Presented by: Mario Basulto-Martinez MD, MSc
Division of Urology, Schulich School of Medicine & Dentistry, Western University,

Introduction

Distal tubular renal acidosis (dTRA) is characterized by the distal nephron’s inability to acidify urine and is associated with calcium phosphate (CaP) urinary stones, nephrocalcinosis and bone disease. However, in the incomplete form of dTRA (idTRA), the biochemical traits are often less conspicuous, unrelated to systemic acidosis, and usually underrecognized. Therefore, this study aimed to evaluate stone-formers (SF) with features of idTRA to identify the prevalence and better characterize their clinical features compared to SFs without dTRA/idTRA.

Materials

A prospectively collected metabolic stone clinic database was reviewed. Patients with incomplete data or incorrectly collected 24-h urine studies were excluded. SF with urinary pH ≥ 6, hypocitraturia (<1.6 mmol/d), and serum potassium <3.8 mmol/L were considered as suggestive for idTRA and compared to SF without evidence of dTRA[JB1] . 

Results

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A total of 1170 SF were included, and 5.2% had suggestive features of idTRA. Sex was similar between groups (p=0.428); however, median age (p=0.003) and body mass index (BMI, p=0.032) were significantly lower in patients with idTRA. Stone composition was available in 682 SF, of which 12% had predominantly CaP stones, but no association between CaP and idTRA was observed (p=574). Moreover, idTRA was associated with lower vitamin D (p=0.023), urinary phosphate (p=0.001) and calcium (p=0.02). Furthermore, 6.6% of patients with idTRA had nephrocalcinosis and 7 subjects (11.5%) had bone mineral densitometry performed with 4 (57%) showing below normal bone mass. 

Conclusion

idTRA is an underdiagnosed risk factor for urinary stone disease and may be found in up to 5% of stone-formers. Patients with idRTA may present at a younger age, with lower BMI, low vitamin D levels and lower urinary calcium compared to SF without features of idTRA. Recognition of idTRA is essential to providing optimized care for SF.

Funding

None

Lead Authors

Fernanda Gabringa-Berto, MD, MSc
Division of Urology, Schulich School of Medicine & Dentistry, Western University

Co-Authors

Nabil Sultan, MD
Division of Nephrology. Schulich School of Medicine & Dentistry. Western University

Elie Gharib, MD
Division of Nephrology. Schulich School of Medicine & Dentistry. Western University

Eduardo Gonzalez-Cuenca, MD, MSc
Division of Urology, Schulich School of Medicine & Dentistry. Western University

Hassan Razvi, MD
Division of Urology, Schulich School of Medicine & Dentistry. Western University

Jennifer Bjazevic, MD, MSc
Division of Urology, Schulich School of Medicine & Dentistry. Western University