Macklin Effect Research Articles

Blunt chest trauma with pneumomediastinum and pneumoperitoneum secondary to Macklin effect. Case report

Abstract Background Pneumomediastinum is the presence of free air around mediastinal structures, which may be spontaneous or secondary, and can occur in 10% of patients with blunt chest trauma, with the Macklin effect being its main pathophysiology. Clinical case A 21 year old male, hit by motor vehicle, with alveolopalatal fracture and blunt chest trauma, who, 72 h after admission, shows subcutaneous emphysema in the anterior chest. A simple tomography of the chest and abdomen was performed, finding a pneumomediastinum, bilateral pulmonary contusions and pneumoperitoneum. Oesophageal, tracheobronchial or intra-abdominal viscera injuries were ruled out, establishing the cause of pneumomediastinum and pneumoperitoneum due to the Macklin effect. This required conservative management in intensive care unit, with a favourable clinical course and discharged after a 10 day hospital stay. Discussion Macklin effect is caused by dissection of air medially along the bronchoalveolar sheath (interstitial emphysema), secondary to alveolar breakdown and extending into mediastinal and other anatomical structures (pneumoperitoneum). It has been documented in blunt trauma, as well as in acute asthma, positive pressure ventilation, or after Valsalva manoeuvres. The imaging method of choice is computed tomography, and its characteristic findings, interstitial emphysema adhering to a bronchus and pulmonary blood vessel. Conclusions In the presence of pneumomediastinum and pneumoperitoneum is necessary to rule out oesophageal and tracheobronchial injury before establishing the Macklin effect as its cause. The diagnosis is made with computed tomography and managed conservatively.

Spontaneous pneumomediastinum due to the Macklin effect: less is more

A 17-year-old woman presented to the Emergency Department with the abrupt onset of left hemi-facial swelling. On clinical examination, she had subcutaneous emphysema of the face, neck, and chest. She reported a prior history of asthma, without recent acute exacerbation, and she acknowledged having used cannabis and MDMA (3,4-methylenedioxy-N-methylamphetamine) a few hours before. A chest radiograph (Fig. 1a) showed diffuse subcutaneous emphysema associated with a large pneumomediastinum, consistent with the diagnosis of spontaneous pneumomediastinum due to alveolar rupture and the Macklin effect. Although there was no argument in favor of tracheal or esophageal rupture in the anamnesis, a thoracic computed tomography (CT scan) without contrast material injection was finally performed to exclude non-spontaneous pneumomediastinum (Fig. 1b–d). The CT scan confirmed the presence of diffuse pneumomediastinum with subcutaneous emphysema and air dissection into the extrapleural space of the left apex, mimicking a pneumothorax. There was no pneumothorax, rib fracture, or rupture of the trachea or esophagus. Air dissection in the central (peribronchovascular bundles) and peripheral (adjacent to the pleura) pulmonary interstitium, associated with the appearance of alveolar rupture in the middle lobe, confirmed the diagnosis of spontaneous pneumomediastinum due to alveolar rupture and the Macklin effect. The patient was afebrile with normal oxygen saturation, but had a leukocytosis (20 g/L) without elevation of the C-reactive protein (CRP). She was admitted to the thoracic surgery service for observation, and was treated with analgesics. She was discharged after a brief hospitalization of 36 h, and follow-up consultation 3 days later confirmed a marked reduction of the subcutaneous emphysema. Although spontaneous pneumomediastinum may have a striking clinical presentation, the symptoms are usually self-limited and resolve in a few days. Despite this impressive presentation, physicians should resist the temptation to over-image and hospitalize these patients, as was the case here. The Macklin effect was experimentally demonstrated by Macklin et al. in 1939. It corresponds to an alveolar rupture with air dissection along the interstitial sheaths toward the mediastinum, eventually leading to a pneumomediastinum [1]. Alveolar rupture is responsible for more than 95 % of cases of pneumomediastinum, and is more frequent than esophageal or tracheobronchial disruptions [1]. Identification of the Macklin effect on chest CT scan by visualizing air dissection along perivascular and peribronchial sheaths has been reported in 89–100 % of cases of spontaneous pneumomediastinum, but CT scan confirmation is unnecessary [1, 2]. The Macklin effect has also been implicated in 39 % of cases of pneumomediastinum following severe blunt chest trauma [3]. Spontaneous pneumomediastinum occurs predominantly in young males, and is frequently associated with respiratory diseases such as asthma and chronic obstructive pulmonary disease [2, 4]. A triggering event can be identified in 39–75 % of cases, such as an acute exacerbation of asthma, coughing, inhalation drug abuse, vomiting, physical exertion, the Valsava maneuver, or karaoke singing [2, 4, 5]. Air dissection into the pulmonary interstitium does not affect gas exchange [3]. Fever up to 38.5 C and leukocytosis with a CRP level less than 5 mg/L are & Guillaume Chassagnon gchassagnon@gmail.com

Spontaneous pneumomediastinum and Macklin effect: Overview and appearance on computed tomography.

