The application of dual-energy computed tomography in the diagnosis of acute gouty arthritis

The aim of the study was to investigate the sensitivity and specificity of dual-energy computed tomography in the diagnosis of acute gouty arthritis, and the related risk factors for urate crystal deposition. One hundred ninety-one patients (143 with acute gouty arthritis and 48 with other arthritic conditions) were studied. All patients had acute arthritic attack in the recent 15 days and underwent dual-energy computed tomography (DECT) scan with the affected joints. The urate volume was calculated by DECT and the basic information of these patients was recorded at the same time. Uric acid crystals were identified with DECT in 140 of 143 (97.9 %) gout patients and 6 of 48 (12.5 %) of nongout patients, respectively. The sensitivity, specificity, positive predictive value, and negative predictive value of DECT in the diagnosis of acute gouty arthritis were 97.9, 87.5, 95.9, and 93.3 %, respectively. The urate volumes were ranged from 0.57 to 54,543.27 mm³ with a mean volume of 1,787.81?±?7,181.54 mm³. Interestingly, urate volume was correlated with the disease duration, serum uric acid levels, the presence of tophi, and bone erosion. Two-year follow-up data was available in one patient with recurrent gouty arthritis, whose urate volume was gradually reduced in size by DECT detection after urate-lowering therapies. DECT showed high sensitivity and specificity for the identification of urate crystals and diagnosis of acute gout. The risk factors for uric acid deposition include the disease duration, serum uric acid levels, the presence of tophi, and bone erosion. DECT has an important role in the differential diagnosis of arthritis, and also could be served as a follow-up tool.     

Prevalence of monosodium urate deposits in a population of rheumatoid arthritis patients with hyperuricemia

ObjectivesTo investigate the prevalence of monosodium urate (MSU) crystal deposits, indicative for gout, in a population of rheumatoid arthritis (RA) patients with concomitant hyperuricemia and to analyze the clinical and disease-specific characteristics of RA patients who exhibit MSU crystal deposits.MethodsOverall, 100 consecutive patients with the diagnosis of RA and a serum urate level above 6 mg/dl underwent dual energy computed tomography (DECT) of both feet and hands to search for MSU crystals in a prospective study between October 2011 and July 2013. Presence and extent of MSU crystal deposits on DECT was assessed by automated volume measurement. Demographic and disease-specific characteristics were recorded and included into two logistic regression models to test for the factors associated with MSU crystal deposits in RA.ResultsHyperuricemic RA patients were mostly male (55%), over 60 years of age (63 ± 11 years), had established disease (8.7 ± 10.5 years) and a mean disease activity score 28 (DAS 28) of 3.2. In total, 20 out of 100 patients displayed MSU crystal deposits in DECT. Interestingly, the majority (70%) of the RA patients positive for MSU crystal deposits were seronegative RA patients. Hence, every third seronegative RA patient had MSU crystal deposits. According to logistic regression model analysis, seronegative status correlated positively with presence of urate deposits (p = 0.019).ConclusionsThese data show that a considerable number of RA patients display periarticular MSU crystal deposits. Seronegative patients were shown to be predominantly affected with every third patient being positive for urate deposits.     

Prediction of renal and cardiometabolic outcomes in gout during urate-lowering therapy by sonography

Objectives

To assess whether the extent of monosodium urate (MSU) crystal deposition estimated by ultrasound could predict renal and cardiometabolic events during urate-lowering therapy (ULT).

Methods

A prospective study on gout patients from two referral centers initiating ULT who underwent baseline ultrasound and were followed for 1 year. Ultrasound scans assessed six joints for double-contour (DC) signs and tophi. A five-point change (mL/min/1.73 m²) in the glomerular filtration rate at month 12 (M12) was considered significant. Outcomes of interest were renal function degraded versus improved and a composite cardiometabolic outcome (new hypertension, diabetes, atherosclerotic disease, and cardiovascular death). Homogeneity analyses and Cox regression models were performed.

