DOI:10.2214/AJR.07.2691
AJR 2008; 191:1046-1056
© American Roentgen Ray Society
MDCT Evaluation of Central Airway and Vascular Complications of Lung Transplantation
Ritu R. Gill1,
Angeline C. Poh1,
Phillip C. Camp2,
Jean M. Allen1,
Mark T. Delano1,
Francine L. Jacobson1,
Andetta Hunsaker1 and
Yolonda L. Colson2
1 Department of Radiology, Brigham and Women's Hospital, 75 Francis St., Boston,
MA 02115.
2 Division of Thoracic Surgery, Brigham and Women's Hospital, Boston, MA.
Received June 6, 2007;
accepted after revision May 4, 2008.
Address correspondence to R. R. Gill
(rgill{at}partners.org).
CME
This article is available for CME credit. See
www.arrs.org
for more information.
Abstract
OBJECTIVE. The purpose of this article is to illustrate the spectrum
of central airway and vascular complications in lung transplantation using
MDCT, with an emphasis on the usefulness of advanced postprocessing
techniques.
CONCLUSION. MDCT is an invaluable tool in the diagnosis, evaluation,
and posttreatment assessment of central airway and vascular complications in
lung transplant recipients. Advanced postprocessing techniques provide
complementary information that is visually accessible and anatomically
meaningful for the clinician.
Keywords: airway complications • lung transplantation • MDCT • vascular complications
Introduction
Lung transplantation is a life-saving procedure for many patients with
end-stage lung disease. With continuing improvements in surgical technique,
immunosuppressive therapy, and antimicrobial prophylaxis, the 1-year survival
rate may be as high as 81% [1].
However, central airway and vascular complications can compromise the function
of the transplanted lung and increase mortality. Airway complications have
been reported in up to 27% of patients
[2]. Vascular anastomotic
stenosis is less common but is associated with a high mortality rate if left
untreated [3]. Other
complications include pulmonary embolism and tracheobronchomalacia.
The traditional methods of assessing the airways and
vasculature—bronchoscopy and pulmonary angiography—are accurate
but invasive and provide only a partial picture of the pathophysiology and
show an incomplete relationship to surrounding structures.
In contrast, MDCT generates true isotropic voxels that allow advanced
postprocessing techniques—multiplanar reformations (MPRs), volume
rendering, virtual bronchoscopy, and minimum-intensity-projection and
maximum-intensity-projection (MIP) images—that help display the
complication and relevant anatomy in a manner familiar to the clinician. MDCT
has an established role in pretransplantation evaluation; it not only helps
evaluate the extent and severity of the abnormality but also aids in
evaluating donor and recipient size and volume measurements and in alerting
the surgeon about an incidental malignancy or infection.
In this article, we describe the role of MDCT in diagnosing and guiding
management in a variety of central airway and vascular complications after
lung transplantation, with an emphasis on the usefulness of advanced
postprocessing techniques.
MDCT Protocol
Posttransplantation evaluations were performed with a Sensation 64-MDCT
scanner (Siemens Medical Solutions) using our airway protocol, which includes
imaging during two phases of respiration: end-inspiratory (imaging during
suspended end-inspiration) and continuous dynamic expiratory (imaging during
forceful exhalation). Before scanning, initial scout topographic images were
obtained to determine the area of coverage, which includes the trachea and
central bronchi, corresponding to a length of approximately 10–12
cm.
Scanning was performed in a craniocaudal dimension for both end-inspiratory
and dynamic expiratory scans. End-inspiratory scanning was performed first in
all patients using 120 kVp, 0.6-mm collimation, high-speed mode, a pitch
equivalent of 1.5, slice interval of 1.25 mm, and slice thickness of 0.75 mm.
After the end-inspiratory scan, patients were coached with instructions for
the dynamic expiratory component of the scan (40 mA, 120 kVp, 0.6-mm
collimation, high-speed mode, and a pitch equivalent of 1.5). For this
sequence, patients were instructed to take a deep breath in and to blow it out
during the CT acquisition, which was coordinated to begin with the onset of
the forced expiratory effort; images were acquired while the patient was
breathing out. To minimize radiation exposure, a low-dose technique (40 mA)
was used for the dynamic expiratory scanning.
