AJR 2002; 178:405-412
© American Roentgen Ray Society
Using Lymphoscintigraphy to Evaluate Suspected Lymphedema of the Extremities
Mariam Moshiri1,
Douglas S. Katz1,
Marvin Boris2 and
Elizabeth Yung1
1
Department of Radiology, Winthrop University Hospital, 259 First St., Mineola,
NY 11501.
2
Lymphedema Therapy, 77 Froehlich Farm Blvd., Woodbury, NY 11797.
Received June 15, 2001;
accepted after revision July 30, 2001.
Presented at the annual meeting of the American Roentgen Ray Society,
Seattle, April 2001.
Address correspondence to D. S. Katz.
Lymphedema is the painless progressive accumulation of protein-rich fluid
in the interstitial spaces of the skin, resulting from an anatomic or
functional obstruction of the lymphatic system
[1]. Lymphedema of the lower or
upper extremities is typically a chronic condition that has several possible
causes and that presents considerable physical as well as psychological
difficulties for patients [2].
Patients with lymphedema experience extremity swelling, decreased coordination
and mobility, and secondary infections
[2]. The disorder typically
affects the dermis and spares the deeper compartments
[3]. At the initial medical
evaluation of patients with suspected extremity lymphedema, it is highly
desirable for physicians to define the abnormality; to determine whether the
suspected abnormality is, in fact, a lymphatic one (Figs.
1A,1B
and
2A,2B)
before instituting a therapeutic plan; and to establish an objective baseline
[3]. The differential diagnosis
of suspected extremity lymphedema includes obesity, venous disease, and
systemic disease (e.g., hypoalbuminemia)
[2]. Lymphoscintigraphy is now
the primary imaging modality used in determining a diagnosis in patients with
suspected extremity lymphedema. The technique has been refined over the past
few decades and has proved reliable and reproducible
[2]. The study is noninvasive
with no known adverse effects. In addition, the radiation dose received during
the examination is low, and the study can be repeated after therapy
[3].
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Fig. 1A. —37-year-old man who presented with bilateral leg edema for
several years after bicycle crash but had normal findings on
lymphoscintigraphy. Anterior lymphoscintigrams obtained 1 hr (A) and 3
hr (B) after injection of radionuclide show no abnormalities. Note that
two main lymphatic trunks (closed arrows, A) in both calves
and both thighs and ilioinguinal lymph nodes are symmetric. Artifacts
(open arrows, A) related to scatter at injection sites in both
feet are present. Cardiac, renal, and bladder uptake seen on B is due
to free pertechnetate.
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Fig. 1B. —37-year-old man who presented with bilateral leg edema for
several years after bicycle crash but had normal findings on
lymphoscintigraphy. Anterior lymphoscintigrams obtained 1 hr (A) and 3
hr (B) after injection of radionuclide show no abnormalities. Note that
two main lymphatic trunks (closed arrows, A) in both calves
and both thighs and ilioinguinal lymph nodes are symmetric. Artifacts
(open arrows, A) related to scatter at injection sites in both
feet are present. Cardiac, renal, and bladder uptake seen on B is due
to free pertechnetate.
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Fig. 2A. —55-year-old woman with clinically suspected lymphocele in
right axilla and edema in right upper extremity but with normal findings on
lymphoscintigraphy. Early lymphoscintigram of upper extremities obtained 10
min after injection of radionuclide, with patient's shoulders at top of image,
shows rapid lymphatic drainage. A = level of axillae, E = level of elbows, RT
= right side, LT = left side.
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Fig. 2B. —55-year-old woman with clinically suspected lymphocele in
right axilla and edema in right upper extremity but with normal findings on
lymphoscintigraphy. Delayed lymphoscintigram of both axillary regions and
upper thorax shows normal bilateral axillary lymph nodes (arrows).
Note absence of lymphocele or any other abnormality.
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Classification of Lymphedema
Various clinical classification systems have been developed to describe the
severity of extremity lymphedema
[2]. One system
[4] classifies lymphedema as
stage 1, 2, or 3. Stage 1 is reversible lymphedema, with pitting edema and
swelling that decreases when the limb is elevated, and stage 2 is nonpitting
edema that does not decrease when the limb is elevated. Stage 3 is
lymphostatic elephantiasis, with a huge increase in size of the limb and
hardened skin.
Primary lymphedema (Figs.
