Pleural exudates and transudates: diagnosis with contrast-enhanced CT

Pictorial Review of Pleural Disease: Multimodality Imaging and Differential Diagnosis

The pleura is a thin, smooth, soft-tissue structure that lines the pleural cavity and separates the lungs from the chest wall, consisting of the visceral and parietal pleurae and physiologic pleural fluid. There is a broad spectrum of normal variations and abnormalities in the pleura, including pneumothorax, pleural effusion, and pleural thickening. Pneumothorax is associated with pulmonary diseases and is caused by iatrogenic or traumatic factors. Chest radiography and US help detect pneumothorax with various signs, and CT can also help assess the causes. Pleural effusion occurs in a wide spectrum of diseases, such as heart failure, cirrhosis, asbestos-related diseases, infections, chylothorax, and malignancies. Chest US allows detection of a small pleural effusion and evaluation of echogenicity or septa in pleural effusion. Pleural thickening may manifest as unilateral or bilateral and as focal, multifocal, or diffuse. Various diseases can demonstrate pleural thickening, such as asbestos-related diseases, neoplasms, and systemic diseases. CT, MRI, and fluorodeoxyglucose (FDG) PET/CT can help differentiate between benign and malignant lesions. Knowledge of these features can aid radiologists in suggesting diagnoses and recommending further examinations with other imaging modalities. The authors provide a comprehensive review of the clinical and multimodality imaging findings of pleural diseases and their differential diagnoses. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

Diagnostic accuracy of thoracic CT to differentiate transudative from exudative pleural effusion prior to thoracentesis

BACKGROUND

Computed tomography (CT) scan is commonly performed for pleural effusion diagnostis in the clinic. However, there are limited data assessing the accuracy of thoracic CT for the separation of transudative from exudative effusions. The study aimed to determine the diagnostic value of thoracic CT in distinguishing transudates from exudates in patients with pleural effusion.

METHODS

This is a two-center retrospective analysis of patients with pleural effusion, a total of 209 patients were included from The First Affiliated Hospital of Henan University of Science and Technology as the derivation cohort (Luoyang cohort), and 195 patients from the First Affiliated Hospital of Zhengzhou University as the validation cohort (Zhengzhou cohort). Patients who underwent thoracic CT scan followed by diagnostic thoracentesis were enrolled. The optimal cut-points of CT value in pleural fluid (PF) and PF to blood CT value ratio for predicting a transudative vs. exudative pleural effusions were determined in the derivation cohort and further verified in the validation cohort.

RESULTS

In the Derivation (Luoyang) cohort, patients with exudates had significantly higher CT value [13.01 (10.01-16.11) vs. 4.89 (2.31-9.83) HU] and PF to blood CT value ratio [0.37 (0.27-0.53) vs. 0.16 (0.07-0.26)] than those with transudates. With a cut-off value of 10.81 HU, the area under the curve (AUC), sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of CT value were 0.85, 88.89%, 68.90%, 43.96%, and 95.76%, respectively. The optimum cut-value for PF to blood CT value ratio was 0.27 with AUC of 0.86, yielding a sensitivity of 61.11%, specificity of 86.36%, PPV of 78.57%, and NPV of 73.08%. These were further verified in the Validation (Zhengzhou) cohort.

CONCLUSIONS

CT value and PF to blood CT value ratio showed good differential abilities in predicting transudates from exudates, which may help to avoid unnecessary thoracentesis.

Impact of photon counting detector CT derived virtual monoenergetic images and iodine maps on the diagnosis of pleural empyema

PURPOSE

The purpose of this study was to evaluate the impact of virtual monoenergetic image (VMI) energies and iodine maps on the diagnosis of pleural empyema with photon counting detector computed tomography (PCD-CT).

MATERIALS AND METHODS

In this IRB-approved retrospective study, consecutive patients with non-infectious pleural effusion or histopathology-proven empyema were included. PCD-CT examinations were performed on a dual-source PCD-CT in the multi-energy (QuantumPlus) mode at 120 kV with weight-adjusted intravenous contrast-agent. VMIs from 40-70 keV obtained in 10 keV intervals and an iodine map was reconstructed for each scan. CT attenuation was measured in the aorta, the pleura and the peripleural fat (between autochthonous dorsal muscles and dorsal ribs). Contrast-to-noise (CNR) and signal-to-noise (SNR) ratios were calculated. Two blinded radiologists evaluated if empyema was present (yes/no), and rated diagnostic confidence (1 to 4; not confident to fully confident, respectively) with and without using the iodine map. Sensitivity, specificity and diagnostic confidence were estimated. Interobserver agreement was estimated using an unweighted Cohen kappa test. A one-way ANOVA was used to compare variables. Differences in sensitivity and specificity between the different levels of energy were searched using McNemar test.

