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Acta Radiol OnlineFirst, published on October 2, 2014 as doi:10.1177/0284185114551399
Original Article
Pneumomediastinum and pneumoperitoneum on computed tomography after peroral endoscopic myotomy (POEM): postoperative changes or complications?
Acta Radiologica 0(0) 1–6 ! The Foundation Acta Radiologica 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0284185114551399 acr.sagepub.com
Shan Yang, Meng-su Zeng, Zhi-yong Zhang, Hao-ling Zhang, Liang Liang and Xing-wei Zhang
Abstract Background: Many of the acute alterations after peroral endoscopic myotomy (POEM) may be of little clinical significance, while others may herald major clinical problems. The question whether pneumomediastinum/pneumoperitoneum is a normal postoperative finding after POEM, or should be regarded as a sign of a complication needs to be evaluated. Familiarity with these findings in computed tomography (CT) is essential for radiologists. Purpose: To evaluate whether or not pneumomediastinum/pneumoperitoneum detected by chest CT is a sign of a complication after POEM using CO2 insufflation for esophageal achalasia. Material and Methods: One hundred and eight patients with esophageal achalasia who underwent chest CT within 30 hours after POEM were included. CT findings were retrospectively reviewed by two radiologists in consensus. The correlation between pneumomediastinum and/or pneumoperitoneum shown on CT and the development of complications was analyzed. Results: Abnormal findings were identified on post-treatment CT, including pneumomediastinum and/or pneumoperitoneum (53.7%, 58/108), pneumothorax (0.9%, 1/108), subcutaneous emphysema (29.6%, 32/108), pleural effusion (69.4%, 75/108), segmental atelectasis of lung tissue (29.6%, 32/108), minor inflammation of lungs (69.4%, 75/108), and ascites (0.9%, 1/108). Pneumomediastinum and pneumoperitoneum were observed simultaneously in 29 cases. The incidence rate of mild complications was high (79.6%, 86/108), while the rate of severe complications was low (2.8%, 3/108). There was no significant correlation between the occurrence of pneumomediastinum and/or pneumoperitoneum on CT and the development of complications (P ¼ 0.542), or the development of severe complications including delayed hemorrhage, esophageal perforation, and retroperitoneal abscess. Conclusion: Pneumomediastinum and pneumoperitoneum detected by CT occur frequently after POEM and may be regarded as normal postoperative changes.
Keywords Esophageal achalasia, peroral endoscopic myotomy (POEM), Computed tomography (CT), X-ray, complications Date received: 25 March 2014; accepted: 24 August 2014
Introduction Esophageal achalasia (EA) is a relatively rare neurodegenerative motility disorder of the esophagus, which results in deranged esophageal peristalsis and loss of lower esophageal sphincter function (1). Various treatments, such as laparoscopic Heller’s myotomy, endoscopic pneumatic balloon dilation, and peroral
Department of Radiology, Zhongshan Hospital, Fudan University; Shanghai Institute of Medical Imaging; Department of Medical Imaging, Shanghai Medical College, Fudan Unversity, Shanghai, PR China Corresponding author: Xing-wei Zhang, Department of Radiology, Zhongshan Hospital, Fudan University, 180 Fenglin Road, Xuhui District, Shanghai 200032, PR China. Email: [email protected]
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endoscopic myotomy (POEM) are available. POEM is a novel and promising therapeutic approach for EA, which was first reported by Pasricha et al. (2) in porcine models and then by Inoue et al. (3) in humans. The technique of POEM is centered on the creation of a submucosal tunnel within the distal esophagus where a myotomy is performed within this tunnel with dissection of the inner circular muscle of the esophagus and minimally dissection of the lower esophageal sphincter (LES) circular muscle (4). Previous studies showed that POEM was a feasible, safe, and effective treatment for EA (5–7). However, the safety profile of this newly developed procedure has received concerns. Some complications may occur during or after the POEM (8). Computed tomography (CT) scan obtained after POEM may show normal alterations resulting from the endosurgical procedure. Many of the acute alterations may be of little clinical significance, while others may herald major clinical problems. Therefore, familiarity with the CT findings of expected changes as well as the possible complications after POEM is essential for radiologists. Inoue et al. (3) reported that CT scans performed immediately after POEM revealed a small amount of carbon dioxide (CO2) deposited in the paraesophageal mediastinum in all the patients, without apparent clinical effect in any case, and neither did symptoms appear in the later follow-up. Von Renteln et al. (5) also reported that the occurrence of pneumoperitoneum and subcutaneous emphysema was not associated with any infectious complications such as mediastinitis and peritonitis. However, Ren et al. (8) suggested that complications developed during or after POEM should be treated promptly and could be resolved with traditional treatment. In this particular study, the cause of these complications might be due to the use of room air instead of CO2 during the procedure, because CO2 is more easily absorbed, and is 20 times more soluble than room air in serum. Pneumoperitoneum was reported to be a postoperative alteration after laparoscopic surgery with CO2 insufflation (9–11), and pneumomediastinum was also clinically silent after esophageal endoscopic submucosal dissection with CO2 insufflation (12). This promoted us to evaluate whether or not pneumomediastinum and pneumoperitoneum were postoperative changes after POEM using CO2 insufflation. Thus, our aim was to assess whether pneumomediastinum/pneumoperitoneum after POEM detected by chest CT is a sign of a complication.
