Pediatr Radiol (1997) 27: 327–329 Springer-Verlag 1997
Wall enhancement of leaking polytetrafluoroethylene grafts: a new CT sign
A. Michelle Fink Michael R. Ditchfield
Received: 12 December 1995 Accepted: 10 February 1996
)
A. M. Fink ⋅ M. R. Ditchfield ( ) Department of Radiology, Royal Children’s Hospital, Flemington Road, Parkville, Victoria 3052, Australia
Abstract Perigraft seroma is a rare complication of synthetic vascular grafts. We describe a new sign observed in two children who underwent computed tomography of the chest for further evaluation of seromas complicating modified BlalockTaussig procedures in which a polytetrafluoroethylene graft was used. In both patients contrast enhance-
Introduction The use of synthetic grafts for vascular anastamoses has become commonplace in vascular surgery. Complications of these procedures include the accumulation of well-demarcated serous collections around the grafts. We describe the pattern of graft wall enhancement on computed tomography (CT) in two patients with leaking grafts and perigraft seromas complicating modified Blalock-Taussig (B-T) procedures using polytetrafluoroethylene (PTFE) grafts.
Case reports
ment of the wall of the leaking graft was demonstrated on delayed imaging. One patient had bilateral grafts, and the enhancement was only demonstrated in the wall of the leaking graft. We discuss the possible mechanism of this finding and propose that this sign may be further evidence of abnormal graft permeability.
Case 2 A boy with Noonan’s syndrome was born prematurely at 33 weeks of gestation with pulmonary atresia and intact ventricular septum. A balloon atrial septostomy was performed on day 1 of life, followed by a modified right B-T shunt using a PTFE graft at the age of 6 weeks. Prolonged intravenous therapy led to superior vena cava occlusion which made a cavo-pulmonary connection unfeasible. Due to increasing cyanosis a second (left) modified B-T shunt was performed at 4 months. Leakage from this latter shunt produced a large serous pleural effusion which reaccumulated after percutaneous drainage. CT 2 weeks after surgery, performed before and after intravenous contrast medium administration (Fig. 2), again demonstrated a non-enhancing fluid collection surrounding the left graft, with delayed contrast enhancement of the wall of this graft. There was no delayed enhancement of the right graft, which was not leaking.
Case 1 A girl born at term with severe cyanosis secondary to a tetralogy of Fallot had a modified right B-T shunt using a PTFE graft at the age of 3.5 months. Six weeks following surgery she presented with cough and tachypnoea. She was afebrile, but a chest radiograph (CXR) demonstrated a new right upper zone opacity. CT performed before and after administration of intravenous contrast material (Fig. 1) showed the opacity to be a well-demarcated fluid attenuation collection surrounding the B-T shunt. Although the collection did not enhance either immediately or on delayed imaging, persistent enhancement of the wall of the graft on the delayed images was noted.
Discussion Perigraft seroma is a rare complication of synthetic vascular prostheses. Initially described in systemic vascular grafts, it is also well recognised following modified B-T procedures using PTFE grafts. The incidence has been reported as 6.8–9.5 % following peripheral grafts [1]. Excessive serous fluid leakage through the walls of the graft has been reported in 18.8 % of modified B-T shunts, with radiological changes in half of the cases
328
a
Fig. 1 a–c Case 1: axial CT images at the level of the main pulmonary artery; a region of interest cursor is positioned over the perigraft seroma (AA ascending aorta, L left, MPA main pulmonary artery). a The right Blalock-Taussig (B-T) shunt is demonstrated (arrow) prior to contrast enhancement. b During dynamic contrast enhancement, the B-T shunt is patent (arrow) and there is no enhancement of the seroma. c Seven minutes later there is enhancement of the shunt wall (arrow); there is no enhancement of the seroma, but some vascular enhancement is still seen
[2]. Gross examination of seromas shows a thin pseudocapsule encasing a serous fluid collection that bathes the prosthetic graft. The fluid is clear, sterile, acellular and of the same chemical composition as serum. The few reports of the histology of the abnormal grafts are conflicting. Blumberg et al. [3] describe the leaking segment of graft as being coated by thin fibrous tissue with an acellular thin fibrin matrix within its wall, whereas the normal part of the graft is encompassed by adherent fibrous tissue with collagen surrounded by occasional fibroblasts, neutrophils and erythrocytes in its wall. The paucity of inflammatory cells was notable in their series of nine grafts examined. Ahn et al. [4] had histological specimens of two leaking grafts and, conversely, found them to be lined by abundant chronic inflammatory cells, mainly giant multinucleated foreign body cells, and a sparse lattice of immature fibroblasts. Serous leakage through synthetic grafts occurs by ultrafiltration of serum through the mesh of the synthetic material. The cause of this remains unclear, but allergic response, “foreign body reaction”, humoral fibroblast inhibitors, “graft wetting” and graft stretching and bending have all been implicated [3–5].
