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 Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 7  |  Issue : 2  |  Page : 149-157

Multidetector computed tomographic evaluation of complications following lung transplantation with clinical correlation: A single center experience from India


1 Department of Radiology, Apollo Hospitals, Chennai, Tamil Nadu, India
2 Department of Heart and Lung Transplantation, Apollo Hospitals, Chennai, Tamil Nadu, India

Date of Submission25-Mar-2021
Date of Decision08-Jul-2021
Date of Acceptance09-Jul-2021
Date of Web Publication31-Aug-2021

Correspondence Address:
Yvette Kirubha Jayakar David Livingstone
G2 Firms Kalvoy Enclave, 127 Medavakkam Tank Road, Kilpauk, Chennai - 600 010, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jpcs.jpcs_17_21

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  Abstract 


Context: Lung transplantation (LT) is now being performed for end-stage lung and heart-lung disease in a few centers in India. Experience in multidetector computed tomography (MDCT) evaluation of posttransplant complications is currently limited and evolving. Aims: This study analyses the early experience in our center regarding the imaging features of complications following LT with clinical outcome correlation and identify the role of MDCT. Methodology: A retrospective study of patients who underwent LT and had MDCT imaging from January 2017 to March 2019 was performed. There were 22 patients in this period whose clinical course and CT scans were studied. Results: The complications encountered include pleural effusions, atelectasis, bronchostenosis, and reperfusion injury. Rare complications included pulmonary thromboembolism and rejection. The accuracy of computed tomography (CT) imaging in airway evaluation was high but was limited in characterization of consolidation as either infective or noninfective. Conclusions: CT is the noninvasive imaging modality of choice in evaluating chronic rejection, airway complications such as bronchostenosis and pulmonary thromboembolism. Clinical, laboratory, and biopsy correlation are needed to diagnose infection or acute rejection, both of which can present with consolidation. Temporal evaluation of events is critical. Familiarity and awareness by the radiologist are crucial for good clinical outcome.

Keywords: Bronchiolitis obliterans, bronchostensosis, lung transplantation, rejection


How to cite this article:
Livingstone YK, Sunder T, Dhanuka T, Sunder K, Thangaraj PR, Kuppuswamy MK. Multidetector computed tomographic evaluation of complications following lung transplantation with clinical correlation: A single center experience from India. J Pract Cardiovasc Sci 2021;7:149-57

How to cite this URL:
Livingstone YK, Sunder T, Dhanuka T, Sunder K, Thangaraj PR, Kuppuswamy MK. Multidetector computed tomographic evaluation of complications following lung transplantation with clinical correlation: A single center experience from India. J Pract Cardiovasc Sci [serial online] 2021 [cited 2021 Dec 1];7:149-57. Available from: https://www.j-pcs.org/text.asp?2021/7/2/149/325219




  Introduction Top


Imaging plays a crucial role in the preoperative assessment, selection of cases for lung transplantation (LT), postoperative management, evaluation, and follow-up. The main stay of imaging is the chest radiograph with multidetector computed tomography (MDCT), its use directed to answering specific questions. Given the endemicity of tuberculosis in India, MDCT has a major preoperative role in assessing lung parenchyma as well as the mediastinum of donors.

The first human LT in the world was performed by Dr Hardy in 1963.[1] In India, LT is still not widely performed, although the first heart-lung transplant (HLT) in India was done by Cherian et al. as early as in 1999 in Chennai.[2] After the initial interest, there followed a period of inactivity until 2011, when the first single-lung transplant (SLT) was done simultaneously at Apollo Hospitals and Global Hospitals in Chennai, but first reported in 2013.[3] The first Indian public sector effort was in Chandigarh in 2019; however, the patient succumbed to immediate complications.[4] In India, LT is now regularly being performed in a few cities such as Chennai(Tamil Nadu), Hyderabad (Telangana), Bengaluru (Karnataka) and Mumbai (Maharashtra), while it is slowly being performed in other cities of India, too.[5]