Spontaneous pneumomediastinum (SPM) is described as free air or gas located within the mediastinum that is not associated with any noticeable cause such as chest trauma. SPM has been associated with many conditions and triggers, including bronchial asthma, diabetic ketoacidosis, forceful straining during exercise, inhalation of drugs, as well as other activities associated with the Valsalva maneuver. The Macklin effect appears on thoracic computed tomography (CT) as linear collections of air contiguous to the bronchovascular sheaths. With the recent availability of multidetector-row CT, the Macklin effect has been seen in the clinical setting more frequently than expected. The aim of this review article is to describe the CT imaging spectrum of the Macklin effect in patients with SPM, focusing on the common appearance of the Macklin effect, pneumorrhachis, and persistent SPM with pneumatocele.

Trauma-induced “Macklin effect” with pneumothorax and large pneumomediastinum, disguised by allergy

A 56-year-old man presented spontaneously to the Emergency Department complaining of facial and neck oedema after assumption of nonsteroidal anti-inflammatory drugs (NSAIDS). The triage nurse assigned the patient to Accident & Emergency (A&E) doctor as probable allergic reaction to NSAIDS. Chest X-ray (CXR), ordered after 24 hours, revealed a huge subcutaneous chest and neck emphysema without clearly visible pneumothorax. Subsequent chest CT scan showed a small left pneumothorax and a large amount of air in the mediastinum. The patient was conservatively treated since he was eupnoeic and hemodynamically stable. The pathophysiology of pneumomediastinum was first described by Macklin in 1939. The Macklin effect involves alveolar ruptures with air dissection along bronchovascular sheaths to the mediastinum. In this case the patient did not report in his history a recent blunt thoracic trauma and the initial suspicion of an allergic reaction has prevented physicians to immediately achieve the correct diagnosis.

Diagnosis and treatment of patients with spontaneous pneumomediastinum

Although many patients complaining of chest pain visit the emergency department, very few are diagnosed with spontaneous pneumomediastinum (SPM). We present the management of 20 patients with SPM. We retrospectively analyzed the clinical features, past history, chest X-rays (CXRs), 64-slice helical computed tomography (CT) images, and clinical course of 20 patients with SPM (19 men and 1 woman) who visited the emergency department of the Tokyo Metropolitan Bokutoh Hospital between 2005 and 2010. SPM predominantly resulted from physical exertion during such activities as sports and weight lifting (8 patients). The most common complaint was chest pain (15 patients), followed by dysphagia (10 patients), and dyspnea (8 patients). Subcutaneous emphysema was detected in 9 patients. The mean body mass index of the patients was 20.8±1.4kg/m(2). Although CXR findings of pneumomediastinum were absent in 5 patients, CT showed findings of the Macklin effect in all patients-interstitial gas was observed in the perihilar area in all patients and in the peripheral lung area in 9 patients (45%). Ten patients were hospitalized. The others received ambulatory care in the form of analgesics without antibiotics. All patients fully recovered without complications. Our results showed that 64-slice helical CT is more reliable than CXRs for diagnosing SPM. Moreover, some patients with SPM can be treated without hospitalization, thus decreasing medical expenses for these patients.

Pneumomediastino espontâneo (síndrome de Hamman)

