- Email: [email protected]
Hepatic artery aneurysms: Evaluation using three-dimensional spiral CT angiography
Clinical Radiology (1997) 52, 227-230
Hepatic Artery Aneurysms: Evaluation Using Three-dimensional Spiral CT Angiography S. J. H O W L I N G , H. GORDON*, T. M c A R T H U R , A. H A T F I E L D * and W. R. LEES
Departments of Radiology and *Gastroenterology, The Middlesex Hospital, UCL Hospitals Trust, Mortimer St, London, WIN 8AA Hepatic artery aneurysms are rare and frequently difficult to diagnose. Computed tomography (CT) and ultrasound rarely make the definitive diagnosis and angiography is usually required. We present three cases of hepatic artery aneurysms in which the definitive diagnosis was made on three-dimensional (3-D) spiral CT angiography-to our knowledge, this has not previously been described. Our experience shows that in many cases of hepatic artery aneurysm, conventional angiography need only be performed as a prelude to embolization. Howling, S. J., Gordon, H., McArthur, T., Hatfield, A. & Lees, W. R. (1997). Clinical Radiology 52, 2 2 7 - 2 3 0 . Hepatic Artery Aneurysms: Evaluation Using Threedimensional Spiral CT Angiography
Accepted for Publication 6 August 1996
Hepatic artery aneurysms are rare. Eighty per cent of patients present acutely with aneurysm rupture, with an attended high mortality [1]. Diagnosis is difficult and often delayed, owing to the non-specific symptoms and lack of clinical findings. Conventional cross-sectional imaging techniques (CT and ultrasound) often reveal the presence o f an aneurysm, but the artery o f origin is not always clear and angiography is still necessary. W e report three cases o f hepatic artery aneurysm in which the definitive diagnosis was established using 3-D spiral CT angiography. Although conventional angiography was subsequently performed, our experience suggests that in most cases of hepatic artery aneurysm conventional angiography need only be performed as a prelude to embolization. To our knowledge these are the first reported cases of hepatic artery aneurysm to be investigated with 3-D spiral CT angiography.
were established on the basis of a review of individual sections. The resultant m o d e l could be rotated 360 (and orientated in any manner allowing accurate determination of 3-D spatial relations. Quasi-surgical techniques allowed removal of unwanted structures and overlapping vessels. Simultaneous 2-D multiplanar reformatting was possible at any level, providing additional information on intimal calcifications and mural thrombus. The CT angiography models were interpreted by a consultant radiologist prior to and without the knowledge of conventional angiographic findings. Observers were asked specifically to comment on the exact location of the aneury s m and on variant anatomy. Subsequently, the two studies were correlated, with arterial angiography as the reference standard. The 3-D reconstruction and analysis required an average o f 30 min extra operator time.
CASE REPORTS
PATIENTS AND METHODS Three patients (details below) with suspected visceral artery aneurysms were examined by 3D-spiral CT angiography prior to conventional angiography. The spiral CT was performed on a GE Prospeed CT scanner. Pre-contrast, contiguous 10 m m axial slices were obtained to localize the volume o f interest. Serial imaging of a 10 ml contrast bolus injected at 5 ml/s, with CT images obtained at the cephalad extent of the volume of interest was used to generate a timedensity curve to plan optimal vascular opacification. A total of 120 ml of non-ionic contrast m e d i u m (350 mg I/ml) was then infused intravenously at 5 ml/s and 5 m m axial contiguous slices obtained and reconstructed at an interval o f 2.5 mm. 3-D reconstruction of the data obtained was performed on a U C L Medical Graphics Workstation (UCL Medical Imaging, London, UK) to generate a multi-threshold shadedsurface display image. Shaded-surface display thresholds Correspondence to: Dr S J Howling, Department of Radiology, The Middlesex Hospital, Mortimer St, London, WIN 8AA, UK. © 1997The RoyalCollegeof Radiologists.