Results

One hundred sixty patients were recruited. At baseline, 81.1% of patients (n = 129) showed sonographic tophi with a mean number of 1.4 joints (±1.3) with a DC sign. At M12, 18 patients (11.3%) were lost to follow-up. The serum urate (SU) target (<6.0 mg/dL) was reached in 86 patients (69.9%). Regarding renal function, 15.9% of patients showed improvement, while in 31.0% it degraded. Fourteen new cardiometabolic events occurred in 12 patients. Neither the DC sign nor tophi showed any significant impact on the outcomes of interest. Baseline SU level was higher in those with renal improvement but not with renal decline, while achieving the SU target protected against new cardiometabolic events (HR = 0.2; 95% CI: 0.05–0.81).

Conclusions

Sonographic MSU crystal burden was unhelpful in predicting renal and cardiometabolic events during the first year of ULT. Reaching the SU target prevented cardiometabolic events, while its benefit in preserving/improving renal function is unclear.     

Imaging of gout: New tools and biomarkers?

While joint aspiration and crystal identification by polarizing microscopy remain the gold standard for diagnosing tophaceous gout, agreement among medical and ancillary health personnel examining synovial fluid using polarizing microscopy for the detection of monosodium urate (MSU) crystals appears to be poor. Imaging modalities, including conventional radiography (CR), ultrasonography (US), magnetic resonance imaging (MRI), and dual-energy computed tomography (DECT), have been found to provide information on the deposition of MSU crystals in tissues, and the consequences of such deposition. CR can demonstrate typical “punched out lesions” with marginal overhangs, but the sensitivity for erosion detection is better for DECT and US. US is inexpensive and can identify tophus deposition in and around joints, erosions, and tissue inflammation if power Doppler US is used. MRI can show tophi, bone marrow edema, and inflammation, but MRI findings of tophi may be nonspecific. DECT can identify and color-code tophaceous material, and provide an overview of the tophus burden of a joint area. Because of the lower number of available studies, the strength of evidence for the newer imaging can be improved through further research.     

New gout test: enhanced ex vivo cytokine production from PBMCS in common gout patients and a gout patient with Kearns-Sayre syndrome

Monosodium urate (MSU) monohydrate crystals synergize with various toll-like receptor (TLR) ligands to induce interleukin-(IL)-1β production. Data are shown from a young male with mitochondriopathy in Kearns-Sayre syndrome (KSS) who developed gout and underwent urate-lowering therapy (ULT) versus a group of common gout patients. Peripheral blood mononuclear cells (PBMCs) are exposed in vitro to MSU crystals in the presence/absence of TLR2 ligands palmitic acid (C16:0) or palmitoyl-3-cysteine (Pam3Cys); proinflammatory cytokine production (IL-1β, IL-6, IL-8) is assessed by specific ELISA’s. MSU crystals alone failed to induce IL-1beta, IL-6, or IL-8 in both the KSS patient and gout controls. A strong synergy between MSU crystals and C16:0 or Pam3Cys for induction of IL-1 beta/IL-6 is found in gout patients, but in gout with KSS, we found even more response than in control gout patients. Pam3Cys exposure reveals an enhanced response in cells originating from the KSS patient, indicating a high producer phenotype in response to TLR2 stimulation. During ULT, serum urate levels dropped in the KSS case. The hyperresponse of TLR2 may be secondary to the high serum urate concentration of 0.92 mmol/l that was initially found in circulation in vivo. Within a 6-month period, the serum urate concentration dropped, and the in vitro stimulation tests improved but did not fully normalize yet. The ex vivo cytokine production in gout patients is promising a novel gout test; PBMCs’ responses in the mitochondriopathic gout patient is enhanced when compared with common gout patients, indicating a supersensitive gout patient profile. The non-inflammatory presentation in the KSS case with bulky gout is due to less inflammatory MSU crystals, i.e., specific crystal stereochemical/conformational properties. For developing gout attacks, the serum urate level and specific crystal properties both are of importance. Key Messages 1. Ex vivo cell tests are promising to serve as a novel gout lab test for screening purposes. 2. Ex vivo cellular responses are reduced following intraarticular glucocorticoid injection and/or urate-lowering therapy. 3. Crystal conformation properties play a role in the inflammatory in vivo and ex vivo response in gout. 4. A young male with Kearns-Sayre syndrome is described with less pronounced inflammatory PMBC responses to his own MSU crystals which explains the advanced stage of urate accumulation in this individual.     