A previously healthy, 21-year-old female nonsmoker sought emergency room treatment complaining of recent and progressive swelling of the face, neck, and chest (Figure 1). The patient reported no pain, dyspnea, or dysphagia at admission. She reported a brief history of odynophagia in the previous week, when, during an episode of cough, she felt intense (dissecting) retrosternal pain, which subsided within a few minutes after its onset. After that episode, she had no symptoms other than the abovementioned swelling.Physical examination revealed extensive subcutaneous emphysema, which extended from the xiphoid process to the temporal muscle and involved the entire neck and face. Pulmonary percussion and auscultation revealed no abnormalities. Cardiac auscultation revealed the presence of Hamman’s sign (crackles—as was the case in our patient—or bubbling sounds, synchronous with the heartbeat). Oral endoscopy revealed no abnormalities, and the remainder of the physical examination was normal.A CT scan of the skull, neck, and chest confirmed the presence of pneumomediastinum, pneumothorax (Figure is known as the Macklin effect or phenomenon, 2A), and extensive soft tissue emphysema in the cervical region (Figure having been named after Charles C. Macklin, 2B)—involving the face, periorbital tissues, and temporal muscles (Figure 2C)—as well as revealing the presence of pneumorrhachis (Figure in the case reported here, spontaneous 2D).From postadmission day two onward, the subcutaneous emphysema gradually improved. The patient received conservative treatment, including rest, unrestricted diet, and analgesia, if necessary. The results of routine laboratory tests, including blood workup and urinalysis, were normal. Follow-up chest X-rays revealed a sustained reduction in the abovementioned signs and symptoms. The patient remained under observation for another five days, being asymptomatic and showing nearly complete resolution of the clinical picture at discharge (Figure 1).Spontaneous pneumomediastinum, also known as Hamman’s syndrome, is defined as the presence of free air in the mediastinum, being unrelated to trauma or procedures (surgical or otherwise).

A Pneumomediastinum with Diffuse Subcutaneous Emphysema

A 65-year-old man presented to the Emergency Department with facial angioedema. It occurred just after an intramuscular morphine injection in the shoulder for a minor chest trauma from falling off a chair. On physical examination, he had right chest pain, a pulse of 90 beats/min, blood pressure of 140/80 mm Hg, respiratory rate of 35 breaths/min, and room air oxygen saturation of 88%. Diffuse wheezes were detectable in both lungs. He was provided with supplemental oxygen, salbutamol aerosol, and corticosteroid treatment. After initial stabilization, subcutaneous emphysema developed suddenly over his chest. Chest radiography revealed a right lucency, some mediastinal radiolucent streaks, and subcutaneous emphysema (Figure 1). Chest computed tomography scan with intravenous contrast confirmed the right pneumothorax and the pneumomediastinum (Figure 2, Figure 3), and revealed a rib fracture (Figure 4). A chest drain was inserted and the patient’s condition improved.Figure 2Chest computed tomography scan (tissue window). Right pneumothorax (arrow) and pneumomediastinum (arrow) are visible.View Large Image Figure ViewerDownload Hi-res image Download (PPT)Figure 3Chest computed tomography scan (tissue window) reveals right and left pneumothoraces and pneumomediastinum with dissection of bronchovascular sheaths (arrows).View Large Image Figure ViewerDownload Hi-res image Download (PPT)Figure 4Chest computed tomography scan (bone window) shows a rib fracture (arrow).Used with permission of Emilie Dehours, MD, Department of Emergency Medicine, Purpan, Toulouse, France.View Large Image Figure ViewerDownload Hi-res image Download (PPT) The term pneumothorax was first coined in 1803 by Itard, and its clinical features were described by Laennec in 1819. More than half of pneumothoraces are traumatic (accidental or iatrogenic); the others occur without any preceding trauma and are labeled spontaneous (1Schramel F.M.N.H. Postmus P.E. Vanderschueren R.G.J.R.A. Current aspects of spontaneous pneumothorax.Eur Respir J. 1997; 10: 1372-1379Crossref PubMed Scopus (257) Google Scholar). Traumatic pneumothoraces result from penetrating or nonpenetrating chest injuries (2Gupta D. Hansell A. Nichols T. et al.Epidemiology of pneumothorax in England.Thorax. 2000; 55: 666-671Crossref PubMed Scopus (259) Google Scholar). It is noteworthy that, in the literature, there is a strong association between rib fractures and pneumothoraces (3Bridges K.G. Welch G. Silver M. et al.CT detection of occult pneumothorax in multiple trauma patients.J Emerg Med. 1993; 11: 179-186Abstract Full Text PDF PubMed Scopus (90) Google Scholar). On the other hand, pneumomediastinum, reported in 1939 by Hamman, is an uncommon clinical entity (4Chalumeau M. Clainche L. Sayeg N. et al.Spontaneous pneumomediastinum in children.Pediatr Pulmunol. 2001; 31: 67-75Crossref PubMed Scopus (147) Google Scholar). The first described pneumomediastinum by Laennec in 1819 was a consequence of traumatic injury. The most widely accepted explanation for the development of pneumomediastium is a sudden rupture of distended alveoli under high-pressure gradient between the alveoli and the surrounding interstitial space. The free air then dissects from the ruptured alveoli along the bronchovascular sheaths toward the mediastinum. This sequence of events is known as the “Macklin Effect” (5Macklin M.T. Macklin C.C. Malignant interstitial emphysema of the lungs and mediastinum as an important occult complication in many respiratory diseases and other conditions.Medicine. 1994; 23: 281-352Crossref Scopus (604) Google Scholar). Gas can also escape retroperitoneally through periaortic and periesophageal planes (6Zylak C.M. Standen J.R. Barnes G.R. et al.Pneumomediastinum revisited.Radiographics. 2000; 20: 1043-1057Crossref PubMed Scopus (164) Google Scholar). As a result, the air within the mediastinum can further dissect through these planes, causing pneumopericardium, pneumoretroperitoneum, and pneumoperitoneum. As a consequence of our finding, early incorporation of a routine chest computed tomography scan in all patients with rib fractures might be required to successfully diagnose pneumothoraces and pneumomediastinum.

