Video-assisted thoracoscopic decortication for management of postpneumonic pleural empyema

BACKGROUND: Video-assisted thoracoscopic surgery (VATS) for decortication or debridement in the management of empyema thoracis has increased the available treatment options but requires validation. We present and evaluate our technique and experience with thoracoscopic management of pleural empyema, irrespective of chronicity. METHODS: From May 1, 2000, to April 30, 2002, VATS debridement and decortication in 70 consecutive patients presenting with pleural space infections was performed with endoscopic shaver system. A retrospective review was performed and the effect of this technique on perioperative outcome was assessed. RESULTS: The VATS evacuation of infected pleural fluid and decortication was successfully performed in 65 of 70 patients. The mean duration of preoperative symptoms before referral was 23 +/- 1.8 days. The mean duration of hospitalization before transfer was 13.5 +/- 1.5 days. Blood loss was 330 +/- 200 mL. Intercostal drainage was required for 5 +/- 3 days. The postoperative hospital stay was 5 +/- 0.7 days. There were no operative mortalities. CONCLUSIONS: Video-assisted thoracoscopic decortication with endoshaver system is a simple and effective method in the management of the fibropurulent or organic pleural empyema.     

Video-assisted thoracoscopic surgery for children with stage II empyema

Children with stage II empyema often fail traditional medical management, frequently succumbing to the effective albeit morbid clutches of thoracotomy. Video-assisted thoracoscopic surgery (VATS) has been recently introduced as a viable and potentially less morbid alternative to open thoracotomy. We review our VATS experience in children with empyema, assessing surgical outcome. Between August 1996 and March 1999, 13 patients at our institution with stage II empyema that did not respond to conventional medical management underwent a modified VATS with decortication. Data from retrospective chart review reflects intraoperative findings and postoperative course, including average time to defervescence, removal of thoracostomy tube, and hospital discharge. VATS was completed in all 13 patients. All intraoperative cultures of pleural fluid and fibrinopurulent debris obtained at VATS showed no growth. The average time to defervescence was 2.2 days (range, 0-4 days) and to removal of thoracostomy tube 3.6 days (range, 2-5 days). Average total chest tube days in patients with pre-VATS thoracostomy (n = 6) was 14.5 days (range, 8-37 days) versus 3.1 days (range, 2-5 days) in patients (n = 7) who underwent primary VATS (t test, p < 0.05). The average time to surgical discharge after VATS was 5.8 days (range, 3 to 19 days). All patients were well on follow-up clinic visits without delayed complications. VATS can be performed safely and effectively in children with stage II empyema, thus avoiding the morbidity of open thoracotomy and decortication. Importantly, early application of VATS significantly relieves patients of unnecessary days of thoracostomy drainage.     

Current treatment of pediatric empyema

Pneumonia with complicated parapneumonic effusion and empyema is increasing in incidence and continues to be a source of morbidity in children seen in our institution. Current diagnostic modalities include chest radiographs and CT scanning with ultrasound being helpful in some situations. Exact management of empyema remains controversial. Although open thoracotomy drainage is well accepted in children, video-assisted thoracoscopic surgery (VATS) drainage has become more prevalent in the current era. Over the last 4 years, we have treated 58 children with intrapleural placement of pigtail catheters and administration fibrinolytics consisting of tissue plasminogen activator (tPA). Successful drainage and resolution of 54 of the 58 effusions was achieved with percutaneous methods alone. There was no mortality or 30-day recurrence. Mean hospital stay was 9.1 days (range 5 to 21) and mean chest catheter removal was 6 days post placement (range 1.5 to 20). Of the four patients that failed percutaneous tube therapy, 3 underwent video assisted thoracic surgery (VATS), and one had open thoracotomy with decortication. Based on our experience, tPA administered through a small bore chest tube for drainage of complicated parapneumonic effusions has become our standard practice. We reserve VATS for treatment failures and open thoracotomy and decortication for patients with VATS failure.     