RESULTS

Sixty patients (median age, 60 years; 26 women) were included. A strong negative correlation was found between image noise and VMI energies (r = -0.98; P = 0.001) and CNR increased with lower VMI energies (r = -0.98; P = 0.002). Diagnostic accuracy (96%; 95% CI: 82-100) as well as diagnostic confidence (3.4 ± 0.75 [SD]) were highest at 40 keV. Diagnostic accuracy and confidence at higher VMI energies improved with the addition of iodine maps (P ≤0.001). Overall, no difference in CT attenuation of peripleural fat between patients with empyema and those with pleural effusion was found (P = 0.07).

CONCLUSION

Low VMI energies lead to a higher diagnostic accuracy and diagnostic confidence in the diagnosis of pleural empyema. Iodine maps help in diagnosing empyema only at high VMI energies.

Hemithorax white-out due to massive pleural effusion

This is a clinical image submission depicting hemithorax white-out due to massive pleural effusion.

Automated Detection, Segmentation, and Classification of Pleural Effusion From Computed Tomography Scans Using Machine Learning

OBJECTIVE

This study trained and evaluated algorithms to detect, segment, and classify simple and complex pleural effusions on computed tomography (CT) scans.

MATERIALS AND METHODS

For detection and segmentation, we randomly selected 160 chest CT scans out of all consecutive patients (January 2016-January 2021, n = 2659) with reported pleural effusion. Effusions were manually segmented and a negative cohort of chest CTs from 160 patients without effusions was added. A deep convolutional neural network (nnU-Net) was trained and cross-validated (n = 224; 70%) for segmentation and tested on a separate subset (n = 96; 30%) with the same distribution of reported pleural complexity features as in the training cohort (eg, hyperdense fluid, gas, pleural thickening and loculation). On a separate consecutive cohort with a high prevalence of pleural complexity features (n = 335), a random forest model was implemented for classification of segmented effusions with Hounsfield unit thresholds, density distribution, and radiomics-based features as input. As performance measures, sensitivity, specificity, and area under the curves (AUCs) for detection/classifier evaluation (per-case level) and Dice coefficient and volume analysis for the segmentation task were used.

RESULTS

Sensitivity and specificity for detection of effusion were excellent at 0.99 and 0.98, respectively (n = 96; AUC, 0.996, test data). Segmentation was robust (median Dice, 0.89; median absolute volume difference, 13 mL), irrespective of size, complexity, or contrast phase. The sensitivity, specificity, and AUC for classification in simple versus complex effusions were 0.67, 0.75, and 0.77, respectively.

CONCLUSION

Using a dataset with different degrees of complexity, a robust model was developed for the detection, segmentation, and classification of effusion subtypes. The algorithms are openly available at https://github.com/usb-radiology/pleuraleffusion.git.

Considerations on Baseline Generation for Imaging AI Studies Illustrated on the CT-Based Prediction of Empyema and Outcome Assessment

For AI-based classification tasks in computed tomography (CT), a reference standard for evaluating the clinical diagnostic accuracy of individual classes is essential. To enable the implementation of an AI tool in clinical practice, the raw data should be drawn from clinical routine data using state-of-the-art scanners, evaluated in a blinded manner and verified with a reference test. Three hundred and thirty-five consecutive CTs, performed between 1 January 2016 and 1 January 2021 with reported pleural effusion and pathology reports from thoracocentesis or biopsy within 7 days of the CT were retrospectively included. Two radiologists (4 and 10 PGY) blindly assessed the chest CTs for pleural CT features. If needed, consensus was achieved using an experienced radiologist’s opinion (29 PGY). In addition, diagnoses were extracted from written radiological reports. We analyzed these findings for a possible correlation with the following patient outcomes: mortality and median hospital stay. For AI prediction, we used an approach consisting of nnU-Net segmentation, PyRadiomics features and a random forest model. Specificity and sensitivity for CT-based detection of empyema (n = 81 of n = 335 patients) were 90.94 (95%-CI: 86.55–94.05) and 72.84 (95%-CI: 61.63–81.85%) in all effusions, with moderate to almost perfect interrater agreement for all pleural findings associated with empyema (Cohen’s kappa = 0.41–0.82). Highest accuracies were found for pleural enhancement or thickening with 87.02% and 81.49%, respectively. For empyema prediction, AI achieved a specificity and sensitivity of 74.41% (95% CI: 68.50–79.57) and 77.78% (95% CI: 66.91–85.96), respectively. Empyema was associated with a longer hospital stay (median = 20 versus 14 days), and findings consistent with pleural carcinomatosis impacted mortality.