Case 1. A 67-year-old man was referred from a local hospital for CT guided biopsy of an 8 cm, enhancing, calcified, pancreatic mass that had been detected on conventional contrast enhanced CT scans. He gave a 3year history of increasing, non-specific, intermittent epigastric pain radiating to the back, but was otherwise well and physical examination was unremarkable. Ultrasound examination demonstrated an 8 x5 cm cystic mass adjacent to the head of the pancreas, which itself appeared normal. Doppler interrogation demonstrated a typical arterial waveform within the cyst; and a visceral artery aneurysm was suspected. A 3-D spiral CT angiogram was performed. The spiral CT scans confirmed the presence of an 8 cm diameter, heavily calcified aneurysm within the porta hepatis. The exact artery of origin was unclear on sectional images. The 3-D reconstruction showed a large solitary aneurysm clearly arising from the proximal common hepatic artery (Fig. 1), with a stenosis at the origin of the aneurysm. The hepatic artery emerging from its distal end divided almost immediately into the right and left hepatic arteries. An accessory right hepatic artery originated from the coeliac axis to pass inferior to the aneurysm. The gastroduodenal artery originated from the left hepatic artery and passed anterior to the aneurysm. The superior mesenteric artery was normal. Selective angiograms of the coeliac axis and superior mesenteric arteries confirmed the 3-D spiral CT findings (Fig. 2). No additional arterial abnormalities were seen.The aneurysm was felt suitable for transcatheter embolization, which was performed using tungsten coils and Gelfoam.
228
CLINICAL RADIOLOGY
Fig. 1 - 3-D spiral CT angiogram (shaded-surface model) demonstrating a large solitary anenrysm (AN) arising from the proximal common hepatic artery (CH). The hepatic artery emerging from its distal end divides almost immediately into right (RH) and left (LH) hepatic arteries. The gastroduodenal artery (G) originates from the left hepatic artery and passes anteriorly to the aneurysm. The origin of an accessory right hepatic artery (AR) is demonstrated at the coeliac axis. The continuation of this vessel, which passes inferiorly to the aneurysm has been edited out. Portal vein (P) compressed by the aneurysm sac (confirmed on 2-D multiplanar views). Splenic artery (S).
Fig. 3 - 3-D spiral CT angiogram (shaded-surface model) demonstrating a single aneurysm (AN) of the common hepatic artery (CH) arising just proximal to the origin of the gastroduodenal artery (G). Superior mesenteric artery (SMA), fight (RH) and left (LH) main hepatic arteries.
Fig. 2 - Conventional selective coeliac axis angiogram confirming the origin of the aneurysm as the common hepatic artery.
Post embolization arterial angiography showed successful obliteration of the aneurysm and a repeat ultrasound examination after 3 months confirmed thrombosis of the aneurysm with no residual Doppler flow, at which time the patient was completely well with no abdominal pain. Case 2. A 19-year-old woman with polyarteritis nodosa presented with a one month history of increasing lethargy and intermittent abdominal pain. Examination was nnremarkable. Pertinent laboratory findings included an ESR of 96mm/h (<17mm/h) and a C-reactive protein of 109mg/1 (< 12 mg/l). An abdominal ultrasound was normal. An enhanced spiral CT was subsequently performed and demonstrated a 1 cm × 1 cm aneurysm, apparently arising from the common hepatic artery. 3-D spiral CT angiography confirmed the single, non-calcified aneurysm to arise from the common hepatic artery, proximal to the origin of the gastroduodenal artery (Fig. 3). No mural thrombus was detected on the 2-D multiplanar views. No variants of vascular anatomy were demonstated. Conventional angiography confirmed these findings (Fig. 4). In view of the active disease indicators the patient was given intravenous methylprednisolone and cyclophosphamide and the abdominal pain settled. The patient remains under regular review with no active treatment for the hepatic artery aneurysm. Case 3. A 58-year-old woman was referred from her local hospital, where she had presented with a 2-week history of nausea and progressive jaundice. Biochemistry revealed a serum bilirubin of 171/zmol/1 with a
Fig. 4 - Conventional selective coeliac axis angiogram providing confirmation of the aneurysm arising from the common hepatic artery.
cholestatic pattern. Ultrasound examination demonstrated a 3-cm diameter cystic lesion in the uncinate process of the pancreas, but normal liver and biliary tree. A spiral CT scan was performed a week later, by which time her symptoms had resolved and biochemistry had returned to normal. The CT study, however, revealed a 3 cm heavily calcified aneurysm inferior to the head of the pancreas, which itseff appeared normal. The aneurysm seemed to originate from a branch of the superior mesenteric artery (SMA). A second, smaller aneurysm arose from the fight hepatic artery. 3-D spiral CT angiography demonstrated a variant of normal visceral arterial anatomy with an accessory right hepatic artery arising from the SMA. A 3-cm aneurysm originated from the accessory right hepatic artery © 1997 The Royal College of Radiologists, Clinical Radiology, 52, 227-230.
