Can hiatal hernia be seen on ct scan without contrast?

Probably, but....: The CT image without contrast can show a suspension of some altered image of the included tissues/organs like suspecting hiatal hernia, and that with contrast can enhance the anatomical delineation of tissues/organs so to almost 100% assurance of hiatal hernia. Remember: Almost all medical care is based on INDIRECT evidence from accumulated experience; like wise, it is true for hiatal hernia. Best