For CT pulmonary angiography, the imaging protocol consists of collimation,
0.6 mm; slice thickness, 1 mm; slice interval, 0.5 mm; and 100 kVp with
automatic tube current adjustment. Seventy-five milliliters of contrast
material (Ultravist 370 [iopromide]), Bayer HealthCare [formerly Schering])
was administered IV at 4 mL/s using an automated power injector. An automated
bolus tracking technique was used to determine the scanning delay.
Image postprocessing was performed using a dedicated workstation (Voxar,
Barco) by experienced technicians in our 3D laboratory under the supervision
of a thoracic radiologist.
Patients are traditionally followed up after lung transplantation with
daily chest radiography, and CT is performed if there is unexplained
deterioration in the patient's condition. Early imaging can be critical in
changing patient management but depends on the clinical scenario. The CT
protocol is governed by the patient's symptomatology and clinical
presentation. Because both airway and vascular complications can present with
dyspnea, image planning and the decision to administer IV contrast material
are crucial. If deterioration is seen on pulmonary function tests or if there
is an unexplained air leak on the recent portable chest radiograph, an airway
complication is suspected. If new or recurrent pulmonary hypertension or heart
strain is seen on echocardiography, a vascular complication is suspected, and
IV contrast material is administered after discussion with the transplant
team. Expiratory images are acquired if deterioration occurs in pulmonary
function test results or if tracheobronchomalacia is suspected, specifically
to assess for bronchiolitis obliterans. Close collaboration and interaction
with the transplant team is a vital part of imaging and reporting in this
cohort; joint review of the images with the transplant surgeons and
pulmonologists is necessary for optimal patient outcome.
Central Airway Complications
Bronchial Anastomotic Dehiscence
Dehiscence of the bronchial anastomosis was a major cause of morbidity in
the early era of lung transplantation and is often attributed to interruption
of the bronchial arterial supply, which is divided at the time of surgery.
Donor–recipient mismatch, poor lymphatic drainage, acute rejection, and
infection are contributing factors
[4]. Bronchoscopy is the gold
standard for evaluating the bronchial anastomosis, but pulmonary secretions,
sloughed mucosa, and distorted postoperative anatomy may hamper assessment.
Bronchial dehiscence is suspected on MDCT when extraluminal pockets of gas are
visualized in and around the anastomosis. Depending on the type of anastomosis
(end-to-end or telescoping), the location of gas in relation to the airway is
important in making the correct diagnosis
[5]. Axial images alone may be
insufficient for this purpose. MPRs and minimum intensity projections are
superior in depicting the communication of extraluminal air with the airway
(Fig. 1).
View larger version (30K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1 —Bronchial anastomotic dehiscence. Schematic diagram shows
telescoped anastomosis (A). In B, blue arrow indicates infold or
pseudodiverticulum (other blue arrows indicate air). Purple arrow shows
contained leak, a small pocket of air trapped in omental wrap. Note that air
pocket does not communicate with airway. Drawings C–E show
development of dehiscence and its progression. Membranous part of trachea is
the most vulnerable. Extraluminal air communicates with airway and progresses
if not diagnosed early.
|
|
In an uneventful transplantation, normal extraluminal air in the
mediastinum or pleurae can be seen up to 2–3 weeks, but there should be
no free air by 4 weeks. If a new or unexplained air leak occurs, in the form
of either a pneumothorax or a pneumomediastinum (Figs.
2A,
2B,
2C,
2D,
2E,
2F and
3; see also supplemental Fig.
S2 at
www.ajronline.org),
further MDCT evaluation is warranted. Extraluminal gas can be seen if there is
a pneumomediastinum that does not communicate with the airways. This is most
commonly seen when there is a global size mismatch between the recipient and
donor lungs, leaving a potential space in which free air can occupy the
peribronchial space and mobilized mediastinum. Extraluminal pockets of air can
also be seen if there is a contained leak at the time of surgery; this air
pocket is trapped in the omentum but does not communicate with the
anastomosis. Pseudodiverticulum, or an infolding of the airway at the level of
the telescoped anastomosis (Fig.
4A,
4B,
4C,
4D,
4E), is caused by the surgical
technique. Tracheal diverticula (Fig.
5), generally seen adjacent to the proximal trachea, and
occasionally a tracheal bronchus that has been ligated (Fig.
6A,
6B,
6C) can also been seen in this
cohort.