Material and Methods Patients This retrospective study was approved by the institutional review board, and informed consent was waived. This study retrospectively evaluated chest CT images of 108
consecutive patients who underwent POEM at our institution between February 2012 and July 2013. Inclusion criteria consisted of: (i) clinically proven esophageal achalasia; (ii) availability of chest CT data obtained within 30 h after POEM; (iii) POEM procedure with CO2 insufflation. Clinical data were collected from medical records. After the operation, all patients were fasted, remaining in a semi-recumbent position, monitored by electrocardiograph (ECG) for vital signs, and given oxygen, antibiotics (third-generation cephalosporins plus ornidazole) and a proton pump inhibitor (PPI). On the third day after the operation, a liquid diet was allowed.
CT acquisition All non-contrast chest CT examinations were performed on either a 16-slice CT scanner (49/108, 45.4%) (Siemens Somatom Sensation16, Siemens AG, Erlangen, Germany), or a 64-slice CT scanner (59/108, 54.6%) (LightSpeed VCT 64; GE Healthcare, Milwaukee, WI, USA). Multi-slice CT parameters included 0.75-mm collimation for the 16-slice CT and 0.625-mm collimation for the 64-slice CT. The CT dataset was reconstructed at a section thickness of 5 mm for both CT instruments. The cranial to caudal range of CT acquisitions was from the lung apices to the level of diaphragm. All CT images were evaluated by two radiologists, who had 10 and 20 years of chest imaging experience and were blinded to clinical data. They reviewed CT images together and recorded findings in consensus. Pneumomediastinum/pneumoperitoneum was graded into four categories: Grade 0, no pneumomediastium/ pneumoperitoneum; Grade I (Fig. 1a and b), a small amount of bubbles in mediastinum or peritoneal cavity; Grade II (Fig. 1c and d), moderate free air around great vessels and heart, or showing thin crescents of radiolucent air in peritoneal cavity; Grade III (Fig. 1e and f), diffuse free air extending around the heart and/or beyond the mediastinum into the neck; and/or a large amount of free air in peritoneal cavity, strikingly outlining the masses of liver and/or spleen. Other abnormal CT findings were also recorded. The complications were classified into two categories: (i) mild, only requiring conservative treatment and with any of the following abnormal findings on the postoperative chest CT: pneumothorax, minor inflammation of the lungs, pleural effusion, subcutaneous emphysema, segmental atelectasis of lungs, or ascites; (ii) severe, requiring special treatment such as endoscopic, radiological, or surgical intervention or hospitalization >10 days with pharmacological treatment.
Statistical analysis Baseline characteristics of patients were expressed as mean, standard deviation (SD), and proportion. The correlation
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Fig. 1. CT grade of the pneumomediastium and pneumoperitoneum. Grade I (a, b): bubbles in mediastinum (black arrow) and peritoneal cavity (white arrow). Grade II (c, d): localized (black arrows) and thin crescents (white arrows). Grade III (e, f): diffuse free air in mediastinum (black arrows) and the peritoneal cavity (white arrows).
between pneumomediastinum and/or pneumoperitoneum showed on CT and the development of complications was assessed by chi-squared test. Statistical analysis was performed using SPSS (version 19.0, SPSS Inc., Chicago, IL, USA). The difference with a P value of less than 0.05 was considered statistically significant.
