Pulmonary Complications of Transplantation: Radiographic Considerations

Gut Microbiota Predict Pulmonary Infiltrates after Allogeneic Hematopoietic Cell Transplantation

RATIONALE

Pulmonary complications (PCs) cause significant morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HCT). Shifts in gut microbiota have been linked to HCT outcomes; however, their effect on PCs is unknown.

OBJECTIVES

To investigate whether changes in gut microbiota are associated with PCs after HCT.

METHODS

A single-center observational study was performed on 94 patients who underwent HCT from 2009 to 2011 and who were previously enrolled in a protocol for 16S ribosomal RNA sequencing of fecal microbiota. The primary endpoint, PC, was defined by new abnormal parenchymal findings on chest imaging in the setting of respiratory signs and/or symptoms. Outcomes were collected up to 40 months after transplant. Clinical and microbiota risk factors for PCs and mortality were evaluated using survival analysis.

MEASUREMENTS AND MAIN RESULTS

One hundred twelve PCs occurred in 66 (70.2%) subjects. A high comorbidity index (hazard ratio [HR], 2.30; 95% confidence interval [CI], 1.30-4.00; P = 0.004), fluoroquinolones (HR, 2.29, 95% CI, 1.32-3.98; P = 0.003), low baseline diversity (HR, 2.63; 95% CI, 1.22-5.32; P = 0.015), and γ-proteobacteria domination of fecal microbiota (HR, 2.64; 95% CI, 1.10-5.65; P = 0.031), which included common respiratory pathogens, predicted PCs. In separate analyses, low baseline diversity was associated with PCs that occurred preengraftment (HR, 6.30; 95% CI, 1.42-31.80; P = 0.016), whereas γ-proteobacteria domination predicted PCs postengraftment (HR, 3.68; 95% CI, 1.49-8.21; P = 0.006) and overall mortality (HR, 3.52; 95% CI, 1.28-9.21; P = 0.016). Postengraftment PCs were also independent predictors of death (HR, 2.50; 95% CI, 1.25-5.22; P = 0.009).

CONCLUSIONS

This is the first study to demonstrate prospective changes in gut microbiota associated with PCs after HCT. Postengraftment PCs and γ-proteobacteria domination were predictive of mortality. This suggests an adverse relationship between the graft and lung, which is perhaps mediated by bacterial composition in the gut. Further study is warranted.

High-resolution CT can differentiate between alloimmune and nonalloimmune lung disease early after hematopoietic cell transplantation

OBJECTIVE

The purpose of this study was to develop a simple semiquantitative high-resolution CT (HRCT) scoring system to differentiate alloimmune-mediated lung syndromes (allo-LS) from other lung diseases early after hematopoietic cell transplantation. Allo-LS should be differentiated from other abnormalities, such as infections and toxicity, because they are life threatening and require prompt and specific treatment.

MATERIALS AND METHODS

In 52 pediatric hematopoietic cell transplant recipients with early symptoms of pulmonary disease, a clinical diagnosis was made by an expert physician. HRCT studies were scored by two independent radiologists for various airway and parenchyma abnormalities. HRCT scores were compared with the final clinical diagnoses.

RESULTS

Patients with allo-LS had significantly higher HRCT severity scores for ground-glass pattern and airtrapping compared with patients with nonalloimmune disease. A combined score was constructed (the "allo-score") that appeared to have good predictive capacity for clinical allo-LS (AUC = 0.82). HRCT scoring was reproducible for all items except airway wall thickening and septal thickening.

CONCLUSION

A simple HRCT severity score can be helpful to differentiate allo-LS from other pulmonary complications early after hematopoietic cell transplantation.

Diagnostic bronchoscopy in solid-organ and hematopoietic stem cell transplantation

Fiberoptic bronchoscopy is a valuable diagnostic tool in solid-organ and hematopoietic stem cell transplant recipients presenting with a range of pulmonary complications. This article provides a comprehensive overview of the utility and potential adverse effects of diagnostic bronchoscopy for transplant recipients. Recommendations are offered on the selection of patients, the timing of bronchoscopy, and the samples to be obtained across the spectrum of suspected pulmonary complications of transplantation. Based on review of the literature, the authors recommend early diagnostic bronchoscopy over empiric treatment in transplant recipients with evidence of certain acute, subacute, or chronic pulmonary processes. This approach may be most critical when an underlying infectious etiology is suspected. In the absence of prompt diagnostic information on which to base effective treatment, the risks associated with empiric antimicrobial therapy, including medication side effects and the development of antibiotic resistance, compound the potential harm of delaying targeted management.

Does high-resolution CT has diagnostic value in patients presenting with respiratory symptoms after hematopoietic stem cell transplantation?

BACKGROUND

Hematopoietic stem cell transplantation (SCT) can be complicated by a variety of live-threatening infectious and non-infectious pulmonary complications. The management of these complications is critically dependent on the most probable diagnosis, which is in part based on imaging work-up.

METHODS

Systematic review of the literature related to the diagnostic value of high-resolution computed tomography (HRCT) in patients who underwent SCT and developed respiratory symptoms.

RESULTS

Literature review did not reveal systematic cohort studies that included patients with respiratory symptoms post-SCT who underwent HRCT and had a well-defined outcome. Most studies selected participants based on their final diagnosis instead of the indication for diagnostic testing in practice. Nevertheless, several papers clearly indicated a potential role for HRCT when complications after SCT occur. A variety of articles described the role of certain HRCT findings in the diagnosis of specific infectious complications, but less data were available for non-infectious complications.

CONCLUSION

We believe more diagnostic studies are needed to determine the value of HRCT for a specific diagnosis in SCT-recipients who present with respiratory symptoms at the transplant clinic. Currently, radiologists should be cautious since HRCT interpretation in these patients is not unambiguous.

Postoperative infectious complications of abdominal solid organ transplantation

There is a rapidly growing population of immunocompromised organ transplant recipients. These patients are at risk of a large variety of infections that have significant consequences on mortality, graft dysfunction, and graft loss. The diagnosis and treatment of these infections are facilitated by an understanding of the preoperative, perioperative, and postoperative risk factors; the typical pathogens; and their characteristic time of presentation. On the basis of these factors, we put forth an algorithm for diagnosing and treating suspected infections in solid organ transplant recipients.

Pulmonary nocardiosis after lung transplantation: CT findings in 7 patients and review of the literature

OBJECTIVE

The purpose of this study is to review reported radiographic clues to the diagnosis of pulmonary nocardiosis, as well as to describe and illustrate the high-resolution computed tomography findings of 7 patients with pulmonary nocardiosis after lung transplantation.

CONCLUSIONS

Computed tomography findings of pulmonary nocardiosis after lung transplantation consist predominantly of nodules and cavitary lesions without any significant zonal or anatomic distribution. The diagnosis of pulmonary nocardiosis requires a high index of suspicion, as presenting symptoms are nonspecific, initial visualization is often not possible with routine stains, and identification requires prolonged cultures.