Leg Pain (cont.)
Leg Pain Diagnosis
The evaluation of leg pain always begins with the care provider interviewing the patient and performing a physical examination to help determine the potential cause of the leg pain and what direction testing may need to take to confirm a diagnosis. Sometimes testing and
X-rays are not required.
Infection and inflammation may be detected by blood tests, including a white blood cell count, an erythrocyte sedimentation rate (ESR), and a C-reactive protein (CRP) measurement. These are nonspecific tests that may give further direction to the care provider. Please note that the white blood cell count may be elevated with an infection unless the patient has some immune system compromise, at which point it may be falsely normal. As with all tests, the ESR and CRP, if elevated, need to be interpreted in light of the specific illness that is being considered.
If gout is a consideration, a blood test to measure uric acid may be done;
however, in the acute attack, the uric acid level may be high, low, or normal.
The result is helpful if the level is high and may confirm a gout flare if
supported by the history and physical examination.
Other blood tests may be considered depending upon the underlying medical
illnesses being considered.
- X-rays: If there is concern that a fracture or broken bone is present, plain
may be indicated. As well, X-rays may be taken as a screening to look for fluid or calcifications
in a joint.
- Ultrasound: Ultrasound may be helpful in making the diagnosis of deep vein thrombosis. Superficial vein thrombosis is usually diagnosed clinically based upon the physical examination, and no imaging may be required.
- Ankle-brachial index (ABI): Arterial blood flow in the legs may be assessed by an ankle-brachial index, in which blood flow is evaluated at rest and with exercise. This test involves comparing the blood pressure in the arms to the blood pressure in the legs.
- Arteriogram: If further information is needed about the arteries, an
arteriogram may be
performed to look directly at the arterial supply to the legs. This is
accomplished by injecting contrast dye directly into the arteries and watching
it flow through the arteries in the legs via X-rays. Arteriography may also be carried out using CT or MRI studies (see below).
- CT scan: Computerized tomography (CT) may be used in a variety of
situations. CT angiography may be able to take the place of arteriography is some situations to
examine blood vessels. CT may also be used to evaluate bone and joint anatomy,
looking for hidden fractures.
- MRI: Magnetic resonance
imaging (MRI) may be used to examine the back for the causes of sciatica to evaluate bones, joints, and soft tissues such as muscles, tendons, and ligaments. MRI angiography may also be considered in place of formal angiography to evaluate blood vessels in the body.
- Nerve conduction studies: Nerve conduction studies may be considered to evaluate nerve function and
measure the ability of specific nerves to carry electrical impulses. This is helpful in deciding whether nerve pain is due to a central cause from the brain or spinal cord or due to a peripheral nerve injury. (For example, inflammation of the ulnar nerve from hitting your funny bone can cause the ring and little fingers to go numb.)
- Joint aspiration: If there is concern about infection or inflammation within a joint, a needle may be put into the joint to pull out or aspirate fluid for
Often this fluid is sent to a laboratory to analyze the white blood cell
count within the fluid (an elevated white blood cell count may signal
inflammation), a gram stain and culture looking for bacterial infection, or crystal analysis looking for uric acid or calcium pyrophosphate crystals to make the diagnosis of gout or pseudogout, respectively.
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