Congenital Abnormalities of the Lung

Michael Shreve, MD

Last updated for text: 7/96, for format 12/97

Outline (click on images to see larger versions)

• Bronchogenic Cyst
• Pulmonary Sequestration
• Congenital Cystic Adenomatoid Malformation of the Lung
• Congenital Lobar Emphysema
• Arteriovenous Fistula
• Congenital Pulmonary Lymphangiectasis
• References
  

Bronchogenic cyst

• Pathophysiology - anomalous bud from tracheobronchial tree between 5th-16th wk gestation
  • arrested in embryonic stage
  • contain tissue normally found in trachea/bronchi
    • mucus glands
    • smooth muscle,
    • elastic tissue
    • cartilage
  • can enlarge due to secretion production, become fluid-filled
  • malignancies can develop (rare)
• Location - 5 classifications
  • paratracheal
  • carinal
  • paraesophageal
  • hilar
  • misc. - detach from tracheobronchial tree and migrate to various sites (pericardial, cervical, subcutaneous, abdominal, etc.)
• Clinical manifestations - result from compression of adjacent structures
  • cough
  • stridor
  • wheezing
  • air trapping & obstructive emphysema, mediastinal shift
  • atelectasis
  • impaired secretion clearance if recurrent pneumonia
  • dysphagia, epigastric discomfort, chest pain, etc.
  • sx's can develop at any age (5-19% are asymptomatic)
  • typically presents one of two ways:
    • airway compression & resp. distress: presents in infancy
    • retained secretions & infection: presents in childhood
• Diagnosis - CXR - variable
  • smooth contoured mass
  • may have air-fluid level
  • may be hidden in mediastinum
  • CT - useful if cyst not evident on plain film
  • esophagram - especially if dysphagia present
  • bronchoscopy (flexible) - may be helpful but pos. pressure
  • and airway instrumentation may worsen sx's
• Treatment - surgical excision
  • even if asymptomatic (to prevent later complications)
  • preceded by abx if infected
  • transbronchial drainage unproved
  • should NOT fly prior to excision - cyst can expand up to 30% at commercial jet cabin pressure
• Prognosis - excellent with excision
  • symptomatic infants mortality rate:
  • without excision = 100%
  • with excision = 0-14%

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Pulmonary Sequestration

• Pathophysiology
  • non functional embryonic lung tissue
  • no communication with normal bronchial system
  • supplied by aberrant systemic artery
    • usually thoracic aorta
    • can be abd. aorta, intercostals, etc.
  • intralobar sequestration - within visceral pleura
    • surrounded by normal lung
    • venous drainage via pulm. veins
      • 75%
    • extralobar sequestration - exist outside normal lung pleura
      • venous drainage via systemic veins
      • 25%
    • pleura may be adherent to mediastinum, diaphragm, thoracic wall
    • other anomalies assoc. (extralobar = 59% of time, intralobar = 14%)
      • diaphragmatic hernias (40% with extralobar sequestration)
      • diaphragm eventration
      • others
• Location
  • most commonly post. basal segment of LLL
  • intralobar = 98% in lower lobes, 58% of these on left
  • extralobar = 77% between diaphragm and lower lobe, 83% of these on left
• Clinical Manifestations - present with sx's of chronic/recurrent pneumonia
  • productive cough
  • fever
  • hemoptysis
  • if large systemic art. to venous shunt then may have exercise intol.
  • rarely detected in infancy (usually found due to assoc. with other anomalies)
  • 1/3 found by age 10
• Diagnosis
  • CXR
    • intralobar = solid/cystic/multicystic mass with long axis pointed at aorta
    • extralobar = uniform density
  • CT or MRI
    • good for locating large vascular supply
  • aortic angio or IV radioisotope study
    • can delineate small art. supplying vessels present in 15%
• Treatment
  • resection even if asymptomatic to prevent future serious infx.
    • intralobar - removal of involved lobe
    • extralobar - removal of sequestration only
  • if infx present then preop abx course
• Prognosis - excellent post-op if no other anomalies present

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Congenital Cystic Adenomatoid Malformation of the Lung

• Pathophysiology - solid areas of tubular structures resembling term. bronchioles(adenomatoid areas) interspersed with cystic areas, 3 types:
  • type I = large cysts, little adenomatoid areas
  • type II = mixed
  • type III = entirely adenomatoid
    • no mature alveoli - resembles fetal lung at 20 wks
    • normal surrounding lung is atelectatic, often hypoplastic
    • blood supply from pulm art.
• Location - anywhere in lung parenchyma
• Clinical Presentation
  • neonatal (35-50%) - related to mass effect due to connection to tracheobronchial tree and expansion of cysts
    • - progressive severe resp. distress
    • - polyhydramnios (due to compression of esophagus)
    • - hydrops fetalis (due to compression of heart, vessels)
  • after neonatal period (50-65%) - present due to recurrent infx (poor secretion clearance)
• Diagnosis
  • CXR - classically solid areas with cystic areas
    • can be solid mass or one large cyst in appearance
    • often solid appearing at birth until fetal fluid clears
    • if 1st seen with pneumonia in childhood, can resemble pneumatocele
    • CCAM will not clear on follow-up CXR's like pneumatocele
  • CT - with contrast often helpful
  • U/S - extremely helpful if CCAM adjacent to chest wall
  • angiography if necessary to distinguish from sequest.
• Treatment - surgical resection
  • immediate is best in symptomatic infants
  • if noted on fetal U/S then deliver at tertiary care center for immediate resection (o/w prognosis very poor).
  • resp. distress post-op until surrounding atelectatic areas re-expand
  • and hypoplastic lung is replaced by new lung.
  • lobar vs. segmental resection still debated
• Prognosis - good after resection