Treatment of hyperuricemia, gout and other crystalline arthritidies

Gout is a very common joint disease which is due to chronic hyperuricemia and its related articular involvements. Yet it can be cured when appropriately managed. Comprehensive management of gout involves correct identification and addressing all causes of hyperuricemia, treating and preventing attacks of gouty inflammation (using colchicine NSAIDs, and/or steroids), and lowering serum urate (SUA) to an appropriate target level indefinitely. The ideal SUA target is, at a minimum, less than 6 mg/dL (60 mg/L or 360 μmol/L), or even less than 5 mg/dL in patients with tophi. The SUA target should remain at less than 6 mg/dL for long in all gout patients, especially until tophi have resolved. Patient education and adherence to therapy are key point to the optimal management of gout, aspects which are often neglected. Adherence can be monitored in part by continuing, regular assessment of the SUA level. More difficult cases of gout often need a combination of urate lowering therapy (ULT) for both refractory hyperuricemia and chronic tophaceous arthritis. Chronic tophaceous gouty arthropathy which do not respond adequately to optimized oral ULT might benefit from the use of pegloticase, when this is available in, for example, Italy and other European countries. By contrast, in calcium pyrophosphate (CPP) crystal deposition disease (CPPD), as evidenced by pseudo gout attacks or chronic polyarthritis, similar anti-inflammatory strategies have been recommended, but there have as yet been no controlled trials. Of note, there is no treatment for the underlying metabolic disorders able to control the CPPD. Management of crystal-induced arthropathies (CIA) depends not only on clinical expression, namely acute attacks or chronic arthropathy, but also on the underlying metabolic disorder. We will mainly focus on gout as an archetype of CIA.     

Imaging of tophaceous gout: computed tomography provides specific images compared with magnetic resonance imaging and ultrasonography

OBJECTIVE: To determine the usefulness of computed tomography (CT), magnetic resonance imaging (MRI), and Doppler ultrasonography (US) in providing specific images of gouty tophi. METHODS: Four male patients with chronic gout with tophi affecting the knee joints (three cases) or the olecranon processes of the elbows (one case) were assessed. Crystallographic analyses of the synovial fluid or tissue aspirates of the areas of interest were made with polarising light microscopy, alizarin red staining, and x ray diffraction. CT was performed with a GE scanner, MR imaging was obtained with a 1.5 T Magneton (Siemens), and ultrasonography with colour Doppler was carried out by standard technique. RESULTS: Crystallographic analyses showed monosodium urate (MSU) crystals in the specimens of the four patients; hydroxyapatite and calcium pyrophosphate dihydrate (CPPD) crystals were not found. A diffuse soft tissue thickening was seen on plain radiographs but no calcifications or ossifications of the tophi. CT disclosed lesions containing round and oval opacities, with a mean density of about 160 Hounsfield units (HU). With MRI, lesions were of low to intermediate signal intensity on T(1) and T(2) weighting. After contrast injection in two cases, enhancement of the tophus was seen in one. Colour Doppler US showed the tophi to be hypoechogenic with peripheral increase of the blood flow in three cases. CONCLUSION: The MR and colour Doppler US images showed the tophi as masses surrounded by a hypervascular area, which cannot be considered as specific for gout. But on CT images, masses of about 160 HU density were clearly seen, which correspond to MSU crystal deposits.     

Temporal evolution of urate crystal deposition over articular cartilage after successful urate-lowering therapy in patients with gout: An ultrasonographic perspective

Objective: To detect evolution of ultrasonographic signs of deposition of monosodium urate crystals (MSUC) in gouty joints by serial ultrasonography after initiation of urate-lowering therapy (ULT).

