Principles of Management
The clinical implications of sterile pyuria are unclear and there are currently no clear national or local guidelines. A local consensus article suggests the following approach:
Definition- ‘Urine dipstick positive for leucocytes(1+ or greater) in the absence of dipstick haematuria or nitrites with subsequent MSU showing no bacterial growth.’
If asymptomatic then repeat after 2-4 weeks and then consider further investigations or referral if still positive. If second test is negative then a further repeat 2-4 weeks later is suggested. 2 out of 3 positive tests would also warrant further investigation.
If a patient is asymptomatic and partially treated UTI or chlamydia is suspected then test and treat appropriately. Other infectious causes include urethritis, prostatitis, balanitis and vulvo-vaginitis would usually be associated with other symptoms and treated accordingly.
TB and schistosomiasis are common causes of pyuria globally but rare in UK without other risk factors. Testing should be reserved for those in at risk populations.
Non- urological infections may also be associated with sterile pyuria (e.g pneumonia, appendicitis).
Post-menopausal atrophy. If symptomatic atrophic vaginitis then treat with topical oestrogen.
Pregnancy. Usually due to physiological vaginal discharge. UTI or asymptomatic bacteria must be excluded due to risk of miscarriage/pre-term labour.
Renal disease. Sterile pyuria can be associated. A check of eGFR, urine ACR and BP should be undertaken to exclude renal disease.
Ketamine use. Usually presents with severe pain, frequency, haematuria and dysuria but may occasionally present with sterile pyuria.
Bladder cancer in an infectious cause and will usually be associated with haematuria or other new onset urinary symptoms ( urgency/frequency/noturia/dysuria/bladder pain). In this case 2 week wait referral should be considered particularly in patients> 50 years old.
Investigations in Primary Care
Investigations should be directed by symptoms but the following should be considered:
NAAT test ( if patient sexually active)
USS of kidneys
Urine culture for AAFB (if at risk of TB)
Urine microscopy for schistosomiasis ova (if recent travel to at risk areas of Africa or Middle East e.g. Lake Malawi)
If sterile pyuria is symptomatic then a referral to urology should be made and if red flags or> 50 then consider 2 week wait referral.
In patients with persistent asymptomatic unexplained sterile pyuria then the need for referral is less clear. The GP should discuss the option of referral with their patient and refer if ongoing concern and the patient is willing to have further in hospital tests