View larger version (144K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 2A —60-year-old man who underwent double lung transplantation for
idiopathic pulmonary fibrosis. Axial CT image of thorax shows bilateral
pneumothoraces (horizontal arrows). Right main bronchus is minimally
irregular (vertical arrow).
|
|
View larger version (144K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 2B —60-year-old man who underwent double lung transplantation for
idiopathic pulmonary fibrosis. Axial CT image in more cranial plane suggests
irregular pocket of gas in region of right bronchial anastomosis
(arrow).
|
|
View larger version (133K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 2C —60-year-old man who underwent double lung transplantation for
idiopathic pulmonary fibrosis. Coronal minimum-intensity-projection image
clearly shows lobulated collection of gas measuring 0.8 x 0.4 cm just
inferior to and communicating with right bronchial anastomosis
(arrow) that is consistent with bronchial dehiscence.
|
|
View larger version (116K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 2D —60-year-old man who underwent double lung transplantation for
idiopathic pulmonary fibrosis. Volume-rendering model shows communication
between gas pocket and right bronchial anastomosis (arrow). Despite
attempts at conservative therapy, patient eventually required surgery to
repair bronchial dehiscence. See also Figure S2, cine image, at
www.ajronline.org.
|
|
View larger version (42K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 2E —60-year-old man who underwent double lung transplantation for
idiopathic pulmonary fibrosis. Volume-rendering model shows communication
between gas pocket and right bronchial anastomosis (arrow). Despite
attempts at conservative therapy, patient eventually required surgery to
repair bronchial dehiscence. See also Figure S2, cine image, at
www.ajronline.org.
|
|
View larger version (47K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 2F —60-year-old man who underwent double lung transplantation for
idiopathic pulmonary fibrosis. Volume-rendering model shows communication
between gas pocket and right bronchial anastomosis (arrow). Despite
attempts at conservative therapy, patient eventually required surgery to
repair bronchial dehiscence. See also Figure S2, cine image, at
www.ajronline.org.
|
|
View larger version (86K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 3 —30-year-old man who underwent double lung transplantation.
Axial CT image shows pneumothorax (straight green arrow),
pneumomediastinum (curved green arrow), pneumatocele (blue
arrow), and subcutaneous emphysema (white arrow).
|
|
View larger version (77K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 4A —39-year-old man with pulmonary fibrosis who underwent double
lung transplantation. Axial (A), coronal (B and C), and
volume-rendered (D and E) CT images show pseudodiverticulum
(arrow) along telescoped anastomosis on left. Insets
(A–C) show pseudodiverticulum in different planes.
|
|
View larger version (132K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 4B —39-year-old man with pulmonary fibrosis who underwent double
lung transplantation. Axial (A), coronal (B and C), and
volume-rendered (D and E) CT images show pseudodiverticulum
(arrow) along telescoped anastomosis on left. Insets
(A–C) show pseudodiverticulum in different planes.
|
|
View larger version (118K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 4C —39-year-old man with pulmonary fibrosis who underwent double
lung transplantation. Axial (A), coronal (B and C), and
volume-rendered (D and E) CT images show pseudodiverticulum
(arrow) along telescoped anastomosis on left. Insets
(A–C) show pseudodiverticulum in different planes.
|
|
View larger version (66K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 4D —39-year-old man with pulmonary fibrosis who underwent double
lung transplantation. Axial (A), coronal (B and C), and
volume-rendered (D and E) CT images show pseudodiverticulum
(arrow) along telescoped anastomosis on left. Insets
(A–C) show pseudodiverticulum in different planes.
|
|
View larger version (110K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 4E —39-year-old man with pulmonary fibrosis who underwent double
lung transplantation. Axial (A), coronal (B and C), and
volume-rendered (D and E) CT images show pseudodiverticulum
(arrow) along telescoped anastomosis on left. Insets
(A–C) show pseudodiverticulum in different planes.
|
|
View larger version (103K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 6A —23-year-old woman who underwent double lung transplantation.
Axial (A) and coronal (B) posttransplantation and coronal
pretransplantation (C) CT images show tracheal bronchus
(arrow) that was ligated and ends as blind pouch in mediastinum.
|
|
View larger version (158K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 6B —23-year-old woman who underwent double lung transplantation.