Results Among the 108 patients included, 52 were men and 56 were women, with a mean age of 40.5 years (median age, 37 years; range, 21–73 years). Six patients (5.6%)
had received drug treatment (e.g. nifedipine, and traditional Chinese medicine), eight (6.1%) had received a botulinum toxin injection, two (1.9%) had received stent treatment, 16 (14.8%) had received balloon dilation, and five (4.6%) had undergone thoracoscopic Heller surgery. All patients underwent a chest CT scan on the first day after POEM (median, 22 h; range, 16–30 h). Abnormal findings were identified on posttreatment CT, including pneumomediastinum (37.0%, 40/108), pneumoperitoneum (43.5%, 47/108), pneumothorax (0.9%,1/108), subcutaneous emphysema (29.6%,32/108), pleural effusion (69.4%, 75/108),
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segmental atelectasis of lungs (29.6%, 32/108), minor inflammation of lungs (67.5%, 73/108), and ascites (0.9%,1/108). Twenty-nine cases showed pneumomediastinum and pneumoperitoneum simultaneously. Overall, pneumomediastinum and/or pneumoperitoneum were detected in 53.7% (58/108) of the cases. As for the grades of pneumomediastinum/pneumoperitoneum on CT, the proportions of grades 0, I, II, and III were 46.3% (50/108), 38.9% (42/108), 7.4% (8/108), and 7.4% (8/108), respectively. The mean length of hospitalization was 4.3 3.3 days. All patients stayed in hospital for less than 10 days except three patients with severe complications. Eighty-six patients had mild complications, while three patients had severe complications. One patient had delayed hemorrhage on the first day after surgery and suddenly vomited about 15 mL of fresh blood. An emergency gastroscopy was immediately performed and successful hemostasis was achieved by thermocoagulation. Another patient was diagnosed with esophageal perforation and was treated endoscopically by applying metal clips for closure of the perforation and drainage for pleural effusion. In addition, one patient developed a retroperitoneal abscess with ascites, and was treated with drainage of the retroperitoneal abscess under ultrasonography guidance and administration of antibiotics. No mortality was registered. There was no statistically significant relationship between the presence of pneumomediastinum and/or pneumoperitoneum on CT and the development of complications (P ¼ 0.542, Table 1). The CT findings of three cases with severe complications are shown in Table 2 and Figs 2 and 3. There was no trend that pneumomediastinum and/or pneumoperitoneum correlated with severe complications.
Discussion The goal of our study was to evaluate the clinical significance of pneumomediastinum and pneumoperitoneum detected by chest CT examination immediately after POEM treatment for EA using CO2 insufflation.
Table 1. Correlation between the occurrence of pneumomediastinum and/or pneumoperitoneum on CT and the development of complications. PM and/or PP on CT Complications
Absence (n ¼ 50) Presence (n ¼ 58) P value
Absence (n ¼ 19) 10 Presence (n ¼ 89) 40
9 49
0.542
Complications: including mild and sever complications. PM, pneumomediastinum; PP, pneumoperitoneum.
Our study showed that the incidence rate of pneumomediastinum and/or pneumoperitoneum on post-treatment chest CT was relatively high (53.7%, 58/108), while severe complications occurred only in three cases (2.8%, 3/108). The most serious complication of endoscopic treatment for esophageal disease is iatrogenic perforation, which results in mediastinitis (13). The therapeutic approach and prognosis of perforation generally depend on the length of time between the event and the diagnosis, the size and characteristics of the perforation, and the presence of underlying diseases. Previous studies demonstrated that CT examination enabled accurate and timely diagnosis of perforation, which significantly improved prognosis and provided valuable indications for treatment (14, 15). White et al. (16) reported that extra-esophageal air was the most useful CT finding for diagnosis of esophageal perforation. However, previous studies on esophageal endoscopic submucosal dissection for esophageal carcinoma, indicated that pneumomediastinum detected by chest CT did not cause clinically significant complications (12,17,18). In the current study, we found that the incidence rate of pneumomediastinum and/or pneumoperitoneum after POEM was 53.7% (58/108), but only one of these cases had esophageal perforation. This might be explained by the insufflation of CO2 into the mediastinum and/or abdomen during submucosal tunnel dissection and myotomy. The muscle fibers and the adventitia do not represent a resistant barrier to CO2, which quickly diffuses into the mediastinum and/or abdomen. Therefore, pneumomediastinum and/or pneumoperitoneum are usually not clinically relevant and do not represent a real problem for the health of the patients. This event is usually self-limiting because CO2 is reabsorbed spontaneously after the operation. Our study also showed that there was no significant correlation between the occurrence of pneumomediastinum and/or pneumoperitoneum and the development of complications. In addition, other abnormal CT findings did not correlate with the presence of pneumomediastinum and/or pneumoperitoneum. Thus, self-limited pneumomediastinum and pneumoperitoneum shown on CT do not need to be treated specially and are of limited clinical significance. Millitz et al. (9) demonstrated that pneumoperitoneum resolved in most patients within the first week after laparoscopic cholecystectomy, as it was detected on upright chest radiographs. However, Gayer et al. (19) reported that pneumoperitoneum was present on CT up to 18 days after abdominal surgery, with a diminished volume of free air as time progressed. So we could assume that pneumomediastinum and pneumoperitoneum should still be present had the CT examination been repeated. However, previous studies
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Table 2. CT findings in three cases with severe complications.
