(Radiology. 1999;213:192-194.)
© RSNA, 1999
Vascular and Interventional Radiology |
Intraaortic Growth of Hydatid Cysts Causing Occlusion of the Aorta and of Both Iliac Arteries: Case Report1
Süleyman Men, MD,
Cüneyt Yücesoy, MD,
Tahsin R. Edgüer, MD and
Baki Hekimoglu, MD
1 From the Department of Radiology, SSK Ankara Hastanesi (Social Security Ankara Hospital), TR-06110 Di
kapi Ankara, Turkey. Received September 11, 1998; revision requested November 3; revision received December 22; accepted February 15, 1999. Address reprint requests to S.M., Atayolu sokak No=7/5, TR-06450 Dikmen Ankara, Turkey.
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Abstract
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A woman who had been operated on previously for a paraspinal hydatid cyst presented with claudication of the lower limbs. Computed tomographic and magnetic resonance images showed multiple cysts in the soft tissues of the back, retroperitoneum, and lumen of the aorta and iliac arteries. Occlusion of the aorta and iliac arteries by recurrent hydatid cysts after previous surgery was confirmed with angiography and subsequent surgical exploration. The authors present the imaging findings of this unusual manifestation of cystic echinococcosis.
Index terms: Aorta, diseases, 981.2083 • Aorta, stenosis or obstruction, 981.7214 • Arteries, CT, 988.12911, 988.12912 • Arteries, iliac, 984.2083 • Arteries, MR, 988.129411, 988.12943 • Arteries, stenosis or obstruction, 988.7214 • Echinococcosis, 38.2083, 988.2083
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Introduction
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Cystic echinococcosis caused by the parasite Echinococcus granulosus has worldwide distribution and poses a health problem in endemic areas, including large sheep-raising regions of Europe, Asia, the Mediterranean, South America, Australia, and New Zealand. The cysts produced by the disease frequently involve the liver and the lungs; however, they may be found in any organ, such as the brain, heart, or bones (1,2). Intravascular growth of hydatid cysts is an unusual manifestation of the disease. Here, we report the radiologic findings in a case of intraaortic growth of hydatid cysts due to recurrent hydatid disease following previous surgery.
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Case Report
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A 43-year-old woman presented with claudication of the lower limbs. The notable findings at physical examination included weak arterial pulses in both lower extremities and soft-tissue swelling of the back. She mentioned that she had been operated on for a paraspinal hydatid cyst 7 years ago. The result of an indirect hemagglutination test for E granulosus was positive in high (1/512) titers. Abdominal computed tomography (CT) demonstrated multiple unilocular and multilocular cystic lesions in the paraspinal muscles, gluteal muscles, psoas muscles, prevertebral retroperitoneal space, and adipose tissues of the back and gluteal area. The lesions detected at CT had low signal intensity on T1-weighted spin-echo magnetic resonance (MR) images (Fig 1a) and high signal intensity on T2-weighted spin-echo MR images (Fig 1b). The wall of the cysts and the septa within the multilocular cysts appeared to be hypointense on T2-weighted spin-echo images (Fig 1b).
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Figure 1a. (a) Left parasagittal T1-weighted spin-echo MR image (repetition time msec/echo time msec, 680/16) shows a prevertebral cystic mass (arrowheads). Note that the aorta (curved arrow) is cut off at the superior margin of the mass (straight arrow). The increased signal intensity within the aortic lumen proximal to the occlusion was attributed to pseudodiastolic gating and stagnation of blood flow. (b) Left parasagittal T2-weighted spin-echo MR image (1,800/80) shows that the wall of the prevertebral cystic mass (arrowheads) and the internal septa are hypointense relative to the cystic fluid.