Diagnostic Accuracy of Imaging Findings in Pleural Empyema: Systematic Review and Meta-Analysis

Computed tomography (CT) diagnosis of empyema is challenging because current literature features multiple overlapping pleural findings. We aimed to identify informative findings for structured reporting. The screening according to inclusion criteria (P: Pleural empyema, I: CT C: culture/gram-stain/pathology/pus, O: Diagnostic accuracy measures), data extraction, and risk of bias assessment of studies published between 01-1980 and 10-2021 on Pubmed, Embase, and Web of Science (WOS) were performed independently by two reviewers. CT findings with pooled diagnostic odds ratios (DOR) with 95% confidence intervals, not including 1, were considered as informative. Summary estimates of diagnostic accuracy for CT findings were calculated by using a bivariate random-effects model and heterogeneity sources were evaluated. Ten studies with a total of 252 patients with and 846 without empyema were included. From 119 overlapping descriptors, five informative CT findings were identified: Pleural enhancement, thickening, loculation, fat thickening, and fat stranding with an AUC of 0.80 (hierarchical summary receiver operating characteristic, HSROC). Potential sources of heterogeneity were different thresholds, empyema prevalence, and study year.

Role of Chest Computed Tomography in Patients Hospitalized with Community-Acquired Complicated Parapneumonic Effusion or Empyema: Role of CT in Parapneumonic Effusion

BACKGROUND

Data regarding predictors of the outcome in patients with community-acquired complicated parapneumonic effusion (CPPE) or empyema are insufficient. The aim of the present study was to investigate the prognostic factors in these patients.

METHODS

Patients with community-acquired pneumonia (CAP) were classified into a CPPE or empyema group and a control group. The patients with CPPE or empyema were further divided into longer and shorter length of stay (LOS) groups, and clinical variables and computed tomographic (CT) findings were compared between the 2 groups.

RESULTS

Of outcome variables, LOS was significantly longer in the CPPE or empyema group than in the control group (13 days [interquartile range, 10‒17 days] versus 8 days [6‒12 days], p < 0.001), whereas 30-day mortality and in-hospital mortality were not significantly different between the 2 groups. Patients with CPPE or empyema were divided into shorter LOS (<14 days) and longer LOS (≥14 days) groups. Pneumonia severity index (PSI) class IV‒V (odds ratio [OR], 2.79; 95% confidence interval [CI]: 1.35, 5.76; p = 0.006), increased attenuation of extrapleural fat (OR, 2.26; 95% CI: 1.06, 4.80; p = 0.034), and pleural microbubbles (OR 3.93; 95% CI: 1.03, 14.98; p = 0.045) were independent predictors for prolonged LOS in CAP patients with CPPE or empyema.

CONCLUSIONS

Increased attenuation of extrapleural fat and pleural microbubbles assessed with CT and PSI class IV‒V independently predicted prolonged LOS in CAP patients with CPPE or empyema. These findings may be helpful to identify patients who need more intensive evaluation and intervention.

Value of spectral detector computed tomography to differentiate infected from noninfected thoracoabominal fluid collections

PURPOSE

To investigate the diagnostic value of spectral detector CT (SDCT)-derived virtual non-contrast (VNC), virtual monoenergetic images (VMI) and iodine overlays (IO) for distinguishing infected from noninfected fluid collections (FC) in the chest or abdomen.

