Aortocaval Fistula Complicating Abdominal Aortic Aneurysm: A Case Report

Aortocaval fistula is a rare complication arising from an abdominal aortic aneurysm. A typical feature observed during the arterial phase of contrast-enhanced CT scanning in such patients is simultaneous enhancement of the dilated inferior vena cava and aorta. Awareness of the specific radiologic features of aortocaval fistula may facilitate diagnosis when the condition is unsuspected clinically. We report a case of aortocaval fistula secondary to abdominal aortic aneurysm, and review the previous literature.

Congenital Anomalies of Aortic Arch: CT Angiography

Aortic arch anomalies result from the failure of an embryonic vascular structure to persist and regress in the usual manner during formation of the aortic arch. The anomalous aortic arch may encircle and compress the trachea and esophagus as a form of a vascular ring. The diagnosis of aortic arch anomaly and the recognition of airway compression are important because they are conditions which complicate the natural and surgical course of related diseases. CT can demonstrate the nature of anatomic structures such as the trachea and esophagus not revealed by angiography, simultaneously disclosing the relationship of stenotic airways and offending mediastinal vessels. Volumetric data acquisition by means of spiral CT enables three dimensional reconstruction,which can provide easy global understanding of the complex anatomy and spatial relationship of airway and cardiovascular structures. Three dimensional imaging is very useful for the physician and surgeon who are not accustomed to mentally reconstructing axial images, and can facilitate surgical planning.

CT Findings of Aortic Intramural Hematoma with or without associated Penetrating Aortic Ulcer

PURPOSE: To analyze the CT findings of aortic intramural hematoma (IMH) with or without associated penetrating aortic ulcer (PAUH), as seen on initial and follow-up CT scans. MATERIALS AND METHODS: We retrospectively analyzed the CT findings of 36 cases diagnosed clinically and radiologically as IMH (n=7) and PAUH (n=29) after initial and follow-up CT scanning. The period between initial and follow-up scanning-which was performed between two and four times-ranged from 1 week to 91 months (mean: IMH, 18.4 months;PAUH, 16.2 months). RESULTS: With regard to maximal thickness and extension of IMH, maximal diameter of the involved aorta, inward displacement of intimal calcification, Stanford type of IMH, and pleural and pericardial effusion between IMH & PAUH, the results were not statistically significant, but PAUH tends to develop in older patients and shows a more frequent incidence of aortic atherosclerosis. Only PAUH involved abdominal aortic a-neurysm and focal right renal infarction, each in one case. Penetrating aortic ulcers (PAU) were more frequently found in the proximal descending thoracic aorta (n=24) than in the mid(n=11) to distal(n=10) descending thoracic aorta. Among 53 cases of PAU, seven could not be detected on initial CT scans; this was due to excessive scan thickness (n=4) and masking of the aortic ulcer by IMH(n=3), circumstances which were visualized after resolution of IMH. Follow-up CT scanning showed that PAU progressed to fusiform or saccular aortic dilatation (n=15) or localized aortic dissection (n=4), and that in 34 cases, there was no interval change. Follow-up CT findings of IMH in cases of PAUH were as follows: Type A (n=8), with four resolutions after surgery and four after conservative treatment; Type B (n=21), with 21 resolutions after conservative treatment. Follow-up CT findings of IMH were as follows: Type A (n=2), with one resolution after surgery and one after conservative treatment; Type B (n=5), with progression of typical aortic dissection in two cases, and three resolutions after conservative treatment. CONCLUSION: PAUH is characterized by its occurrence in older patients, a more frequent incidence of aortic atherosclerosis and abdominal aortic aneurysm, but no difference in the extension of IMH and other CT findings between PAUH and IMH. Branch vessel involvement was noted in one case of PAUH but not in cases of IMH. Follow-up CT scanning showed that in the absence of surgery, IMH progressed to aortic dissection or resolution. In all patients who did not undergo surgery, PAU progressed to saccular or fusiform aortic dilatation, localized aortic dissection and no interval change, with resolution of IMH after conservative treatment. Initial and follow-up thin-slice spiral CT scanning can provide correct diagnosis and treatment planning (especially ascending aorta is involved), and permit differentiation between PAUH and IMH.

