What Is Pulmonary Gangrene?
Pulmonary gangrene is a rare but serious complication of pneumonia that is often the final stage of progressive pulmonary parenchymal necrosis (death of lung tissue) and results in the sloughing of the pulmonary segment or lobe. The damage includes necrotizing pneumonia and pulmonary abscess, damaging the tissues to death. Normal lung functioning requires pulmonary vitalization that is facilitated by lung ventilation and optimal perfusion. Perfusion is achieved by normal blood flow to and from the lung, bathing the lung with oxygen, and removing the wastes. The perfusion may be disrupted due to infections, foreign body aspiration, cancers, trauma, radiation damage, chemotherapeutic side effects, or post-surgical complications. Deficient blood flow results in tissue necrosis, overgrowth of microflora, and formation of pulmonary abscesses.
What Causes Pulmonary Gangrene?
The cause of pulmonary gangrene is essential to program a treatment plan. The causes may be categorized into primary and secondary ones based on the mode of onset.
1. Primary Causes:
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Pulmonary embolism.
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Cancers.
2. Secondary Causes:
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Trauma.
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Post-surgical complications.
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Sepsis.
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Drug-induced pulmonary gangrene.
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Radiation-induced.
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Foreign body aspiration.
The underlying pathophysiology leading up to pulmonary gangrene due to primary and secondary causes may be defined and studied to understand the link from the cause to necrosis. Severe pneumonia, uncontrolled deep lung infections, pulmonary embolism that occurs due to a clot lodging in the lung due to hypercoagulable systemic state or deep vein thrombosis, lung cancers with parenchymal necrosis, and opportunistic infections, hilar tumors causing bronchial obliteration (fibrous proliferation, submucosal inflammation and fibrosis of the bronchiolar walls), or hilar lymphadenopathy (swelling of the hilar lymph nodes) can precipitate the primary causes of pulmonary gangrene.
Secondary causes of pulmonary gangrene may be due to contusional lung hemorrhage (bleeding in lungs due to trauma), improper ligation of pulmonary vessels (post-surgical complication), lobar torsion after surgery (rotation of pulmonary lobe), pulmonary sepsis (extreme lung infection) due to systemic infections, septic secondary to pulmonary emboli (infection due to blood clot), chemotherapeutic drug-induced toxicity (cancer drug side-effect), radiation pneumonitis (lung inflammation from radiation therapy), or aspiration pneumonia (due to breathing in foreign material).
What Are the Clinical Features of Pulmonary Gangrene?
Necrotizing pneumonia has been described in adults since the forties but has been reported in children only during the mid-nineties.
Some of the findings reported in medical literature and by clinicians are as follows:
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Lobar pneumonia (alveolar sacs filled with pus).
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Necrotizing pneumonitis (a complication of bacterial community-acquired pneumonia).
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Lung cysts.
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Lung abscesses (liquefaction necrosis of the lung tissue).
Symptoms of pulmonary gangrene are:
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Chest pain.
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Pleurisy (inflammation of the pleura).
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Cough.
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Dyspnea (shortness of breath).
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Purulent expectorants.
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Reduced tolerance of physical activity.
Systemic manifestations of pulmonary gangrene include:
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Hypotension (decreases blood pressure).
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Tachycardia (increased heart rate).
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Tachypnea (rapid breathing).
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Dyspnea.
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High fevers.
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Severe chest pain.
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Malaise.
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Lack of appetite.
In severe or advanced cases, patients may present with the following:
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Deterioration of consciousness.
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Abundant sputum.
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Putrid sputum (foul-smelling sputum).
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Hemoptysis (blood in cough).
How to Diagnose Pulmonary Gangrene?
Apart from the clinical findings, physicians or pulmonologists may order specific tests to extrapolate a definitive diagnosis and further formulate a treatment protocol. These include various blood paraments, lung function tests, and imaging studies.
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Laboratory Tests: A complete blood and biochemical analysis are essential in almost all pulmonary diseases. Left shift (abundant neutrophil consumption) and abundance of WBCs are indicative of systemic inflammation. Other parameters to study include C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and procalcitonin. Blood cultures and serological tests may be included in some instances of infection.
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Sputum Analysis: The study of the sputum is necessary to guide the use of the type and dose of the antibiotic regimen. Yet, clinicians do not wait for the culture results, as it may take several days, and prescribe empiric broad-spectrum antibiotics. Polymerase chain reaction (PCR) has turned the table in favor of diagnosticians as the pathogens can be detected rapidly from a sputum sample or throat swab.
