From the Guidelines
Treatment for calcium oxalate kidney stones should prioritize increasing fluid intake to at least 2 liters per day, as recommended by the American College of Physicians 1, to dilute urine and prevent stone formation. This approach is crucial in reducing the concentration of lithogenic factors in the urine, thereby decreasing the risk of stone formation.
Key Recommendations
- Increasing fluid intake to achieve at least 2 liters of urine per day to prevent recurrent nephrolithiasis, as recommended by the American College of Physicians 1.
- Dietary modifications, including limiting oxalate-rich foods, reducing sodium intake, moderating animal protein consumption, and maintaining normal calcium intake from food sources rather than supplements, as suggested by the American Urological Association 1.
- Pharmacologic management with thiazide diuretics, citrate, or allopurinol may be considered for patients with active disease in which increased fluid intake fails to reduce the formation of stones, as recommended by the American College of Physicians 1.
Rationale
The American College of Physicians recommends management with increased fluid intake spread throughout the day to achieve at least 2 liters of urine per day to prevent recurrent nephrolithiasis 1. Additionally, the American Urological Association suggests that clinicians should counsel patients with calcium oxalate stones and relatively high urinary oxalate to limit intake of oxalate-rich foods and maintain normal calcium consumption 1.
Treatment Options
- For existing stones, treatment options range from watchful waiting for small stones (less than 5 mm) that may pass naturally with pain management using NSAIDs or opioids.
- Procedures like extracorporeal shock wave lithotripsy (ESWL), ureteroscopy, or percutaneous nephrolithotomy may be considered for larger stones. These approaches work by addressing the underlying causes of calcium oxalate stone formation: high urinary calcium, low urinary citrate, high urinary oxalate, and low urine volume, which together create an environment conducive to crystal formation and aggregation.
From the FDA Drug Label
The changes induced by Potassium Citrate produce urine that is less conducive to the crystallization of stone-forming salts (calcium oxalate, calcium phosphate and uric acid). Increased citrate in the urine, by complexing with calcium, decreases calcium ion activity and thus the saturation of calcium oxalate Citrate also inhibits the spontaneous nucleation of calcium oxalate and calcium phosphate (brushite). Potassium Citrate therapy was associated with inhibition of new stone formation in patients with distal tubular acidosis. The stone formation rate was reduced in all groups as shown in Table 1.
Treatment of Calcium Oxalate Stones:
- Potassium citrate is indicated for the management of Hypocitraturic calcium oxalate nephrolithiasis.
- The objective of treatment with Potassium Citrate is to provide Potassium Citrate in sufficient dosage to restore normal urinary citrate and to increase urinary pH to a level of 6.0 or 7.0.
- Dosage:
- In patients with severe hypocitraturia, therapy should be initiated at a dosage of 60 mEq/day.
- In patients with mild to moderate hypocitraturia, therapy should be initiated at 30 mEq/day.
- Key Benefits:
- Decreases calcium ion activity and thus the saturation of calcium oxalate.
- Inhibits the spontaneous nucleation of calcium oxalate and calcium phosphate.
- Reduces the stone formation rate. 2
From the Research
Treatment Options for Calcium Oxalate Stones
- Medical treatment for calcium oxalate stones includes potassium citrate (K-CIT) and hydrochlorothiazide (HCT) to reduce urinary calcium excretion in patients with hypercalciuria 3.
- K-CIT has been shown to be effective in reducing calcium excretion and increasing citrate excretion in patients with calcium oxalate stones and hypercalciuria, with efficacy comparable to HCT treatment 3.
- Conservative treatment strategies for idiopathic calcium oxalate urolithiasis include increasing fluid intake, restricting high oxalate foods, and maintaining a recommended calcium intake of 800-1200 mg/day 4.
Dietary Recommendations
- Patients with calcium oxalate stones are advised to increase their fluid intake to achieve a urine volume of 2 l or more 4.
- Dietary calcium restriction is not recommended as it can increase urinary oxalate and contribute to a negative bone balance 4.
- High oxalate foods should be restricted, and daily protein intake should be between 0.8 and 1 g/kg body weight/day 4.
Medical Therapy
- Thiazide treatment has been shown to successfully lower urine calcium and both calcium oxalate and calcium phosphate supersaturations in both types of stone formers 5.
- Alkali therapy, such as potassium citrate, may not confer the same benefits on calcium phosphate stone formers as it does on calcium oxalate stone formers 5.
- Expulsive therapy using nifedipine or tamsulosin, both associated with ketoprofene, after shock wave lithotripsy of ureteral stones has been shown to be effective in facilitating ureteral stone expulsion 6.
Future Directions
- Further research is needed to explore the potential benefits and risks of different treatment options for calcium oxalate stones, including the use of calcium supplements and other medical therapies 4, 7.
- The mechanism of calcium oxalate stone formation is still largely unclear, and further studies are needed to understand the complex multistep formation process of kidney stones 7.