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(Radiology. 1999;212:837-840.)
© RSNA, 1999

Pediatric Imaging

Anterior Chest Wall: Frequency of Anatomic Variations in Children1

Lane F. Donnelly, MD, Donald P. Frush, MD, Joseph N. Foss, MD 2, Sara M. O'Hara, MD and George S. Bisset, III, MD

1 From the Department of Radiology, Division of Pediatric Radiology, Duke University Medical Center, Durham, NC. From the 1998 RSNA scientific assembly. Received July 28, 1998; revision requested October 15; revision received November 3; accepted March 16, 1999. Address reprint requests to L.F.D., Department of Radiology, Children's Hospital and Medical Center and the University of Cincinnati, 3333 Burnet Ave, Cincinnati, OH 45229-3039.


   Abstract
TOP
 Abstract
Introduction
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 References
 
PURPOSE: To evaluate the frequency of anterior chest wall variations in children.

MATERIALS AND METHODS: The computed tomographic (CT) images of 200 consecutive infants and children (114 boys and 86 girls; mean age, 10.5 years; age range, 3 months to 19 years) who underwent chest CT during a 20-month period were evaluated for chest wall variations. Children who had undergone chest wall surgery or were suspected of having a chest wall abnormality were excluded. The frequency of chest wall anomalies was compared with age and sex (Fisher exact test).

RESULTS: The CT scans of 65 children (33%) depicted one or more variations in the anterior chest wall: tilted sternum (n = 29), prominent convexity of anterior rib or costal cartilage (n = 19), prominent asymmetric costal cartilage (n = 20), well-defined paracostal subcutaneous nodule (n = 4), mild pectus excavatum (n = 4), or mild pectus carinatum (n = 4). The frequency of these findings did not vary significantly with age (P = .96) or sex (P = .36).

CONCLUSION: Variations in the anterior chest wall are common, occurring in one-third of children, and should be considered normal. These asymptomatic variations should not be considered alarming when palpated at physical examination.

Index terms: Thorax, abnormalities, 47.1496, 47.1497, 47.92 • Thorax, CT, 47.1211


   Introduction
TOP
 Abstract
 Introduction
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 References
 
Because the chest wall can be involved with either malignancies or severe infections, cross-sectional imaging is often performed to evaluate palpable lesions of the chest wall discovered in children. Although such malignant processes of the chest wall are not common, the presentation for imaging of a child with a "lump" palpated at physical examination is not infrequent. In a previous study (1), in which the results were reviewed for computed tomographic (CT) and magnetic resonance (MR) imaging examinations performed in children referred for evaluation of anterior chest wall lesions, all of the palpated lumps that were asymptomatic were related to anatomic variations of no clinical importance. In our subjective experience, such variations are also seen frequently in children referred for cross-sectional imaging for other indications, when there is no question concerning a chest wall anomaly. If the frequency of chest wall variants is high, these findings should be considered normal when discovered at physical examination and should not be considered alarming to either parents or physicians. The purpose of this study was to evaluate the frequency of chest wall variations in children.


   MATERIALS AND METHODS
TOP
 Abstract
 Introduction
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 References
 
We reviewed the CT scans of 200 consecutive children (114 boys and 86 girls; mean age, 10.5 years; age range, 3 months to 19 years) who underwent CT examination of the chest at our institution over a 20-month period to evaluate chest wall anomalies. Children who had undergone chest wall surgery or were suspected of having a chest wall abnormality were excluded from the study. No other indications prohibited inclusion in the study. The most common indications for CT examination included evaluation for pulmonary metastasis, suspicion of mediastinal mass, follow-up of lymphoma, or evaluations for pulmonary infection in an immunocompromised host, complications of pneumonia, or mediastinal hematoma. Each child was included in the study only once, even if the child underwent multiple chest CT examinations.

