Clinical audit of kidney stone formers in Southern Tasmania

Aim:

To investigate the number, type, and metabolic profile of recurrent kidney stone formers (KSF) referred to a tertiary hospital renal unit.

Background:

Up to 15% of adults are affected by kidney stones at some point during their life. For people who have their first stone, up to half will experience a second. Complete metabolic assessment of KSF in the Tasmanian population might allow more effective preventative strategies to be put in place.

Methods:

This retrospective clinical audit reviewed adult KSF referred to the Royal Hobart Hospital renal unit between 2009 and 2019.

Results:

We only identified 39 adults (18 (46%) women) mean age 52 ± 16.9 years. Overall, 85% of these patients had a previous admission for kidney stones. All patients had pre-existing comorbidities, including hypertension (62%), diabetes (36%) and 46% had a smoking history. Of those with a known BMI, 95% were overweight or obese. On stone analysis, 21% were calcium oxalate, 13% were staghorn, 8% were urate, 5% were cysteine and the rest (51%) were not recorded. Biochemically, 18% had low serum bicarbonate, 68% had low eGFR, 5% had hypercalcaemia, 14% hyperphosphatemia, 9% had hypophosphatemia, 25% had hyperuricemia and 18% had hypomagnesaemia. Sixteen of 39 (40%) patients had a 24-hour urine assessment where most (56%) had <2 L urine volume. Of those tested, 40% had hyperoxaluria (2 of 5), 33% had hypocitraturia (2 of 6) and none had hypercalciuria (0 of 6).

Conclusion:

This audit shows stone analysis is underperformed, referral to renal physicians uncommon and there is inconsistent metabolic assessment. A consistent management approach could possibly help improve preventative strategies and reduce future episodes of renal colic or hospital admissions.