DOI:10.2214/AJR.04.1041
AJR 2005; 185:1011-1014
© American Roentgen Ray Society
Distended Thoracic Duct and Diffuse Lymphangiectasia Caused by Bancroftian Filariasis
Peter J. Ahn1,
Reono Bertagnolli1,
Susan L. Fraser2 and
Judy H. Freeman3
1 Department of Radiology, Tripler Army Medical Center, 1 Jarrett White Rd.,
Honolulu, HI 96859.
2 Department of Internal Medicine, Tripler Army Medical Center, Honolulu,
HI.
3 Department of Pathology, Tripler Army Medical Center, Honolulu, HI.
Received June 30, 2004;
accepted after revision October 15, 2004.
The opinions and assertions contained herein are the private views of the
authors and are not to be construed as official or as reflecting the views of
the Department of the Army or the Department of Defense. 1 Jarrett White Rd.,
Honolulu, HI 96859. Address correspondence to P. J. Ahn
(Peter.Ahn{at}andrews.af.mil).
Introduction
Filariasis is a disease endemic to subtropical areas that is rarely
encountered in North America. Because this infection rarely occurs in the
United States, our knowledge of CT and MRI findings associated with it is
limited. To date, the CT and MRI features of filarial lymphangiectasia in a
human have not been described. We present a case of diffuse lymphangiectasia
in a patient with filariasis as revealed by CT and MRI findings.
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Fig. 1A —23-year-old man with filariasis. Contrast-enhanced CT scans
of chest reveal low-density tubular structure (arrowheads) in
posterior mediastinum, with central attenuation value ranging from 15 to 32
H.
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Fig. 1B —23-year-old man with filariasis. Contrast-enhanced CT scans
of chest reveal low-density tubular structure (arrowheads) in
posterior mediastinum, with central attenuation value ranging from 15 to 32
H.
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Case Report
A 23-year-old U.S. marine, who was born and raised in Guyana, South
America, before emigrating to the United States at age 21, presented to a
primary care facility in Japan, his military duty station, with fever and
acute abdominal pain radiating to the right groin. Bilateral inguinal
adenopathy was found, and a whole-body CT scan revealed what was thought to be
diffuse posterior mediastinal, retroperitoneal, pelvic, and inguinal
lymphadenopathy. He had no scrotal abnormalities. His symptoms improved on
empiric antibiotic therapy, and fine-needle aspiration of an enlarged right
inguinal lymph node was performed. He was then referred to our institution
with a diagnosis of possible lymphoma.
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Fig. 1E —23-year-old man with filariasis. Coronal (E) and
rotated oblique coronal (F) single-shot fast spin-echo images
(11,430/98) further help delineate distended thoracic duct
(arrowheads), originating below diaphragm and coursing superiorly
just anterior to thoracic vertebral column.
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Fig. 1F —23-year-old man with filariasis. Coronal (E) and
rotated oblique coronal (F) single-shot fast spin-echo images
(11,430/98) further help delineate distended thoracic duct
(arrowheads), originating below diaphragm and coursing superiorly
just anterior to thoracic vertebral column.
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Enhanced CT scans of the chest, abdomen, and pelvis were obtained at our
institution. The chest CT scan revealed a low-density tubular structure in the
posterior mediastinum, with maximum dimensions of 3.0 x 1.6 cm at the
T10 level (Figs. 1A and
1B). It extended from the
thoracic inlet to the level below the diaphragmatic crura. Single-shot fast
spin-echo MR images in multiple planes confirmed a fluid-filled tubular
structure extending from L1 level to the junction of left subclavian and
internal jugular veins (Figs.
1C,
1D,
1E, and
1F), consistent with a
distended thoracic duct. No chylothorax was present. CT of the abdomen
revealed diffuse nonenhancing low-density material in the retroperitoneum,
surrounding the inferior vena cava, aorta, and proximal renal vessels
(Fig. 1G). Similar low-density
material was distributed in the pelvis, more prominently along the right iliac
vessels (Fig. 1H). MR images
confirmed nonenhancing fluid-filled structures distributed in the
retroperitoneum and pelvis (Figs.
1I and
1J), consistent with diffuse
lymphangiectasia. More readily apparent on MRI were superficial inguinal
lymphangiectasia (Fig. 1K) and
mild scrotal subcutaneous lymphangiectasia (not shown).
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Fig. 1G —23-year-old man with filariasis. Enhanced CT scans of abdomen
(G) and pelvis (H) show nonenhancing low-density material in
retroperitoneum and pelvis surrounding aorta, inferior vena cava, proximal
renal vessels, and iliac vessels (arrowheads). Central attenuation
value of this diffusely distributed material ranged from 8 to 27 H in
retroperitoneum and from 22 to 30 H along common iliac and external iliac
vessels.
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Fig. 1H —23-year-old man with filariasis. Enhanced CT scans of abdomen
(G) and pelvis (H) show nonenhancing low-density material in
retroperitoneum and pelvis surrounding aorta, inferior vena cava, proximal
renal vessels, and iliac vessels (arrowheads). Central attenuation
value of this diffusely distributed material ranged from 8 to 27 H in
retroperitoneum and from 22 to 30 H along common iliac and external iliac
vessels.
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Fig. 1I —23-year-old man with filariasis. Single-shot fast spin-echo
images (12,500/99) show high-signal-intensity confluence of dilated lymphatic
ducts and vessels in retroperitoneum and pelvis.