Letter to the Editor: MDCT features of spontaneous pneumomediatinum by Macklin effect.

Dear editor, we read with great interest the two recent case reports about pneumomediastinum: “Com-pli cated pulmonary interstitial emphysema” reported by C. Altay (JBR-BTR, 2011, 94: 84) and “Spon - taneous soccer-induced pneumo - mediastinum in a 39-year-old man” reported by K. De Smet (JBR-BTR, 2011, 346-347). We would like to widen this subject, reporting a case of massive spontaneous pneumomediastinum by Macklin effect in a 25-year-old man. High quality MDCT series, associated to scientific literature review, allow us to highlight the the CT appearance of the Macklin effect leads us to affirm the spontaneous orgin of the pneumomedia - stinum and thus permitting to be reassuring

Pneumomediastinum and Pneumoperitoneum after Blunt Chest Trauma:The Macklin Effect

Background: Pneumomediastinum creation, in blunt chest trauma, results from Mackin effect in more than 95% of cases. Objectives: In this article we report two cases of blunt chest trauma, underlining the relationship between Macklin effect, pneumomediastinum and pneumoperitoneum, and analysing conservative and invasive treatment. Case reports: We report two cases of blunt chest trauma with Pneumomediastinum creation and no evidence of airway lesions. The first patient presented with malignant pneumomediastinum, created by Macklin effect, and pneumoperitoneum with intra-abdominal hypertension. He underwent invasive treatment. The second case shows how Macklin effect can be self-limiting. This patient underwent conservative treatment. Conclusions: In any case of post-traumatic pneumomediastinum, the Macklin effect should be suspected. Clinical observation is the treatment of choice since Macklin effect is self-limiting. There are some life-threatening event, like malignant pneumomediastinum and intra-abdominal hypertension that must be relieved and treated immediately.

Cervical Soft Tissue Emphysema in Hanging—A Prospective Autopsy Study*

The underlying mechanism of cervical soft tissue emphysema (CSTE) in hanging remains unclear. The aim of this study was to determine the frequency of CSTE in cases of hanging. The sample included 83 deceased persons, average age 55.3 ± 17.9 years. CSTE was established in 44 cases. CSTE is presented as frothy air, soap bubble-like formations in superficial and/or deep connective tissue between the neck muscles up to the ligature mark, visible during gross neck examination, using special neck autopsy technique-preparation of the neck organs in layers. The interpretation of positive CSTE must be taken with caution: it could be an antemortem phenomenon possibly because of either Macklin Effect or direct or indirect trauma to the cervical airways, as well as an ante- or postmortem artifact.

Pneumomediastinum in blunt trauma: A review

Pneumomediastinum (PM) is an uncommon finding after blunt trauma to the neck or chest. Motor vehicle collisions are the most common cause in adults, while falls are the most common in children. The majority of traumatic PM results from medial tracking of air from a concomitant pneumothorax. The Macklin effect, of air tracking medially along peribronchial sheaths from alveolar rupture, is responsible for most other cases. Chest pain is the most common symptom, and crepitus the most common sign. The majority of PM will resolve spontaneously, and requires no specific intervention. Only 1—6% of cases result from rupture of the larynx, trachea, bronchi or oesophagus. Hoarseness, dyspnea, persistent lung collapse or air leak should increase suspicion for aerodigestive injury. Computed tomography (CT) can help differentiate benign etiology from those that require surgical correction. High suspicion for aerodigestive injury based on clinical and/or CT findings should prompt diagnostic bronchoscopy and/or oesophagram.