Axial (A) and coronal (B) posttransplantation and coronal
pretransplantation (C) CT images show tracheal bronchus
(arrow) that was ligated and ends as blind pouch in mediastinum.
|
|
View larger version (107K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 6C —23-year-old woman who underwent double lung transplantation.
Axial (A) and coronal (B) posttransplantation and coronal
pretransplantation (C) CT images show tracheal bronchus
(arrow) that was ligated and ends as blind pouch in mediastinum.
|
|
Bronchial Stenosis
The prevalence of bronchial stenosis after lung transplantation ranges from
10% to 15% [4]. Bronchial
stenosis can occur at the anastomosis or in the central airways distal to the
anastomosis; potential mechanisms for the development of airway narrowing
include ischemic injury after the division of the bronchial artery. Stenosis
in the central bronchi distal from the anastomosis can be seen in
approximately 75% of cases and is generally related to local ischemia,
technical complications, and size mismatch.
Bronchoscopic assessment is useful but does not provide extraluminal
information and may be limited if there is a high-grade stenosis. Assessment
of axial CT images alone may result in underestimation of the severity of
stenosis [6]. MPRs and virtual
bronchoscopy allow more accurate determination of the extent and degree of
stenosis and are useful for treatment planning
[7]. The extent of airway
narrowing is categorized as grade 0 (no narrowing), grade 1 (
50%
narrowing), and grade 2 (> 50% narrowing)
[8]. Curved reformations are
the most accurate in providing the measurements and are vital in ordering
customized airway stents. Using a curved reformation—which is acquired
after using the manual mode to deposit a cursor pointin the center of the
lumen of the trachea and bronchi—the airways are mapped, using a fixed
reference point such as the carina or the vocal cords. Linear and
circumferential measurements at, above, and below the stenosis are provided
using the vessel metrics function on the Voxar workstation, thereby enabling
customized stent placement.
Bronchial strictures can be treated with bronchoscopic dilation, laser
débridement, or stenting. After treatment, MDCT can be used to evaluate
bronchial patency and optimal stent placement and to assess stent
complications such as fracture, migration, or compression of adjacent
structures [9] (Figs.
7A,
7B,
7C,
7D,
7E,
7F,
7G,
7H and
8A,
8B,
8C,
8D; see also supplemental
Figs. S7 and S8 at
www.ajronline.org).
View larger version (116K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 7A —25-year-old man with cystic fibrosis who underwent double
lung transplantation. Patient developed shortness of breath several months
after surgery. See also Figure S7, AVI images, at
www.ajronline.org.
Axial thoracic CT image shows collapse of right upper lobe and anterior
displacement of oblique fissure (arrow).
|
|
View larger version (120K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 7B —25-year-old man with cystic fibrosis who underwent double
lung transplantation. Patient developed shortness of breath several months
after surgery. See also Figure S7, AVI images, at
www.ajronline.org.
Axial (B) and coronal (C) CT images of thorax in more caudal
plane show cause to be possible stricture (black and white
arrows) at origin of right upper lobe bronchus and stenosis of bronchus
intermedius.
|
|
View larger version (112K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 7C —25-year-old man with cystic fibrosis who underwent double
lung transplantation. Patient developed shortness of breath several months
after surgery. See also Figure S7, AVI images, at
www.ajronline.org.
Axial (B) and coronal (C) CT images of thorax in more caudal
plane show cause to be possible stricture (black and white
arrows) at origin of right upper lobe bronchus and stenosis of bronchus
intermedius.
|
|
View larger version (133K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 7D —25-year-old man with cystic fibrosis who underwent double
lung transplantation. Patient developed shortness of breath several months
after surgery. See also Figure S7, AVI images, at
www.ajronline.org.
Coronal reformatted CT image after dilatation of right upper lobe stricture
and stenting of bronchus intermedius shows improved patency (black
arrow) and reexpansion of right upper lobe.
|
|
View larger version (115K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 7E —25-year-old man with cystic fibrosis who underwent double
lung transplantation. Patient developed shortness of breath several months
after surgery. See also Figure S7, AVI images, at
www.ajronline.org.
Sagittal reformatted CT image after stenting shows patency of right upper lobe
bronchus (arrow).
|
|
View larger version (111K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 7F —25-year-old man with cystic fibrosis who underwent double
lung transplantation. Patient developed shortness of breath several months
after surgery. See also Figure S7, AVI images, at
www.ajronline.org.