LT is indicated in cases with end-stage failure wherein all therapeutic options have been ineffective. Conditions causing end-stage lung disease fall under one of these categories: Obstructive and restrictive pattern of lung pathophysiology, primary pulmonary hypertension, bronchiectasis, and cystic fibrosis. The indications and appropriate time to refer for consideration for LT differ among the different categories and guidelines have been summarized by The International Society of Heart and Lung transplant 2014.[6] While current, active, or recently treated malignancy remains the most important absolute contraindication, there are many other absolute and relative contraindications. The overall survival rates are 89% at 3 months, 80% at 1 year, 65% at 3 years, 54% at 5 years, and 32% at 10 years.[7] The major complication rates are 10%–15% for early airway complications and 50% for bronchiolitis obliterans syndrome (BOS) at 5 years.[8] Rejection and infection remain the most common complications.[9]

The situation in India presents different challenges due to the relative lack of physician awareness, late presentation of patients, lack of widespread adequate technical support such as extracorporeal membrane oxygenation, expense involved and most importantly endemic nature of tuberculosis which has influence on recipient outcome and donor selection.[5] In India, as on date, the donor lung is harvested only from deceased donors. LT could either be SLT, double-lung transplant (DLT), and HLT based on recipient pathophysiology. The main issues related to immediate survival are primary graft dysfunction (PGD), infection, hyperacute, and acute rejection. In the West, rejection and PGD pose greater challenges, whereas in India, infections such as tuberculosis appear to be more challenging. The long-term complications include Chronic Lung Allograft Dysfunction either as BOS or Restrictive Allograft Syndrome, lymphoproliferative disorders, recurrence of primary disease, etc.

At our Institute, the lung transplant program was established since 2008. We have transplanted 151 lungs in 79 patients in different combinations of organ transplant including SLT, DLT and HLT, and combined Heart-Lung-Kidney transplantation. This is one of the largest lung transplant programs in India.

In this article, we have undertaken to retrospectively analyze the MDCT imaging findings of postlung transplant complications in one of the largest series in India. To the best of our knowledge, there is no such study done till date in India. We aim to analyze the MDCT imaging features of these complications to create the awareness and familiarity among both radiologists and transplant teams.


  Methodology Top


This is a retrospective observational study of CT scans of patients following lung and HLT from January 2017 to March 2019. A total of 33 scans in 22 patients were identified in this study period. Of these 22 patients, 19 patients had their surgery during the study period and three patients had their surgery 1 year before the study period [Table 1].
Table 1: Patient details

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During the study period, a total of 39 patients underwent lung and HLT, out of which 19 patients (48.7%) had computed tomography (CT) scans, while 20 patients (51.3%) did not have CT scans posttransplant [Table 2].
Table 2: Scan details

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All the 33 scans were obtained on a 160 slice multidetector CT scanner (Toshiba Aquilion Prime) with single breathold, 120 Kv, mA of 150 and 0.5 mm thickness images were acquired. Axial reconstructions were done at 2 mm in the mediastinal and lung window with overlap and at 1 mm with high-resolution CT protocol. Coronal and sagittal reformats were obtained in the lung window with 3 mm slice thickness. Most of the studies included end-expiratory scans as part of the protocol. Three-dimensional reconstructions, minimum intensity projections (mini MIP), and virtual bronchoscopy were done when required at the workstation (Vitrea version 6.7.3, Toshiba Medical Systems Corporation, Otawara, Japan). Pulmonary angiography protocol using 80 ml intravenous iodinated contrast and 20 ml saline (bolus triggered at 120HU, caudal to cranial) was followed when evaluating thromboembolism.

The scans were analyzed for their imaging features, diagnostic ability, and correlated with the clinical outcome and other investigations such as culture, biopsy, and bronchoscopy.


  Results Top


The mean age of the patients who underwent the scans was 62.5 years. The youngest patient was 24 years old and the eldest was 72 years old.

Fifteen patients (68%) were male and 7 patients (31%) were female. In 22 patients, 4 patients (18%) underwent SLT, and 14 patients (64%) underwent DLT and 4 patients (18%) underwent HLT. There was a total of 36 airway anastomoses (32 bronchial and 4 tracheal anastomoses).

