The Egyptian Journal of Radiology and Nuclear Medicine (2014) 45, 689–694

Egyptian Society of Radiology and Nuclear Medicine

The Egyptian Journal of Radiology andNuclearMedicine

www.elsevier.com/locate/ejrnmwww.sciencedirect.com

ORIGINAL ARTICLE

Abnormalities of fetal rib number

and associated fetal anomalies using three

dimensional ultrasonography

* Corresponding author. Address: 65 Salah Salem St, Qwuesna,

Elmenufia, Egypt. Tel.: +20 1118030044; fax: +20 482573465.

E-mail addresses: samehkhodair@gmail.com (S.A. Khodair),

omarhassanien@yahoo.com (O.A. Hassanen).1 Tel.: +20 1202006808.

Peer review under responsibility of Egyptian Society of Radiology and

Nuclear Medicine.

0378-603X � 2014 Production and hosting by Elsevier B.V. on behalf of Egyptian Society of Radiology and Nuclear Medicine.

http://dx.doi.org/10.1016/j.ejrnm.2014.03.009Open access under CC BY-NC-ND license.

Sameh Ahmad Khodair *, Omar Ahmad Hassanen1

Radiology Department, Faculty of Medicine, Tanta University, Egypt

Received 28 December 2013; accepted 19 March 2014Available online 24 April 2014

KEYWORDS

Ribs;

Three-dimensional imaging;

Fetal ultrasonography;

Congenital abnormality

Abstract Aim: To determine incidence of abnormal number of fetal ribs and its association with

other fetal anomalies using 3D ultrasonography.

Materials and methods: A prospective study conducted on 188 singleton pregnant women searching

for fetal anomalies including the incidence of abnormal number of fetal ribs and other anomalies.

Static 3D volumes with volume contrast imaging using spine map were used. Rendered images were

displayed and the ribs were counted.

Results: 173 fetuses (92%) were having normal number of ribs. Fifteen fetuses (8%) were found to

have abnormal number of ribs; ten fetuses (5.3%) had 11 ribs. On the other hand five fetuses (2.7%)

had supernumerary 13 ribs. Eight fetuses (4.2%) were having abnormal number of ribs with no

associated anomalies (isolated abnormal number). Seven fetuses (3.7%) in this study had associated

anomalies.

Conclusion: Abnormal number of fetal ribs more to be an isolated finding (4.3%) but it may also be

seen with other anomalies (3.7% in this study). 3DUS is useful for scanning the fetal ribs in the mid

trimester of the pregnancy for early detection of associated genetic aberrations.� 2014 Production and hosting by Elsevier B.V. on behalf of Egyptian Society of Radiology and Nuclear

Medicine. Open access under CC BY-NC-ND license.

1. Introduction

Fetal malformations are variable regarding their types and

severity. According to recent statistics, fetal anomalies occurin about 2–3% of the new born in the developed countries (1).

Fetal thoracic anomalies are relatively less common and

most of them could be detected by the standard prenatal twodimensional (2D) ultrasound examinations especially afterthe recent technical improvements in 2D equipments and theircolor Doppler applications (2–3).

690 S.A. Khodair, O.A. Hassanen

A wide range of fetal rib abnormalities are present involv-ing their shape, length and number in addition to fracturesand unusual articulation of the ribs (4). The abnormal ribs

may be an isolated entity or often a part of congenital disorderor other syndromes e.g. trisomy 21 with unilateral agenesis ofthe 12th rib (5–6). Ultrasound is still the method of choice and

most often used in screening the anomalies of growing fetus, asit is cheap, available and non- invasive (7) The advent of three-dimensional ultrasound (3DUS) technology, allowed easier

assessment of both morphological and pathological character-istics of fetal ribs in vivo. The whole body could be visualizedand volume reconstruction could be done (8–10). On the otherhand, the volume contrast imaging (VCI) technique used with

3D sonography had improved both bone and soft tissue con-trast while the reformatting coronal plane has been appliedto count the number of the Ribs (11–13).

