BODY FLUIDS: SYNOVIAL FLUID, TRANSUDATES AND EXUDATES
Transudate: Fluid inside the cells, such as seen in edema/swelling, pulmonary edema, allergic reactions, etc...Clear fluids, but an increase of them; Some of them may be bloody Exudate: Fluid in-between the cells, such as pus, which is a combination of bacteria, white blood cells, and cellular debris, which may or may not be bloody and/or more viscious
Examples of Transudates:
Transudates are fluids that are extravascular and they have a low specific gravity and low protein content. These fluids are typically clear. Ultrafiltrates of plasma are examples of transudates. Transudates form when there is an increase in hydrostatic pressure and a decrease in colloidal osmotic pressure. Levels of lactate dehydrogenase are low (<0.6 ). These are seen in conditions such as left ventricular heart failure with formation of pulmonary edema or pulmonary effusion, liver cirrhosis and ascites, nephrotic syndrome, and severe malnutrition.
Edema/Swelling (Pitting Edema)
Pulmonary Edema (associated with left ventricular heart failure)
Cerebrospinal Fluid (CSF)
CSF (cerebral spinal fluid) collected in 4 vials, and all 4 appear clear
Examples of Exudates:
Exudates are cloudy or turbid fluids associated with inflammatory-increased vascular permeability. They have an increased protein content, increased specific gravity, cholesterol content and LDH. It includes cell debris, pus, white blood cells, and bacteria. Fluids are often yellowish, greenish, cloudy or milky, and somewhat thicker or more viscous than a transudate. These indicate inflammation or infection.
Pyuria: Pus in the Urine
Septic Arthritis (Exudate with Pus)
Synovial Joint Fluid:
Synovial fluid is found in the cavities of joints to provide lubrication for joint movement and protection of the joint. It protects and cushions the articular cartilage during movement. The synovial membrane synovial cells secrete the joint fluid into the joint cavities. The joint fluid composition includes hyaluronan, lubrican, and interstitial fluid, which is an ultrafiltrate of plasma.
Synovial fluid reduces friction, acts as a cushion, absorbs shock, supplies oxygen and nutrients to the joint structures, removes toxins and CO2 from the joint structures, and provides a barrier for cells entering or exiting the joint space. It also aids in the regulation of synovial cell growth. It contains phagocytic cells that perform cellular "housekeeping" and remove cell debris and microbes within the joint space.
Synovial fluid is removed from the joint by a procedure called arthrocentesis, in which a needle is used to aspirate the fluid from the joint. The fluid collected is classified as normal/clear, noninflammatory, inflammatory/may be thick, cloudy or viscous, septic/cloudy and discolored, and hemorrhagic/bloody. It is important to document the appearance and volume of synovial fluid sent to the laboratory for analysis to aid in the patient's diagnosis.
The following chart is useful for laboratory purposes:
Classification of synovial fluid in an adult knee joint: Normal Noninflammatory Inflammatory Septic Hemorrhagic Volume (ml) <3.5 >3.5 >3.5 >3.5 >3.5 Viscosity High High Low Mixed Low Clarity Clear Clear Cloudy Opaque Mixed Color Colorless/straw Straw/yellow Yellow Mixed Red WBC/mm3 <200 <2,000 5,00-75,000 >50,000Similar to blood level Polys (%) <25 <2550-70>70 Similar to blood level Gram stain Negative Negative Negative Often Positive Negative
EXAMPLES OF CONDITIONS:
1) NORMAL FLUID VISCOSITY: -Traumatic arthritis -Degenerative/Osteoarthritis -Synovitis
2) NORMAL OR DECREASED VISCOSITY: -Systemic lupus erythematosus
HEMORRHAGIC: -Trauma -Tumors/Cancers -Hemophilia -Scurvy -Ehlers-Danlos Syndrome -Synovitis -Neuropathic arthropathy (commonly seen in Diabetic patients)
A knee joint showing the ends of bones covered with articular cartilage, the synovial membrane, articular capsule, and joint cavity containing synovial fluid.
When knee injuries occur, the joint becomes inflamed and may need to be repaired through arthroscopy or surgery, in which the device is inserted into the joint capsule itself.
