The trouble with uric acid crystals, is you know they are there, but you cannot see them.

It’s worrying to know there are millions of tiny particles floating round your body, that remain hidden.

Now, strictly speaking, they don’t always remain hidden, as large deposits form tophi, that can break through the skin. But for our own peace of mind, and to help our doctors diagnosis and treatment, it really is a good idea to see what is happening in our joints.

Traditionally, the only way to test for the presence of uric acid crystals is to analyze fluid from the joints. Recently, there is hope that DECT might eventually replace this invasive procedure, but the huge expense of suitable scanning equipment puts this beyond the reach of most gout patients.

Advances in other medical imaging techniques leads to frequent reviews in professional journals. The most recent[1] of these concludes:

The diagnosis of gout is usually based on clinical presentation and laboratory findings. Imaging plays a role in the assessment and grading of articular damage related to chronic, long-standing disease, which is characterized by granulomatous synovitis, tophi, and erosions. Multimodality imaging of chronic tophaceous gout may be useful in clinical practice for a variety of purposes, including assessment of disease-related anatomical changes and monitoring of articular and soft-tissue lesions over time, especially in response to urate-lowering therapy. Radiography remains the primary imaging technique. Ultrasonography may detect monosodium urate crystals on cartilage, is helpful to assess small joint effusion, to guide to joint aspiration, and to evaluate the volume of tophi. Computed tomography is considered to be more sensitive than plain radiography in the detection and evaluation of cortical bone erosions associated with tophi. MRI represents the only imaging modality which provides visualization of bone marrow oedema associated with erosions and may be useful to characterize and distinguish tophi from other soft tissue nodules.

Unfortunately the full report is in Italian, and impossible for me to understand. However, an earlier review[2] shows similar findings, and so we can see how different technologies play their part in allowing us to see uric acid crystals (or not).

X-ray

Uric acid crystals will not show on x-rays. However, they do show joint damage where gout has eaten into the bone. Unfortunately, this is too late to prevent that damage.

Ultrasound

The relatively low cost, and high availability, of ultrasound makes it the most reliable tool for measuring gout progression. It will detect deposits at quite an early stage, though it will not determine if these are uric acid crystals from gout or other deposits such as pseudogout. If there is doubt, the ultrasound can also help in positioning the rheumatologist’s needle for joint fluid analysis.

CT Scans

Computed Tomography will detect uric acid crystals at very low volumes. It also shows clearly when these deposits start growing into bone – a much earlier recognition of bone damage compared to x-ray. Though this early detection of deposits allows urate lowering treatment to start before gout causes permanent damage, the scarcity of suitable equipment limits this to the lucky few.

MRI

MRI, though not cheap, is more widely available. It will detect bone erosion earlier then x-ray, and it will detect deposits, though not what they are. The 2009 study concludes that MRI might be most useful in assessing joint problems associated with gout, whilst the later report notes that it is the only technique to show bone marrow swelling [edema].

Leave this page to browse the uric acid crystals in the Understanding Uric Acid Section

References

1. Title:

   [Multimodality imaging of chronic tophaceous gout].

   Authors:

   Paparo F, Sconfienza LM, Muda A, Denegri A, Piccazzo R, Aleo E, Cimmino MA.

   Published:

   Reumatismo. 2010 Oct-Dec;62(4):286-91.

2. Title:

   Imaging of gout: findings and utility.

   Authors:

   Perez-Ruiz F, Dalbeth N, Urresola A, de Miguel E, Schlesinger N.

   Published:

   Arthritis Res Ther. 2009;11(3):232. Epub 2009 Jun 17. Uric Acid Crystals: X-ray, Ultrasound, MRI, & CT

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Uric acid crystals must be dissolved to permanently get rid of gout pain, but how long does it take to get rid of them?

Like all gouty issues, the answer is never simple. However, we can see some factors that affect the time it takes for crystals to dissolve, and see that the time to start dissolving is now.

In an earlier article, I explained how tophi shrink quicker with lower uric acid concentrations. But this does not mean that once you lower uric acid to a safe level you will immediately stop all gout attacks. In fact, partially dissolved uric acid crystals can start a gout attack, as I explained in Allopurinol Medication: Why It Hurts To Get Rid Of Gout. Though that article looks specifically at allopurinol, the effects of dissolving uric acid crystals might occur with any urate lowering treatment, including diet, until all urate deposits dissolve. But how long does this cleansing period take?

Uric Acid Treatment Phases

Firstly, and most importantly, we have to differentiate two phases of urate lowering treatments. This distinction is not understood by all medical practitioners with the result that inadequate, ineffective dosing of allopurinol is common.

Urate Cleansing Period

The cleansing period requires uric acid levels well below 6mg/dL (0.35 mmol/L). We have already seen that faster results are obtained below this figure, so it is good to aim for 3 to 4 mg/dL (0.2-0.25 mmol/L) – your Urate Cleansing Target. During the cleansing period, your joints and other tissues still contain crystals that can cause a gout flare. Some doctors prescribe preventative (prophylactic) pain-killers such as colchicine or other anti-inflammatory pain relief.

As we will see soon, it is difficult to determine how long this cleansing phase will take, but easy to see when it has ended. Once you have gone 6 months without a gout flare, whilst maintaining your Urate Cleansing Target, and have no visible uric crystal deposits (tophi), then you are ready to start the uric acid maintenance phase.

Uric Acid Maintenance Period

Once all uric acid crystals have dissolved, the dose of allopurinol, febuxostat or other treatment can be relaxed to maintain a level around 5mg/dL (0.30 mmol/L), never rising above 6 mg/dL (0.36 mmol/L). The maintenance phase usually lasts as long as you do, but some gout sufferers are able to stop uric acid treatment completely, if only for a few months.

Even if you can stop treatment, it is vital to maintain monitoring at least once, preferably twice, every year. At the first sign of uric acid rising over 5mg/dL (0.30 mmol/L), you must recommence allopurinol, or other uric acid lowering treatment. Do not wait for a gout attack – the deposits build very slowly, and by the time you notice them you will have sufficient uric acid crystal deposits to give many more months of pain.

Length Of Urate Cleansing Period

There are many variables that determine how long it takes to dissolve all uric acid crystals.

We have already seen that lowering uric acid concentration in the blood will increase the rate at which crystals dissolve. That study[1] reports:

The mean time from onset of ULT [Urate Lowering Therapy] to disappearance of the target tophus for the entire series was 20.8 ± 10.2 months (range 6–64 months)

That study, dealing with sufferers of tophaceous gout, showed that urate clearance could take more than 5 years. A later study[2], amongst other findings concerning relationships between uric acid levels and gout attacks, shows that most gout patients who maintain uric acid levels below 6mg/dL (0.35 mmol/L) do not have gout attacks after one year. Unfortunately, the study is not directly related to the time it takes to clear urate deposits, focusing more on the occurrence of acute gout attacks.

More relevant, is Pascual & Sivera’s investigation to define the time required for the disappearance of urate crystals from gouty joints[3]. The study analyzes fluid from gouty joints in 18 gout patients who have had gout between 2 months and 40 years, with an average of 10 years. The chart above shows how uric acid lowering medicines reduce the number of gouty subjects who have uric acid crystals in their joints. Most are crystal-free within one year; all but three are crystal free within 2 years; with the final subject becoming gout free within 3 years. The authors note that:

The time required for crystal disappearance ranged from 3 to 33 months, and showed a good correlation with the time since the initial episode of gout (r_s = 0.71;p

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