How Is LAM Diagnosed?
Methods for diagnosing LAM have improved, and it is
now possible to diagnose it at an early stage.
Many of the signs and symptoms of LAM can be caused
by other diseases such as
asthma,
emphysema, and bronchitis. It is important for your doctor to rule out those
conditions before making a final diagnosis.
- Chest x ray. A chest x ray takes a picture of your heart and
lungs. It can show a collapsed lung or fluid in your chest cavity. In the early
stages of LAM, your chest x rays may look normal, but as the disease gets
worse, they may show cysts in your lungs.
- Lung function tests. For these tests, you breathe through a
mouthpiece into a machine called a spirometer (spi-ROM-e-ter). The spirometer
measures the amount of air you inhale and exhale and how fast your lungs move
it in and out. These tests also can provide an estimate of the amount of air
your lungs can hold, and how well your lungs can take oxygen into the
bloodstream.
- Exercise stress test. This test helps the doctor evaluate the
effect of exercise on your heart and lungs.
- Blood tests. The doctor takes a sample of your
blood from an artery in your arm and examines it to see whether your lungs are
providing enough oxygen to your blood. These tests may show low oxygen levels
in your blood even when you are resting. The doctor also may take a blood
sample from a vein in your arm to look at your blood cells and blood
chemistry.
- Pulse oximetry. A small sensor attached to your
fingertip also can give an estimate of the level of oxygen in your blood.
- High-resolution CT scan (HRCT). This test shows a
computer-generated picture of your lungs that has more detail than a chest x
ray. It is the most useful imaging test for diagnosing LAM. HRCT can show cysts
or shadows of cell clusters in your lungs, a collapsed lung, or enlarged lymph
nodes. It also can show how much normal lung tissue has been replaced by the
LAM cysts. HRCT scans of your abdomen and pelvis can show if you have growths
in your kidneys, other abdominal organs, or lymph nodes.
- Lung biopsy. Although the tests mentioned above sometimes
provide enough information for your doctor to diagnose LAM, the most useful
test involves removing samples of your lung tissue so they can be looked at
under a microscope. You should go to a doctor who specializes in LAM for this
test. Several procedures can be used to obtain lung tissue:
- Thoracoscopy (tho-rah-KOS-ko-pe). Your doctor
inserts a small, lighted tube (endoscope) into little incisions in your chest
wall. This lets him or her see the insides of your chest and snip out a few
small pieces of lung tissue. This procedure is done in a hospital, and you are
under general anesthesia. It is not major surgery, but it usually provides all
the tissue your doctor needs.
- Open lung biopsy. Your doctor removes a few small pieces of
lung tissue through an incision in your chest wall between your ribs. This
procedure also is done in the hospital, and you are under general anesthesia.
Recovery takes longer than recovery from thoracoscopy.
- Transbronchial biopsy. Your doctor inserts a
long, narrow, flexible, lighted tube (bronchoscope) down your windpipe, or trachea (TRA-ke-ah), into
your lungs. He or she then snips out bits of lung tissue with a tiny forceps.
This procedure is usually done in a hospital on an outpatient basis, and you
are under local anesthesia. Doctors usually are not able to remove enough
tissue to diagnose LAM with this procedure.
Some doctors recommend that once you are diagnosed
with LAM, you have
magnetic resonance imaging (MRI) of your head. This test can
show if you have signs of
tuberous sclerosis complex (TSC) or a growth in your brain
called a meningioma (me-NIN-je-O-mah). About 1 out of every 20 patients with
LAM has this kind of growth. It also appears in people with TSC.
The National Institutes of Health is studying
whether blood tests for the TSC1 and TSC2 genes may be helpful in diagnosing
LAM patients. |