Methods: Adult gout patients were examined by serial ultrasonography after initiation of ULT with target serum uric acid (SUA) Results: Thirty-eight male patients with gout with mean age of 50?±?11?years, median disease duration of 48 months and baseline mean SUA level of 8.8?±?1.5?mg/dL were recruited. Ultrasonographic evidence of MSUC deposition was detected in 89.74% of first metatarsophalangeal (MTP) joints and 27.63% of knee joints. Double contour sign (DCS), tophi, and hyperechoic spots (HES) were detected in 77.63%, 43.42%, and 19.74% of first MTPs, respectively. SUA level normalizes and plateaus after fourth month of follow-up. DCS thickness reduced significantly throughout the follow-up period. Overall, 86.25% DCS and 100% HES disappeared with median time of 6 months and 5.7 months, respectively. SUA normalization was the only significant predictor of DCS disappearance.

Conclusions: Serial ultrasonographic determination of DCS, tophi, or HES during hypouricemic therapy is a noninvasive, effective method to detect the lowering of burden of urate load in gouty joints.     

CaseBook Consults: Improving Outcomes in Gout (Multimedia Activity)

Gout is a chronic, potentially debilitating condition characterized by an inflammatory process in the joints or periarticular tissues that results from the deposition of monosodium urate crystals. Underdiagnosis and undertreatment can lead to the development of tophi and chronic arthropathy. A presumptive diagnosis of gout can be made on the basis of the clinical presentation as well as risk factors such as metabolic syndrome. Key conditions to rule out in the differential diagnosis are septic arthritis, calcium pyrophosphate deposition disease (pseudogout), fracture, and rheumatoid arthritis. Acute flares of gout should be managed with nonsteroidal antiinflammatory drugs (NSAIDs), colchicine, or corticosteroids. With a diagnosis of gout, if urate-lowering therapy (ULT) is required, prophylaxis should be considered with low-dose colchicine or an NSAID, followed by the addition of ULT. The goal of ULT is to reach a serum uric acid (SUA) level ≤6.0 mg/dL. Measurements of SUA should be obtained after resolution of an acute attack, then periodically to facilitate titration of the ULT dose to achieve the target SUA level. Studies have confirmed significant reductions in gout attacks among patients who have attained SUA levels ≤6.0 mg/dL with ULT. Patient education concerning the disease and its treatment is essential to ensure close adherence with recommended therapies. Patients should also understand that ULT is intended as long-term, and for most patients, lifelong therapy to maximize the prospects for control of the disease. Clinicians should feel confident in making a presumptive diagnosis and choosing a therapeutic regimen for gout while effectively communicating with and educating patients about their disease.     

Role of Ultrasound and Other Advanced Imaging in the Diagnosis and Management of Gout

Imaging of gout with conventional radiography has been described since shortly after roentgenography was invented. Ultrasound (US) detects more erosions than conventional radiography in rheumatoid arthritis, and the same seems to be true for gout. MRI is being used to assess articular and periarticular masses, including gouty tophi. However, MRI findings in gout can lack specificity. Monosodium urate (MSU) tophi are very echogenic when US is used. Typical US features of gout include a double-contour sign or “urate icing.” The double-contour consists of the hyperechoic bony contour and a parallel hyperechoic line of MSU crystals that deposit on the hypoechoic or anechoic hyaline cartilage. Tophi can have a “wet clumps of sugar” appearance, often surrounded by an anechoic halo. Tophi are closely related to the formation of erosions. If serum urate levels are lowered consistently below 6.0 mg/dL, the disappearance of MSU crystals can be observed sonographically.     

Global patterns of treat-to-serum urate target care for gout: Systematic review and meta-analysis

BackgroundInternational rheumatology guidelines advocate a treat to serum urate target (T2T) approach for gout management. While individual studies have reported regional and national-level gout management, global patterns in gout care have not been synthesized. This study aimed to systematically review and meta-analyze global T2T care for patients with gout.MethodsElectronic databases were searched for studies reporting medication and serum urate testing in patients with gout. Meta-analyses were conducted to determine the pooled proportion of patients with gout achieving pre-specified T2T indicators.ResultsSixty-seven papers were included from North America (n = 31 studies), Europe (n = 22), Oceania (n = 7), Asia (n = 6), and reporting data from multiple continents (n = 1). The global pooled percentages (95% confidence interval (CI)) of patients with gout achieving T2T indicators were: 52% (45%, 59%) on urate lowering therapy (ULT), 50% (40%, 61%) on ULT receiving regular uninterrupted ULT, 53% (40%, 65%) on ULT having any serum urate testing, and 34% (28%, 41%) on ULT achieving a serum urate target.ConclusionOutside North America and Europe, there are relatively few studies about T2T care for gout management. However, available data demonstrate that a minority of people with gout receive T2T care worldwide. For those prescribed ULT, there are low rates of continuous therapy, serum urate testing, and achievement of serum urate target.     