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Figure 1b. (a) Left parasagittal T1-weighted spin-echo MR image (repetition time msec/echo time msec, 680/16) shows a prevertebral cystic mass (arrowheads). Note that the aorta (curved arrow) is cut off at the superior margin of the mass (straight arrow). The increased signal intensity within the aortic lumen proximal to the occlusion was attributed to pseudodiastolic gating and stagnation of blood flow. (b) Left parasagittal T2-weighted spin-echo MR image (1,800/80) shows that the wall of the prevertebral cystic mass (arrowheads) and the internal septa are hypointense relative to the cystic fluid.
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Moderate contrast enhancement was observed in the wall of the lesions on both the CT and MR images after intravenous administration of contrast material. The inferior vena cava was compressed and displaced anteriorly by a prevertebral cyst at the level of the fourth lumbar vertebra. The abdominal aorta appeared to be normal proximal to the level of the L2-3 intervertebral disk. However, at CT, a cystic lesion was detected in the lumen of the aorta at the level of the inferior endplate of the L2 vertebra (Fig 2a, 2b). Distal to this level, the aorta could not be demonstrated; instead, multilocular cysts were observed at the location of the aorta (Fig 2c) and the iliac arteries. The MR images also failed to show the aorta distal to the level of the L2 vertebra (Fig 1a). These findings suggested that the lumina of the distal aorta and the iliac arteries were occupied by multiple cysts. Findings at abdominal aortography (Fig 3) confirmed occlusion of the distal half of the abdominal aorta and of the common and external iliac arteries on both sides. The blood flow to the distal part of the external iliac arteries was reconstituted by collateral circulation.
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Figure 2a. (a, b) Sequential (from cranial to caudal) contrast material-enhanced axial CT scans (1-cm collimation) obtained through the level of the L2-L3 vertebrae. (a) The aortic lumen (arrow) appears to be normal at the level of the L2 vertebra. (b) Scan obtained below the level in a shows a low-attenuating lesion (arrow) occupying the aortic lumen. The contrast-enhanced peripheral rim represents the residual lumen. (c) Scan obtained below the level in b shows a multilocular cyst (arrows) at the aortic location.
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Figure 2b. (a, b) Sequential (from cranial to caudal) contrast material-enhanced axial CT scans (1-cm collimation) obtained through the level of the L2-L3 vertebrae. (a) The aortic lumen (arrow) appears to be normal at the level of the L2 vertebra. (b) Scan obtained below the level in a shows a low-attenuating lesion (arrow) occupying the aortic lumen. The contrast-enhanced peripheral rim represents the residual lumen. (c) Scan obtained below the level in b shows a multilocular cyst (arrows) at the aortic location.
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Figure 2c. (a, b) Sequential (from cranial to caudal) contrast material-enhanced axial CT scans (1-cm collimation) obtained through the level of the L2-L3 vertebrae. (a) The aortic lumen (arrow) appears to be normal at the level of the L2 vertebra. (b) Scan obtained below the level in a shows a low-attenuating lesion (arrow) occupying the aortic lumen. The contrast-enhanced peripheral rim represents the residual lumen. (c) Scan obtained below the level in b shows a multilocular cyst (arrows) at the aortic location.
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Figure 3. Aortogram shows abrupt occlusion (arrow) of the aorta at the level of the inferior endplate of the L2 vertebra.
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On the basis of the described findings, the diagnosis of secondary dissemination of hydatid disease to the soft tissues of the back, to the retroperitoneal space, and to the lumen of the aorta following previous surgery was made in this patient. The patient underwent surgery, during which it was noted that some hydatid cysts adherent to the aortic wall were compressing the aorta, whereas others were penetrating the aortic wall and protruding into its lumen. The distal half of the aorta was expanded by intraluminal cysts. Numerous cysts of a diameter ranging from a few millimeters to 3 cm were removed from the lumina of the aorta and iliac arteries.
Because the affected arteries were destroyed, an aortoiliac graft was placed to restore the blood flow to the lower extremities in the patient. Not all of the other cysts in the retroperitoneal space and paraspinal soft tissues could be removed, and adjuvant chemotherapy with albendazole (10 mg/kg daily) was started in the patient. The arterial pulses in the lower extremities returned to normal, and the claudication disappeared after surgery. However, no substantial change in the residual paraspinal cysts was observed on the follow-up MR images obtained 6 months after surgery.