Video-assisted evacuation of empyema is the preferred procedure for management of pleural space infections

BACKGROUND: Empyema remains a cause of morbidity and mortality. Thoracoscopy has proved its versatility in the management of pleural space disorders. The suitability of video-assisted thoracic surgery (VATS) for decortication in the management of the fibrotic stage of empyema is unclear. METHODS: VATS evacuation of empyema and decortication was performed on seventeen patients presenting with pleural space infections. A retrospective review was performed and constitutes the basis of this report. RESULTS: VATS evacuation of empyema and decortication was successfully performed in 13 of 17 patients. Blood loss was 325 +/- 331 cc. Mean hospital stay was 18 +/- 10 days. Postoperative hospitalization was 11 +/- 7 days. Chest tubes remained in place for 7 +/- 3 days. There were no operative mortalities. CONCLUSIONS: Video-assisted evacuation of empyema and decortication is an effective modality in the management of the exudative and fibrinopurulent stages of empyema. An organized empyema should be approached thoracoscopically, but may require open decortication.     

Surgical therapy of pleural empyema

In the period from January 1976 to December 1986, 31 (56.3%) out of 55 patients with pleural empyema were treated, after failure of conservative treatment with antibiotic drugs, pleural puncture and tube drainage. Twenty-two patients were submitted to a posterolateral thoracotomy with debridement in the early stage or decortication in the later stage of empyema thoracis. There was no relapse of empyema in this group, but 7 patients suffered from air leakage for 7 to 19 days (mean 12 days). One patient needed rethoracotomy after debridement for continuous bleeding. Nine patients were treated in a first step with limited thoracotomy in local anaesthesia with or without costotomy. There were 5 relapses of empyema in this group. The average time of hospitalization was for the debrided cases 13.6 days and for the decortication group 19.6 days. The conservatively treated group remained during 39.5 days in the hospital.     

Primary thoracoscopic treatment of empyema in children

OBJECTIVE: The optimal treatment of pediatric empyema remains controversial. The objective of this study is to compare the use of conventional management versus primary thoracoscopic drainage and decortication in children with empyema. METHODS: Conventional management has consisted of chest drain insertion under general anesthesia plus intravenous antibiotics. Thoracoscopic drainage and decortication has consisted of primary thoracoscopic drainage and decortication plus antibiotics. The clinical course of 54 patients treated conventionally between 1989 and 1997 was compared with that of 21 patients treated by means of thoracoscopic drainage and decortication between September 2000 and September 2001. RESULTS: Results of the study demonstrated that patients in the drainage-decortication group had fewer invasive interventions per patient than those in the conventional management group (1.0 vs 1.26). Patients undergoing thoracoscopic drainage and decortication also had significantly shorter durations of intravenous antibiotic therapy (7.6 +/- 1.2 vs 18.2 +/- 7.5 days), chest tube drainage (4.0 +/- 0.5 vs 10.2 +/- 6.1 days), and hospital stays (7.4 +/- 0.8 vs 15.4 +/- 7.4). Moreover, there were no open thoracotomies and decortications in the thoracoscopic drainage and decortication group, whereas in the conventional management group 39% (21/54) of patients underwent an open procedure. CONCLUSION: Although the 2 groups were not prospectively randomized and they were treated in different time periods, the results of this study support the use of thoracoscopic surgery as the primary therapeutic modality in children presenting with pleural empyema. This strategy appears to offer significant benefits over conventional treatment in terms of duration of treatment and the need for more invasive surgery.     

Thoracoscopic decortication: first-line therapy for pediatric empyema

Video-assisted thoracoscopic surgery (VATS) has become a popular and well-refined procedure. It has several advantages over open thoracotomy in terms of invasiveness and cosmetics. The aim of this study is to consider if VATS can serve as primary management for pediatric empyema. Between October 2000 and December 2002, 13 children with empyema receiving VATS were retrospectively reviewed. Of them, 5 had tube thoracostomy before VATS intervention (group T), and 8 had VATS as the initial treatment (group V). Their mean (+/- SD) age of groups V and T were 5.75 +/- 4.43 and 4.0 +/- 1.58 years, respectively. The children of group V had a shorter length of hospital stay (group V 10.7 +/- 3.54 days; group T 28.2 +/- 8.32 days), a shorter period of chest tube drainage (group V 5 +/- 1.87 days; group T 25 +/- 11.08 days), less transfusion (group V 0.4 +/- 0.17 units; group T 0.9 +/- 0.27 units) and less radiation exposure (group V 10.3 +/- 3.49; group T 23.4 +/- 11.64). No mortality was noted in the entire series. We conclude that primary VATS is a safe, effective and definitive method which can serve as first-line therapy for children with empyema.     

