Slideshow
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Kidney_stones_quiz_1--renal_allograft_ultrasound2.
Renal allograft ultrasound showing 2 separate areas of increased echogenicity with shadowing consistent with stones
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Slide
CT without contrast view showing 2 separate areas of calcification in the renal allograft
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Slide
CT without contrast view showing 2 separate areas of calcification in the renal allograft
Revisiting a previously discussed case, a 60-year-old woman complained of pain in the right lower abdomen in the region of her kidney allograft. She had a deceased donor renal transplant 8 years previously. Her native kidney disease was due to diabetes and other medical diagnoses, including hypertension and peripheral vascular disease. She had a prior episode of allograft nephrolithiasis. Her medications include amlodipine, hydrochlorthiazide, famotidine, lovastatin, metoprolol, prednisone, and tacrolimus. On examination she was afebrile. She did have tenderness to palpation in the right lower quadrant and over the area of her allograft.
Her white blood cell count was 6,200. At baseline, her creatinine level was 1.5 mg/dL, calcium level was 8.4 mg/dL, sodium was 134 mEq, potassium was 4 mEq/L, and bicarbonate was 24 mEq/L. Urinalysis showed a specific gravity of 1.012, pH 6.5, more than 180 red blood cells, and 50 white blood cells
Two different imaging modalities demonstrating nephrolithiasis and representative images are shown. She was treated for presumptive pyelonephritis and eventually underwent urologic procedure for relief of stone burden.
Her stone analysis revealed large component of calcium oxalate. Her urine calcium excretion was 300 mg in 24 hours, and her urine sodium total 90 mEq in 24 hours.
Submit your diagnosis to see full explanation.
This case was provided by Kevin Harley, MD, Assistant Clinical Professor of Medicine at the University of California in Irvine.
References
Borghi L, Schianchi T, Meschi T, Guerra A, Allegri F, Maggiore U, Novarini A. Comparison of two diets for the prevention of recurrent stones in idiopathic hypercalciuria. N Engl J Med. 2002 Jan 10;346(2):77-84
Coe FL, Worcester EM, Evan AP. Idiopathic hypercalciuria and formation of calcium renal stones. Nat Rev Nephrol. 2016 Jul 25
Answer: C
Explanation
A patient with recurrent nephrolithiasis requires a complete diagnostic assessment of urine chemistry and stone burden. Such studies include 24-hour urine studies to quantify urine sodium, calcium, oxalate, citrate, urea nitrogen, and volume among other values including supersaturations of calcium phosphorus, and urine pH.
For those with calcium-based stones, preliminary recommendations to decrease stone recurrence risk include increasing fluid (water) intake over 2 liters per day. Additionally, at least 1 randomized trial has shown the benefit of dietary sodium restriction to less than 2.3 grams of sodium per day, and animal protein restriction to under 0.7 g per kg per day. Reduction in dietary calcium is not advised, as it may further gut absorption of oxalate and resultant stone formation.
Medical management of those who have increased urinary calcium excretion despite low salt diet includes the use of thiazide diuretics. Amiloride, a potassium sparing diuretic, can be added in cases where maximal thiazide use does not meet urinary calcium reduction goals. (Triamterene use is generally avoided.) Patients should also be counseled to reduce supplemental vitamin C administration.
Hypocitraturia may potentiate calcium-based stone formation. Thus, agents such as potassium citrate may be prescribed to raise urinary citrate excretion in certain patients.
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