Urinary tract infections

Urinary tract infections are very common. For women, there is a one-in-three lifetime incidence of urinary tract infection. Prevalence increases with age in both men and women.

Pathogenesis

Lower urinary tract infections generally present as cystitis, which is an infection of the superficial bladder lining. Access via the urethra is the most common mechanism by which pathogens such as Escherichia coli infect the bladder. E. coli accounts for 80–90% of infections. Other pathogens include Staphylococcus saprophyticus (5–10%), enterococci, Proteus mirabilis and other enteric Gram-negative rods such as Klebsiella species.

Presentation

The presenting features of lower urinary tract infection include frequent urination or an urgent need to urinate, painful urination, pain in the lower abdomen above the pubic bone and cloudy or foul-smelling urine. Fever and generalised lower back pain may also be present. Flank pain accompanied by systemic symptoms such as fevers, rigors, nausea and vomiting may suggest an ascending infection or pyelonephritis. In elderly patients, confusion may be the only presenting symptom.
Symptoms consistent with cystitis may also be caused by other conditions such as pelvic inflammatory disease, sexually transmitted diseases, bladder cancer and bladder stones.

ADDITIONAL INFORMATION

Investigations

Antibiotic treatment MAY be commenced immediately for symptomatic cystitis, HOWEVER, formal urine testing should be performed in most circumstances to ensure the most appropriate antibiotic is selected, especially given the rising incidence of antibiotic resistance. This is particularly important in men, pregnant women and patients with recurrent infections.

Blood cultures should be taken if there are signs of sepsis (infection in the blood) or an unusual organism in the urine, such as S. aureus.

Ultrasound of the urinary tract should be done for patients with recurrent infections to check for upper urinary tract abnormalities and urinary stones. It is also indicated in older men to check for bladder outlet obstruction and residual urine volume post-voiding. Patients with persistent blood in the urine following resolution of a urinary tract infection should have a cystoscopy and evaluation of the upper urinary tract. This is usually done with a CT urogram.

Treatment

Most urinary tract infections require antibiotics. However, there is progressive development of antimicrobial resistance to common antibiotics in Australia and overseas. Antibiotic choice is therefore guided by knowledge of local resistance patterns.

Uncomplicated urinary tract infections

Uncomplicated infections should almost always be treated with antibiotics to decrease length and severity of symptoms. A 3 to 5 day course of trimethoprim, cephalexin, or amoxycillin/clavulanate can be used for the majority of acute, uncomplicated infections, in the absence of previous antibiotic exposure or other risk factors such as recent travel to high-risk areas. Nitrofurantoin is an option in short-course therapy for cystitis, especially when drug resistance is present. However, long-term use should be avoided, especially in older patients as side effects can occur with impaired renal function. Fluroquinolones (for example norfloxacin and ciprofloxacin) should be considered second-line and restricted to patients with culture-proven resistant organisms.

Recurrent urinary tract infections

Risk factors in adults with recurrent urinary tract infections include sexual activity, contraceptive devices (such as intrauterine devices), hormonal deficiency in postmenopausal women, diabetes, foreign objects (including bladder calculi), and urinary tract obstruction (including benign prostatic hyperplasia or pelvic organ prolapse). Recurrent infections can be due to bacterial persistence or re-infections. It is important to have an adequate course of antibiotics and repeat urine tests after treatment is completed to ensure complete resolution. An ultrasound of the urinary tract should be considered to exclude structural abnormality and document complete bladder emptying. Therapeutic strategies include low-dose antibiotic prophylaxis and patient-initiated antibiotics guided by symptoms, although this should be only undertaken following urological assessment by Dr Ruban, as long-term antibiotics should preferably be avoided.

Strategies to prevent recurrence

Topical vaginal oestrogen therapy and alkalinising agents such as Ural® may provide symptomatic relief and are often used as preventative strategies. However, they do not necessarily have any impact on reducing recurrent infections. Alternative therapies such as probiotics, cranberry tablets or juice are often advocated for prevention but may not be effective. If recurrence is associated with sexual activity, the bladder should be emptied immediately after intercourse.

Complicated urinary tract infections

When stone disease, pyelonephritis, prostatitis, (epididymo)orchitis or neurogenic bladder is confirmed or suspected, further evaluation is recommended to exclude anatomical abnormalities and urinary obstruction that may require surgery. Infections associated with urinary tract obstruction, such as pyelonephritis due to an obstructing kidney stone, are a medical emergency. These patients require urgent hospital admission and surgical drainage with placement of a nephrostomy tube or stunting of the ureter/s. It is important that patients with complicated urinary tract infections are prescribed an adequate course of antibiotics – usually for at least 10–14 days.

Patients with a catheter

The urinary tract is the most common source of hospital-acquired infection, especially in patients with catheters. In these patients, presence of bacteria in the urine is expected within a few days due to colonisation, although in the short term it comprises a single organism and does not usually cause symptoms. Catheterisation for longer than 30 days is associated with colonisation with multiple organisms.

Catheterised patients in whom bacteria are detected in the urine, should only be treated if they are symptomatic or about to undergo a urological procedure. Such signs or symptoms may include fever, rigors, delirium, malaise, lethargy with no other identified cause, flank pain, blood in the urine, or pelvic discomfort. Pus in the urine alone does not confirm a catheter-associated infection. The catheter should be changed at the time of antibiotic treatment.

Recurrent catheter-associated urinary tract infection may be reduced by careful catheter handling and management, removal of unnecessary catheters, and changing to a suprapubic catheter. There is a role for low-dose preventative antibiotics in patients susceptible to severe infections or sepsis after common causes for recurrence, such as poor catheter care or bladder stones, have been excluded. This should generally only be undertaken with specialist urological input due to the risks of long-term antibiotic use.