Community-acquired and nosocomial pneumonia

Pneumonia is one of the leading causes of morbidity, hospitalization, and mortality in both industrialized and developing countries. In particular, pulmonary infections acquired in the community, and pneumonias arising in the hospital setting, represent a major medical and economic problem and thus a continuous challenge to health care. For the radiologist, it is important to understand that community-acquired pneumonia (CAP) and nosocomial pneumonia (NP) share a number of characteristics, but should, in many respects be regarded as separate entities. CAP and NP arise in different populations, host different spectra of causative pathogens, and pose different challenges to both the clinician and the radiologist. CAP is generally seen in outpatients, is most frequently caused by Streptococcus pneumoniae, Mycoplasma pneumoniae, Haemophilus influenzae, and Chlamydia, and its radiologic diagnosis is relatively straightforward. NP, in contrast, develops in the hospital setting, is commonly caused by gram-negative bacteria, and may generate substantial problems for the radiologist. Overall, both for CAP and NP, imaging is an integral component of the diagnosis, important for classification and differential diagnosis, and helpful for follow-up.     

Imaging of community-acquired pneumonia: Roles of imaging examinations,imaging diagnosis of specific pathogens and discrimination from noninfectious diseases

This article reviews roles of imaging examinations in the management of community-acquired pneumonia (CAP), imaging diagnosis of specific CAP and discrimination between CAP and noninfectious diseases. Chest radiography is usually enough to confirm the diagnosis of CAP, whereas computed tomography is required to suggest specific pathogens and to discriminate from noninfectious diseases. Mycoplasma pneumoniae pneumonia, tuberculosis, Pneumocystis jirovecii pneumonia and some cases of viral pneumonia sometimes show specific imaging findings. Peribronchial nodules, especially tree-in-bud appearance, are fairly specific for infection. Evidences of organization, such as concavity of the opacities, traction bronchiectasis, visualization of air bronchograms over the entire length of the bronchi, or mild parenchymal distortion are suggestive of organizing pneumonia. We will introduce tips to effectively make use of imaging examinations in the management of CAP.     

Thin-section CT findings of patients with acute Streptococcus pneumoniae pneumonia with and without concurrent infection

Objectives

The aim of this study was to compare the pulmonary thin-section CT findings of patients with acute Streptococcus pneumoniae pneumonia with and without concurrent infection.

Methods

The study group comprised 86 patients with acute S. pneumoniae pneumonia, 36 patients with S. pneumoniae pneumonia combined with Haemophilus influenzae infection, 26 patients with S. pneumoniae pneumonia combined with Pseudomonas aeruginosa infection and 22 patients with S. pneumoniae pneumonia combined with methicillin-susceptible Staphylococcus aureus (MSSA) infection. We compared the thin-section CT findings among the groups.

Results

Centrilobular nodules and bronchial wall thickening were significantly more frequent in patients with pneumonia caused by concurrent infection (H. influenzae: p<0.001 and p<0.001, P. aeruginosa: p<0.001 and p<0.001, MSSA: p<0.001 and p<0.001, respectively) than in those infected with S. pneumoniae alone. Cavity and bilateral pleural effusions were significantly more frequent in cases of S. pneumoniae pneumonia with concurrent P. aeruginosa infection than in cases of S. pneumoniae pneumonia alone (p<0.001 and p<0.001, respectively) or with concurrent H. influenzae (p<0.05 and p<0.001, respectively) or MSSA infection (p<0.05 and p<0.05, respectively).

Conclusions

When a patient with S. pneumoniae pneumonia has centrilobular nodules, bronchial wall thickening, cavity or bilateral pleural effusions on CT images, concurrent infection should be considered.Streptococcus pneumoniae has long been recognised as the most common cause of community-acquired pneumonia (CAP) and is responsible for the increasing frequency of nosocomial pneumonia [1-3]. The mortality associated with pneumonia is linked to inadequate initial antibiotic therapy; therefore, early detection of S. pneumoniae pneumonia is important for reducing morbidity and mortality.A rapid immunochromatographic membrane test was developed for the detection of S. pneumoniae antigens in urine samples [4]. It is a useful technique for the rapid diagnosis of pneumococcal pneumonia; however, the urinary antigens cannot be detected a few days after S. pneumoniae infection, and this test is unable to detect concurrent pathogen infections.Most cases of CAP are probably caused by a single pathogen, but dual or multiple infections have been increasingly reported in the literature [5-8]. There is growing concern for the concurrent presence of a second pathogen in a significant proportion of cases of CAP previously thought to be monomicrobial [5,7-10]. De Roux et al [8] reported that in 82 patients with mixed CAP, S. pneumoniae was the most prevalent microorganism (n=44), that the most frequent combination of organisms was S. pneumoniae with Haemophilus influenzae (n=17) and that patients with mixed pyogenic pneumonia more frequently developed shock than patients with single pyogenic pneumonia.The classic chest radiographic appearances of pneumococcal pneumonia have been described as sublobar, lobar or multilobar opacities, often homogeneous with an air bronchogram [11-13]. As for CT findings, a few studies have been reported in patients with S. pneumoniae pneumonia; Miyashita et al [14] reported CT findings in 68 patients with S. pneumoniae pneumonia who were not infected with any other microorganisms.However, to the best of our knowledge, no studies have been published that compare CT findings in patients with S. pneumoniae pneumonia alone with those displaying concurrent pneumonia caused by S. pneumoniae and another pathogen. The present study therefore compared the pulmonary thin-section CT findings of patients with acute S. pneumoniae pneumonia alone with those of patients with concurrent S. pneumoniae pneumonia.     