HEPATIC ARTERY ANEURYSMS
Fig. 5 - 3-D spiral CT angiogram (shaded-surface model) demonstrating a normal anatomical variant with an accessory right hepatic artery (AR) arising from the superior mesenteric artery (SMA). A large aneurysm (AN) arises from the proximal accessory right hepatic artery with a further smaller aneurysm arising more distally (AN). Rotation of the model demonstrates this relationship more clearly and reveals absence of the coeliac trunk. Splenic artery (S). Common hepatic artery (CH) which is projected over the aneurysmal accessory right hepatic artery in this view.
with a further 1 cm aneurysm arising from the same vessel more distally (Fig. 5). Rotation of the model revealed absence of the coeliac trunk. Conventional angiography with selective cannnlation of the SMA confirmed the position of the aneurysms and the accuracy of the 3-D model (Fig. 6) with filling of the coeliac axis territory via enlarged vessels around the pancreatic head. A lateral aortogram confirmed true absence of the coeliac trunk. At operation the accessory right hepatic artery was ligated following excision of the aneurysms. The patient remains well 1 month post-operatively.
DISCUSSION Hepatic artery aneurysms are rare, but frequently fatal [2]. They constitute 20% of visceral artery aneurysms with only those of the splenic artery being more common [2]. Eighty per cent of hepatic artery aneurysms are extrahepatic and of these, 63% affect the common hepatic artery, 28% the right hepatic artery, 5% the left hepatic artery and 4% both the right and left hepatic arteries [2-5]. Lesions may be single or multiple and have been reported in patients from 10 to 93 years of age with a mean age of approximately 40 years [2,3,6]. The aetiology of hepatic artery aneurysms, thought to be exclusively mycotic prior to the advent of antibiotics is now more commonly atherosclerosis (an associated factor in 32%) or medial degeneration (found in a further 24%). Less common causes include polyarteritis nodosa, tuberculosis, © 1997 The Royal College of Radiologists, Clinical Radiology, 52, 227-230.
229
Fig. 6 - Conventional selective superior mesenteric artery angiogram confirms the 3-D spiral CT findings.
inflammation of the biliary tree and trauma, including iatrogenic trauma from biliary surgery and radiological interventional procedures [2,7] Clinical presentation tends to be variable and non-specific with fewer than one-third of patients presenting with the classical triad of abdominal pain, haemobilia and obstructive jaundice [1]. Eighty per cent of hepatic artery aneurysms are not detected until they rupture, either into the peritoneal cavity (43%), biliary tree (41%), gastro-intestinal tract (11%) or portal vein (5%), with resultant haemoperitoneum, haemobilia or haematemesis [1,8,9]. Rupture carries a high associated mortality. Short of this catastrophic presentation, 70% of patients complain of epigastric or right upper quadrant pain, which occasionally radiates to the back or right shoulder [1,2]. Jaundice due to an intraductal clot or biliary tree compression is seen in 50% of cases [8]. Physical signs are rare, but may include a palpable mass, bruit or hepatomegaly [1,2,10]. Radiological diagnosis of hepatic artery aneurysm is also difficult. Conventional imaging has little to offer. Ultrasound and CT are frequently misleading because of a tow index of suspicion, as highlighted by cases 1 and 3. Even when intravenous contrast enhancement or colour flow Doppler reveal the vascular nature of the mass, the exact site of origin is rarely demonstrated [7,11 ]. Angiography has therefore remained essential to confirm the diagnosis, delineate feeding vessels and provide the anatomical information required for surgery. The technique of 3-D spiral CT angiography has already been successfully employed in the assessment of renal and mesenteric artery stenoses, abdominal aortic dissections and abdominal aortic aneurysms [12,13]. These studies used
230
CLINICAL RADIOLOGY
