From the Guidelines
The most likely finding during metabolic evaluation in this case is D. Hypocitraturia. This 51-year-old woman with recurrent kidney stones and persistent watery diarrhea is experiencing chronic diarrhea-induced metabolic acidosis. When the body is in a state of metabolic acidosis, the kidneys increase citrate reabsorption to help buffer the acid load, resulting in decreased urinary citrate excretion (hypocitraturia) 1. Citrate normally acts as an inhibitor of calcium stone formation by binding to calcium in the urine, preventing it from combining with oxalate or phosphate to form stones. With reduced urinary citrate, there is less inhibition of stone formation, increasing the risk of calcium-based stones. The patient's history of persistent watery diarrhea suggests chronic acid loss from the gastrointestinal tract, leading to this metabolic derangement. While hyperoxaluria may be present due to fat malabsorption from chronic diarrhea (enteric hyperoxaluria), the primary metabolic abnormality driving stone formation in this clinical scenario would be hypocitraturia from the chronic metabolic acidosis.
Some key points to consider in the management of this patient include:
- Increasing fluid intake to achieve at least 2 L of urine per day to prevent recurrent nephrolithiasis, as recommended by the American College of Physicians 1.
- Considering pharmacologic monotherapy with a thiazide diuretic, citrate, or allopurinol to prevent recurrent nephrolithiasis in patients with active disease in which increased fluid intake fails to reduce the formation of stones 1.
- Dietary changes, such as reducing dietary oxalate, reducing dietary animal protein and other purines, and maintaining normal dietary calcium, may also be beneficial in preventing recurrent kidney stones 1.
- The use of potassium citrate may be considered to increase urinary citrate excretion and reduce the risk of calcium stone formation 1.
Overall, the management of this patient should focus on addressing the underlying metabolic abnormalities contributing to stone formation, as well as implementing lifestyle and dietary changes to reduce the risk of recurrent kidney stones.
From the Research
Metabolic Evaluation Findings
The patient's history of intermittent UTIs, current stone disease, and persistent watery diarrhea suggests a possible underlying metabolic disorder. Based on the provided evidence, the most likely finding during metabolic evaluation is:
- Hyperoxaluria: This condition is characterized by excessive oxalate levels in the urine, which can lead to kidney stone formation 2, 3, 4, 5, 6.
- The patient's symptoms, such as watery diarrhea, may be related to intestinal diseases that increase the risk of secondary hyperoxaluria 2, 3.
Associated Metabolic Abnormalities
In addition to hyperoxaluria, the patient may also exhibit other metabolic abnormalities, including:
- Hypocitraturia: This condition is characterized by low citrate levels in the urine, which can increase the risk of kidney stone formation 3.
- Hypercalciuria: This condition is characterized by excessive calcium levels in the urine, which can also contribute to kidney stone formation 3.
- However, the most likely associated abnormality in this case is hypocitraturia, as the patient's symptoms and history suggest a possible intestinal disorder that may lead to impaired citrate absorption or production.
Urine Characteristics
The patient's urine characteristics may also provide clues about the underlying metabolic disorder. For example:
- Alkaline urine: This may be present in patients with certain intestinal disorders that lead to increased oxalate absorption and hyperoxaluria 3.
- However, the most likely urine characteristic in this case is acidic urine, which can contribute to the formation of kidney stones, particularly those composed of uric acid or calcium oxalate 3, 4.