A Suggestion of New Integrated Prognostic Factor for Aortic Aneurysm: Ta n gential Stress Index

PURPOSE: To construct a useful index for use as a prognostic factor in cases of aortic aneurysm. MATERIALS AND METHODS: Using CT or EBT, we studied nine ruptured aortic aneurysms, 40 unruptured aneurysms, and 42 normalaortas, measuring aortic diameter and wall thickness. Systolic, mean or diastolic blood pressure was used as apressure parameter. Tangential stress(TS) and the tangential stress index ( TSI) were calculated by modified Laplace's law. RESULTS: Average diastolic TS's (TSI's) were 1938 (4.13), 905 (1.84) and 554 (0.94) in rupturedaneurysm, unruptured aneurysm and normal groups, respectively (p<0.01). ROC curves of diastolic TS and TSI wereseen in a "useful study" zone. With a threshold of 1230 (2.90) for TS (TSI), the sensitivity and thespecificity for differentiation of ruptured and unruptured aneurysms were 100% (100%) and 75% (88%), and thepositive and the negative predictive values were 47% (64%) and 100% (100%), respectively (p<0.01). Amongsystolic, mean and diastolic TS 's and TS I 's, the diastolic TSI showed the highest specificity at its maximalsensitivity. CONCLUSION: Diastolic TSI is a more accurate prognostic factor for aortic aneurysm.

Aortic Arch Aneurysm: CT and MR Features

PURPOSE: The purpose of this study was to evaluate the CT and MR features of aortic arch aneurysms and todetermine the differences between involved segments and morphologic types according to their causes. MATERIALS AND METHODS: Twenty-nine patients with aortic arch aneurysms who underwent CT scanning(n=24) and/or MR imaging(n=16)were retrospectively evaluated. The aneurysms were analyzed with respect to location of involved segment,morphology, direction and size, and morphologic differences between aneurysms were compared according to causes. RESULTS: The causes of arch aneurysms were atherosclerosis in 25 patients(86%), trauma in three (10%) and infection in one (4%). Arch aneurysms were frequently located at the arch only(n=17,59%), ascending aorta toarch(n=6,21%), arch to descending aorta(n=4,14%), or ascending aorta to descending aorta(n=2,7%). The shape of theaneurysm was fusiform in 15 patients and saccular in 14. Atherosclerotic aneurysms(n=25) were fusiform in 15patients and saccular in ten. Arch aneurysms due to trauma and infection(n=4) were saccular. MRI was more helpfulthan CT scanning involved site, direction, and morphology of the aneurysm. CONCLUSION: Bothe CT scanning and MRIeasily diagnose arch aneurysms, though MRI is a very useful imaging modality for evaluating involved aorticsegments and morphologic types. Aortic arch aneurysms are either fusiform or saccular. Most saccular aneurysmsinvolve the aortic arch, whereas the involvement of fusiform aneurysms is more varied. Atherosclerosis is the mostcommon cause of both fusiform and saccular arch aneurysms.

Intrathoracic Major Vessels, Trachea and Main Bronchi: The Effect of Respiration on Size

PURPOSE: To evaluate the effect of respiration on the sizes of intrathoracic vasculature, and the trachea,and the main bronchus. MATERIALS AND METHODS: Seventeen volunteers (10males aged 20-39 years and 7 females aged20-39 years) underwent spiral CT, between the apex and lowest base of the lung, collimation was 10mm, pitch was 1,and images were obtained at breath hold forced end-inspiration and breath hold forced end-expiration. Crosssecional areas or diameters were measured in each respiration state at the aorta (ascending, descending, lowerthoracic) and great branches, the IVC (thoracic, abdominal), the SVC, pulmonary artery (right main, leftdescending) and the tracheobronchus (trachea, left upper bronchus). Changes in the size of vessels and airwaysbetween the respiration states were evaluated and compared between inspiration and expiration. RESULT: Duringbreath-hold forced end-inspiration CT, the ascending, descending, and lower thoracic aorta and itsbranches(brachiocephalic, left common carotid, left subclavian) as well as the thoracic IVC and SVC and the rightmain and left descending pulmonary arteries decreased in size: during breath-hold forced end-expiration CT, thesize of all these vessels increased. For the trachea, left upper lobe bronchus and abdominal IVC, the situationwas reversed. Statistically significant changes(p<0.05) were noted in the ascending aorta and descending aorta,the lower thoracic aorta, the thoracic and abdominal IVC, the SVC, the right main and left pulmonary arteries, andthe trachea. CONCLUSION: During respiration, changes in the size of the thoracic vasculature and airways isprobably due to changes in intrathoracic pressure. In the measurement and diagnosis of stenosis or dilatation inthe intrathoracic vesculature and airways, respiration states should therefore be considered.