Complementary virtual bronchoscopy images illustrate patency of right main
bronchial anastomosis and right upper lobe bronchus. Image looking down from
carina (F) into right mainstem bronchus (blue arrow) shows
origin of right upper lobe bronchus and patency of bronchus intermedius. Image
from trachea looking inferiorly at carina (G) shows patency of
anastomosis of both right and left mainstem bronchi.
|
|
View larger version (124K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 7G —25-year-old man with cystic fibrosis who underwent double
lung transplantation. Patient developed shortness of breath several months
after surgery. See also Figure S7, AVI images, at
www.ajronline.org.
Complementary virtual bronchoscopy images illustrate patency of right main
bronchial anastomosis and right upper lobe bronchus. Image looking down from
carina (F) into right mainstem bronchus (blue arrow) shows
origin of right upper lobe bronchus and patency of bronchus intermedius. Image
from trachea looking inferiorly at carina (G) shows patency of
anastomosis of both right and left mainstem bronchi.
|
|
View larger version (131K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 7H —25-year-old man with cystic fibrosis who underwent double
lung transplantation. Patient developed shortness of breath several months
after surgery. See also Figure S7, AVI images, at
www.ajronline.org.
Volume-rendered image shows patent right upper lobe bronchus (black
arrow) and stent in bronchus intermedius (white arrow).
|
|
View larger version (130K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 8A —54-year-old man who underwent single left lung
transplantation for idiopathic pulmonary fibrosis. Patient had earlier
developed left pulmonary artery anastomotic stenosis for which stent was
placed. He became increasingly short of breath several weeks after stent was
deployed. See also Figure S8, cine images, at
www.ajronline.org.
Coronal unenhanced axial CT scan of thorax reveals mass effect from pulmonary
artery stent resulting in stenosis of left main bronchus (arrow).
|
|
View larger version (140K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 8B —54-year-old man who underwent single left lung
transplantation for idiopathic pulmonary fibrosis. Patient had earlier
developed left pulmonary artery anastomotic stenosis for which stent was
placed. He became increasingly short of breath several weeks after stent was
deployed. See also Figure S8, cine images, at
www.ajronline.org.
Volume-rendered image clearly shows relationship of stent to left bronchial
narrowing (arrow).
|
|
View larger version (131K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 8C —54-year-old man who underwent single left lung
transplantation for idiopathic pulmonary fibrosis. Patient had earlier
developed left pulmonary artery anastomotic stenosis for which stent was
placed. He became increasingly short of breath several weeks after stent was
deployed. See also Figure S8, cine images, at
www.ajronline.org.
Curved reformation acquired after manually inserting cursor point in center of
airways allows accurate measurement of stenoses, which are graded as mild,
moderate, or severe. Additional cross-sectional measurements of airways at
normal airway proximal, distal, and at level of stenosis, along with length of
stenosis, are provided and aid in planning stent. 1 = trachea, 2 = point
proximal to stenosis showing normal diameter of left main bronchus, 3 =
diameter of stenotic segment.
|
|
View larger version (108K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 8D —54-year-old man who underwent single left lung
transplantation for idiopathic pulmonary fibrosis. Patient had earlier
developed left pulmonary artery anastomotic stenosis for which stent was
placed. He became increasingly short of breath several weeks after stent was
deployed. See also Figure S8, cine images, at
www.ajronline.org.
Coronal CT image after bronchial stent placement clearly shows patent left
main bronchus (black arrow). White arrow indicates pulmonary artery
stent.
|
|
Tracheobronchomalacia
Tracheobronchomalacia may result from prolonged intubation, trauma,
infection, or chronic inflammation. It is characterized by excessive airway
collapse due to abnormal weakness of the airway walls and cartilage and
flaccidity of the membranous portion of the trachea
[10]. Diagnosis using MDCT is
made when the cross-sectional area of the airway is decreased by 50% or more
at expiration or during coughing
[11]. A high index of
suspicion is required to avoid missing the diagnosis because many patients
have dyspnea in the postoperative period. Bronchoscopy is challenging because
life-threatening airway obstruction and pulmonary edema may be precipitated
with severe tracheobronchomalacia. Paired inspiratory and dynamic expiratory
scanning and virtual bronchoscopy during respiration and forced exhalation can
provide visual and functional information regarding the extent of collapse
[12] (Fig.