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Bronchoscopy: Direct visualization of the lung via a bronchoscope (a flexible device with a camera and light source) becomes primordial to help evaluate the condition of the tracheal tract and the bronchus. Some of the common findings from bronchoscope recordings are lobar torsion (commonly of the right middle lobe), right upper lobe resection, lobar gangrene, and total obliteration of the bronchial orifice. Suspected bronchial lesions may be studied further with brushing, lavage with saline, and punch biopsy to concrete a diagnosis.
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Radiographic Imaging: Chest X-rays can track the progress of the disease from a smaller pneumonia patch, lobar pneumonia, lung abscess, and parapneumonic effusion, then to diffuse necrotic lung gangrene. Other findings involve consolidation of the lung, cavitation, and interstitial infiltrates. Lack of any abnormalities in the X-ray should not reassure the patients but rather serve as an indication to take interval follow-up chest X-rays. Due to the symptoms being common findings in various other lung diseases, the diagnostic value of radiographic findings is low.
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Angiography: When the pulmonary vasculature of the infected lung is disrupted, angiography provides the relevant means to evaluate the vascular status and also aids in differentiating the presenting conditions from other diseases. Due to the more invasive nature and potential risk of vascular injuries, CTA (computed tomography angiography) has replaced traditional angiographies.
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Computer Tomography: The images obtained from CT scans can be studied to define the localized or diffuse gangrenous forms. CT with and without contrast can help preoperatively isolate the affected regions and assess the occlusion of pulmonary vessels. CT images show multiple low-density areas, consolidations, air-trapping, loculated effusion, and hydropneumothorax due to broncho-pleural fistula.
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Lung Function Tests (LFTs): These are the staple tests for any pulmonary dysfunction. Although not absolutely diagnostic, LFTs provide essential information about the possibility and extent of lung resection.
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Nuclear Imaging: These imaging studies can aid in establishing a definitive diagnosis, evaluating the extent of lung resection, and estimating post-operative lung function by means of perfusion and ventilation scans. These images are more reliable for the said parameters than LFTs.
How to Treat Pulmonary Gangrene?
The treatment of pulmonary gangrene may be discussed under three headings-medical, surgical, and support.
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Medical Therapy: Medical treatment forms the mainstay of pulmonary gangrene management, which aims to control both localized and systemic manifestations, preventing systemic inflammatory response syndrome and septic shock. This involves aggressive broad-spectrum antibiotics administration, steroids, fluid replacement, and securing the airway. The antibiotic therapy should be modulated as per the culture reports. Aggressive therapy should be continued for 48 hours. If the patient's condition improves within that time, lung resection may be delayed or avoided. If not, then surgical means need to be explored to prevent bilateral necrotizing pneumonia and death.
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Surgical Intervention: It is difficult to define the correct time for surgical interventions due to the presence of accompanying pleural infections, empyema, and chest wall infections, that make the surgery prone to post-operative bleeding, air leakage due to bronchial rupture, and persistent pleural infections. A two-stage surgical approach is proposed with reasonable success rates. In the first stage, tube thoracostomy is done to clean the pleural space and prepare for subsequent resection. In case of failed stage-1 (insufficient symptom alleviation), surgical resection should be done promptly. The extent of resection is largely dependent on the extent of necrosis. All of the necrotic tissues must be removed.
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Supportive Therapy: Extracorporeal membrane oxygenation or ECMO is a supportive means to provide adequate oxygenation and circulation when the lungs fail to do so. The use of ECMO is currently being recommended for various non-cardiac circulatory failures as well.
What Is the Prognosis of Pulmonary Gangrene?
When the gangrenous involvement extends to multiple lobes, the extent of resection must be carefully evaluated, and only after complete resection of necrotic tissue can infection control get easier. Long-term follow-ups become mandatory as the individuals become susceptible to recurrent pulmonary infections and even necrosis and gangrene. Pulmonary rehabilitation must be started three months after resection.
What Are the Complications of Pulmonary Gangrene?
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Multiple organ failure.
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Death.
Conclusion
Lung gangrene is a fatal complication of various conditions that, when left untreated, can cause serious fatal complications. In extensive damages, infection control can only be achieved after the complete removal of necrotic tissue. It is absolutely necessary to keep up with the follow-up appointments. Also, negative X-rays with existing symptoms are not reassuring. Hence, treatment (medical) needs to be implemented as soon as the patient comes in with suspected lung infections.