3,4A,4B,5A,5B,5C,5D,5E)
can be a nonhereditary or a genetic condition; can be unilateral or bilateral;
and may present at birth, at puberty, or in adulthood
[3]. The onset of edema is
usually spontaneous—without a history of trauma, surgery, or radiation
therapy [2]—and most
often occurs in patients before the ages 30 or 35 years; the lower limbs are
more often and more severely affected than the upper extremities
[2,
3]. The nonfamilial form is
much more common than the familial form. Secondary lymphedema (Figs.
6,7,8,9A,9B,10,11),
which is much more common than primary lymphedema, may be caused by therapy
for cancer, particularly axillary lymph node dissection and radiation therapy
for breast cancer, as well as regional lymph node dissection for melanoma and
pelvic lymph node dissection
[2,
3]. The disorder can present
months or years after the initial injury, and its origin is complex
[3]. In the developing world,
filariasis and other infections are common causes of secondary lymphedema
[3]. In some cases, it may not
be possible to categorize patients as having either primary or secondary
lymphedema, either by history or by lymphoscintigraphy (Figs.
12A,12B,13,14A,14B,14C,14D).
Both primary and secondary lymphedema can progress to chronic inflammation and
irreversible perilymphatic fibrosis
[1].
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Fig. 3. —34-year-old man with recurrent left foot and leg swelling and
multiple episodes of left leg cellulitis. Anterior lymphoscintigram obtained 3
hr after injection of radionuclide reveals markedly delayed and diminished
flow in left leg, with no lymphatic trunks or clinically relevant collaterals
visualized. Note absence of radionuclide uptake in expected location of left
ilioinguinal lymph nodes (thick arrow), compared with uptake on right
side (thin arrow). Findings are consistent with aplasia of lymphatic
vessels in left leg and primary lymphedema. LT = left side of body.
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Fig. 4A. —64-year-old woman who has had bilateral lower extremity
swelling for 42 years (worse on left), consistent with primary lymphedema.
Anterior lymphoscintigram of lower extremities obtained 1 hr after injection
of radionuclide shows little lymphatic drainage. Upper marker indicates
location of groin, and lower marker indicates knee.
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Fig. 4B. —64-year-old woman who has had bilateral lower extremity
swelling for 42 years (worse on left), consistent with primary lymphedema.
Lymphoscintigram obtained 3.5 hr after injection of radionuclide reveals few
lymphatic channels bilaterally and marked dermal backflow (arrows) in
lower calves.
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Fig. 5A. —30-year-old man with primary lower extremity lymphedema and
Prader-Willi syndrome. Lymphoscintigram obtained 45 min after injection of
radionuclide shows multiple large and tortuous lymphatic channels with
multiple additional lymphatic vessels in thighs and calves. Increased numbers
of bilateral ilioinguinal lymph nodes (small arrows) as well as
megalymphatics (large arrows) in right calf both medially and
laterally are visible.
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Fig. 5B. —30-year-old man with primary lower extremity lymphedema and
Prader-Willi syndrome. Anterior lymphoscintigram obtained 2.5 hr after
injection of radionuclide shows prominent number of fine collateral lymphatic
channels (open arrow) and left dermal backflow (solid
arrow).
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Fig. 5C. —30-year-old man with primary lower extremity lymphedema and
Prader-Willi syndrome. Spot posterior lymphoscintigram obtained 3.5 hr after
injection of radionuclide shows improved visualization of right collateral
channels and subtle left dermal backflow (arrows). Dermal backflow is
secondary effect of poor lymphatic transport. Round marker in left upper
corner of image indicates level of knees. RT = right side, LT = left side.
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Fig. 5D. —30-year-old man with primary lower extremity lymphedema and
Prader-Willi syndrome. Photographs of legs before (D) and after
(E) complex lymphedema therapy. Note improvement, particularly at
ankles.
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Fig. 5E. —30-year-old man with primary lower extremity lymphedema and
Prader-Willi syndrome. Photographs of legs before (D) and after
(E) complex lymphedema therapy. Note improvement, particularly at
ankles.
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Fig. 6. —58-year-old man with left leg edema after prostate and
bilateral pelvic lymph node resection. Anterior lymphoscintigram obtained 95
min after injection of radionuclide shows delayed left lower extremity
lymphatic drainage with decreased left ilioinguinal lymph nodes (large
arrow). Collateral lymphatic trunks are seen in left thigh and calf
(small arrows). Same findings were present on image obtained 4 hr
after injection (not shown).