METHOD

This retrospective study included 58 patients with venous phase SDCT with 77 FC. For all included FC, microbiological analysis of aspirated fluid served as reference. For quantitative analysis, wall thickness was measured, and (ROI)-based analysis performed within the fluid, the FC's wall (if any) and the aorta. Two radiologists qualitatively evaluated visibility of wall enhancement, diagnostic confidence regarding infection of fluid collection, confidence of CT-guided drainage catheter placement and visibility of anatomical landmarks in conventional images (CI) and VNC, VMI_40keV, IO.

RESULTS

Wall thickness significantly differed between infected (n = 46) and noninfected (n = 31) FC (3.5 ± 1.8 mm vs. 1.4 ± 1.8 mm, AUC = 0.81; p < 0.05). Fluid attenuation and wall enhancement was significantly higher in infected as compared to noninfected FC in all reconstructions (p < 0.05, respectively). Highest AUC regarding A) attenuation in fluid was yielded in CI and VMI_70,80keV (0.75); B) wall enhancement in CI (0.88) followed by iodine concentration (0.86). Contrast-to-noise ratio of wall vs. fluid was highest in VMI_40keV (p < 0.05). All assessed qualitative parameters received significantly higher ratings when using spectral reconstructions vs. CI (p for all <0.05), except for visibility of wall enhancement.

CONCLUSION

Spectral reconstructions improve the assessment of infected from noninfected thoracoabdominal fluid collections and depiction of wall enhancement. Diagnostic performance of the quantitative measurements in spectral reconstructions were comparable with measurements in conventional images.

Efficacy of Ultrasonography in the Diagnosis of Transudative Pleural Fluids

AIMS

We aimed to evaluate the efficacy of thoracic ultrasonography (USG) in diagnosis of pleural exudates and transudates using pleural thickness (PT) measurement.

PATIENTS AND METHODS

Patients who underwent investigations for pleural fluid between January 2018 and May 2018 were included in this prospective study. The patients were evaluated using radiologic imaging modalities to detect pleural fluid, and PT was measured using thoracic USG. The patients were then divided into 2 groups according to Light's criteria as transudative pleural fluid (TPF) and exudative pleural fluid (EPF), and the results were compared between the groups.

RESULTS

A total of 73 patients were included in the study. The mean age was 62±15.1 years. Forty-eight patients (65.8%) had EPF and 25 (34.2%) had TPF. Thoracic USG revealed a mean PT of 0.3±0.1 cm in the TPF group and 0.6±0.3 cm in the EPF group (P<0.001). The optimal cut-off value for PT was 0.2 cm in the TPF group. The sensitivity and specificity of thoracic USG were calculated as 87.5% and 56%, respectively.

CONCLUSION

The measurement of PT using thoracic USG in this study has a high sensitivity but low specificity for identifying transudates from exudates. This approach may be useful in patients who refuse thoracentesis or have a contraindication for the procedure, and in emergency and intensive care unit settings. We recommend further studies to determine the efficacy of thoracic USG studies in patients with pleural fluids.

A review of the management of complex para-pneumonic effusion in adults

A complex para-pneumonic effusion is a descriptive term for exudative effusions, which complicate or are likely to complicate the anatomy of the pleural space after pneumonia. We performed an online search was performed using the resources PubMed and Google Scholar to provide an update on the management of such effusions based on review of published literature. Search terms including pleural effusion (PE), parapneumonic effusion, and empyema were used. Relevant studies were identified and original articles were studied, compared and summarized. References in these articles were examined for relevance and included where appropriate. Studies involving pediatric patients were excluded. Management of para-pneumonic PE has changed tremendously over the last decade. As we accumulate more evidence in this area, approach to pleural fluid drainage is becoming more specific and guideline based. An example of a practice changing study in this aspect is the Multi-center Intrapleural Streptokinase Trial (MIST) 2 trial which demonstrated that a combination of intra-pleural tPA and DNAse improved outcomes in pleural infections compared to DNase or t-PA alone. More randomized control trials are needed to describe the role of surgical techniques like VATS (video-assisted thoracoscopic surgery) when MIST 2 protocol fails; this combination has revolutionized the management of empyema in recently.