single threshold, shaded-surface display models. These display pixels with a CT number above a selected threshold. All pixels below the threshold are set to zero and are not displayed in the 3-D image. Grey-scale encodes a surface rendering, based on a computer-calculated degree of reflected light that would be expected from an imaginary light source and hence the grey-scale of the rendered image does not indicate X-ray attenuation. Although providing excellent anatomical detail, loss of information occurs, with intraluminal contrast material (90-250 HU) and mural calcification (200-700 HU) appearing indistinguishable. Thus, for example, rings of calcification may be interpreted as patent vessel sections even if the vessel is highly stenosed within the ring. Our use of multiple thresholds (range= l l 0 - 1 9 0 H U ) permitted this distinction and allowed more accurate assessment of vascular anatomy with the demonstration of third order aortic branches with remarkable clarity. Our initial experience with 3-D spiral CT angiography suggests that this fast, non-invasive technique can secure the diagnosis and provide sufficient anatomical information for surgical planning. This coupled with the ability of 2-D multiplanar views to show intra and extraluminal abnormalities, intimal calcifications, mural thrombus and if necessary the relationship of the aneurysm to the biliary tree adds a dimension not currently available with other imaging modalities. Fm'thermore, the data once acquired can be retrospectively edited and reconfigured into any possible projection, whereas conventional angiography requires additional intra-arterial contrast injections and further radiation exposure for each additional view. We conclude that 3-D spiral CT angiography is a promising technique for confirming the presence of hepatic artery aneurysms, depicting the artery of origin and detailing any variant anatomy.
Acknowledgements. We wish to acknowledge the assistance of Dr M. Raphael in the investigation of these cases and thank Mr R. Russell for his permission to report on the third case.
REFERENCES 1 Harlaftis NN, Akin JG. Hemobilia from ruptured hepatic artery aneurysm. American Journal of Surgery 1977;133:229-232. 2 Guida PM, Moore SW. Aneurysm of the hepatic artery: report of five cases with a brief review of the previously reported cases. Surgery 1966;60:299-310. 3 Countryman D, Norwood S, Register D et aL Hepatic artery aneurysm: report of an unusual case and review of the literature. American Surgeon 1983;49:51-54. 4 Rutherford RB. Vascular Surgery, 1st edn. Philadelphia: WB S aunders Co, 1977:676-678. 5 Haimovici H. Vascular Surgery- Principles and Techniques. New York: McGraw-Hill, 1976:383-384. 6 Warshauer DM, Keefe B, Manro MA. Intrahcpatic hepatic artery aneurysm: computed tomography and colour-flow Doppler ultrasound findings. Gastrointestinal Radiology 1991;16:175-177. 7 Curran F r , Taylor SA. Hepatic artery aneurysm. Postgraduate Medical Journal 1986;62:957-959. 8 Lewis DR, Kung H, Connon JJ. Biliary obstruction secondary to hepatic artery aneurysm; cholangiographic appearance and diagnostic considerations. Gastroenterology 1982;82:1446-1451. 9 Gordon-Taylor G. A rare cause of gastrointestinal bleeding. British Medical Journal 1943;1:504-505. 10 Kibbler CC, Cohen DL, Cruicshank JK et aL Use of CAT scanning in the diagnosis and management of hepatic artery aneurysm. Gut 1985;26:752-756. 11 Zachary K, Geier S, Pellecchia C et aL Jaundice secondary to hepatic artery aneurysm; radiological appearance and clinical features. American Journal of Gastroenterology 1986;81:295-298. 12 Rubin GD, Walker PJ, Dake MD et aL Three-dimensional spiral computed tomographic angiography: an alternative imaging modality for the abdominal aorta and its branches. Journal of Vascular Surgery 1993;18:656-665. 13 Gomes MN, Davros WJ, Zeman RK. Preoperative assessment of abdominal aortic aneurysm: the value of helical and three-dimensional computed tomography. Journal of Vascular Surgery 1994;20:367-375.
