From the Guidelines
The most likely finding during metabolic evaluation of this 51-year-old woman with recurrent stone formation is hyperoxaluria and hypocitraturia, due to her clinical presentation of Crohn's disease with persistent diarrhea, which suggests enteric hyperoxaluria. This condition is characterized by fat malabsorption, leading to increased binding of calcium with fatty acids in the intestinal lumen, leaving oxalate free to be absorbed, as noted in the study by 1. Additionally, the persistent diarrhea causes bicarbonate loss, resulting in metabolic acidosis, which decreases citrate excretion by the kidneys, as discussed in the guideline by 1. The management of this condition should include:
- Increasing fluid intake to at least 2-3 liters daily, as recommended by 1, to help reduce the concentration of oxalate and other stone-forming substances in the urine.
- Dietary oxalate restriction, as suggested by 1, to reduce the amount of oxalate available for absorption.
- Calcium supplementation (500-1000 mg) with meals, as noted in the example answer, to bind oxalate in the gut and reduce its absorption, which is supported by the study by 1 that found a higher calcium diet is associated with a reduced risk of stone formation.
- Potassium citrate supplementation (typically 10-20 mEq two to three times daily) to increase urinary citrate levels and help alkalize the urine, as recommended by 1. Treating the underlying Crohn's disease is also essential to reduce intestinal malabsorption, as emphasized by 1. Regular monitoring of urinary parameters and stone formation is necessary to assess treatment efficacy and adjust therapy as needed, as discussed in the guideline by 1.
From the FDA Drug Label
Patients with chronic diarrheal syndrome, were treated with Potassium Citrate, The main inclusion criterion was a history of stone passage or surgical removal of stones during the 3 years prior to initiation of Potassium Citrate therapy The most likely finding during metabolic evaluation is hyperoxaluria due to the patient's history of Crohn's disease with persistent watery diarrhea, which can lead to an increased excretion of oxalate in the urine.
- Hyperoxaluria is a common finding in patients with chronic diarrheal syndrome, as seen in the patient's history of Crohn's disease.
- The patient's history of forming eight stones over the previous three years, along with intermittent UTIs and Crohn's disease, supports the likelihood of hyperoxaluria. 2
From the Research
Metabolic Evaluation Findings
The patient's history of Crohn's disease with persistent watery diarrhea and recurrent urinary tract infections (UTIs) suggests a high likelihood of hyperoxaluria. The most likely finding during metabolic evaluation is:
Causes of Hyperoxaluria
Hyperoxaluria can be caused by:
- Inherited disorders of glyoxylate metabolism leading to hepatic oxalate overproduction (primary hyperoxaluria) 3, 7
- Increased intestinal oxalate absorption (secondary hyperoxaluria) 3, 4, 5, 6
- Enteric hyperoxaluria, which can occur in patients with Crohn's disease due to extensive ileal resection or intestinal bypass surgery 4, 5, 6
Relationship between Crohn's Disease and Hyperoxaluria
Studies have shown that patients with Crohn's disease are at increased risk of developing hyperoxaluria and urinary stone formation due to:
- Increased intestinal oxalate absorption 4, 5
- Hyperabsorption of oxalate following extensive ileal resection 4
- Fat malabsorption, which can lead to increased binding of dietary calcium by free fatty acids, reducing the calcium available to precipitate dietary oxalate 6
Clinical Implications
The diagnosis of hyperoxaluria is crucial, as it can lead to: