AUTHOR AND EDITOR INFORMATION

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• Clinical
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• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
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• References

INTRODUCTION

Section 2 of 11  

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• Clinical
• Differentials
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• Medication
• Follow-up
• Miscellaneous
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Background

Right middle lobe syndrome (RMLS) generally refers to atelectasis in the right middle lobe of the lung. It is caused by various etiologies and has no consistent clinical definition. RMLS is characterized by a wedge-shaped density that extends anteriorly and inferiorly from the hilum of the lung, which is best visualized using lateral chest radiography. This condition is most common in children with a history of asthma or atopy. Although the mechanism by which asthma leads to lobar atelectasis is unknown, associated inflammation, bronchospasm, and secretions that cause mucus plugging are probably major contributors. Management is determined by etiology, and most patients respond to medical therapy alone.

Pathophysiology

Certain anatomical characteristics make the right middle lobe susceptible to transient obstruction as a result of inflammation or edema. The narrow diameter of the lobar bronchus and acute take-off angle create poor conditions for drainage. Relative anatomical isolation of the middle lobe and poor collateral ventilation decrease the chance of reinflation once atelectasis occurs. Bronchial obstruction can result from extrinsic compression as in hilar lymphadenopathy or tumor of neoplastic origin; however, atelectasis in children usually results from a process such as asthma-associated edema and inflammation. Foreign body aspiration into the right middle lobe orifice can also predispose to collapse of the lobe.

Frequency

United States

The precise incidence in children is unknown. RMLS is widely underdiagnosed and frequently unrecognized.

Mortality/Morbidity

Severity in children ranges from mild atelectasis and scarring of no consequence to severe bronchiectasis requiring surgical resection.

Sex

RMLS has been said to occur twice as often in girls than in boys; however, large epidemiologic studies are lacking.

Age

Symptoms begin in early childhood, usually in children aged 1-2 years. Symptom frequency decreases in later childhood, but the interval between onset of symptoms and diagnosis widely varies.

CLINICAL

Section 3 of 11  

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History

• The most common symptoms include the following:
• • Persistent or recurrent cough
  • Intermittent wheezing
  • Dyspnea
  • History of recurrent or chronic pneumonia (May often be a misinterpretation of the radiographic findings)
• In many cases, these respiratory symptoms are refractory to normal treatment.
• At least half of the patients report a history of asthma or atopy, and one third report a family history of atopy.
• Less frequently reported symptoms, which may be indicative of chronic disease with suppurative complications, include the following:
• • Hemoptysis
  • Low-grade fever
  • Fatigue
  • Weight loss
  • Chest pain

Physical

• Right middle lobe syndrome (RMLS) is essentially a radiographic diagnosis, and physical findings widely vary.
• Auscultation of the lungs may reveal a fine wheeze, rales, or diffuse rhonchi, ranging from decreased aeration and dullness to percussion in the region of the right middle lobe. The right middle lobe is anterior, best heard at the nipple. The medial segment is located medial to the nipple; the lateral segment is lateral to the nipple. Failure to listen to this area results in failure to hear the right middle lobe.
• Clubbing is rarely found in patients with advanced disease.

Causes

• Intra-airway origin
• • In children, RMLS is usually secondary to primary ventilation disorders. Chronic inflammation of the airways, which contributes to atelectasis of the right middle lobe, is present. A paucity of collateral ventilation is observed in children and serves to prevent reinflation.
  • Primary disorders of ventilation include the following:
  • • Asthma
    • Bronchopulmonary dysplasia
    • Chronic pneumonia or bronchitis
    • Cystic fibrosis
    • Other chronic lung diseases caused by aspiration or gastroesophageal reflux
    • Primary ciliary dyskinesia (immotile cilia syndrome)
  • Airway foreign body aspiration
  • Endobronchial tumors
  • Mucous plugging, as from any of the above
  • Granulation tissue
• Extraairway origin
• • Extraluminal compression is caused by the following:
  • • Cardiovascular anomalies
    • Congenital malformations such as situs inversus and other anatomical defects such as anomalous branching or abnormal diameter, length, or structure of the bronchi
    • Lymphadenopathy of peribronchial nodes
    • Tumors
    • Traction diverticula of the esophagus
• Infectious etiologies 
• • Whether the infection is a cause of the collapse or a result of airway stasis and poor clearance may not be clear. 
• • Primary infectious etiology is more frequent in adults; however, one pediatric study found that 50% of children with collapsed right middle lobe had an underlying bacterial infection.¹
  • Infectious causes also increase in frequency among immunocompromised patients.
  • Common bacterial causes in children include Streptococcus pneumoniae and Haemophilus influenzae.
  • Fungal causes include histoplasmosis, blastomycosis, and aspergillosis, which manifest as allergic bronchopulmonary aspergillosis (APBA).
  • Mycobacteria, including Mycobacterium tuberculosis, Mycobacterium avium-intracellulare, and Mycobacterium fortuitum have also been identified as causal agents.
  • Occurrence is mainly caused by extrinsic compression by hilar lymph nodes, which are commonly observed in these infections as well as in fungal infections.

DIFFERENTIALS

Section 4 of 11  

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Other Problems to be Considered

Diagnosis of right middle lobe syndrome (RMLS) is mainly based on the presence of atelectasis of the right middle lobe of long duration. Rule out acute right middle lobe pneumonia with repeat chest radiography within 3-4 weeks of initial onset.

WORKUP

Section 5 of 11  

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Lab Studies

• Purified protein derivative (tuberculin) skin test
• CBC count and differential
• Westergren sedimentation rate
• Fungal serology by complement fixation and immune diffusion
• Quantitative immunoglobulins panel

Imaging Studies

• Chest radiography with anteroposterior (AP) and lateral views
• • The classic finding of right middle lobe syndrome (RMLS) is a blurred right heart border and a loss of volume in the right middle lobe (see Media file 1).
  • A wedge-shaped density extending from the hilum anteriorly and inferiorly is best visualized on a lateral view (see Media file 2).
  • Consolidation and infiltration are less commonly observed.
  • Acute pneumonia should clear radiologically in 6-8 weeks.
• CT scanning
• • If bronchiectasis is suspected, confirm diagnosis by performing high-resolution chest CT scanning (see Media file 3), which carries less risk to younger patients or patients with asthma than the seldom-used traditional bronchography.
  • High-resolution chest CT imaging is also helpful for follow-up medical therapy.

Other Tests

• Pulmonary function tests
• • Pulmonary function tests (PFTs) can be used to establish a previously unidentified asthmatic component.
  • Although findings on a baseline forced expiratory volume in one second (FEV₁) may be normal, a prebronchodilator and postbronchodilator study with 10-15% changes in FEV₁ is diagnostic for asthma.

Procedures

• The value of bronchoscopy is 2-fold, as follows: 
• • It is immediately therapeutic in removing mucus and clearing the airway and can be curative in some cases. 
  • It allows visualization of the airway and the ability to determine patency of the right middle lobe bronchus and to discern whether endobronchial obstruction is the cause.
• Bronchoalveolar lavage can be concurrently performed to determine cellular elements in the right middle lobe. It can also be used to assess the presence of infections by culturing and staining for bacterial, fungal, viral, and mycobacterial pathogens.

TREATMENT

Section 6 of 11  

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Medical Care

• Long-term follow-up of children shows that most patients do not experience recurrent or persisting symptoms. This indicates that the first line of treatment in all cases is conservative medical management, except in cases involving neoplastic origin and those with bronchiectasis.
• Chest physical therapy and postural drainage are the hallmarks of therapy.
• • Treat the asthmatic child with aggressive anti-inflammatory therapy such as inhaled steroids. Consider systemic steroids.
  • Provide the patient with chest physical therapy and postural drainage. In unresponsive patients or patients who have a predisposition to airway colonization, an appropriate antibiotic, as determined by a bronchoalveolar lavage (BAL) culture, should be added to their regimen.
• Patients with fungal infections (eg, histoplasmosis) or tuberculous infections who have hilar adenopathy and complete blockage of their right middle lobe should be treated aggressively. The addition of systemic corticosteroids may be necessary.

Surgical Care

• Lobectomy
• • Lobectomy is indicated in cases of malignancy and bronchiectasis that are unresponsive to medical therapy.
  • Only perform lobectomy when right middle lobe syndrome (RMLS) is associated with systemic symptoms such as failure to thrive, persistent cough, and recurrent fever or when chronic infection threatens the remainder of the lung.
• Bronchography: Avoid bronchography because of potential risks to the patient unless surgery is seriously considered; therefore, always explore high-resolution CT imaging as an alternative.

MEDICATION

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The role of antibiotic therapy in the treatment of right middle lobe syndrome (RMLS) is not well studied. Antibiotics are usually administered during acute exacerbations and when bronchiectasis is well established. In this latter instance, long-term rotation of antibiotics (ie, 3 weeks on and 1 week off, then change antibiotic) is advocated. Base the choice of antibiotic on culture and sensitivity results of either sputum or BAL fluid. When this is not available, select a broad-spectrum antibiotic to cover S pneumoniae, other streptococci, H influenzae, and Moraxella catarrhalis. Antibiotics can be orally or intravenously administered. The use of nebulized antibiotics has not been studied in RMLS. Also see Asthma for relevant treatment information.

Drug Category: Antibiotics

Empiric antimicrobial therapy must be comprehensive and should cover all likely pathogens in the context of the clinical setting.

FOLLOW-UP

Section 8 of 11  

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Further Inpatient Care

• Most patients with right middle lobe syndrome (RMLS) are managed as outpatients; however, acute exacerbations may require inpatient care and intravenous antibiotics.

Further Outpatient Care

• Periodic office follow-up with repeat chest radiographs is warranted to assess response to medical therapy. Periodic assessment of caregivers' chest physical therapy techniques can be monitored during the visits as well.

Deterrence/Prevention

• Prevention of RMLS has not been studied, but, because of the long-term morbidity associated with this condition, perform a repeat chest radiograph in children with asthma who have atelectasis of the right middle lobe during an acute asthma exacerbation and in children with acute pneumonia of the right middle lobe to document resolution.
• Recently, a more aggressive approach in a cohort of 55 symptomatic children with RMLS followed for a median duration of 2 years yielded good outcome.² All these children underwent flexible bronchoscopy at presentation, and specific antibiotic therapy was given based on bronchial alveolar lavage fluid. Bronchiectasis was documented in 27% of patients, and the duration of symptoms correlated with the development of this unfavorable complication.

Complications

• Long-term complications range from none to minimal pulmonary scarring of no discernible physiological consequence to severe bronchiectasis requiring surgical intervention.
• In children with asthma, RMLS may produce a vicious cycle of infection, inflammation, and asthma exacerbation.

Prognosis

• RMLS resolves in approximately 33% of children after bronchoscopy. Approximately 33% recover eventually with medical management, 22% require lobectomy, and 11% have decreased severity of symptoms but should be monitored for the possibility of requiring lobectomy later.
• About one third of patients with RMLS in early childhood continue to have symptoms in later childhood. These patients usually experience asthma symptoms or another chronic lung condition such as cystic fibrosis.
• The remaining two thirds of children with RMLS do not have persistent symptoms later in adulthood.

Patient Education

• Because chest physical therapy and postural drainage are of paramount importance in the management of RMLS, instruct the caretaker with appropriate techniques and position for right middle lobe physiotherapy. This is often performed by a registered respiratory or physical therapist. Regardless, the therapist should be somebody who frequently deals with children.
• Flutter valve and high-frequency oscillation (known as the vest) have not been studied in this setting, but they may be alternative modalities of delivering chest physical therapy.

MISCELLANEOUS

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Medical/Legal Pitfalls

• The vague nature of right middle lobe syndrome (RMLS) symptoms may lead to a delay in diagnosis. Approximately 10% of children admitted for acute asthma have atelectasis of one or more lobes; the right middle lobe is most commonly affected. Because of the high incidence in children with asthma, if chest radiography suggests right middle lobe atelectasis, another chest radiograph should be obtained 3-4 weeks later to document total resolution. Early detection and aggressive initial management may alter the course of this disease.
• Too often, RMLS is mistaken for an acute pneumonia and is simply treated with antibiotics, without a follow-up radiograph. This underdiagnosis with resultant undertreatment can be harmful to the underlying lung.