© 1997 The Royal College of Radiologists, ClinicalRadiology, 52, 227-230.
Hepatic Artery Aneurysms: Evaluation Using Three-dimensional Spiral CT Angiography S. J. H O W L I N G , H. GORDON*, T. M c A R T H U R , A. H A T F I E L D * and W. R. LEES
Departments of Radiology and *Gastroenterology, The Middlesex Hospital, UCL Hospitals Trust, Mortimer St, London, WIN 8AA Hepatic artery aneurysms are rare and frequently difficult to diagnose. Computed tomography (CT) and ultrasound rarely make the definitive diagnosis and angiography is usually required. We present three cases of hepatic artery aneurysms in which the definitive diagnosis was made on three-dimensional (3-D) spiral CT angiography-to our knowledge, this has not previously been described. Our experience shows that in many cases of hepatic artery aneurysm, conventional angiography need only be performed as a prelude to embolization. Howling, S. J., Gordon, H., McArthur, T., Hatfield, A. & Lees, W. R. (1997). Clinical Radiology 52, 2 2 7 - 2 3 0 . Hepatic Artery Aneurysms: Evaluation Using Threedimensional Spiral CT Angiography
Accepted for Publication 6 August 1996
Hepatic artery aneurysms are rare. Eighty per cent of patients present acutely with aneurysm rupture, with an attended high mortality [1]. Diagnosis is difficult and often delayed, owing to the non-specific symptoms and lack of clinical findings. Conventional cross-sectional imaging techniques (CT and ultrasound) often reveal the presence o f an aneurysm, but the artery o f origin is not always clear and angiography is still necessary. W e report three cases o f hepatic artery aneurysm in which the definitive diagnosis was established using 3-D spiral CT angiography. Although conventional angiography was subsequently performed, our experience suggests that in most cases of hepatic artery aneurysm conventional angiography need only be performed as a prelude to embolization. To our knowledge these are the first reported cases of hepatic artery aneurysm to be investigated with 3-D spiral CT angiography.
were established on the basis of a review of individual sections. The resultant m o d e l could be rotated 360 (and orientated in any manner allowing accurate determination of 3-D spatial relations. Quasi-surgical techniques allowed removal of unwanted structures and overlapping vessels. Simultaneous 2-D multiplanar reformatting was possible at any level, providing additional information on intimal calcifications and mural thrombus. The CT angiography models were interpreted by a consultant radiologist prior to and without the knowledge of conventional angiographic findings. Observers were asked specifically to comment on the exact location of the aneury s m and on variant anatomy. Subsequently, the two studies were correlated, with arterial angiography as the reference standard. The 3-D reconstruction and analysis required an average o f 30 min extra operator time.
CASE REPORTS
PATIENTS AND METHODS Three patients (details below) with suspected visceral artery aneurysms were examined by 3D-spiral CT angiography prior to conventional angiography. The spiral CT was performed on a GE Prospeed CT scanner. Pre-contrast, contiguous 10 m m axial slices were obtained to localize the volume o f interest. Serial imaging of a 10 ml contrast bolus injected at 5 ml/s, with CT images obtained at the cephalad extent of the volume of interest was used to generate a timedensity curve to plan optimal vascular opacification. A total of 120 ml of non-ionic contrast m e d i u m (350 mg I/ml) was then infused intravenously at 5 ml/s and 5 m m axial contiguous slices obtained and reconstructed at an interval o f 2.5 mm. 3-D reconstruction of the data obtained was performed on a U C L Medical Graphics Workstation (UCL Medical Imaging, London, UK) to generate a multi-threshold shadedsurface display image. Shaded-surface display thresholds Correspondence to: Dr S J Howling, Department of Radiology, The Middlesex Hospital, Mortimer St, London, WIN 8AA, UK. © 1997The RoyalCollegeof Radiologists.