Reproducibility of musculoskeletal ultrasound for determining monosodium urate deposition: concordance between readers

Objective

Criteria for sonographic diagnosis of monosodium urate (MSU) crystal deposition have been developed, but the interreader reproducibility of this modality is not well established. We therefore assessed agreement using a systematic approach.

Methods

Fifty male subjects ages 55–85 years were recruited during primary care visits to an urban Veterans Affairs hospital, and were assessed by musculoskeletal ultrasound (US) of the knees and first metatarsophalangeal (MTP) joints to evaluate for the double contour sign and tophi as evidence of MSU crystal deposition. Images were read by 2 blinded rheumatologists trained in musculoskeletal US, and the degree of concordance was determined for individual subjects, total joints, femoral articular cartilage (FAC), and first MTP joints. Subjects were further categorized into 3 diagnostic groups: gout, asymptomatic hyperuricemia (no gout, serum uric acid [UA] ≥6.9 mg/dl), and controls (no gout, serum UA ≤6.8 mg/dl), and reader concordance within these 3 groups was assessed.

Results

We observed almost perfect agreement between readers for 1) individual subjects (yes/no; n = 50, 100% agreement, κ = 1.000), 2) total joints (n = 200, 99% agreement, κ = 0.942), 3) FAC (n = 100, 99% agreement, κ = 0.942), and 4) first MTP joints (n = 100, 99% agreement, κ = 0.942). Furthermore, findings by side (right/left) and diagnostic group (gout, asymptomatic hyperuricemia, control) showed substantial to almost perfect concordance for all measures. MSU deposition was seen most commonly in gout patients, and deposition was also seen in some subjects with asymptomatic hyperuricemia, but in only 1 control.

Conclusion

Musculoskeletal US is reliable for detecting MSU deposition in FAC and first MTP joints in gout and asymptomatic hyperuricemia.     

Gouty arthritis: decision-making following dual-energy CT scan in clinical practice,a retrospective analysis

To establish whether dual-energy CT (DECT) is a diagnostic tool, i.e., associated with initiation or discontinuation of a urate lowering drug (ULD). Secondly, to determine whether DECT results (gout deposition y/n) can be predicted by clinical and laboratory variables. Digital medical records of 147 consecutive patients with clinical suspicion of gout were analyzed retrospectively. Clinical data including medication before and after DECT, lab results, and results from diagnostic joint aspiration and DECT were collected. The relationship between DECT results and clinical and laboratory results was evaluated by univariate regression analyses; predictors showing a p?<?0.10 were entered in a multivariate logistic regression model with the DECT result as outcome variable. A backward stepwise technique was applied. After the DECT, 104 of these patients had a clinical diagnosis of gout based on the clinical judgment of the rheumatologist, and in 84 of these patients, the diagnosis was confirmed by demonstration of monosodium urate (MSU) crystals in synovial fluid (SF) or by positive DECT. After DECT, the current ULD was modified in 33 (22.4%) of patients; in 29 of them, ULD was started and in 1 it was intensified. Following DECT, the current ULD was stopped in three patients. In the multivariable regression model, cardiovascular disease (OR 3.07, 95% CI 1.26–7.47), disease duration (OR 1.008, 95% CI 1.001–1.016), frequency of attack (OR 1.23, 95% CI 1.07–1.42), and creatinine clearance (OR 2.03, 95% CI 0.91–1.00) were independently associated with positive DECT results. We found that the DECT result increases the confidence of the prescribers in their decision to initiation or discontinuation of urate lowering therapy regimen in of mono- or oligoarthritis. It may be a useful imaging tool for patients who cannot undergo joint aspiration because of contraindications or with difficult to aspirate joints, or those who refuse joint aspiration. We also suggest the use of DECT in cases where a definitive diagnosis cannot be made from signs, symptoms, and MSU analysis alone.     

