From the Guidelines
Oxalate crystals in urine are primarily caused by high levels of oxalate in the body, which can result from dietary factors, metabolic disorders, or certain medical conditions, and the most effective way to reduce them is to limit high-oxalate foods, increase fluid intake to at least 2-3 liters daily, and maintain adequate calcium intake. The most common cause of oxalate crystals is consuming foods high in oxalate such as spinach, rhubarb, beets, chocolate, nuts, and tea 1. Inadequate fluid intake also contributes by concentrating urine and allowing crystals to form. Some medical conditions that increase oxalate levels include inflammatory bowel disease, short bowel syndrome, and certain genetic disorders like primary hyperoxaluria 1. Certain medications such as vitamin C supplements (in doses exceeding 1000mg daily) can increase oxalate levels as vitamin C can be metabolized to oxalate.
To reduce oxalate crystals, the following measures can be taken:
- Limit high-oxalate foods
- Increase fluid intake to at least 2-3 liters daily
- Maintain adequate calcium intake (which binds to oxalate in the gut preventing absorption) 1
- Treat any underlying medical conditions In some cases, medications like potassium citrate may be prescribed to help prevent crystal formation by making the urine less acidic 1. Persistent oxalate crystals should be evaluated by a healthcare provider as they can lead to kidney stone formation and kidney damage if left untreated.
It is also important to note that the use of nephrotoxic medications and existing renal disease may also play a role in the formation of oxalate crystals 1. Additionally, a low-fat diet or replacing with MCT and oral calcium supplementation at mealtime have also been considered as preventive measures 1. Correction of metabolic acidosis and supplementation with citrate and magnesium supplementation may prevent stone formation 1.
Overall, a comprehensive approach that includes dietary changes, pharmacologic management, and treatment of underlying medical conditions is necessary to reduce the risk of oxalate crystals in urine and prevent kidney stone formation. The most recent and highest quality study 1 recommends management with increased fluid intake and pharmacologic monotherapy with a thiazide diuretic, citrate, or allopurinol to prevent recurrent nephrolithiasis in patients with active disease.
From the Research
Causes of Oxalate Crystals in Urine
The presence of oxalate crystals in urine can be attributed to several factors, including:
- Primary hyperoxaluria, a group of inherited disorders that affect glyoxylate metabolism, leading to hepatic oxalate overproduction 2
- Secondary hyperoxaluria, which can result from increased intestinal oxalate absorption, nutritional deficiencies, decreased fluid intake, impaired excretion, and increased dietary consumption of oxalate 3, 4
- Enteric hyperoxaluria, which occurs due to gastrointestinal disorders associated with fat malabsorption and increased absorption of dietary oxalate 5, 6
- Ingestion-related hyperoxaluria, which can be caused by consuming large quantities of oxalate-rich foods, such as green vegetables 4
- Dehydration, which can contribute to the formation of calcium oxalate crystals in the urine 2
Underlying Conditions
Certain underlying conditions can increase the risk of developing oxalate crystals in urine, including:
- Chronic kidney disease (CKD), which can impair the excretion of oxalate and increase the risk of oxalate nephropathy 4
- Renal failure, which can lead to the accumulation of oxalate throughout the body, a state termed oxalosis 6
- Gastrointestinal disorders, such as those associated with fat malabsorption, which can increase the absorption of dietary oxalate 3, 6