A comparative study of thin-section CT findings between seasonal influenza virus pneumonia and Streptococcus pneumoniae pneumonia

Objective:

To compare the pulmonary thin-section CT findings in patients with seasonal influenza virus pneumonia with Streptococcus pneumoniae pneumonia.

Methods:

The study group included 30 patients (20 males and 10 females; age range, 20–91 years; mean age, 55.9 years) with seasonal influenza virus pneumonia and 71 patients (47 males and 24 females; age range, 27–92 years; mean age, 67.5 years) with S. pneumoniae pneumonia.

Results:

The proportion of community-acquired infection was significantly higher in patients with influenza virus pneumonia than with S. pneumoniae pneumonia (p = 0.001). CT findings of ground-glass attenuation (GGA) (p = 0.012) and crazy-paving appearance (p = 0.03) were significantly more frequent in patients with influenza virus pneumonia than with S. pneumoniae pneumonia. Conversely, consolidation (p < 0.001), mucoid impaction (p < 0.001), centrilobular nodules (p = 0.04) and pleural effusion (p = 0.003) were significantly more frequent in patients with S. pneumoniae pneumonia than in those with influenza virus pneumonia.

Conclusion:

Pulmonary thin-section CT findings, such as consolidation and mucoid impaction may be useful in distinguishing between seasonal influenza virus pneumonia and S. pneumoniae pneumonia.

Advances in knowledge:

(1) Distinguishing seasonal influenza virus pneumonia with S. pneumoniae pneumonia is important. (2) The CT findings of GGA and crazy-paving appearance were more frequently found in patients with influenza virus pneumonia than in patients with S. pneumoniae pneumonia, whereas consolidation, mucoid impaction, centrilobular nodules and pleural effusion were more frequently found in patients with S. pneumoniae pneumonia.Influenza virus is responsible for seasonal epidemics of community-acquired pneumonia (CAP), with outbreaks occurring predominantly during the winter months. Secondary bacterial superinfections are the most frequent complications among fatal cases of seasonal and pandemic influenza.Streptococcus pneumoniae is the most common pathogen of CAP and is also responsible for the increasing frequency of nosocomial pneumonia.^1–3 The mortality related with pneumonia is affected by initial antibiotic therapy; therefore, early detection of S. pneumoniae pneumonia is important for reducing mortality. Moreover, S. pneumoniae has been identified as the most prominent causative agent for secondary bacterial pneumonia following influenza virus infection.⁴A rapid immunochromatographic membrane test was developed for the detection of S. pneumoniae antigens.⁵ It is a useful technique for the rapid diagnosis of S. pneumoniae pneumonia; however, it does have its limitations. For example, urinary antigens of S. pneumoniae pneumonia cannot be detected a few days after S. pneumoniae infection, and assay sensitivity is approximately 70–80%.There are several reports of the radiologic features of novel influenza virus pneumonia and S. pneumoniae pneumonia.^6–8 However, there are few reports of the CT findings of seasonal influenza virus pneumonia.^9–11 Furthermore, to the best of our knowledge, no studies comparing CT findings in patients with seasonal influenza virus pneumonia to those with S. pneumoniae pneumonia have been published. The present study therefore compared the pulmonary thin-section CT findings of patients with seasonal influenza virus pneumonia to those with S. pneumoniae pneumonia.     