Most of the patients had only one scan during this period 15 (68%), while some of them had multiple scans sometimes up to 4 (4.5%). Three (9%) of the scans were done in the early postoperative period (within 1 week). Majority of them were performed between intermediate (1 week to 2 months – 13 patients, 39%) and late (>2 months-17 patients, 51.5%) periods. Regarding the outcomes of these patients, survival analysis was considered.

When the survival analysis for the study period January 2017–March 2019 is considered, there are three subsets of patients as under:

  1. Group A: Twenty-two patients who have had CT scans after lung and heart- LT from January 2017 to March 2019. This includes 19 patients who had their transplant operation and CT scans in this period and three patients who were operated a year earlier, with CT scans done in the study period
  2. Group B: Nineteen patients who were BOTH operated and had CT scans in the study period. Excluding the three patients who had their operation 1 year before the study period
  3. Group C: All 39 patients who underwent lung and HLTs in the study period. This includes 19 patients who had CT scan and 20 patients who did not have CT scans. An overall survival for these 39 patients and comparison of survival for patients requiring CT scan (Group C1 = 19 patients) and patients who did not need CT scans (Group C2 = 16 patients).


The overall survival in these patients did not vary between the groups.

  • Group A: The 1, 2, 3, and 4-year survival was 85.7%, 81%, 81%, and 64.8%, respectively [Figure 1]
  • Group B: The 1, 2, and 3-year survival was 83.3%, 77.8%, and 77.8%, respectively [Figure 2]
  • Group C: The overall 1, 2, and 3-year survival was 76.6%, 76.6%, and 76.6%, respectively [Figure 3].
Figure 1: Kaplan–Meier Survival curve for patients who had computed tomography scans between January 2017 and March 2019 showing 1, 2, 3, 4-year survival of 85.7%, 81%, 81%, and 64.8%, respectively.

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Figure 2: Kaplan–Meier survival curves for all patients (35 patients) who were operated on between January 2017 and March 2019. This included 19 patients with computed tomography scans and 16 patients without computed tomography scan.

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Figure 3: Kaplan Meier curves comparing survival of 19 patients with (Green curve) and 16 patients without compute tomography scan (Red curve) operated between January 2017 and March 2019. No difference noted in survival between the 2 groups (P = 0.79 logrank test).

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The 1, 2, and 3-year survival in Group C1 (who had CT) as compared to Group C2 (who did not have CT) was 77.8% versus 75%, 77.8% versus 75%, and 77.8% versus 75%, respectively. There was no difference in the survival between the two groups (log rank test, P = 0.79) [Figure 3]. These suggest that requirement of CT scans which was mandated clinically was reflective of the morbidity among these patients but had no effect on mortality when compared to patients who did not require CT scan.

This article reflects the condition in India where LT is still very young and is continually evolving with data being accrued. It is hoped with the passage of time, more data will be available to allow detailed additional analysis. However, the reason for including this analysis is to emphasis that while CT scan was the modality of choice in diagnosing certain conditions and helped in treatment, the morbidity did not make any impact on the mortality. The curves between those with and without morbidity (and hence CT scan study) have been similar with no significant difference.

Clinical indications for computed tomography imaging

The main indication for the MDCT study, after LT, is increasing oxygen requirement in cases where definitive diagnosis is still elusive. Clinically, the main differential diagnosis includes mainly infection and rejection, while other differentials include airway complications, residual or increasing pleural space, and venous thromboembolism. While chest radiographs, clinical and laboratory parameters, bronchoscopy and bronchoalveolar lavage (BAL) help, in instances where the diagnosis is still uncertain, MDCT plays an important role in narrowing the differentials.

Computed tomography findings and impact on clinical decision-making/therapy

It is a well-known that while the CT images most often reveal the pathology – atelectasis, consolidation, nodules, pleural fluid – it may not be able to categorically report on the cause of the above findings. Thus, CT scan is an important added tool which the transplant physician uses in corroboration with other diagnostic modalities. While the ability to differentiate between infection and rejection is not absolute, MDCT patterns provide data which might favor one or the other as the diagnosis.

