The Chest Wall

Etiology.

Most asymptomatic palpable anterior chest wall lesions in pediatric patients are normal anatomic osseous or cartilaginous variants, most commonly a prominent anterior convexity of a solitary rib, costal cartilage, or sternal tilt ( Fig. 59.1 ). These normal anatomic variations occur in approximately one-third of children. Symptoms that may raise concern and require further evaluation are focal pain and rapid growth of the mass.

Imaging.

In the case of a palpable but otherwise asymptomatic anterior chest wall lesion in children, a chest radiograph with a BB marker is usually adequate to exclude a potentially aggressive or malignant underlying condition. When chest radiographic findings are equivocal, ultrasound can be performed. To minimize ionizing radiation exposure, computed tomography (CT) should be reserved for situations in which further characterization is still necessary after radiographic and ultrasound evaluation. Magnetic resonance imaging (MRI), which is not associated with ionizing radiation exposure, is a particularly helpful imaging modality for confirming and characterizing congenital and developmental chest wall lesions.

Treatment and Follow-up.

If the diagnosis of an anterior chest wall developmental variant can be made confidently by imaging studies in asymptomatic infants and children, no further treatment or follow-up is necessary.

Etiology.

Two of the most common abnormalities of the chest wall are pectus excavatum and pectus carinatum, with the former being the most common congenital deformity of the sternum and the most common sternal deformity requiring surgery. The current leading theory for the development of pectus excavatum is a misdirected, rapid growth of the lower costal cartilages. Such abnormal growth of the lower costal cartilages, which often intensifies during growth spurts, displaces the sternum either inward or outward, resulting in pectus deformity. Pectus excavatum occurs in between 1 in 400 and 1 in 1,000 live births. In children with pectus excavatum, the inferior aspect of the sternum is depressed inward, resulting in varying degrees of anterior chest wall concavity and anterior protrusion of the costochondral junctions. Although most cases of pectus excavatum are isolated, approximately 45% of cases are familial.

Pectus carinatum is a less common chest wall deformity that occurs in approximately 1 in 1,500 live births and has a familial occurrence of approximately 25%. In children with pectus carinatum, outward displacement of the sternum occurs, with secondary abnormal protrusion of the ribs.

Pectus deformities may occur in association with scoliosis (more frequently with pectus excavatum), Marfan syndrome, Ehlers – Danlos syndrome, Poland syndrome, and congenital heart disease. In addition to cosmetic issues, severe pectus deformities also can cause chest pain, dyspnea, palpitations, and restrictive lung disease.

Imaging.

On frontal chest radiographs, the sternal depression of pectus excavatum may cause a pseudoinfiltrate over the right side of the heart and various degrees of leftward cardiac shift. On the lateral chest radiograph, the sternal depression causes narrowing of thoracic anteroposterior (AP) diameter ( Fig. 59.2 ). Pectus carinatum usually is diagnosed on a lateral chest radiograph, which shows an increased AP diameter of the thoracic cavity and an extended retrosternal space ( Fig. 59.3 ).

The Haller or pectus index is used to estimate the severity of pectus excavatum. It is calculated from an axial CT image by dividing the maximum transverse dimension of the thorax from the inner aspect of the ribs by the AP dimension of the thoracic cavity at its narrowest point ( Fig. 59.4 ). A pectus index greater than 3.25 in symptomatic pediatric patients typically initiates corrective surgery, whereas an index less than 2.56 is considered normal. Recent studies have advocated the use of chest radiographs instead of CT to preoperatively evaluate the severity of the deformity. In more severe cases, the use of a limited, low-dose CT scan with selective five to seven axial CT images through the deformity can be obtained to generate the pectus index. When the primary purpose of imaging is to assess the Haller index, axial MRI can be used to avoid ionizing radiation.

Treatment and Follow-up.

Severe pectus deformity requires surgical correction, particularly in symptomatic pediatric patients. The Ravitch procedure for pectus excavatum includes resection of deformed cartilages and correction of the sternum by a wedge osteotomy in the upper sternal cortex. In the Nuss procedure, a convex metal bar is placed behind the sternum, pulling the sternum anteriorly. The Nuss procedure has a 4% to 11% complication rate (infection and dislocation of the metallic bar are most common), and thus follow-up imaging is necessary to monitor the implanted bar and its complications. Corrective surgery for pectus carinatum also requires costochondral resection and a wedge osteotomy, but the sternum is pushed inward.

Etiology.

Cleidocranial dysostosis is a rare syndrome usually caused by an autosomal dominant gene mutation (CBFA1) with a high degree of penetrance and variable expression. The triad of partial or complete absence of the clavicles, supernumerary or impacted teeth, and delayed fontanel closure is highly suggestive of this syndrome. Other features include midface hypoplasia, short stature, and pelvic and distal phalangeal hypoplasia that causes brachydactyly.

Imaging.

Typical chest radiographic findings include a bell-shaped thorax, short ribs, and either complete or partial absence of the clavicles ( e-Fig. 59.5 ). When the clavicle is partially absent, the distal portion of the clavicle usually is involved. Scoliosis may be present. Because many of the characteristic manifestations only become evident during adolescence, early clinical diagnosis may be difficult and often requires a skeletal survey. Other features of the syndrome can support the diagnosis.

Treatment and Follow-up.

