Pregnant women have a higher prevalence of asymptomatic bacteriuria. In the non-pregnant woman, asymptomatic bacteriuria appears to be intermittent and self-limiting, but 4 – 7% will have bacteriuria throughout pregnancy. It is thought that pregnant women are more prone to asymptomatic bacteriuria because the higher urinary pH allows more rapid colonization by E. coli. The progestogen effect on smooth muscle allows relaxation of the urethral meatus, giving both easier ascent of uropathogens into the bladder, and more frequent reflux to the kidneys, causing a higher percentage of complicated upper urinary tract infection (Medicine’s Resource Centre Bulletin). For women with asymptomatic bacteriuria in pregnancy, there is a significant risk that they will experience a symptomatic urinary tract infection, with obstetric complications of possible premature labour, small-for-dates babies, and an increased perinatal mortality.
Routine screening of pregnant women for asymptomatic bacteriuria is advised in the 16th week of pregnancy, with an mid-stream sample of urine (see above). If asymptomatic bacteriuria is found in these women, treatment should be given to prevent acute pyelonephritis. Pregnant women with asymptomatic bacteriuria should receive at least 7 days” treatment with an antibiotic. Most pregnant women are heavily indoctrinated not to take any drugs during pregnancy. The general practitioner must explain to the woman why she needs to be treated for an asymptomatic condition in the pregnancy, or compliance may be low, with disastrous results. Nitrofurantoin (except at term), amoxicillin and the older cephalosporins are thought to be relatively safe in pregnancy and are commonly used as first-line agents, depending on the sensitivity of the uropathogen and the allergies of the patient. Various antibiotics are not recommended in pregnancy (the quinolones, co-amoxiclav) as the potential risk to the fetus is thought to be more harmful than the potential benefit to the woman. Tetracycline should be avoided in pregnancy as they colour the fetal teeth and bones. Trimethoprim has a theoretical teratogenic risk as it is a folate antagonist, and should be avoided in the first trimester.
If there are problems with bacterial sensitivities of urinary tract infection in pregnant women, specialist advice from the local medical microbiologist should be sought. A pregnant woman with the signs of an acute pyelonephritis should be referred for hospital admission as she will probably require intravenous antibiotics.
Asymptomatic bacteriuria is 40 times more common in the diabetic woman than the non-diabetic. Fungal urinary tract infections are also slightly more common as the glycosuria encourages fungal and bacterial growth. The high urinary glucose also impairs leucocyte phagocytosis. There may be an autonomic neuropathy in long-term diabetics which impairs bladder emptying, predisposing to recurrent infections. Up to 50% of diabetics have upper renal tract involvement. Long-term prophylaxis may be required in this group if there are proven underlying anatomical abnormalities, including significant residual urine due to a neurogenic bladder. Certainly diabetics should be treated immediately if there is a symptomatic infection, and some would argue for routine screening and treatment of asymptomatic patients in this subgroup.
Urinary tract calculi
Stones in the urinary tract irritate the mucosa, which promotes bacterial adherence and colonization. The stone itself also acts as a focus for bacterial persistence. urinary tract infections, in the presence of calculi, are more often caused by Proteus mirabilis, and other unusual organisms such as Ureaplasma urealyticum, Klebsiella pneumoniae, and Pseudomonas aeruginosa. The flora may give the clue to reveal an occult urinary tract calculus, particularly if Proteus is present. It is impossible to cure a urinary tract infection with antibiotics whilst there is a stone present. Bacteria are released from secluded sites deep in the stone, so relapse is inevitable. Treatment requires a urological referral to disrupt the stone by ultrasound, or surgical removal.
There is a rapid rise in the prevalence of urinary tract infections in postmenopausal women. Women over the age of 60 have an incidence of 15% urinary tract infections per year. In the postmenopausal woman, lactobacilli disappear from the vaginal introitus and the pH of the vagina rises. This favours colonization by E. coli. Entry of uropathogens into the urethral meatus may be facilitated by a urethral caruncle, and bladder and uterine prolapse cause a stagnant pool of residual urine after voiding. The vaginal and urethral mucosa is atrophic and more vulnerable to colonization with E. coli.
