Presented by: Amy Gosling
School of Medicine, Worsley Building, University of Leeds

Introduction

Cystinuria is an autosomal recessive condition resulting in the supersaturation of cystine in the urine and subsequent crystallisation. Despite only accounting for 2% of all urolithiasis, the 5-year recurrence rate for cystine stones is high at approximately 83%. The current understanding of the growth mechanisms of urinary stones is limited. Characterisation of urinary stones is essential to improve understanding of the formation of urolithiasis, allowing for the identification of major and trace components and morphological features and structure. The existing standard analysis technique is Fourier-transform infrared spectroscopy (FT-IR), however, a wider range of characterisation techniques is advisable for a thorough understanding of stone composition and growth. These results will be used to suggest a protocol for stone analysis.

Materials

Three intact stones were removed from an 80-year-old male, undergoing treatment for prostate cancer. The stones were removed by an open cystolithotomy because of the size. There was no positive family history of cystinuria. The three ovoid stones (two ~6 cm, one ~3 cm in length) were superficially similar. One stone was cut in half to reveal the internal structure. The surface of the stone was imaged using stereo and reflected light microscopy. Higher-resolution imaging and elemental information were performed using scanning electron microscopy (SEM). Crystalline phases were identified by X-ray diffraction (XRD). Results were compared with FT-IR spectra. A 30-micrometre thin section of the smaller stone was produced to enable polarised transmitted light microscopy.

 

Results

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Light microscopy visualised a central core of large crystals surrounded by concentric growth rings emanating from the centre of the stone (Fig.). XRD revealed a single, crystalline phase, cystine. SEM imaging and elemental analysis (EDX) showed hexagonal crystals (cystine) together with amorphous, spherical calcium phosphate particles (~5 µm) clustered near the core and in concentric rings within the stone. FT-IR spectra were consistent with cystine and calcium phosphate.

Conclusion

We have demonstrated that a wide range of characterisation techniques is necessary to clearly understand the structure and composition of cystine stones. Protocols for the analysis of urinary tract stones should combine multiple methods of characterisation to aid in the understanding of stone formation.

 

Funding

Nil

Lead Authors

Roanne Causey,
School of Medicine, Worsley Building, University of Leeds

Chandra Shekhar Biyani,
Urology Department, St James’s University Hospital

Robert Simpson,
School of Chemical and Process Engineering, University of Leeds

Ben Holley,
School of Chemical and Process Engineering, University of Leeds

Antonia Borissova,
School of Chemical and Process Engineering, University of Leeds

Andrew Scott,
School of Chemical and Process Engineering, University of Leeds