All CT examinations were performed with the same type of scanner (CT HiSpeed Advantage; GE Medical Systems, Milwaukee, Wis). Because the examinations were tailored to the specific indication and patient size, the technical parameters varied. Examinations were performed without or with intravenous nonionic contrast material (2.0 mL per kilogram of body weight). Collimation ranged from 5 to 10 mm, and pitch varied from 1.0 to 1.5. All examinations were performed with the patient supine with the arms extended over the head. Breath holding was instigated when possible. All patients underwent imaging from the thoracic inlet superiorly to the level of the adrenal glands inferiorly. In all cases, images were reviewed with various window width and level settings, which always included standard mediastinal and lung settings. In each case, a data sheet pertaining to the presence or absence of chest wall variations was completed by one of four attending pediatric radiologists (L.F.D., D.P.F., S.M.O., G.S.B.) at the time the CT scans were clinically interpreted.

The CT studies in each patient were reviewed for the presence of six variations in the anterior chest wall: (a) tilted sternum, (b) prominent convexity of the anterior rib or costal cartilage, (c) prominent asymmetric costal cartilage, (d) well-defined small (<1 cm) parachondral nodule, (e) pectus excavatum, or (f) pectus carinatum (1). A tilted sternum was considered present when the sternum was not oriented in the horizontal left-to-right axis of the body (Fig 1) (1). The anterior convexity of a rib or costal cartilage was considered prominent when a solitary rib or costal cartilage demonstrated an apex anterior convexity with angulation greater than that of the adjacent superior, inferior, or contralateral ribs and costal cartilage (Fig 2) (1). A costal cartilage was considered asymmetrically prominent when the anteroposterior diameter of one cartilage was more than 3 mm larger than that of the contralateral isolevel cartilage (Fig 2). The presence of a well-defined nodule less than 1 cm in diameter was noted in the subcutaneous fat, immediately adjacent to the sternum or costal cartilage (Fig 3) (1). Pectus excavatum was considered present when the anterior chest wall was prominently concave, with the midline located more posteriorly than the adjacent, more lateral chest wall (Fig 4). Pectus carinatum was considered present when the anterior chest wall was prominently convex with the midline located more anteriorly than the adjacent, more lateral chest wall (Fig 5). A variation was considered not to be present in any case in which the presence of one of the variations was thought possibly to be related to asymmetric positioning of the patient within the scanner or asymmetric positioning of the patient's arms in relationship to the chest.



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  		Figure 1a. Tilted sternum with associated subluxation of the left clavicular head in a 12-year-old girl. (a) Axial CT image shows the sternum (arrow) to be tilted with respect to the horizontal right-to-left axis of the body. The left margin of the sternum is located more anteriorly than the right margin. (b) Shaded-surface three-dimensional CT reconstructed image, obtained for illustrative purposes, shows tilted sternum (arrow) and anteriorly subluxated left clavicular head (arrowhead). The image is displayed as viewed in the axial plane, from the superior perspective, with the anterior region located at the top and the posterior region at the bottom of the image.

 


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  		Figure 1b. Tilted sternum with associated subluxation of the left clavicular head in a 12-year-old girl. (a) Axial CT image shows the sternum (arrow) to be tilted with respect to the horizontal right-to-left axis of the body. The left margin of the sternum is located more anteriorly than the right margin. (b) Shaded-surface three-dimensional CT reconstructed image, obtained for illustrative purposes, shows tilted sternum (arrow) and anteriorly subluxated left clavicular head (arrowhead). The image is displayed as viewed in the axial plane, from the superior perspective, with the anterior region located at the top and the posterior region at the bottom of the image.

 


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  		Figure 2. Right prominent anterior convex costal cartilage and left prominent costal cartilage size in a 9-year-old girl. Axial CT scan shows prominence of the anterior convexity of the right costal cartilage (arrow) and asymmetrically larger left costal cartilage (arrowhead).

 


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  		Figure 3. Small parachondral nodule in a 16-year-old boy. Axial CT scan shows a small (3-mm-diameter) nodule (arrow) in subcutaneous tissues immediately adjacent to the costal cartilage. Such nodules are believed to represent cartilaginous islands (1).

 


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  		Figure 4. Pectus excavatum in a 7-year-old girl. Axial CT scan shows anterior chest wall to be concave. The midline chest wall (arrow) is located more posteriorly than the more lateral chest wall.

