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You may be looking at the start of a blockage of the intestines from the fabric. Should the dog start vomiting, having diarrhea, loose hid appetite and become lethargic then you should have him seen as this will require surgery.
As for the leakage of the anus this could be from a blockage or there could be a problem with the anal sacs which are located on either side of the anus. The sacs may be releasing fluid which they normally do with a bowel movement. Sometimes they become full and the dog will scoot to try and break them. You can easily see this if you lift the tail.
Here is more on the anal sacs.