UTIs occur when there is bacterial colonisation of the uroepithelium and a subsequent inflammatory response. Classically, the urine and urinary collecting system is sterile, although there is some debate whether a small amount of bacterial colonisation is normal. Given this, and that voiding urinary samples may be contaminated by skin or rectal reservoir flora, bacteriuria is suggestive of a UTI, but bacteriuria and pyuria (white blood cells in the urine) is much more specific for infection.
Uncomplicated vs. complicated UTI
- uncomplicated: an otherwise healthy patient with a structurally and functionally normal urinary tract
complicated: factors are present that decrease the likelihood of therapy being effective
- urinary tract is structurally or functionally abnormal
- immunocompromised status
- especially virulent pathogen
- factors that may make a patient complicated 1
- childhood UTIs
- failed antibiotic course
- extended symptoms before presentation
Treatment and prognosis
These patients are usually well managed with a course of oral antibiotics.
Many imaging algorithms suggest that imaging for an uncomplicated cystitis or pyelonephritis is unnecessary.
These patients have often failed a course of antibiotics and may benefit from imaging:
- lower urinary tract
- CT urography: for evaluation of structural abnormalities and possible abscess formation; MRI could be considered if the patient has an allergy to contrast
- ultrasound has a secondary role
- upper urinary tract
- CT abdomen with contrast (or without and with contrast)
- MRI abdomen: for patients with contrast allergies and pregnant patients
- renal and bladder ultrasound: second line, relative to CT it is not as good at detecting renal parenchymal changes and/or characterizing perinephric extension of infection
- 1. Wein AJ, Kavoussi LR, Novick AC et-al. Campbell-Walsh Urology: Expert Consult Premium Edition: Enhanced Online Features and Print, 4-Volume Set. Saunders. ISBN:1416069119. Read it at Google Books - Find it at Amazon
- 2. Segal AJ, Amis ES, Bigongiari LR et-al. Recurrent lower urinary tract infections in women. American College of Radiology. ACR Appropriateness Criteria. Radiology. 2000;215 Suppl: 671-6. Pubmed citation Updated 2014, electronic pdf accessed Oct 24, 2015.
- 3. Sandler CM, Amis ES, Bigongiari LR et-al. Imaging in acute pyelonephritis. American College of Radiology. ACR Appropriateness Criteria. Radiology. 2000;215 Suppl: 677-81. Pubmed citation Updated 2012, electronic pdf accessed Oct 24, 2015.