Video-assisted thoracoscopic surgery for thoracic empyema: primarily, or after fibrinolytic therapy failure?

BACKGROUND: Traditional and modern treatments are proposed for thoracic empyema. The efficacy of video-assisted thocoscopic surgery (VATS) has been studied when the method is applied either as primary treatment for thoracic empyema or after the failure of fibrinolytic therapy. METHODS: Thirty-eight patients treated with VATS for thoracic empyema have been reviewed. Of those, 20 patients (group 1) with empyema thoracis were referred to VATS after failure of the fibrinolytic treatment. Another 18 patients (group 2) with primary empyema thoracis were treated thoracoscopically immediately when empyema was diagnosed. Both groups were staged 5, 6, or 7 according to Light's criteria. RESULTS: The group 2 patients showed a higher empyema resolving rate (95% versus 85%), shorter hospital stay (4.5 versus 7.5 days), and significantly shorter duration of the procedure (70 +/- 14 versus 62 +/- 10 minutes) in comparison with the patients of group 1. CONCLUSIONS: The VATS technique for thoracic empyema is a well-tolerated, minimally invasive technique, with excellent therapeutic results, mild postoperative complications, and reduced hospitalization. VATS should be considered as the treatment of choice for thoracic empyema, in the fibrinopurulent stage, as it is more effective when applied primarily than when applied after fibrinolytic therapy.     

Early decortication in childhood empyema thoracis

Thoracic empyema is a life-threatening condition in paediatric surgical practice and the appropriate management still remains controversial. The authors reviewed 79 (37 boys, 42 girls) cases of empyema thoracis who underwent thoracotomy and decortication between 1990 and 2005. The initial diagnosis based on history, physical examination and radiology was confirmed by thoracentesis. Fever, cough and dyspnoea were the most common presenting symptoms. In all cases aerobic cultures were performed and Staphylococcus aureus was the most common microorganism isolated. All patients except three received antibiotics and tube drainage as an initial treatment. The decision for early decortication was based on persistence of fever, dyspnoea, air leakage and lack of resolution on CT scan, in spite of medical therapy and tube drainage, at the end of 10 days. All but one with wound dehiscence showed rapid recovery and they were discharged on the fifth to eighth postoperative days. In conclusion, early decortication is a safe and curative treatment in childhood empyema thoracis with low morbidity.     

Empyema thoracis: a problem with late referral?

BACKGROUND--Patients are often referred to thoracic units for management of empyema after the acute phase has been treated with antibiotics but without adequate drainage. This study evaluates the effects of delay in surgical treatment of empyema thoracis on morbidity and mortality. METHODS--Thirty nine consecutive patients were studied from January 1991 to June 1992. Two groups (group 1, 16 patients; group 2, 23 patients) were compared depending on the time spent under the care of other specialists before referral to the thoracic unit (group 1, seven days or less; group 2, eight days or more). The reasons for delay in referral were analysed. RESULTS--Four patients were treated conservatively with chest drainage alone (all in group 1). Thirty five patients required rib resection and drainage of their empyema (group 1, 12 patients; group 2, 23 patients). Nineteen (all in group 2) of the 35 patients who had rib resections went on to have decortication. The commonest cause of empyema was post-pneumonic (37 out of 39 patients). Staphylococcus aureus was the commonest organism isolated. Misdiagnosis (five patients), inappropriate antibiotics (six patients), and inappropriate placement of chest drainage tubes (three patients) all contributed to persistence and eventual progression of empyema. The overall mortality was 10% and mortality increased with age. The median stay in hospital was 9.5 days (range 7-12 days, n = 4) for patients treated with closed tube drainage only; 18 days (range 10-33 days, n = 16) for patients who had undergone rib resections and open drainage; and 28 days (range 22-49 days, n = 19) for patients who underwent decortication. The likelihood of having a staged procedure (antibiotics, closed tube drainage, open drainage with rib resection, and finally decortication) increased when closed tube drainage was persevered with for more than seven days. The total hospital stay was positively related with the time before referral for surgical treatment. Anaemia, low albumin concentrations, and worsening liver function were found in group 2 compared with group 1. CONCLUSIONS--Early adequate operative drainage in patients with empyema results in low morbidity, shorter stays in hospital, and good long term outcome. These patients should be treated aggressively and early referral for definitive surgical management is recommended.     

