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Article of the week: Calcium : citrate ratio may predict severe lithogenesis

Every week the Editor-in-Chief selects the Article of the Week from the current issue of BJUI. The abstract is reproduced below and you can click on the button to read the full article, which is freely available to all readers for at least 30 days from the time of this post.

In addition to the article itself, there is an accompanying editorial written by a prominent member of the urological community. This blog is intended to provoke comment and discussion and we invite you to use the comment tools at the bottom of each post to join the conversation.

Finally, the third post under the Article of the Week heading on the homepage will consist of additional material or media. This week we feature a video of Miguel Angel Arrabal-Polo discussing his paper.

If you only have time to read one article this week, it should be this one.

Importance of citrate and the calcium : citrate ratio in patients with calcium renal lithiasis and severe lithogenesis

Miguel Angel Arrabal-Polo*, Miguel Arrabal-Martin*,  Salvador Arias-Santiago**, Juan Garrido-Gomez, Antonio PoyatosAndujar§ and Armando Zuluaga-Gomez**

Department of Urology, San Cecilio University Hospital, **Department of Medicine, Baza Hospital, Department of  Medicine, University of Granada, and Departments of Traumatology and §Biochemistry, San Cecilio University Hospital, Granada, Spain

OBJECTIVE

• To analyse the importance of urinary citrate and the urinary calcium : citrate  ratio in patients with calcium renal lithiasis and severe lithogenesis compared with  a control group of patients without lithiasis.

MATERIAL AND METHODS

• A cross-sectional study of 115 patients in eastern Andalusia, Spain was conducted.

• The patients were divided into two groups: Group A: 56 patients aged 25 – 60 years without calcium renal lithiasis; Group B: 59 patients aged 25 – 60 years, presenting with calcium renal lithiasis and severe lithogenesis.

• The citrate levels and the calcium : citrate ratio in the patients’ urine and the relationship of these two factors to lithiasic activity were analysed and compared.

RESULTS

• In Group B, 32.2% of the patients presented with hypocitraturia, compared with 14.3% of the patients in Group A (P = 0.02).

• The urinary citrate levels were lower in Group B than in Group A (P = 0.001) and the calcium : citrate ratio was higher in Group B than in Group A (P = 0.005).

• The results suggest that a patient urinary calcium : citrate ratio > 0.25 indicates severe lithogenesis (with a sensitivity of 89% and a specifi city of 57%).

• After linear regression analysis, we found that the urinary citrate level is an independent factor associated with the changes in bone densitometry T-score values of patients.

CONCLUSIONS

• The patients with severe lithogenesis presented with hypocitraturia, which was associated with lower bone mineral density.

• The calcium : citrate ratio, which is linearly related to the bone resorption marker β-crosslaps, could be useful in evaluating the risk of severe lithogenesis when this ratio is > 0.25.

 

Read Previous Articles of the Week

Editorial: The importance of citrate in patients with calcium stones and loss of bone mineral density

Stone disease and osteopaenia are both common conditions, and reduced bone mineral density (BMD) is an increasingly recognized complication in stone formers; indeed, in a previous paper in BJUI, Arrabal-Polo et al. reported that patients with recurrent stones have lower BMD compared with controls or patients with just a single episode of urolithiasis.

Although the exact pathogenesis of bone loss in stone disease is yet to be determined, the conceptually obvious relationship with hypercalciuria is well documented. In the present study, Arrabal-Polo et al. emphasise that hypocitraturia is also associated with reduced BMD. Furthermore, they found a higher calcium : citrate ratio in patients with a cumulative maximum stone diameter > 20 mm, or in those with frequent recurrences than in controls, and found that this correlated with higher levels of β-crosslaps, consistent with increased bone resorption in these patients.

We commented in our previous editorial that metabolic abnormalities should be sought in recurrent stone formers, and managed in a multi-disciplinary setting. In addition to dietary advice, options for treatment include bisphosphonates (which inhibit bone resorption, and are commonly used in osteoporosis), thiazide diuretics (which reduce calcium excretion and can increase BMD) and potassium citrate (which acts as an alkalinizing agent mitigating the bone restorative effect of acidosis). This approach is supported by recent data in medullary sponge kidneys, in which hypercalciuria and hypocitraturia were commonly detected in association with reduced BMD. Patients who were treated with potassium citrate were found to have increased urinary pH citrate levels, and an improvement in their BMD.

In the present article, Arrabal-Polo et al. suggest using a calcium : citrate ratio of 0.25 for predicting the risk of future recurrent stone formation, but this value could equally be used to predict the risk of patients having reduced BMD and the complications that may follow. Either way, their findings strengthen the argument for metabolic screening of recurrent stone formers, and for an assessment of these patients’ BMD. Patients can then be appropriately treated with a thiazide diuretic, potassium citrate, or a bisphosphonate, either singly or in combination, according to the abnormalities detected and their progress on treatment.

Daron Smith
Stone and Endourology Unit, University College Hospital, London, UK

Chris Laing
UCL Centre for Nephrology, Royal Free Hospital London, London, UK

Video: Commentary by Dr Arrabal-Polo on the calcium : citrate ratio.

Importance of citrate and the calcium : citrate ratio in patients with calcium renal lithiasis and severe lithogenesis

Miguel Angel Arrabal-Polo*, Miguel Arrabal-Martin*,  Salvador Arias-Santiago**, Juan Garrido-Gomez, Antonio PoyatosAndujar§ and Armando Zuluaga-Gomez**

Department of Urology, San Cecilio University Hospital, **Department of Medicine, Baza Hospital, Department of  Medicine, University of Granada, and Departments of Traumatology and §Biochemistry, San Cecilio University Hospital, Granada, Spain

OBJECTIVE

• To analyse the importance of urinary citrate and the urinary calcium : citrate  ratio in patients with calcium renal lithiasis and severe lithogenesis compared with a control group of patients without lithiasis.

MATERIAL AND METHODS

• A cross-sectional study of 115 patients in eastern Andalusia, Spain was conducted.

• The patients were divided into two groups: Group A: 56 patients aged 25 – 60 years without calcium renal lithiasis; Group B: 59 patients aged 25 – 60 years, presenting with calcium renal lithiasis and severe lithogenesis.

• The citrate levels and the calcium : citrate ratio in the patients’ urine and the relationship of these two factors to lithiasic activity were analysed and compared.

RESULTS

• In Group B, 32.2% of the patients presented with hypocitraturia, compared with 14.3% of the patients in Group A (P = 0.02).

• The urinary citrate levels were lower in Group B than in Group A (P = 0.001) and the calcium : citrate ratio was higher in Group B than in Group A (P = 0.005).

• The results suggest that a patient urinary calcium : citrate ratio > 0.25 indicates severe lithogenesis (with a sensitivity of 89% and a specificity of 57%).

• After linear regression analysis, we found that the urinary citrate level is an independent factor associated with the changes in bone densitometry T-score values of patients.

CONCLUSIONS

• The patients with severe lithogenesis presented with hypocitraturia, which was associated with lower bone mineral density.

• The calcium : citrate ratio, which is linearly related to the bone resorption marker β-crosslaps, could be useful in evaluating the risk of severe lithogenesis when this ratio is > 0.25.

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