Knee surgery and arthroscopy can predispose an individual to infection if skin bacteria get into the wound. Synovial fluid can be withdrawn through a needle and sent to Microbiology and UBFL for analysis.
Inflammatory Arthritis
Inflammatory arthritis synovial fluid is typically cloudy and yellow, although, as seen in the image below, may be red and slightly bloody due to a traumatic collection.
Septic arthritis will produce joint fluid that is green-to-yellow in color due to pus (cellular debris, monocytes, neutrophils, and bacteria). It is also cloudy.
Osteoarthritis
Osteoarthritis, or OA, is a degenerative joint disease that attacks the joints. It occurs when cartilage breaks down and bones become fragile and prone to breakage as well. Joint pain (aching and burning), stiffness, inflammation, swelling, decreased range of motion, weakness, numbness and tingling, and formation of nodules, particularly of the joints of the hands as seen in the image below, are just some of the common symptoms individuals experience, which tend to worsen over time. Only the joints are affected. Sometimes individuals need joint replacements, such as knee or hip, if symptoms and damage become severe, which last about 10-15 years on average.
OA is the most common type of arthritis that affects the hip or knee. Prior trauma or injury, obesity, genetic factors, abnormal joints, or abnormal joint or limb development are risk factors for OA. A combination of mechanical stress plus low-grade chronic inflammation seem to play a part in the development of OA. As cartilage is lost and destroyed, so is the underlying bone. Muscle loss and pain may occur. It is the most common type of arthritis, and it affects around 3.5% of the population. Pain, stiffness, and crackling noises are associated with OA.
The main joints affected by osteoarthritis;By US federal government - http://www.niams.nih.gov/health_info/Osteoarthritis/default.asp, Public Domain, https://commons.wikimedia.org/w/index.php?curid=40173053
By Drahreg01 - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=1358952
By CFCF - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=44235706
By BruceBlaus - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=44968165
Osteoarthritis in a knee joint;By James Heilman, MD - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=10335934
Gout
Gout is a painful condition caused by deposits of monosodium urate crystals (MSU) or uric acid crystals in the joints. Gout is diagnosed by the finding of the crystals in joint fluid under uncompensated polarized light microscopy, as seen in the images below. MSU crystals are shaped like long needles or toothpicks with thicker centers and tapered, sharp ends, and range from 5-20 cm in length. With polarized light and a special filter, they are strongly birefringent. They exhibit sharp extinction and negative birefringence. The crystals are found either inside or outside of cells, or both. A red plate compensator is used to help distinguish uric acid crystals from CPPD crystals and other types.
If uric acid builds up in the synovial fluid, it results in saturnine gout (acute monoarticular arthritis or acute synovitis). This forms a super-saturated solution including overproduction or inefficient secretion of uric acid. In 90% of cases of acute saturnine gout, these MSU crystals will be able to be seen and identifiable in the synovial joint fluid. The higher the inflammation, the more crystals are seen. As inflammation subsides, however, the number of crystals will decrease unless there is an acute flare-up.
In attacks that are recurrent, urates may deposit in places such as the peri-articular soft tissues, helix of the ear, and cartilage. Gout can also coexist with other types of arthritis, including septic arthritis. During an inflammatory attack, synovial fluid may also contain many neutrophilic leukocytes.
MSU crystals that build up in the synovial membrane are referred to as "micro-tophi". Those that build up in soft tissue result in what is known as tophaceous gout. MSU crystal solubility decreases if the temperature decreases, as the two are linked.
Gout is a type of inflammatory arthritis, in which the joints become very painful, hot, red, and swollen. Individuals with gout are also prone to developing kidney stones as well. Gout is treated with anti-inflammatory medicines, sometimes steroids, colchicine, exercise and by a strict diet to avoid foods high in uric acid, and by taking vitamin C.