Management of gout and hyperuricemia: Multidisciplinary consensus in Taiwan

Gout is an inflammatory disease manifested by the deposition of monosodium urate (MSU) crystals in joints, cartilage, synovial bursa, tendons or soft tissues. Gout is not a new disease, which was first documented nearly 5,000 years ago. The prevalence of gout has increased globally in recent years, imposing great disease burden worldwide. Moreover, gout or hyperuricemia is clearly associated with a variety of comorbidities, including cardiovascular diseases, chronic kidney disease, urolithiasis, metabolic syndrome, diabetes mellitus, thyroid dysfunction, and psoriasis. To prevent acute arthritis attacks and complications, earlier use of pharmacotherapeutic treatment should be considered, and patients with hyperuricemia and previous episodes of acute gouty arthritis should receive long‐term urate‐lowering treatment. Urate‐lowering drugs should be used during the inter‐critical and chronic stages to prevent recurrent gout attacks, which may elicit gradual resolution of tophi. The goal of urate‐lowering therapy should aim to maintain serum uric acid (sUA) level <6.0 mg/dL. For patients with tophi, the initial goal can be set at lowering sUA to <5.0 mg/dL to promote tophi dissolution. The goal of this consensus paper was to improve gout and hyperuricemia management at a more comprehensive level. The content of this consensus paper was developed based on local epidemiology and current clinical practice, as well as consensuses from two multidisciplinary meetings and recommendations from Taiwan Guideline for the Management of Gout and Hyperuricemia.     

Treatment of chronic gout. Can we determine when urate stores are depleted enough to prevent attacks of gout?

OBJECTIVE: To determine if lowering of serum uric acid (SUA) concentrations below 6 mg/dl or longer duration of lowered SUA will result in depletion of urate crystals from the knee joints and prevent further attacks of gout. METHODS: A prospective study was initiated 10 years ago at Philadelphia VA Medical Center to attempt to maintain SUA levels of patients with crystal proven gout at < 6.0 mg/dl. We recalled all 57 patients who were available during 1999. Patients were divided into 2 groups: Group A, with SUA still > 6 mg/dl, and Group B, with SUA < or = 6 mg/dl. A knee joint aspirate was requested from all asymptomatic Group B patients and many in Group A. Aspirates were examined by polarized light microscopy for identification of crystals. RESULTS: There were no differences between the groups in age, sex, duration of gout, or serum creatinine. Group A (n = 38) had a mean of 6 attacks of gout for the recent year, those with tophi having the most frequent attacks. Among the 16 patients in this group who agreed to knee aspiration, monosodium urate (MSU) crystals were found in 14, although they were asymptomatic at the time. Nineteen patients (Group B) were able to maintain serum urate levels < or = 6 mg/dl for > 12 months. Nearly half of them had no attack of gout for 2 or more years, with a mean of 1 attack in the last year for the whole group. Three patients in whom tophi were found did not have major flares of gout within the past year. Knee joint aspiration was done on 16 asymptomatic patients. Seven (44%) still had MSU crystals present in their knees. Patients in this group who were taking prophylactic colchicine did not differ with respect to the character of synovial fluid from those who had discontinued it for up to several years, although the frequency of attacks was less in those who continued colchicine. CONCLUSION: A majority of patients were able to deplete urate crystal stores in their knee joint fluids when their SUA levels were kept to < or = 6 mg/dl for several years. The mechanisms for persistence in some patients, and whether such crystals have clinical implications, are not known. Patients with chronic gout need serum urate concentrations to be kept low to prevent further attacks.     

