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Clinical investigation of synovial fluid

  • Clinical investigation of synovial fluid

    A general clinical study of fluid from a joint involves the determination of the physico-chemical properties of the fluid and the microscopic examination of cellular elements. The reference values ​​of synovial fluid are presented in the table.

    Table Synovial fluid reference values ​​

    Table Synovial fluid reference values ​​

    Synovial fluid research plays an important role in elucidating the nature of the process in the affected joint. Indications for joint puncture: monoarthritis of unclear etiology, unpleasant sensations in the affected joint( with established diagnosis), the need to monitor the effectiveness of treatment for infectious arthritis, for the differential diagnosis of arthritis and arthrosis, as this determines the choice of the program for further examination and treatment of the patient. The parameters of synovial fluid for arthritis and arthrosis are presented in the table.

    Table Changes in synovial fluid in arthritis and arthrosis

    Table Changes in synovial fluid in arthritis and arthrosis

    In clinical practice, the most common lesion of joints is detected in the following diseases.

    Infectious arthritis is divided into gonococcal( arising from dissemination of gonococcal infection) and non-gonococcal - most commonly caused by Staphylococcus aureus( 70% of cases) and Streptococcus, as well as in many viral infections( especially rubella, infectious parotitis, infectious mononucleosis, hepatitis) and Lymedisease caused by spirochetes Borrelia burgdorferi, transmitted by tick bites. Septic arthritis can cause fungi and mycobacteria.

    Synoviitis caused by crystals. The deposition of crystals in joints or periarticular tissues underlies gout, pseudogout and apatite disease. For the diagnosis of gout and pseudogout, a polarization microscopy of the precipitate obtained by centrifuging the synovial fluid is carried out. Use a polarizing microscope with a red filter. Needle crystals of urate, characteristic of gout, glow yellow( if their long axis is parallel to the axis of the compensator) and have a strong negative birefringence. They are found in both synovial fluid and neutrophils. Crystals of calcium pyrophosphate dihydrate, detected in pseudogout, have a variety of shapes( more often diamond-shaped), glow with blue light and are characterized by a weak positive birefringence

    .Complexes containing hydroxyapatite( specific for apatite disease), as well as complexes containing basic calcium and phosphorus salts, can be detected only by electron microscopy. It should be emphasized that hyperuricemia should not be considered a specific sign of gout, and calcification of joints is a pseudogout, in any case, a study by polarization microscopy is necessary to confirm the diagnosis.

    Rheumatoid arthritis. With a clear predominance of inflammation of one joint, synovial fluid should be investigated to exclude the infectious genesis of its origin, since rheumatoid arthritis predisposes to infectious arthritis.

    Spondyloarthropathies. This group includes a number of diseases that are characterized by asymmetric oligoarthritis. Investigation of synovial fluid is performed to exclude septic arthritis. Allocate the following spondyloarthropathies.

    ■ Ankylosing spondylitis. Of the peripheral joints, the hip and shoulder are more often affected.

    ■ Arthritis in inflammatory bowel diseases: 10-20% of patients suffering from Crohn's disease and ulcerative colitis develop joint damage, especially knee and ankle attacks.

    ■ Reiter's syndrome and reactive arthritis that develop after urogenital or intestinal infections.

    ■ Psoriatic arthritis develops in 7% of patients with psoriasis.

    SLE.Changes in articular fluid can be both non-inflammatory( arthrosis) and inflammatory( arthritis).

    Osteoarthrosis is a degenerative joint disease, characterized by "wear" of the articular cartilage with subsequent bone growth along the edges of the articular surfaces.

    Changes in synovial fluid in various pathological processes are reflected in the table.

    The most pronounced changes in the synovial fluid are found in bacterial arthritis. Externally the synovial fluid can have the form of pus;the cell content reaches 50,000-100,000 in 1 μl, of which neutrophils constitute more than 80%.Sometimes in the first 24-48 h of acute arthritis the number of cellular elements may be less than 25,000 in 1 μl.

    In patients with rheumatoid arthritis , the study of synovial fluid is important to confirm the diagnosis and determine the local activity of the inflammatory process. In rheumatoid arthritis, the number of leukocytes in the synovial fluid rises to 25,000 in 1 μl due to neutrophils( 25-90%), the protein content reaches 40-60 g / l. In the cytoplasm of leukocytes, inclusions, vacuoles, similar to a brush of grapes( ragocytes) are found. These cells contain phagocytized material - lipid or protein substances, rheumatoid factor, immune complexes, complement. Ragocytes are also found in other diseases - rheumatic, psoriatic, arthritis, SLE, bacterial arthritis, gout, but not in the same amount as with rheumatoid arthritis.

    Table Changes in synovial fluid in various pathological processes

    Table Changes in synovial fluid in various pathological processes

    Monitoring of the efficacy of treatment based on synovial fluid results is indicated for infectious arthritis.