9A,
9B,
9C).
View larger version (131K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 9A —54-year-old man who underwent left lung transplantation for
idiopathic pulmonary fibrosis. CT image shows "frown sign" of
tracheobronchomalacia (arrow). Marked collapse of trachea of more
than 50% was seen incidentally on CT of thorax performed for evaluation of
patient's pneumonia.
|
|
View larger version (111K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 9B —54-year-old man who underwent left lung transplantation for
idiopathic pulmonary fibrosis. Dynamic inspiratory (B) and expiratory
(C) virtual bronchoscopy images confirm diagnosis of
tracheobronchomalacia. Image from trachea looking inferiorly at right and left
mainstem bronchi in inspiration (B) shows normal diameter of central
airways. In expiration (C), note marked collapse and associated
decrease in diameter of trachea, which is consistent with
tracheobronchomalacia.
|
|
View larger version (126K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 9C —54-year-old man who underwent left lung transplantation for
idiopathic pulmonary fibrosis. Dynamic inspiratory (B) and expiratory
(C) virtual bronchoscopy images confirm diagnosis of
tracheobronchomalacia. Image from trachea looking inferiorly at right and left
mainstem bronchi in inspiration (B) shows normal diameter of central
airways. In expiration (C), note marked collapse and associated
decrease in diameter of trachea, which is consistent with
tracheobronchomalacia.
|
|
Vascular Complications
Pulmonary Artery Anastomotic Stenosis
Vascular anastomotic complications are relatively uncommon but have a high
mortality rate [3].
Donor–recipient size mismatch, surgical technique, and twisting,
stricture, or thromboses of the pulmonary artery have been cited as causes. In
single lung transplantation, poor blood flow dynamics in the lung, increased
airway compliance, and increased vascular resistance of the diseased native
lung typically result in a preferential shift of perfusion to the transplanted
lung within hours of surgery. Pulmonary artery compromise should be suspected
when the patient experiences unexplained hypoxia or new or recurrent pulmonary
hypertension.
MDCT is a noninvasive alternative to angiography and can define the extent
and degree of stenosis and the presence of collateral pathways
[13] (Fig.
10A,
10B,
10C,
10D; see also supplemental
Fig. S10 at
www.ajronline.org).
MDCT can be used to assess posttreatment results (Fig.
11A,
11B,
11C,
11D) and, most important,
provides an ability to compare images serially.
View larger version (107K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 10A —40-year-old woman who underwent single left lung
transplantation for emphysema. CT pulmonary angiography was performed for
suspected pulmonary embolism. See also Figure S10, AVI images, at
www.ajronline.org.
Axial CT image shows complete occlusion of left pulmonary artery anastomosis
(arrow).
|
|
View larger version (108K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 10B —40-year-old woman who underwent single left lung
transplantation for emphysema. CT pulmonary angiography was performed for
suspected pulmonary embolism. See also Figure S10, AVI images, at
www.ajronline.org.
Maximum-intensity-projection axial (B) and coronal (C) images
show occlusion of left pulmonary artery and no distal arterial supply. Left
bronchial collaterals are also present (arrow).
|
|
View larger version (103K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 10C —40-year-old woman who underwent single left lung
transplantation for emphysema. CT pulmonary angiography was performed for
suspected pulmonary embolism. See also Figure S10, AVI images, at
www.ajronline.org.
Maximum-intensity-projection axial (B) and coronal (C) images
show occlusion of left pulmonary artery and no distal arterial supply. Left
bronchial collaterals are also present (arrow).
|
|
View larger version (122K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 10D —40-year-old woman who underwent single left lung
transplantation for emphysema. CT pulmonary angiography was performed for
suspected pulmonary embolism. See also Figure S10, AVI images, at
www.ajronline.org.