2. Materials and methods

A prospective study was conducted on 188 consecutive single-

ton low risk pregnant women searching for fetal anomaliesincluding the incidence of abnormal number of fetal ribs eitherisolated or co-incidence with other anomalies.

Research Ethics Committee approval and informed consentwere obtained. Patients were referred in the period between

Table 1 The associated anomalies and their ratios.

System Malformations n (%) Type of anomalies

Urinary system 4 (40%) MCDK (2)

PUJO (1)

P. urethral valve (1)

CNS 3 (30%) Anencephaly (2)

Ventriculomegaly (1)

GIT 1 (10%) Jejunal atresia (1)

Others 2 (20%) Clubfoot (1)

Omphalocele (1)

Total 10 (10)

Table 2 The relationship between abnormal number of ribs in (7)

Eleven

Bilateral

(3 patient

1.6%

Anomalies

(2) MCDK

(Multi-cystic dysplastic kidney) – urinary

(1) Pelvi-ureteric Junction obstruction (PUJO) – urinary 1

(1) Posterior urethral valve – urinary 1

(2) Anencephaly – (CNS) 1

(1) Ventriculomegaly (CNS)

(1) Jejunal atresia (GIT) 1

(1) Clubfoot (others)

(1) Omphalocele (others) 1

Total 5

Aug. 2012 and Sept. 2013 for either routine prenatal examina-tion or for further assessment of fetal anomalies. All womenvolunteered to undergo 3DUS after being fully informed with

the study protocol, technique and time of examination. Inclu-sion criteria were singleton pregnancy and a match betweenthe ultrasound calculated fetal gestational age and the gesta-

tional age calculated based on the Last Menstrual Period(LMP) of the patient. Exclusion criteria were diabetic mothers,fetal growth retardation or over growth and oligohydramnios.

2.1. Fetal 3DUS examination

Examinations were performed during one of two periods sched-

uled for routine fetal anomaly scans, either at the early secondtrimester (14–16 weeks) and this was done in 98 patients or at20–24 weeks of gestation which was done in 90 patients.

All examinations were performed by using a commercially

available Ultrasonography scanner (Voluson 730 Pro; GE,Milwaukee, WI) equipped with a 4–8 MHz abdominal probefor 3-dimensional volume scanning which was used to assess

the fetal ribs. Data sets of the fetal ribs were acquired eitherwith static 3D volumes using the skeleton map or with volumecontrast imaging using spine map. Static 3D volumes were

taken with a sagittal sweep over the fetal thorax and abdomenand displayed in the antero-posterior projection. The acquisi-tion time was 2–4 s per volume, and acquisition was performedonly in the absence of fetal movement with the fetal back fac-

ing up toward the transducer. In order to obtain clear andobvious rendered images, the region of interest in the multipla-nar images was reduced as much as possible and the threshold

values were also adjusted accordingly. Three to four volumedatasets were obtained for each spine. Both multiplanar andrendered images were displayed simultaneously and the ribs

were counted on the rendered image only. Regarding the vol-ume contrast imaging (VCI) thickness around 15 mm was used(varying according to gestational age). The spine was lined up

in the sagittal plane, and the locator line was positioned alongthe spine. The VCI displayed with the spine map used a 100%maximum intensity mode with the low threshold set at 20.

fetuses with associated anomalies.

Number of ribs N (%)

ribs (5 patients)

2.7%

Thirteen ribs (2 patients)

1.1%

s)

Unilateral

(2 patients)

(1.1%)

Bilateral

(2 patients)

1.1%

Unilateral

(0 patients)

0%

1

Unilateral

MCDK

1

Bilateral

MCDK

1

1

1

2 3 Total

10

Abnormalities of fetal rib number and associated fetal anomalies 691

For post-processing, volumes were stored and subsequentlyanalyzed on an offline personal computer with 4D View soft-ware version 5.0 (GE Healthcare).