Differential diagnosis between the coronavirus disease 2019 and Streptococcus pneumoniae pneumonia by thin-slice CT features

ObjectiveThe chest computed tomography (CT) features of coronavirus disease 2019 (COVID-19) and Streptococcus pneumoniae pneumonia (S. pneumoniae pneumonia) were compared to provide further evidence for the differential imaging diagnosis of patients with these two types of pneumonia.MethodsClinical information and chest CT data of 149 COVID-19 patients between January 9, 2020 and March 15, 2020 and 97 patients with S. pneumoniae pneumonia between January 23, 2011 and March 18, 2020 in Zhongnan Hospital of Wuhan University were retrospectively analyzed. In addition, CT features were comparatively analyzed.ResultsAccording to the chest CT images, the probability of lung segmental and lobar pneumonia in S. pneumoniae pneumonia was higher than that in COVID-19(P<0.001); the probabilities of ground-glass opacity (GGO), the “crazy paving” sign, and abnormally thickened interlobular septa in COVID-19 were higher than those in S. pneumoniae pneumonia(P = 0.005, P<0.001, P<0.001, respectively); and the probabilities of consolidation lesions, bronchial wall thickening, centrilobular nodules, and pleural effusion in S. pneumoniae pneumonia were higher than those in COVID-19 (P<0.001, P = 0.001, P = 0.003, P = 0.001, respectively).ConclusionThe findings of GGO, the crazy paving sign, and abnormally thickened interlobular septa on chest CT were significantly higher in COVID-19 than S. pneumoniae pneumonia. The most important differential points on chest CT signs between COVID-19 and S. pneumoniae pneumonia were whether disease lesions were distributed in entire lung lobes and segments and whether the crazy paving sign, interlobular septal thickening, and consolidation lesions were found.     

Pneumonia: high-resolution CT findings in 114 patients

The objective of the present study was to assess the high-resolution CT appearances of different types of pneumonia. The high-resolution CT scans obtained in 114 patients (58 immunocompetent, 59 immunocompromised) with bacterial, Mycoplasma pneumoniae, viral, fungal, and Pneumocystis carinii pneumonias were analyzed retrospectively by two independent observers for presence, pattern, and distribution of abnormalities. Areas of air-space consolidation were not detected in patients with viral pneumonia and were less frequently seen in patients with Pneumocystis carinii pneumonia (2 of 22 patients, 9%) than in bacterial (30 of 35, 85%), Mycoplasma pneumoniae (22 of 28, 79%), and fungal pneumonias (15 of 20, 75%; p<0.01). There was no significant difference in the prevalence or distribution of consolidation between bacterial, Mycoplasma pneumoniae, and fungal pneumonias. Extensive symmetric bilateral areas of ground-glass attenuation were present in 21 of 22 (95%) patients with Pneumocystis carinii pneumonia and were not seen in other pneumonias except in association with areas of consolidation and nodules. Centrilobular nodules were present less commonly in bacterial pneumonia (6 of 35 patients, 17%) than in Mycoplasma pneumoniae (24 of 28, 96%), viral (7 of 9, 78%), or fungal (12 of 20, 92%) pneumonia (p<0.01). Except for Pneumocystis carinii pneumonia and Mycoplasma pneumoniae pneumonia, which often have a characteristic appearance, high-resolution CT is of limited value in the differential diagnosis of the various types of infective pneumonia. Electronic Publication     

Meticillin-resistant Staphylococcus aureus and meticillin-susceptible S. aureus pneumonia: comparison of clinical and thin-section CT findings

Objectives

The purpose of this study was to compare the clinical and thin-section CT findings in patients with meticillin-resistant Staphylococcus aureus (MRSA) and meticillin-susceptible S. aureus (MSSA).

Methods

We retrospectively identified 201 patients with acute MRSA pneumonia and 164 patients with acute MSSA pneumonia who had undergone chest thin-section CT examinations between January 2004 and March 2009. Patients with concurrent infectious disease were excluded from our study. Consequently, our study group comprised 68 patients with MRSA pneumonia (37 male, 31 female) and 83 patients with MSSA pneumonia (32 male, 51 female). Clinical findings in the patients were assessed. Parenchymal abnormalities, lymph node enlargement and pleural effusion were assessed.

Results

Underlying diseases such as cardiovascular were significantly more frequent in the patients with MRSA pneumonia than in those with MSSA pneumonia. CT findings of centrilobular nodules, centrilobular nodules with a tree-in-bud pattern, and bronchial wall thickening were significantly more frequent in the patients with MSSA pneumonia than those with MRSA pneumonia (p=0.038, p=0.007 and p=0.039, respectively). In the group with MRSA, parenchymal abnormalities were observed to be mainly peripherally distributed and the frequency was significantly higher than in the MSSA group (p=0.028). Pleural effusion was significantly more frequent in the patients with MRSA pneumonia than those with MSSA pneumonia (p=0.002).

