Case 1: Adult Male with Soft Tissue

Case 1: Adult Male with Soft Tissue Swelling of Right Middle Finger
Gout is caused by genetic disposition and alimentary factors. It comprises a heterogeneous group
of disorders characterized by deposition of monosodium urate crystals in the joints and tendons.
Asymptomatic hyperuricemia is common and should not ordinarily be treated. Gout progresses
through four clinical phases: asymptomatic hyperuricemia, acute gouty arthritis, intercritical gout
(intervals between acute attacks) and chronic tophaceous gout. A combination of increased production
of uric acid and insufficient excretion causes the disease to become clinically evident. The causes are
deposits of uric acid that can be found in the distal extremities, especially adjacent to joints, primarily
in the toes but also in the fingers. The foot, heel, ankle, knee, hands, wrists and elbows are the other
joints that are frequently involved (i.e. rather peripheral joints). A familial pattern is observed in up to
15% of cases. Obesity, high blood pressure and atherosclerotic heart disease are often associated.
Gout occurs acutely as intermittent attacks of inflammatory arthritis with severe joint pain, swelling,
redness and warmth of affected joint. In 90% of initial episodes, a single joint is involved, especially
the joint at the base of the hallux. Severe attacks of joint pain can occur at any age, but the first attack
often affects men between the ages of 40 and 50. Gout occurs 20 times more frequently in men than in
women. Attacks can be triggered by alcohol, high purine food (meat, seafood, kidney), diuretic drugs or
anti-cancer chemotherapy.1, 2
Although hyperuricemia predisposes patients to gout and nephrolithiasis, it does not need to be treated
in the asymptomatic patient. However, efforts should be made to modify or correct underlying causes.
Colchicine, an antimitotic drug derived from the roots of the herb Colchicum autumnale, is one of
the oldest treatments for gout. Although colchicine is effective in treating acute gout, 80 percent
of patients experience gastrointestinal side effects, including nausea, vomiting and diarrhea, at
therapeutic dosages.
Therefore, nonsteroidal anti-inflammatory drugs are the treatment of choice for acute attacks of gout
in most patients, but should be used sparingly in elderly patients and avoided in patients with renal
disease and peptic ulcer disease. Corticosteroids are a valuable treatment option for patients in whom
non-steroidal anti-inflammatory drugs are contraindicated. Acute gouty arthritis and chronic gout require different treatment strategies. After the acute gouty attack is treated and prophylactic therapy
is initiated, the issue of ongoing urate deposition should be addressed. A common practice is not to
initiate drug therapy aimed at lowering urate levels after the initial attack. Rather, most clinicians
prefer to aggressively correct or reverse sources of hyperuricemia in hopes of lowering the serum urate
level without the use of medication.
Demonstration of intra-articular monosodium urate crystals is necessary to establish a definitive
diagnosis of gouty arthritis. Thus, a definitive diagnosis usually requires aspiration and examination
of synovial fluid to confirm the presence of monosodium urate crystals. The crystals are identified
by their characteristic birefringence under polarized light microscopy.
In cases of unclear soft tissue swelling, elevated serum levels of uric acid and response to treatment
with colchicine can support the diagnosis. Plain film radiography shows soft tissue affections
and calcium deposits in earlier stages, and chronic gout leads to asymmetrical forms of osseous
destruction.3
Spiral dual energy CT provides the unique opportunity to directly show the presence of uric acid crystals
in the tophi. Moreover, inflammation can be assessed by administering contrast material, and areas
of enhancement can also be identified by spiral dual energy CT due to the dual energy properties of
iodine. Thus, a more specific and reliable diagnosis can be made within a few minutes, including highresolution
morphology of the affected joint, depiction of inflammatory changes and visualization of
uric acid deposits in the tophi.4
As described in a recent case report, a 46-year-old male was referred for imaging of his hands to clarify
an acute inflammation with hyperemia, swelling and tenderness of his right middle finger.1
There were
several areas of painless soft tissue swelling on both hands. Known hyperuricemia was suggestive of
gout, but the inflammation of the palmar soft tissue of the right middle finger without relation to a
joint was considered less characteristic, and imaging was to rule out other causes.
Spiral dual energy CT was performed on the SOMATOM Definition at 140 and 80 kVp
tube potential
after intravenous injection of iodinated contrast material (Ultravist® 370, Bayer Schering Pharma).
The three material differentiation shows a spectral behavior characteristic for uric acid in the area of inflammation and multiple other areas of painless soft tissue swelling (encoded blue in the image).
The differentiation of iodine clearly shows the contrast enhancement in the area of inflammation
(encoded red ). Thus, the inflammatory changes could be attributed to acute gout. The diagnosis was
confirmed by response to treatment with Colchicine. The patient received appropriate medication and
dietary advice and is now scheduled for surgical resection of the gout tophi.
This case shows the ability of spiral dual energy CT to enhance the diagnostic value of computed
tomography, not mainly by increasing its spatial resolution or its soft tissue contrast but by adding
a higher specificity to the obtained information. Depending on the further development of the
technique and ongoing research, it is conceivable that other substances which represent markers
for a certain diseases can be differentiated and detected due to their spectral properties. Then, other
dual energy protocols can offer more specific diagnostic information as well as a direct and precise
assessment of the disease with diagnostic certainty and high resolution morphology, replacing the
current, merely morphology-based diagnostic reading in CT.