Video-thoracoscopic and open surgical management of thoracic empyema

PURPOSE: To evaluate the outcomes of video-thoracoscopic and open surgical management of patients with thoracic empyema. METHODS: We studied 122 patients retrospectively who underwent surgery for thoracic empyema in our hospital between January, 1999 and January, 2005. Patients' medical records, surgical procedures, and outcomes were reviewed. The study identified 97 affected men and 25 affected women with a mean age of 54 years (range 16-78 years). The empyema was parapneumonic in 95 patients (78%). RESULTS: Forty-four patients who had stage II empyema underwent video-assisted thoracic surgery (VATS). The procedure was converted to thoracotomy in 13 patients (29.5%); the morbidity and mortality rates of VATS were 13% and 0, respectively. Seventy-eight patients had stage III empyema and, along with those 13 who were converted, underwent thoracotomy for decortication. The associated morbidity rate was 12%, and the mortality rate was 6.6%. Thoracotomy was considered successful in 90 of 91 patients (99%); one patient needed a reoperative thoracotomy for an organ space/surgical site infection with pus in the pleural cavity. CONCLUSIONS: Many treatment modalities are available for thoracic empyema, depending on the results of appropriate clinical and laboratory investigations. In fibrinopurulent empyema, VATS debridement is safe and effective, with minimal morbidity and no deaths. Lung decortication via thoracotomy is the only option for organized empyema and is associated with a substantial mortality rate.     

Video-Assisted Thoracoscopic Surgery in the Treatment of Chronic Empyema Thoracis

We prospectively analyzed the surgical results in chronic organizing empyema thoracis utilizing a video-assisted thoracoscopic technique, particularly in debilitated patients. From January 1999 to September 2000, ten patients with stage III empyema thoracis underwent video-assisted thoracoscopic surgery for decortication (VATD). The mean age of the patients was 53.2 years, and they included one female and nine male patients. Four patients were regarded as not suitable for open thoracotomy. After the procedure, all patients had one infusion tube and two 32-F chest tubes inserted, the former for irrigation with saline solution and the latter for drainage. The mean operation time was 178 min. There was no mortality. The mean time to remove the infusion tube was 3.3 days. The mean time to remove the first chest tube was 7.1 days and the second chest tube 9.7 days. The mean hospitalization time after the operation was 14.9 days. The mean follow-up was 14.9 months. A restoration of lung function was ascertained in nine patients, with a 17.6% mean increase in forced vital capacity. There was no recurrence of empyema during the follow-up. Nevertheless, a reaccumulation of pleural effusion occurred in one patient 1 month after the procedure, which thus necessitated further treatment. VATD is considered to be a feasible surgical modality for the treatment of stage III empyema thoracis in selected patients. Received: January 22, 2001 / Accepted: July 17, 2001     

The treatment of thoracic empyema by video-assisted thoracic surgery (VATS)

Despite various treatment options, empyema thoracis remains associated with important morbility and mortality. Diffused or loculated empyema developed through exudative, purulent and organized phases. Clinically, these phases corresponding to the evolution of the disease: acute and chronic one. The treatment of empyema thoracis is also correlated with the general condition of the patient and even if the drainage is satisfactory in the exudative form, these surgical procedure may be not curative in the purulent and chronic phase. In these cases empyemectomy and pleural decortication are treatment of choice. Recently, Video Assisted Thoracic Surgery has assumed greater importance in the management of this pathology. In our Department of General and Thoracic Surgery, on 178 patients with chronic empyema thoracis, 26 were underwent VATS. During the follow-up there was no mortality or recurrence of empyema. The results indicate VATS because of higher efficacy, shorter hospital stay and less cost, is the primary surgical treatment of chronic empyema thoracis.     

