Introduction
Background
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Table
| Clinical Image Atlas Click to view clinical images on the features, causes, epidemiology, diagnosis, and treatment of Gout. |
| Clinical Image Atlas Click to view clinical images on the features, causes, epidemiology, diagnosis, and treatment of Gout. |
Gout is defined as a peripheral arthritis that results from the deposition of sodium urate crystals in one or more joints.1,2,3,4,5,6,7,8
Although gout has many contributing factors, 2 main processes are9 involved in its development: the overproduction of uric acid and the underexcretion of uric acid. A variety of conditions, including renal disease, have been implicated as causes of gout, but the vast majority of cases are idiopathic. Podagra, or pain in the first metatarsophalangeal joint, is the classic presentation of gout. In general, the symptoms of gout suddenly appear at night and occur in men with hyperuricemia who are aged 30-60 years.
Early radiologic findings in gout are limited to the soft tissues and involve asymmetric swelling in the affected joints. In the intermediate stage of disease, gout causes subtle changes in the bony structures on plain-film radiographs. In the periphery of affected joints, small punched-out lesions arise; obtaining 2 views is important to appreciate these subtle findings. The hallmark sign of late-phase gout is the appearance of large and numerous interosseous tophi on plain-film radiographs. Joint-space narrowing is also prominent in late-phase gout. (Also see the other eMedicine topics Gout, in Rheumatology, and Gout and Pseudogout, in Emergency Medicine.)
Recent studies
Choi et al evaluated the use of dual-energy CT scanning (DECT) to assess urate deposits in 20 patients with tophaceous gout and computerized quantification of tophus volume in peripheral joints. The study findings showed that DECT scans can produce obvious color displays for urate deposits and help identify subclinical tophus deposits and that tophus volume can be measured by DECT scans through automated volume estimation.6
Rettenbacher et al compared radiography with ultrasonography in diagnosing gout. In a prospective study, 105 consecutive patients with clinical suspicion of gout underwent conventional radiography and high-resolution US in order to help determine a definite diagnosis. Radiography suggested gout with a sensitivity of 31% (32/102) and a specificity of 93% (55/59), whereas US suggested gout with a sensitivity of 96% (98/102) and a specificity of 73% (43/59). Ultrasonography, according to the authors, often provided additional diagnostic information in patients with clinical suspicion of gout when laboratory findings and radiographic results were negative or inconclusive and should therefore be used in such cases.7
For excellent patient education resources, visit eMedicine's Arthritis Center and Kidneys and Urinary System Center. Also, see eMedicine's patient education article Gout.
Pathophysiology
Gout is a disease process that results from a central metabolic abnormality, namely, hyperuricemia. In the early stages of the disease, acute attacks of gouty arthritis occur. As gout progresses, chronic arthritis develops, and the hallmark finding of tophi in the affected joint spaces appears.
Primary gout that is due to an inborn error of metabolism accounts for about 90% of cases of the disease, and approximately 10% of cases are due to secondary gout.1,2,3 In 85-90% of cases of primary gout, the enzyme defect that is responsible for hyperuricemia is unknown. Common causes of secondary gout include renal disease, conditions with increased nucleic-acid turnover, and inborn errors of metabolism.
According to some estimates, gout develops in less than 5% of people with hyperuricemia. This finding leads to the question about why some affected individuals have gout and others do not. Several factors are believed to predispose individuals to gout, including genetic predisposition, alcohol abuse, obesity, the use of pharmacologic agents, age, and the duration of hyperuricemia.
Frequency
United States
Gout affects less than 0.5% of the population; however, the incidence is 6-80% in affected families.
Mortality/Morbidity
Untreated gout can cause significant joint pain of a progressive yet episodic nature. Commonly affected areas are the feet, ankles, knees, hands, wrists, and elbows. Other joints are less frequently affected, but their involvement can also cause significant pain and discomfort. As the disease progresses, severe damage to cartilage impairs the function of the affected joints. Gout can also cause a condition known as gouty nephropathy in which monosodium urate crystals and free uric acid crystals impair renal function. As a result, conditions such as pyelonephritis and urinary obstruction may develop.
Race
Gout is most common in Pacific Islanders, such as the Maori of New Zealand and natives of the Mariana Islands. Gout is less common in blacks than in whites.
Sex
Idiopathic gout occurs approximately 20 times more often in men than in women.
Age
Gout is more common in older individuals because this condition generally appears only after 20-30 years of hyperuricemia.
Anatomy
Gout most commonly affects joints in the feet, ankles, hands, wrists, elbows, and knees. Less commonly affected areas include the sacroiliac, sternoclavicular, and shoulder joints. Gout rarely affects the hip and spine. The kidneys are a systemic area of involvement as a result of crystal deposition, with resulting sequelae.
Presentation
The classic presentation of podagra is only one of the many presentations of gout. Acute gout causes short episodes of acute arthritis in varying joints (see Anatomy). Chronic gout, however, leads to more frequent and severe attacks of gouty arthritis, as well as the deposition of urates in joints, which creates tophi. Also, most patients with chronic gout have urate nephropathy, with complications such as pyelonephritis and urinary obstruction.
Factors in the patient's history that suggest gout include older age, male sex, Pacific Islander race, genetic predisposition, obesity, the use of thiazide diuretics, lead toxicity, and heavy alcohol consumption.
Preferred Examination
A detailed medical history is important in the initial examination of the patient who has symptoms that are consistent with those of gouty arthritis. In the initial evaluation for suspected gout, a thorough physical examination of the musculoskeletal system, with a focus on commonly affected joints, should be performed.
