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This article is part of the supplement: 7th European Workshop on Immune-Mediated Inflammatory Diseases

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Distal renal tubular acidosis in primary Sjögren syndrome

Tim Both1*, Ewout J Hoorn1, Zana Brkic2, Marjan A Versnel2, Jan AM van Laar1, P Martin van Hagen1, Robert Zietse1 and Paul LA van Daele1

  • * Corresponding author: Tim Both

Author Affiliations

1 Dept. of Internal Medicine, Erasmus MC, Rotterdam, The Netherlands

2 Dept. of Immunology, Erasmus MC, Rotterdam, The Netherlands

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Journal of Translational Medicine 2012, 10(Suppl 3):P8  doi:10.1186/1479-5876-10-S3-P8

The electronic version of this article is the complete one and can be found online at:

Published:28 November 2012

© 2012 Both et al; licensee BioMed Central Ltd.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Primary Sjögren syndrome (pSS) is a chronic inflammatory disorder characterized by lymphocytic infiltration of exocrine glands. pSS can also cause distal renal tubular acidosis (dRTA). dRTA is a disorder in which patients are unable to acidify their urine because of impaired hydrogen ion secretion in the collecting duct.


To determine the prevalence of dRTA in pSS using a urinary acidification test.

Patients and methods

62 pSS patients and 27 healthy controls participated in the study. After baseline measurements, both groups received a single administration of 40 mg furosemide and 1 mg fludrocortisone after which urine pH was measured hourly for six hours (Walsh et al., Kidney Int 2007). dRTA was initially defined as a failure to achieve a urine pH < 5.3.


At baseline, pSS patients had a significantly higher urine pH (6.2 ± 0.6 vs. 5.8 ± 0.7) and lower estimated ammonium secretion (10 ± 14 vs. 25 ± 23 mmol/l) than controls (p < 0.01 for both), already suggesting a subtle acidification defect in pSS. Only 4 pSS patients, however, had overt metabolic acidosis (serum bicarbonate < 21 mmol/l). During the test, 24 pSS patients (39%) failed to acidify their urine to a pH < 5.3.

Seven controls (26%), however, were also unable to reach a urine pH < 5.3 (p = 0.3). Therefore, we believe a urine pH of 5.3 may not be sufficiently specific for diagnosing dRTA in pSS. All controls did reach a urine pH of 5.8 or lower during the test. Setting the threshold at this level, 7 patients with pSS (11%) were diagnosed with dRTA.


The prevalence of dRTA in pSS is relatively high. A urinary acidification test is more sensitive to diagnose dRTA in pSS than serum bicarbonate, but the threshold for a positive test should be set at a urine pH of 5.8 instead of 5.3.