Monosodium Urate Crystal (Gout)
Monosodium Urate Crystal (Gout)
Uric Acid Crystals seen in gout;By Bobjgalindo - Own work, GFDL, https://commons.wikimedia.org/w/index.php?curid=5653456
Rheumatoid Arthritis
Rheumatoid arthritis (RA) is an autoimmune disease that is chronic and affects the joints. It causes red, hot, inflamed, swollen, painful, disfiguring, and stiffness of the joints. Fevers may occur on and off, as well as weakness and lack of energy with the disease. Sometimes, other parts of the body are affected as well, such as the lungs or heart. RA may be genetic, or may be the result of an illness. The immune system attacks the joints, resulting in damage to the cartilage, bone and a thickening of the joint capsule. It often follows illnesses such as systemic lupus erythematosis, psoriatic arthritis, strep throat that was untreated, fibromyalgia, and possibly even viruses.
Cholesterol Crystals;By Ed Uthman from Houston, TX, USA - Cholesterol Crystals in Synovial Fluid (compensated polariscopy)Uploaded by CFCF, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=30104382
By Ed Uthman from Houston, TX, USA - Cholesterol Crystals in Synovial Fluid (compensated polariscopy)Uploaded by CFCF, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=30104384
By Ed Uthman, MD, pathologist, Houston, Texas, USA - Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=12153007
By Ed Uthman from Houston, TX, USA - Cholesterol Crystals in Synovial Fluid (compensated polariscopy)Uploaded by CFCF, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=30104383
By James Heilman, MD - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=11110471
By James Heilman, MD - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=9445237
By Bernd Brägelmann Braegel Mit freundlicher Genehmigung von Dr. Martin Steinhoff - Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=3961869
Pseudogout: Chondrocalcinosis
Pseudogout is a condition that includes acute inflammation of the joint, synovitis, redness, swelling, tenderness, and pain resembling that of gouty arthritis, however, the deposition of crystals is of different types. This condition involves calcification of hyaline cartilage or fibrocartilage within the joint. It may occur with osteoarthritis. Research is still underway to determine the exact causes of this condition, however, interestingly, it may be linked to a breakdown in the body's usable energy, ATP (adenosine triphosphate). Hypercalcemia seems to play a role, and in some cases, increasing one's intake of magnesium tends to bring the levels back into more of a balance and alleviate symptoms. Thyroid and parathyroid imbalances, low potassium levels, hereditary hemochromatosis, osteoarthritis, and Wilson's disease appear to be linked to this condition as well, and treating these underlying conditions tend to help alleviate symptoms.
Calcium pyrophosphate dihydrate (CPPD) crystals, which are often needle-shaped and positively birefringent under red plate compensator, are similar to MSU crystals, and may be a sign of pseudogout. CPPD crystals tend to form in damaged soft tissue matrix within the joint cartilage. These crystals form within articular cartilage, next to chondrocytes (cartilage cells). CPPD crystals are sometimes found in joint aspirates of patients with acute osteoarthritis.
Clinical laboratory tests in addition to what is mentioned above may include a white blood cell count, which tend to be elevated. Radiology tests and joint fluid analysis tests are also typically ordered. Diagnosis is based on symptoms, radiology results, arthrocentesis joint fluid analysis and findings of crystals seen in the image below. Calcium pyrophosphate dihydrate crystals are a typical rhomboid shape with weak positive birefringence by polarized microscopy.
Treatment is recommended because of potential organ damage over time. Intra-articular corticosteroid injections, non-steroidal anti-inflammatory drugs, or other medicines are often administered to aid in relief of symptoms.
Calcium pyrophosphate dihydrate crystal in a knee arthrocentesis (rhombus shape)-CPPD;By David Iberri - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=24763637
Steroid Crystals:
When examining synovial fluid, one should note that steroid crystals, which closely resemble MSU and CPPD crystals of gout and pseudogout respectively, may be present for a couple of weeks after an injection of intra-articular steroids. These crystals may also form needles, which may be either positively or negatively birefringent. Steroid shots can cause pain in joints, referred to as a "steroid flare" (burning pain).
Other Crystals Present in Body Fluids:
Other types of crystals may be found in body fluids. These include starch, oxalate, hematin, lipids and cholesterol. They each have their own unique shape and defining characteristics. Some are significant, whereas others are simply artifact.