P73
MODIFICATION OF DIET IN RENAL STONE DISEASE: REVIEW OF THE
EVIDENCE AND SERVICE PROVIDED AT THE ROYAL FREE CENTRE FOR
NEPHROLOGY
Newman, J¹, Moochhala, S²
¹Department of Nutrition and Dietetics, ²UCL Centre for Nephrology, Royal Free London
NHS Foundation Trust
INTRODUCTION: Kidney stone disease is a relatively common condition with an estimated
prevalence of five per cent in the general population with men being twice as likely as women
to develop kidney stones. Historically in this Trust, dietetic referrals for kidney stone patients
were ad hoc and advice primarily focused on increasing fluid intake and reducing salt intake.
Following an increased number of referrals since December 2011, the current service provision
was reviewed. It became apparent that our patient literature on kidney stones was out-of-date
and often inconsistent with that provided by other health care professionals in the Metabolic
Stone Clinic. The aim of this project was to review the current evidence base for dietary
intervention, the level of input required for patients with recurrent stone disease and the
expected outcome after appropriate dietary advice.
METHODS: A literature search was carried out using the following sources: NHS Evidence,
Cochrane Library, Medline, Embase, Cinahl, Amed using the terms below:
Patient/Population/Problem
Intervention
Comparison
Outcome
Kidney stones
Diet therapy
None
Reduction
Kidney calculi
Nutrition Therapy
Metabolic stones
Nephrolithiasis
We contacted 5 renal units to ascertain what dietary advice/ service they were providing for
patients with stones. We also looked at the number of referrals to the dietitian in our renal team
for renal stone related advice between January 2011 to May 2012,
RESULTS: Limited number of clinical trials have been conducted which evaluate the effects of
various dietary treatment regimens in individuals with a history of kidney stones. Many of the
recommendations are based on clinical studies of urinary measures in healthy subjects or large
population studies, which correlate food intake by questionnaire to kidney stone development.
Our audit of referrals in the Trust showed out of the 5 patients identified, the primary stone type
was calcium oxalate in 2 patients, uric acid in 2 patients and unconfirmed in the remaining
patient. The dietary advice provided was consistent with these current recommendations, which
includes increasing fluid intake, reducing BMI (if clinically indicated) and reducing salt.
Oxalate restriction is not always necessary (e.g. in the case of confirmed non-oxalate stones),
and the degree of restriction is unclear as oxalate absorption varies with other dietary
components and enteric factors. No clear or consistent guidance on the level and frequency of
dietetic input required for stone patients was identified in the literature. The key clinical
outcomes that should be measured as response to dietary intervention remain unclear.
CONCLUSION: This descriptive project has shown that the dietary advice recommendations
for kidney stone patients have not changed significantly since our last review period 6 years
ago. Research has suggested some additional advice such as drawing attention to foods and
fluids which may positively influence the pH, highlighting the need for regular review. In view
of the current evidence, no specific additional clinical dietetic advice is indicated for our
recurrent calcium-stone forming patients. Initial management is via a dietary information leaflet
consistent with the published literature. Resources are best concentrated on those requiring
specialist dietetic input e.g. uric acid stones, where there is a confirmed biochemical
abnormality despite ‘optimised’ medical management with persisting stone recurrence. These
patients are identified and managed in collaboration with the Metabolic Stone Clinic in the
Trust. Even in this group, further evidence is needed to define appropriate clinical outcomes.