腎臟尿酸結石治療

避免腎臟發生尿酸結石的方法有三種

鹼化尿液

增加水分補充

減少尿酸生成

TREATMENT

Because alkalinization of the urine with medical therapy can lead to dissolution of pure uric acid stones, more invasive procedures (such as extracorporeal shock wave lithotripsy) are usually not required. The three treatments options to prevent recurrent uric acid nephrolithiasis include [3]:

●Alkalinization of the urine

●Increased fluid intake

●Reduction of uric acid production with reduced purine intake and xanthine oxidase inhibitors

尿酸腎結石病患都應該鹼化尿液及增加水分補充

Urinary alkalinization and increased fluid intake should be prescribed to almost all patients with uric acid stones. The indications for xanthine oxidase inhibitors to reduce uric acid production depend upon whether uric acid stones are recurrent despite alkalinization or when alkalinization cannot be used and also upon the presence or absence of gout:

Xanthine Oxidase  inhibitor  主要用於鹼化尿液和補充水分治療無效的病患, 尿酸生成過多 (每天超過 1000 mg) 的病患, 鹼化尿液和補充水分可能無效, 但尿酸排泄在正常範圍內的病患,  xanthine oxidase inhibitor 仍有效

●Recurrent uric acid stones – Xanthine oxidase inhibitors are usually reserved for patients who continue to have stones despite urinary alkalinization and a prescribed higher fluid intake. Recurrent uric acid stone formation despite urinary alkalinization and increased hydration usually occurs in patients with high urinary uric acid excretion (exceeding 1000 mg/day [6 mmol/day]). However, xanthine oxidase inhibitor therapy is warranted in recurrent uric acid stone formers even if urinary uric acid excretion is in the reference range.

●Patients with gout – Patients with uric acid stones who also have recurrent or tophaceous gouty arthritis should be treated with a xanthine oxidase inhibitor for long-term control of gouty manifestations; the primary indication in such patients is gout and not necessarily the prevention of kidney stones (see "Pharmacologic urate-lowering therapy and treatment of tophi in patients with gout"). Urate-lowering therapy for gout with uricosuric agents is not indicated as first-line therapy in gouty stone formers to prevent stone recurrence, as this will not lead to a long-term change in the amount of uric acid in the urine.

In a patient with a history of uric acid stones and gout but ≤1 flare of gouty arthritis per year, there may be no specific indication for xanthine oxidase inhibitor therapy. Rather, urinary alkalinization and increased hydration are the initial treatment option in such patients. If, however, the patient prefers a medication that could reduce both gout flare frequency and recurrence of uric acid stones, we would agree to prescribe treatment with a xanthine oxidase inhibitor (along with increased hydration but not necessarily urinary alkalinization).

Urinary alkalinization — The effect of increasing the urine pH on uric acid solubility can be appreciated from the Henderson-Hasselbalch equation for the relationship between soluble urate and insoluble uric acid, where 5.35 is functionally the pKa for this reaction under conditions existing in urine [31]:

pH = 5.35 + log ([urate] ÷ [uric acid])

At a urine pH of 6.75, more than 90 percent of the total urinary uric acid will be the more soluble urate salt, thereby minimizing the risk of uric acid precipitation.

There are no randomized trials that have evaluated the efficacy of urinary alkalinization on recurrence or dissolution of uric acid stones. However, alkalinization is associated with a remarkable reduction in recurrent stone episodes in observational studies. As an example, the mean rate of recurrent uric acid stones among 18 patients was reduced from 1.2 to 0.01 stones per patient per year with long-term treatment with potassium citrate [32]. Alkalinization can also dissolve existing uric acid calculi, as demonstrated in eight patients with recurrent uric acid stones who underwent serial ultrasound examinations after initiating potassium citrate or potassium bicarbonate [33].

鹼化尿液過度可能會造成磷酸鈣結石, 所以維持尿液 pH 6.5~7 即可, pH 超過 7 以上, 效果並沒有更好.
另外, 也不需要持續維持鹼化尿液, 一天一次或兩天一次, 將尿液pH提升超過 6.5 以上, 就可以預防尿酸結石產生. (不用 24 小時)

Alkalinization therapy should target a urine pH between 6.5 and 7. Achieving a urine pH higher than 7 will provide little if any further benefit on uric acid stone formation and may increase the risk of calcium phosphate stone formation (figure 1). An alkaline urine pH may not need to be maintained at all times since raising the urine pH to at least 6.5 once per day or every other day may prevent uric acid stone formation [34].

可給予重碳酸鉀 或檸檬酸鉀, 可將已經出現的腎結石溶解, 也可以預防腎結石生成, 使用鉀鹽比鈉鹽好. 因為檸檬酸鈉或重碳酸鈉會增加鈣的排泄(經腎臟), 在某些病患會引起鈣結石. 

應建議病患在家自己測尿液pH

Either potassium bicarbonate or potassium citrate can be given, with the typical dose being 40 to 80 mEq/day (table 2) [3,32]. This regimen can dissolve preexisting pure uric acid stones and prevent the formation of new stones. Alkalinization with potassium salts is preferable since the sodium load with sodium citrate or sodium bicarbonate may increase calcium excretion and promote the formation of calcium stones in some patients [32]. Patients should be instructed to check their urine pH at home; this will help guide the amount of alkali required.