Case 1. A 67-year-old man was referred from a local hospital for CT guided biopsy of an 8 cm, enhancing, calcified, pancreatic mass that had been detected on conventional contrast enhanced CT scans. He gave a 3year history of increasing, non-specific, intermittent epigastric pain radiating to the back, but was otherwise well and physical examination was unremarkable. Ultrasound examination demonstrated an 8 x5 cm cystic mass adjacent to the head of the pancreas, which itself appeared normal. Doppler interrogation demonstrated a typical arterial waveform within the cyst; and a visceral artery aneurysm was suspected. A 3-D spiral CT angiogram was performed. The spiral CT scans confirmed the presence of an 8 cm diameter, heavily calcified aneurysm within the porta hepatis. The exact artery of origin was unclear on sectional images. The 3-D reconstruction showed a large solitary aneurysm clearly arising from the proximal common hepatic artery (Fig. 1), with a stenosis at the origin of the aneurysm. The hepatic artery emerging from its distal end divided almost immediately into the right and left hepatic arteries. An accessory right hepatic artery originated from the coeliac axis to pass inferior to the aneurysm. The gastroduodenal artery originated from the left hepatic artery and passed anterior to the aneurysm. The superior mesenteric artery was normal. Selective angiograms of the coeliac axis and superior mesenteric arteries confirmed the 3-D spiral CT findings (Fig. 2). No additional arterial abnormalities were seen.The aneurysm was felt suitable for transcatheter embolization, which was performed using tungsten coils and Gelfoam.
228
CLINICAL RADIOLOGY
Fig. 1 - 3-D spiral CT angiogram (shaded-surface model) demonstrating a large solitary anenrysm (AN) arising from the proximal common hepatic artery (CH). The hepatic artery emerging from its distal end divides almost immediately into right (RH) and left (LH) hepatic arteries. The gastroduodenal artery (G) originates from the left hepatic artery and passes anteriorly to the aneurysm. The origin of an accessory right hepatic artery (AR) is demonstrated at the coeliac axis. The continuation of this vessel, which passes inferiorly to the aneurysm has been edited out. Portal vein (P) compressed by the aneurysm sac (confirmed on 2-D multiplanar views). Splenic artery (S).
Fig. 3 - 3-D spiral CT angiogram (shaded-surface model) demonstrating a single aneurysm (AN) of the common hepatic artery (CH) arising just proximal to the origin of the gastroduodenal artery (G). Superior mesenteric artery (SMA), fight (RH) and left (LH) main hepatic arteries.
Fig. 2 - Conventional selective coeliac axis angiogram confirming the origin of the aneurysm as the common hepatic artery.
Post embolization arterial angiography showed successful obliteration of the aneurysm and a repeat ultrasound examination after 3 months confirmed thrombosis of the aneurysm with no residual Doppler flow, at which time the patient was completely well with no abdominal pain. Case 2. A 19-year-old woman with polyarteritis nodosa presented with a one month history of increasing lethargy and intermittent abdominal pain. Examination was nnremarkable. Pertinent laboratory findings included an ESR of 96mm/h (<17mm/h) and a C-reactive protein of 109mg/1 (< 12 mg/l). An abdominal ultrasound was normal. An enhanced spiral CT was subsequently performed and demonstrated a 1 cm × 1 cm aneurysm, apparently arising from the common hepatic artery. 3-D spiral CT angiography confirmed the single, non-calcified aneurysm to arise from the common hepatic artery, proximal to the origin of the gastroduodenal artery (Fig. 3). No mural thrombus was detected on the 2-D multiplanar views. No variants of vascular anatomy were demonstated. Conventional angiography confirmed these findings (Fig. 4). In view of the active disease indicators the patient was given intravenous methylprednisolone and cyclophosphamide and the abdominal pain settled. The patient remains under regular review with no active treatment for the hepatic artery aneurysm. Case 3. A 58-year-old woman was referred from her local hospital, where she had presented with a 2-week history of nausea and progressive jaundice. Biochemistry revealed a serum bilirubin of 171/zmol/1 with a
Fig. 4 - Conventional selective coeliac axis angiogram providing confirmation of the aneurysm arising from the common hepatic artery.
cholestatic pattern. Ultrasound examination demonstrated a 3-cm diameter cystic lesion in the uncinate process of the pancreas, but normal liver and biliary tree. A spiral CT scan was performed a week later, by which time her symptoms had resolved and biochemistry had returned to normal. The CT study, however, revealed a 3 cm heavily calcified aneurysm inferior to the head of the pancreas, which itseff appeared normal. The aneurysm seemed to originate from a branch of the superior mesenteric artery (SMA). A second, smaller aneurysm arose from the fight hepatic artery. 3-D spiral CT angiography demonstrated a variant of normal visceral arterial anatomy with an accessory right hepatic artery arising from the SMA. A 3-cm aneurysm originated from the accessory right hepatic artery © 1997 The Royal College of Radiologists, Clinical Radiology, 52, 227-230.
