Editing Stones: Evaluation and Medical Management (section)

== Diet Therapies ==
* '''<span style="color:#ff0000">General diet therapies to reduce risk of stone recurrence (6)'''
*# '''<span style="color:#ff0000">Increase fluid intake (urine volume of > 2.5 liters daily)'''
*# '''<span style="color:#ff0000">Limit sodium intake (≤100 mEq (2,300 mg) per day)'''
*# '''<span style="color:#ff0000">Moderate calcium intake (1,000-1,200 mg per day)'''
*# '''<span style="color:#ff0000">Limit intake of oxalate-rich foods'''
*# '''<span style="color:#ff0000">Increase intake of fruits and vegetables'''
*# '''<span style="color:#ff0000">Limit intake of non-dairy animal protein'''

=== Increase fluid intake ===
#'''<span style="color:#ff0000">Fluid intake that will achieve a urine volume of > 2.5 liters daily is recommended in all stone formers</span>'''
#*An RCT of recurrent calcium oxalate stone formers randomized to a high fluid intake vs. no specific recommendations found significantly reduced stone recurrence rates in the high fluid intake group (12% vs. 27%, respectively, at 5 years)
#*Although there is no definitive threshold for urine volume and increased risk, an accepted goal is ≥2.5 liters of urine daily.#**Because of insensible losses and varying intake of fluid contained in food, a universal recommendation for total fluid intake is not appropriate
#*'''Overall, most evidence suggests that it is not the type of fluid ingested that is important for stone prevention but rather the absolute amount of fluid volume taken in per day'''
#** Water hardness should be a minor concern with respect to stone formation
#** Carbonated water may provide some protective benefit
#** Citrus juices (particularly lemon and orange juices) may be a useful adjunct to stone prevention
#**'''Alcoholic beverages, coffee, decaffeinated coffee, tea and wine have been shown to be associated with a lower risk of stone formation'''
#**'''Sugar-sweetened beverages demonstrated an increased risk.'''
#***'''The only specific beverage that has been evaluated for an effect on stone recurrence in an RCT is soft drinks; the group avoiding soft drinks demonstrated a marginally lower rate of stone recurrence at the end of the 3-year trial but the effect appeared to be limited to those consuming primarily phosphoric acid-based (e.g. colas) rather than citric acid-based soft drinks'''
#***'''Soda flavored with phosphoric acid may increase stone risk, whereas those with citric acid may decrease risk'''
#**** Several sodas are acidified by citric acid and contain an amount of citrate equal to or greater than that of lemonade, including Diet Sunkist Orange, Diet 7Up, Sprite Zero, Diet Canada Dry Ginger Ale, Sierra Mist Free, Diet Orange Crush, Fresca, and Diet Mountain Dew. All of the aforementioned sodas have the potential to decrease the risk of kidney stones similar to or greater than lemonade.
#**** In contrast, colas, including Caffeine Free Diet Coke, Diet Coke, Diet Coke with Lime, Coke Zero, Caffeine Free Diet Pepsi and Pepsi, are acidified by phosphoric acid, not by citric acid and contain low citrate levels.
#***** One randomized study of recurrent stone formers with baseline soda consumption > 160 ml per day, found that over a 3-year period those who abstained from any soft drink consumption had a lower risk of symptomatic stone events (34%) compared to those who continued to drink sodas acidified by phosphoric acid (41%; RR, 0.83).§
#***'''Performance sports drinks'''
#**** '''May increase urinary citrate and pH''' thereby reducing risk of stones.
#***** However, these drinks have a high fructose and total carbohydrate content so they should not be recommended as the primary means of hydration for stone formers.
#**** Do not lead to hypernatriuria, even though sodium content may be high
#**** No effect on urinary calcium, oxalate, and uric acid.

=== Limiting sodium intake ===

* '''<span style="color:#ff0000">Limiting sodium intake (target of ≤100 mEq (2,300 mg)) is recommended in patients with calcium stones and relatively high urinary calcium</span>'''

* '''High sodium intake is associated with:'''
*# '''Increased calcium excretion'''
*# '''Increased urinary pH'''
*# '''Decreased citrate excretion'''
* RCTs have demonstrated a benefit of dietary sodium restriction

