Urine and stone analysis for the investigation of the renal stone former: a consensus conference

Abstract

The Consensus Group deliberated on a number of questions concerning urine and stone analysis over a period of months, and then met to develop consensus. The Group concluded that analyses of urine and stones should be routine in the diagnosis and treatment of urinary stone diseases. At present, the 24-h urine is the most useful type of urine collection, and accepted methods for analysis are described. Patient education is also important for obtaining a proper urine sample. Graphical methods for reporting urine analysis results can be helpful both for the physician and for educating the patient as to proper dietary changes that could be beneficial. Proper analysis of stones is also essential for diagnosis and management of patients. The Consensus Group also agreed that research has shown that evaluation of urinary crystals could be very valuable, but the Group also recognizes that existing methods for assessment of crystalluria do not allow this to be part of stone treatment in many places.

Keywords: Crystalluria; Nephrolithiasis; Stone analysis; Urine analysis.

Fig. 1

Examples of urine analysis reports that include graphical features to aid in interpretation. a Part of the LithoLink report (Laboratory Corporation of America, Burlington, NC, USA) for 24-h urine results. Note that measures that are out of the normal range are highlighted both by a change in background colour and an increase in the size and boldness of the typeface. The history of the patient is also shown, with the most recent results on the top line. Note that in this case, the patient has significantly increased the urine volume, and thereby reduced the supersaturation value for calcium oxalate (SS CaOx). However, this was done along with a dramatic increase in dietary salt (Na 24), which likely led to the increase in urine calcium (Ca 24), which was part of what drove an increase in the supersaturation value for calcium phosphate (SS CaP). b Part of the graphical report for urine results from the LITHOSCREEN system for assessing stone patients [29]. Note that targeted values (least likely to lead to a stone recurrence) are at the centre of the diagram, in the green bull’s eye. PSF indicates the Robertson biochemical risk of forming stones as described above under Q12. The initial untreated PSF values for the patient are shown in the purple lines and shape, and the values after treatment are shown in light blue. Before treatment, this patient was at risk of forming both uric acid and calcium oxalate stones or a mixture of the two. Following suitable dietary treatment, the PSF values of the patient all fell into the green bull’s eye. Similar target diagrams are also available for both 24-h urine and dietary composition [29]