Conclusions

Findings from the evaluation of thin-section CT manifestations of pneumonia may be useful to distinguish between patients with acute MRSA pneumonia and those with MSSA pneumonia.Staphylococcus aureus is one of the most common and important pathogens involved in nosocomial pneumonia, particularly because of the development of meticillin-resistant S. aureus (MRSA) [1]. Pneumonia caused by MRSA is a clinically important type of pneumonia because of its severity, the high incidence of complications, and the increased mortality it causes in nosocomial pulmonary infections [2-4].In recent years, MRSA has also emerged as an increasingly important cause of community-acquired bacterial infection, often affecting healthy children and adults who have no apparent risk factors for infection. community-acquired MRSA strains causing life-threatening infections, such as necrotising pneumonia and necrotising fasciitis, have been found to frequently carry Panton–Valentine leukocidin (PVL) genes [5-7].The mortality of pneumonia is usually associated with inadequate initial antibiotic therapy; therefore, early recognition of S. aureus pneumonia is important for reducing morbidity and mortality. Meanwhile bacteriological evaluation may take time and cause a delay in diagnosis. As such, thin-section CT may be helpful in expediting differential diagnosis of infections and in the selection of appropriate antibiotics. Recently, a small number of reports have emerged describing thin-section CT findings in patients with pathogens, including Klebsiella pneumoniae, Mycoplasma pneumoniae and Chlamydia pneumoniae [8-11]. As for S. aureus pneumonia, several studies have shown differences in clinical findings between MRSA pneumonia and meticillin-susceptible S. aureus (MSSA) pneumonia [12-13]. In a radiological study, González et al [14] reported that there were no differences on chest radiographs between 32 patients with MRSA and 54 patients with MSSA. Nguyen and colleagues [15] reported CT findings in nine patients with community-acquired MRSA, whose conditions were characterised by extensive bilateral consolidation and frequent cavitation, which is commonly associated with rapid progression and clinical deterioration. However, there are currently very few reports with radiological findings in patients with MRSA or MSSA pneumonia. Moreover, to the best of our knowledge, no studies describing the comparison of CT findings in patients with MRSA with those with MSSA have been published. As such, the current study sought to evaluate thin-section CT findings of acute MRSA pneumonia compared with those with acute MSSA pneumonia.     

Radiological findings in acute Haemophilus influenzae pulmonary infection

Objective

The aim of this study was to assess pulmonary thin-section CT findings in patients with acute Haemophilus influenzae pulmonary infection.

Methods

Thin-section CT scans obtained between January 2004 and March 2009 from 434 patients with acute H. influenzae pulmonary infection were retrospectively evaluated. Patients with concurrent infection diseases, including Streptococcus pneumoniae (n=76), Staphylococcus aureus (n=58) or multiple pathogens (n=89) were excluded from this study. Thus, our study group comprised 211 patients (106 men, 105 women; age range, 16–91 years, mean, 63.9 years). Underlying diseases included cardiac disease (n=35), pulmonary emphysema (n=23), post-operative status for malignancy (n=20) and bronchial asthma (n=15). Frequencies of CT patterns and disease distribution of parenchymal abnormalities, lymph node enlargement and pleural effusion were assessed by thin-section CT.

Results

The CT findings in patients with H. influenzae pulmonary infection consisted mainly of ground-glass opacity (n=185), bronchial wall thickening (n=181), centrilobular nodules (n=137) and consolidation (n=112). These abnormalities were predominantly seen in the peripheral lung parenchyma (n=108). Pleural effusion was found in 22 patients. Two patients had mediastinal lymph node enlargement.

Conclusion

These findings in elderly patients with smoking habits or cardiac disease may be characteristic CT findings of H. influenzae pulmonary infection.Haemophilus influenzae is an important pneumonia pathogen because of its severity, high incidence of complications and high mortality. This Gram-negative bacillus frequently colonises the human upper respiratory tract, especially the nasopharynx, and is considered to form part of the normal respiratory flora [1]. Most H. influenzae infections are the result of direct extension from the nasopharynx to the lower respiratory tract [1].H. influenzae infection has received increasing attention because it is an important factor in the acute exacerbation of chronic obstructive pulmonary disease (COPD) [1,2]. Acute exacerbation is a frequent event during the prolonged chronic course of COPD, which entails significant morbidity and mortality, and the main aetiology for the majority of episodes is infection.The mortality rate in patients with H. influenzae pneumonia has been reported as 10–42% [3-6]. Moreover, nosocomial outbreaks caused by H. influenzae have been reported [7]. Therefore, it is important to identify the risk factors associated with H. influenzae infection and to evaluate the radiological findings so that no time is lost in initiating appropriate management.Several studies have presented the clinical and microbiological findings in patients with H. influenzae infection [1-4,6,7]. The characteristics of H. influenzae pneumonia on plain radiography have also been described previously [1,8]. Recently, Nei et al [8] have described CT findings of Mycoplasma pneumoniae pneumonia and community-acquired pneumonia caused by other organisms, including 12 patients with H. influenzae pneumonia. The CT finding of bronchial wall thickening in patients with H. influenzae pneumonia was more common than in patients with Streptococcus pneumoniae or Klebsiella pneumoniae.However, to the best of our knowledge, no other English-language studies of pulmonary CT findings in patients with acute H. influenzae pneumonia have been published. This study aimed to assess the clinical findings and pulmonary thin-section CT findings in patients with acute H. influenzae pneumonia.     

