UTIs in adults

Contributed by Dr Pushpam Chadha, GP locum in London and and Dr Josip Car, post-doctoral research fellow, department of primary care and social medicine, Imperial College London.

1. EPIDEMIOLOGY AND AETIOLOGY

Epidemiology

UTIs are the second most common infections in women, affecting up to 15 per cent of women each year.

More than 25 per cent of women who have had a UTI will experience a recurrence.

In contrast UTIs are uncommon in men, affecting mainly those at the extreme of ages, such as those under the age of one and those over 60.

In acute cystitis in young women, a previous history of cystitis, frequent or recent sexual activity represent important risk factors. The relative odds of acute cystitis increase by a factor of 60 during the 48 hours after sexual intercourse.

The use of spermicidal agents increases the odds of infection with Escherichia coli and Staphylococcus sapro-phyticus by a factor of two to three.

Pregnancy, especially in the second and third trimester, also increases the risk of developing a UTI due to hormonal changes modifying the genito-urinary tract.

There is substantial evidence that UTIs are one of the most common reasons for presentation to general practice. Therefore, there are important implications for both clinical and cost management of the condition.

Aetiology UTI may be either uncomplicated - caused more often than not by E coli and by Staph saprophyticus and other enterobacteria in the rest of cases - or complicated.

Complicated UTIs are mainly caused by enterococci, however the anatomical and complicating factors predispose to persistent infection, recurrent infection or treatment failure.

However, it important not to be complacent about treating uncomplicated UTIs because there is a risk of their becoming complicated UTIs.

Complicated UTIs can rapidly lead to renal scarring, renal failure and, in the worst case scenario, death, especially in high risk groups such as the elderly or those with co-morbidities.

Classification

Multiplication of organisms in the urinary tract may result in symptoms such as urinary frequency, dysuria and supra-pubic pain.

Clinical management of the infection is guided by distinguishing a classification of either an infection of the lower urinary tract (cystitis) or that of the upper urinary tract (pyelo-nephritis).

2. DIAGNOSIS

The diagnosis depends on characteristic clinical features and the demonstration of either a positive dipstick test or urine culture. Patients with recurrent infections can accurately self-diagnose a lower UTI.

Clinical features

It can be difficult to find a clear pattern of symptoms and signs, particularly in the evolving phases of the infection (see below).

Although we need better evidence for the validity of dipstick analysis a reasonable approach is to treat on the basis of a positive dipstick for nitrites and leucocytes.

Investigations

Investigations for pyelonephritis may include a pelvic examination, urinalysis and urine culture.

If the dipstick is positive for blood then microscopic examination should differentiate between haematuria and haemaglobinuria and detect casts.

A dipstick positive for nitrites/leucocytes confirms infection; if there are more than 20 epithelial cells per high powered field then there is contamination with vaginal secretions.

If the dipstick is negative, an infection cannot be ruled out if the pre-test likelihood is high.

A urinary culture confirms diagnosis but it is not necessary for most patients with consistent symptoms and a positive dipstick.

Urine culture also identifies unusual or resistant organisms in women whose symptoms either do not abate or recur within two to four weeks of treatment.

Urinary culture is necessary when there are predisposing factors for an upper tract or complicated infection such as hydronephrosis or atonic bladder; clinical features of pyelo-nephritis; failure to respond to empirical treatment; pregnancy and urolithiasis.

A GUIDE TO DISTINGUISHING FEATURES

Cystitis

  • Urinary frequency (average person urinates six times/day)
  • Urgency
  • Haematuria
  • A change in the smell of urine
  • Suprapubic pain
  • Strangury (slow painful urination due to spasms of the urethra and bladder

Pyelonephritis

  • Fever
  • Rigors
  • Vomiting
  • Loin pain/tenderness (a renal mass may be indicative of a renal tumour)

3. MANAGING THE CONDITION

Current treatment

The management should be centred around the decision of whether to prescribe antibiotics or rely on alternative measures.

Randomised control trials suggest that drinking 200-750ml of cranberry or lingoberry juice or taking cran-berry concentrate tablets reduces the risk of symptomatic, recurrent infection by 10 to 20 per cent.

However, there is no evidence to support other non-pharmacological measures, such as post-coital voiding, attempts at improving poor hygiene, specific instructions regarding the frequency of urination, the timing of voiding, wiping patterns, douching, the use of hot tubs, or wearing of tights.

Empirical treatment

Prophylaxis is rarely considered. If the symptoms are atypical, urinary dipstick will help prevent unnecessary prescriptions and thereby help in the prevention of antibiotic resistance.

First choice

Trimethoprim is the first choice of drug treatment, except in women from communities with a high rate of resistance, when following local microbiological guidelines will be most appropriate. A three-day course should suffice.

Single dose treatment, which has a smaller side-effect profile, can be used but is a less effective option.

If despite treatment the patient's symptoms persist or worsen, a urine culture should be performed and antibiotics should be prescribed according to the results of the culture and sensitivity tests.

Mild upper UTIs can be treated with oral antibiotics for seven to 10 days with an early review.

Patients who become systemically unwell should be admitted.

Bacteruria in pregnancy

Treatment options for asymptomatic and symptomatic bacteruria in pregnant women include oral amoxicillin 250-500mg every eight hours for 10 days or with nitrofurantoin 100mg every 12 hours for seven days. Cephalexin and ampicillins are alternatives.

Follow up with monthly urine cultures until delivery. Group B streptococcal infections should be treated intrapartum.

Paracetamol can be used as pain relief for abdominal pain.

Bacteruria in the elderly

Asymptomatic bacteruria in the elderly is not associated with increased morbidity.The treatment of diabetics with asymptomatic bacteruria is complex and the evidence is limited for a consensus on a best approach.

KEY POINTS

- It is important to differentiate between cystitis and pyelonephritis.

- Search for the right combination of symptoms. Dysuria and frequency without vaginal discharge or vaginal irritation are highly suggestive of cystitis.

- Perform a urine culture in patients with suspected pyelonephritis, patients who fail to respond to first-line antibiotic treatment and on all pregnant women who present with suggestive symptoms.

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