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Fig. 1J —23-year-old man with filariasis. Single-shot fast spin-echo
images (12,500/99) show high-signal-intensity confluence of dilated lymphatic
ducts and vessels in retroperitoneum and pelvis.
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Fig. 1L —23-year-old man with filariasis. High-power microscopic view
of microfilaria of Wuchereria bancrofti obtained from peripheral
blood smear shows presence of distinct sheath and absence of nuclei in tail.
(Wright-Giemsa stain)
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On reviewing the fine-needle aspiration sample of the patient's inguinal
lymph node, a single microfilaria was identified. His peripheral blood smear
revealed many motile microfilariae, and a Wright-Giemsa-stained buffy coat
confirmed the diagnosis of Wuchereria bancrofti
(Fig. 1L).
The patient was treated with a half dose of ivermectin, followed 1 week
later with diethylcarbamazine obtained from the Centers for Disease Control
and Prevention. His treatment was complicated by severe testicular pain, mild
fever, anorexia, nausea, headache, and mild eosinophilia. He returned to duty
in good health.
Discussion
Human lymphatic filariasis is caused by infections with W. bancrofti,
Brugia malayi, or Brugia timori. These parasites are found in many
tropical and subtropical areas of the world. The adult worms live in the
lymphatics throughout the body and cause extensive lymphangiectasia by
obstructing lymph flow. Filariasis is the most common cause of acquired
lymphedema in the world [1].
Interestingly, our patient had neither scrotal nor lower extremity edema.
Chest CT revealed a tubular structure in the posterior mediastinum,
coursing along the thoracic spine. Its central attenuation value ranged from
15 H in a more distended segment to 32 H in the least distended portion, which
was behind the left atrium. The low-density tubular structure in the posterior
mediastinum of this patient is a distended thoracic duct. The thoracic duct
collects lymph from most body tissues and transmits it back into the blood
stream. The duct originates in the abdomen anterior to the second lumbar
vertebra at the cisterna chyli and then ascends into the thorax through the
aortic hiatus of the diaphragm slightly to the right of the midline. Within
the posterior mediastinum of the thorax and still coursing just ventral to the
vertebral column, the thoracic duct gradually crosses the midline to the left.
The duct then ascends into the root of the neck on the left side and drains
into the left subclavian vein near the junction of the left internal jugular
vein [2].
An abdominal CT scan revealed low-attenuation material distributed in the
retroperitoneum and pelvis that showed no enhancement with IV contrast
material. The central attenuation value ranged from 8 to 27 H in the
retroperitoneum and 22 to 30 H in the pelvis along the iliac vessels. No
discrete mass was identified associated with this diffuse abnormality. MR
images clearly revealed nonenhancing confluence of prominent lymphatic ducts
and vessels. Superficial inguinal lymphangiectasia and mild scrotal
subcutaneous lymphangiectasia were also more readily evident on heavily
T2-weighted images.
Case et al. [3] used MRI to
detect dilated lymphatic vessels in ferrets infected with B. malayi.
In 1999, Blacksin et al. [4]
reported the first description of MRI findings in a human, a case of
bancroftian filariasis affecting the ankle joint
[4]. Witte et al.
[5] described the potential use
of MRI, particularly fat-saturated T2-weighted images, for the evaluation of
the lymphatic system. Schick et al.
[6] described cystic lymph node
enlargement of the neck on MRI in a patient with filariasis.
This case shows the distended thoracic duct on CT as a nonenhancing
low-attenuation tubular structure in the posterior mediastinum. Its
recognition is made easier by knowing the anatomic origin and course of the
thoracic duct. Diffuse lymphangiectasia in the retroperitoneum and pelvis
appears on CT as nonenhancing low-attenuation material along major vessels and
is not associated with a discrete mass. MR images, particularly single-shot
fast spin-echo images, a heavily T2-weighted pulse sequence, helped reveal the
nonenhancing fluid-filled thoracic duct and prominent lymphatic ducts and
vessels. To our knowledge, this case is the first reported case of distended
thoracic duct and diffuse central and peripheral lymphangiectasia in a patient
with active filarial infection.
References
- Szuba A, Rockson SG. Lymphedema: classification, diagnosis and
therapy. Vasc Med 1998;3
: 145-156[Abstract/Free Full Text]
- Clemente CD. Anatomy: a regional atlas of the human
body, 3rd ed. Baltimore, MD: Urban & Schwarzenberg,1987
: Figures 222, 223
- Case TC, Unger E, Bernas MJ, et al. Lymphatic imaging in
experimental filariasis using magnetic resonance. Invest
Radiol 1992; 27:293
-297[Medline]
- Blacksin MF, Lin SS, Trofa AF. Filariasis of the ankle: magnetic
resonance imaging. Foot Ankle Int 1999;20
: 738-740[Medline]
- Witte CL, Witte MH, Unger EC, et al. Advances in imaging of lymph
flow disorders. RadioGraphics 2000;20
: 1697-1719[Abstract/Free Full Text]
- Schick C, Thalhammer A, Balzer JO, et al. Cystic lymph node
enlargement of the neck: filariasis as a rare differential diagnosis in MRI.
Eur Radiol 2002;12
: 2349-2351[Medline]
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Introduction
Case Report
