Elevated Dome of Diaphragm -CXR Teaching Points

A young male for  medical check up shows accentuated difference in heights of the  domes of approximately 35mm with rest of the study normal including supra and infra diaphragmatic regions    which may suggest  unusual causes like  eventeration.

Teaching points by Dr MGK Murthy

1.    Usual accepted range in vertical deep inspiratory  position of CXR  is 5 to 25mm between cupolae   (Right higher than left in about 95% of normal individuals)(X ray beam centered at D4) (unless lot of swallowed air in stomach  or colonic distension  changes this equation)

2.    Level is counted in terms of ribs in relation to the highest point in mid lung field  as  the dome is clearly  discernible at this levels  and anterior ribs are closer to the film than posterior ones .

3.    Least chance of shadow of anterior ribs or diaphragm being projected downwards if centering beam is unusually high or  leaning  forward of the  patient (common error)

4.    Disadvantage is anterior ribs move cranial  more than posterior ones in inspiration, down ward  slope of anterior ribs is variable  & length differs in individuals

5.    In  about 95% individuals , right dome  between 5 to halfway between 6&7 (anterior). Stocky or fat  could be as high as 4th  and asthenic  lean persons  as low as 7th

6.    15% of normal  children  between 5-15 years  will have right  dome below halfway between 6&7 ribs  because  ribs are shorter and more horizontal than adults.

7.    Domes levels with respect to dorsal  vertebrae include  Right (D11/D12)and left (D12) on inspiration ,  D8 (right) D9 (left) on expiration

8.    Though anatomically  Supine position makes dome  3 cm higher than vertical  position & if he rolls on one side /prone position, dome  higher that side (because of pressure of viscera), In practice these are hardly  conspicuous on radiographs and are usually not significant

9.    Patholgical causes  of course include   paresis, eventeration and intra abdominal  volume increase (gas, fluid, SOL etc ),  reduced lung compliance (SLE) and lung collapse  etc