44,45

40-42

151

MEtabolic EvalUation and MEdical ManagEMEnt of stonE disEasE

collection” of urine. Cystine values should be requested when cystinuria is suspect. It is our routine to have the patient collect two 24 h urine samples on two different days (either consecutive or separate) with the patient on their “normal routine” (normal diet, fluid intake, medications, physical exercise, etc) .

In the past, a third 24 h urine collection was performed to differentiate between the various causes of hypercalciuria–Absorptive hypercalciuria Type I, Type II, and renal leak hypercalciuria. However, discrimination of specific causes of hypercalciuria, while important for physiologic discrimination, has little importance presently, as thiazide diuretics are the only medications available to treat patients with either absorptive or renal leak hypercalciuria.

Conservative Management

As already mentioned,conservative therapy may be effective as first-line treatment for first time stone formers and for those patients without significant risk factors for recurrent stone formation.21

Increased Fluid Intake

The first recommendation for all stone producers would be increased fluid intake as increased urine volume prevents urine stagnation and reduces crystallization of stone-forming salts. Recommended fluid intake is 2–3 L of liquids, preferably water, however, most beverages can be included in the total amount.

Radiologic Imaging

Radiologic imaging should be considered part of the basic metabolic evaluation which should not be overlooked. While the utility of imaging is greater as a clinical management tool, there are insights which can be gleaned from plain films, an intravenous pyelogram, or computed tomography (CT).In addition to assessing residual stone burden, radio-opacity/radiolucency of stones on plain films as compared to CT may indicate presence of uric acid, xanthine, and triamterene calculi. Intravenous pyelograms permit appraisal of anatomic anomalies and filling defects. CT scanning is currently the gold standard for the diagnosis of urolithiaisis and will identify stones of all compositions, except for indinavir calculi.30,31

Multiple researchers have reported the use of CT to ascertain stone composition based on measurement of Hounsfield units.32-38 In fact, the use of dual energy CT may further improve the diagnostic capabilities of CT.39 Additional studies are warranted to further define the use of CT imaging to better predict stone composition.

Citrus Juices

Especially in cases of hypocitraturia, the addition of citrus juices to fluid intake not only increases urine output but also contributes to the increase of urinary citrate levels, thereby increasing the inhibitory activity against stone formation. Both lemon and orange juices have been sown to reduce the risk of stone formation in certain patients, and can be used to supplement fluid intake in almost all individuals. Other studies have assessed the citrate concentrations of various citrate juices and drinks.42,43 In one study, the highest citrate concentrations were found in grapefruit juice (64.7 mmol/L), lemon juice (47.66 mmol/L), orange juice (47.36 mmol/L), pineapple juice (41.57 mmol/L), reconstituted lemonade (38.65 mmol/L), and lemonade flavored Crystal Light (38.39 mmol/L).

Controversy still exists in the literature with regard to the potential harm of grapefruit juice consumed in excessive amounts; therefore further studies are warranted to evaluate the clinical significance of other citrate-containing juices.

Medical Management

The primary goal of medical stone management is to prevent urine crystallization and hence the formation or growth of stones. This goal can be achieved either by conservative or by medical management.

Dietary Restrictions

General dietary advice refers to a low sodium and low animal protein diet. Previous studies have suggested that excessive sodium intake increases urinary calcium and decreases urinary citrate probably by producing mild metabolic acidosis and have demonstrated the different