Dr. Pepe’s Diploma Casebook 167 – Big little findings – SOLVED

Dear friends,
Presenting today a new case of “Big little findings”. This case is not recommended for the faint-hearted 😱
Chest images belong to a 65-year-old woman with moderate cough. Since I am your friend, I am including an axial CT.

What do you think?

Click here to see the answer

Findings: PA radiograph shows a curvilinear opacity in the right middle/lower lung (A, arrows). The right lung is slightly smaller than the left and the hilum looks abnormal (A, circle). Aside from slight elevation of the right hemidiaphragm, the lateral view (B) is unremarkable.

Coronal CT shows that the curvilinear line represents a scimitar vein draining below the diaphragm (C, arrow). The right pulmonary artery describes an unusual path (D, circle) and there is abnormal branching of the right main bronchus (D, circle).

An unexpected finding is an oblique band in the lower right lung (E and F, arrows). The bronchi and RLL vessels pass through an opening in the center (E and F, circles).

Final diagnosis: hypogenetic right lung with duplicated diaphragm

The reason I’m presenting this case is to discuss duplication of the diaphragm, an uncommon congenital malformation associated with hypogenetic lung.

As you all know, hypogenetic lung is a congenital malformation characterized by absence of one or two lobes of the right lung, with abnormal lower lung venous drainage (scimitar vein) in 80% of cases. It is asymptomatic and almost always occurs on the right side. Because it is symptomless, it is usually found incidentally in adults .

Typical signs in the PA chest radiograph (Fig. 1) reflect the small size of the lung:

1. Small right hemithorax with secondary dextrocardia
2. Small right hilum
3. Anomalous vein in RLL (scimitar sign), not always present

Fig. 1. PA radiograph (A) shows typical appearance of hypogenetic lung: small right hemithorax, secondary dextrocardia, and a scimitar vein (A, arrows) coursing downwards to join the IVC. Enhanced coronal CT in a different patient shows the scimitar vein to better advantage (B, arrow). Axial CT confirms the small right hemithorax and abnormal branching of the right main bronchus (insert, circle).

Occasionally, hypogenetic lung occurs with minimal hypoplasia, a normal-sized right lung, and absent dextrocardia. In these patients (such as the initial one), the scimitar vein and abnormal right hilum are the clues to the diagnosis.

In my experience, these cases are the ones most commonly associated with duplicated diaphragm, an infrequent malformation resulting from an alteration of caudal migration of the embryonic diaphragm.

Anatomically it appears as a band running obliquely from the chest wall to the right hemidiaphragm (Fig. 3, drawing).

If we’re lucky, we might see it as an oblique line in PA and lateral radiographs (Fig. 4), but it is usually not visible or overlooked (Fig. 5). An additional sign is blurring of the central part of the right hemidiaphragm, where the duplication ends (Figs. 4 and 5).

Fig. 3. Coronal and axial drawings demonstrating the appearance of the duplicated diaphragm (A and B, blue lines) and vessels crossing through the central orifice (A and B, in red).
Fig. 4. Duplicated diaphragm visible in the PA and lateral radiographs as an oblique band (A and B, white arrows). Note that the contour of the right hemidiaphragm becomes blurred where the duplicate joins it (A and B, red arrows). Axial CT confirms the duplicated diaphragm (C, white arrows) and crossing vessels (C, red arrow). A scimitar vein was not present in this patient.
Fig. 5. Blurring of the central right hemidiaphragm (A, red arrow) and an oblique line in the lateral view (B, red arrow) were present in the initial case, but they were overlooked. Signs in the chest radiograph can be too subtle. My advice is to rely on the CT findings.

My hard-learned experience tells me it is very difficult to suspect duplicated diaphragm on plain films. It is usually discovered in a CT performed to confirm a hypogenetic right lung or for other reasons.
The good news is that the CT findings are pathognomonic and consist of:

1. An oblique band with a central opening
2. RLL bronchi and vessels passing through the opening and fanning out thereafter

You may wonder why I present such a rare condition, but the answer is simple:

a) It is easily recognized because of the distinctive findings. Once recognized, advise against surgery or other invasive procedures.

b) I don’t believe it’s that rare. In my career I have seen a dozen cases, the last three in this century and at the same institution. The last, seen in 2015, is the one that headed this Diploma. Two more were seen in 2004 and 2008 (Cases 1 and 2, below).

I am due to see a new case soon. Perhaps in a COVID patient, allowing me to write a useless paper about the relationship between COVID and duplicated diaphragm 🙂

CASE 1. 56-year-old woman investigated for lymphoproliferative syndrome. Axial and coronal CT show an unsuspected duplicated diaphragm (A and B, white arrows) and the crossing vessels (A and B, red arrows).
CASE 2. CT requested for chronic bronchitis in a 44-year-old woman. Axial CTs document the complete duplicated diaphragm (red arrows), the vessels insinuating through it (B, circle) and lower down, the orifice with the vessels passing through (C, green arrow). White arrows point to the downward course of the scimitar vein before draining in the IVC.


Follow Dr. Pepe’s advice:
1. Duplicated diaphragm is an infrequent malformation associated with hypogenetic right lung

2. Difficult to detect in the chest radiograph

3. Easy to diagnose in CT images by the following signs:

a) Oblique band with a central hiatus in the right lower lung

b) Central hiatus that constricts RLL bronchi and vessels

10 thoughts on “Dr. Pepe’s Diploma Casebook 167 – Big little findings – SOLVED

  1. Scoliotic thorax cage.

    CXR(PA, lateral): Right lower lobe is decreased in volume.
    CT:
    Lung (showned) parenchyma is intact.
    There is peribronchovascular thickening at the level of RLL S8-10. As well as thickening of big fissure.

    Taking into account both x-ray and ct – suggesting S8 (right) atelectasis.

    Suggesting amyloidosis (tracheobronchial type?) DDx lung ca (superficial endobronchial).

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  2. I can see that you are puzzled by this case (only two answers so far). I would offer some tips:
    1. Which lung is abnormal, right or left?
    2. What do you think of the curve thick line in the middle right lung? What does it look like?
    3. The appearance of the CT image is pathognomonic (if you know the entity).
    4. Remember that this case is not for the faint-hearted!

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    1. 1. Right lung is abnormal
      2. Looking repeatedly on CXR suggesting vascular (arterial) pathology- right hilum has not its common structure. Thus, this curve thick line could be vessel
      3. But I suppose I do not know this entity (maybe, anatomy variation or other benign malignancy)

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  3. CXR PA , later showed Rticulonoduar shadow bilateral middle and Lowe zones,more right in lung
    With obvious loss af right lung volum and thickened curved nodular shadow in middle right lung ? Bronchovascular intesticium thickening,?lymphatic in origin
    CT showed thickened blood vessels with mild dilated airways (peribronchovascular interstium thichening),with small nodular lesions petivasular and adhere to pleura near cardiac
    DD
    Sarcidosis
    Silicosis
    Connective tissue disorders (sjogren)
    Lymph proliferative disorder

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  4. Hello! On Pa image, right hilus with unclear vascular structure. Under it, suspicious nodular opacity. On lateral image, dilated inferior pulmonary veins and arteries. Ct showed a non calcified lobular nodule suspicios with connection to blood vesel (until we have an image of Cy ),and about it, dilated blood veesels. My first opinion is for pulmonary AVM.

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