血清降钙素原在社区获得性肺炎诊断与病情评估中的价值

目的探讨血清降钙素原（PCT）在社区获得性肺炎（CAP）诊断和病情评估中的价值。方法选取2011年5月～2012年5月于本院治疗的72例CAP患者为研究对象,根据CURB-65评分,将所有CAP患者分为轻、中、重症肺炎,并选取健康人群28例为对照组。检测两组血清中PCT浓度,对其相关数据进行统计分析及比较。结果 CAP组治疗后和对照组PCT浓度与治疗前相比较均具有显著性差异（P〈0.05）;并发症组和无并发症组PCT浓度比较具有显著性差异（P〈0.05）;重症组PCT浓度与轻症组和中症组相比较,均具有显著性差异（P〈0.05）;PCT与肺炎严重程度存在相关性,相关系数r=0.620（P〈0.05）。结论病情越重的细菌感染肺炎患者,血清PCT浓度越高,PCT水平检测可为CAP的诊断与病情评估提供科学依据。     

Comparison of plain chest radiography and high-resolution CT in human immunodeficiency virus infected patients with community-acquired pneumonia: a sub-Saharan Africa study

The objective of the study was to determine the proportion of patients with missed lesions on plain chest radiographs compared with high-resolution computed tomography (HRCT) in 49 human immunodeficiency virus (HIV) infected patients with community-acquired pneumonia (CAP). Patients underwent plain chest radiography and HRCT scans of the chest at admission. Microbiological investigations for CAP were performed. An experienced radiologist, without knowledge of clinical or pathological data, reported the chest radiographs and HRCT scans. The study group included 26 females and 23 males, aged 18-53 years (mean age 36 years). Organisms were isolated from 26 patients (53%). In 40 patients (82%), the HRCT scans demonstrated lesions not visualized on the plain chest radiographs. There was 100% correlation between plain radiographic and HRCT scan findings in nine cases (18%). Lesions that were not visualized on the plain radiographs but elucidated on HRCT included: pleural effusion (n = 14), ground-glass opacification (n = 20), pericardial effusion (n = 8), cavitation (n = 4), cysts (n = 4), bullae (n = 4), abscess (n = 1) and pneumothorax (n = 1). In 20 of 23 cases, hilar lymphadenopathy, identified on HRCT, was not recognized on plain chest radiographs. In patients in whom an organism was isolated, a correct HRCT diagnosis of pulmonary tuberculosis, bacterial pneumonia and Pneumocystis carinii pneumonia (PCP) was made in 80%, 84% and 100% of cases, respectively. The proportion of patients with missed lesions on plain chest radiographs in HIV infected patients with CAP was high. This has important implications for management and prognosis. HRCT scans correlate well with the microbiological diagnosis when reported by an experienced radiologist.     

Adult chest radiograph reporting by radiographers: Preliminary data from an in-house audit programme

AimTo examine the adult chest radiograph (CXR) reporting performance of a reporting radiographer in clinical practice using different audit systems; single radiologist and two radiologists, with clinical review of discordant cases.Materials and methods100 chest radiographs (CXRs) were drawn randomly from a consecutive series of 4800 CXRs which had been reported during a nine month period at a district general hospital by a radiographer after two years of training. Diagnostic outcomes were normal or abnormal, and agreement with the reporting radiographer or not. There was 50% duplication of CXRs reported between three radiologists. Concordance rates were determined for the radiographer-radiologist and inter-radiologist interpretations. Independent clinical review of discordant cases was performed to establish the final diagnosis.ResultsNinety-nine cases were reviewed, with 40 cases deemed abnormal by at least one radiologist. Consensus was found with the radiographers report in 59 normal and 33 abnormal CXRs reviewed by two radiologists (96.7% and 86.8% respectively). Seven CXR reports were discrepant with clinical review: mediastinal lymphadenopathy was missed by both radiologist and radiographer; linear atelectasis was reported by two radiologists but not the radiographer. Three cases were over-interpreted and on two occasions at least one radiologist agreed with the radiographer. There was very high concordance between the radiographer and each radiologist, 96%, 96% and 92% respectively.ConclusionsThis study suggested that regular audit, which incorporates case note review and discrepant reporting within a multidisciplinary setting, should contribute to safe practice.     

