HYPERLUCENT HEMITHORAXDr Prakash Sapkale

Confirm the side appearing hyperlucent is abnormal - Exclude contralateral increased density. e.g. pleural effusion in a supine patient or pleural thickening or chest wall hemihypertrophy.

ETIOLOGY ROTATION AND TECHNICAL FACTORS CHEST WALL PLEURA LUNG PULMONARY VESSELS

1. ROTATION AND TECHNICAL FACTORS

ROTATION

Poor Technique

Scoliosis

The hyperlucent hemithorax is the side to which the patient is rotated(increase in density over the lung rotated away from the film cassette).

1. ROTATION AND TECHNICAL FACTORS

THE HEEL EFFECT (ANODE CUTOFF)

The intensity of the x-ray beam as it leaves the focal spot has nonuniform distribution.

The intensity of film exposure on the anode side of the x-ray tube is significantly less than that on the cathode side of the tube- caused by absorption of some of the x-ray photons by target itself.

Difference in exposure intensities will be less if focus film distance is increased ; and in case of smaller film.

1. ROTATION AND TECHNICAL FACTORS

THE GRID CUTOFF

It is the loss of primary radiation that occurs when the images of the lead stripes are projected wider than they would be with ordinary magnification.

The resultant radiograph will be lighter in the area in which the cutoff occurs.

2. CHEST WALL 1.MASTECTOMY-

Absent breast +/- pectoral muscle shadows. 2.POLIOMYELITIS-

Pectoral muscle atrophy; atrophic changes in the shoulder girdle and humerus.

3.POLAND SYNDROME- A rare birth defect characterized by

-Chest muscle deformities - absence of the pectoralis minor and the breastbone part of the pectoralis

major -Underdevelopment or absence of breast or nipple on the

affected side -Patchy absence of hair under the arm on the affected side

Additional symptoms on the affected side may include: - -Underdeveloped or missing ribs

-Underdeveloped arm, hand, and fingers -Abnormally short, webbed fingers -Small, elevated scapula , called Sprengel deformity-It may be associated with other conditions such as

Moebius syndrome and Klippel Feil Syndrome

3.PLEURA

PNEUMOTHORAX- sharp lung edge peripherally and absent vascular margins beyond lung border.

4. LUNG

COMPENSATORY EMPHYSEMA-Following lobectomy (rib defects and

opaque bronchial sutures), lobar collapse, shunting procedure, lobar agenesis or hypoplasia.

OBSTRUCTIVE EMPHYSEMA-Ball valve mechanism-Air trapping

on expiration-increased lung volume-shift of the mediastinum to the contralateral side

4. LUNGObstructive emphysema can be due

to- Endobronchial obstruction-

Bronchial foreign body, stricture, atresia, granuloma, broncholith,mucus plug or mucoid impaction, neoplasm- bronchogenic carcinoma, carcinoid, endobronchial metastasis.

Extrabronchial obstruction or compression-Mediastinal mass, hilar lymphadenopathy(tuberculosis,histoplasmosis, sarcoidosis,lymphoma,metastatic disease), anomalous vessels.

4. LUNG UNILATERAL BULLAE

-Vessels are absent rather than attenuated-May mimic pneumothorax.

MACLEOD’S SYNDROME(Swyer-James syndrome )

-Late sequela of childhood bronchiolitis.-Post infectious syndrome-diminished

vascularity, arrest of progressive growth and alveolarization of affected lung-hypoplasia of lung

-Small lung with small main and peripheral arteries.-Air trapping occurs on expiration.-Decreased number of bronchial

divisions(5-10).

4. LUNG CONGENITAL LOBAR EMPHYSEMA

-Potentially reversible though possibly life-threatening cause of respiratory distress in the neonate.-Progressive overdistension of lobe at birth .-Symptoms: respiratory distress (90%) and cyanosis < 6 mos -Treatment: surgical resection-Etiology(theories)-Immaturity of bronchial cartilage, Endobronchial obstruction (fold,web,mucus) ,Bronchial compression from vascular structure e.g. PDA, aberrant left pulmonary artery-Usually involves one lobe MC- LUL ,then RUL,RML-air trapping and compressive changes in the remainder of the lung -2 forms:1) Hypoalveolar 2) Hyperalveolar-Can be identified on in utero ultrasound.-X-Ray apperance

Mass-like opacity following birth (fluid-filled, overdistended lobe)Lucency develops over next two weeks Air-trapping occurs in affected lobe Compression atelectasis of adjacent lobesShift of mediastinum away from lesion

5. PULMONARY VESSELS PULMONARY ARTERY ATRESIA, HYPOPLASIA,

COARCTATION,BRANCH STENOSIS OR ANOMALOUS ORIGIN

-(eg, “pulmonary sling” with left PA arising from right PA)

PULMONARY ARTERY COMPRESSION- by inflammatory process or neoplasm

PULMONARY VEIN ATRESIA OR STENOSIS

PULMONARY THROMBOEMBOLISM-To a major pulmonary artery(at least lobar in

size)-The pulmonary artery is dilated in size and the

affected lung shows moderate loss of volume.

6. OTHERS PNEUMATOCELE)

-A thin-walled, gas-filled space within the lung, usually occurring in association with acute pneumonia (most commonly of staphylococcal etiology

-Noninfectious etiologies include hydrocarbon ingestion, trauma, and positive pressure ventilation.

PULMONARY SEQUESTRATION (INTRALOBAR)[CONGENITAL THORACIC MALFORMATION.]

-An uncommon mass that is usually cystic and is composed of nonfunctioning primitive tissue that does not communicate with the tracheobronchial tree.

-Blood supply is from systemic circulation rather than the pulmonary circulation.

-The 2 forms of pulmonary sequestration are intrapulmonary, which is surrounded by normal lung tissue, and extrapulmonary, which has its own pleural investment.

CONGENITAL CYSTIC ADENOMATOID MALFORMATION

-developmental hamartomatous abnormality of the lung, with adenomatoid proliferation of cysts resembling bronchioles.

-A lesion containing all the normal components of lung tissue except cartilage.

-a mass containing both solid and cystic components.

-The main differential diagnosis in the neonatal period is a congenital diaphragmatic hernia

SCIMITAR VEIN SYNDROME

(VENOLOBAR SYNDROME/HYPOGENETIC LUNG)

-Hypoplastic lung that is drained by an anomalous vein into the systemic venous system.

-It almost exclusively occurs on the right side.

-A small lung with ipsilateral mediastinal shift, and in one third of cases the anomalous draining vein may be seen as a tubular structure paralleling the right heart border in the shape of a Turkish sword (“scimitar”)