Right Middle Lobe Syndrome

Right middle lobe syndrome is recurrent or persistent collapse of the right middle lobe (and similarly the lingula, which is sometimes called Brock syndrome), with chronic or recurrent infection. It is seen in children and adults.

Two mechanisms are recognised. The obstructive type is from compression or blockage of the middle lobe bronchus by enlarged lymph nodes (tuberculosis, a main cause in Africa), a tumour (carcinoid or lung cancer), a foreign body or a mucus plug. The non-obstructive type arises from the anatomy and from airway disease.

Pathophysiology. The middle lobe bronchus is long and narrow, arises at an acute angle, and is surrounded by lymph nodes. The lobe has poor collateral ventilation because it is bounded by fissures, so even a mild obstruction leads to collapse and infection. Asthma, bronchiectasis, cystic fibrosis, primary ciliary dyskinesia, immunodeficiency, aspiration and nontuberculous mycobacterial infection can all keep it collapsed.

Chronic or recurrent cough, sputum, wheeze, recurrent pneumonia in the same area, haemoptysis, and breathlessness. Some are asymptomatic and found on a radiograph. Examination may show reduced air entry and crackles in the right lower anterior chest.

Haemoptysis, weight loss, fever and night sweats, or stridor need prompt assessment, since cancer and tuberculosis must be excluded.

• Chest radiograph: loss of the right heart border on the frontal view, and a triangular wedge density on the lateral view.
• CT chest with contrast: collapsed lobe, the state of the middle lobe bronchus (patent or obstructed), enlarged nodes, bronchiectasis and tumour.
• Bronchoscopy in adults, in children with persistent collapse beyond 6 to 8 weeks of treatment or a suspected foreign body, to inspect the lumen, obtain washings and biopsy.
• Sputum and washing for bacteria, acid fast bacilli (smear, culture and nucleic acid amplification), nontuberculous mycobacteria and fungi.
• Spirometry, immunoglobulins, sweat chloride, nasal nitric oxide and HIV test, chosen by the age and clinical features.

Differential diagnosis.

• Resolving pneumonia
• Endobronchial tumour or lung cancer
• Tuberculosis with nodal compression
• Foreign body
• Bronchiectasis from cystic fibrosis or primary ciliary dyskinesia
• Nontuberculous mycobacterial disease

• Treat the cause: antituberculosis therapy for tuberculosis (rifampicin 10 mg/kg, isoniazid 5 mg/kg, pyrazinamide 25 mg/kg and ethambutol 15 mg/kg for 2 months, then rifampicin and isoniazid for 4 months), removal of a foreign body, treatment of asthma, and resection or oncological care for tumour.
• Infection: amoxicillin-clavulanate 625 mg three times daily for 10 to 14 days in adults (reduce to 625 mg every 12 hours at eGFR 10 to 30), and weight based dosing in children. Doxycycline 200 mg on day 1 then 100 mg daily in penicillin allergy.
• Airway clearance: chest physiotherapy, positioning with the right side up, nebulised hypertonic saline 3 to 7% where tolerated, and bronchodilator with inhaled corticosteroid for asthma.
• Bronchoscopic lavage and suction to remove mucus plugs.
• Prophylaxis in recurrent exacerbations: azithromycin 250 mg daily or 500 mg three times weekly in adults, and 10 mg/kg three times weekly in children, after excluding nontuberculous mycobacteria and checking QTc.
• Surgery by thoracoscopic middle lobectomy for persisting symptoms or repeated infection with bronchiectasis after 6 months of optimal treatment, and for obstructing tumour.

Monitoring. Chest radiograph 6 to 8 weeks after treatment to confirm re-expansion, then review at 3 and 6 months, and repeat CT if collapse persists.

Referral and escalation. Refer to a respiratory physician for bronchoscopy and cause, and to a thoracic surgeon for lobectomy.