3. Results

This study included 188 singleton low risk pregnant women, 98

women examined at the early second trimester (14–16 weeks)and the other 90 women were examined at 20–24 weeks ofgestation.

In this study, 173 fetuses (92%) were having normal num-ber of ribs; twelve paired ribs.

Fifteen fetuses (8%) were found to have an abnormal num-

ber of ribs; ten fetuses (5.3%) had 11 ribs with missing of thelast 12th rib either unilaterally in four fetuses (2.1%) or bilat-erally in six fetuses (3.2%).

On other hand five fetuses (2.7%) had supernumerary 13 ribs;two fetuses (1.1%) had 13 pairs of ribs and three fetuses (1.6%)had unilateral 13 ribs with an extra rib after the last 12th rib.

(15) patients with abnormal

number of ribs (8%)

(10) patients with

11 ribs (5.3%)

(5) patients with

Supernumerary 13 ribs(2.7%)

(3) patients with unilateral 13 ribs (1.6%)

(4) patients with unilateral11 ribs ( 2.1%)

(6) patients with bilateral11ribs (3.1%)

(2) patients with bilateral 13 ribs (1.1%)

Eight fetuses (4.2%) were having abnormal number of ribs withno associated anomalies (isolated abnormal number).

Seven fetuses (3.7%) in this study had associated anoma-lies, five of them (2.7%) showing 11 ribs (three unilateraland two bilateral), while the other two fetuses (1%) were with

supernumerary ribs.The total associated anomalies included in this study were

ten anomalies. Urinary system anomalies were the most fre-

quent in this study as four renal anomalies (40%) were present;two multicystic dyspalstic kidney (MCDK), one pelvi-uretericjunction obstruction (PUJO) and one posterior urethral valve.CNS anomalies were the second associated anomalies, as three

anomalies (30%) were present; anencephaly in two fetuses andventriculomegaly in one fetus. One associated anomaly of theGIT (10%) was present (jejunal atresia) in one fetus, Other two

anomalies (20%) were present one was clubfoot and the otherwas omphalocele (Table 1).

The seven fetuses with abnormal rib number were having

ten congenital anomalies either involved one system or

concomitant more than one system anomalies. The first fetuswas having bilateral MSDK with bilateral supernumerary 13ribs. The second fetus was having unilateral MSDK with uni-

lateral eleven ribs. The third fetus was having unilateral PUJOwith posterior urethral valve and associated bilateral elevenribs. The forth fetus was having anencephaly, and omphalocele

with associated bilateral eleven ribs. The fifth fetus was havingjejunal atresia with bilateral eleven ribs. The sixth fetus washaving ventriculomegaly with club feet and associated bilateral

13 paired ribs. The seventh fetus was having anencephaly withunilateral eleven ribs (Table 2 and Figs. 1–6).

4. Discussion

Many and different variations are existent in the human ribs.Some of these variations are common and frequently seen

including asymmetric or supernumerary ribs, in addition tofusion or absence of some ribs (14).

Abnormalities in the ribs may be isolated such as cervicalribs or abnormal number of the ribs and usually pass

unnoticed. This is because prenatal scanning of the ribs ismainly performed in the presence of other associated anoma-

lies and not as a routine work (15–17). On the other hand,the importance of prenatal assessment of fetal rib anomaliesis due to their co-association with skeletal dysplasia and anom-

alies of other systems (4). To our knowledge, this is the firstprospective prenatal study about the incidence of abnormalrib number associated with other anomalies using three & four

dimensional ultrasonography.In this study, 188 consecutive singleton low risk pregnant

women underwent 3D and 4D ultrasonography, 15 patientswere found to have abnormal number of ribs representing

8%, this result is matching with Lorder et al. (18) who statedincidence of abnormal rib number ranging between 1.4 and8%. The most clinical significance of abnormal rib number is

its association with chromosomal and genetic aberrations.Esser et al. (6) stated that trisomy 21 is usually associated withabnormalities of the thoracic cage and the two common tho-

racic anomalies are multiple sternal ossification centers and

Fig. 1 3DUS maximal mode rendered image of normal twelve

pairs of ribs of fetus aged 24 weeks.