However, MDCT is the modality of choice to diagnosis pulmonary thrombo-embolism. It is always indicated before intervention especially with relation to airway complications such as planning for balloon dilatation, stenting, and treating dehiscence. It is also quite valuable in assessment and follow-up of residual pleural space in case of prolonged air-leak, which may not be possible with just a two-dimensional chest X ray.

Multidetector computed tomography imaging findings

Pleural effusion [Figure 4] was the most common finding being seen in 18 scans, out of which two effusions required tube drainage or aspiration as they were symptomatic or were persistent. The next common finding was the presence of ground-glass opacities (GGO) or consolidation which was unilateral or bilateral in 16 studies.
Figure 4: Noncontrast multidetector computed tomography coronal reformatted images show thick rind of pleural fluid (star) on left side with thickening causing mild volume loss in left hemithorax. Left drain tube in situ.

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Atelectasis (segmental or plate like) was seen frequently and was a nonspecific finding in many scans. None of them were significant requiring intervention. We did not encounter lobar or lung collapse. Similarly, diffuse mild degree of cylindrical bronchiectasis was seen in few scans (4) and was not clinically significant.

Bronchial complications were the next most common finding occurring in six scans, although three of these scans were for the same patient who showed an initial bronchial plug followed by stenosis and repeat imaging posttreatment which showed improvement in the stenosis follow bronchoscopy. Another patient had two scans earlier, one showing anastomotic site granulations followed by progressive bronchostenosis in the second scan.

Smooth septal thickening and centrilobular nodules were other frequent findings, seen in four and three scans each. Centrilobular nodules were seen in two patients, one with infection and another with chronic allograft dysfunction in repeated scans due to bronchiolitis.

Other less frequent imaging findings were hemothorax, hydropneumothorax, pneumothorax, segmental pulmonary embolism, hemomediastinum, pneumomediastinum, etc., Mosaic attenuation was seen in three scans of a single patient of chronic graft dysfunction.

Two patients did not have any positive imaging findings on CT scan, one of whom was proven to have HINI infection. Atelectasis, small GGO, and effusions were the common findings prevalent at all time frames and having no clinical significance. Many of the studies had overlap of findings frequently, for example, pleural effusion, GGO, and septal thickening. The list of imaging findings according to the frequency is listed in [Table 3].
Table 3: Summary of multidetector computed tomography imaging findings

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Complications in temporal sequence

Early postoperative period (0–7 days)

Three patients had complications in this period (9% of scans). Hemothorax and pneumothorax was seen in one patient each and one patient had hemothorax and hemomediastinum [Figure 5] which resolved on conservative management. The other patient with hemothorax [Figure 6] had a history of silicosis due to which the surgery technique was difficult. He succumbed to bleeding diathesis and MODS. The pneumothorax was bilateral in a patient with Kartageners syndrome which also resolved [Figure 7]. Early complications are summarized in [Table 4].
Figure 5: Axial noncontrast multidetector computed tomography images of double lung transplant showing oval hyperdense lesion in the mediastinum (white arrow head) just above the level of left atrium in keeping with postoperative hematoma. Associated moderate left pleural effusion (black arrow).

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Figure 6: Axial noncontrast multidetector computed tomography images of the chest showing bilateral large hyperdense pleural collections in keeping with hemothorax (white arrow) with drain tube on both sides.

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Figure 7: Coronal noncontrast multidetector computed tomography images in lung window shows bilateral pneumothoraces (asterix) with drain tubes in situ.

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Table 4: List of early postoperative complications

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Intermediate postoperative period (1 week–2 months)

Thirteen scans showed complications in this period (40%).

