12/24/2015    Todd Lewis, DPM

Gouty Tophus with Normal Uric Acid (Barry Mullen, DPM)

Dr. Mullen, I apologize if my message came across
as disrespectful to you and our peers. That
wasn’t my intention.

I strongly concur with your response to this
disease, and I do feel serum uric acid levels do
have merit, but aren't diagnostic. I was simply
trying to state some facts, that from my
experience, are misunderstood and/or under-
appreciated when it comes to gout and it’s not
only our profession, but all facets of medicine.

The definitive diagnosis of gout is confirmed by
the presents of needle-shaped monosodium crystals
with negative birefringence under polarized
microscopy and that a 24-hour urine uric
acid/creatinine clearance analysis helps us to
determine renal function and to better generate a
long term treatment plan with medication.

For example, in such patients, if the uric acid
excretion is less than 600-700mg/24-hours, then
Probenecid is commonly used; and if the uric acid
excretion is greater than 600-700mg/24-hours,
then Allopurinol is commonly used. These values
may vary depending on the hospital or laboratory
used. These medications are traditionally
utilized in clinical practices. Remember, if
collecting 24-hour urine for uric acid, don't
forget to also order 24-hour creatinine so
creatinine clearance can be calculated.

In addition, musculoskeletal ultrasound and dual
energy CT scan are 2 other ways to diagnosis
gout.

Musculoskeletal ultrasound can detect urate
crystals in a joint or in a tophus, "tophus Latin
meaning "stone", plural tophi" is a deposit of
uric acid crystals, in the form of monosodium
urate crystals, in people with longstanding
hyperuricemia”, this technique is more widely
used abroad than in the United States.

Dual energy CT scan is a type of imaging that can
detect the presence of urate crystals in a joint,
even when it’s not acutely inflamed. This test
isn’t used routinely in clinical practice due to
the expense and is not widely available.

Todd Lewis, DPM, Chicago, IL

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