management strategies.
Epidemiology
Prevalence. UTIs are more common in women than men. In the general population, the incidence in women is estimated to be about 10-times greater.6 This disparity becomes less obvious in the elderly population. In fact, the incidence of UTIs in elderly men closely matches that found in elderly women. The prevalence of bacteriuria in women at 70 years of age is 5-10% and increases to approximately 20% at 80 years of age.6,7 In men ages 60-65 years, 1-3% have bacteriuria. This increases to more than 10% for men older than 80 years.8,9 The incidence of bacteriuria exceeds 20% in the institutionalized non-ambulatory population for both genders.8 In a study of 13 nursing homes, including almost 2000 patients, a 16% incidence of UTI was reported.10
Morbidity and Mortality. UTIs remain a significant cause of morbidity and health care expense in all age groups.11 Compared to bacteremia from other sources, UTIs have the lowest mortality. The frequency of concomitant chronic illness and decreased resistance in the elderly age group would seem to infer increased rates of morbidity and mortality.12 However, multiple studies have found that there is no increased incidence of death with asymptomatic bacteriuria or uncomplicated UTI.8,13-15 Being male, having a concomitant illness, and having a chronic indwelling catheter are associated with a higher mortality from bacteremic UTIs.8,16,17 The mortality rate is approximately 10-30% for UTI associated with bacteremia.18,19 It is interesting to note that, if other risks are controlled for, that advanced age does not increase mortality.16
Risk Factors
Certain risk factors specific to the elderly population make them more susceptible to UTIs. (See Table 2.) Different contributing factors exist and vary in importance for the different, diverse geriatric populations. Obstruction to urine flow at any level of the urinary tract leads to stasis and compromised bladder and renal defense mechanisms. Stasis contributes to attachment, colonization, and multiplication of pathogens in the genitourinary tract. Increased residual volume predisposes and maintains bladder infection by providing a continuous pool of media suitable for bacterial growth. For both elderly functional men and women, structural genitourinary abnormalities such as cystocoeles, rectocoeles, and bladder diverticula lead to increased residual urine and are a risk factor. For community-dwelling men, prostatic hypertrophy with obstruction and bacterial prostatitis are likely contributing factors.8,20
| Table 2. Risk Factors for Urinary Tract Infections in the Elderly |
| • Immobilization |
| • Less frequent urination |
| • Incomplete bladder emptying |
| • Prostate disease (men) |
| • Neuropathic diseases |
| • Immune response deterioration |
| • Increased incidence of renal/bladder/prostatic calculi |
| • Iatrogenic genitourinary instrumentation |
For community-dwelling elderly women, contributing factors, such as the loss of estrogen, are more significant. When present, estrogen stimulates the proliferation of lactobacillus in the vaginal epithelium. Lactobacillus reduces the pH of the genitourinary tract and interferes with colonization by preventing attachment of Escherichia coli to the epithelium.21 Some lactobacillus strains produce hydrogen peroxide, which also contributes to lower bacteria counts.22 Loss of estrogen results in a uropathogen dominant vaginal flora without the normal protective lactobacilli and an elevated pH. The absence of estrogen also decreases the strength of the vaginal muscles, resulting in laxity of the ligaments holding the uterus, pelvic floor, and bladder. Bladder emptying, which is an important defense against infection, becomes impaired.23,24
In the institutionalized elderly population, the greater risks for UTI are immobilization and functional impairment. Neurological problems, such as Alzheimer’s disease, Parkinson’s disease, and cerebrovascular accidents, commonly are seen in the nursing home patient and are associated with increasing bacteriuria. These diseases lead to impaired voiding, increased residual urine volumes, and uretic reflux, which put the patient at risk.8
Chronic illnesses, which occur more frequently in the elderly, also may contribute to increased bacteriuria. Diabetic women have three times the prevalence of bacteriuria compared to women the same age without diabetes.8,25
Certain medications also may put the elderly patient at risk. Anticholinergic medication may impair bladder emptying. Alpha-adrenergic medications such as phenylpropanolamine and pseudoephedrine, common over-the-counter medications, may cause an increase in urethral resistance and impair bladder emptying.21
Pathogenesis and Microbiology
Successful invasion of the urinary tract is determined, in part, by the virulent characteristics of the bacteria, the inoculum’s size, and the inadequacy of host defenses.25,26 Normal urine possesses characteristics that effectively diminish the survival of organisms in the tract. Most organisms normally colonizing the urethra do not multiply in urine and rarely are responsible for UTIs. Urinary pathogens have their origin in the fecal flora. In women, the vaginal reservoir is a critical source of uropathogens. Bacteria enter the tract and ascend through the urethra and into the bladder.
