Metabolic assessment in pure struvite stones formers: is it necessary?

Abstract

Background and objective: Magnesium ammonium phosphate stones (MAP), also known as struvite stones, are associated with urinary infection and impairment of renal unit. The aim of this study is to evaluate the urinary metabolic risk factors for recurrence of renal calculi in patients submitted to nephrectomy due to MAP stones. Methods: We retrospectively reviewed the charts of patients > 18 years old submitted to total nephrectomy due to pure MAP stones and pure calcium oxalate (CaOx) stones from July 2006 to July 2016. Urinary metabolic parameters were assessed through 24-hour urine exams ≥ 3 months after nephrectomy. Urinary metabolic parameters and new event related to lithiasis were compared. Results: Twenty-eight and 39 patients were included in MAP and CaOx group, respectively. Abnormalities in 24-hour urine samples were similar between groups. Hypercalciuria occurred in 7.1 and 10.3% of patients in MAP and CaOx group, respectively (p = 0.66), whereas hypocitraturia was present in 65.2 and 59.0% of patients with MAP and CaOx group, respectively (p = 0.41). No significant difference in new events was found between MAP and CaOx groups (17.9 vs. 23.1%, respectively; p = 0.60). Conclusion: A 24-hour urine evaluation should be offered to patients submitted to nephrectomy due to pure MAP stones in order to detect metabolic risk, improve treatment, and prevent stone recurrence.

The necessary pathway for metabolic and crystallographic analysis of kidney stones: struvite may not differ from its counterparts

“…Although metabolic abnormalities in pure struvite stone formers indeed appear to be more common than previously reported, the profile of metabolic alterations differ among reports. Iqbal et al 1 , for instance, reported much higher rates of hypercalciuria (43%) and lower rates of hypocitraturia (14%) among pure struvite stone formers than the ones presented by Danilovic et al 4 . A possible reason could have been a sample with approximately a third of patients in stage 3 CKD in both groups (CaOx and MAP) by the latter.…”

“…We read with great interest the work of Danilovic et al 4 , who conducted a retrospective evaluation of the charts of patients submitted to unilateral total nephrectomy due to pure MAP (magnesium ammonium phosphate or struvite stones) or pure calcium oxalate (CaOx) stones, searching for urinary metabolic parameters predictive of new clinical events. Although this topic has been raised in recent years 1 , the lack of data in our population highlights the epidemiologic relevance of their study 4 .…”