Fig. 2 3DUS maximal mode rendered image of normal twelve

pairs of ribs of fetus aged 16 weeks.

Fig. 3 3DUS image showing 13 ribs unilaterally (arrows), the

13th rib being on the left side of the fetus (arrow).

Fig. 4 3DUS image showing fetus with anencephaly (arrow), the

fetus was having 11 pairs of ribs.

692 S.A. Khodair, O.A. Hassanen

11 pairs of ribs. According to their results, the incidence of 11

pairs of rib in neonates with trisomy 21 is 28–33%, in ourstudy we had 10 fetuses showing 11 ribs, three of them (repre-senting 30%) were proved to have trisomy 21 on the basis of

both clinical and genetic studies. The characteristic short andbroad hands with short stubby fingers are evident on threeand four dimensional ultrasonographic examinations.

In our study supernumerary ribs were present in (5) fetuses

with an extra rib after the 12th rib. This represents (2.7%) allfetuses examined in this study. Three fetuses (1.6%) had extraribs unilaterally, while the other (2) fetuses (1.1%) had bilat-

eral supernumerary ribs. Our results are relatively differentfrom those mentioned by Hershkovitz (19), in his study; unilat-eral 13 ribs were found in 0.3% of the patients and bilateral

extra ribs in 0.54% of the patients. These differences in theresults may be related to the less number of the patients in

our study. Seven patients (3.7%) in this study were associated

with anomalies of the other organs; five of them associatedwith 11 ribs, while the other two patients were associated withsupernumerary ribs. The total additional anomalies included

in this study were ten (10) anomalies in the seven patients assome patients had more than one anomaly. Urinary systemanomalies were the most common associated anomaly in thisstudy. Four associated urinary anomalies (40%) were present,

two multicystic dyspalstic kidney (MCDK), one pelvi-uretericjunction obstruction (PUJO) and one posterior urethral valve.CNS anomalies were the second associated anomalies, as three

anomalies (30%) were present, anencephaly in two fetuses andventriculomegaly in one fetus. In a previous retrospectivestudy done by Gindes et al. (13), cardiac anomalies were

the common associated anomalies representing 45% of the

Fig. 5 3DUS image showing fetus with bilateral club feet, the fetus was having 13 pairs of ribs.

Fig. 6 3DUS image showing fetus with trisomy 21 facial features and stubby fingers, the fetus was having 11 pairs of ribs.

Abnormalities of fetal rib number and associated fetal anomalies 693

associated anomalies followed by renal anomalies representing36% of the all associated anomalies.

One limitation of this study was the small number of theincluded fetuses showing abnormal rib number, with a subse-quent decrease in their associated anomalies (only in 7

patients). This is because the study was a prospective study.

5. Conclusion

Abnormal number of fetal ribs more to be an isolated finding(4.3%) but it may also be seen with other anomalies (3.7% inthis study). 3DUS and 4DUS are easily applied technologiesand are useful for the clinical evaluation of fetuses with tho-

racic anomalies including abnormal rib number.We recommend routine scanning of the fetal ribs in the mid

trimester of the pregnancy for early detection of associated

genetic aberrations.

Source(s) of support

No.

Presentation at a meeting

No.

Conflicting interest

The authors declared that there is no conflict of interest.

References

(1) Kouame N, N’goan-Domoua AM, Nikiema Z, et al. Polyhy-

dramnios: a warning sign in the prenatal ultrasound diagnosis of

foetal malformation? Diagn Interv Imaging 2013; 94: 433–7

[PMID: 23403339. doi: 0.1016/j.diii.2013.01.002].

