Why , when ? This can be explained in several parts. One could be due to a birth defect. Another is that it can happen after birth for various reasons. If for some reason a surgery is performed , a weak part is formed there. Or if a patient is found to be very obese, or if he is found to be pregnant, or if he is found to have long-term cough or constipation, or to urinate, he must urinate quickly. If he does this in the long run , then his weak points will be able to get rid of both the fat in his esophagus or the side of the omentum . This is what we call hernia. And these are the reasons we call them. Both can come out. This is what we call hernia. And these are the reasons we call them.