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Urinary tract infections in the over 75s

Key learning points:

- During diagnosis taking history is vital

- Some older patients have bacteria in their urine, but are asymptomatic; this does not routinely require treatment with antibiotics

- If a patient has a definite catheter associated UTI with symptoms (e.g. pyrexia) and raised inflammatory markers - treat with antibiotics for seven days and consider changing the catheter

Older adults are more prone to develop urinary tract infections (UTIs) than younger individuals. This is due to a number of reasons: incomplete bladder emptying (e.g. due to prostate enlargement), increased susceptibility to infection due to frailty and higher risk of catheter use.

UTIs are the second most common clinical indication for empirical antibiotics in primary care (after chest infections). The diagnosis of a UTI is more difficult in elderly patients, who are more likely to have asymptomatic bacteriuria (ASB) and elderly people are more likely to receive unnecessary antibiotic treatment leading to adverse events - e.g. clostridium difficile infection (CDI) or Methicillin resistant staphylococcus aureus (MRSA) infection and the development of antibiotic resistant UTIs. The purpose of this article is to give practice nurses guidance to improve the diagnosis and treatment of UTIs in patients over 75 years and to avoid adverse effects of treatment.

Why diagnosing a UTI is more difficult in older people

One of the major difficulties with diagnosis of UTI in older people is the high prevalence of ASB: the presence of bacteria in the urine of people without symptoms. ASB is present in around 10% of men over 75 years and around 20% of women over 75 years, and in up to 50% of non-catheterised people in care homes. All long-term catheter users have bacteriuria. ASB is associated with white blood cells in the urine in more than 90% of cases. Treating ASB in older adults does not reduce either mortality or morbidity, but does increase the risk of antibiotic related adverse events. A second major diagnostic difficulty is that patients over 75 presenting with a UTI may not have urinary tract symptoms. Older people may present non-specifically with acute functional decline or delirium. Also, cognitive impairment (dementia or delirium) may make it difficult to take a reliable history. In such cases the nurse may have to rely on other investigations and signs to diagnose a septic illness - for example pyrexia, raised serum white cell count or raised CRP in the absence of an alternative more likely explanation (e.g. a chest infection). Finally, the infecting organism in UTIs in people over 75 is likely to be different than in a younger person. Escherichia coli (E.coli) accounts for 80% of UTIs in young women, but less than 60% of UTIs in people over 75 years old.

Alternative organisms implicated include other gram-negative rods (e.g. Klebsiella, proteus and pseudomonas), gram-positive cocci (staphylococci, streptococci and enterococci) and occasionally fungi, such as candida. Gram-positive organisms account for 10-20% of UTIs in the elderly. Catheterised patients have higher rates of proteus mirabilis, pseudomonas and gram-positive organisms. Generally speaking, the more frail the patient the less likely that a coliform (e.g. E.coli) will be the cause. Ideally, a urine culture should be obtained in all older patients to guide treatment. The possible different causes of a significant bacterial growth (greater than 100,000 bacteria) are shown in Table 1 and include ASB, which does not require treatment.

Assessment and treatment

The basic first step is to take a history. Does the patient have a new onset of dysuria, frequency, urgency, haematuria, suprapubic pain or tenderness, flank pain or renal angle tenderness? (see Table 2). If so, a UTI is likely and it is reasonable to start treatment with an antibiotic, sending a urine sample to the laboratory if possible. For a simple urinary tract infection (see Table 1) then a three day course of an antibiotic is reasonable. The type of antibiotic is guided by your local guidelines, but common choices are trimethoprim or nitrofurantoin for three days. Nitrofurantoin, however, is ineffective if there is renal impairment (eGFR

Sometimes in patients over 75 it is not possible to get a clear history, particularly if the patient has delirium or dementia. In this situation it is advised that if there is clear evidence of a septic illness with raised C-reactive protein and a raised white cell count, and/or a temperature and no other obvious cause of sepsis (e.g. a chest infection) then it is reasonable to treat for a complicated UTI (see Table 2) with a broad spectrum antibiotic for seven days. If the patient has a presumed catheter associated UTI then consideration should be given to changing the catheter, as well as treating with antibiotics. 

It is important to note that urine dipstix tests are unreliable in older patients and play no part in the diagnosis of a UTI. This is because the finding of blood and protein is very non-specific and can occur in many other infections. Similarly, the nitrite test and the leucocyte test can be positive in asymptomatic bacteriuria. The nitrite test is dependent on bacteria in the urine transforming nitrates to nitrites. However, it requires the bacteria to be in contact with the urine for sufficient time to do this, and also many organisms that cause UTIs in older people do not have the ability to convert nitrates to nitrites - hence this test can give both false positives (e.g. asymptomatic bacteriuria) and false negatives in older people. If an older patient has recurrent documented UTIs then imaging of the urinary tract is recommended to check for a structural abnormality (e.g. an ultrasound to check for poor bladder emptying in a man due to an enlarged prostate). Cranberry juice has proven benefiticial in preventing urinary tract infections, but may interact with some drugs (e.g. warfarin).


UTIs are common in patients over 75 years. Correct assessment and treatment depends on taking a careful history and starting empirical antibiotics, depending on the history or evidence of infection with raised inflammatory markers (pyrexia, raised white cell count and raised CRP), and no better explanation than a UTI (e.g. a chest infection). Urine dipstix and routine urine examination are not helpful, but urine examination for bacteria and sensitivities in a clinically suspected UTI can help guide treatment. Many older patients are treated unnecessarily for UTIs when in fact they have asymptomatic bacteriuria, which does not require antibiotics. This increases the risk of MRSA and clostridium difficile. The practice nurse, who works very much on the front line in primary care, can help reduce adverse effects in the community from indiscriminate antibiotic use.


1. Woodford H J, George J. Diagnosis and management of urinary infections in older people. Clinical Medicine, 2011, Vol. 11; No. 1: pp 80-83.

2. Rowe T A, Juthani-Mehta M. Diagnosis and Management of Urinary Tract Infections in Older Adults. Infectious Disease Clinics of North America, 2014, March 28 (1); pp 75-89.