Gall Bladder Mucocele (GBM) results when the inside lining of the gallbladder produces a solidified mucus. The mucus remains attached to the lining of the gallbladder and over time fills the entire lumen of the gallbladder leading to obstruction to the flow of bile or rupture of the gallbladder. GBM has received a lot of attention recently. In the past it may not have been diagnosed correctly, however the availability of abdominal ultrasound has made it easy to diagnose. In the UK (where there are at least 5 times the registration of Border Terriers than we see in the US) there has been a concern about the incidence of GBM. Surgery to remove the gall bladder is often the outcome. Late diagnosis does not help as the dogs are often a poor surgical risk at that time.