There are many DVM's & people that do not belive that "Cow Pile Syndrome" (aka Megacolon) is a "medically recognized condition". If your rabbit has Megacolon you might be in for an uphill battle depending on the VET. Here is an [HRS] House Rabbit Society article that reports on this non MC/CPS idea. Disorders of the Cecum by Marie Mead, has a small section on "COW PILE SYNDROME":
"Cow pile syndrome, named for its most visible characteristic, may result from a combination of factors, including genetic, environmental, and dietary. Though not a medically recognized condition, brief mention is included because of some of the similarities with cecal motility disorders.
Determining whether a rabbit is suffering from a condition that affects the cecum or colon requires the skill of an experienced rabbit veterinarian. The caregiver can assist in the process by providing astute and accurate observations about the problem. Additional factors aid in the diagnostic process, including the history of medications, description of the diet (including dates and details of change), any possible foreign materials ingested and date of occurrence(s), and stress factors. Regardless of the condition, appropriate diet plays a crucial role in the recovery and health of the rabbit.