Cystic Adventitial Disease (CA

Discussion on Cystic Adventitial Disease of the Popliteal Artery

What is Cystic Adventitial Disease (CAD)? CAD is a collection of gelatinous fluid in the tunica adventitia layer of a blood vessel wall. The fluid progressively accumulates in this layer eventually causing a localized narrowing in the vessel lumen. The gradual narrowing becomes a significant stenosis or occlusion resulting in arterial insufficiency distal to the affected artery. The stenosis is not a result of atherosclerotic changes. In fact, CAD characteristically occurs in young men (fourth or fifth decade) presenting with intermittent claudication in the absence of atherosclerosis. CAD is rarely found to be bilateral, or part of another systemic disorder. Right and left legs are equally affected. The cysts are filled with clear or yellow (currant jelly appearance) fluid and can vary in length, averaging approximately 1 to 8 cm (up to 13 cm have been reported). The cysts can be uniloculated or multiloculated and can be adherent to adjacent structures such as veins or nerves. 

The popliteal artery is the most common site for CAD, however, it has been diagnosed in other arteries such as the iliac, femoral, radial, ulnar, and brachial. Furthermore, the locations of the cyst in these arteries have been adjacent to joint spaces, such as the hip, wrist and elbow. In many cases, there is an anatomical connection between the cyst and the adjacent joint capsule. CAD is not entirely limited to arteries. Veins in the legs such as the external iliac, femoral, popliteal and saphenous have also been reported. 

CAD has been referred to by other names, such as: cystic adventitial degeneration, cystic mucoid degeneration, cystic myxomatous adventitial degeneration, mucinous cystic dissecting intramural degeneration, and subadventitial pseudocyst.

Different stages of progression of cystic adventitial disease.

Different arteriographic appearances of cystic adventitial disease.
(Modified from Ishikawak: cystic adventitial disease of the popliteal artery. Jpn j surg 17:227, 1987)

Etiology: The exact etiology of CAD is unknown, however, the following four theories have been reported to be possible causes of CAD: 
1) Systemic disorder theory
2) Repetitive trauma theory
3) Ganglion theory
4) Developmental theory

The systemic disorder theory was proposed by Linquette et al (1967) based on an abnormal skin biopsy. This theory has the least support due to the fact that long-term follow-up has failed to reveal a systemic condition of CAD. 

The repetitive trauma theory suggests that because of the popliteal’s close proximity to the knee joint, it undergoes repeated trauma causing destruction and degeneration of the adventitial layer. Small detachments of the adventitial layer from the media layer cause intramural bleeds, resulting in cystic formation. Additions to this theory suggest connective tissue changes cause cells to secrete a substance that forms a cyst. This theory fails to explain why there is no predominance of CAD in athletes and laborers, who sustain more physical stress and trauma to the popliteal fossa than the general population. Even those with the disease rarely report repeated trauma.

The ganglion theory is supported by the fact that adventitial cysts have been reported to be biochemically and histologically similar to ganglia. The proposed process occurs because the cysts arise from synovial structures and track along vascular branches to the adventitia of the adjacent major vessel. 

The developmental theory suggests mucin secreting cells derived from the mesenchyme of adjacent joints are misplaced into the adventitial layer of nearby arteries or veins during development. The cells at some time later in life begin to actively secrete fluid into the adventitial layer. 

Interestingly, the etiology may be a combination of the ganglion and developmental theories. Joint related ganglion may be integrated into the vessel wall during embryonic development while still maintaining a communication with a synovial structure. This is supported by those CAD cases that have reported a connection or stalk between the cyst and the joint space. 