The most common organism causing UTIs in all ages (except the neonate) is E. coli.27 This is true for the geriatric population as well. However, in the older nursing home population, it only causes 40-60% of cases compared to 80-90% of cases in community-dwelling elderly women.16 Other agents, such as Proteus, Klebsiella, Enterobacter, Serratia, Pseudomonas, and Enterococci, become more common in this age group. Common organisms, in order of frequency, are listed in Table 3. Men and patients with chronic urinary catheters have higher proportions of non-E. coli gram-negative rods and gram-positive organisms.16,20 Enterococcus is a particular concern in obstructed or instrumented men.28,29
| Table 3. Top Eight Organisms Causing Bacteremic UTI |
| 1) Escherichia coli |
| 2) Staphylococcus aureus* |
| 3) Klebsiella |
| 4) Proteus |
| 5) Enterococcus* |
| 6) Pseudomonas |
| 7) Enterobacter |
| 8) Citrobacter |
| = Listed in order of decreasing frequency |
| * = Gram-positive organisms |
Traditionally, a level of 100,000 colony-forming units (cfu) of one or more organisms that grows from one milliliter of urine has been considered a "positive" culture. In the presence of symptoms, lower counts may be significant.12 Recent studies suggest counts as low as 100 may be significant if the organism is a common uropathogen, the specimen is obtained by fresh catheterization, or the patient manifests pyuria or symptoms of UTI.12 Other factors that may influence the number of organisms isolated include hydration, urinary frequency, ureteral obstruction, or current antibiotic therapy.3
Presentation
UTIs in the elderly can present differently from those in younger adults. The classic lower tract symptoms of frequency, urgency, and dysuria, and the upper tract symptoms of chills, flank pain, and tenderness, may be altered or absent. Patients may lack fever and can even be hypothermic.10 While acute pyelonephritis in the elderly typically displays a septic syndrome manifested as a fever, tachycardia, and altered mental status, UTIs in the elderly present with a multitude of varying chief complaints.23 These include mental status deterioration, nausea, vomiting, abdominal pain, or respiratory distress.2,12 In community-dwelling adults older than 50 years, bacteremic UTI most commonly presented as confusion, cough, and dyspnea. New urinary symptoms were the chief complaint in only 20% of cases.2 In another study, only one-half of older bacteremic UTI patients were febrile. However, older patients were no more likely to be afebrile than younger bacteremic patients (40% of whom had normal temperatures).16 Because of the wide range of presenting symptoms, the misdiagnosis of UTI ranges from approximately 20% to 40% and is attributed to the patient presenting with non-urinary complaints.12,30
It may be clinically impossible to ascertain whether fever in the bacteriuric elderly patient lacking urinary symptoms is an invasive urinary infection. The majority of febrile episodes in the bacteriuric, non-catheterized elderly are unlikely to be due to invasive infection.8,31
Foul-smelling urine is sometimes considered a symptom in the elderly adult, especially in the institutionalized patient. Bacteria in the urine produce polyamines, which account for the odor, and antibiotic therapy may ameliorate the odor. However, use of antibiotics for this sole reason is not advocated.8 Management of incontinence and improved hygiene, especially in the institutionalized patient, will usually solve this problem.
Diagnosis
Since it is often difficult to clinically detect the source of an infection in the elderly population, it is important to sample the urine for analysis in older patients who are acutely ill. For both sexes, urine collection in a sterile container during normal voiding after cleaning the periurethral region with water is a reliable method for obtaining a sample.32 Midstream clean catch and catheterization methods of urine collection have a high concordance for findings of bacteria, positive tests for nitrites and leukocyte esterase, microscopic bacteriuria, and pyuria.33 This can help decrease the amount of catheterization in the elderly. Mixed flora found in midstream clean-catch urine samples suggest contamination, and should have a repeat specimen by catheterization if treatment is being considered.21
Pyuria is the hallmark of inflammation and is detected easily and reliably by the leukocyte esterase dipstick test or by finding 5-10 white blood cells (WBCs) per high power field in the urinary sediment. The absence of pyuria is a very good predictor for the absence of bacteriuria.34 Most patients with an infection will usually have more than 100 leukocytes. If the clinical suspicion of UTI is high, a leukocyte esterase dipstick test may be helpful since it has a high sensitivity. The positive predictive value of the test, however, will be decreased if used indiscriminately in cases where suspicion (and prevalence) is lower. These findings also are true for the dipstick test for nitrites.35,36
Microscopic and sometimes gross hematuria may be encountered in acute infection, but proteinuria is unusual. Gross hematuria is seldom attributable directly to hemorrhagic cystitis, despite a high prevalence of bacteriuria in institutionalized patients with gross hematuria.8,37
Due to the high prevalence of bacteriuria in the elderly, a positive urine culture has less positive predictive power for the diagnosis of symptomatic urinary infection. Therefore, a negative culture is more helpful in excluding an infection than a positive culture in diagnosing an infection.8 It is recommended that pretreatment cultures be obtained in the elderly since microbiology can vary and culture results can aid treatment.