Esophageal perforation Retroperitoneal abscess Hemorrhage
Pneumomediastinum
Pneumoperitoneum
Effusion
Ascites
Pneumonia
Grade I Grade II Grade I
Grade I Grade II /
Moderate (right) Mild (bilateral) Mild (bilateral)
/ Moderate /
/ Mild (bilateral) /
Grade I, a small amount of bubbles in mediastinum and/or abdomen; Grade II, a moderate amount of free air in mediastinum and/or abdomen.
Fig. 2. Esophageal perforation. Follow-up chest CT scan on the first day after POEM in a 55-year-old man with persistent high fever shows bubbles around esophagus (grade I), esophageal wall swelling, partial passive atelectasis of right lower lobe and moderate right pleural effusion (a). Esophageal lumen enlargement became remarkable and new left pleural effusion occurred on the sixth day after POEM (b). The esophageal perforation was proved by endoscopy and treated with endoscopic application of metal clips for closure. Esophageal lumen enlargement and pleural effusion diminished 2 weeks after POEM (c).
reported that a repeated CT examination was not deemed necessary when the clinical conditions of patients improved (9–12,17–19). In our study, there was no trend that pneumomediastinum and/or pneumoperitoneum correlated with severe complications. Interestingly, we identified some CT signs that were related to severe complications. Although the group with severe complications is too small to draw a meaningful conclusion, there are some abnormal findings may indicate severe complications after POEM.
Specifically, moderate pleural effusion and moderate ascites might have predictive value for severe complications after POEM. For radiologists, familiarity with these CT findings is important because they are often the first indications of severe complications, especially in the early postoperative period. The present study has some limitations. First, our study could not avoid sampling bias due to its retrospective nature. Second, some groups had small sample sizes, especially there were only three cases with severe
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Fig. 3. Retroperitoneal abscess. Abdominal CT on the 10th day after POEM in a 41-year-old male patient revealed an abscess (arrows) in the right retroperitoneum. The abscess contained fluid and gas (arrowhead).
complications. Third, we evaluated the free air only in the upper abdomen with chest CT instead of the entire peritoneal cavity. Finally, we only focused on special interventions for complications, and did not examine whether information from the chest CT was correlated with other care provided, for example the intensity of further imaging or laboratory diagnostics, or at the level of care in hospital. In conclusion, pneumomediastinum and/or pneumoperitoneum detected by CT (53.7%) after POEM is common and should not be considered as signs of complications. Moderate pleural effusion or ascites might be predictive findings for severe complications. Acknowledgements The authors would like to thank Pinghong Zhou for data management and performing the peroral endoscopic myotomy for this study.
Conflict of interest None declared.
Funding This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
References 1. O’Neill OM, Johnston BT, Coleman HG. Achalasia: a review of clinical diagnosis, epidemiology, treatment and outcomes. World J Gastroenterol 2013;19:5806–5812. 2. Pasricha PJ, Hawari R, Ahmed I, et al. Submucosal endoscopic esophageal myotomy: a novel experimental approach for the treatment of achalasia. Endoscopy 2007;39:761–764. 3. Inoue H, Minami H, Kobayashi Y, et al. Peroral endoscopic myotomy (POEM) for esophageal achalasia. Endoscopy 2010;42:265–271.
