Megacolon Figure 1c

Figure 1c: Megacolon in 41-day-old rat
Case history and photos


SRR Borrowed Angel, a high-white blazed blue female. Her mother was a unmarked rat (white feet only) with no history of m/c in the line. Her father was from a dominant blazed line that had megacolon in the history
There were 10 in the litter, born 11/6/2000. Two littermates, a black wedge blazed and a black lightning blazed, died at about two weeks old. Their muscle tone was not good, and though their bellies were large but not really abnormally large, the cause of death on both appeared to be megacolon. Some of the siblings were high whites who were not afflicted with megacolon.

Clinical Signs

As is often normal in a litter with megacolon, what is first noticed, before they reach two weeks, is that the affected pups have poor muscle tone. The first place that it can be noticed is in their back legs/thighs. Bloating isn’t very noticeable until they begin to eat solid foods. This particular little female rarely had any diarrhea except for a couple of occurrences. She mostly had no stools.Pups with megacolon also grow more slowly than their unaffected siblings, probably due to poor absorption of nutrients. Though she was smaller and quite bloated, she was normal and active, eating, drinking, playing on the wheel, playing with her siblings, affectionate with her people, etc. until just hours before she died.


Genetic megacolon.


I could not find anything at the time, though I believe her case was severe enough that she would not have survived to live a normal life even with treatment. When onset is seen at birth, it’s rare that any treatment will help.


SRR Borrowed Angel died at 46 days old, peacefully, and on her own in my hands. She was calm and had slowed down her activity. There was no evidence that it was time.
(Note: comfort of the rat is important. If at any time the rat appears to be distressed euthanasia should be considered.)


megacolon at 41 days

Photo 1: At 41 days old showing distention of the abdomen.
  Comparison photo

Photo 2: Comparison between siblings. One with megacolon and one without.

At 45 days old

Photo 3: Shows increasing distention at 45 days of age.
  At 45 days old

Photo 4: Considerable bloating can be seen.
  Comparison between siblings

Photo 5: Comparison between siblings.

Case history and photos courtesy of E. Brooks at Spoiled Ratten Rattery— Archived page from 2013-07-29 (via the Wayback Machine)


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