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Clinical Observations |
1 Department of Radiology, Asan Medical Center, University of Ulsan College of
Medicine, 388-1 Pungnap-dong, Songpa-gu, Seoul, South Korea 138-736.
2 Department of Surgery, Asan Medical Center, University of Ulsan College of
Medicine, Seoul, South Korea.
Received May 9, 2005;
accepted after revision August 9, 2005.
Address correspondence to A. Y. Kim
(aykim{at}amc.seoul.kr).
Abstract
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CONCLUSION. Inferior phrenic arterial bleeding occurs frequently and is one of the major postoperative bleeding sites in patients undergoing liver transplantation. Awareness of its common clinical manifestations and predictive CT features is essential for prompt diagnosis and treatment of this early vascular complication, and this knowledge can help to avoid unnecessary reoperation and catastrophic hypotension.
Keywords: abdominal imaging • arteriography • CT • liver transplantation
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Radiologic manifestations and clinical significance of main vascular complications such as hepatic arterial or venous thrombosis are well known in patients undergoing liver transplantation, but there are little data regarding postoperative bleeding in these patients. Unfortunately, we experienced some cases with a sudden decrease of hematocrit and hypotensive crisis in posttransplantation patients, in whom the bleeding originated in an inferior phrenic artery (IPA). If detection of postoperative arterial bleeding is delayed and it is not treated by open surgical vascular revision, it can be fatal [3]. With the increasing number of liver transplantations, the frequency of these complications is likely to increase. For good outcome in these patients, therefore, accurate knowledge and early recognition of these complications are essential. To our knowledge, however, no attention has previously been paid to postoperative IPA bleeding. This study was performed to determine the incidence of IPA bleeding after liver transplantation in adult patients and to describe clinical manifestations and predictive CT features.
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Two-Phase MDCT
CT examinations were performed with an MDCT scanner (LightSpeed QX/i, GE
Healthcare; Somatom Sensation 16, Siemens Medical Solutions). Each patient
received 150 mL of iopromide (Ultravist 370, Schering), which was injected
using a power injector at a flow rate of 3 mL/s through an 18-gauge
angiographic catheter inserted into a forearm vein. A baseline unenhanced scan
was obtained by using 5-mm collimation and a pitch of 0.75 (LightSpeed QX/i)
or a pitch of 1 (Somatom Sensation 16) from the dome of the diaphragm to the
lower pole of the right kidney. Arterial phase imaging was initiated within 5
seconds after enhancement of the descending aorta to 100 H, as measured by a
bolus-tracking technique (Smart Prep, GE Healthcare). CT parameters for
arterial phase scanning included (for LightSpeed QX/i) a pitch of 1.5,
collimation of 1.25 mm, and table speed of 15 mm; and (for Somatom Sensation
16) a pitch of 1, collimation of 0.75 mm, and table speed of 12 mm; both using
120 kVp and 250 mA. Portal venous phase imaging was initiated 72 seconds after
contrast injection and covered from the dome of the diaphragm to the symphysis
pubis.
Image Analysis
CT scans were retrospectively reviewed by two experienced abdominal
radiologists. All CT images were evaluated on a PACS monitor to determine the
presence of abnormal fluid collection. CT attenuation of the abnormal fluid
collection was recorded on noncontrast CT images with the same elliptic region
of interest (ROI). Their distributions were recorded, focusing on the hepatic
graft.
The size of the IPA and the presence and location of direct extravasation of contrast material were also evaluated. To measure the size of the right and left IPAs, the images were magnified on the PACS monitor and the anteroposterior diameter of the artery was measured just above the level of the right or left adrenal gland. To analyze size differences between both IPAs, Wilcoxon's signed rank test was used with SPSS software (version 10.0.7, SPSS), and p < 0.05 was considered to show a significant difference.
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Clinical Manifestations
Common clinical manifestations included sudden drainage of fresh blood from
the drainage tube (n = 28), an acute decrease of hemoglobin level of
more than 2 mg/dL (n = 17; mean = 2.57 ± 1.84 mg/dL), and
systemic hypotension (n = 14; mean = 83.57 ± 9.05 mm Hg). Of
these, hypotensive crisis requiring blood transfusion of more than four pints
per day was noted in nine patients. No patients showed altered liver function
tests before or after the onset of bleeding. The onset of these clinical
manifestations ranged from 1 to 14 days after liver transplantation (mean = 5
days).
All patients underwent two-phase CT and diagnostic angiography 1 or 2 days after the onset of clinical symptoms. At that time, tentative diagnostic interpretations of the CT scans included acute perihepatic hematoma of unknown origin (n = 14), postoperative perihepatic fluid collection of unknown origin (n = 6), and bleeding from the IPA (n = 8). Bleeding was treated with transcatheter arterial embolization in 23 patients; however, five patients finally underwent surgical revision.