4. Friedel D, Modayil R, Iqbal S, et al. Per-oral endoscopic myotomy for achalasia: An American perspective. World J Gastrointest Endosc 2013;5:420–427. 5. Von Renteln D, Fuchs KH, Fockens P, et al. Peroral endoscopic myotomy for the treatment of achalasia: an international prospective multicenter study. Gastroenterology 2013;145:309–311. 6. Zhou PH, Li QL, Yao LQ, et al. Peroral endoscopic remyotomy for failed Heller myotomy: a prospective single-center study. Endoscopy 2013;45:161–166. 7. Swanstrom LL, Kurian A, Dunst CM, et al. Long-term outcomes of an endoscopic myotomy for achalasia: the POEM procedure. Ann Surg 2012;256:659–667. 8. Ren Z, Zhong Y, Zhou P, et al. Perioperative management and treatment for complications during and after peroral endoscopic myotomy (POEM) for esophageal achalasia (EA) (data from 119 cases). Surg Endosc 2012;26:3267–3272. 9. Millitz K, Moote DJ, Sparrow RK, et al. Pneumoperitoneum after laparoscopic cholecystectomy: frequency and duration as seen on upright chest radiographs. Am J Roentgenol 1994;163:837–839. 10. Hope WW, Heniford BT, Norton HJ, et al. Duration and clinical significance of radiographically detected ‘‘free air’’ after laparoscopic nephrectomy. Surg Laparosc Endosc Percutan Tech 2009;19:415–418. 11. Watari J, Tomita T, Toyoshima F, et al. The incidence of ‘‘silent’’ free air and aspiration pneumonia detected by CT after gastric endoscopic submucosal dissection. Gastrointest Endosc 2012;76:1116–1123. 12. Maeda Y, Hirasawa D, Fujita N, et al. A pilot study to assess mediastinal emphysema after esophageal endoscopic submucosal dissection with carbon dioxide insufflation. Endoscopy 2012;44:565–571. 13. Shimizu Y, Kato M, Yamamoto J, et al. Endoscopic clip application for closure of esophageal perforations caused by EMR. Gastrointest Endosc 2004;60:636–639. 14. De Lutio di Castelguidone E, Pinto A, Merola S, et al. Role of spiral and multislice computed tomography in the evaluation of traumatic and spontaneous oesophageal perforation. Our experience. Radiol Med 2005;109:252–259. 15. Wu CH, Chen CM, Chen CC, et al. Esophagography after pneumomediastinum without CT findings of esophageal perforation: is it necessary? Am J Roentgenol 2013; 201:977–984. 16. White CS, Templeton PA, Attar S. Esophageal perforation: CT findings. Am J Roentgenol 1993;160:767–770. 17. Tamiya Y, Nakahara K, Kominato K, et al. Pneumomediastinum is a frequent but minor complication during esophageal endoscopic submucosal dissection. Endoscopy 2010;42:8–14. 18. Maeda Y, Hirasawa D, Fujita N, et al. Mediastinal emphysema after esophageal endoscopic submucosal dissection: its prevalence and clinical significance. Dig Endosc 2011;23:221–226. 19. Gayer G, Jonas T, Apter S, et al. Postoperative pneumoperitoneum as detected by CT: prevalence, duration, and relevant factors affecting its possible significance. Abdom Imaging 2000;25:301–305.
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Acta Radiol OnlineFirst, published on October 2, 2014 as doi:10.1177/0284185114551399
Original Article
Pneumomediastinum and pneumoperitoneum on computed tomography after peroral endoscopic myotomy (POEM): postoperative changes or complications?
Acta Radiologica 0(0) 1–6 ! The Foundation Acta Radiologica 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0284185114551399 acr.sagepub.com
Shan Yang, Meng-su Zeng, Zhi-yong Zhang, Hao-ling Zhang, Liang Liang and Xing-wei Zhang
Abstract Background: Many of the acute alterations after peroral endoscopic myotomy (POEM) may be of little clinical significance, while others may herald major clinical problems. The question whether pneumomediastinum/pneumoperitoneum is a normal postoperative finding after POEM, or should be regarded as a sign of a complication needs to be evaluated. Familiarity with these findings in computed tomography (CT) is essential for radiologists. Purpose: To evaluate whether or not pneumomediastinum/pneumoperitoneum detected by chest CT is a sign of a complication after POEM using CO2 insufflation for esophageal achalasia. Material and Methods: One hundred and eight patients with esophageal achalasia who underwent chest CT within 30 hours after POEM were included. CT findings were retrospectively reviewed by two radiologists in consensus. The correlation between pneumomediastinum and/or pneumoperitoneum shown on CT and the development of complications was analyzed. Results: Abnormal findings were identified on post-treatment CT, including pneumomediastinum and/or pneumoperitoneum (53.7%, 58/108), pneumothorax (0.9%, 1/108), subcutaneous emphysema (29.6%, 32/108), pleural effusion (69.4%, 75/108), segmental atelectasis of lung tissue (29.6%, 32/108), minor inflammation of lungs (69.4%, 75/108), and ascites (0.9%, 1/108). Pneumomediastinum and pneumoperitoneum were observed simultaneously in 29 cases. The incidence rate of mild complications was high (79.6%, 86/108), while the rate of severe complications was low (2.8%, 3/108). There was no significant correlation between the occurrence of pneumomediastinum and/or pneumoperitoneum on CT and the development of complications (P ¼ 0.542), or the development of severe complications including delayed hemorrhage, esophageal perforation, and retroperitoneal abscess. Conclusion: Pneumomediastinum and pneumoperitoneum detected by CT occur frequently after POEM and may be regarded as normal postoperative changes.