Impact of clinical data on chest radiography sensitivity in detecting pulmonary abnormalities in immunocompromised patients with suspected pneumonia

Purpose

Chest radiography (CXR) of immunocompromised patients has low sensitivity in the early evaluation of pulmonary abnormalities suspected to be infectious. The purpose of the study was to evaluate whether the knowledge of clinical data improves the diagnostic sensitivity of CXR in the particular setting of immunocompromised patients after hematopoietic stem cell transplantation (HSCT).

Materials and methods

Sixty-four CXRs of immunocompromised patients with clinically suspected pneumonia were retrospectively and independently evaluated by two radiologists to assess the presence of radiological signs of pneumonia, before (first reading) and after (second reading) the knowledge of clinical data. A chest computed tomography (CT) performed within 3 days was assumed as the standard of reference. For each reading, sensitivity of both radiologists was calculated.

Results

Readers showed a sensitivity of 39% and 58.5% for the first reading, and 43.9% and 41.5% for the second reading, respectively. For both readers, these values were not significantly different from those obtained at first reading (McNemar’s test, p>0.05). Interobserver agreement at second reading was fair (Cohen test, k=0.33).

Conclusions

The sensitivity of CXR is too low to consider it a stand-alone technique for the evaluation of immunocompromised patients after HSCT with suspected pneumonia, even if the radiologist knows detailed clinical data. For these patients, an early chest CT evaluation is therefore recommended.     

Acute Klebsiella pneumoniae pneumonia alone and with concurrent infection: comparison of clinical and thin-section CT findings

The purpose of this study was to identify the clinical and thin-section CT findings in patients with acute Klebsiella pneumoniae pneumonia (KPP) alone and with concurrent infection. We retrospectively identified 160 patients with acute KPP who underwent chest thin-section CT examinations between August 1998 and August 2008 at our institution. The study group comprised 80 patients (54 male, 26 female; age range 18–97 years, mean age 61.5) with acute KPP alone, 55 (43 male, 12 female; age range 46–92 years, mean age 76.0) with KPP combined with methicillin-resistant Staphylococcus aureus (MRSA) and 25 (23 male, 2 female; age range 56–91 years, mean age 72.7) with KPP combined with Pseudomonas aeruginosa (PA). Underlying diseases in patients with each type of pneumonia were assessed. Parenchymal abnormalities were evaluated along with enlarged lymph nodes and pleural effusion. In patients with concurrent pneumonia, underlying conditions such as cardiac diseases, diabetes mellitus and malignancy were significantly more frequent than in patients with KPP alone. The mortality rate in patients with KPP combined with MRSA or PA was significantly higher than in those with KPP alone. In concurrent KPP, CT findings of centrilobular nodules, bronchial wall thickening, cavity, bronchiectasis, nodules and pleural effusion were significantly more frequent with concurrent pneumonia than in those with KPP alone.Klebsiella pneumoniae is among the most common Gram-negative bacteria encountered by physicians worldwide, and accounts for 0.5–5.0% of all cases of pneumonia. It is a clinically important type of pneumonia because of its severity, high incidence of complications and increased mortality [1–3]. The mortality rate in alcoholics with Klebsiella pneumoniae pneumonia (KPP) has been reported to be as high as 50–60% [4, 5].The characteristics of KPP on plain radiography have been described previously [1, 3, 6–9]. Felson et al [8] have studied 14 patients with acute KPP and reported that the presence of certain radiological features supports a diagnosis of acute KPP. These features are bulging fissures, sharp margins of the advancing border of the pneumonic infiltrate and early abscess formation.Recently, we have reported that in 764 of 962 patients (79.4%) with acute KPP, 1 or more additional pathogens, predominantly methicillin-resistant Staphylococcus aureus (MRSA) (36.7%) and Pseudomonas aeruginosa (PA) (23.3%), were found [10].To the best of our knowledge, no studies have compared the pulmonary CT findings in patients with acute and concurrent KPP. Therefore, the present study compared the clinical and pulmonary thin-section CT findings of patients with acute KPP alone and concurrent KPP with MRSA or PA.     

CT differentiation of pyogenic liver abscesses caused by Klebsiella pneumoniae vs non-Klebsiella pneumoniae

Objective

Klebsiella pneumoniae is one of the organisms most commonly isolated from pyogenic liver abscesses in Asian populations. We compared CT findings in liver abscesses caused by K. pneumoniae with those caused by other bacterial pathogens.

Methods

Of 214 patients with liver abscesses examined over a 5 year period, 129 patients with positive blood or aspirate cultures were enrolled. The patients were divided into two groups: the K. pneumoniae monomicrobial liver abscess (KLA) group (n = 59) and the non-K. pneumoniae monomicrobial or polymicrobial liver abscess (non-KLA) group (n = 70). Two radiologists blinded to the culture results evaluated the CT images, recording the number, size, location and configuration of abscesses, the thickness of the abscess wall, the pattern of rim enhancement, septal enhancement, the double target sign, internal necrotic debris, internal gas bubbles and underlying biliary disease. The presence of diabetes and metastatic infection was also compared between groups. Statistical analyses were performed using univariate (Student''s t-test and χ² test) and multivariate analyses.