HEPATIC ARTERY ANEURYSMS
Fig. 5 - 3-D spiral CT angiogram (shaded-surface model) demonstrating a normal anatomical variant with an accessory right hepatic artery (AR) arising from the superior mesenteric artery (SMA). A large aneurysm (AN) arises from the proximal accessory right hepatic artery with a further smaller aneurysm arising more distally (AN). Rotation of the model demonstrates this relationship more clearly and reveals absence of the coeliac trunk. Splenic artery (S). Common hepatic artery (CH) which is projected over the aneurysmal accessory right hepatic artery in this view.
with a further 1 cm aneurysm arising from the same vessel more distally (Fig. 5). Rotation of the model revealed absence of the coeliac trunk. Conventional angiography with selective cannnlation of the SMA confirmed the position of the aneurysms and the accuracy of the 3-D model (Fig. 6) with filling of the coeliac axis territory via enlarged vessels around the pancreatic head. A lateral aortogram confirmed true absence of the coeliac trunk. At operation the accessory right hepatic artery was ligated following excision of the aneurysms. The patient remains well 1 month post-operatively.
DISCUSSION Hepatic artery aneurysms are rare, but frequently fatal [2]. They constitute 20% of visceral artery aneurysms with only those of the splenic artery being more common [2]. Eighty per cent of hepatic artery aneurysms are extrahepatic and of these, 63% affect the common hepatic artery, 28% the right hepatic artery, 5% the left hepatic artery and 4% both the right and left hepatic arteries [2-5]. Lesions may be single or multiple and have been reported in patients from 10 to 93 years of age with a mean age of approximately 40 years [2,3,6]. The aetiology of hepatic artery aneurysms, thought to be exclusively mycotic prior to the advent of antibiotics is now more commonly atherosclerosis (an associated factor in 32%) or medial degeneration (found in a further 24%). Less common causes include polyarteritis nodosa, tuberculosis, © 1997 The Royal College of Radiologists, Clinical Radiology, 52, 227-230.
229
Fig. 6 - Conventional selective superior mesenteric artery angiogram confirms the 3-D spiral CT findings.
inflammation of the biliary tree and trauma, including iatrogenic trauma from biliary surgery and radiological interventional procedures [2,7] Clinical presentation tends to be variable and non-specific with fewer than one-third of patients presenting with the classical triad of abdominal pain, haemobilia and obstructive jaundice [1]. Eighty per cent of hepatic artery aneurysms are not detected until they rupture, either into the peritoneal cavity (43%), biliary tree (41%), gastro-intestinal tract (11%) or portal vein (5%), with resultant haemoperitoneum, haemobilia or haematemesis [1,8,9]. Rupture carries a high associated mortality. Short of this catastrophic presentation, 70% of patients complain of epigastric or right upper quadrant pain, which occasionally radiates to the back or right shoulder [1,2]. Jaundice due to an intraductal clot or biliary tree compression is seen in 50% of cases [8]. Physical signs are rare, but may include a palpable mass, bruit or hepatomegaly [1,2,10]. Radiological diagnosis of hepatic artery aneurysm is also difficult. Conventional imaging has little to offer. Ultrasound and CT are frequently misleading because of a tow index of suspicion, as highlighted by cases 1 and 3. Even when intravenous contrast enhancement or colour flow Doppler reveal the vascular nature of the mass, the exact site of origin is rarely demonstrated [7,11 ]. Angiography has therefore remained essential to confirm the diagnosis, delineate feeding vessels and provide the anatomical information required for surgery. The technique of 3-D spiral CT angiography has already been successfully employed in the assessment of renal and mesenteric artery stenoses, abdominal aortic dissections and abdominal aortic aneurysms [12,13]. These studies used
230
CLINICAL RADIOLOGY