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Fig. 7. —72-year-old man with secondary lymphedema in left leg after
fall that injured leg several months earlier. Anterior spot lymphoscintigram
of both calves obtained 3.5 hr after injection of radionuclide shows decreased
number of lymphatic channels in left calf (large arrows), with
associated dermal backflow (small arrows). K = level of knees, A =
level of ankles, RT = right side, LT = left side.
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Fig. 8. —53-year-old man who fractured right ankle 1 year earlier
presented with right leg swelling. Anterior lymphoscintigram obtained 3.25 hr
after injection of radionuclide shows normal left lower extremity but dermal
backflow (solid arrows) in right calf. Note increased number of
right-sided ilioinguinal lymph nodes (open arrows) of uncertain
importance.
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Fig. 9A. —71-year-old woman with right lower extremity edema and
history of substantial injury to right knee. Anterior lymphoscintigram
(composite transmission and emission image) of both calves obtained 25 min
after injection of radionuclide reveals normal left leg and focal collection
(arrow) in right medial calf representing lymphocele.
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Fig. 9B. —71-year-old woman with right lower extremity edema and
history of substantial injury to right knee. Lymphoscintigram obtained 4.5 hr
after injection of radionuclide reveals marked dermal backflow
(arrow) in right calf, which hides focal collection visible on
earlier image. Note markedly delayed lymphatic drainage in right calf.
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Fig. 10. —55-year-old woman who has experienced right arm edema for 1
year after removal of recurrent right axillary cysts and abscesses. Image was
acquired with patient's outstretched arms placed on rectangular view camera.
Early lymphoscintigram of arms shows delayed lymphatic drainage in right arm,
with fewer lymph nodes in right (open arrow) than in left axilla
(solid arrow) and collateral channels at level of right elbow,
consistent with secondary lymphedema. Dashed arrows indicate elbow
markers.
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Fig. 11. —66-year-old man with history of swelling in left arm after
removal of left forearm melanoma and left axillary lymph node dissection.
Lymphoscintigram of arms obtained 50 min after injection of radionuclide shows
rapid lymphatic drainage of both forearms but decreased number of left
axillary lymph nodes (small arrow) and multiple focal collections
(large arrow) in left upper arm, consistent with dilated lymphatics.
Findings are consistent with left axillary level obstruction from previous
lymph node dissection. H = level of hands, E = level of elbows, A = level of
axillae, RT = right side, LT = left side.
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Fig. 12A. —43-year-old woman with history of extensive travel to
numerous developing countries evaluated for suspected lymphedema. Results of
multiple examinations for infection—including filarial
disease—were negative. Photograph of patient shows massive swelling in
both thighs.
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Fig. 12B. —43-year-old woman with history of extensive travel to
numerous developing countries evaluated for suspected lymphedema. Results of
multiple examinations for infection—including filarial
disease—were negative. Lymphoscintigram of lower extremities shows
dermal backflow (arrow) in right calf, with otherwise prompt
lymphatic drainage in both legs. No right lymphocele or other right thigh
lymphatic abnormality is revealed. Left leg is unremarkable. Findings are
consistent with obesity ("lipedema") with relatively minor
lymphatic abnormality in right calf unrelated to obesity.
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Fig. 13. —41-year-old woman who had lymphangioma removed from left
thigh at birth and who presented with new soft-tissue mass in left anterior
thigh and edema of left lower extremity. Delayed lymphoscintigram of lower
extremities reveals no lymphocele or dermal backflow but does show fewer
ilioinguinal lymph nodes (arrow) on left side than on right. Latter
finding may be residual effect of prior surgery, normal variant, or related to
low flow obstruction.
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Fig. 14A. —44-year-old man who had bilateral lower extremity edema below
the waist for 1 year without history of surgery or trauma. Abdominal and
pelvic lymphadenopathy identified on CT was biopsied and was negative for
malignancy. Cause of findings is unknown. Early anterior lymphoscintigrams of
calves (A) and knees (B) show fine lymphatic collaterals
(arrows), especially in left leg. R = right side, L = left side.
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Fig. 14B. —44-year-old man who had bilateral lower extremity edema below
the waist for 1 year without history of surgery or trauma. Abdominal and
pelvic lymphadenopathy identified on CT was biopsied and was negative for
malignancy. Cause of findings is unknown. Early anterior lymphoscintigrams of
calves (A) and knees (B) show fine lymphatic collaterals
(arrows), especially in left leg. R = right side, L = left side.
