2. • Pulmonary tuberculosis affects predominantly the upper lobes.
• When tuberculosis is confined to the lower lung fields, it often
masquerades as pneumonia and the correct diagnosis may not be
sought for a long time.
3. Definition
• The lower lung field TB is defined as tuberculous disease on the
postero-anterior [PA] chest radiograph in an area which extends
below an imaginary horizontal line traced across the hilum and
includes the parahilar regions.
• In a PA radiograph of the chest, lower lung field includes the middle
lobe on right side and lingula on left side in addition to the lower
lobes.
4. PATHOGENESIS
• Due to ulceration of a bronchus by a lymph node affected by TB with
spillage of TB material into the bronchus.
• Lower lung field TB occurs as a continuum of primary TB or soon after in
the post-primary phase
• Another plausible mechanism is majority of Indians tie their clothes tightly
around the upper abdomen and this results in impaired movement of
diaphragm
• It has been suggested that the resultant impaired movement of diaphragm
leads to costal type of breathing , which leads to decreased ventilation,
retarded blood circulation and lymphatic flow in lower lung fields, thus
making them more vulnerable to TB
5. Associated Conditions
Lower lung field TB appears to be more common in patients receiving
1. corticosteroid treatment
2. patients with hepatic or renal disease
3. diabetes mellitus
4. pregnancy
5. Silicosis
6. kyphoscoliosis and
7. HIV.
6. Signs and symptoms
• Cough with variable amounts of expectoration is the most frequent
symptom
• Hemoptysis
• The general toxaemic manifestations of TB infection, such as, fever,
chills, malaise, weakness and anorexia are also frequently present.
• However, a recent study from east Asia has revealed that lack of fever
more than 38 °C in lower lung field TB is an important discriminating
symptom as compared to lower lung field bacterial pneumonia.
7. • The physical signs correlate with the extent of the disease.
• Physical signs are encountered more often in patients with lower
lung field TB than in those with the classical upper lobe pulmonary TB
8. Investigations
• Sputum Examination:
• Although sputum examination is the simplest way to diagnose lower
lung field TB, isolation of Mycobacterium tuberculosis is difficult on
sputum smear or mycobacterial culture.
• However, the diagnostic yield of sputum examination is better in
patients with cavitary lesions.
9. • CXR
• More than half of the cases of lower lung field TB have right lung
involvement, whereas one-third cases have left lung involvement. Bilateral
lesions are reported in 10% of cases
• Lower lung field TB radiographic findings differ significantly from those
seen in upper lobe disease.Consolidation is the most common radiographic
finding, and it is more confluent and extensive than in upper lobe
TB.Cavitary lesions, which can be single or multiple and can occur within a
consolidation area, are also common.
• Cavities can be quite large (3-4 cm in diameter). Lower lung field TB is also
distinguished by the presence of tension cavities [thin-walled with fluid].
10. • Absence of air bronchogram in a chest radiograph is more common in
patients with lower lung field TB when compared to lower lung field
bacterial pneumonia.
• The radiographic features also have prognostic value. Patients with
lower lung field TB who have lung collapse or pulmonary
consolidation on a chest radiograph have a poor prognosis.
11.
12. • Bronchoscopy
• Early diagnosis – important for prevention of severe sequelae.
• FOB-preferred diagnostic modality for diagnosis of LLFTB.
• Abnormal findings- ulcerative granuloma , mucosal erythema,
submucosal infiltration and fibrostenosis.
13. • FOB has a higher diagnostic yield than sputum examination,
particularly in patients with radiographic findings of pulmonary
consolidation, lung collapse, or solitary mass.
• FOB is also useful in assessing the severity of endobronchial lesions in
patients with lower lung field TB.
• When FOB reveals fibrostenosis or ulcerative granuloma in patients
with lower lung field TB, the outcome is unfavourable.
• If there is severe fibrostenosis, early surgical intervention should be
considered to prevent lung damage distal to the obstruction.
14. • EBUS-Transbronchial Needle Aspiration
• Ongoing studies for cost effectiveness.
• EBUS in conjunction with FOB particularly useful in assessing smear
negative pts.
• EBUS-TBNA results in higher diagnostic yield in pulmonary TB suspect
patients with lymphadenopathy
16. Management
• Lower lung field TB is frequently confused with the more common
pneumonias.
• TB should be considered a diagnostic possibility in patients with lower
lung field lesions who have the following conditions: diabetes
mellitus, advanced age, glucocorticoid treatment, renal or hepatic
illness, malignancy or lesions with poor response to adequate
antibiotic therapy.
• FOB should be performed early to ascertain the diagnosis of TB and
assess the severity of the endobronchial lesions.
17. • Multiple sputum examinations are often necessary to secure
bacteriological proof of tuberculosis.
• The patients with lower lung field TB show a favorable response to
conventional anti-TB therapy. Delayed diagnosis affects the outcome
in these patients .Significant resolution of chest radiograph findings
and/or sputum negativity was observed with anti-TB treatment, if the
diagnosis to treatment time was less than three months.
• If severe fibrostenosis is present, early surgical intervention in the
form of sleeve operation is indicated before permanent sequelae,
such as, damage of lung distal to the obstruction and respiratory
failure occur.