Pulmonary angiogram reveals abrupt cutoff at orifice of left main pulmonary
artery that could not be cannulated. Turbulent retrograde contrast flow is
shown at site of stenosis (white arrow). Pulmonary vein branches are
seen in upper left chest (black arrow).
|
|
View larger version (124K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 11A —54-year-old man who underwent single left lung
transplantation for idiopathic pulmonary fibrosis. CT pulmonary angiography
was performed for suspected pulmonary embolism. Axial CT image shows tight
stricture at left pulmonary artery stenosis (black arrow). Note
dilatation of central pulmonary arteries from recurrent pulmonary hypertension
(white arrow).
|
|
View larger version (129K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 11B —54-year-old man who underwent single left lung
transplantation for idiopathic pulmonary fibrosis. CT pulmonary angiography
was performed for suspected pulmonary embolism. Axial (B) and coronal
(C) CT images of thorax after insertion of metallic Wallstent
(arrow) show satisfactory positioning and patency of left main
pulmonary artery.
|
|
View larger version (116K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 11C —54-year-old man who underwent single left lung
transplantation for idiopathic pulmonary fibrosis. CT pulmonary angiography
was performed for suspected pulmonary embolism. Axial (B) and coronal
(C) CT images of thorax after insertion of metallic Wallstent
(arrow) show satisfactory positioning and patency of left main
pulmonary artery.
|
|
View larger version (95K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 11D —54-year-old man who underwent single left lung
transplantation for idiopathic pulmonary fibrosis. CT pulmonary angiography
was performed for suspected pulmonary embolism. Pulmonary angiogram confirms
diagnosis of tight stricture (arrow) of left pulmonary artery
anastomosis.
|
|
Pseudoaneurysm
Pseudoaneurysms of the carotid or subclavian arteries can develop in
patients after lung transplantation when these vessels are inadvertently
injured during central line placement. Large pseudoaneurysms can cause
compression of surrounding structures, hemodynamic instability, dissection,
thrombosis, or embolization. MPR, MIP, and 3D volume-rendered angiographic
views are useful for pretreatment planning (Fig.
12A,
12B,
12C).
View larger version (139K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 12A —46-year-old woman who underwent double lung transplantation
10 years previously for cystic fibrosis and who had history of repeated right
subclavian vein line insertions. Patient developed painless right lower neck
mass. Chest radiograph after attempted insertion of central venous catheter
reveals right paratracheal opacity (arrow) causing deviation of
trachea to right.
|
|
View larger version (143K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 12B —46-year-old woman who underwent double lung transplantation
10 years previously for cystic fibrosis and who had history of repeated right
subclavian vein line insertions. Patient developed painless right lower neck
mass. Coronal contrast-enhanced CT image of neck and thoracic inlet shows
focal dilatation of proximal right subclavian artery and mural thrombus
(arrow).
|
|
View larger version (123K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 12C —46-year-old woman who underwent double lung transplantation
10 years previously for cystic fibrosis and who had history of repeated right
subclavian vein line insertions. Patient developed painless right lower neck
mass. Right upper limb angiography confirms presence of pseudoaneurysm of
proximal right subclavian artery (arrow). Pseudoaneurysm was removed
surgically, and patient underwent grafting of right subclavian artery.
|
|
Pulmonary Embolism
The incidence of pulmonary embolism in patients after lung transplantation
has been reported to be as high as 27%, with 40% of those patients going on to
have an infarction [14,
15]. Prolonged immobility and
hypercoagulable postsurgical states have been cited as reasons for the high
incidence in this population
[16]. MDCT findings include an
intraluminal filling defect and an abrupt cutoff of a vessel.
MPRs and MIPs are especially useful in differentiating mucus-filled airways
or lymph nodes from pulmonary emboli (Fig.
13A,
13B) and in an isolated
subsegmental embolus. In addition, they are also useful in identifying an
abrupt cutoff of a vessel, a finding that may be quite subtle on axial images,
particularly in smaller vessels.
View larger version (103K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 13A —34-year-old man who underwent double lung transplantation for
cystic fibrosis. Patient also had acute shortness of breath, elevated D-dimer
level, and new pulmonary hypertension. Axial (A) and coronal oblique
(B) maximum-intensity-projection CT pulmonary angiography images show
nonocclusive filling defect in left lower lobe pulmonary artery (white
arrow). Black arrow (B) indicates mild stenosis involving left
main pulmonary artery at vascular anastomotic site.
|
|
View larger version (109K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 13B —34-year-old man who underwent double lung transplantation for
cystic fibrosis. Patient also had acute shortness of breath, elevated D-dimer
level, and new pulmonary hypertension. Axial (A) and coronal oblique
(B) maximum-intensity-projection CT pulmonary angiography images show
nonocclusive filling defect in left lower lobe pulmonary artery (white
arrow). Black arrow (B) indicates mild stenosis involving left
main pulmonary artery at vascular anastomotic site.