MULTIMEDIA

Section 10 of 11  

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Media file 1:  Posteroanterior chest radiograph demonstrating right middle lobe collapse and infiltrate. Note blurred right heart border.
	View Full Size Image
Media type:  Radiograph

Media file 2:  Lateral view chest radiograph of Media file 1 showing a wedge-shaped density extending from the hilum anteriorly and inferiorly.
	View Full Size Image
Media type:  Radiograph

Media file 3:  Chest CT scan showing extensive bronchiectasis of both medial and lateral segments of the right middle lobe.
	View Full Size Image
Media type:  CT

REFERENCES

Section 11 of 11

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1. Springer C, Avital A, Noviski N, et al. Role of infection in the middle lobe syndrome in asthma. Arch Dis Child. May 1992;67(5):592-4. [Medline].
2. Priftis KN, Mermiri D, Papadopoulou A, et al. The role of timely intervention in middle lobe syndrome in children. Chest. Oct 2005;128(4):2504-10. [Medline].
3. American Journal of Medicine. Right middle lobe syndrome progressing to death in a 77-year-old woman. Am J Med. Mar 1987;82(3):471-80. [Medline].
4. Ayed AK. Resection of the right middle lobe and lingula in children for middle lobe/lingula syndrome. Chest. Jan 2004;125(1):38-42. [Medline]. [Full Text].
5. Brown M, Lemen R. Bronchiectasis. In: Kendig's Disorders of the Respiratory Tract in Children. Philadelphia, Pa: WB Saunders Co; 1998:150-2.
6. Case records of the Massachusetts General Hospital. Weekly clinicopathological exercises. Case 19-1984. A 57-year-old woman with recurrent pneumonia. N Engl J Med. May 10 1984;310(19):1245-52. [Medline].
7. De Boeck K, Willems T, Van Gysel D, et al. Outcome after right middle lobe syndrome. Chest. Jul 1995;108(1):150-2. [Medline]. [Full Text].
8. Dees SC, Spock A. Right middle lobe syndrome in children. JAMA. Jul 4 1966;197(1):8-14. [Medline].
9. Eggleston PA, Ward BH, Pierson WE, Bierman CW. Radiographic abnormalities in acute asthma in children. Pediatrics. Oct 1974;54(4):442-9. [Medline].
10. Gudmundsson G, Gross TJ. Middle lobe syndrome. Am Fam Physician. Jun 1996;53(8):2547-50. [Medline].
11. Kinzy JD, Powers WP, Baddour LM. Case report: Blastomyces dermatitidis as a cause of middle lobe syndrome. Am J Med Sci. Oct 1996;312(4):191-3. [Medline].
12. Kwon KY, Myers JL, Swensen SJ, Colby TV. Middle lobe syndrome: a clinicopathological study of 21 patients. Hum Pathol. Mar 1995;26(3):302-7. [Medline].
13. Lambert GW, Baddour LM. Right middle lobe syndrome caused by Mycobacterium fortuitum in a patient with human immunodeficiency virus infection. South Med J. Jul 1992;85(7):767-9. [Medline].
14. Livingston GL, Holinger LD, Luck SR. Right middle lobe syndrome in children. Int J Pediatr Otorhinolaryngol. Jun 1987;13(1):11-23. [Medline].
15. Priftis KN, Anthracopoulos MB, Mermiri D, et al. Bronchial hyperresponsiveness, atopy, and bronchoalveolar lavage eosinophils in persistent middle lobe syndrome. Pediatr Pulmonol. Sep 2006;41(9):805-11. [Medline].
16. Rock MJ. The diagnostic utility of bronchoalveolar lavage in immunocompetent children with unexplained infiltrates on chest radiograph. Pediatrics. Mar 1995;95(3):373-7. [Medline].
17. Saha SP, Mayo P, Long GA, McElvein RB. Middle lobe syndrome: diagnosis and management. Ann Thorac Surg. Jan 1982;33(1):28-31. [Medline].
18. Shah A, Bhagat R, Panchal N, et al. Allergic bronchopulmonary aspergillosis with middle lobe syndrome and allergic Aspergillus sinusitis. Eur Respir J. Jun 1993;6(6):917-8. [Medline].
19. Thacher H, Kaplan A. Middle lobe syndrome in asthmatic children. J Maine Med Assoc. Mar 1972;63(3):46-8 passim. [Medline].
20. Torkian B, Kanthan R, Burbridge B. Diagnostic pitfalls in fine needle aspiration of solitary pulmonary nodules: two cases with radio-cyto-histological correlation. BMC Pulm Med. Sep 8 2003;3(1):2. [Medline]. [Full Text].
21. Wagner RB, Johnston MR. Middle lobe syndrome. Ann Thorac Surg. Jun 1983;35(6):679-86. [Medline].

Article Last Updated: Oct 17, 2007