Does it ever happen that a hiatal hernia make passing gas difficult?

Not unless: It is an incarcerated paraesophageal type of hiatal hernia. The usual sliding type involves on the esophagus and proximal stomach, so it should not affect your colon function. A paraesophageal hiatal hernia has a propensity for serious complications, sometimes even fatal, so have your GI specialist or surgeon take a look.

Hiatal hernia : No, not really. A hiatal hernia can give you heartburn or reflux, or make it hard to get food down, but really wouldn't affect your ability to pass gas.