Signs and Symptoms: The typical patient is a male (15:1 ratio) in his mid forties presenting with a sudden onset of intermittent claudication. Reported cases have shown patients as young as 10 and as old as 77 with a mean age of 45 years. The degree of lumen narrowing and collateralization dictate the severity of the claudication. Typically the progression of claudication is fairly quick (occurring within weeks) and can be severe, limiting walking to less than a block. Further progression of the disease can lead to ischemic neuropathy causing parethesis, burning pain, or coldness. Patients can have decreased or absent pedal and popliteal pulses. Distal pulses may be present, however, upon acute knee flexion the pulses disappear. A bruit may be heard in the popliteal fossa. Blood pressures in the ankles may appear normal at rest; but post exercise, these pressures drop suggesting a significant arterial stenosis. 

Diagnosis: Intermittent claudication in a young male with no risk factors for atherosclerotic disease should heighten the clinical suspicion of CAD. Several tests can be performed to identify the problem. A measure of the ankle pressure compared to the brachial pressure pre and post exercise can identify that there is, in fact, arterial insufficiency present. Resting ABI (ankle/brachial index) may be normal, but the ABI will drop significantly post exercise.

A duplex arterial ultrasound evaluation of the popliteal fossa can locate the exact site of the cyst. The size (variable), shape (round, oval, sausage like, etc.), contour (smooth), content (fluid = anechoic, uniloculated vs. multiloculated) and number of cysts can be determined. Ultrasound should be able to detect the absence of atherosclerotic disease and differentiate between the perivascular cyst and aneurysmal development. Color Doppler imaging demonstrates a lumen reduction with a mosaic of colors characteristic of aliasing in the area of the lumen narrowing. Power Doppler may be useful for more clearly outlining the reduced size of the lumen. Doppler analysis displays an elevation of velocities in the narrowed section of the lumen and when compared to velocities in a normal proximal segment, a ratio can be obtained to quantify the degree of stenosis. Distal to the stenosis, the hemodynamic flow may change from a high resistant (tri or biphasic) waveform to a low resistant (monophasic) waveform. However, the distal waveforms may remain high resistant depending on the severity of the lumen reduction and the amount of collateral flow present. 

Angiography can clearly demonstrate the degree of stenosis using both anteroposterior and lateral views. The vessel is typically lacking any atherosclerotic changes with few marginal irregularities. The narrowing is seen as having a smooth tapered appearance. Depending on the shape and location of the cyst, several angiographic appearances have been described. They are scimitar, hourglass, flute embouchure, m-shaped or a triangular filling defect. The most common appearance is that of the scimitar. Aneurysm development and post stenotic dilatation is not seen in CAD. 

Computed tomography with angiographic contrast (CT Angio) has the advantage of not only outlining the vessel lumen but also displaying the tissue characteristics of the perivascular lesion (i.e. cystic, solid, complex). The angiographic appearance using CT is very similar to conventional angiography. CT can also show circumferential involvement with axial images. A complete understanding of the relationship between the cyst to the artery and the severity of lumen reduction is obtained.

Magnetic resonance imaging (MRI) can be used to both image the cyst and determine degree of stenosis. There appears little evidence that MRI is superior to other forms of imaging for the diagnosis and planning of therapy of CAD (Rutherford, 2000).

Differential Diagnosis: The differential diagnosis of CAD of the popliteal artery includes: popliteal aneurysm, Baker’s cyst, atherosclerotic stenosis in popliteal artery, and false aneurysms. True aneurysms are a dilatation of all three layers of the vessel wall. CAD affects only the external layer leaving the internal layer uninterrupted. A fine echogenic line can be seen with ultrasound separating the cyst from the internal layer of the vessel. A Baker’s cyst is not found adjacent or connected to the popliteal artery. Rather, it lies more medial and closer to the knee joint. The tunica intima rarely undergoes atherosclerotic changes and can be seen intact in most cases. False aneurysms lie completely outside the vessel wall connected to the lumen by a neck. Blood flow is usually seen in the false aneurysm and is never present in the cysts of CAD. CAD is not a vascular mass.

