Crystalluria in idiopathic recurrent calcium urolithiasis. Dependence on stone composition

Area of Science:

• Nephrology
• Urology
• Biochemistry

Background:

• Recurrent idiopathic calcium urolithiasis (RCU) is a common condition.
• Understanding the factors contributing to RCU is crucial for effective management.
• Previous studies have explored crystalluria, relative saturation products (RSPs), and inhibitors in RCU patients.

Purpose of the Study:

• To investigate the nature and degree of crystalluria in fasting and postprandial urine of RCU patients.
• To correlate crystalluria patterns with stone composition.
• To compare crystalluria with RSPs and urinary inhibitors in relation to patient sex.

Main Methods:

• Retrospective study of RCU patients with available stone analysis.
• Crystalluria assessment using filter technique and polarization microscopy.
• Evaluation of crystalluria score, RSPs, and low-molecular-weight inhibitors.

Main Results:

• Calcium oxalate crystals were absent in patients with pure calcium oxalate stones and sporadic in mixed stones.
• Amorphous calcium phosphate, urate-containing, and spherolytic phases were more frequent in mixed stones.
• RSPs and inhibitors differed between sexes, unlike crystalluria patterns.

Conclusions:

• Calcium oxalate crystalluria is not a diagnostic aid for RCU with pure calcium oxalate stones.
• The presence of the isotropic phase alongside mixed stones may characterize a significant RCU subgroup.
• Urinary chemistry, physicochemical data, and crystalluria suggest sex-specific pathogenesis in RCU.