Four patients had developed lung infection. One patient had CT features of aspiration pneumonitis [Figure 8] from which Klebsiella was isolated as a pathogen on bronchial wash. One patient had fungal infection to which he succumbed later. Acute rejection [Figure 9]a and [Figure 9]b was seen in three patients of which two were due to acute T-cell mediation and one was both T-cell and antibody mediated. One patient had a combination of rejection and infection. Two patients had bronchial dehiscence which presented as loculated hydropneumothorax [Figure 10] and one as bronchial narrowing. Bronchial stenosis was seen in one patient seen as narrowing. Bronchial exuberant granulation causing 30% luminal stenosis was seen in one patient on bronchoscopy which was missed on MDCT [Figure 11]. Five patients had MDCT identifiable bronchial complications during this period. One patient had subsegmental pulmonary thromboembolism [Figure 12]a and [Figure 12]b. The complications that we encountered in this period are listed in [Table 5].
Figure 8: Axial noncontrast multidetector computed tomography images of single lung transplant shows multiple centrilobular nodules (curved arrow) in the right lower lobe due to aspiration pneumonia. Klebsiella was grown on aspirate from trachea. Straight arrow shows native interstitial fibrosis.

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Figure 9: Coronal reformatted (a) and axial (b) noncontrast multidetector computed tomography images of double lung transplant show patchy ground glass opacities (white circle) and septal thickening (white arrowhead) diffusely in both lungs in keeping with acute T cell mediated rejection.

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Figure 10: Axial noncontrast multidetector computed tomography images of the lung apex in mediastinal (a) and lung windows (b) shows a horizontal air fluid level (small black arrow) in the left apex suggestive of loculated hydropneumothorax.

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Figure 11: Axial noncontrast multidetector computed tomography images of double lung transplant show irregular polypoid intrabronchial nodular lesion in the right main bronchus in keeping with bronchial granulations (black arrow) with mild bilateral pleural effusion (white arrow).

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Figure 12: (a) Axial contrast MDCT image of a SLT showing right pleural effusion (black arrow) and (b) coronal MDCT image of a SLTshowing a filling defect ina subsegmental branch of right lower lobe pulmonary artery(grey arrow) suggestive of acute pulmonary thromboembolism.

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Table 5: List of complications in the intermediate postoperative period

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Late postoperative period (2 months and greater)

Six patients presented during this period (51.5% of scans). Three patients had infection. One patient had chronic allograft dysfunction with bronchiolitis obliterans [Figure 13]a and [Figure 13]b and the same patient later developed an episode of acute on chronic rejection. One patient with Kartageners syndrome had recurrence of bronchostenosis involving the left main bronchus [Figure 14]. These findings are summarized in [Table 6].
Figure 13: Axial noncontrast MCDT images of bronchiolitis obliterans syndrome with (a) and without expiration (b) showing areas of air trapping (plus symbol), ground glass opacities, mild bronchiectasis (black arrow) and centrilobular nodules (white arrow).

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Figure 14: Axial noncontrast coronal reformatted multidetector computed tomography images in mini MIP projection of double lung transplant shows marked long segment stenosis of the left lower lobe bronchus with proximal dilatation (black arrow).

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Table 6: List of late postoperative period complications

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The overall diagnostic accuracy of MDCT was 85%. Sensitivity is 96%, specificity is 33.3%, positive predictive value is 86%, and negative predictive value is 66.7%.


  Discussion Top


Studies have shown that the spectrum of postoperative complications is dependent on a time spectrum[9] and is as follows:

*EARLY POSTOPERATIVE PERIOD (0–7 DAYS) and < 24 h is immediate complications

*INTERMEDIATE POST OPERATIVE PERIOD (1 week-2 months)

*LATE POSTOPERATIVE PERIOD (2 months and greater) and <4 months is primary late and more than 4 months is secondary late.

However, this division is not strict and there is often overlap of the conditions, although some are specific to the time frames. This time continuum is especially important as it gives a guide as to what complications are likely and helps the radiologist narrow the differentials.

Early and intermediate postoperative complications

Most of our scans were done in the intermediate and late postoperative period with few scans in the early postoperative period. This is because in the early postoperative period the issues commonly faced are effusion, atelectasis, and pneumothorax which can be diagnosed fairly early and easily on chest radiographs.

Primary graft dysfunction

PGD is a condition where the graft fails to function properly from the time of anastomosis until 72 h postoperative and is believed to be due to ischemic reperfusion injury or reimplantation response by the body to the lung. When all other secondary causes of hypoxia were ruled out, two of our cases had a history of significant Grade 3 PGD for which MDCT imaging was not done. The incidence of Stage 3 PGD is between 10% and 25% with a 30-day mortality of approximately 50%[10] and they are more prone for developing other complications. One of these patients died in 2 months due to fulminant aspergillosis and the other patient developed bronchostenosis.

