Fever and proximal tubular function in acute pyelonephritis

Area of Science:

• Nephrology
• Infectious Diseases
• Biochemistry

Background:

• Urinary tract infections (UTI) can affect different parts of the urinary system, leading to varying degrees of kidney involvement.
• Proximal tubular dysfunction can be assessed using specific urinary biomarkers.
• Distinguishing between renal and non-renal causes of elevated urinary markers is crucial for accurate diagnosis.

Purpose of the Study:

• To evaluate urinary excretion of alpha 1-microglobulin (alpha 1M), beta 2-microglobulin (beta 2M), retinol-binding protein (RBP), and N-acetyl-beta-D-glucosaminidase (NAG) in various UTI forms and non-renal fever.
• To determine the utility of urinary protein profiles and fibrin degradation product D (FDP-D) in diagnosing acute UTI.
• To investigate the role of fever as a cause of tubular proteinuria.

Main Methods:

• Measurement of urinary alpha 1M, beta 2M, RBP, and NAG in patients with acute pyelonephritis, acute cystitis, asymptomatic bacteriuria, and non-renal fever.
• Detection of urinary fibrin degradation product D (FDP-D) in UTI patients.
• Correlation analysis of urinary protein excretion and comparison with body temperature.

Main Results:

• Significantly increased urinary concentrations of alpha 1M, beta 2M, RBP, and NAG were observed in acute pyelonephritis compared to acute cystitis and asymptomatic bacteriuria.
• Tubular proteinuria and enzymuria were also present in subjects with non-renal fever, similar to pyelonephritis findings.
• Urinary alpha 1M, beta 2M, and RBP levels were highly correlated; NAG activity showed weaker correlation. FDP-D detection had limited diagnostic value for UTI level.

Conclusions:

• Fever itself is the likely cause of tubular proteinuria observed in acute pyelonephritis.
• Urinary protein profiles offer no advantage over body temperature measurement for localizing acute UTI.
• Fibrin degradation product D is not a reliable marker for diagnosing the level of UTI.