Yes, it is! However, if this is continuous and uncontrollable, you should perform wudhu after the athan and then pray, regardless of what comes out until the Time of the following prayer.

After surgery am not passing stool through the normal passage, instead its being collected in a bag attached to my belly and has to be emptied out when filled. I dont pass wind as usual but do know that it has gone in the bag as i hear the sound. When this happens, is my wadhu nullified?