Acute Aortic Intramural Hematoma

PURPOSE: To evaluate the radiologic findings of acute intramural hematoma of the aorta, and the clinical follow up thereof. MATERIALS AND METHODS: Among 34 cases confirmed clinically and radiologically as aortic dissection, an analysis was carried out based on 15 cases in which intramural hematoma without false lumen was demonstrated, on initial CT, 12 cases of in which follow up CT was used and five cases involving an aortogram. Elements such as the shape of the thickened aortic wall, ulcer-like intimal defects, and intimal calcification were examined. Changes in these elements were also examined on follow up CT. RESULTS: DeBackey types I and III accounted for one and 14 cases. respectively. Initial precontrast CT demonstrated continuous, crescentic high attenuation areas along the wall of the descending aorta. In postcontrast scans, the crescentic areas were of relatively lower-attenuation and appeared along the aorta wall. Displaced intimal calcifications were seen in nine of fifteen patients. There was no intimal flap on all five aortogram, while aortic wall thickening and atherosclerotic change were demonstrated in four cases and in one case, case, respectively. Focal ulcers were seen in three cases. Ulcer-like intimal defects were demonstrated in a total of eleven cases (eight on CT, two on aortogram, and one on both). In ten of the twelve cases seen on follow up CT, the thickness of the intramural hematoma was seen to be reduced. Among the 15 cases, the operation was performed in two cases, and the remaining 13 received conservative treatment. In ten cases observed for more than twelve months, a recurrence of symptoms did not occur. CONCLUSION: Eccentric aortic wall thickening in patients who complain of acute chest pain is the result of acute aortic dissection with intramural hematoma, or a penetrating atherosclerotic ulcer of the aorta.The latter may be differentiated from the former by the presence of on ulcer-like intimal defect. When both diseases are limited to the descending aorta, conservative treatment may be effective, unless patients experience persistent or recurrent chest pain, or unless intramural hematoma progresses further.

Various Complications of Abdominal Aortic Aneurysm: CT Findings

PURPOSE: To evaluate on abdominal CT the type and incidence of various complications of abdominal aortic aneurysm (AAA). MATERIALS AND METHODS: Twenty six suspected cases of AAA were confirmed by operation(n=21) and by CT(n=5). The etiology, size, shape and incidence of various complications of AAA were then retrospectively evaluated. In addition, post-operative complications were also evaluated in five cases. RESULTS: The etiology ofthe aneurysm was atherosclerotic in 18 cases and mycotic in three ; it showed the presence of Behcet disease in three cases, of tuberculosis in one, and of Marfan syndrome in one. Among the 18 fusiform AAA, the mean maximum diameter of ruptured AAA(7.5+/-3.3cm, n=3) was significantly larger than that of unruptured AAA(4.9+/-1.6cm, n=15)(p<0.05). The saccular type was much more likely to rupture than the fusiform type(p<0.00001). Out of the eight saccular AAA, seven ruptured ; their mean maximum diameter was 3.9+/-1.3cm This was significantly smaller than that of ruptured fusiform aneurysm(p<0.05). The most common complication was rupture, and occurred ten of 26 cases(38%). Others included hydronephrosis in three cases, bowel infarction in one, and perianeurysmal retroperitoneal fibrosis in one case. Various post-operative complications developed in five patients ; these comprised periprosthetic pseudoaneurysm with hematoma (two cases), bowel ischemia (one), focal renal infarction(one), and secondary aorticoduodenal fistula (one). CONCLUSION: The most common complication of AAA was rupture, the rate of which was much higher in the saccular type with smaller size than the fusiform type. Other various and uncommon complications were observed. CT was helpful in detecting complications arising from AAA and in planning its treatment.