Keywords Esophageal achalasia, peroral endoscopic myotomy (POEM), Computed tomography (CT), X-ray, complications Date received: 25 March 2014; accepted: 24 August 2014
Introduction Esophageal achalasia (EA) is a relatively rare neurodegenerative motility disorder of the esophagus, which results in deranged esophageal peristalsis and loss of lower esophageal sphincter function (1). Various treatments, such as laparoscopic Heller’s myotomy, endoscopic pneumatic balloon dilation, and peroral
Department of Radiology, Zhongshan Hospital, Fudan University; Shanghai Institute of Medical Imaging; Department of Medical Imaging, Shanghai Medical College, Fudan Unversity, Shanghai, PR China Corresponding author: Xing-wei Zhang, Department of Radiology, Zhongshan Hospital, Fudan University, 180 Fenglin Road, Xuhui District, Shanghai 200032, PR China. Email: [email protected]
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endoscopic myotomy (POEM) are available. POEM is a novel and promising therapeutic approach for EA, which was first reported by Pasricha et al. (2) in porcine models and then by Inoue et al. (3) in humans. The technique of POEM is centered on the creation of a submucosal tunnel within the distal esophagus where a myotomy is performed within this tunnel with dissection of the inner circular muscle of the esophagus and minimally dissection of the lower esophageal sphincter (LES) circular muscle (4). Previous studies showed that POEM was a feasible, safe, and effective treatment for EA (5–7). However, the safety profile of this newly developed procedure has received concerns. Some complications may occur during or after the POEM (8). Computed tomography (CT) scan obtained after POEM may show normal alterations resulting from the endosurgical procedure. Many of the acute alterations may be of little clinical significance, while others may herald major clinical problems. Therefore, familiarity with the CT findings of expected changes as well as the possible complications after POEM is essential for radiologists. Inoue et al. (3) reported that CT scans performed immediately after POEM revealed a small amount of carbon dioxide (CO2) deposited in the paraesophageal mediastinum in all the patients, without apparent clinical effect in any case, and neither did symptoms appear in the later follow-up. Von Renteln et al. (5) also reported that the occurrence of pneumoperitoneum and subcutaneous emphysema was not associated with any infectious complications such as mediastinitis and peritonitis. However, Ren et al. (8) suggested that complications developed during or after POEM should be treated promptly and could be resolved with traditional treatment. In this particular study, the cause of these complications might be due to the use of room air instead of CO2 during the procedure, because CO2 is more easily absorbed, and is 20 times more soluble than room air in serum. Pneumoperitoneum was reported to be a postoperative alteration after laparoscopic surgery with CO2 insufflation (9–11), and pneumomediastinum was also clinically silent after esophageal endoscopic submucosal dissection with CO2 insufflation (12). This promoted us to evaluate whether or not pneumomediastinum and pneumoperitoneum were postoperative changes after POEM using CO2 insufflation. Thus, our aim was to assess whether pneumomediastinum/pneumoperitoneum after POEM detected by chest CT is a sign of a complication.
Material and Methods Patients This retrospective study was approved by the institutional review board, and informed consent was waived. This study retrospectively evaluated chest CT images of 108
consecutive patients who underwent POEM at our institution between February 2012 and July 2013. Inclusion criteria consisted of: (i) clinically proven esophageal achalasia; (ii) availability of chest CT data obtained within 30 h after POEM; (iii) POEM procedure with CO2 insufflation. Clinical data were collected from medical records. After the operation, all patients were fasted, remaining in a semi-recumbent position, monitored by electrocardiograph (ECG) for vital signs, and given oxygen, antibiotics (third-generation cephalosporins plus ornidazole) and a proton pump inhibitor (PPI). On the third day after the operation, a liquid diet was allowed.
CT acquisition All non-contrast chest CT examinations were performed on either a 16-slice CT scanner (49/108, 45.4%) (Siemens Somatom Sensation16, Siemens AG, Erlangen, Germany), or a 64-slice CT scanner (59/108, 54.6%) (LightSpeed VCT 64; GE Healthcare, Milwaukee, WI, USA). Multi-slice CT parameters included 0.75-mm collimation for the 16-slice CT and 0.625-mm collimation for the 64-slice CT. The CT dataset was reconstructed at a section thickness of 5 mm for both CT instruments. The cranial to caudal range of CT acquisitions was from the lung apices to the level of diaphragm. All CT images were evaluated by two radiologists, who had 10 and 20 years of chest imaging experience and were blinded to clinical data. They reviewed CT images together and recorded findings in consensus. Pneumomediastinum/pneumoperitoneum was graded into four categories: Grade 0, no pneumomediastium/ pneumoperitoneum; Grade I (Fig. 1a and b), a small amount of bubbles in mediastinum or peritoneal cavity; Grade II (Fig. 1c and d), moderate free air around great vessels and heart, or showing thin crescents of radiolucent air in peritoneal cavity; Grade III (Fig. 1e and f), diffuse free air extending around the heart and/or beyond the mediastinum into the neck; and/or a large amount of free air in peritoneal cavity, strikingly outlining the masses of liver and/or spleen. Other abnormal CT findings were also recorded. The complications were classified into two categories: (i) mild, only requiring conservative treatment and with any of the following abnormal findings on the postoperative chest CT: pneumothorax, minor inflammation of the lungs, pleural effusion, subcutaneous emphysema, segmental atelectasis of lungs, or ascites; (ii) severe, requiring special treatment such as endoscopic, radiological, or surgical intervention or hospitalization >10 days with pharmacological treatment.
