Graham et al
. in 1948 used the term middle lobe syndrome to describe middle lobe atelectasis resulting from bronchial compression (12 patients).[3
] Anatomic characteristics, such as the narrow diameter of the lobar bronchus and an acute takeoff angle, make the right middle lobe susceptible to transient, usually partial, obstruction. Such an obstruction is considered to be the result of poor drainage of secretions due to inflammation and/or edema of the right middle lobe bronchus. In addition, the relative anatomic isolation of the middle lobe and the poor collateral ventilation decrease the chance of reinflation once atelectasis has been established. These mechanisms help to explain the vicious cycle of recurrent inflammation and obstruction that develops after repeated episodes of infection or asthma exacerbations.[1
] Subsequent reports suggest that ineffective collateral ventilation is a major factor in the pathogenesis of middle lobe syndrome.[11
] Our experience indicates that the middle lobe is prone to develop persistent total or partial atelectasis with infection. Five patients in this series had atelectasis and bronchiectasis, and infection was a manifestation of the syndrome in all patients.
Wagner and Johnston published a review of 933 cases reported in the literature. In their review, the following etiologic causes of right middle lobe syndrome were noted: Inflammation, 47%; bronchiectasis, 15%; malignant tumors, 22%; benign tumors, 2%; tuberculosis, 9%; aspiration, 2%; and miscellaneous, 3%. It was not documented whether the atelectasis was caused by active disease or nodal compression.[3
] The main bronchus to the middle lobe showed cicatricial stenosis at the point of maximum compression. This point correlated with the enlarged nodes on the external surface of the bronchus. Histological examination of the lymph nodes revealed changes only of a chronic, nonspecific lymphadenitis.[7
] We also intraoperatively saw enlarged and scarred lymph nodes around the middle lobe bronchus in most of our cases. Stenosis due to external compression was revealed in 12 patients, hyperemia and bronchitis in two patients, granulation tissue in two patients, and dense secretions in two patients.
It was previously reported that swelling of lymph nodes due to either acute or chronic inflammation narrows the bronchus, leading to further retention of bronchial secretions, atelectasis, chronic bronchitis, or bronchiectasis. Healing of these recurrent episodes by fibrosis and scarring of the lymph nodes further contributes to collapse and narrowing of the bronchial divisions.[3
] However, with repeated episodes of infection, through the resulting vicious cycle of recurring bouts of inflammation, the right middle lobe may eventually be destroyed completely.[2
The reasons for obstruction can be intraluminal or extraluminal. Although the lymph nodes are the extraluminal reason for tumors and abnormal branching, object aspiration is the intraluminal reason for granulation tissue and mucous blockage.[2
] Nonobstructive reasons were observed etiologically in most of the studies.
The existence of a nonobstructive etiology in middle lobe syndrome was especially indicated by the fact that the symptoms started in the early infantile period and decreased with age. In some series, the proportion of males was higher than that of females, whereas in other series, the opposite was found. The average age of these patients was 6.0 ± 1.1 years. The common reason in children for right middle lobe syndrome was inflammatory diseases such as bronchiectasis or pneumonia.[13
The etiology of the infection is commonly bacterial and occasionally viral, and in some cases, it is caused by tuberculosis and histoplasmosis. Two patients in this series had tuberculosis. The diagnosis was made by a smear and culture of the bronchial aspirates. The microorganisms detected are those usually isolated in children, most frequently S. pneumoniae
, followed by Haemophilus influenzae
and Staphylococcus aureus
] In our study, S. pneumoniae was isolated in frequencies that were similar to those of other studies.
Clinical application in children with middle lobe syndrome was not found to be associated with the respiratory symptoms.[8
] Conditions such as chronic cough, snuffles, dyspnea, repetitive pneumonia attacks, asthma, or atopy can be found in the anamnesis. If the nonspecific and mostly moderate respiratory symptoms of a patient were delayed with a chest graphy, it can be inadequate for diagnoses for middle lobe syndrome existing for a long time.
Posterior-anterior (PA) and lateral lung X-ray films, CT, HRCT, and bronchoscopy are used in the diagnosis.[1
] HRCT is currently the modality of choice in the diagnosis of bronchiectasis, with only a 2% false-negative rate and 1% false-positive rate.[16
] HRCT was performed in all patients in this series to document the presence of bronchiectasis. Bronchoscopy is important for diagnosis and treatment.[1
] The situation of the proximal entrance of the middle lobe can be examined by bronchoscopy. Bronchial obstruction caused by the granulation tissue, a tumor, or a foreign body can be accurately excluded. At the same time, bronchoscopy enables microbiological examination and the cleaning of remaining secretions.[17
Among the 18 patients, 66% had specific endoscopic findings of stenosis. Abnormal but nonspecific changes were present in 34% of these patients. Thus, the diagnostic yield by bronchoscopy in middle lobe syndrome appears to be almost 66%. The treatment of middle lobe syndrome is directed at the underlying cause .
CT of 6-year-old child with bronchiectasis of the middle lobe
For this purpose, antibiotic treatment, postural drainage, and bronchodilator treatment were applied, and it was suggested to avoid from allergen factors.[1
For obstructing lesions, restoration of bronchial patency may be curative. Surgery may also be indicated in patients without malignancy who have scarring, fibrosis, or abscess formation. Broncholiths and foreign objects can often be removed with flexible fiberoptic or rigid bronchoscopy.[7
] Intensive medical therapy is quite capable of resolving atelectasis and healing the patient. If endoscopic examination and CT scan did not show abnormalities after one month of the development of atelectasis, follow up with conservative treatment for another month is recommended.
If the middle lobe fails to re-expand, or recurrent atelectasis is observed, or when bronchiectasis is documented, surgical excision of the right middle lobe is indicated. Operative treatment also should be offered for patients with complete bronchial obstruction.[2
Our patients were treated medically for 4.5 years interruptedly before surgical treatment. Middle lobectomy was applied in these cases that did not respond to medical treatment for a long time, in which the middle lobe atelectasis turned chronic and aeration of lung tissue was not observed.
One patient died on postoperative day 10 due to a brain abscess. A relapse of pneumonia symptoms was not observed in any of the other patients in the postoperative follow-up.
In conclusion, middle lobe syndrome must be kept in mind for children presenting with chronic cough and repetitive pneumonia attacks and the patient must be assessed with PA and lateral lung X-ray films. It is primarily important to determine the etiologic factors carefully before starting the treatment. In middle lobe syndrome patients who have bronchiectasis, bronchial stenosis, lung re-expansion defect, despite the medical treatment, curative results can be obtained by lobectomy in the cases of recurrent symptoms.