Back to Basics - 'Must Know' Classical Signs in Thoracic Radiology

There are a few signs in radiology which are based on many common objects or patterns that we come across in our routine lives. The objective behind the association between such common objects and the corresponding pathologies is to make the reader understand and remember the disease process. These signs do not necessarily indicate a particular disease, but are usually suggestive of a group of similar pathologies which will facilitate in the narrowing down of the differential diagnosis. These signs can be seen in different imaging modalities like plain radiograph and computed tomography. In this essay, we describe 24 classical radiological signs used in chest imaging, which would be extremely helpful in routine clinical practice not only for radiologists but also for chest physicians and cardiothoracic surgeons.

Efficacy of CT in diagnosis of transudates and exudates in patients with pleural effusion

PURPOSE

We aimed to evaluate the efficacy of multidetector computed tomography (CT) imaging in diagnosis of pleural exudates and transudates using attenuation values.

MATERIALS AND METHODS

This retrospective study included 106 patients who were diagnosed with pleural effusion between January 2010 and June 2012. After the patients underwent chest CT, thoracentesis was performed in the first week. The attenuation values of the pleural effusions were measured in all patients.

RESULTS

According to Light's criteria, 30 of 106 patients with pleural effusions had transudates, and the remaining patients had exudates. The Hounsfield unit (HU) value of the exudates (median, 12.5; range, 4-33) was significantly higher than that of the transudates (median, 5; range, 2-15) (P = 0.001). Additionally, when evaluated by disease subgroups, congestive heart failure and empyema were predictable in terms of median HU values of the pleural effusions with high and moderate sensitivity and specificity values (84.6% and 81.2%, respectively; 76.9% and 66.7%, respectively). Compared with other patients, the empyema patients had significantly more loculation and pleural thickening.

CONCLUSION

CT attenuation values may be useful in differentiating exudates from transudates. Although there is an overlap in most effusions, exudate can be considered when the CT attenuation values are >15 HU. Because of overlapping HU values, close correlation with clinical findings is essential. Additional signs, such as fluid loculation and pleural thickness, should be considered and may provide further information for the differentiation.

Pleural Disorders

This chapter provides an overview of both benign and malignant pleural disorders, starting with the relevant anatomy and physiology. The focus is on the management of pneumothoraces and pleural effusions—conditions that are commonly encountered on a general thoracic surgery service. The pleural cavity is lined by parietal and visceral pleura, which are smooth membranes that are continuous with one another at the hilum and pulmonary ligaments. Parietal Pleura: innermost chest wall layer, divided into cervical, costal, mediastinal and diaphragmatic pleura.

Role of interventional pulmonology in the management of complicated parapneumonic pleural effusions and empyema

Pleural infection is a major problem that affects 80,000 cases per year in the UK and USA. It is increasing in incidence, and in an ageing population, it presents a complex challenge that requires a combination of medical therapies and may lead to the need for surgery. This article focuses on the role of the interventional pulmonologist in the diagnosis and management of pleural infection. In particular, we examine the role of pleural ultrasound in diagnostics, thoracocentesis and real-time guided procedures, and the current management strategies, including the controversial role of medical thoracoscopy.

Treatment of complicated pleural effusions in 2013

The incidence of pleural infection seems to be increasing worldwide. Despite continued advances in the management of this condition, morbidity and mortality have essentially remained static over the past decade. This article summarizes the current evidence and opinions on the epidemiology, etiology, and management of complicated pleural effusions caused by infection, including empyema. Although many parallels may be drawn between children and adults in such cases, most trials, guidelines, and series regard pediatric patient groups and those more than 18 years of age as separate entities. This review focuses mainly on the treatment of adult disease.

Multidetector CT imaging of pleura: comparison of two contrast infusion protocols

OBJECTIVES

Imaging of the pleura by multidetector CT (MDCT) can be challenging. There is no clear evidence or guidelines on contrast infusion parameters for imaging pleura. We compared two contrast protocols for assessing pleural pathology on MDCT.

METHODS

This was a prospective study in which consecutive patients with MDCT for suspected pleural disease on chest radiograph were randomised into two groups. The first group received 150 ml of intravenous contrast at a rate of 2.5 ml s(-1) and the second group received 100 ml at 2 ml s(-1). Images were acquired after a 60 s delay. Hounsfield units of the pleura, thoracic aorta, main pulmonary artery, portal vein and superior mesenteric artery were measured and analysed by two independent readers.