Plain-film radiography may be used to evaluate gout; however, radiographic findings generally do not appear until after at least 1 year of uncontrolled disease. Bone scanning may also be used to examine gout; the key finding on bone scans is an increased radionuclide concentration at the affected sites.10
The criterion standard in the diagnosis of gout is the analysis of synovial fluid samples that are obtained with aspiration. Wet mounts of the synovial fluid reveal negatively birefringent urate crystals. Also, the synovial fluid usually reveals an inflammatory process, with a white blood cell count in the range of 7,000-10,000 x 103 per mL.
Limitations of Techniques
In general, plain-film radiography is useful in the evaluation of gout only after at least 1 year of uncontrolled disease. Computed tomography (CT) scanning is often used to follow up the development of gout in areas that are difficult to assess; however, this modality is generally not used as a screening examination for the disease. Magnetic resonance imaging (MRI) has not been extensively studied with regard to its benefit in the evaluation of gout; however, MRI may have promise in the study of this disease.
Differential Diagnoses
| Abdominal Aortic Aneurysm, Diagnosis | Rheumatoid Arthritis, Hands |
| Calcium Pyrophosphate Deposition Disease | Septic Arthritis |
| Osteoarthritis, Primary | |
| Psoriatic Arthritis | |
| Reactive Arthritis, Musculoskeletal |
Other Problems to Be Considered
Pseudogout is caused by the deposition of calcium pyrophosphate deposition rather than the deposition of uric acid derivatives that cause gout (see eMedicine topics Gout and Pseudogout and Calcium Pyrophosphate Deposition Disease). In addition, the synovial fluid samples that are obtained with aspiration have positive birefringence in pseudogout; this finding is in direct contrast to the negative birefringence in gout.
In cases of infectious arthritis, cultures of synovial fluid can be helpful in differentiating this condition from gout.
In cases of amyloidosis, amyloid shows apple-green birefringence under polarized light with Congo red staining (see eMedicine topic Amyloidosis, Overview).
In cases of hyperparathyroidism, helpful diagnostic features include increased serum calcium levels, increased serum parathyroid hormone (PTH) levels, and low serum phosphate levels (see eMedicine topic Hyperparathyroidism, Primary).
Spondyloarthropathy involves a variety of presentations. The most common symptoms relate to inflammatory back pain and symptoms of inflamed peripheral joints.
Rheumatoid arthritis (RA) typically causes morning stiffness, unlike the sudden-onset of night pain that is associated with acute episodes of gout. A rheumatoid factor (RF) level of more than 1:80, which is present in 70-80% of cases of RA, can also help in differentiating this condition from gout (see eMedicine topic Rheumatoid Arthritis).
More on Gout |
 Overview: Gout |
| Imaging: Gout |
| Follow-up: Gout |
| Multimedia: Gout |
| References |
| Further Reading |
| Next Page » |
References
Dambro MR, ed. Griffith's 5-Minute Clinical Consult: A Reference for Clinicians. 9th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2001.
Resnick D. Diagnosis of Bone and Joint Disorders. Vol 3. 3rd ed. Philadelphia, Pa: WB Saunders Co; 1995:1511-39.
Cotran RS, Robbins SL, Kumar V, Schoen FJ, eds. Robbins Pathologic Basis of Disease. 5th ed. Philadelphia, Pa: WB Saunders Co; 1994:1255-8.
Dalbeth N, McQueen FM. Use of imaging to evaluate gout and other crystal deposition disorders. Curr Opin Rheumatol. Mar 2009;21(2):124-31. [Medline].
Perez-Ruiz F, Dalbeth N, Urresola A, de Miguel E, Schlesinger N. Gout. Imaging of gout: findings and utility. Arthritis Res Ther. 2009;11(3):232. [Medline].
Choi HK, Al-Arfaj A, Eftekhari A, Munk PL, Shojania K, Reid G, et al. Dual Energy Computed Tomography in tophaceous gout. Ann Rheum Dis. Dec 9 2008;[Medline].
Rettenbacher T, Ennemoser S, Weirich H, Ulmer H, Hartig F, Klotz W, et al. Diagnostic imaging of gout: comparison of high-resolution US versus conventional X-ray. Eur Radiol. Mar 2008;18(3):621-30. [Medline].
Dalbeth N, Clark B, Gregory K, Gamble G, Sheehan T, Doyle A, et al. Mechanisms of bone erosion in gout: a quantitative analysis using plain radiography and computed tomography. Ann Rheum Dis. Aug 2009;68(8):1290-5. [Medline].
Tavaras JM, Ferrucci JT Jr, eds. Radiology: Diagnosis, Imaging, Intervention. Philadelphia, Pa: JB Lippincott Co; 1993.
Coombs RJ, Pinsky ST, Padanilam TG. Bone scan findings of combined gout and septic arthritis in the same digit. Clin Nucl Med. May 2001;26(5):442-3. [Medline].
Perez-Ruiz F, Martin I, Canteli B. Ultrasonographic measurement of tophi as an outcome measure for chronic gout. J Rheumatol. Sep 2007;34(9):1888-93. [Medline].
Gentili A. The advanced imaging of gouty tophi. Curr Rheumatol Rep. Jun 2006;8(3):231-5. [Medline].
Perez-Ruiz F, Naredo E. Imaging modalities and monitoring measures of gout. Curr Opin Rheumatol. Mar 2007;19(2):128-33. [Medline].
Further Reading
Related eMedicine topics
Gout and Pseudogout
Gout (Ophthalmology)
Gout (Orthopedic Surgery)
Gout (Rheumatology)
Keywords
peripheral arthritis, sodium urate crystals, podagra, hyperuricemia, primary gout, secondary gout, intermediate gout, late-phase gout, pseudogout, tophi, gouty nephropathy, gouty arthritis, first metatarsophalangeal joint pain, probenecid, colchicine, allopurinol, indomethacin