Infection

Most complications encountered in our study were in the intermediate postoperative period with lung infection being most common. The incidence in the literature is nearly 75% including bacterial, viral, and fungal infections.[11] During the immediate postoperative period, high doses of immunosuppressive drugs are used intravenously as induction therapy to prevent rejection. Routine surgical antibiotic prophylaxis is used, and subsequent antibiotic therapy is guided by culture results from the donor tissue. Later, intravenous immunosuppressants are changed to oral maintenance therapy to prevent rejection. Hence, in this phase, patients are susceptible to different opportunistic infections. Lung infections presented in our study as GGO or consolidation in four scans (unilateral or bilateral and unifocal or multifocal). These could be associated with small effusion. Another pattern was the presence of centrilobular nodules seen in one patient. Two patients presented purely with focal interstitial oedema which was misdiagnosed on CT as a feature of rejection. This must be kept in mind by the radiologist. We have observed in our patients, the challenge was in managing infection more than rejection. These patterns agree with those described in literature.

Rejection

Acute rejection incidence was similar to the incidence of infection in our study, while it is quoted as 29% by Roden et al.[12] However, it is similar in other Asian countries like Korea where infection is more of concern generally and tuberculosis is endemic.[13] Acute rejection presented in our study most frequently with focal GGO or consolidation in two patients, septal thickening and bilateral perihilar consolidation in one patient each. The focal form without septal thickening most often mimics infection.

Airway complications

Airway complications which occur due to ischemia and infection, involve the anastomosis and distal airway beyond the anastomosis. They are reported to occur in 10%–15% of patients.[14] Bronchial complications, although occasional, are the important cause for significant morbidity and they may need intervention. Bronchial stenosis, dehiscence-partial or complete, bronchomalacia, excessive granulation, and diverticula are the bronchial abnormalities which occur and they may need intervention. We encountered all except complete dehiscence and diverticulae.

Bronchial anastomotic complications are initially assessed by fiber optic bronchoscopy. Mucosal ischemia with very minimal dehiscence may not show up on MDCT imaging. Only when the degree of dehiscence progresses, pockets of air surrounding the anastomosis are evident on imaging. Larger degrees or complete breakdown of anastomosis reveal large air pockets with discontinuous bronchial wall often communicating with the pleural space.[9] Furthermore, CT is limited in that it cannot identify the site of dehiscence for which bronchoscopy is excellent. Careful examination of the bronchial wall is needed to look for small irregularities and plugs which may represent granulations leading to stenosis later as illustrated by the case overlooked by MDCT in our study.

Bronchial dehiscence presented as persistent air leak in 1 patient and needed bronchoscopic deployment of self-expanding metallic stents which were subsequently removed successfully. Two patients had anastomotic stenosis. They had to be treated with bronchoscopic balloon dilatation. One of them has recurrence in late postoperative period requiring cryotherapy, mitomycin injections and balloon dilatation to which he eventually responded. This patient had a DLT for end-stage bronchiectasis due to Kartagener's syndrome with situs inversus totalis with surgical challenges due to reversed anatomy. MDCT reconstructions were able to identify and depict the stenosis exquisitely and guide intervention. Stenosis should not be confused with telescoping which is due to surgical technique employed when there is a significant size mismatch between the donor and recipient bronchi. Stenosis can develop due to technically difficult anastomosis, anatomical variations or ischemic changes. Infection also predisposes to granulations and scarring leading to stenosis. Dynamic scans may be of use to evaluate fixed narrowing vs bronchomalacia.

Pulmonary thromboembolism

Pulmonary embolism was seen in one patient and was at the subsegmental level. Although in a clinically stable patient, the clinical significance is questionable, in a post-SLT patient with one diseased lung it may assume importance. The incidence of clinically suspected pulmonary embolism is said to be 6%.[15] In our study, most of our cases have not been done with IV contrast.

