Uric Acid Stone Dissolution
Date issued: March 2024
Review date: March 2026
Ref: B-507/JP/Urology/Uric Acid Stone Dissolution
PDF: Uric Acid Stone Dissolution final March 2024.pdf [pdf] 231KB
Introduction
Uric acid kidney stones most commonly form when a person’s urine is acidic. De-acidifying, or “alkalinising”, the urine (raising its pH) can help to prevent new uric acid stones forming or existing uric acid stones growing. In some cases, very strongly alkalinising the urine can dissolve uric acid kidney stones. This can be achieved using a medication called sodium bicarbonate.
Sodium bicarbonate will usually be prescribed by the urologist (stone surgeon) or nephrologist (kidney doctor). The treatment is taken for 6 weeks. During this time you will need to record the acidity (pH) of your urine in this booklet using urine dipsticks so that the medical team can adjust the dosing. You will also need a blood test after about a week on the treatment. You will have regular telephone follow up with the nursing team. After 6 weeks you will stop the treatment and soon after that you will have a scan to see if the stones have dissolved.
Timeline of therapy
Before treatment
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Baseline pH recording
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Baseline blood tests
Week 1 of treatment
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Sodium bicarbonate dose: 2 grams, taken 3 times a day
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Record urinary pH 3x a day for the first week (aiming for a pH 7-8)
First blood tests and review
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Blood tests organised for 7-10 days after starting treatment
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Bloods, pH and medication dosing reviewed by nurse via telephone appointment
If the dose is increased at the first review, an additional review is scheduled for a week or so later. In this case, continue to record the urinary pH 3x a day before this. Blood tests are not required.
If the dose is not increased at the first review then a midpoint review is scheduled for around the third or fourth weeks.
Midpoint review
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Record urinary pH 3x a day for 2 days prior to your review
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You will have blood tests organised ahead of the review
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The blood results, pH results and medication dosing will be reviewed by the nurse at a telephone appointment
The treatment is completed after 6 weeks and a CT scan is performed soon afterwards.
Recording your urine pH (acidity)
You will be given pH strips to test the pH of your urine. A sample of your urine should be collected in a pot. The test strip should then be dipped into the urine (for 3 to 5 seconds). It is then ready to read immediately. The strips come in a box with colour coding to pH numbers. We are usually targeting pH readings of around 7 to 8.
Week 1 of treatment: sodium bicarbonate dose ______
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Date |
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pH reading |
Side effects (if any) |
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Week 2 onwards of treatment (if dose increased)
Sodium bicarbonate dose:_______________________
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Date |
Time |
pH reading |
Side effects (if any) |
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Midpoint review: sodium bicarbonate dose__________
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Time |
pH reading |
Side effects |
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Telephone appointment dates
Week 1 follow up
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Blood test:
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Nurse telephone appointment:
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Dose to continue taking:
Week 2 follow up (if required)
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Nurse telephone appointment:
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Dose to continue taking:
Midpoint review
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Blood test:
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Nurse telephone appointment:
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Dose to continue taking:
7 Week CT scan
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Date and time:
Fluids
Ensuring you pass dilute urine is often the single most important measure you can take to stop kidney stones of all kinds from forming or growing. This means drinking enough fluids to keep your urine clear; usually 2-3 litres a day (and more if exercising or if it is hot). It is also important to keep hydrated overnight.
What you drink is probably less important but try to avoid drinks with high calorie contents (such as fruit juices or fizzy drinks) as they can lead to weight gain and dental problems. Limit alcohol to within the weekly recommended guidelines (14 units spread across 3 or more days). Adding a squirt of fresh lemon juice to water will help provide citrate which stops stones forming.
Dietary advice for Uric Acid Stones
Uric acid is made from the breakdown of purines that are found in certain foods. Reducing your intake of high purine foods helps to prevent uric acid stone formation. The same advice is given to patients with gout (which is due to uric acid crystals in the joints instead of the kidneys).
Foods which are high in purines and should be limited include; game and red meat, oily fish and seafoods, offal and yeast extracts.
Foods which contain moderate amount of purines and should be eaten in moderation include; meats, poultry, dried peas and beans, mushrooms, Quorn, wholegrains, asparagus, cauliflower and spinach.
Foods which are low in purines include; dairy, eggs, bread, low fibre cereals, pasta, fruit and most vegetables (see moderate purines)
