Alveolopleural Fistula

Alveolopleural fistula is a communication between the alveoli (or distal airways) and the pleural space, which leads to a persistent air leak after a chest drain is placed. Unlike bronchopleural fistula, no large central bronchus is involved, and the leak arises from the peripheral lung.

A leak persisting beyond 5 to 7 days is considered prolonged. It happens after lung resection (in 8 to 15%, with the commonest cause), spontaneous pneumothorax in emphysema and fibrotic lung disease, necrotising pneumonia, tuberculosis, lung abscess, trauma, radiotherapy, chest drain or biopsy injury and mechanical ventilation with high pressures (acute respiratory distress syndrome).

Pathophysiology. Damage to the visceral pleura and underlying parenchyma (from surgery, necrosis, rupture of a bulla or barotrauma) allows air to leak with each breath into the pleural space, particularly during inspiration with positive pressure or coughing. Poor tissue healing is common in emphysema, steroid use, malnutrition, infection and radiotherapy.

Persistent bubbling in the underwater seal chamber after drain insertion, which increases with coughing or expiration, subcutaneous emphysema, failure of the lung to expand, and in ventilated patients loss of tidal volume. Breathlessness, pleural pain and infection can occur. Pneumothorax with a large leak and tension is possible.

Rapid enlargement of subcutaneous emphysema, hypotension or hypoxaemia needs urgent drain check and replacement.

• Clinical: a continuous or intermittent air leak seen as bubbling in the drain chamber. Digital drainage systems quantify the flow (in mL per minute).
• Chest radiograph or CT: persistent pneumothorax or hydropneumothorax, parenchymal damage, bullae, consolidation or cavity, and the position of the drain.
• Bronchoscopy to exclude a central bronchial fistula, and to define the leaking segment by balloon occlusion with watching for a fall in leak flow.
• Infection workup, since empyema often accompanies it: fluid culture, white cell count and C-reactive protein.
• Nutritional assessment and assessment of risk factors for poor healing (steroids, diabetes control, smoking).

Differential diagnosis.

• Bronchopleural fistula (central airway)
• Leaking drain connection, or drain placed in subcutaneous tissue
• Oesophagopleural fistula
• Persistent pneumothorax from a non-expanding (trapped) lung
• Loculated empyema with air

• Conservative: keep the chest drain on water seal or low suction (-5 to -10 cmH2O), avoiding high suction which pulls air through the defect. Treat infection, optimise nutrition (energy 25 to 30 kcal/kg daily and protein 1.2 to 1.5 g/kg daily), stop smoking, correct anaemia and control diabetes. Cough suppression and chest physiotherapy.
• Ventilated patients: use the lowest possible airway pressures and tidal volumes, with a short inspiratory time, and early liberation from ventilation when possible.
• Many leaks close by 7 to 14 days. If a leak persists, escalate.
• Chemical pleurodesis through the drain: talc slurry (4 to 5 g in 50 mL saline), with analgesia (lidocaine 3 mg/kg, maximum 250 mg, into the pleural space, and systemic analgesia).
• Autologous blood patch: 50 mL (or up to 1 to 2 mL/kg) of the patient's own blood injected into the drain, which clamps for 2 to 4 hours, with success of about 70 to 85%. A repeat dose can be given after 24 to 48 hours.
• Endobronchial one way valves (bronchoscopic placement) to the leaking segment, for patients unfit for surgery. Fibrin sealant or other sealants are less commonly used.
• Surgery: video assisted thoracoscopic stapling or suture of the leak, bullectomy, or pleurectomy with pleurodesis, when these measures fail, or earlier in good risk patients.
• Outpatient management with a portable one way valve (Heimlich type) drainage device is possible for stable patients.
• Antibiotics for infection, directed by culture (for example amoxicillin-clavulanate 625 mg three times daily).

Complications and prognosis. Prolonged hospital stay, empyema, malnutrition, and respiratory failure. Most leaks close with conservative measures or pleurodesis, though success is lower in emphysema and fibrosis.

Monitoring. Daily leak assessment and radiograph, weekly review of nutrition and infection markers, and a check at 2 weeks and 6 weeks after drain removal.

Referral and escalation. Refer to thoracic surgery or a pleural service for a leak persisting beyond 5 to 7 days, and to a bronchoscopy unit for valve placement.