Renal stone analysis: why and how?

Upper urinary tract stone disease is widespread in the developed world. On both clinical and economic grounds it is now accepted that evidence-based medical intervention is the only approach likely to make a significant impact on the incidence, and more importantly, the recurrence rates of this disease. Targeted medical prophylaxis requires reliable information on stone type which, when combined with relevant blood and urine analyses, allows identification of treatable risk factors. Data from an external quality assurance scheme indicate that stone analysis is poorly performed in many laboratories, and it is probable that this results in ill-informed patterns of investigation, inappropriate therapy, missed diagnoses of rarer causative disorders and wasteful further investigation of 'non-renal' stone artefacts. Renal stone analysis is a specialist investigation requiring appropriate analytical and interpretative expertise if the information is to be used to enhance patient care. For those laboratories not able to offer this, for whatever reason, referral is the only defensible approach to service provision. The methods currently employed in many departments have no place in modern clinical biochemistry practice.

Rapid computer-assisted infrared analysis of urinary calculi using photoacoustic detection.

The application of commercial spectrum-analysing software to quantitative analysis of urinary stones by Fourier transform infrared spectrophotometry is described. The infrared technique is straightforward in comparison with other stone analysis procedures of similar scope and affords significant time savings. The use of partial least squares regression in the analysis program enables better quantitation of stone components than has been hitherto possible using infrared methods. All the principal and many less common stone constituents can be detected and measured. Photoacoustic detection was employed, thus enabling non-destructive analysis with minimal sample preparation. A comparison is made between the infrared procedure and the hybrid thermogravimetric plus "wet" chemistry technique, which it has superseded for routine urinary stone analysis in the author's department.

Stability of catecholamines in whole blood, plasma, and platelets.

Checking catecholamine stability in whole blood, plasma, and platelets, we found that specimens stored at room temperature or frozen for periods ranging from 1.5 h to three weeks show no significant difference in measured catecholamine concentration. The implications of these findings are discussed.