Statistical analysis Baseline characteristics of patients were expressed as mean, standard deviation (SD), and proportion. The correlation
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Fig. 1. CT grade of the pneumomediastium and pneumoperitoneum. Grade I (a, b): bubbles in mediastinum (black arrow) and peritoneal cavity (white arrow). Grade II (c, d): localized (black arrows) and thin crescents (white arrows). Grade III (e, f): diffuse free air in mediastinum (black arrows) and the peritoneal cavity (white arrows).
between pneumomediastinum and/or pneumoperitoneum showed on CT and the development of complications was assessed by chi-squared test. Statistical analysis was performed using SPSS (version 19.0, SPSS Inc., Chicago, IL, USA). The difference with a P value of less than 0.05 was considered statistically significant.
Results Among the 108 patients included, 52 were men and 56 were women, with a mean age of 40.5 years (median age, 37 years; range, 21–73 years). Six patients (5.6%)
had received drug treatment (e.g. nifedipine, and traditional Chinese medicine), eight (6.1%) had received a botulinum toxin injection, two (1.9%) had received stent treatment, 16 (14.8%) had received balloon dilation, and five (4.6%) had undergone thoracoscopic Heller surgery. All patients underwent a chest CT scan on the first day after POEM (median, 22 h; range, 16–30 h). Abnormal findings were identified on posttreatment CT, including pneumomediastinum (37.0%, 40/108), pneumoperitoneum (43.5%, 47/108), pneumothorax (0.9%,1/108), subcutaneous emphysema (29.6%,32/108), pleural effusion (69.4%, 75/108),
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segmental atelectasis of lungs (29.6%, 32/108), minor inflammation of lungs (67.5%, 73/108), and ascites (0.9%,1/108). Twenty-nine cases showed pneumomediastinum and pneumoperitoneum simultaneously. Overall, pneumomediastinum and/or pneumoperitoneum were detected in 53.7% (58/108) of the cases. As for the grades of pneumomediastinum/pneumoperitoneum on CT, the proportions of grades 0, I, II, and III were 46.3% (50/108), 38.9% (42/108), 7.4% (8/108), and 7.4% (8/108), respectively. The mean length of hospitalization was 4.3 3.3 days. All patients stayed in hospital for less than 10 days except three patients with severe complications. Eighty-six patients had mild complications, while three patients had severe complications. One patient had delayed hemorrhage on the first day after surgery and suddenly vomited about 15 mL of fresh blood. An emergency gastroscopy was immediately performed and successful hemostasis was achieved by thermocoagulation. Another patient was diagnosed with esophageal perforation and was treated endoscopically by applying metal clips for closure of the perforation and drainage for pleural effusion. In addition, one patient developed a retroperitoneal abscess with ascites, and was treated with drainage of the retroperitoneal abscess under ultrasonography guidance and administration of antibiotics. No mortality was registered. There was no statistically significant relationship between the presence of pneumomediastinum and/or pneumoperitoneum on CT and the development of complications (P ¼ 0.542, Table 1). The CT findings of three cases with severe complications are shown in Table 2 and Figs 2 and 3. There was no trend that pneumomediastinum and/or pneumoperitoneum correlated with severe complications.
Discussion The goal of our study was to evaluate the clinical significance of pneumomediastinum and pneumoperitoneum detected by chest CT examination immediately after POEM treatment for EA using CO2 insufflation.
Table 1. Correlation between the occurrence of pneumomediastinum and/or pneumoperitoneum on CT and the development of complications. PM and/or PP on CT Complications
Absence (n ¼ 50) Presence (n ¼ 58) P value
Absence (n ¼ 19) 10 Presence (n ¼ 89) 40
9 49
0.542
Complications: including mild and sever complications. PM, pneumomediastinum; PP, pneumoperitoneum.