Role of dual-energy CT in the diagnosis and follow-up of gout: systematic analysis of the literature

The aim of this systematic review was to determine the potential role of dual-energy CT in the diagnosis and follow-up of gout with regard to the Outcome Measures in Rheumatology (OMERACT) filter. A systematic analysis of the literature was conducted using the MEDLINE and Cochrane databases and published abstracts of international congresses, according to the criteria of the OMERACT filter: feasibility, reproducibility, validity versus laboratory (serum urate, MSU synovial fluid aspirate) and other imaging modalities for gout, and its sensitivity to change in patients on urate lowering therapy (ULT). Thirty-two articles were found representing a total of 1502 patients. The data on feasibility showed that the examination took little time and involved low levels of radiation but had current limited availability. Intra- and inter-observer reproducibility was excellent, with intra-class correlation coefficients >?0.9. Validity in comparison with polarized-light microscopy showed good sensitivity and specificity (>?80%). The diagnostic performance was better than that of radiography and conventional CT-scan and at least equivalent to that of ultrasonography. The sensitivity to change varied with effect sizes from 0.05 (low) to 1.24 (high) for decrease in the tophus volume following different ULT in gout patients. Dual-energy CT-scan is a reproducible and accurate imaging modality for the diagnosis of gout, particularly for tophaceous gout (intra- or extra-articular). It can become a second-line imaging modality of choice in cases of diagnostic doubt, such as ultrasonography. Its role remains uncertain in the follow-up of gout patients treated with ULT and needs further clarification.     

"Crystal clear"-sonographic assessment of gout and calcium pyrophosphate deposition disease

OBJECTIVES: To date, high-resolution ultrasound (US) has not been fully exploited in the field of crystalline arthropathy. Both gout and calcium pyrophosphate deposition (CPPD) disease are significant diseases within the purview of the rheumatologist. The aim of this pictorial review was to present the principal findings in patients with crystal deposition in gout and CPPD. METHODS: US pictures were obtained from 60 consecutive patients, 34 with CPPD disease and 26 with gout, whose diagnosis was confirmed by synovial fluid analysis. The US examinations were performed using the following US systems: Diasus (Dynamic Imaging, Livingstone, UK) and Logiq 9 (General Electric Medical Systems, Milwaukee, WI). RESULTS: Pictorial evidence of the principal US findings in gout includes monosodium urate (MSU) deposition on the surface of articular cartilage, various patterns within synovial fluid ranging from completely anechoic fluid to collections filled with aggregates of variable shape and echogenicity, microdeposition within tendons, and tophus formation. In CPPD, the hallmark US features include crystal deposition within articular cartilage, calcification of fibrocartilage, together with focal crystal deposition within tendons. CONCLUSION: US is an impressive imaging modality in crystalline arthropathy. The anatomical location of the crystal deposits, clearly depictable by US, allows differentiation between MSU and CPPD aggregates.     

Clinical features of gout

Gout is a metabolic disease characterized by hyperuricemia and the deposition of monosodium urate (MSU) crystals in the joints and soft tissues, consisting of a self-limited acute phase characterized by recurrent attacks of synovitis and a chronic phase in which inflammatory and structural changes of the joints and periarticular tissues may lead to persistent symptoms. Acute gout is characterized by a sudden monoarthritis of rapid onset, with intense pain, mostly affecting the big toe (50% of initial attacks), the foot, ankle, midtarsal, knee, wrist, finger, and elbow. Acute flares also occur in periarticular structures, including bursae and tendons. The presence of characteristic MSU crystals in the joint fluid, appearing needle-like and showing strong negative birefringence by polarized microscopy, is pivotal to confirm the diagnosis of gout. The time interval separating the first attack from subsequent episodes of acute synovitis may be widely variable, ranging from a few days to several years. During the period between acute attacks the patient is asymptomatic even if MSU deposition may continue to increase silently. The factors that control the rate, location, and degree of ongoing deposition in gouty patients are not well defined. Chronic gout is the natural evolution of untreated hyperuricemia in patients with gouty attacks followed by pain-free intercritical periods. It is characterized by the deposition of solid MSU crystal aggregates in a variety of tissues including joints, bursae and tendons. Tophi can occur in a variety of locations including the helix of the ear, olecranon bursa, and over the interphalangeal joints. Their development is usually related with both the degree and the duration of hyperuricemia. About 20% of patients with gout have urinary tract stones and can develop an interstitial urate nephropathy. There is a strong association between hyperuricaemia and the metabolic syndrome (the constellation of insulin resistance, hypertension, obesity and dyslipidaemia), and gouty patients often have a medical history of kidney disease, diabetes mellitus and signs of vascular illness such as coronary artery disease, heart failure and stroke, resulting with a poor overall quality of life.