Investigation and diagnosis:
- Urine microscopy - the presence of 10 leukocytes/mm3 of uncentrifuged urine or 10 leukocytes/hpf of the centrifuged sample, in a clinically suspected UTI, is important for diagnosis.
- Dipstick leukocyte esterase test – This is a rapid screening test for UTI; a negative test result does not rule out UTI.
- Urine culture –
- This is most useful when collected from a patient with clinical features of UTI, and should always be collected before the first dose of antibiotic.
- Usually, bacteriuria of 105cfu/ml is associated with UTI. However, any colony count is significant in symptomatic young women and men with pyuria. Any colony count of bacteria grown from a suprapubic aspirate is significant.
- The sample is to be collected in a sterile screw-capped container and up to a minimum volume of 10-20 ml.
- Midstream clean catch
- Supra-pubic aspiration especially in infants
- Aseptic single catheterization for sample collection
- Collection procedure in a catheterized patient: If the catheter is in place <14 days, urine must be collected using a syringe and needle (No. 26) from the Foley’s catheter after disinfecting the rubber surface with 70% ethyl alcohol. If the catheter is >14 days, replace the old catheter before collection of urine for culture.
- Urine samples should not be obtained from catheter bags.
- Storage & Transport: Transport of the specimen and plating should be done within 1 hour. If delay, the urine sample must be refrigerated at 4ºC for a maximum of 6-8 hours.
- Blood cultures (two sets) – Should be sent before the first dose of antibiotics if the patient is febrile, has suspected acute pyelonephritis or complicated UTI.
- Radiology – Radiology should only facilitate diagnosis of UTI
- Ultrasound of kidney, urinary tract and bladder is essential for all complicated and recurrent (more than 2 episodes) UTI.
- CECT of kidney and the urinary system is indicated when pyelonephritis, perinephric abscess or intra-renal abscess are suspected.