I’m so sorry to hear that your family and rabbit are going through this. It would be helpful to know what you are presenting your rabbit with each day in terms of diet, just to rule-out if something in the diet may be causing ongoing GI distress.

If you hadn’t come across it already, the Wabbitwiki page on Megacolon is a helpful resource: https://wabbitwiki.com/wiki/Megacolon
There is no formal “test” to confirm megacolon, but diagnosis comes from a combination of looking at the rabbit’s coloring (En/En) and process of elimination with unsuccessful treatments from other GI-related issues.

I’m so sorry you are going through this, but please try not to panic! It’s true that megacolon rabbits often have shorter lifespans, but with a care plan they often do much better. Usually megacolon buns will need a motility medication daily (cisapride is commonly used), as well as a high calorie diet, such as supplemental feeding with critical care or another recovery food (like Emeraid or Sherwood’s formula). Keeping the gut well hydrated also helps, so some people will give lactulose (under the vet’s instruction) as part of the treatment plan. Vets are becoming more knowledgeable about megacolon and how to keep buns comfortable.

Once this initial bout of stasis is dealt with I would talk to your vet about having an arsenal of at-home treatment options that are part of his daily routine as well as things you can do first when you see an episode coming on. When a bun has chronic issues most vets will work out a plan like this with you.

Have his poops always matched those of a megacolon bun, or just when he’s having an episode? Usually buns with megacolon NEVER have normal poops, and symptoms really start to appear around age 3. There are other things that can cause chronic stasis, so it would be important to rule out those other causes before jumping to megacolon. For example, a tiny molar spur can also cause enough pain and reduced hay eating to cause a bun to have stasis episodes and weight loss.