b
c
Imaging is a useful part of the diagnostic work-up of perigraft seromas. In modified B-T shunts an upper mediastinal mass is the most common finding on the CXR, and can be difficult to differentiate from a haematoma, aneurysm [2] or even a mediastinal tumour [6]. Sonography will confirm the cystic nature of the lesion [1, 7, 8]. We found three previous reports of CT imaging in perigraft seromas [1, 6, 9]. Although Scherer et al. [1] state in their discussion that the lack of ring enhancement of the periphery of the collection favours the diagnosis of seroma over infection, none of the other authors comment on the enhancement pattern of perigraft seromas. Enhancement of the graft wall has not previously been documented. It is of interest that in the patient with bilateral B-T shunts, delayed graft wall enhancement was only observed in the graft through which the serum was leaking. We can only speculate on the mechanism involved in this observation. It would, however, seem to support the theories that invoke an inflammatory aetiology, be it immunologically mediated or not, for the abnormal permeability of leaking grafts. The presence of inflammatory cells lining the wall of these grafts as seen by Ahn
329
a
b
Fig. 2 a–c Case 2: axial CT images at the level of the aortic arch (Ao). The left serous effusion (E) is visible and the left lung is collapsed (L left). a The two B-T shunts are demonstrated (arrows) prior to contrast enhancement. b During dynamic contrast enhancement, both B-T shunts are patent (arrows) and there is no enhancement of the effusion. c Five minutes later there is still enhancement of the shunt wall on the left (arrow), but not on the right (arrowhead) and there is no enhancement of the effusion
et al. [4] would further explain the persistent contrast enhancement of these structures. In conclusion, the diagnosis of serous leakage from a prosthetic vascular graft should be possible on the basis of clinical and imaging findings. We have described two
c
patients with leaking B-T shunts in whom delayed contrast enhancement of the graft wall was observed on CT. We propose that delayed graft wall enhancement on CT provides further evidence of abnormal graft permeability with serous transudation.
References 1. Scherer G, Roeren T, Paetz B, Hupp T, Kauffmann GW (1995) Sonographische und computertomographische Befunde bei Perigraftreaktionen nach operativer Implantation von Gefa¨ßprothesen. Fortschr Geb Rontgenstr Neun Bildgeb Verfahr 162: 46–50 2. LeBlanc J, Albus R, Williams WG, Moes CAF, Wilson G, Freedom RM, Trusler GA (1984) Serous fluid leakage: a complication following the modified BlalockTaussig shunt. J Thorac Cardiovasc Surg 88: 259–262 3. Blumberg RM, Gelfand ML, Dale WA (1985) Perigraft seromas complicating arterial grafts. Surgery 97: 194–203
4. Ahn SS, Machleder HI, Gupta R, Moore WS (1987) Perigraft seroma: clinical, histologic, and serologic correlates. Am J Surg 154: 173–178 5. Kaupp HA, Matulewicz TJ, Lattimer GL, Kremen JE, Celani VJ (1979) Graft infection or graft reaction? Arch Surg 114: 1419–1422 6. Verhaaren HA, Hessmann M, Logghe K, Kunnen M, Derom F (1988) Abnormal leakage of serous fluid through the wall of vascular prosthetic material causing a tumor-like mass in the posterior part of the mediastinum. J Belge Radiol 71: 687– 689
7. Wolson AH, Kaupp HA, McDonald K (1979) Ultrasound of arterial graft surgery complications. Am J Roentgenol 133: 869–875 ¨ zkutlu S, O ¨ zbarlas N, Demircin M 8. O (1992) Perigraft seroma diagnosed by echocardiography: a complication following Blalock-Taussig shunt. Int J Cardiol 36: 244–246 9. Rudd SA, McAdams HP, Chen AJ, Midgley FM (1994) Mediastinal perigraft seroma: CT and MR imaging. J Thorac Imaging 9: 120–122