Investigations
1st investigations to order
urine dipstick
Test
Perform a urine dipstick test as the first diagnostic test in women aged under 65 years with urinary tract symptoms where they have:[4]
Only 1 of the 3 key signs or symptoms (dysuria, nocturia, or cloudy-looking urine, OR
None of the 3 key signs or symptoms but other severe symptoms of urgency, frequency, visible haematuria, or suprapubic tenderness).
Use in combination with other tests.[4]
This test looks for positive leukocytes or nitrites to indicate a UTI.
Organisms like Escherichia coli or Klebsiella, Enterobacter, Proteus, Staphylococcus, or Pseudomonas species reduce nitrate to nitrite in the urine - therefore nitrites on a urinalysis is an indicator of a UTI.[56]
The presence of pyuria on its own is non-specific and does not always indicate clinical UTI.
Do not routinely perform a urine dipstick in:
Patients aged under 65 years with 2 or 3 of the key diagnostic symptoms (dysuria, nocturia, or cloudy-looking urine)[4][2]
Perform a urine culture instead if there is a risk of antibiotic resistance (see below).
Patients aged over 65 years[4][2]
Up to half of older adults, and most with a urinary catheter, will have bacteria present with no infection.[35]
This is asymptomatic bacteriuria and is not harmful.[4]
Antibiotics do not help with this and can cause harm.[4]
Consider a urine dipstick in patients aged over 65 years as a supplement to the urine culture and to detect red blood cells.
Patients with a catheter
Symptomatic UTI cannot be differentiated from asymptomatic bacteriuria on the basis of urine analysis by dipstick tests or by microscopy. Pyuria is common in catheterised patients and its level has no predictive value.[2]
Note that the Scottish Intercollegiate Guidelines Network differs from NICE in its advice and recommends that a dipstick test should be performed in women under 65 who have 2 or more of the following urinary symptoms: dysuria, frequency, urgency, visible haematuria, nocturia.[2]
Result
positive for nitrite and leukocytes
if dipstick result is negative but the symptoms suggest a UTI, the probability of disease is still relatively high[49]
urine culture and sensitivity
Test
Send a midstream, clean-catch urine specimen for culture (before giving antibiotics) if the patient:
Has 2 or 3 of the 3 key diagnostic symptoms (dysuria, new nocturia, or cloudy-looking urine) if there is a risk of antibiotic resistance[3]
Has 1 of the 3 key diagnostic symptoms, and the urine has positive nitrites or positive leukocytes and red cells, and there is a risk of antibiotic resistance[3]
Has none of the 3 key diagnostic symptoms but has other urinary symptoms, and the urine has positive nitrites or positive leukocytes and red cells, and there is a risk of antibiotic resistance[3]
Has 1 of the 3 key diagnostic symptoms, and the urine has positive leukocytes and negative nitrites[4]
Has none of the 3 key diagnostic symptoms but has other urinary symptoms, and the urine has positive leukocytes and negative nitrites[4]
Is pregnant[4]
Is aged over 65 years and is symptomatic and is being started on antibiotics for a UTI[1][4]
Has suspected sepsis or pyelonephritis[4]
Has persistent symptoms or where antibiotic treatment has failed[4]
Has recurrent UTIs (2 in 6 months or 3 in 12 months)[4]
Has a urinary catheter and will receive antibiotics for a UTI[4][52]
Has a risk of antimicrobial resistance (genitourinary abnormalities, renal impairment, lives in a care home, previous UTI resistance, long recent hospital stay, recent travel to a place with antibiotic resistance).[4]
This is the most specific and sensitive test.
Women catching midstream urine samples can try to part the labia if possible to help reduce contamination.[35]
Recommend against cleaning the area with antiseptic as this can inhibit bacteria.[4]
Catch a sample in a sterile container in elderly patients with incontinence.[51]
Consider sending a repeat sample if mixed growth or epithelial cells are present in a symptomatic patient.[4][35]
Send a urine sample for culture, ideally before giving antibiotics, in catheterised patients who present with fever.[57][2]
Take the sample from the catheter, via a sampling port if provided, using an aseptic technique.[57]
If the catheter has been changed, obtain the sample from the new catheter.[57]
If the catheter has been removed, obtain a midstream sample of urine.[57]
Note for the lab that you suspect catheter-associated infection and any antibiotic prescribed.[57]
Result
107 to 108 CFU/L (104 to 105 CFU/mL) indicate UTI
Investigations to consider
urine microscopy
Test
Do not use as a routine diagnostic test. It may be used to confirm the type of organism and to guide antibiotic selection in complicated UTI or pyelonephritis.
Do not use urine microscopy to diagnose UTI in patients with catheters.[2]
Symptomatic UTI cannot be differentiated from asymptomatic bacteriuria on the basis of urine analysis by microscopy.
Result
bacteria, white blood cells, possibly red blood cells
post-void residual
Test
Consider in women with recurrent UTIs or in unwell women with suspected UTI.
Poor bladder emptying may be a cause and UTIs may continue to occur until this is resolved.
Result
may demonstrate residual urine after bladder emptying
renal ultrasound
Test
Use ultrasound to rule out urinary tract obstruction in women with uncomplicated pyelonephritis and a history of urolithiasis, renal function disturbances, or a high urine pH.[1]
Use ultrasound in preference to CT or excretory urography in pregnant women who remain febrile after 72 hours of treatment to avoid radiation risk to the fetus.[1]
Result
kidney stone; hydronephrosis; renal abscess; renal scarring
abdominal/pelvic CT
Test
In hospital, consider contrast-enhanced computed tomography (CT) in unwell patients, for example, if the patient remains febrile after 72 hours of treatment, or immediately in any patient with worsening clinical status.[1]
Consider non-contrast CT to identify stones, particularly if obstruction is identified on ultrasound scan.
Avoid in pregnant women to avoid radiation risk to the fetus.[1]
Result
kidney or bladder stone; renal abscess
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