Various Complications of Abdominal Aortic Aneurysm: CT Findings

PURPOSE: To evaluate on abdominal CT the type and incidence of various complications of abdominal aortic aneurysm (AAA). MATERIALS AND METHODS: Twenty six suspected cases of AAA were confirmed by operation(n=21) and by CT(n=5). The etiology, size, shape and incidence of various complications of AAA were then retrospectively evaluated. In addition, post-operative complications were also evaluated in five cases. RESULTS: The etiology ofthe aneurysm was atherosclerotic in 18 cases and mycotic in three ; it showed the presence of Behcet disease in three cases, of tuberculosis in one, and of Marfan syndrome in one. Among the 18 fusiform AAA, the mean maximum diameter of ruptured AAA(7.5+/-3.3cm, n=3) was significantly larger than that of unruptured AAA(4.9+/-1.6cm, n=15)(p<0.05). The saccular type was much more likely to rupture than the fusiform type(p<0.00001). Out of the eight saccular AAA, seven ruptured ; their mean maximum diameter was 3.9+/-1.3cm This was significantly smaller than that of ruptured fusiform aneurysm(p<0.05). The most common complication was rupture, and occurred ten of 26 cases(38%). Others included hydronephrosis in three cases, bowel infarction in one, and perianeurysmal retroperitoneal fibrosis in one case. Various post-operative complications developed in five patients ; these comprised periprosthetic pseudoaneurysm with hematoma (two cases), bowel ischemia (one), focal renal infarction(one), and secondary aorticoduodenal fistula (one). CONCLUSION: The most common complication of AAA was rupture, the rate of which was much higher in the saccular type with smaller size than the fusiform type. Other various and uncommon complications were observed. CT was helpful in detecting complications arising from AAA and in planning its treatment.

Motion Artifact Simulating Dissection of Ascending Aorta on CT

PURPOSE: The purpose of this study was to investigate the frequency, site and characteristics of motion artifact of ascending aorta mimicking dissection. MATERIALS AND METHODS: The authors evaluated postcontrast CT scans of 60 cases in 60 patients without symptoms of aortic dissection or aortic disease. A Toshiba 900S scanner was used, with 1 cm slice thickness and 1 sec scan time. Streak artifacts, and those relating to extra-aortic vascular structure or pericardial effusion were excluded from this study. RESULTS: Crescent-shaped motion artifacts were seen in 54 cases (90%), and occurred from 1 cm to 4 cm above the level of the aortic valve; between men and women, there was no significant difference in frequency. In each case, the artifact was seen at 1 to 5 (mean 2.9) levels. Its pattern was symmetric in 31 of 60 cases (51%), and at 15 other sites, symmetric artifacts were seen between the SVC and ascending aorta. At the margin of the aortic circumference, the direction of the artifact was left anterior-right posterior in 23.9% of cases, and anterior median-posterior median in 20.8%. CONCLUSION: On CT, motion artifact of ascending aorta occurs frequently. Findings relating to location, symmetric pattern and characteristic direction of artifact may be helpful in the differential diagnosis of aortic dissection and aortic motion artifact.

Aortic Intramural Hematoma: Assessment of Clinical and Radiological Features in Comparison to Acute Aortic Dissection

PURPOSE: To compare the clinical and radiological features of aortic intramural hematoma(IMH) to those of acute aortic dissection(AD). MATERIALS AND METHODS: We analyzed the clinical and radiological features of 12patients with aortic IMH and 43 patients with acute AD. In aortic IMH, the diagnoses were made by means of both CTand transesophageal echocardiography (TEE) and included two surgically proven cases. In acute AD, the diagnoses were made by means of CT and TEE and included 21 surgically proven cases. We com- pared patients ages, etiologies, the extent of the disease, the presence or absence of aortic branch involvement, complications, and outcomes. RESULTS: Aortic IMH tended to develop in older patients (67.8+/-7.9 vs. 50.4+/- 13.4, P.05). In aortic IMH, there was no involvement of aortic branches, whereas in acute AD, 14 (33%) patients showed involvement of one or more aortic branches. Complications of aortic IMH included pericardial effusion (n=2) and pleural effusion (n=4) ; in acute AD, pericardial effusion (n=7), pleural effusion(n=4), aortic insufficiency (n=8), cerebral infarction (n=3), renal infarction (n=4) and spinal infarction (n=1)were seen. There was one (8%) death due to aortic IMH and ten (23%) deaths due to acute AD (p<.01). CONCLUSION: Aortic IMH is characterized by its occurrence in older patients with hypertension, a less frequent incidence of complications, and a more favorable outcome than acute AD.