Typical Urinalysis Findings in Leptospirosis
Urinalysis in leptospirosis typically shows proteinuria and hematuria 1.
Primary Urinalysis Abnormalities
The most consistent urinalysis findings in leptospirosis include:
- Proteinuria - Present due to renal tubular damage and interstitial nephritis
- Hematuria - Results from capillary fragility and direct renal injury
These findings reflect the underlying pathophysiology of leptospirosis, where interstitial nephritis is the basic renal lesion and occurs even in patients without overt clinical renal manifestations 1.
Additional Urinary Findings
Beyond the classic proteinuria and hematuria, leptospirosis can present with:
- Hyposthenuria (dilute urine) - May occur due to tubular dysfunction and acquired nephrogenic diabetes insipidus, particularly in the early stages
- Mild urinary sediment changes - Non-specific cellular elements may be present
- Low molecular weight proteinuria - Research demonstrates a 36.7% increase in low molecular weight protein excretion, supporting the interstitial nephritis pattern 2
Clinical Context and Pitfalls
Important caveat: These urinalysis findings are non-specific and must be interpreted alongside the clinical presentation (fever, myalgia, conjunctival suffusion, history of water/animal exposure) and other laboratory abnormalities 1.
The renal involvement in leptospirosis is characterized by:
- Tubular dysfunction preceding glomerular filtration rate decline - This explains why hypokalemia is common (elevated urinary fractional excretion of potassium) 3, 4
- Polyuric rather than oliguric presentation in many cases - Unlike typical acute kidney injury 5, 4
Critical pitfall: Despite the presence of proteinuria and hematuria, urine is not a suitable sample for isolation of leptospira for culture purposes 1. However, recent evidence suggests urine PCR testing can be highly sensitive (84%) for early diagnosis, particularly from day 4 onward after symptom onset 6.