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Congenital Lobar Emphysema

• Pathophysiology - massively overdistended lobe
  • no bronchial obstruction noted in 50%, intraluminal obstruction in 48%
  • bronchial stenosis, abnormal rotation, mucosal folds, etc.
  • bronchomalacia is most common abnormal
  • will not deflate even with manual compression
  • uniform appearance histologically, normal alveoli anatomically
  • usually only 1 lobe involved, but can be more
  • male:female = 2:1
• Location - LUL > RML/lingula > RUL
  • seldom lower lobes
• Clinical Manifestations - most present in 1st 4 months of life
  • 50% as neonates with severe resp. distress
  • 50% as infants with dyspnea, tachypnea, wheezing, cyanosis, cough
  • older children present with recurrent infx or wheezing (may reflect bronchomalacia)
  • exam c/w unilateral air trapping & compression of contralateral side
• Diagnosis
  • CXR
    • hyperlucent affected side (contains lung markings,unlike cyst)
    • mediastinal shift, contralateral atelectasis, etc.
    • may be fluid filled in neonate initially
    • fluoroscopy - can distinguish CLE from compensatory hyperinflation due to atelectasis
    • once dx made, have to determine whether emphysema is CLE (requiring lobectomy) vs. secondary to obstruction which can be relieved.
  • CT/MRI - to r/o vascular anomalies and other fixable causes of obstruction
  • bronchoscopy (flexible) - to assess for malacia, inspissated mucus, FB in older children
    • only in stable patients
  • V/Q scan - not necessary but can be helpful
    • CLE = matched V and Q defects
    • compensatory emphysema = V and Q are normal
• Differential Diagnosis
  • acquired lobar emphysema of newborn
    • neonates with HMD
    • usually RLL
    • 2 subsets: normal V/Q scans then resolved
    • Ø perfusion then required lobectomy
  • Swyer-James syndrome (unilateral hyperlucent lung)
    • -caused by severe pneumonia
    • -Ø blood flow
  • bronchiolitis obliterans
    • hyperlucency due to Ø blood flow
    • involved lung has normal to Ø volume
    • no contralateral mediastinal shift
• Treatment - immediate lobectomy in infants with progressive resp. distress
  • without surgery, mortality in these infants = 50-75%
  • older children with no or mild sx's can sometimes be managed conservatively
  • most with CHD and CLE need BOTH fixed (in most cases the CLE will not resolve spontaneously after CHD repaired)
  • pos. pressure vent. can worsen sx's therefore initiate PPV immediately prior to thoracotomy
• Prognosis - mortality of surgically treated patients = 7% (mostly due to CHD or hypoxic brain injury)
  • surgically treated patients -some have abnormal PFT's ( FRC, TLC, Ø mid flow rates)
  • most are asymptomatic
  • some may have wheezing (may be due to malacia)

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Arteriovenous Fistula (click on image to see series of images on AVM)

• Pathophysiology - abnormal connection between pulm. arterial and pulm. venous systems
  • can involve systemic circulation
  • most are congenital (40-65% of these have Osler-Weber-Rendu)
  • rarely acquired (trauma, carcinoma, schistosomiasis)
  • 3 types: -single or few discrete AVF's
    • multiple discrete AVF's
    • multiple bilat telangiectasias
    • single lesion found in 65% of cases
• Location - anywhere, but usually lower lobes
• Clinical Manifestations - small shunt then asymptomatic
  • large shunt (2cm diameter or multiple AVF's) then dyspnea on exertion is 1st sx.
  • shunt > 20% of pulm flow
    • dyspnea, cyanosis, polycythemia, clubbing, sx's of hypoxemia and polycy.
    • brain abscess or meningitis
    • continuous murmur, with inspiration, Ø with Valsalva
• Diagnosis
  • CXR - usually well circumscribed lesion
  • CT with contrast can be helpful
  • lung perfusion scan - can miss small AVF's
  • bubble echo
  • angiography - invasive but most sensitive always do both lungs prior to surg.
• Treatment - surgical resection vs. embolization
  • debate as to whether small asymptomatic lesions require tx.

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Congenital Pulmonary Lymphangiectasis

• Pathophysiology - dilated, hypertrophic lymphatic vessels in the lungs
  • 3 types:
    • part of generalized lymphangiectasis - rarest
    • secondary to pulm. venous obstruction (TAPVR or other CHD)
    • primary dev. defect of pulm. lymphatics - most common
• Clinical Manifestations - respiratory distress usually from birth, can be in days to weeks
  • hyperexpansion, tachypnea, retractions, intermittent wheezing, no bronchodilator response, chylothorax, pneumothorax.
  • stiff lungs
• Diagnosis
  • CXR - pulm venous congestion, atelectasis, hyperexpansion, etc.
  • ECG - RAD, RVH, RAE
• Treatment - none
• Prognosis - uniformly fatal in infancy except occasional pts. with systemic lymphangiectasis (occasional long-term survival)

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References

• Burke, et al. Pulmonary arteriovenous malformations: a critical update. 1986. Am Rev Respir Dis, 134:334-339.
• Cooney, et al. "Acquired" lobar emphysema: a complication of respiratorydistress in premature imfants. 1977. J Ped Surg, 12(6):897-903.
• DuMontier, et al. Bronchogenic cysts in children. 1985. Clin Radiol, 36:431-436.
• Hilman. Pediatric Respiratory Disease. 1993. "Congenital Abnormalities." Lierl, Michelle. 457-498.
• Kendig and Chernick. Disorders of the Respiratory Tract in Children. 1990. "Congenital malformations of the lower respiratory tract." Salzberg, Arnold and Krummel, Thomas. 227-267.
  

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