Multidisciplinary management by a team of specialists including pediatricians, geneticists, and orthodontists is the optimal approach for patients with cleidocranial dysostosis. Genetic counseling is recommended. No imaging follow-up is required once the diagnosis has been made.

Etiology.

Poland syndrome is a form of chest wall and breast hypoplasia that occurs in 1 in every 20,000 to 30,000 live births. The syndrome includes absence of the pectoralis muscles and ipsilateral syndactyly. Other associations include rib aplasia, amastia/athelia, and absence of axillary hair. Poland syndrome typically is unilateral and (more often) sporadic and occurs more frequently in boys than in girls, with a ratio of 2 : 1 to 3 : 1. The tendency toward unilaterality (with the right side affected more frequently than the left side) has raised the hypothesis that this anomaly is perhaps a result of interrupted or insufficient blood supply during limb bud development in the sixth week of gestation. Poland syndrome is diagnosed clinically by the apparent asymmetry of the chest wall ( e-Fig. 59.6 ) and syndactyly. Cardiopulmonary impairment and functional deficiency of the shoulder, although rare, also can be present.

Imaging.

On chest radiographs, hyperlucency of the affected hemithorax is usually apparent in unilateral cases because of the absent pectoralis muscle and breast ( Fig. 59.7 ). Because the extent of involvement is difficult to assess with clinical examination or chest radiographs, cross-sectional imaging with CT or MRI is useful ( Fig. 59.8 ). Furthermore, it is imperative to preoperatively assess the presence of all of the chest wall and anterior abdominal wall muscles, because muscle flaps are used in surgical reconstruction.

Treatment and Follow-up.

Corrective surgery often is performed for cosmetic reasons, particularly in girls. Such surgery includes (1) restoration of the structural integrity of the rib cage and (2) improvement in the appearance of the chest by performing transposition of musculocutaneous flaps (most commonly with latissimus dorsi and rectus abdominis muscles), as well as concomitant breast implants in female patients.

Etiology.

Bacterial infections of the chest wall are rare in children. The common organisms that cause bacterial infections of the chest wall are Staphylococcus aureus and Salmonella species in persons with sickle cell disease. Sternal osteomyelitis may occur in patients with an underlying disease, such as immunodeficiency and hemoglobinopathies. Rib osteomyelitis is most commonly acquired by direct spread from an adjacent pneumonia or empyema. Empyema necessitans is a rare complication of empyema characterized by the extension of the infection from the pleural space into the chest wall. Pediatric patients with a bacterial chest wall infection often present with focal soft tissue erythema, edema, and pain. Additionally, other signs of infection, such as leukocytosis and elevated erythrocyte sedimentation rate, often are present.

Imaging.

Chest radiographs may reveal localized soft tissue edema in cases of cellulitis or fasciitis. Bone changes such as periosteal reaction or lytic or sclerotic lesions can be present, particularly in the late stage of disease. Concomitant pulmonary consolidation, empyema, and subcutaneous emphysema also may be present. Ultrasound, CT, and MRI are more sensitive than chest radiographs in detecting and characterizing chest wall infections. Ultrasound should be reserved for superficial and more localized chest wall infections because of the limited field of view ( Fig. 59.9A ). The extent of the chest wall infection is best demonstrated on CT or MRI. For evaluation of chest wall abscess and bone marrow edema in the earlier stage of osteomyelitis, MRI is the most sensitive imaging modality ( Fig. 59.9B ). CT is the imaging modality of choice for evaluating concomitant pulmonary parenchymal infection.

Treatment and Follow-up.

Antibiotics are administered to treat bacterial chest wall infections. In cases of abscesses localized to the chest wall or empyema, drainage may be necessary to relieve the focus of infection and avoid further spread. Prolonged antibiotic therapy is necessary for cases of osteomyelitis. Evaluation of response to treatment by monitoring C-reactive protein in pediatric patients with osteomyelitis has dramatically decreased both the average duration of therapy and the need for follow-up imaging.

Etiology.

Tuberculosis (TB) is a potentially deadly infectious disease caused by various strains of mycobacteria, usually Mycobacterium tuberculosis in humans. Tuberculosis infection of the chest wall often is a result of the hematogenous spread of pulmonary TB infection. However, tuberculosis of the chest wall also can occur as an isolated primary infection with no evidence of pulmonary disease, although this presentation is rare. Skeletal TB infection accounts for 10% to 20% of extrapulmonary cases and 1% to 2% of all TB infection cases. Affected patients present with a slow-growing soft tissue chest wall mass, often without associated pain or fever. Respiratory symptoms may be present in cases of lung involvement.

Imaging.

TB infection can involve any bone of the chest wall; however, the ribs are most commonly affected. On radiographs, osseous TB infections are usually lytic and sharply marginated. Associated periosteal reaction is a relatively rare finding. On CT or MRI, TB chest wall infections usually present as a rim-enhancing chest wall mass. CT and MRI can play an important role in demonstrating bone involvement from a chest wall TB infection that may not be seen on radiographs. Expansion and destruction of the bone with an adjacent soft tissue mass from a TB infection of the chest wall may mimic an underlying malignancy.

Treatment and Follow-up.

Treatment of chest wall TB infection currently is not well established. Some advocate at least 6 months of antituberculous medication, whereas others suggest more aggressive management consisting of surgical excision of affected bones and soft tissues, in addition to preoperative and postoperative antituberculous medication regimens.