Our study showed that the incidence rate of pneumomediastinum and/or pneumoperitoneum on post-treatment chest CT was relatively high (53.7%, 58/108), while severe complications occurred only in three cases (2.8%, 3/108). The most serious complication of endoscopic treatment for esophageal disease is iatrogenic perforation, which results in mediastinitis (13). The therapeutic approach and prognosis of perforation generally depend on the length of time between the event and the diagnosis, the size and characteristics of the perforation, and the presence of underlying diseases. Previous studies demonstrated that CT examination enabled accurate and timely diagnosis of perforation, which significantly improved prognosis and provided valuable indications for treatment (14, 15). White et al. (16) reported that extra-esophageal air was the most useful CT finding for diagnosis of esophageal perforation. However, previous studies on esophageal endoscopic submucosal dissection for esophageal carcinoma, indicated that pneumomediastinum detected by chest CT did not cause clinically significant complications (12,17,18). In the current study, we found that the incidence rate of pneumomediastinum and/or pneumoperitoneum after POEM was 53.7% (58/108), but only one of these cases had esophageal perforation. This might be explained by the insufflation of CO2 into the mediastinum and/or abdomen during submucosal tunnel dissection and myotomy. The muscle fibers and the adventitia do not represent a resistant barrier to CO2, which quickly diffuses into the mediastinum and/or abdomen. Therefore, pneumomediastinum and/or pneumoperitoneum are usually not clinically relevant and do not represent a real problem for the health of the patients. This event is usually self-limiting because CO2 is reabsorbed spontaneously after the operation. Our study also showed that there was no significant correlation between the occurrence of pneumomediastinum and/or pneumoperitoneum and the development of complications. In addition, other abnormal CT findings did not correlate with the presence of pneumomediastinum and/or pneumoperitoneum. Thus, self-limited pneumomediastinum and pneumoperitoneum shown on CT do not need to be treated specially and are of limited clinical significance. Millitz et al. (9) demonstrated that pneumoperitoneum resolved in most patients within the first week after laparoscopic cholecystectomy, as it was detected on upright chest radiographs. However, Gayer et al. (19) reported that pneumoperitoneum was present on CT up to 18 days after abdominal surgery, with a diminished volume of free air as time progressed. So we could assume that pneumomediastinum and pneumoperitoneum should still be present had the CT examination been repeated. However, previous studies
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Table 2. CT findings in three cases with severe complications.
Esophageal perforation Retroperitoneal abscess Hemorrhage
Pneumomediastinum
Pneumoperitoneum
Effusion
Ascites
Pneumonia
Grade I Grade II Grade I
Grade I Grade II /
Moderate (right) Mild (bilateral) Mild (bilateral)
/ Moderate /
/ Mild (bilateral) /
Grade I, a small amount of bubbles in mediastinum and/or abdomen; Grade II, a moderate amount of free air in mediastinum and/or abdomen.
Fig. 2. Esophageal perforation. Follow-up chest CT scan on the first day after POEM in a 55-year-old man with persistent high fever shows bubbles around esophagus (grade I), esophageal wall swelling, partial passive atelectasis of right lower lobe and moderate right pleural effusion (a). Esophageal lumen enlargement became remarkable and new left pleural effusion occurred on the sixth day after POEM (b). The esophageal perforation was proved by endoscopy and treated with endoscopic application of metal clips for closure. Esophageal lumen enlargement and pleural effusion diminished 2 weeks after POEM (c).
reported that a repeated CT examination was not deemed necessary when the clinical conditions of patients improved (9–12,17–19). In our study, there was no trend that pneumomediastinum and/or pneumoperitoneum correlated with severe complications. Interestingly, we identified some CT signs that were related to severe complications. Although the group with severe complications is too small to draw a meaningful conclusion, there are some abnormal findings may indicate severe complications after POEM.
Specifically, moderate pleural effusion and moderate ascites might have predictive value for severe complications after POEM. For radiologists, familiarity with these CT findings is important because they are often the first indications of severe complications, especially in the early postoperative period. The present study has some limitations. First, our study could not avoid sampling bias due to its retrospective nature. Second, some groups had small sample sizes, especially there were only three cases with severe
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Fig. 3. Retroperitoneal abscess. Abdominal CT on the 10th day after POEM in a 41-year-old male patient revealed an abscess (arrows) in the right retroperitoneum. The abscess contained fluid and gas (arrowhead).
complications. Third, we evaluated the free air only in the upper abdomen with chest CT instead of the entire peritoneal cavity. Finally, we only focused on special interventions for complications, and did not examine whether information from the chest CT was correlated with other care provided, for example the intensity of further imaging or laboratory diagnostics, or at the level of care in hospital. In conclusion, pneumomediastinum and/or pneumoperitoneum detected by CT (53.7%) after POEM is common and should not be considered as signs of complications. Moderate pleural effusion or ascites might be predictive findings for severe complications. Acknowledgements The authors would like to thank Pinghong Zhou for data management and performing the peroral endoscopic myotomy for this study.
Conflict of interest None declared.
Funding This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
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