 


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  		Figure 5. Pectus carinatum in a 13-year-old boy. Axial CT scan shows apex anterior convexity of anterior chest. The midline chest wall (arrow) is located more anteriorly than the more lateral chest wall. The left hemidiaphragm is elevated secondary to acute phrenic nerve involvement by mediastinal lymphoma. The high-attenuation linear structure in the subcutaneous tissues of the right anterior chest wall represents a central venous catheter.

 
The frequency and type of anterior chest wall variations were compared between subgroups of patients on the basis of age and sex. Statistically significant differences in the frequency of variations between these subgroups was evaluated with a Fisher exact test. A P value of less than .05 was considered statistically significant. The findings at CT were not correlated with physical examination findings after the CT studies were reviewed.


   RESULTS
TOP
 Abstract
 Introduction
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 References
 
The CT scans of 65 (33%) of the 200 patients depicted variations of the anterior chest wall. Variations included tilted sternum (n = 29), prominent convexity of anterior rib or costal cartilage (n = 19), prominent asymmetric costal cartilage (n = 20), well-defined paracostal subcutaneous nodule (n = 4), mild pectus excavatum (n = 4), and mild pectus carinatum (n = 4). More than one variation was noted in 15 of the 65 patients.

The frequency of asymmetric variations among subgroups of patients was evaluated. Variations were depicted in 34 (30%) of the 114 boys and 31 (36%) of the 86 girls. The mean age for patients with variations was 10.8 years as compared to 10.0 years for patients without variations. Among the 200 children, CT scans depicted variations in 13 (33%) of the 39 patients aged 3 months to 3 years, 16 (30%) of the 54 patients aged 4–8 years, 15 (33%) of the 46 patients aged 9–13 years, and 21 (34%) of the 61 patients aged 13–19 years. There was no statistically significant trend between frequency of variations and age (P = .96) or sex (P = .36).


   DISCUSSION
TOP
 Abstract
 Introduction
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
References
 
Because evaluation of abnormalities of the chest wall can be difficult by means of physical examination (2) or radiography (1–7), cross-sectional imaging with either CT or MR imaging is often performed when a chest wall abnormality is suspected. Demonstration of abnormalities of the anterior chest wall at radiography can be more difficult in children than in adults because the bulk of the anterior chest wall is made of nonossified cartilage in children. MR imaging and CT are sensitive in the demonstration of aggressive chest wall lesions, including bone destruction, irregular soft-tissue mass, and pleural effusion (1,3,6,7).

In children, multiple aggressive lesions may involve the ribs and chest wall (3). These include malignancies such as Ewing sarcoma, osteosarcoma, neuroectodermal tumors, leukemia, and metastatic neuroblastoma, and aggressive inflammatory conditions such as osteomyelitis and Langerhans cell histiocytosis (3). In the imaging literature concerning the chest wall in children, most studies have dealt with imaging findings in these aggressive conditions or with pectus excavatum (8–10). Although the normal calcification patterns of costal cartilage in adults older than 30 years have been described (11), other characteristics concerning variations in shape and configuration of the anterior chest wall have not been described, to our knowledge.

In a previous study, a population of children suspected of having anterior chest wall lesions was evaluated with cross-sectional imaging (1). In that study, all patients who had clinically important abnormalities, such as malignancy or infection, indicated pain or tenderness at physical examination. In asymptomatic children, however, the cause of the palpable abnormality was always a benign variation in the anterior chest wall. Therefore, benign history and physical examination results have a high negative predictive value for excluding important abnormalities. In this study, we evaluated a population of children who were not suspected of having chest wall abnormalities and underwent CT of the chest for other indications. One-third of the children had these variations in the anterior chest wall. These findings (in the population of children in our study, who were considered to have normal chest walls) are probably not different from those in the patients who were referred with palpable "bumps" in the previous study (1). The only difference may be that in the latter group, these variations were brought to attention by the child, parent, or physician after noticing the area at physical inspection.