CT imaging of blunt chest trauma

BackgroundThoracic injury overall is the third most common cause of trauma following injury to the head and extremities. Thoracic trauma has a high morbidity and mortality, accounting for approximately 25% of trauma-related deaths, second only to head trauma. More than 70% of cases of blunt thoracic trauma are due to motor vehicle collisions, with the remainder caused by falls or blows from blunt objects.MethodsThe mechanisms of injury, spectrum of abnormalities and radiological findings encountered in blunt thoracic trauma are categorised into injuries of the pleural space (pneumothorax, hemothorax), the lungs (pulmonary contusion, laceration and herniation), the airways (tracheobronchial lacerations, Macklin effect), the oesophagus, the heart, the aorta, the diaphragm and the chest wall (rib, scapular, sternal fractures and sternoclavicular dislocations). The possible coexistence of multiple types of injury in a single patient is stressed, and therefore systematic exclusion after thorough investigation of all types of injury is warranted.ResultsThe superiority of CT over chest radiography in diagnosing chest trauma is well documented. Moreover, with the advent of MDCT the imaging time for trauma patients has been significantly reduced to several seconds, allowing more time for appropriate post-diagnosis care.ConclusionHigh-quality multiplanar and volumetric reformatted CT images greatly improve the detection of injuries and enhance the understanding of mechanisms of trauma-related abnormalities.

Diagnostic value of CT scan for closed chest injury

CT findings and complete clinical data of 185 cases with closed chest injuries were retrospectively analyzed.The diagnosis of 185 cases were pulmonary contusion ( n = 185 ),pulmonary laceration ( n = 35 ),Macklin effect ( n = 5 ) and lung herniation ( n = 1 ).CT findings of lung contusion appeared as thick and vagur lung marking (n =9),small points shadows (n = 12 ),blotchy shadows (n =48),small pieces shadows (n=10),ground-glass shadows (n=16),large pieces shadows (n =5),diffuse patchy clouding shadows (n = 17) or mixed lesions (n = 68).CT appearance of lung laceration included pulmonary hematomas (n = 12),cavitary lesions with air ( n = 19),cavitary lesions with air-fluid levels ( n = 53 ).Macklin effect appeared as bronchus-,pulmonary vessel-adjacent air collection and mediastinal air collection (n=5).Traumatic pulmonary hernia appeared as lung herniation through an intercostal space.Initial CT scan missed one case of pulmonary contusion and 2 cases of pulmonary laceration. Key words: Thoracic injury,closed; Tomography, X-ray computed

The Macklin effect: a frequent cause for pneumomediastinum in blunt chest trauma

纵隔积气,亦称纵隔气肿,指气体积聚于纵隔结构的周围.Macklin效应是纵隔积气的一种重要原因,文献报道较少[1-4].笔者复习了2004年6月至2009年6月广东省连平县第二人民医院240例胸部闭合性损伤的CT图像,发现Macklin效应9例,现报道如下。

Spontaneous pneumomediastinum and subcutaneous emphysema in asthma exacerbation: The Macklin effect

We describe the clinical features of a 17-year-old girl with severe asthma exacerbations. On admission to the intensive care unit, she manifested expiratory dyspnea, cyanosis, and an unproductive cough. Her chest x-rays showed extensive pneumomediastinum (PM), mild subcutaneous emphysema at the right anterior triangle of the neck, and right upper-lobe atelectasis. Her PM resulted from the "Macklin effect," which involves a three-step process: overly distended alveolar rupture, air dissection along the bronchovascular sheaths, and air spreading into the mediastinum. Treatment consisted of oxygen therapy, parenteral corticosteroids, and nebulized bronchodilators. She made a good recovery, and was discharged from the intensive care unit after 2 days. This case illustrates that conservative management strategies in this severe and unusual complication of asthma exacerbation can result in rapid and complete recovery. Nonetheless, every asthma exacerbation should be considered potentially life-threatening, and must be treated promptly and adequately.