Results

Multivariate analysis showed that a thin wall, necrotic debris, metastatic infection and the absence of underlying biliary disease were the most significant predictors of KLA. When three of the four criteria were used in combination, a specificity of 98.6% was achieved for the diagnosis of KLA.

Conclusion

A thin-walled abscess, internal necrotic debris, the presence of metastatic infection and the absence of underlying biliary disease may be useful CT findings in the early diagnosis of K. pneumoniae liver abscesses.Pyogenic liver abscesses are caused by a wide range of bacteria. Escherichia coli was previously the most common causative pathogen of pyogenic liver abscesses. Recently, however, Klebsiella pneumoniae has become the leading cause of pyogenic liver abscesses in many Asian populations and in some Western populations [1-6].There are several distinct clinical differences between K. pneumoniae liver abscesses (KLA) and non-K. pneumoniae liver abscesses (non-KLA). First, compared with other bacterial liver abscesses, KLA are associated with a higher frequency of bacteraemia and the potential for metastatic infection in other parts of the body. Although the mortality rate is generally lower for KLA than for non-KLA (4.1 vs 20.8%), the prognosis of KLA is often poor in patients with metastatic infection [6]. Second, ampicillin is ineffective against KLA because K. pneumoniae is intrinsically resistant to ampicillin. The preferred antibiotics for KLA are aminoglycoside and extended-spectrum β lactams. Thus, a high index of suspicion for KLA should be maintained when selecting antibiotic coverage. Third, non-KLA occur in patients with underlying biliary disease, whereas KLA frequently occur in the absence of any underlying biliary disease or predisposing medical condition [2-8].Although the early recognition of KLA is important, the differentiation between KLA and non-KLA can be difficult. In fact, the clinical presentation and laboratory findings of patients with KLA are similar to those of patients with other pyogenic liver abscesses. Blood or pus culture is the standard method for the identification of bacterial pathogens, but these methods require several days to produce results, thus delaying treatment.Imaging modalities, such as ultrasonography and CT, have been used to diagnose liver abscesses, to identify possible causes and to rule out other intra-abdominal conditions that cause similar symptoms [9,10]. However, only a few reports regarding the use of ultrasonography or CT in the differentiation of KLA and non-KLA have been published [11,12]. To our knowledge, there is only one published report on distinctive CT features in the differentiation of KLA and non-KLA [12], and no report has identified predictors that can be used to distinguish KLA from other bacterial liver abscesses using CT images. Thus, the purpose of our study was to retrospectively compare the clinical and CT features of pyogenic liver abscesses caused by K. pneumoniae and other bacterial pathogens, and to identify differences that may assist in differential diagnosis.     

Organizing pneumonia associated with <Emphasis Type="Italic">Mycoplasma pneumoniae</Emphasis> infection

Mycoplasma pneumoniae infection is known to produce infiltrative and/or nodular opacities that are often localized. A patient presented to us with diffuse centrilobular, peribronchovascular, and perilobular opacities after documented Mycoplasma pneumoniae infection. A surgical biopsy proved the lung disease to be organizing pneumonia, which dramatically resolved in response to treatment with corticosteroid. This case represents an unusual radiological manifestation associated with M. pneumoniae infection, thereby stressing the importance of this disease in the differential diagnosis for patients with diffuse opacities of the lungs.     

Comparison of Chest Radiograph Impressions for Diagnosing Pneumonia: Accounting for Categories of Language Certainty

ObjectivesUncertain language in chest radiograph (CXR) reports for the diagnosis of pneumonia is prevalent. The purpose of this study is to validate an a priori stratification of CXR results for diagnosing pneumonia based on language of certainty.DesignRetrospective chart review.Setting and participantsCXR reports of 2,411 patient visits ≥ 18 years, admitted to medicine, who received a CXR and noncontrast chest CT within 48 hours of emergency department registration at two large academic hospitals (tertiary and quaternary care) were reviewed.MethodsThe CXR and CT report impressions were categorized as negative, uncertain, or positive. Uncertain CXRs were further stratified into four categories based on language modifiers for the degree of pneumonia certainty. Comparison of CXR and CT results were determined using χ² test; a P value of less than .0033 was considered significant to account for multiple comparisons.ResultsCXR reports for the diagnosis of pneumonia revealed the following distribution: 61% negative, 32% uncertain, and 7% positive; CT reports were 55% negative, 22% uncertain, and 23% positive for the diagnosis of pneumonia. There were significant differences between CXR categories compared with CT categories for diagnosis of pneumonia (P < .001). Negative CXR results were not significantly different than the uncertain category with the most uncertain language (P = .030) but were significantly different from all other uncertain categories and positive CXR results (each P < .001). Positive CXR results were not significantly different than the least uncertain category (most certain language) (P = .130) but were significantly different from all other categories (each P < .001).Conclusions and implicationsLanguage used in CXR reports to diagnose pneumonia exists in categories of varying certainty and should be considered when evaluating patients for pneumonia.     

