A recent study examined 2,400 canine cases of congenital portosystemic shunts (CPSS) recorded in the Veterinary Medical Database from the period 1980-2002. CPSS were reported in 0.18% of all dogs and 0.05% of mixed-breed dogs, with Yorkshire Terriers representing 20.1% of those reported. In 1980, the proportion of reported dogs with CPSS was 0.05%, whereas it had increased 10-fold to 0.5% by 2001. During this period, diagnosis of CPSS in Yorkshire Terriers increased from 8.6% of Database accessions in 1980 to 31.6% in 2000. As compared to mixed breed controls, 33 breeds were significantly more likely to have CPSS. The greatest proportion of diagnoses were reported in Havanese (6/187) [3.2%], Yorkshire Terrier (483/16,538) [2.9%], Maltese (100/6,231)[1.6%], Dandie Dinmont Terrier (4/251) [1.6%], Pug (75/5,681) [1.3%], and Miniature Schnauzer (244/24,411) [1%]. Veterinarians and owners/breeders of breeds at increased risk for CPSS should be alerted to the clinical signs and methods of diagnosis of the disorder.
. Reference: Tobias, Rohrbach. JAVMA 223: 1636-1639, 2003.

Congenital portosystemic shunts (PSS) are commonly seen in Yorkshire terriers. The hereditary basis for PSS in this breed was explored through case records, pedigree analysis, and a breeding trial. The odds ratio for PSS in Yorkshire Terriers was 35.9 times greater than that for all other breeds combined. The coefficient of inbreeding was about twice as high for Yorkshire terriers with PSS as compared to normal members of the breed. No common ancestors were found that were significant to the PSS group. Two affected Yorkshire terriers were bred and produced two normal puppies. Thus, while PSS appears to be hereditary in this breed, the mechanism of inheritance has yet to be defined.
Reference: Tobias, JAAHA 39:385-389, 2003.

Critically ill humans and dogs commonly have abnormal serum magnesium concentration (Mg). A study of 57 cats in intensive care found that abnormal Mg was associated with increased morbidity and mortality. Hypermagnesemia was seen in cats with azotemia or thoracic neoplasia and pleural effusion. While hypomagnesemia was more common, it was not associated with any specific category of disease. In some cases, low Mg was seen during hospitalization, perhaps from reduced dietary intake, administration of fluids low in magnesium, or effects of medications. Hypomagnesemia could contribute to patient mortality by affecting cardiac or other functions.
Reference: Whitney. Adv Sm An Med Surg 16(9): 1, 2003.