single threshold, shaded-surface display models. These display pixels with a CT number above a selected threshold. All pixels below the threshold are set to zero and are not displayed in the 3-D image. Grey-scale encodes a surface rendering, based on a computer-calculated degree of reflected light that would be expected from an imaginary light source and hence the grey-scale of the rendered image does not indicate X-ray attenuation. Although providing excellent anatomical detail, loss of information occurs, with intraluminal contrast material (90-250 HU) and mural calcification (200-700 HU) appearing indistinguishable. Thus, for example, rings of calcification may be interpreted as patent vessel sections even if the vessel is highly stenosed within the ring. Our use of multiple thresholds (range= l l 0 - 1 9 0 H U ) permitted this distinction and allowed more accurate assessment of vascular anatomy with the demonstration of third order aortic branches with remarkable clarity. Our initial experience with 3-D spiral CT angiography suggests that this fast, non-invasive technique can secure the diagnosis and provide sufficient anatomical information for surgical planning. This coupled with the ability of 2-D multiplanar views to show intra and extraluminal abnormalities, intimal calcifications, mural thrombus and if necessary the relationship of the aneurysm to the biliary tree adds a dimension not currently available with other imaging modalities. Fm'thermore, the data once acquired can be retrospectively edited and reconfigured into any possible projection, whereas conventional angiography requires additional intra-arterial contrast injections and further radiation exposure for each additional view. We conclude that 3-D spiral CT angiography is a promising technique for confirming the presence of hepatic artery aneurysms, depicting the artery of origin and detailing any variant anatomy.
Acknowledgements. We wish to acknowledge the assistance of Dr M. Raphael in the investigation of these cases and thank Mr R. Russell for his permission to report on the third case.
REFERENCES 1 Harlaftis NN, Akin JG. Hemobilia from ruptured hepatic artery aneurysm. American Journal of Surgery 1977;133:229-232. 2 Guida PM, Moore SW. Aneurysm of the hepatic artery: report of five cases with a brief review of the previously reported cases. Surgery 1966;60:299-310. 3 Countryman D, Norwood S, Register D et aL Hepatic artery aneurysm: report of an unusual case and review of the literature. American Surgeon 1983;49:51-54. 4 Rutherford RB. Vascular Surgery, 1st edn. Philadelphia: WB S aunders Co, 1977:676-678. 5 Haimovici H. Vascular Surgery- Principles and Techniques. New York: McGraw-Hill, 1976:383-384. 6 Warshauer DM, Keefe B, Manro MA. Intrahcpatic hepatic artery aneurysm: computed tomography and colour-flow Doppler ultrasound findings. Gastrointestinal Radiology 1991;16:175-177. 7 Curran F r , Taylor SA. Hepatic artery aneurysm. Postgraduate Medical Journal 1986;62:957-959. 8 Lewis DR, Kung H, Connon JJ. Biliary obstruction secondary to hepatic artery aneurysm; cholangiographic appearance and diagnostic considerations. Gastroenterology 1982;82:1446-1451. 9 Gordon-Taylor G. A rare cause of gastrointestinal bleeding. British Medical Journal 1943;1:504-505. 10 Kibbler CC, Cohen DL, Cruicshank JK et aL Use of CAT scanning in the diagnosis and management of hepatic artery aneurysm. Gut 1985;26:752-756. 11 Zachary K, Geier S, Pellecchia C et aL Jaundice secondary to hepatic artery aneurysm; radiological appearance and clinical features. American Journal of Gastroenterology 1986;81:295-298. 12 Rubin GD, Walker PJ, Dake MD et aL Three-dimensional spiral computed tomographic angiography: an alternative imaging modality for the abdominal aorta and its branches. Journal of Vascular Surgery 1993;18:656-665. 13 Gomes MN, Davros WJ, Zeman RK. Preoperative assessment of abdominal aortic aneurysm: the value of helical and three-dimensional computed tomography. Journal of Vascular Surgery 1994;20:367-375.
© 1997 The Royal College of Radiologists, ClinicalRadiology, 52, 227-230.