title: Hepatic artery stenosis following liver transplantation: significance of the tardus parvus waveform and the role of microbubble contrast media in the detection of a focal stenosis.
abstract: OBJECTIVE
  To evaluate the role of microbubble ultrasound contrast media in detecting stenosis of the post-liver transplant extrahepatic hepatic artery (HA) in the presence of the tardus parvus spectral Doppler waveform of the intrahepatic HA.
  
  
  METHODS
  All post-liver transplant patients with a prolonged systolic acceleration time (SAT>0.08s) and/or a reduced resistant index (RI<0.50) of the HA (the tardus parvus waveform) on colour Doppler ultrasound (CDUS), were assessed with microbubble contrast medium for a focal arterial stenosis. Following microbubble contrast-enhanced CDUS, patients underwent arteriography or follow-up CDUS.
  
  
  RESULTS
  A total of 2038 examinations were performed in 529 liver transplant recipients; 16 (3.02%) tardus parvus waveforms were identified. The median SAT of the intrahepatic HA was 0.18s (range 0.11-0.38s) and the RI 0.47 (range 0.22-0.58). No extrahepatic elevated peak systolic velocity (PSV), defined as above 1.00m/s, was detected on the baseline examinations. Following the administration of microbubble contrast, medium, PSV in the extrahepatic HA was elevated in 14 of 16 patients, (median=2.15m/s, range=1.44-3.10m/s); flow was not identified in two patients. Arteriography was performed in 10 patients and confirmed stenosis in eight (median grade of stenosis 93%, range 60-99%) and occlusion in two. The measured median PSV at contrast-enhanced CDUS in the stenosis group was 2.03m/sec (range 1.44-2.71m/sec). Repeat CDUS in six patients not undergoing arteriography showed resolution in four; one underwent re-transplantation before arteriography and one patient maintains a tardus parvus waveform. In transplant recipients undergoing arteriography during the study period (n=55), no hepatic artery stenosis without a tardus parvus waveform was seen.
  
  
  CONCLUSIONS
  The tardus parvus waveform pattern is an excellent screening test for the presence of post-liver transplantation hepatic artery stenosis. There is only a limited role for microbubble ultrasound contrast agent in the presence of a tardus parvus waveform. It could be used following equivocal colour Doppler ultrasound, but arteriography will still be necessary.
authors.affiliation: Department of Diagnostic Radiology, King's College Hospital, London, UK. paulsidhu@compuserve.com
authors.forename: P S
authors.initials: PS
authors.lastname: Sidhu
authors.forename: S M
authors.initials: SM
authors.lastname: Ellis
authors.forename: J B
authors.initials: JB
authors.lastname: Karani
authors.forename: S M
authors.initials: SM
authors.lastname: Ryan
mesh_terms: D000293:Adolescent; D000328:Adult; D001157:Arterial Occlusive Diseases / Q000000981:diagnostic imaging*; D003287:Contrast Media; D005260:Female; D006499:Hepatic Artery / Q000000981:diagnostic imaging*; D006801:Humans; D016031:Liver Transplantation / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011134:Polysaccharides; D011183:Postoperative Complications / Q000000981:diagnostic imaging*; D011446:Prospective Studies; D011859:Radiography; D018615:Ultrasonography, Doppler, Color
chemical_list: D003287:Contrast Media; D011134:Polysaccharides; C059891:SHU 508