Other laboratory tests, such as a WBC count, may be helpful in evaluating UTIs in the elderly population. However, normal WBC counts are not uncommon (up to 30% prevalence) even in patients with bacteremia. Among patients with community-acquired bacteremic UTIs, older patients were just as likely to have leukocytosis (WBC > 10,000/mm3) as younger patients (approximately 70% in both).16 In the debilitated non-ambulatory nursing home patient, however, an immunocompromised state may prevent leukocytosis. Five clinical and lab factors have been significantly and independently associated with bacteremia.38 These include serum creatinine, leukocyte count, temperature, presence of diabetes mellitus, and a low serum albumin. The clinical utility of these factors was limited, since calculating the probability of bacteremia required mathematical computation of these variables, and easy to use values or cut-points were not useful by themselves. However, the presence of these factors does indicate poorer host defenses, pre-existing renal disease, and increased likelihood of bacteremia, and should be noted when making treatment and disposition decisions.
Controversy exists about which elderly persons should undergo diagnostic testing for recurrent UTI. Some clinicians believe all should. Currently, it is recommended that patients at high risk for anatomical problems be investigated. It is important to take elderly women through diagnostic testing for recurrent symptomatic UTIs if there is any suspicion of urinary tract obstruction. Obstruction, if left untreated, can lead to renal parenchymal destruction, septic shock, and death. Obstruction should be suspected in a patient with persistent bacteremia, bacteriuria, and fever lasting more than 4-5 days after proper treatment has been initiated.3
Contrast studies, such as intravenous pyelography and excretory urography, should be used with caution in elderly patients since the contrast can lead to contrast nephropathy.21 Elderly patients at risk for contrast nephropathy include those with diabetic nephropathy, chronic renal insufficiency, or CHF.21 Although the reported prevalence of contrast-induced nephropathy is 0.1-12%, this rate substantially increases in patients with these predisposing risk factors.39 Prevalences ranging from 17% to 55% have been reported in patients with initial serum creatinine levels greater than 2 mg/dL.40 Patients with both renal insufficiency and diabetes mellitus are especially at risk, with rates of contrast-induced nephropathy approaching 90%.39 Better alternatives to contrast studies include ultrasonography, CT scans, and abdominal films, which have a greater than 95% rate of detecting kidney stones or obstruction.
Treatment and Disposition
Upper tract infections should be suspected in elders with fever, flank pain, or mental status changes. Older patients with pyelonephritis should be admitted and treated with parenteral antibiotics. These patients are much more likely to develop bacteremia (occurring in 66%) and urosepsis (developing in 22%) than younger patients.41,42 Appropriate antibiotic choices include third-generation cephalosporins (cefotaxime or ceftriaxone), ampicillin and an aminoglycoside, or high-dose fluoroquinolones. (See Table 4.) Ampicillin should be added if enterococcus is suspected (i.e., older male patients or gram-positive cocci in chains on urine gram stain). Hospital or nursing-home acquired gram-negative infections are often due to multiply antibiotic-resistant organisms, such as Pseudomonas aeruginosa. Empiric antibiotic therapy includes ciprofloxacin, ceftazidime, or aztreonam.