Treatment: A conservative approach to treating CAD is percutaneous cyst aspiration under ultrasound or CT guidance. This procedure has immediate success in eradicating the fluid and restoring normal luminal caliber, but has been prone to early recurrence of the fluid and subsequent vessel stenosis. The secretory lining of the cyst remains allowing for the rapid reaccumulation of fluid. Cyst aspiration rarely provides a long-term successful solution to CAD of the popliteal artery (Sieunarine, et al, 1991)

Transluminal angioplasty (TLD) is not an effective method because the intima of the vessel is not affected in CAD. Ballooning this area will not change the intrinsic pressure the vessel lumen is under due to the cyst. 

A more aggressive option is usually required to successfully treat CAD. Surgical cyst evacuation is currently the preferred treatment if the artery has not become occluded (Rutherford, 2000). This requires incision into the cyst and evacuation of the fluid without disturbing the medial and internal layers of the vessel wall. If the integrity of the vessel wall is compromised, a vein or synthetic patch may be required to repair it. Another surgical option is complete resection of the affected popliteal artery. The section of artery removed is replaced end to end with a length of the long or short saphenous vein. This particular method is required in those patients with complete occlusion of the popliteal artery. Due to the rarity of this disease, there still remains no standardized method of surgical intervention. Some centers prefer cyst evacuation, while others are comfortable with complete resection with bypass grafts with or without complete occlusion. Regardless, surgical intervention remains a successful treatment for CAD. 

Glossary

 

References/Further Reading

Books
1. Rutherford RB: Vascular Surgery, 5th ed. Philadelphia, WB Saunders, 2000, pp. 1079-1087.

2. Bartholomew JR, Olin JW, and Young JR: Peripheral Vascular Diseases, 2nd ed. St. Louis, Mosby, 1996, pp. 429-431.

Articles

1. Heiderer JE, Jain JKA, Abramo AA, et al. Using the noninvasive vascular laboratory to identify and evaluate adventitial cystic disease of the popliteal artery. J Vasc Tech. 25(4):232-234, 2001.

2. Levien L, Benn C. Adventitial cystic disease: a unifying hypothesis. J Vasc Surg. 28(2):193-205, 1998.

3. Galle C, Carvenaile J, Hoang A, et al. Adventitial cystic disease of the popliteal artery communicating with the knee joint. J Vasc Surg. 28:738-741, 1998.

4. Miller A, Salenius J, Sacks B, Gupta S, Shoukimas G. Noninvasive vascular imaging in the diagnosis and treatment of adventitial cystic disease of the popliteal artery. J Vasc Surg. 26:715-720, 1997.

5. Stapff M, Zoller WG, and Spengel FA: Image-directed Doppler ultrasound findings in adventitial cystic disease of the popliteal artery. J Clin Ultrasound 17:689, 1989.

6. Chiche L, Baranger B, Cordoliani TS, et al: Two cases of cystic adventitial disease of the popliteal artery: Current diagnostic approach. J Mal Vasc, 19:57.1994

7. Cholet M, Rousseau H, Ferro P, et al: Adventitial cyst of the popliteal artery: Imaging and percutaneous treatment. J Radiol 77:201, 1996.

8. Ward AS, and Reidy JF: Adventitial cystic disease of the popliteal artery. Clin Radiol 38:639, 1987.

9. Riviere J, Soury P, Poli P, et al: Importance of complementary preoperative examinations in the treatment of adventitial cystic degeneration of the popliteal artery. J Mal Vasc 19:251, 1994.

10. Schaberle W, and Eisele R: Ultrasound diagnosis, follow-up and therapy of cystic degeneration of the adventitia: 2 case reports and review of the literature. Ultraschall Med 17:131, 1996.

11. Saeed M, Wolf YG, and Dilley RB: Adventitial cystic disease of the popliteal artery mistaken for an endoluminal lesion. J Vasc Interv Radiol 4:815, 1993.

12. Sieunarine K, Lawrence-Brown M, Kelsey P: Adventitial cystic disease of the popliteal artery: Early recurrence after CT guided percutaneous aspiration. J Cardiovasc Surg 32:702, 1991.

Related Web Sites

www.rcsed.ac.uk/journal/vol44_2/4420014.htm
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