From the Guidelines
Calcium oxalate crystals in urine are primarily caused by high concentrations of calcium and oxalate that combine and form crystals, and the most effective way to reduce their formation is to drink plenty of water, limit oxalate-rich foods, and maintain adequate calcium consumption through diet rather than supplements, as supported by the most recent study 1.
Causes of Calcium Oxalate Crystals
The formation of calcium oxalate crystals in urine is a complex process that involves the interaction of various factors, including:
- High concentrations of calcium and oxalate in the urine
- Dehydration, which concentrates the urine and makes crystal formation more likely
- Dietary factors, such as excessive consumption of oxalate-rich foods (spinach, rhubarb, chocolate, nuts), high sodium intake, or high animal protein consumption
- Medical conditions, such as hyperparathyroidism, certain bowel diseases, recurrent urinary tract infections, and some genetic disorders
- Medications, such as vitamin C supplements (in doses over 1000mg daily), certain diuretics, and some calcium-based antacids
Prevention and Treatment
To reduce the formation of calcium oxalate crystals, the following measures can be taken:
- Drink plenty of water (at least 2-3 liters daily) to keep the urine diluted and reduce the concentration of substances that form crystals
- Limit oxalate-rich foods, such as spinach, rhubarb, chocolate, and nuts
- Reduce sodium and animal protein intake
- Maintain adequate calcium consumption through diet rather than supplements
- Consider taking potassium citrate or pyridoxine (vitamin B6) supplements, as they may help reduce urinary oxalate excretion and prevent crystal formation, as suggested by studies 1 and 1
Recent Study Findings
A recent study published in 2023 1 provides evidence-based recommendations for the prevention and treatment of calcium oxalate crystals in urine. The study suggests that a high fluid intake, adequate dietary calcium consumption, and limitation of oxalate-rich foods can help reduce the formation of calcium oxalate crystals. Additionally, the study recommends considering potassium citrate and pyridoxine supplements for patients with primary hyperoxaluria, a condition characterized by excessive oxalate production.
From the Research
Causes of Calcium Oxalate in Urine
- Calcium oxalate in urine is a multifactorial disease, and several factors contribute to its formation, including dietary and urinary risk factors 2
- Urinary oxalate has emerged as the most important determinant of calcium oxalate crystallization, while the role of urinary calcium has shifted to bone balance and osteoporosis 2
- Hypercalciuria, or high levels of calcium in the urine, is a common anomaly in patients with calcium oxalate stones, and treatment with potassium citrate or hydrochlorothiazide can help reduce urinary calcium excretion 3, 4
Dietary Factors
- Dietary oxalate and calcium can contribute to the formation of calcium oxalate in urine, and restricting high oxalate foods and increasing calcium intake to 800-1200 mg/day may help reduce the risk of stone formation 2
- Increasing fluid intake to achieve a urine volume of 2 l or more, restricting daily protein intake to 0.8-1 g/kg body weight/day, and including essential fats and increasing vegetable and fruit intake (except oxalate-rich vegetables) may also help reduce the risk of stone formation 2
Metabolic Disturbances
- Hyperparathyroidism and hyperthyroidism can lead to metabolic disturbances that contribute to the formation of calcium oxalate in urine, including increased serum and ionized calcium levels and urinary calcium excretion 5
- However, hyperthyroid patients do not have a significantly higher incidence of urolithiasis compared to normal subjects, suggesting that other factors may be involved in the formation of calcium oxalate stones 5
Treatment
- Potassium citrate supplementation can help reduce urinary calcium excretion and increase urinary citrate levels, which can help prevent the formation of calcium oxalate stones 3, 4, 6
- Thiazide treatment can also help reduce urinary calcium excretion and prevent stone recurrence, but its effectiveness may vary depending on the type of stone formed 3, 4