RESULTS

40 patients (20 in each group) who had pleural enhancement on MDCT were included for final analysis. The mean pleural enhancement value was 83 HU (Group A) vs 59 HU (Group B) (p = 0.0004). The mean aortic enhancement was 241 HU (A) vs 141 HU (B) (p<0.0001); main pulmonary artery enhancement was 208 HU (A) vs 139 HU (B) (p<0.0002); portal venous enhancement was 169 HU (A) vs 115 HU (B) (p<0.0001); and the superior mesenteric artery enhancement was 215 HU (A) vs 128 HU (B) (p<0.0001).

CONCLUSION

Enhancement of the pleura and major vessels was significantly higher in the group receiving more contrast at a greater infusion rate. This technique of a single scan through the entire pleural surface with a delayed acquisition is promising. When pleural disease is suspected, contrast infusion protocols should be modified to achieve the best results and clinicians should be encouraged to specifically request a "pleural CT".

Imaging of parapneumonic pleural effusions and empyema in children

Pleural empyema in children is increasing in incidence. The British Thoracic Society published guidelines for the management of empyema in children in 2005, including recommendations regarding imaging. In this article we review the pathophysiology, treatment options and imaging findings of complicated parapneumonic effusion and empyema in children. We also review the published evidence that supports the roles imaging is called upon to play in the management of these conditions. Imaging in the form of chest radiography and US is recommended to identify and guide drainage of complicated parapneumonic effusions. CT is recommended in special circumstances only. Imaging techniques have not been shown to accurately stage empyema, predict outcome or guide decisions regarding surgical versus medical management.

The utility of multi-detector computed tomography in the diagnosis of malignant pleural effusion in the patients with ovarian cancer

PURPOSE

The purpose of this study was to retrospectively assess possible clinical predictors of malignant pleural effusion in patients with ovarian cancer.

MATERIALS AND METHODS

This review was performed on 38 ovarian cancer patients that showed pleural effusion in a CT scan and who underwent thoracocentesis before treatment. CT scans were obtained using a 4-channel multi-detector CT scanner. Fisher's exact test was used to determine the probability of malignant pleural effusion as a function of; amount of ascites, lymph node enlargement, amount of pleural effusion, pleural nodules, and pleural thickening.

RESULTS

Sixteen (42.1%) of the 38 patients had malignant pleural effusion and malignant pleural effusion amounts were greater than those with nonmalignant effusion. Pleural nodules were more frequently found in the malignant pleural effusion group (eight [50%] patients) than in the nonmalignant group (zero [0%] patient) (p<0.001). Supradiaphragmatic lymph node enlargement (with short axis diameter 1cm or more) was more frequent in malignant group (12 [75%] patients) than in the nonmalignant group (two [9.1%] patients) (p<0.001).

CONCLUSION

The probability of malignant pleural effusion in patients with ovarian cancer was found to be correlated with the amount of pleural effusion, the presence of pleural nodules, and supradiaphragmatic lymph node enlargement.

Pleural effusion: characterization with CT attenuation values and CT appearance

OBJECTIVE

The purpose of this study was to assess the utility of CT in characterizing pleural effusions on the basis of attenuation values and CT appearance.

MATERIALS AND METHODS

We retrospectively analyzed 100 pleural effusions in patients who underwent chest CT and diagnostic thoracentesis within 48 hours of each other. On the basis of Light's criteria, effusions were classified as exudates or transudates using laboratory biochemistry markers. The mean value in Hounsfield units of an effusion was determined using a region of interest on the three slices with the greatest quantity of fluid. All CT scans also were reviewed for the presence of additional pleural features such as fluid loculation, pleural thickening, and pleural nodules.

RESULTS

Twenty-two of the 100 pleural effusions were transudates and 78 were exudates. The mean attenuation of the exudates (7.2 HU; [SD] 9.4 HU; range, 21-28 HU) was not significantly lower than the mean attenuation of the transudates (10.1 HU; 6.9 HU; range, 0.3-32 HU), (p = 0.24). None of the additional CT features accurately differentiated exudates from transudates (p > 0.1). Fluid loculation was found in 58% of exudates and in 36% of transudates. Pleural thickening was found in 59% of exudates and in 36% of transudates.