Slight variations in the configuration of the costal cartilage, ribs, and sternum are commonly encountered in children and should be considered normal. When these variations in anatomy are encountered at physical examination, they should not be considered alarming. Unless the patient has pain or an underlying illness that predisposes them to a chest wall process (such as immunodeficiency, previous chest wall surgery, or a source of metastatic disease), cross-sectional imaging or ultrasonography is most likely not necessary.

Because of the potential for asymmetric somatic growth to play a role in the frequency of such normal variations in children, we suspected that there might be a higher frequency in children during ages of rapid growth. However, there were no age groups in which there was a higher frequency of variations. In addition, there was no statistically significant difference in the frequency between boys and girls. In all age and sex groups, the frequency was always approximately 33%.

The majority of variations encountered in this study were mild in degree and would not have raised the possibility of a pertinent abnormality with most radiologists. Our goal was not to suggest that there is an epidemic of chest wall variations suddenly elucidated by our interpretations of CT scans. We emphasize that we are not advocating the use of CT to evaluate for these normal variations. Our goal was to use information available on CT studies performed for other reasons to evaluate the frequency of such variations. It is only when such a variation is detected at physical examination and raises the issue of a pathologic process that knowledge of these aberrations has clinical relevance.

In conclusion, variations in the anterior chest wall are common, occurring in one-third of children, and should be considered normal. Findings in a previous study (1) have shown that normal variants of the chest wall, which are of no clinical importance, are usually the cause of asymptomatic "bumps" that are recommended for imaging evaluation. The high frequency of these normal aberrations should be considered when contemplating imaging in a child with an asymptomatic chest wall "lump."


   Acknowledgments
 
We thank David M. Delong, PhD, for his help with the statistical analysis.


   Footnotes
 
2 Current address: Department of Radiology, Arnold Palmer Hospital for Children and Women, Orlando, Fla. Back

Author contributions: Guarantor of integrity of entire study, L.F.D.; study concepts and design, L.F.D.; definition of intellectual content, L.F.D.; literature research, L.F.D.; data acquisition and analysis, all authors; manuscript preparation, L.F.D.; manuscript editing and review, all authors.


   References
TOP
 Abstract
 Introduction
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 References
 

  1. Donnelly LF, Taylor CNR, Emery KH, Brody AS. Asymptomatic, palpable, anterior chest wall lesions in children: is cross-sectional imaging necessary?. Radiology 1997; 202:829-831.[Abstract/Free Full Text]
  2. Hatfield MK, Gross BH, Glazer GM, Martel W. Computed tomography of the sternum and its articulations. Skeletal Radiol 1984; 11:197-203.[Medline]
  3. Faro SH, Mahroubi S, Ortega W. CT diagnosis of rib anomalies, tumors, and infection in children. Clin Imaging 1993; 17:1-7.[Medline]
  4. Brossmann J, Stabler A, Preidler KW, Trudell D, Resnick D. Sternoclavicular joint: MR imaging–anatomic correlation. Radiology 1996; 198:193-198.[Abstract/Free Full Text]
  5. Goodman LR, Teplick SK, Kay H. Computed tomography of the normal sternum. AJR 1983; 141:219-223.[Abstract/Free Full Text]
  6. Destouet JM, Gilula LA, Murphy WA, Sagel SS. Computed tomography of the sternoclavicular joint and sternum. Radiology 1981; 138:123-128.[Abstract/Free Full Text]
  7. Gouliamos AD, Carter BL, Emami B. Computed tomography of the chest wall. Radiology 1980; 134:433-436.[Abstract/Free Full Text]
  8. Maddern IR, Goodman LR, Almassi GH, Haasler GB, McManus RP, Olinger GN. CT after reconstructive repair of the sternum and chest wall. Radiology 1993; 186:665-670.[Abstract/Free Full Text]
  9. Lancaster L, McIlhenny J, Rodgers B, Alford B. Radiographic findings after pectus excavatum repair. Pediatr Radiol 1995; 25:452-454.[Medline]
  10. Ellis DG. Chest wall deformities in children. Pediatr Ann 1989; 18:161-165.[Medline]
  11. Ontell FK, Moore EH, Shepard JA, Shelton DK. The costal cartilage in health and disease. RadioGraphics 1997; 17:571-577.[Abstract]



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