Kidney Stones – What’s the diagnosis?

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A 65yo man was reviewed in the clinic for assessment of kidney stones. He has a history of stones for at least 8 years and has been passing small calculi on a regular basis for the last few months. His 24 hour urine results are shown below (results are 24 hour total values unless otherwise specified):

Volume, Liters
Sodium, mmol/day
Supersaturation Calcium Oxalate
Potassium, mmol/day
Calcium, mg/day
Magnesium, mg/day
Oxalate, mg/day
Phosphate, mg/day
Citrate, mg/day
NH4, mmol/day
Supersaturation Calcium Phosphate
Chloride, mmol/day
Urine pH
Sulphate, mEq/day
Supersaturation Uric Acid
Urea Nitrogen, g/day
Uric Acid, mg/day
Protein Catabolic Rate

He has a high risk for calcium oxalate and uric acid stones. His urine citrate and sodium are remarkably low and he has a very low urine volume. His BP in the clinic was normal as were his labs apart from a serum creatinine of 1.3mg/dl

What is the underlying diagnosis (an important  piece has been left out of his background history)?
What is the best approach to treating his kidney stones?

Answers in the comments please (if this proves popular we may make it a regular feature).


  1. Very likely IBD, Crohn's disease, with chronic diarrhea and enteric hyperoxaluria;
    The missing hint could have been "chronic diarrhea"
    1. Fluid intake > 3 L per day
    2. Ca with meals
    3. K citrate
    4. Low oxalate diet.

  2. short bowel syndrome.
    Relative increased absorption of oxalate (though absolute value not particularly high but relatively high given urine volume).
    Needs urine alkalinization with potassium citrate to supplement citrate and prevent uric acid and calcium oxalate stones.

  3. high ouput from ileostomy. Loss of volume, base and sodium.

  4. gastrointestinal disorder as the main pathophysiology.

    Specific therapy for the malabsorptive disorder, such as a gluten-free diet for patients with sprue, is the first line of treat- ment of enteric hyperoxaluria. More generalized therapy for steatorrhea, such as a low-fat diet, cholestyramine, and adminis- tration of medium-chain triglycerides, may reduce fat malabsorp- tion as well as oxalate absorption and subsequent excretion. The low-oxalate diet and mealtime calcium carbonate prescribed for patients with dietary oxaluria are also helpful for these patients. The diarrhea associated with these disorders may result in low urine volumes, hypokalemia, hypocitraturia, and hypomagnes- uria. Patients should therefore be advised to increase their fluid intake and to take potassium citrate (in this case, the liquid, although unpalatable, is better absorbed than the tablets) as well as a magnesium supplement. Magnesium also serves as a urinary stone inhibitor and can be given as magnesium gluconate (0.5 to 1 g every 8 hours) or magnesium oxide (400 mg every 12 hours.

    From Comprenhesive clinical Nephrology.

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