CONCLUSION

The clinical use of CT attenuation values to characterize pleural fluid is not accurate. Although fluid loculation, pleural thickness, and pleural nodules were more commonly found in patients with exudative effusions, the presence of these features does not accurately differentiate between exudates and transudates.

PET/CT in non-small cell lung cancer staging—promises and problems

Integrated positron emission tomography/computed tomography (PET/CT) has many advantages over solitary PET and CT, which has led it to become an increasingly established imaging technique in the management of many cancers. This article will review the evidence for the role of (18)F-fluorodeoxyglucose PET/CT in non-small cell lung cancer staging, examining its strengths, weaknesses and cost-effectiveness.

Thoracic empyema in patients with community-acquired pneumonia

PURPOSE

The objective of this study was to update the incidence and natural history of empyema in patients admitted to hospital with community-acquired pneumonia (CAP).

METHODS

A prospective population-based study of 3675 patients with a diagnosis of CAP was carried out. Patients were classified as "definite empyema" based on one or more of the following criteria: presence of microorganisms in pleural fluid Gram stain or culture, pleural pH less than 7.2 associated with radiographic features of empyema, or frank pus in the pleural space at the time of thoroscopy. All others were classified as either "suspected empyema" or CAP. We then compared characteristics and outcomes between subgroups.

RESULTS

A diagnosis of empyema was made in 47 patients (1.3%) by the attending physician; 24 patients (0.7%) met criteria for definite cases. Few clinical, laboratory, or radiographic features were useful in differentiating patients with definite empyema. The most commonly isolated pathogen from pleural fluid of patients with definite empyema was Streptococcus milleri group (50%). The in-hospital mortality rate for patients with definite empyema was 4.2%.

CONCLUSION

In the 21st century, empyema is an uncommon complication of CAP with an incidence of 0.7%. The S. milleri group has emerged as the most common causative microbial pathogen. The diagnosis remains difficult, although outcomes have improved from that previously reported.

Prevalence and clinical significance of pleural microbubbles in computed tomography of thoracic empyema

AIM

To determine the prevalence and clinical significance of pleural microbubbles in thoracic empyema.

MATERIALS AND METHODS

The charts of 71 consecutive patients with empyema were retrospectively reviewed for relevant demographic, laboratory, microbiological, therapeutic and outcome data. Computed tomography (CT) images were reviewed for various signs of empyema as well as pleural microbubbles. Two patient groups, with and without microbubbles were compared.

RESULTS

Mean patient age was 49 years and 72% were males. Microbubbles were detected in 58% of patients. There were no significant differences between patients with and without microbubbles in regard to pleural fluid chemistry. A causative organism was identified in about 75% of cases in both. There was no difference in the rates of pleural thickening and enhancement, increased extra-pleural fat attenuation, air-fluid levels or loculations. Microbubbles were diagnosed after a mean of 7.8 days from admission. Thoracentesis before CT was performed in 90 and 57% of patients with and without microbubbles (p=0.0015), respectively. Patients with microbubbles were more likely to require repeated drainage (65.9 versus 36.7%, p=0.015) and surgical decortication (31.7 versus 6.7%, p=0.011). Mortalities were 9.8 and 6.6% respectively (p=0.53).

CONCLUSION

Pleural microbubbles are commonly encountered in CT imaging of empyema but have not been systematically studied to date. Microbubbles may be associated with adverse outcome such as repeated drainage or surgical decortication. The sensitivity and specificity of this finding and its prognostic implications need further assessment.

The Approach to the Patient with a Parapneumonic Effusion

Parapneumonic effusion is a common clinical problem, and those that go on to develop pleural infection have high morbidity and mortality. The process of pleural infection evolution involves changes in pleural physiology that are increasingly being elucidated and understood. The microbiology of pleural infection has changed over recent years, with clear differences emerging between hospital- and community-acquired infections. Using biochemical surrogates of infection, chest drainage can be undertaken rationally for those who do not respond to antibiotics alone. Recent data suggest that fibrinolytics do not influence outcomes in pleural infection. The optimal type and timing of surgery remain controversial.

Imaging of Pleural Disease

Imaging plays an important role in the diagnosis and subsequent management of patients with pleural disease. The presence of a pleural abnormality is usually suggested following a routine chest x-ray, with a number of imaging modalities available for further characterization. This article describes the radiographic and cross-sectional appearances of pleural diseases, which are commonly encountered in every day practice. The conditions covered include benign and malignant pleural thickening, pleural effusions, empyema and pneumothoraces. The relative merits of CT, MRI and PET in the assessment of these conditions and the role of image-guided intervention are discussed.

