Low Urinary Citrate, A Major Risk Factor for Calcium Stone Formation in Pakistan Is it Diet Induced?

Abstract

Renal stone disease is common in Pakistan; causes loss of days at work; destruction of kidneys, and renal failure of which it is common cause. (In Pakistan 10% of patients undergoing dialysis treatment have renal stone disease). New stones keep forming even after complete removal of the first stone. Therefore, it is worthwhile designing a prophylactic (preventive) programme. We focused on urinary citrate for two reasons. 1) Citrate is known to slow crystal aggregation. 2) Majority of our stone patients have low citrate excretion. Citrate supplementation should help prevent stone formation. As oral citrate is expensive and as citrate excretion is determined by alkali absorbed from the gut, we intend to study if NaHCO3 (an alkali source), could raise urinary citrate as efficiently as citrate therapy. Our study investigates: - Whether urinary citrate levels increased on administration of soda bicarbonate (NaHCO3) as effectively as oral potassium citrate; and - Whether oral bicarbonate increases alkali absorption as dramatically as citrate. Significance: If NaHCO3 is as effective, it will provide a cheap alternative to citrate therapy for the masses. (NaHCO3 costs only Rs 0.18 per day as compared to potassium citrate preparations, which are very costly and imported.) Progress so far: The study will on completion have assessed the effects of citrate and NaHCO3 40 patients (10 females, 30 males). We report results on completed tests on 35 patients (10 females; 25 males). Results to date: 1. Citrate increased urinary citrate levels in 29 of 35 (82.9%) patients. NaHCO3 increased the urinary citrate in 19 of 31 (61%) patients. The mean 24 hour urinary citrate levels increased from 279.2±146 mg to 433.39±211.1 (highly significant p= <0.000) after citrate administration. Urinary citrate did not rise significantly (p=0.036) after NaHCO3 administration. (338.05±166.0 mg/24 hours to 369.7±187.35 mg/24 hour after alkali administration). 2. The net alkali absorption increased with citrate from 12.3±27.0 to 56.2±36.3 (p<0.000) and with bicarbonate from 20.5±26.0 to 65.4±32.7 (p<0.000) Conclusions: 1. Though bicarbonate increased urinary citrate in 61% of patients, the rise was not significant. Citrate on the other hand increased urinary citrate in 82.9% of patients. 2. Net alkali raises with NaHCO3 as much as with oral citrate does as shown by rise in net alkali absorption strengthening our conviction stated previously that citrate excretion is not related to net alkali absorption. Summary of results: 1. NaHCO3 is not as affective in increasing urinary citrate as oral potassium citrate and can not be used as a substitute for raising urinary citrate. 2. There is evidence that net alkali absorption is not linked to citrate excretion.