Case report

The present case show an incidental findings found on routine pregnancy scan screening at 24 weeks of gestational age. The patient was referred to our hospital at 26 weeks of pregnancy.

Images 1-4: Thoracic and abdominal situs concordant, with both heart and stomach on the left side.

US assessment of cardiac anatomy was difficult due to poor acoustic window.Cardiac axis looks normal, but heart position is shifted to the left: this situation suggests absence of a left-sided structure or a compressive right-sided structure.Color Doppler shows on the right side a vessel which could be clearly followed from the umbilical cord, compatible with a portal vein sinus. Suspicion of right diaphragmatic hernia with liver ascension within a normal sized-thorax.

Images 5-10: MR allows better visualization of lung and liver: lung's signal is hyper T2W while liver's signal is hypo T2W.

MR confirms the right-sided diaphragmatic defect with an intrathoracic liver. Portal vein sinus is seen in the coronal and axial planes as a tubular structure without signal due to flow-voids.
Right lung is not seen.
Left lung is atrophic. Pulmonary volumetry was 7 mL, while expected volumetry for gestational age was 40 mL.

T1 sequence allows meconium identification: hence the colon is found here in the right abdominal upper quadrant. Note that liver is slightly hyper T1W compared to lung as well.

The final diagnosis was congenital diaphragmatic hernia, right-sided, non syndromic.

Case Discussion

Most diaphragmatic hernias (90%) are left-sided, thus right-sided account for only 10% of the cases. Diagnosis of left-sided is usually easier thanks to the stomach acting as an acoustic window. US contrast resolution often results in difficulties in distinguishing lung from liver in standard screening, hence small right-sided diaphragmatic hernias may be missed.

MR imaging depicts a clearer image of the anatomy, thanks to its multiplanar analysis and improved contrast.  In fetal US the lung to head ratio is employed, whilst with MR provides additional prognostic factors with estimated fetal lung volume assessment, which is compared to normal fetal lung volume expected for gestational age.

Right-sided hernia may be part of a wider pathology: Fryns syndrome, which includes additional facial and limb anomalies;  not found in our case.

References

1. Mehollin-Ray AR, Cassady CI, Cass DL, Olutoye OO. Fetal MR imaging of congenital diaphragmatic hernia. (2012) Radiographics : a review publication of the Radiological Society of North America, Inc. 32 (4): 1067-84.

2. Rypens F, Metens T, Rocourt N, Sonigo P, Brunelle F, Quere MP, Guibaud L, Maugey-Laulom B, Durand C, Avni FE, Eurin D. Fetal lung volume: estimation at MR imaging-initial results. (2001) Radiology. 219 (1): 236-41. 

3. G. Gorincour, J. Bouvenot, M.G. Mourot, P. Sonigo, K. Chaumoitre, C. Garel, L. Guibaud, F. Rypens, F. Avni, M. Cassart, B. Maugeyâ€Laulom, B. Bourlièreâ€Najean, F. Brunelle, C. Durand, D. Eurin. Prenatal prognosis of congenital diaphragmatic hernia using magnetic resonance imaging measurement of fetal lung volume. (2005) Ultrasound in Obstetrics and Gynecology. 26 (7): 738.