|
|
Summary
Knowledge of the spectrum of MDCT appearances of these complications is
valuable in the diagnosis, pretreatment planning, and assessment of
posttreatment complications. Three-dimensional postprocessing techniques are
invaluable in defining anatomic relationships and accurately assessing
stenosis; they can provide important functional information in a manner that
is both visually accessible and anatomically meaningful to the clinician and
surgeon. Familiarity with these techniques can help the radiologist make rapid
and accurate evaluations, bolster diagnostic confidence, and improve patient
outcomes.
References
- Cooper JD, Patterson GA, Trulock EP. Results of single and
bilateral lung transplantation in 131 consecutive recipients. Washington
University Lung Transplant Group. J Thorac Cardiovasc
Surg 1994; 107:460
–470; discussion 470–461[Abstract/Free Full Text]
- Saad CP, Ghamande SA, Minai OA, et al. The role of self-expandable
metallic stents for the treatment of airway complications after lung
transplantation. Transplantation 2003;75
:1532
–1538[Medline]
- Clark SC, Levine AJ, Hasan A, Hilton CJ, Forty J, Dark JH. Vascular
complications of lung transplantation. Ann Thorac Surg1996; 61:1079
–1082[CrossRef][Medline]
- Shennib H, Massard G. Airway complications in lung transplantation.
Ann Thorac Surg 1994;57
: 506–511[Abstract]
- McAdams HP, Murray JG, Erasmus JJ, Goodman PC, Tapson VF, Davis RD.
Telescoping bronchial anastomoses for unilateral or bilateral sequential lung
transplantation: CT appearance. Radiology1997; 203:202
–206[Abstract/Free Full Text]
- Quint LE, Whyte RI, Kazerooni EA, et al. Stenosis of the central
airways: evaluation by using helical CT with multiplanar reconstructions.
Radiology 1995;194
: 871–877[Abstract/Free Full Text]
- McAdams HP, Palmer SM, Erasmus JJ, et al. Bronchial anastomotic
complications in lung transplant recipients: virtual bronchoscopy for
noninvasive assessment. Radiology 1998;209
: 689–695[Abstract/Free Full Text]
- Hoppe H, Dinkel HP, Walder B, von Allmen G, Gugger M, Vock P.
Grading airway stenosis down to the segmental level using virtual
bronchoscopy. Chest 2004;125
: 704–711[CrossRef][Medline]
- Ferretti GR, Kocier M, Calaque O, et al. Follow-up after stent
insertion in the tracheobronchial tree: role of helical computed tomography in
comparison with fiberoptic bronchoscopy. Eur Radiol2003; 13:1172
–1178[Medline]
- Johnson TH, Mikita JJ, Wilson RJ, Feist JH. Acquired
tracheomalacia. Radiology 1973;109
: 576–580[Medline]
- Hein E, Rogalla P, Hentschel C, Taupitz M, Hamm B. Dynamic and
quantitative assessment of tracheomalacia by electron beam tomography:
correlation with clinical symptoms and bronchoscopy. J Comput
Assist Tomogr 2000; 24:247
–252[CrossRef][Medline]
- Boiselle PM, Feller-Kopman D, Ashiku S, Weeks D, Ernst A.
Tracheobronchomalacia: evolving role of dynamic multislice helical CT.
Radiol Clin North Am 2003;41
: 627–636[CrossRef][Medline]
- Soyer P, Devine N, Frachon I, et al. Computed tomography of
complications of lung transplantation. Eur Radiol1997; 7:847
–853[CrossRef][Medline]
- Burns KE, Iacono AT. Incidence of clinically unsuspected pulmonary
embolism in mechanically ventilated lung transplant recipients.
Transplantation 2003;76
: 964–968[CrossRef][Medline]
- Burns KE, Iacono AT. Pulmonary embolism on postmortem examination:
an under-recognized complication in lung-transplant recipients?
Transplantation 2004;77
: 692–698[CrossRef][Medline]
- Izbicki G, Bairey O, Shitrit D, Lahav J, Kramer MR. Increased
thromboembolic events after lung transplantation.
Chest 2006; 129:412
–416[CrossRef][Medline]
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
Top
Abstract
Introduction