Late complications

Late complications were encountered in five of our cases with one rejection, one recurrent bronchostenosis, three infections.

Chronic rejection

Chronic rejection is said to occur in at least 50% of patients within 5 years posttransplantation.[9] We had only on patient who had been followed for more than 3 years and presented with BOS due to chronic rejection. BOS is characterized by bronchiectasis, air trapping, and centrilobular nodules, of which air trapping is said to be more sensitive. It must be noted that mild degree of bronchiectasis is of no clinical significance and is usually seen in many patients. This patient also had an episode of acute on chronic rejection which presented as focal increasing consolidation mimicking infection.

Pleuroparenchymal fibrosis, recurrence of primary disease in the graft, and lymphoproliferative disorders are the recognized long-term complications. However, we did not face these complications as our follow-up period is less.

One patient had tubercular infection which was diagnosed by exclusion and complete clinical response to empirical antituberculous therapy. We mention this to highlight the fact that endemic nature of TB needs to be kept in mind when evaluating possible causes of infection. Furthermore, this population is susceptible to epidemics like the rest of the general population as highlighted by one of our cases with normal MDCT who had acquired HINI infection.

In our study, bronchial complications such as stenosis could be easily identified through careful search for early granulations has to be made. Acute rejection most often presented with desaturation, hypoxia, and a combination of infection and rejection was common presentation on imaging with GGO, septal thickening, and effusion. Infection and rejection could mimic each other in the imaging findings and pattern of distribution. Viral pneumonias can very often present with bilateral changes and septal thickening. Chronic rejection showed findings of BOS.

This shows that the findings of acute rejection and infection overlap, and timing and clinical presentation is crucial for the diagnosis along with BAL and biopsy. If positive sputum or BAL and raised Procalcitonin (PCT) were present, then infection was more likely. Our study again illustrates that in our population infection could be more frequent than rejection.

Finally, the status of the native lung in SLT is very important to assess in MDCT for primary disease progression which could lead to complications affecting the transplant like mass effect due to hyperinflation of native lung [Figure 15], infections in the native lung or development of a pneumothorax.
Figure 15: Axial noncontrast multidetector computed tomography images of single lung transplant show marked narrowing of the right main bronchus with distal tapering (black arrow) and collapse of the right lung. The native lung is hyperinflated and emphysematous (white arrow).

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  Conclusions Top


Although regular immediate and long-term follow-up is by chest radiographs in lung transplant patients, MDCT is the initial noninvasive imaging modality of choice for the evaluation of radiographic abnormalities and a problem-solving tool. Protocols must be tailored according to the need and clinical question. Radiologists need to be familiar with the imaging appearances and issues related to LT, especially in the current pandemic as LT is offered as the treatment to irreparable residual lung damage after COVID-19 pneumonia.

MDCT imaging and clinical diagnosis concordance is high. The remarkably high sensitivity of CT scan is helpful provided the temporal sequence of complications is understood and applied in conjunction with other tests to improve the specificity.

MDCT is extremely useful and unambiguous in identifying airway complications and is useful for planning interventions and in follow-up. Air leaks and granulations should be followed up for long-term complications. Chronic rejection is identified fairly accurately by MDCT as BOS characterized by air trapping.

MDCT is limited in evaluating lung parenchymal changes as there is overlap of imaging features of acute rejection and infection. Correlation with bronchoscopy/BAL and biopsy is required in such situations although the presence of nodules and asymmetric involvement favor infection. Unlike Western world, infection including tuberculosis is more frequently encountered than rejection.

The limitations include a small number of patients in the study. Hence, statistical inferences on survival may not be as robust as when calculated for a larger number of patients. Furthermore, in view of small numbers, statistical analysis of images and clinical correlation could not be done. Furthermore, there is a broad range of conditions involved over a long-time continuum. Hence, larger studies over a longer period are required to validate these findings. Plain radiographs which are the main stay in the immediate and initial evaluation were not included. Correlation with radiographs may give additional important information regarding the development of complications in each patient over a time frame, when there are overlapping MDCT imaging features.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12], [Figure 13], [Figure 14], [Figure 15]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]



 

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