CT Findings
All 28 patients showed abnormal fluid collection in the abdomen (right
upper quadrant, n = 26; multiquadrant, n = 2). Two patients
with a multiquadrant fluid collection received left-lobe or dual-lobe grafts.
In these patients, fluid collection was unevenly distributed in both upper
quadrants of the abdomen, although more was found in the right upper quadrant.
The most common location of abnormal fluid collection in the right upper
quadrant was the posterolateral site of the hepatic graft (n = 11),
followed by posteromedial (n = 7), posteroinferior (n = 5),
broad posterior (n = 3), and anterolateral (n = 2) sites.
Mean CT attenuation of the abnormal fluid collections was 39.5 H, with a range
from 3.7 to 78 H. Most patients showed high attenuation (> 25 H) of fluid
collection surrounding the hepatic graft, suggesting an acute hematoma (26/28,
93%) [4] (Figs.
1A,
1B, and
1C).
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Our study showed that bleeding from the right IPA occurred with an incidence of 5% within the first 2 weeks after liver transplantation. Lee et al. reported postoperative bleeding in 10 of 198 patients (5.1%) with living donor liver transplantation (presented at the 2002 annual meeting of the Radiological Society of North America). In their study, nonhepatic arterial bleeding was detected more frequently than hepatic arterial bleeding (3.8% and 1.4%, respectively), the majority occurring in the right IPA. Therefore, the right IPA is one of the chief postoperative bleeding sources in liver transplant recipients.
IPAs are paired small vessels near and below the diaphragmatic aortic hiatus that supply a large part of the diaphragm. Among them, the right IPA is clinically important because it acts as an extrahepatic collateral vessel [10, 11] and runs in front of the right crus of the diaphragm and then behind the inferior vena cava [8, 9]. During liver transplantation, ligation of the right IPA is necessary for hepatectomy in the recipient and for right hepatic lobectomy in a living donor. If the ligation of this artery is not maintained adequately, bleeding from the IPA can occur after liver transplantation.
In our study, most patients with IPA bleeding suffered from viral liver cirrhosis or hepatocellular carcinoma before liver transplantation (25/28, 89%) and underwent living donor liver transplantation (27/28, 96%). We think that the bleeding tendency of the right IPA after liver transplantation is relevant to its enlarged size, which suggests a high potential of extrahepatic collateral. This artery can supply hepatic tumors or surrounding hepatic tissue [10, 11], and it is frequently enlarged in patients with liver cirrhosis, which is revealed by axial thin-section CT [12]. Although it is unclear why the mean diameter of this artery is larger in cirrhotic patients than in a healthy control group, reduced portal blood flow into the liver is thought to be a possible cause. Therefore, under these clinical situations, the right IPA is likely to be hypertrophied and to have a tendency to bleed postoperatively.
Undoubtedly, liver transplantation is a causative factor for IPA bleeding. In a liver transplant recipient, hepatectomy can cause injury to the diaphragm or perihepatic tissues during retraction of the diaphragm or dissection of the right hepatic lobe from the surrounding tissue. The risk of injury to the diaphragm or perihepatic tissue seems to increase with living donor transplantation. Because a smaller hepatic graft can be unstable in the large right upper quadrant of the abdomen, it requires stronger fixation with the adjacent diaphragm or perihepatic tissue to prevent twisting of the graft on the vascular pedicle. Our study and that by Lee at al. [13] supported this presumption.
It is also important to notice that all IPA bleeding occurred within the first 2 weeks after liver transplantation and that its main clinical manifestations included sudden decreased hemoglobin level by more than 2 mg/dL and drainage of fresh blood from the drainage tube. Most patients (82%) were well controlled by transcatheter arterial embolization. These observations suggest that most arterial bleeding might be easily controlled by radiologic intervention if diagnosed rapidly.
In this study, the most common CT finding of right IPA bleeding was localized high attenuation of fluid collection of > 25 H in the posterior portion of the right hepatic graft. Pathognomonic findings were direct extravasation of contrast material from the right IPA, although its depiction on CT was not high (37%). However, active extravasation of contrast material in the posterior portion of the hepatic graft, suggesting the possibility of right IPA bleeding, was more frequently seen on CT (57%). Consequently, sudden development of acute hematoma in the posterior aspect of the hepatic graft, and extravasation of contrast material in the same region on CT, are thought to be predictive CT findings of IPA bleeding in posttransplantation patients.
In conclusion, IPA bleeding frequently occurred within the first 2 weeks after liver transplantation, especially in recipients who underwent living donor transplantation because of liver cirrhosis or hepatocellular carcinoma. Loculated acute hematoma and the extravasation of contrast media in the posterior portion of the hepatic graft are common predictive CT findings of IPA bleeding, which is well depicted by MDCT. Manifestation of sudden hypotension, a decrease in hemoglobin, or fresh blood drainage from in-dwelling drainage tubes in the early postoperative period requires prompt and thorough attention. CT is helpful in diagnosing IPA bleeding, which can prevent the progression into an undesirable clinical status that requires surgical management.
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