'Bad dietary habits' and recurrent calcium oxalate nephrolithiasis.

[UUrea×V (mmol/day)×0.18]+13 A 32-year-old truck driver had previously been treated =Protein consumption (g/day) with allopurinol because of hyperuricaemia and gouty arthritis. After having first formed a kidney stone at (adapted from [5]); age 20, he had passed calculi annually for 8 years before he finally underwent ESWL for bilateral radioit amounted to 108.1 g or 1.25 g/kg BW per day. The opaque kidney stones. The patient, whose mother had patient’s daily intake of calcium from dairy products, suffered from renal stones, continued to live on a selfestimated by using a questionnaire based on tabulated selected diet, but considerably increased fluid intake. data of the calcium content of dairy products typically Three years later, after he had passed another stone, consumed in Switzerland [6 ], was 1240 mg/day. bilateral radio-opaque stones (3 stones on the right, 1 Treatment only consisted of dietary advice by a on the left side) were found on plain X-rays of the dietician who instructed the patient to reduce meat abdomen, and the patient was referred for metabolic protein intake to 5–7 servings per week, to lower evaluation of severe recurrent calcium stone disease. consumption of salt-rich foods (sausages, cheese) and Physical examination revealed a 32-year-old man not to add salt during meals. Furthermore, the patient (173 cm, 86.4 kg, body-mass index 28.9 kg/m2) with was told to reduce intake of oxalate-rich foods and to moderate hypertension (150/95 mmHg), but otherwise keep fluid intake high. Within 6 months, he lost 15 kg normal clinical findings. Laboratory analyses were as of weight, and urine chemistries were significantly follows: values for serum creatinine, sodium, potasaltered, as shown in Figure 1. Whereas excretion rates sium, chloride, phosphate, magnesium, albumin, and of oxalate, phosphate and urea were reduced by venous bicarbonate were normal, and uric acid was 40–50%, urinary citrate almost doubled. high-normal (399 mmol/l, upper normal limit 416). Four months later, urine volume remained very high Ionized calcium was 1.25 mmol/l, intact PTH 19 pg/ml (5430 ml/day), but the patient admittedly had (normal range 10–65), and calcitriol 51 pg/ml (25–79). increased his protein consumption, which was now In a 2-h fasting urine, Ca-E was 0.043 mmol/l GF calculated to be 102 g/day; this was also reflected by a (normal∏0.037), and pH 5.87; after 3 days of ammorise in UP×V to 57.3 mmol/day. Whereas hypercalciunium chloride loading, fasting urine pH dropped to ria (12.98 mmol/day) and hyperoxaluria 5.29, indicating normal urinary acidification [1]. (0.478 mmol/day) persisted, UCit×V had fallen into Unfortunately, no stone analysis was available. the low-normal range (1.94 mmol/day). The patient Nevertheless, the diagnosis of recurrent calcium was told to lower meat protein intake more and to nephrolithiasis with idiopathic hypercalciuria, hypslightly reduce calcium intake from dairy products eroxaluria, and hypocitraturia was made, based on the towards normal, i.e. 800 mg/day. Another 4 months presence of bilateral radio-opaque calculi and measurelater, the patient’s urine volume was still high ments of main urinary risk factors for stone disease (5800 ml/day), whereas UCa×V had normalized [2,3] in two 24-h urines collected on free-choice diet (8.76 mmol/day) as well as protein consumption, (Table 1). derived from UUrea×V, had dropped to 81 g/day; this Excessive consumption of protein and salt, an was also reflected by a decrease in UP×V to aggravating factor for calcium nephrolithiasis [4], was 46.2 mmol/day. On the other hand, UCit×V had identified based on measurements of urinary markers increased to 2.56 mmol/day. Surprisingly, UOx×V was of protein and salt consumption (Table 1). Assuming erratically high, i.e. 1.259 mmol/day. Since measuresteady-state conditions, daily protein consumption was ments of urinary glycollate [6 ] had recently become available in our hospital, glycollate excretion rate was determined in the same 24-h urine and found to be Correspondence and offprint requests to: PD Dr Bernhard Hess, 0.371 mmol/day (normal∏0.700 mmol/day). This patDepartment of Medicine, University Hospital, CH-3010 Berne,