In a double-blind, placebo-controlled trial of intervaginal oestriol cream in postmenopausal women, episodes of bacteriuria were measured. Over an 8-month period, there was a considerable reduction in the frequency of asymptomatic episodes in the women using oestriol cream (nightly for 2 weeks and then twice weekly for 8 months). Of the 50 women in the treated oestriol group, there were 12 episodes of bacteriuria; the 43 in the placebo group had 111 episodes of bacteriuria (P < 0.005). Some women withdrew from the treatment group because of pruritis and burning from the oestriol cream. The mean vaginal pH fell from 5.5 to 3.6 in the treated group, and the re-oestrogenized women became recolonized with lactobacilli. Lactobacilli produces lactic acid, which lowers the pH of the vagina and discourages growth of uropathogens. If the vaginal pH is less than 4.5, E. coli do not colonize the mucosa. It has also been found in in vitro experiments, that fragments of lactobacilli cell wall actually prevent attachment of E. coli to epithelial cells. At present it is not known whether this is by stearic hindrance or specific blocking of potential attachment sites.
Although urogenital ageing has been an entity for as long as there have been women that have survived to the postmenopausal period, this is a renewed area of interest at present due to the sudden profusion of local oestrogen treatments (oestrogen pessaries, creams, and rings). There is also full systemic hormone replacement therapy (hormone replacement therapy) without the necessity for monthly withdrawal bleeds, a factor that had previously discouraged many postmenopausal women from continuing on medication. The use of hormone replacement therapy in postmenopausal women who do have recurrent urinary tract infections should be considered, and the pros and cons discussed with the patient.
There are data to suggest that if we routinely gave elderly women daily cranberry juice, there would be a significant reduction in bacteriuria and pyuria, with fewer symptomatic urinary tract infections. In one study, 153 elderly women (mean age 78.5 years) enrolled in a double-blind trial of drinking 300 ml fruit juice with vitamin C, with or without cranberry content. Their voided urine study samples were collected at monthly intervals. Bacteriuria (>105/ml) with pyuria was 42% less after 2 months of cranberry juice, in the cranberry juice group than in the controls. Also over a 6-month period there were 16 symptomatic urinary tract infections in the control group, and 8 in the treated group. The pH of treatment group urine was 6.0, with the mean pH of the control group of 5.5: so this is not an acidification effect.
This is really a very complex topic, and most studies have looked at acutely ill people in the hospital setting, rather than the few, very disabled people that have urinary catheters for chronic problems in the primary care setting. Some helpful conclusions can be drawn from US data: 25% of hospital patients have a urinary catheter sometime during their stay; 5% of those catheterized will acquire a bacteriuria per day. Thus, after 1 month nearly all will be bacteriuric. The case-fatality rate from urinary tract infection-related bacteraemia is 13%; only intravascular catheters lead to more cases of bacteraemia. Lack of proper hand-washing by health-care professionals was largely responsible for cluster outbreaks in the hospital setting, but most nosocomial urinary tract infections reflect endemic acquisition.
- Avoid using a urinary catheter whenever possible. When used, remove as soon as possible. Inserting a catheter for the convenience of the nursing or medical staff is rarely appropriate.
- Always insert the catheter aseptically, use a closed drainage system, and properly maintain the catheter.
- Consider prophylactic systemic antibiotics only during short-term catheterizations (3 – 14 days) of patients at high risk for complications of catheter-associated bacteriuria. Most experts do not recommend routine prophylaxis for catheterized patients because of cost, potential adverse reactions, and encouraging antibiotic resistance.
- Consider using a silver alloy catheter in patients at high risk of complications, where catheter placement is relatively short term (<2 weeks).
- Suprapubic catheters may be desirable in patients needing long-term catheterization.
- A condom catheter may be sensible for incontinent men who will not manipulate the device.
- There is no good evidence that bladder irrigation, antibacterial instillation in the drainage bag, rigorous meatal cleaning, and use of meatal lubricants or creams prevent bacteriuria. They should not be used.
Recurrent simple urinary tract infections in the premenopausal woman
This group of women can have their lives made miserable by recurrent infection. Twenty per cent of women with urinary tract infections have more than two urinary tract infections in 6 months, or three or more urinary tract infections in 12 months. For a woman with persistent recurring infections, an ultrasound of the urinary tract to exclude a stone or an obstructive uropathy may be reasonable, and a referral for cystoscopy if she has persistent haematuria. However, a cause is rarely found. Excretory urography and cystoscopy in women with recurrent urinary tract infections demonstrates anatomical abnormalities in less than 5%, with extremely few correctable lesions. There are three management strategies for women with recurrent urinary tract infections: postcoital prophylaxis, intermittent self-treatment, and continuous prophylaxis.