Urinary tract infections

URINARY TRACT INFECTIONS

Introduction

Infections of the kidney, ureter and bladder constitute urinary tract infections (UTI). When infections occur in the kidney and ureter it is called upper urinary tract infections and bladder downwards it is called lower urinary tract infections.

Structure Of Urinary Tract (Fig:16)

       Urinary tract infection is common in females than in males. The urethra in females are shorter and wider and is less effective in preventing the bacteria entering the bladder. Sexual intercourse is a predisposing factor. High incidence is seen in pregnant women because of hormonal changes and impairment of urine flow due to pressure on the urinary tract. Other causes of urinary stagnation predispose UTI, such as urethral obstruction, urinary stones, congenital malformation and neurological disorders. Most UTI are caused by organisms origi-nating from the patient’s own fecal flora.

Organisms Causing Urinary Tract Infections

For convenience the organisms causing urinary tract infections can be classified into the following:

1.      Organisms most commonly involved are: Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis and other Proteus spp, Enterococcus faecalis, Pseudomonas aeruginosa, Staphylococcus saprophyticus and S.aureus

2.      Uncommon organisms are: Enterobacter species, Serratia spp, Providencia spp, other nonfermenters

3.      Rare organisms are: Streptococci other than group A, Candida albicans, Candida glabrata etc

Laboratory Diagnosis Of Urinary Tract Infection

Mid stream urine is collected and transported to the laboratory immediately. If there is any delay expected it should be refrigerated. A quantitative culture should be performed to know the number of gram negative organisms present. A count of more than 100,000 (105 /ml) organisms per ml of urine in pure culture is indicative of UTI. For the isolated organisms antibiotic susceptibility testing must be done and appropriate treatment should be given