Surgical treatment of pleural empyema--changing priorities

The surgical management of pleural empyema and post-traumatic clotted haemothorax is described. The study included 15 cases of post-thoracotomy empyema, 23 of empyema of other aetiology and five of post-traumatic haemothorax. Chest-tube drainage was the first measure in most cases. Post-pneumonectomy empyema was treated with partial thoracoplasty plus omentoplasty (8 cases) or plus myoplasty (1 case). Empyema after lobectomy or bilobectomy (4 cases) or after failed decortication (1 case) was managed with thoracoplasty or, in cases of concomitant wound infection, with open-window thoracostomy followed by thoracoplasty. Empyema after subclavian artery reconstruction (1 case) was cleared by removal of a previously unrecognized foreign body. For early empyema of other aetiology or haemothorax (10 cases in total), treatment comprised debridement by video-assisted thoracoscopic surgery (VATS). VATS was also used to establish suitable pleural drainage prior to elective thoracotomy (2 cases). Decortication and partial parietal pleurectomy were performed for organizing-stage empyema (16 cases). Three of the 15 patients with post-thoracotomy empyema died perioperatively, one died two months postoperatively and one had recurrence of bronchopleural fistula during follow-up. One patient with VATS debridement subsequently required thoracotomy and lobectomy for lung abscess. All the others with VATS or decortication recovered without complications. During follow-up there was no mortality or recurrence of empyema.     

Management of multiloculated empyema thoracis in children: thoracotomy versus fibrinolytic treatment.

OBJECTIVE: Progression of empyema, with the development of fibrinous adhesions and loculations, makes simple drainage difficult or impossible. The appropriate management remains controversial. Intrapleural fibrinolytic treatment to facilitate drainage of loculated empyema instead of open thoracotomy has been advocated recently. The aim of this study was to evaluate the effectiveness of the intrapleural fibrinolytic application. METHODS: In our clinic we used urokinase in 28 patients and performed thoracotomy and decortication in another 43. The two groups of patients had similar characteristics. Mean age was 10.2 (range: 3-14 years). All had undergone medical treatment and tube thoracostomy. Empyema severity score (ESS) was measured in all. RESULTS: Fibrinolytic treatment, and thoracotomy and decortication had complete response rates of 67.8 and 100%, respectively. Treatment was ineffective in six (21.4%) out of 28 patients who underwent urokinase instillation; they recovered after thoracotomy. In three (10.7%) patients, partial resolution was observed. One patient died of sepsis and pleural hemorrhage. Mean hospital stay after urokinase was 10.7 (range: 6-17) days. In the thoracotomy group, all patients recovered completely. No deaths occurred. Postoperative complications were incisional infection in two patients, atelectasis in one and reoperation after hemorrhage in one. Mean hospital stay after surgery was 9.5 (5-19) days. The ESS of cases operated on was lower postoperatively (0.3 versus 0.8). CONCLUSION: Continued conservative therapy risks morbidity and mortality. Thoracotomy-decortication can be used successfully and must remain the preferred method in the treatment of multiloculated pediatric empyema.     

Video-Assisted Thoracoscopic Surgery in the Management of Pediatric Empyema

Background:

Management of empyema in children has progressed from open thoracotomy to video-assisted thoracoscopic surgery (VATS). The purpose of the present study was to evaluate the efficacy and safety of VATS in children with multiloculated empyemas.

Methods:

Nine children (mean age, 4 years; range, 21 months to 13 years) with empyema, in whom multiple loculations were found on computed tomography, were treated with VATS from January, 1994, to November, 1996. All patients underwent VATS under general anesthesia, with drainage of the empyemas, decortication, and placement of chest tubes under direct vision.

Results:

In all nine patients, VATS was successful. Average operating time was 120 minutes. Blood loss was insignificant, except in one patient who needed an intraoperative blood transfusion. This child required extensive decortication, with blood oozing from raw areas. All patients recovered well, with no recurrences to date. An algorithm for the use of VATS in the treatment plan for children with empyema was established.

Conclusion:

VATS provides safe and effective treatment in the management of pediatric empyema. Moreover, it avoids lengthy hospitalization, prolonged intravenous antibiotic therapy, and unnecessary pain and stress secondary to placement of chest tubes without anesthesia.     