(2) Achiron R, Zalel Y, Lipitz S, et al. Fetal lung dysplasia: clinical

outcome based on a new classification system. Ultrasound Obstet

Gynecol 2004;24:127–33.

(3) Achiron R, Hegesh J, Yagel S. Fetal lung lesions: a spectrum of

disease. New classification based on pathogenesis, two dimen-

sional and color Doppler ultrasound. Ultrasound Obstet Gynecol

2004;24:107–14.

694 S.A. Khodair, O.A. Hassanen

(4) Glass RB, Norton KI, Mitre SA, et al. Pediatric ribs: a spectrum

of abnormalities. Radiographics 2002;22:87–104.

(5) Prefumo F, Homfray T, Jeffrey I, et al. A new recognized autosomal

recessive syndrome with abnormal vertebral ossification, rib abnor-

malities, and nephrogenic rests. Am J Med Genet 2003;120:386–8.

(6) Esser T, Rogalla P, Sarioglu N, et al. Three dimensional

ultrasonographic demonstration of agenesis of the 12th rib in a

fetus with trisomy 21. Ultrasound Obstet Gynecol 2006;27:714–5.

(7) Harvey CJ, Pilcher JM, Eckersley RJ, Blomley MJK. Advances in

ultrasound. Clin Radiol 2002;57:157–77.

(8) Hull AD, James G, Pretorius DH. Detection of Jarcho-Levin

syndrome at 12 weeks’ gestation by nuchal translucency screening

and three-dimensional ultrasound. Prenat Diagn 2001;21:390–4.

(9) Benoit B. The value of three-dimensional ultrasonography in the

screening of the fetal skeleton. Childs Nerv Syst 2003;19:403–9.

(10) Wong GY, Wong SF, Chan WP, et al. Three-dimensional

ultrasound findings of spondylocostal dysostosis in the second

trimester of pregnancy. Ultrasound Obstet Gynecol 2006;27:580–2.

(11) Ruano R, Benachi A, Aubry MC, et al. Volume contrast

imaging: a new approach to identify fetal thoracic structures. J

Ultrasound Med 2004;23:403–8.

(12) Vinals F, Munoz M, Naveas R, et al. The fetal cerebellar vermis:

anatomy and biometric assessment using volume contrast imaging

in the C-plane (VCI-C). Ultrasound Obstet Gynecol

2005;26:622–7.

(13) Gindes L, Benoit B, Pretorius DH, et al. Abnormal number of

fetal ribs on 3-dimensional ultrasonography: associated anom-

alies and outcomes in 75 fetuses. J Ultrasound Med 2008;27:

1263–71.

(14) Gupta V, Suri RK, Rath G, et al. Synostosis of first and second

thoracic ribs: anatomical and radiological assessment. Int J Anat

Var (IJAV) 2009;2:131–3.

(15) Sahinoglu Z, Uludogan M, Gurbuz A, et al. Prenatal diagnosis

of thanatophoric dysplasia in the second trimester: ultrasonogra-

phy and other diagnostic modalities. Arch Gynecol Obstet

2003;269:57–61.

(16) Parilla BV, Leeth EA, Kambich MP, et al. Antenatal detection of

skeletal dysplasia. J Ultrasound Med 2003;22:255–8.

(17) Yeo L, Guzman ER, Shen-Schwarz S, et al. Value of a complete

survey in detecting fetal abnormalities: correlation with perinatal

autopsy. J Ultrasound Med 2002;21:501–10.

(18) Loder RT, Huffman G, Toney E, et al. Abnormal rib number in

childhood malignancy: implications for the scoliosis surgeon.

Spine 2007;32:904–10.

(19) Hershkovitz R. Prenatal diagnosis of isolated abnormal number

of ribs. Ultrasound Obstet Gynecol 2008;32:506–9.