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Fig. 14C. —44-year-old man who had bilateral lower extremity edema below
the waist for 1 year without history of surgery or trauma. Abdominal and
pelvic lymphadenopathy identified on CT was biopsied and was negative for
malignancy. Cause of findings is unknown. Lymphoscintigram obtained 45 min
after injection of radionuclide shows lymphocele or megalymphatic vessel
(large arrow) in right calf, diffuse bilateral dermal backflow
(small arrows), and early filling (open arrow) of abnormal
structures in abdomen and pelvis, consistent with small lymph nodes and
abnormal lymph vessels in mesentery.
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Fig. 14D. —44-year-old man who had bilateral lower extremity edema below
the waist for 1 year without history of surgery or trauma. Abdominal and
pelvic lymphadenopathy identified on CT was biopsied and was negative for
malignancy. Cause of findings is unknown. Lymphoscintigram obtained 3.5 hr
after injection of radionuclide shows diffuse bilateral dermal backflow and
extravasation (small arrows) from lymphatic channels. Abnormal
structures (large arrows) in abdomen and pelvis are accentuated and
are also seen in thorax (open arrow).
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Technique of Lymphoscintigraphy
In the most common method used to perform lymphoscintigraphy of the
extremities, 74-296 MBq of millipore-filtered 99mTc sulfur colloid
suspended in 0.10 mL of saline is injected into the interdigital web spaces
between the first and second digits on the patient's right and left lower (or
upper) extremities, creating a wheal. Both of the feet (or hands) are massaged
for 2 min immediately after the injection. A high-resolution collimator is
always used, the camera speed is set at 8 cm/min, and images of at least
300,000 counts are acquired. A flow study is performed, and the arrival of
radionuclide delivery to the knees and groin (or to the elbows and axillary
regions for the arms) is timed. Spot and whole-body images are obtained for up
to 3-4 hr; the study is also tailored to the need for individual findings.
Findings on Lymphoscintigraphy
In patients with normal lymphatic anatomy and function (Figs.
1A,1B
and
2A,2B),
a predictable sequence should be seen on lymphoscintigraphy. In the lower
extremities, symmetric migration of the radionuclide should be seen through
discrete lymph vessels (three to five lymph vessels per calf and one to two
per thigh). Then bilateral visualization of ilioinguinal lymph nodes should
occur within 1 hr, as should visualization of the liver because of the
systemic circulation of the radiocolloid
[1]. Typically, approximately
one to three popliteal nodes and two to 10 ilioinguinal nodes are visualized
[5]. A parallel sequence should
be seen in the upper extremities.
On lymphoscintigrams with abnormal findings, a variety of findings can be
identified (Figs.
3,4A,4B,5A,5B,5C,5D,5E,6,7,8,9A,9B,10,11,12A,12B,13,14A,14B,14C,14D),
including interruption of lymphatic flow, collateral lymph vessels, dermal
backflow, delayed flow, delayed visualization or nonvisualization of lymph
nodes, a reduced number of lymph nodes, dilated lymphatics, and in severe
cases, no visualization of the lymphatic system at all
[1,
5]. Purely qualitative analysis
has been reported to be very accurate for confirming or excluding the
diagnosis of lymphedema, with a sensitivity as high as 92% and a specificity
as high as 100% [1].
Despite earlier reports, most authorities believe that primary lymphedema
cannot be reliably differentiated from secondary lymphedema on the basis of
lymphoscintigraphic findings alone
[1,
5]. Some authors have reported
that lymphoscintigrams of patients with primary lymphedema tend to show a lack
of lymphatic vessels and absent or delayed transport, whereas those of
patients with secondary lymphedema tend to show obstruction with visualization
of discrete lymphatic trunks and slow transport
[3]. In both primary and
secondary lymphedema, however, both dermal backflow and a decreased number of
lymph nodes can be identified
[3].
Therapy for Lymphedema and Role of Scintigraphic Follow-Up
Lymphedema is a chronic condition that is notoriously difficult to treat
and that has no known curative therapy. Surgical procedures have been
attempted, but none have proven to be particularly successful
[2]. At present, the most
successful conservative therapy is a 4-6 week regime known as complex
lymphedema therapy
[6,7,8].
This labor-intensive therapy requires as many as 4 hr per day
[4,
6,
7] (Figs.
5D and
5E). In a report by Boris et
al. [7], 30 patients whose
progress was followed up for as long as 1 year after complex lymphedema
therapy had an average 86% decrease in their initial extremity volume.
Lymphoscintigraphy can be repeated after therapy to provide an objective
measure of the disease status in patients
[3,
4,
8].
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