电视胸腔镜在脓胸治疗中的应用体会

目的探讨胸腔镜在脓胸治疗中的价值。方法 2002年1月至2011年11月对98例确诊脓胸在胸腔镜下清理和刮除脓苔,剥离纤维膜;对病程稍长,纤维粘连不易剥离者,胸腔镜辅助下小切口,术后彻底冲洗脓腔。结果 71例胸腔镜手术,18例辅助小切口手术,9例中转开胸手术。手术时间50～180min,平均80min;胸腔引流3～35d,平均12d。出院前胸片复查肺复张良好,无脓胸复发及并发症。结论胸腔镜手术或辅助小切口手术治疗脓胸安全、有效、微创。能达到清除病因、闭合脓腔、恢复肺功能的目的 ,特别是对病程较长、心肺功能差的患者尤为适合。     

Surgical treatment of metapneumonic pleural empyema

During a period of 13 years 54 patients have been treated for metapneumonic pleural empyema, namely 3 children (all boys), 31 men and 20 women. One patient was admitted in extremis heavily intoxicated after unsuccessful attempt at closed drainage. He died during thoracotomy for open drainage. All the remaining 53 patients were cured, 3 out of 18 by closed thoracostomy (Bülau), 12 out of 16 by open drainage and 37 by decortication which had to be combined with pulmonary resection 13 times. Local treatment of pleural empyema is aimed at the obliteration of the pleural space. This goal can best be accomplished: in the acute exudative stage of the disease (according to the American Thoracic Society) by closed thoracotomy, in the fibrino-purulent phase by open thoracotomy with rib resection and in the chronic organizing stage by decortication.     

Efficacy of primary and secondary video-assisted thoracic surgery in children

BACKGROUND/PURPOSE: Video-assisted thoracic surgery (VATS) is used commonly for diagnostic and therapeutic procedures in children. The purpose of this study was to determine the accuracy, efficacy, and complications associated with primary and secondary VATS in children. METHODS: Eighty-seven infants, children, and adolescents underwent 104 VATS procedures between March 1993 and April 1999. There were 47 boys and 40 girls with an age range of 6 months to 19 years. VATS was performed for excision of pulmonary nodule (n = 51), biopsy of infiltrate (n = 14), excision or biopsy mediastinal mass (n = 12), decortication of empyema (n = 16), pleurodesis and bleb excision for pneumothorax (n = 5), pleurolysis for P32 administration (n = 3), esophageal myotomy (n = 2), and thymectomy (n = 1). In 6 children a contralateral thoracic procedure was performed along with VATS (3 VATS, 3 thoracotomies). Secondary VATS was performed in 20 after prior thoracic procedures. RESULTS: VATS was efficacious for diagnostic or therapeutic purposes in 93 cases. Overall, 11 (11%) VATS required conversion to open thoracotomy. Average length of thoracostomy tube drainage (CTD) was 2.2 days, and average length of stay (LOS) was 3.7 days. Complications included prolonged air leak (> 7 days) in 3 (2 empyema, 1 nodule). Two children with malignancy and pulmonary infiltrates died within 30 days of progressive respiratory failure. There were no bleeding complications or deaths related to VATS. CONCLUSIONS:VATS is a safe and effective primary and secondary procedure in children resulting in a short length of CTD and LOS. Duration of CTD and LOS are prolonged if empyema is associated with a bronchopleural fistula, and VATS may not be of value in this setting.     

Outcomes of Video-Assisted Thoracic Surgical Decortication in 274 Patients with Tuberculous Empyema

Objective: The present work aimed to retrospectively assess the outcomes associated with decortication by video-assisted thoracic surgery (VATS) in patients with tuberculous empyema.Methods: Patients (n = 274) who underwent decortication by VATS for surgical management of pleural empyema between January 2000 to 2010 were included. Pre-, intra-, and post-operative characteristics were observed for all patients, which were followed up for 12 months to evaluate surgical outcomes such as postoperative complications and disease recurrence.Results: No patients required conversion to thoracotomy, and no death or postoperative bleeding was reported. The mean operation time was 104.5 ± 20.4 min, with 271.5 ± 41.3 ml intraoperative blood loss and median length of hospital stay of 7.2 ± 3.4 days. Of the 274 patients, 262 were followed up for 12 months; 26 (9.9%) patients showed complications, including incomplete lung re-expansion (11 patients) and persistent air leak (6 patients). While early disease recurrence was observed in 3 (1.1%) patients after surgery, late recurrence was reported for 6 (2.3%) individuals. Interestingly, the complication rate was much higher in patients with chronic empyema (15/34, 44.1%) than in subjects with acute empyema (11/228, 4.8%).Conclusions: Decortication by VATS decreases postsurgical complications, and results in decreased disease recurrence. This study demonstrated improved outcomes by decortication by VATS, even in patients with stage III tuberculous empyema.