Bifid rib - usefulness of chest ultrasound. A case report.

The paper presents the possibility of using ultrasonography in the diagnosis of a congenital rib anomaly in the form of bifid rib. Bifid rib is a rare congenital abnormality of anterior chest wall. It manifests as a chest "lump." Such lesions are detected during a routine physical examination or chest X-ray which is often performed for other reasons. The overall prevalence of bifid rib is estimated at 0.15% to 3.4% (mean 2%) and it accounts for approximately 20% of all congenital rib anomalies. It is usually an unilateral lesion. The cases presented herein constitute the first pediatric cases in the available literature in which bifid rib anomaly was visualized by ultrasound examination.

The paper presents five cases of bifid rib with the discussion on the usefulness of the ultrasound examination (US) in the diagnostic process.

Case reports

Case 1

A three-year-old boy was referred to the oncological clinic due to a lesion localized in the left midclavicular line in the region of the fourth intercostal space. The lesion did not cause pain. Laboratory tests (tab. 1) and imaging examinations (chest X-ray and US) were performed. The result of the X-ray was unclear (fig. 1) and the chest US examination revealed bifurcation of the costal cartilage of the fourth left rib (fig. 2).

Tab. 1

Results of the laboratory tests and the type of imaging examinations performed in individual patients

Patient	Imaging examinations	Laboratory tests
1.	X-ray, US	Complete blood count (n), ALP (n), calcium-phosphorus metabolism (n)
2.	X-ray, US	Complete blood count (n), creatinine (n), UA (n), eGFR (n), Na (n), K (n), LDH (n), coagulation profile, ALP (n), aHCV (n), HBsAg (n)
3.	US	(-)
4.	US, X-ray	(-)
5.	US, X-ray	Complete blood count (WBC ↑, Lymph ↑), IgM EBV (+), AST (n), ALT (n), GGTP (n), LDH (n)

(n) – normal result; ALP – alkaline phosphatase; UA – uric acid; eGFR – estimated glomerular filtration rate; Na – sodium; K – potassium; LDH – lactate dehydrogenase; aHCV – hepatitis C antibody, HBsAg – hepatitis B surface antigen; (-) – laboratory tests were not performed; WBC ↑ – elevated leukocyte level; Lymph ↑ – elevated lymphocyte level, IgM EBV (+) – positive antibodies to the Epstein-Barr virus; AST – aspartate aminotransferase; ALT – alanine aminotransferase; GGTP – gamma-glutamyl transpeptidase.

Fig. 1

Chest X-ray – normal image

Fig. 2

Bifurcation of the costal cartilage of the fourth left rib (arrows)

Case 2

A five-year-old boy was referred to the oncological clinic due to a lesion localized on the anterior chest wall on the left side in the region of the fifth rib. The lesion did not cause pain. Laboratory tests (tab. 1) and imaging examinations (chest X-ray and US) were conducted. The X-ray revealed bifurcation of the fifth rib (fig. 3). The US examination confirmed the diagnosis.

Fig. 3

Chest X-ray – bifurcation of the fifth left rib

Case 3

A six-year old boy was referred to hospital due to four painless lumps localized bilaterally on the anterior chest wall in the region of the fourth and fifth ribs. The patient underwent a US examination (tab. 1) which revealed bifurcation of the costal cartilage of the fourth (bilaterally) and fifth (bilaterally) ribs.

US examination – bifurcation of the fifth left rib

US examination – bifurcation of the fifth left rib

Bifurcation of the costal cartilage of the fourth and fifth left ribs

Bifurcation of the costal cartilage of the fourth and fifth right ribs

Bifurcation of the cartilage of the fourth right rib (arrows)

Case 4

A seven-year-old boy was referred to the Pediatric Oncology Clinic due to a lesion localized in the right parasternal line in the region of the fourth rib. The palpated lesion was hard and painless. The results of the chest X-ray were unclear and the chest US examination demonstrated bifurcation of the costal cartilage of the fourth rib.

Case 5

A four-year-old boy was referred to the Pediatric Hematology and Oncology Clinic due to lymphadenopathy, hepatomegaly and splenomegaly for further diagnosis and to rule out a proliferative disease. Based on additionally performed examinations, the diagnosis of the infection with the Epstein-Barr virus was established. Moreover, the chest X-ray and US examinations revealed bifurcation of the left fifth rib (fig. 9).

Fig. 9

Bifurcation of the fifth left rib

Discussion

The cases presented above are the first cases in the available literature in which bifid rib anomaly was diagnosed by chest ultrasound in children. Bifid rib is a rare congenital abnormality of the anterior chest wall. It manifests as a painless “lump” of the chest wall. A single bifid rib is most commonly a normal incidental finding discovered during a routine physical examination and/or chest radiography which is often performed for other reasons(. The overall prevalence of bifid rib is estimated at approximately 0.15% to 3.4% (mean 2%) and it accounts for approximately 20% of all congenital rib anomalies(. It is usually unilateral( and more frequently occurs in men(. The fourth rib has been reported to be the most commonly bifid(. This congenital anomaly may occur sporadically as an isolated defect or may be seen in several genetic disorders such as Gorlin-Goltz syndrome(. It is a multisystem disorder that occurs predominantly in the white race. It is autosomal dominant condition( characterized by the anomalies of the skeletal system (bifid rib in 60–70% of cases, maxillary and mandibular cysts), nervous system and skin lesions (numerous basal cell nevi, epidermoid cysts)(. The incidence of this syndrome is 1 per 600,000 live births(.

The X-ray examination is useful in the diagnosis of congenital anomalies of the rib cage. However, in the case of bifid rib, this method has certain limitations due to a more difficult assessment of the cartilage and parasternal region (case 2 and 3). The presented cases demonstrate that sonography allows for a more accurate assessment of bifid rib than the X-ray, particularly in the parasternal region. It also enables cartilage assessment.

Conclusions

The US examination of the rib cage in pediatric patients is a useful tool for diagnosis rib lesions. It enables assessment of the periosteum and costal cartilage, moreover, it gives rapid and precise answer whether the lump is a congenital anomaly and specify its type.