Urinary-tract infections

5.1.13 Urinary-tract infections

Urinary-tract infection is more common in women than in men; when it occurs in men there is frequently an underlying abnormality of the renal tract. Recurrent episodes of infection are an indication for radiological investigation especially in children in whom untreated pyelonephritis may lead to permanent kidney damage.

Escherichia coli is the most common cause of urinary- tract infection; Staphylococcus saprophyticus is also com- mon in sexually active young women. Less common causes include Proteus and Klebsiella spp. Pseudomonas aeruginosa infections usually occur in the hospital set- ting and may be associated with functional or anatomi- cal abnormalities of the renal tract. Staphylococcus epi- dermidis and Enterococcus faecalis infection may complicate catheterisation or instrumentation.

Whenever possible a specimen of urine should be collected for culture and sensitivity testing before starting antibacterial therapy. The antibacterial cho- sen should reflect current local bacterial sensitivity to antibacterials.

Uncomplicated lower urinary-tract infections often respond to trimethoprim, nitrofurantoin, amoxicillin, or nalidixic acid given for 7 days (3 days may be adequate for infections in women); those caused by fully sensitive bacteria respond to two 3-g doses of amoxicillin (section 5.1.1.3). Widespread bacterial resistance, especially to ampicillin, amoxicillin, and trimethoprim has increased the importance of urine culture before therapy. Alter- natives for resistant organisms include co-amoxiclav (amoxicillin with clavulanic acid), an oral cephalosporin, pivmecillinam, or a quinolone.

Long-term low dose therapy may be required in selected patients to prevent recurrence of infection; indi- cations include frequent relapses and significant kidney damage. Trimethoprim, nitrofurantoin and cefalexin have been recommended for long-term therapy.

Methenamine (hexamine) should not generally be used because it requires an acidic urine for its antimicrobial activity and it is ineffective for upper urinary-tract infec- tions; it may, however, have a role in the prophylaxis and treatment of chronic or recurrent uncomplicated lower urinary-tract infections and asymptomatic bacteruria.

Acute pyelonephritis can lead to septicaemia and is treated initially by injection of a broad-spectrum anti- bacterial such as cefuroxime or a quinolone if the patient is severely ill; gentamicin can also be used.

Prostatitis can be difficult to cure and requires treatment for several weeks with an antibacterial which penetrates prostatic tissue such as trimethoprim, or some quino- lones.

Where infection is localised and associated with an indwelling catheter a bladder instillation is often effective (section 7.4.4).

Urinary-tract infection in pregnancy may be asympto- matic and requires prompt treatment to prevent pro- gression to acute pyelonephritis. Penicillins and ceph- alosporins are suitable for treating urinary-tract infection during pregnancy. Nitrofurantoin may also be used but it should be avoided at term. Sulphonamides, quinolones, and tetracyclines should be avoided during pregnancy; trimethoprim should also preferably be avoided particularly in the first trimester.

In renal failure antibacterials normally excreted by the kidney accumulate with resultant toxicity unless the dose is reduced. This applies especially to the amino- glycosides which should be used with great caution; tetracyclines, methenamine, and nitrofurantoin should

be avoided altogether. Children Urinary-tract infections in children require

prompt antibacterial treatment to minimise the risk of renal scarring. Uncomplicated ‘lower’ urinary-tract infections in children over 3 months of age can be treated with trimethoprim, nitrofurantoin, a first generation cephalosporin (e.g. cefalexin), or amoxicillin for 3 days; children should be reassessed if they continue to

be unwell 24–48 hours after the initial assessment. Amoxicillin should only be used if the organism causing the infection is sensitive to it.

Acute pyelonephritis in children over 3 months of age can be treated with a first generation cephalosporin or co-amoxiclav for 7–10 days. If the patient is severely ill, then the infection is best treated initially by injection of a broad-spectrum antibacterial such as cefotaxime or co- amoxiclav; gentamicin is an alternative.

Children under 3 months of age should be transferred to hospital and treated initially with intravenous anti- bacterial drugs such as ampicillin with gentamicin, or cefotaxime alone, until the infection responds; full doses of oral antibacterials are then given for a further period.

Recurrent episodes of infection are an indication for imaging tests. Antibacterial prophylaxis with low doses of trimethoprim or nitrofurantoin may be considered for children with recurrent infection, significant urinary- tract anomalies, or significant kidney damage.