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Discussion
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In humans, infection with E granulosus is caused by ingestion of the parasitic eggs, which are distributed widely in environments contaminated with infected dog feces. The eggs are absorbed in the intestine and migrate through either the portal venous system or lymphatic system. The migration of the eggs through either of these systems determines the future liver or lung location of the parasite (1). Involvement of organs other than the liver or lungs, which occurs when the eggs pass these two major filters, is encountered in 15% of patients (1,2). Involvement of the musculoskeletal system is seen in 1%–4% of cases (2). In the cardiovascular system, the heart—especially the myocardium—is the most frequently affected site; it harbors 0.5%–2.0% of all hydatid cysts (3).
Previous reports of the involvement of vessels include those of embolism of the germinative membranes caused by ruptured cardiac hydatid cysts (4), spontaneous or surgical rupture of a hydatid cyst into an adjacent vessel (5), and thrombosis of an artery and/or vein due to compression by hydatid cysts (6). To our knowledge, intravascular growth of hydatid cysts has been encountered in only one case before (7). In the latter case, intraluminal development of a hydatid cyst caused occlusion of a femoral artery. In the present case, secondary dissemination of hydatid disease after surgery led to the development of numerous cysts in the soft tissues of the back and in the retroperitoneal structures, including the lumina of the aorta and of both iliac arteries. Although secondary dissemination is a well known complication of surgery for hydatid cyst removal, growth of hydatid cysts in the lumen of such large arteries, to the best of our knowledge, has not been reported before.
A hydatid cyst is composed of an endocyst and a pericyst. The endocyst surrounds clear, mineral-like water and is made of two layers—the germinative and laminated membranes. The pericyst is composed of reactive host cells and may be very thin or absent in loose tissues or in hollow viscera (1). Because the endocyst is very fragile and loosely attached to the host tissue, it is unusual for a hydatid cyst to settle in an arterial lumen without being ruptured or dragged by the pulsatile flow. In the present case, the aorta, which is the largest artery of the body, and both iliac arteries were occluded by hydatid cysts. It is probable that a substantial decrease in aortic flow due to the compression by the extraluminal retroperitoneal cysts accompanied the penetration of the aorta and invasion of its lumen by the hydatid cysts. Further intraluminal growth of numerous hydatid cysts led to occlusion of the distal half of the abdominal aorta and of both iliac arteries.
The imaging findings of cystic echinococcosis have been well documented in the literature (2,8,9). Regardless of where the hydatid cysts are located, ultrasonography (US), CT, or MR imaging demonstrates well-defined single or multiple cysts that may be uniloculated or multiloculated and either thin or thick walled. The cyst fluid appears anechoic at US, yields an attenuation value of 3–30 HU at CT, and shows signal intensities similar to that of water at MR imaging. Calcification may be present in the cyst wall and is best detected on CT scans. The cyst wall and the septa in multilocular cysts are isointense relative to the cyst fluid on T1-weighted MR images and appear as a low-signal-intensity rim surrounding the cyst fluid on T2-weighted MR images. The cyst wall and septa may enhance after intravenous administration of gadopentetate dimeglumine. All of the above mentioned imaging findings were observed in the present case. The case of occlusion of the aorta and iliac arteries due to intraluminal growth of hydatid cysts described herein is presented to acquaint radiologists with this unusual vascular manifestation of cystic echinococcosis.
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Footnotes
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Author contributions: Guarantor of integrity of entire study, B.H.; study concepts and design, S.M.; definition of intellectual content, S.M.; literature research, C.Y.; clinical studies, T.E.; data acquisition, T.R.E.; data analysis, C.Y.; manuscript preparation and editing, S.M.; manuscript review, B.H.
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References
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Abstract
Introduction