=== Moderate calcium intake ===

* '''<span style="color:#ff0000">Consuming 1,000-1,200 mg per day of dietary calcium is recommended in patients with calcium stones and relatively high urinary calcium</span>'''
**'''A lower calcium diet in the absence of other specific dietary measures is associated with an increased risk of stone formation'''
***'''Lower calcium intake results in insufficient calcium to bind dietary oxalate in the gut, thereby increasing oxalate absorption and urinary oxalate excretion.'''
**'''In contrast, the RDA of calcium, defined as 1,000-1,200 mg/day for most individuals, was shown to be associated with reduced risk'''
* '''Calcium supplements are safe if attention is paid to preparation (calcium citrate appears to be a more stone-friendly calcium supplement because of the additional inhibitory action of citrate) and especially timing (should be taken with meals)'''

=== Limit intake of oxalate-rich foods ===

* '''<span style="color:#ff0000">Limiting intake of oxalate-rich foods and maintaining normal calcium consumption is recommended in patients with calcium oxalate stones and relatively high urinary oxalate</span>'''

*'''Urinary oxalate is also modulated by calcium intake, which influences intestinal oxalate absorption'''
*'''Other factors that may contribute to higher urinary oxalate include vitamin C''' (ascorbic acid is metabolized to oxalate) '''and other over-the-counter nutrition supplements.'''
*Although dietary oxalate clearly plays a role in increased urinary oxalate, it is difficult to restrict its intake because oxalate is ubiquitous and found in most vegetable matter. However, it is important to avoid large portions of '''foodstuffs that are rich in oxalate, such as spinach, beets, chocolate, nuts, and tea.'''
* Whereas general advice on a restricted-oxalate intake might be given to patients with recurrent nephrolithiasis, '''a low-oxalate diet would be most useful in patients with enteric hyperoxaluria, such as those with underlying bowel abnormalities or previous gastric bypass surgery'''

=== Increase intake of fruits and vegetables ===

* '''<span style="color:#ff0000">Recommended in patients with calcium stones and relatively low urinary citrate</span>'''

*'''Dietary citrate increases urinary citrate excretion'''
**Although a number of fruits and juices have been evaluated for their effect on urinary stone risk factors, none have been prospectively evaluated in an RCT assessing actual stone formation.
*'''Urinary citrate excretion is determined by acid-base status; conditions such as metabolic acidosis, renal tubular acidosis and chronic diarrhea, and some medications, such as carbonic anhydrase inhibitors, may promote hypocitraturia'''
**Acidosis can arise from a diet that is inordinately rich in foods with a high potential renal acid load such as meats, fish, poultry, cheese, eggs, and to a lesser extent, grains.

=== Limit intake of non-dairy animal protein ===

* '''<span style="color:#ff0000">Recommended in patients with calcium stones and relatively low urinary citrate</span>'''
* '''<span style="color:#ff0000">May help reduce stone recurrence in patients with uric acid stones or calcium stones and relatively high urinary uric acid</span>'''

*'''Protein intake increases urinary calcium, oxalate, and uric acid excretion'''
**'''Urinary uric acid is derived from both endogenous and exogenous sources'''
***Diet-derived purines account for an ≈30% of urinary uric acid
* '''If diet assessment suggests that purine intake is contributory to high urinary uric acid, patients may benefit from limiting high- and moderately high purine containing foods.'''
**'''"High purine" foods are generally considered specific fish and seafood (anchovies, sardines,''' herring, mackerel, '''scallops and mussels)''', water fowl, '''organ meats,''' glandular tissue, gravies and meat extracts.
**'''"Moderately-high" sources of purines include other shellfish and fish,''' game meats, mutton, '''beef, pork, poultry''' and meat-based soups and broths
*RCTs have demonstrated a benefit of a diet with reduced animal protein (meat) intake

=== Cystine Stones ===
*'''Patients with cystine stones should be counselled to increase fluid intake and limit sodium and protein intake'''
**'''High fluid intake is particularly important in cystine stone formers'''; the target for urine volume is typically higher than that recommended to other stone formers; '''oral intake of ≥4 L/day is often required'''
**Lower sodium intake has been shown to reduce cystine excretion
**Limiting animal protein intake is of benefit in patients with cystine stones

=== Other ===
*Weight-loss diets
** The consumption of a low-carbohydrate, high-protein diet delivers a marked acid load to the kidney, increases the risk for stone formation, and may increase the risk of bone loss

* '''Vitamin D'''
** '''Controversy exists over the role of vitamin D supplementation and kidney stone formation'''
** '''Patients who undergo vitamin D repletion should have their 24-hour urine calcium monitored'''