Spontaneous pneumopericardium in acute asthma

A 14-year-old girl presented with sudden onset breathlessness associated with swelling over the face, chest and upper limbs. The breathlessness developed after a single bout of cough and progressed within a few minutes. On examination the patient was breathless with a pulse rate of 112 bpm, blood pressure of 106/76 mmHg, respiratory rate of 35 breaths/min and was afebrile. The face, chest and upper limbs were swollen and crepitus was felt on palpation. The trachea was in the midline. Air entry was reduced on the left side and diffuse wheezing was present. An immediate chest roentgenogram was done which revealed subcutaneous emphysema, mediastinal emphysema and a left pneumothorax. A lateral view revealed pneumopericardium (Fig. 1). The patient was managed conservatively with high flow oxygen, antibiotics, bronchodilators and corticosteroids. The patient improved and was discharged a week later. Fig. 1 Lateral chest x-ray showing pneumopericardium The phenomenon of pneumomediastinum (air in the mediastinum), pneumopericardium (air in the pericardium) and subcutaneous emphysema can result from many intrathoracic causes. The mechanism involves alveolar rupture secondary to raised intrathoracic pressures also called the Macklin effect [1]. Other than acute asthma, pneumopericardium can accompany a number of conditions including mechanical ventilation in neonates, thoracic trauma, following cardiac surgery, fistula formation from oesophageal or gastric ulcers, or even during labour [2]. Although chest radiography helps in the diagnosis of pneumopericardium and pneumomediastinum, computed tomography (CT) helps in confirming the presence of air [3]. Pneumopericardium is usually self-limiting but features of tamponade may necessitate pericardiocentesis. It is important that clinicians are aware of this rare but potentially fatal complication of asthma.

Macklin effect in pediatric spontaneous pneumomediastinum

Pneumomediastinum is defined as the presence of air in the mediastinum, and may be secondary to trauma or spontaneous. We present the case of a four-year old patient with a spontaneous pneumomediastinum secondary to a violent cough episode, presumably due to a simple cold. The presence of cervical pain, swelling and crepitus warned the pediatrician, who ordered the patient admission. Diagnosis was confirmed by chest and neck plane x-rays. The disorder had a short duration and favorable outcome with no specific treatment aside from symptomatic. CT scan performed at admission revealed an air migration through the perivasculobronchial sheath towards the mediastinum, the so-called "Macklin effect". This is the first description of this entity in pediatrics.

Unsuccessful resuscitation of a preterm infant due to a pneumothorax and a masked tension pneumopericardium

Pneumopericardium is the least common form of air leak in infants. A tension pneumopericardium is even more infrequent but associated with a very high mortality rate. We describe the case of an unsuccessful resuscitation in a preterm infant due to a pneumothorax and tension pneumopericardium. Despite relatively mild pressure ventilation the patient developed massive pulmonary interstitial emphysema. The extra-alveolar air spread from the interstitium towards the mediastinal space (Macklin effect) and caused a pneumothorax and pneumopericardium, which evolved towards a tension pneumopericardium after a traumatic mechanical procedure. The infant deteriorated acutely. Despite prompt pleural drainage there were no signs of recovery at any time. Postmortal examination revealed a tension pneumopericardium and massive interstitial pulmonary emphysema, which was not obvious on radiographical investigation. In cases of acute deterioration of a ventilated neonate, one should always rule out pneumothorax. If the patient does not recover after pleural drainage and cardiac resuscitation a (tension) pneumopericardium should be considered.

ABS94: The Macklin effect- case series of spontaneous pneumomediastinum

We present a case series ofspontaneous pneumomediastinum from presentation until resolution. A short review will follow to introduce the Macklin effect as a possible pathophysiology and how this understanding can help improve clinical understanding and management. Conflict of interest and funding Nil.

Frequent Cause of the Macklin Effect in Spontaneous Pneumomediastinum

The purpose of this study was to evaluate the Macklin effect in patients with spontaneous pneumomediastinum by multidetector-row computed tomography (MDCT). Chest computed tomography (CT) reports between July 2000 and January 2003 at our institution were retrospectively reviewed. Nine patients with spontaneous pneumomediastinum were identified, and their CT scans were evaluated to detect the Macklin effect. The patient diagnoses included interstitial lung diseases (n=4), bronchiolitis obliterans organizing pneumonia or pneumonia (n=3), asthma (n=1), and spontaneous pneumomediastinum without definite pulmonary disease (n=1). The Macklin effect was observed in 8 (89%) of 9 patients. In 4 patients, the Macklin effect was observed in perihilar and peripheral areas, and in 4 patients, it was observed only in the perihilar area. The Macklin effect can frequently be demonstrated in patients with spontaneous pneumomediastinum of nontraumatic respiratory causes by MDCT. A CT-proven Macklin effect may be useful in differentiating respiratory from other causes of pneumomediastinum.