The basics - Urinary tract infection in adults

The presentation of a urinary tract infection is not always consistent, says Dr Harry Brown.

A positive urine dipstick and clinical examination may provide sufficient evidence to initiate treatment (Photograph: SPL)
A positive urine dipstick and clinical examination may provide sufficient evidence to initiate treatment (Photograph: SPL)

UTI is a relatively common problem. It may be considered a minor nuisance in many cases but in some situations it can lead to Gram-negative septicaemia, renal disease or recurrent infection and therefore could result in considerable morbidity.

It can be subdivided into lower UTI (cystitis), when the bladder alone is involved and upper UTI (pyelonephritis), when the kidneys are involved.

UTI is more common in women compared with men and children. Women can experience a UTI when the urinary tract is structurally and anatomically normal.

However this may not always be the case in men and children, and an underlying cause may be suspected.

1. Causes
Infection often arises from the patient's own colonic flora ascending deeper into the urinary tract via the urethra.

Escherichia coli is a common pathogen; other less common pathogens include Proteus mirabilis, streptococcus and klebsiella. Infection can also spread from the bowel, the lymphatics, the bloodstream or directly from an adjacent organ.

Some organisms have intrinsic properties that allow them to be more pathogenic in the urinary tract.

For example, some are able to adhere to the urinary tract epithelium or produce toxins which can help overcome host immunological responses.

Furthermore, some bacteria are resistant to commonly used antibiotics and this can vary by locality. For this reason, doctors should be aware of local antibiotic-resistant patterns when prescribing.

In addition, patient risk factors may increase the possibility of experiencing a UTI (see box).

Risk factors
  • Diabetes
  • Pregnancy
  • Sexual activity
  • Urinary catheterisation
  • Calculi within the urinary tract
  • Abnormality within the urinary tract

2. Symptoms and signs
The presentation of UTIs is not always consistent and the symptoms alone cannot confirm or refute the diagnosis. The symptoms of a lower UTI include dysuria, frequency, and lower abdominal and back pain and sometimes patients report that their urine has an unpleasant odour.

In the elderly, a presentation can be less specific and can include confusion. Patients with pyelonephritis may be systemically unwell with pyrexia and pain in the loin. If the patient is particularly ill, they may need hospital admission, especially if they are vomiting and unable to tolerate oral medication.

It is not possible to specify the precise anatomical site of the infection based on symptoms alone. The presence of haematuria should always be taken seriously, even in the context of a UTI. Microscopic or visible haematuria always should be investigated further.

UTI is uncommon in men aged under 50 years but the incidence rises with increasing age due to incomplete bladder emptying, possibly secondary to prostate problems.

Dysuria could also indicate urethritis caused by an STI, such as chlamydia, so this should be considered, particularly when dealing with younger, sexually active patients.

3. Diagnosis
Diagnosis will depend on the age, sex and medical history of the patient. For example, in an otherwise well young non-pregnant female, a positive urine dipstick with a suggestive history and clinical examination may be sufficient evidence to initiate treatment.

Laboratory culture of the MSU is considered the gold standard but may not always detect an infecting organism.

Requesting an MSU may not always be necessary in every situation, such as in a young woman who is not pregnant.

4. Management
General management includes increasing fluid intake. There have been suggestions that cranberry juice may reduce the risk of a UTI as it is thought that elements of cranberry juice can affect the ability of E coli to attach to cells.

Generally speaking, treatment with antibiotics is only suggested when the patient is symptomatic because unnecessary use of antibiotics may lead to the emergence of resistant organisms.

Commonly used antibiotics include trimethoprim, amoxicillin, nitrofurantoin and quinolones. A three-day course of oral antibiotics should help in many cases, but this depends on the clinical situation.

Always check that a female patient of reproductive age is not pregnant because this is important in prescribing suitable antibiotics.

In pregnancy, the urine of all pregnant women is routinely tested as part of the antenatal screening programme.

A significant number may have asymptomatic bacteriuria, which in the non-pregnant state usually does not cause a problem in the affected woman.

However, for pregnant women there is a significant risk of symptomatic infection which can be associated with premature labour, so treatment is advised.

Interstitial cystitis is not common but can affect women who are over the age of 40 years and can cause similar symptoms to a UTI, particularly suprapubic pain. No growth is obtained from urine cultures and these patients may need further investigation, such as a cystoscopy.

An uncomplicated single episode of a UTI in a patient who is not at risk may not require further investigations.

However, men, children, those with recurrent urine infections or patients with infection associated with an uncommon pathogen may require further investigations.

Depending on the situation, this could include routine haematological and biochemical blood tests (for example, a PSA in the older man and tests of renal function) and imaging of the urinary tract.

If the person is acutely ill with a possible acute pyelonephritis, then consider hospital admission depending on the clinical and social circumstances. In certain situations, such as ongoing visible haematuria, urology referral may be necessary under the two-week rule.

Recurrent UTIs may prompt the practitioner to consider further investigations to look for an underlying cause and in certain situations, this may require regular prophylactic antibiotics.

  • Dr Brown is a GP in Leeds

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