Septal Lines in Pleural Inflammation

OBJECTIVE

The aim of the study was to evaluate the interstitial changes adjacent to pleural inflammation on multidetector computed tomography.

METHODS

The multidetector computed tomography scans of 30 patients with pleural inflammation were retrospectively and blindly evaluated by 2 observers. A control group of 7 patients with documented fibrothorax was also included. The number, appearance, thickness, and extent of septal lines were analyzed.

RESULTS

More than 10 septal lines immediately adjacent to the abnormal pleura were seen in 22 of the 30 patients with pleural inflammation and 2 of the 7 patients with fibrothorax (P<0.01). Septal lines that are more than 1 mm thick were seen in 13 of the 30 patients with acute inflammation and none of the patients with fibrothorax (P<0.01). Differences between focal and diffuse pleural inflammation included 10 cm or greater craniocaudal extent and more smooth septal lines with diffuse pleural inflammation.

CONCLUSIONS

Pleural inflammation is associated with increased number and thickening of septal lines in the immediately adjacent lung parenchyma.

[Inflammation and pleural fibrosis]

Pleural effusions are frequent. There are many etiologies of inflammatory pleural effusions and of pleural fibrosis. Imaging (standard radiography, ultrasound, scanner, MRI) is important for visualization, localization, and assessment of abundance. Exsudative (inflammatory) effusion can sometimes be distinguished from hydrothorax. Imaging signs generally remain nonspecific but can contribute to the etiological diagnosis. In particular, a CT scan of the chest, without and with contrast injection (tissue impregnation) can, in addition to the study of pleural space, enable an visual assessment of the visceral and parietal pleura, the adjacent chest wall, and the adjacent pulmonary parenchyma or vessels, which may provide diagnostic clues. Imaging can also contribute to therapeutic guidance.

Diagnosis and Management of Infectious Pleural Effusion

Pleural infection remains a common illness, with a high morbidity and mortality. The development of frank empyema from a simple exudative pleural effusion is a result of biochemical changes within the pleural space in response to bacterial invasion. These changes can be used in the diagnosis of pleural infection and used to predict which patients will require intercostal drainage for resolution of infection. Recent large trials in empyema have further advanced our knowledge of microbiologic patterns, informing important decisions about empiric antibacterial therapy. Diagnosis of pleural infection relies on high clinical suspicion in association with clinical features, radiology, and pleural fluid characteristics. Treatment of pleural infection is based upon accurate and often empiric choice of antibacterial agents, intercostal drainage in certain contexts, and appropriate surgical referral. Intrapleural thrombolytic therapy is not currently recommended for the treatment of pleural infection, on the basis of evidence from the largest randomized trial in empyema to date.

[Diagnosis and management of pleural effusions in critically iII patients]

INTRODUCTION

Pleural effusions are common in ICU patients. Causes include massive fluid resuscitation in shock, pneumonia--either community acquired or nosocomial, cardiac insufficiency, hypoalbuminemia and hepatic impairment. Pleural effusions frequently complicate cardiac and abdominal surgery and haemothorax may complicate trauma.

STATE OF THE ART

The incidence of pleural effusions in the intensive care unit (ICU) varies depending on the screening method used, from about 8% for physical examination to more than 60% for routine ultrasonography. In the absence of clinical parameters to exclude infection pleurocentesis remains an essential aspect of management and is not contraindicated mechanical ventilation. This review of the diagnosis and management of pleural effusions in ICU patients reports the most recent data from the literature. Pleurocentesis can be performed safely in the ICU, even in mechanically ventilated patients. The absence of reliable clinical or laboratory test criteria for determining the cause of pleural effusions and the potentially devastating consequences of failing to diagnose and treat pleural infection are strong reasons to perform pleurocentesis in patients with clinically detectable pleural effusions and no contraindication to the procedure.

PERSPECTIVES

Although the data reviewed indicate that the diagnosis and treatment of pleural effusions should follow the same rules in the ICU as they do elsewhere, several incompletely resolved issues deserve further investigation. These are summarised in an agenda for future research.