| Table 4. Treatment Options for UTI | ||||
| 1° | Days | 2° | Days | |
| Acute uncomplicated | TMP/SMX 1 tab bid | 3 | Doxycycline | 3 |
| UTI | Fluoroquinolone norfloxacin/norfloxacin/ofloxacin/levofloxacin) | 3 | Amoxicillin/clavulanate | 3 |
| Acute uncomplicated pyelonephritis | ||||
| Outpatient | Fluoroquinolone (PO) | 14 | Amoxicillin/clavulanate | 14 |
| Inpatient | Fluoroquinolone (IV) | 14 | Ampicillin/sulbactam | 14 |
| Ampicillin/gentamicin (IV) | 14 | Ticarcillin/clavulanate | 14 | |
| Cefotaxime (IV) | 14 | |||
Treatment should be considered for patients of any age with a symptomatic UTI. Strategies differ in the healthy, community-dwelling elder compared to the frail, institutionalized patient. Antimicrobial treatment should be determined by several factors, including susceptibility of the infecting organism, patient tolerance, severity of the illness, and cost. In the institutionalized elderly patient, there may be local patterns of infecting organisms or antimicrobial resistance that will direct antimicrobial choices.8
Short-course antibiotic therapy is less likely to be successful in the elderly patient and is not recommended in men. In one study of elderly women with UTIs, initial cure rates for single-dose and conventional 7- to 10-day therapy were similar (52% and 59%, respectively). Relapse rates were much higher with single-dose therapy (62% vs 48%, respectively).43 Elderly women are less likely to be cured by any duration of therapy compared to younger women. Relapse and recurrence are more common in elderly, institutionalized females.8,44
There are many options for treatment. (See Table 4.) Narrow spectrum antibiotics should be avoided since many organisms other than E. coli can be causative agents. In addition, nitrofurantoin appears to have an increased incidence of side effects (pulmonary reactions and blood dyscrasias) in older women and is not recommended in this group.45 There is now substantial evidence that short-course therapy (3 days) gives results comparable to longer (7- to 14-days) treatment courses in urinary infections confined to the bladder.19 For females, one option is giving a three-day treatment followed by re-treatment for 14 days if there is early recurrence (less than 4 weeks). However, seven-day treatment also is commonly suggested. Women who present with evidence of a more invasive infection like pyelonephritis should be treated for at least 14 days. Some authors suggest treating all symptomatic UTIs for 10-14 days, arguing that differentiating lower and upper tract infections can be difficult in the elderly female patient.21 A 14-day treatment also is appropriate for men unless they present with recurrent symptomatic UTIs. In this case, they may need between 6 and 12 weeks of therapy.
Many experts feel the use of antibiotics to prevent bacteriuria in high-risk patients (elderly female nursing home residents and those with indwelling urinary catheters) is not indicated because of the side effects, cost, and emergence of resistant bacteria. Although the indications for prophylaxis in patients undergoing urologic procedures are controversial, the purpose of treatment should be to prevent bacteria in the periurethral area from entering the bladder, and to avoid placing a catheter into an already infected space.46 There are, however, proven exceptions, including treatments recommended for renal transplant and granulocytopenic patients. (See Table 5.) For these patients, the goal of prophylaxis is to prevent unacceptably high morbidity and mortality rates associated with UTIs.46
| Table 5. Patients in Whom UTI Prophylaxis Is Recommended |
| • Women with uncomplicated recurrent UTI |
| • Spinal cord injury patients |
| • Neurogenic bladder |
| • Men with chronic bacterial prostatitis |
| • Renal transplant patients |
| • Pre-op for urologic and gynecological procedures |
Asymptomatic Bacteriuria. Simple bacteriuria in the elderly in the absence of UTI symptoms and obstruction is referred to as asymptomatic bacteriuria. It is usually quantitatively defined using microbiology results similar to those for UTI (105 cfu). Studies have been done that evaluate the need for screening the elderly population for bacteriuria and, in turn, treating asymptomatic bacteriuria in this population.8 Most of these have found asymptomatic bacteriuria to be benign and do not recommend treatment.8,47-49 There are several reasons for this. First, symptomatic disease rarely develops from asymptomatic infection.47 The recurrence rate for asymptomatic bacteriuria after therapy is high in the elderly and it remains to be seen if extended infection-free intervals can be maintained. Finally, the adverse reaction rate to antimicrobial agents in this population is high, and there is no clear evidence that asymptomatic bacteriuria results in increased morbidity or mortality.47
However, there is clear indication for treatment of asymptomatic bacteriuria for both institutionalized and non-institutionalized patients when subjects are to undergo an invasive genitourinary procedure. The presence of infected urine predisposes procedures with mucosal trauma to have a high likelihood of post-procedure bacteremia and, in some instances, death from septic shock.8
Urinary Incontinence. Urinary incontinence is defined as the involuntary loss of urine.50 Incontinence in the presence of bacteriuria occasionally is used as an indication to treat with antibiotics, presuming the incontinence will improve with eradication of bacteriuria. However, it has been shown that incontinence and bacteriuria are unrelated, and symptom scores of incontinence are not increased by asymptomatic bacteriuria.51 An increase in incontinence should not be used as an indication to treat asymptomatic bacteriuria.47 Chronic incontinence has not been shown to result from UTIs, even though many incontinent patients have bacteriuria.23
Indwelling Catheters. There are many reasons for urethral catheterization, including surgery, urine output measurement, urine retention, and urinary incontinence. Approximately 5% of the institutionalized elderly population have a chronic, indwelling urinary catheter. The incidence of bacteriuria seems to be of the same magnitude as that found in the hospital setting, about 3-10% a day.52 Therefore, most patients will have bacteriuria by the end of a 30-day catheterization.52
Urine obtained through a catheter may not always reflect bladder urine.46 Catheter urine contains organisms which may not be present in the bladder. This has been proven by comparing catheter specimens with suprapubic aspirate.52 Urine specimens should be obtained by needle and syringe without opening the catheter-collection tube junction.
