Synopsis
Use dipstick, quantitative protein testing, culture and urine sediment together to localise renal and urinary disease while recognising contamination, false results and time-critical nephritic patterns.
- A fresh midstream clean-catch sample with documented timing and symptoms is the starting point. Catheter, menstruation, vigorous exercise, antiseptic contamination and delayed analysis can change results.
- Dipstick 'blood' detects haem pigment, not intact red cells. Haematuria, haemoglobinuria and myoglobinuria can all be positive; microscopy and the clinical setting separate them.
- Nitrite supports nitrate-reducing bacteria but is insensitive with frequent voiding, low dietary nitrate or organisms that do not reduce nitrate. A negative result never excludes UTI or pyelonephritis.
Key red flags
Protein with dysmorphic erythrocytes or red-cell casts, hypertension, oedema and impaired function favours glomerular inflammation. Systemic rash, haemoptysis or rapidly rising creatinine increases urgency.
Investigation priorities
Screen blood, leucocytes, nitrite, protein, glucose, ketones, pH and concentration at the bedside or laboratory.
Management branches
Blood and protein with impaired function, hypertension, casts or systemic inflammatory features.
- Repeat a clean sample, quantify ACR/PCR, obtain urgent renal biochemistry, FBC and blood pressure, and review baseline and urine output.
- Discuss promptly with nephrology; send targeted complements, ANCA, ANA, anti-GBM, infection and paraprotein testing as advised rather than delaying referral for a complete panel.
Key medicines
Empirical antimicrobial for urinary infectionSelect agent, dose and duration from current local and NICE guidance using site, severity, culture history, allergy, pregnancy and renal function.
SGLT2 inhibitor awarenessContinue or pause only according to an individualised clinical sick-day and peri-procedure plan; timing varies by medicine, illness severity and procedure.