Diagnostic performance of qualitative and radiomics approach to parotid gland tumors: which is the added benefit of texture analysis?

Objective:To investigate whether MRI-based texture analysis improves diagnostic performance for the diagnosis of parotid gland tumors compared to conventional radiological approach.Methods:Patients with parotid gland tumors who underwent salivary glands MRI between 2008 and 2019 were retrospectively selected. MRI analysis included a qualitative assessment by two radiologists (one of which subspecialized on head and neck imaging), and texture analysis on various sequences. Diagnostic performances including sensitivity, specificity, and area under the receiver operating characteristic curve (AUROC) of qualitative features, radiologists’ diagnosis, and radiomic models were evaluated.Results:Final study cohort included 57 patients with 74 tumors (27 pleomorphic adenomas, 40 Warthin tumors, 8 malignant tumors). Sensitivity, specificity, and AUROC for the diagnosis of malignancy were 75%, 97% and 0.860 for non-subspecialized radiologist, 100%, 94% and 0.970 for subspecialized radiologist and 57.2%, 93.4%, and 0.927 using a MRI radiomics model obtained combining texture analysis on various MRI sequences. Sensitivity, specificity, and AUROC for the differential diagnosis between pleomorphic adenoma and Warthin tumors were 81.5%, 70%, and 0.757 for non-subspecialized radiologist, 81.5%, 95% and 0.882 for subspecialized radiologist and 70.8%, 82.5%, and 0.808 using a MRI radiomics model based on texture analysis of T₂ weighted sequence. A combined radiomics model obtained with all MRI sequences yielded a sensitivity of 91.5% for the diagnosis of pleomorphic adenoma.Conclusion:MRI qualitative radiologist assessment outperforms radiomic analysis for the diagnosis of malignancy. MRI predictive radiomics models improves the diagnostic performance of non-subspecialized radiologist for the differential diagnosis between pleomorphic adenoma and Warthin tumor, achieving similar performance to the subspecialized radiologist.Advances in knowledge:Radiologists outperform radiomic analysis for the diagnosis of malignant parotid gland tumors, with some MRI qualitative features such as ill-defined margins, perineural spread, invasion of adjacent structures and enlarged lymph nodes being highly specific for malignancy. A radiomic model based on texture analysis of T₂ weighted images yields higher specificity for the diagnosis of pleomorphic adenoma compared to a radiologist non-subspecialized in head and neck radiology, thus minimizing false-positive pleomorphic adenoma diagnosis rate and reducing unnecessary surgical complications.     

Acoustic radiation force impulse-imaging and transient elastography for non-invasive assessment of liver fibrosis and steatosis in NAFLD

Background

Transient elastography (TE) and acoustic radiation force impulse (ARFI)-imaging have shown promising results for the staging of liver fibrosis.

Aim

The aim of the present study was to compare ARFI of the left and right liver lobe with TE using the standard and obese probes for the diagnosis of liver fibrosis in NAFL/NASH. In addition, liver steatosis is evaluated using the novel controlled attenuation parameter (CAP).

Methods

Sixty-one patients with NAFLD/NASH were included in the study. All patients received TE with both probes, ARFI of both liver lobes and CAP. The results were compared with liver histology.

Results

57 patients were included in the final analysis. The diagnostic accuracy for TE measurements with the M-and XL-probe and for ARFI of the right and left liver lobe was 0.73, 0.84, 0.71 and 0.60 for the diagnosis of severe fibrosis, and 0.93, 0.93, 0.74 and 0.90 for the diagnosis of cirrhosis, respectively. No significant difference of results was observed between TE and ARFI in the subgroup of patients with reliable TE-measurement when taking into account the best results of both methods. However, while a significant correlation could be found for TE with histological liver fibrosis, the correlation of ARFI with liver fibrosis was not statistically significant. A significant correlation was found for CAP with histological steatosis (r = 0.49, p < 0.001).

Conclusions

No significant difference in diagnostic accuracy for the non-invasive assessment of liver fibrosis was found for transient elastography and ARFI. Nevertheless TE significantly correlated with liver fibrosis while ARFI did not. CAP enables the non-invasive assessment of steatosis.