Complications associated with short-term catheter use include symptomatic UTIs, trauma, urethritis, bacteriuria, pyelonephritis, and bacteremia. Table 6 outlines risk factors for catheter-associated bacteriuria.10,23 Even after catheter removal, the patient may remain at risk for bacteriuria for at least 24 hours. Long-term catheterization is associated with catheter obstruction, nephrolithiasis, chronic renal inflammation, renal failure, and bladder cancer. Complications specific to men include urethritis, urethral fistulae, epididymitis, scrotal abscess, and prostatitis. Two-thirds of febrile episodes in elderly, long-term catheterized patients are caused by UTIs.52 Most episodes last for fewer than 24 hours and resolve without antibiotic therapy or catheter change.52
| Table 6. Independent Risk Factors and Preventative Options for Catheter-Associated Bacteriuria Risk Factors |
| • Duration of catheterization |
| • Absence of urimeter use |
| • Colonization of drainage bag |
| • Diabetes mellitus |
| • Absence of antibiotic use |
| • Female |
| • If used other than for surgery/output |
| • Abnormal serum creatinine |
| • Errors in catheter care |
| Preventative Options |
| • Condom catheters |
| • Intermittent catheterization |
| • Suprapubic catheterization |
Catheter hygiene is universally recommended and includes maintaining a closed catheter system. The use of systemic antibiotics may postpone bacteriuria in the catheterized patient. Approximately 80% of patients are administered systemic antibiotics at some time during their catheterization.52 This is usually done as prophylaxis for surgical operations or treatment of non-urinary infections, not as prophylaxis against a UTI.52
Many treatments have been suggested for bacteriuria associated with catheters, but discontinuing the catheter is the only effective method of eradicating the bacteria. Intermittent catheterization has shown a much lower infection rate.54 Other catheterization options to prevent bacteriuria are listed in Table 6.
Alternative/Behavioral Treatment. Interventions that might be suggested to the elderly patient for help with avoiding UTI include: voiding upon urge, increasing overall fluid intake, and drinking cranberry juice.46 Cranberry juice has been studied in postmenopausal women with asymptomatic bacteria and has been shown to help if 300 mL is ingested per day. The juice contains substances that inhibit the adherence of a uropathogenic E. coli isolate to uroepithelial cells.46 Prevention of recurrent UTIs among postmenopausal women can sometimes be accomplished by topical estrogen replacement therapy.46
Recurrent UTIs
There are two main hypotheses to explain recurrent UTIs. The first is that women who experience recurrent UTIs have defective local defense mechanisms, which makes them more susceptible to periurethral colonization. The second hypothesis suggests that the first UTI changes host resistance.
Recurrence of UTIs is more common in women older than age 55.44 If treatment of a UTI does not result in the elimination of the bacteria, then these strains tend to cause recurrences for a long time. They also are associated with resistance to antimicrobial therapy.48
Conclusion
The elderly population is immense and will continue to grow over the next few decades. Therefore, it is extremely important to understand the medical problems of this age group. Infections will continue to be a major component accounting for emergency visits. The emergency physician needs to understand the signs and symptoms associated with UTIs in the elderly and how they differ from the younger population. Physicians also need to be able to interpret a urinalysis with respect to these symptoms. This is especially true if there is an indwelling catheter. Asymptomatic bacteriuria is common in the elderly, occurring more often in women and in the functionally impaired. Diagnostic and treatment options for all patients need to be made on an individual basis for the best benefit of the patient.
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