Jugan MC, August JR. Serum cobalamin concentrations and small intestinal ultrasound changes in 75 cats with clinical signs of gastrointestinal disease: a retrospective study. J Feline Med Surg. 2017 Jan;19(1):48-56.
Cobalamin (Vitamin B12) is an essential nutrient in the feline diet. Aside from the need to supplement cobalamin in several feline diseases, measurement of serum cobalamin levels has become an important tool for the diagnosis of intestinal disease. The absorption of Vitamin B12is complex, involving a series of gastric proteases, intrinsic factor, transcobalamin, and other interactions. While its deficiency is primarily a marker of ileac disease, blood levels also depend on hepatic and pancreatic disease, neoplasia, and other factors. Abdominal ultrasound has also been utilized extensively as a tool to diagnose intestinal disease.
The purpose of this study was to determine if there is a relationship between cobalamin concentration and the presence of ultrasonographic evidence of intestinal disease. The study was designed as a retrospective analysis of records from Texas A&M University teaching hospital from 2000 to 2013. Cats included in the study had clinical signs of GI disease, cobalamin concentration <500ng/L (369 pmol/L), abdominal ultrasound, and a definitive diagnosis of intestinal disease.
Records from 751 cats were reviewed, of which 75 met inclusion criteria. Most cats were domestic shorthair, no difference was seen between breeds. Most cats presented with chronic GI signs, most commonly weight loss and vomiting. Cats were classified as having either low (<300ng/L) or low-normal (>300ng/L, <500ng/L) cobalamin. Ultrasound findings were evaluated, and definitive diagnosis based on cytology or histopathology was determined.
No specific ultrasound finding was associated with hypocobalaminemia. The most common change documented was increased wall or layer thickness. A significant overlap was found in cats with ultrasound evidence of intestinal disease and normal serum cobalamin. This precluded the determination of a cobalamin cut off value for the presence of GI disease.
Overall, 35% of cats presenting with GI signs and low or low-normal serum cobalamin had a normal abdominal ultrasound. No correlation was seen between serum cobalamin and albumin levels. 91% of cats in the study had some histopathologic evidence of gastrointestinal disease.
This study determined that lower cobalamin concentrations were associated with lymphoma and IBD more than with other gastrointestinal disease. No difference was found in cobalamin levels between lymphoma and IBD. The authors further suggest that a laboratory cut-off value of 300ng/L may be too low, and that a value of <500ng/L may be more sensitive to detect GI disease.
Several drawbacks to this study are present. The authors did not rule out concurrent disease (ie hyperthyroidism, pancreatitis, etc) that may have an impact on cobalamin balance. The location of intestinal lesions within the GI tract on ultrasound was not classified. Ultrasounds were evaluated by multiple operators, introducing some degree of variability.
This study served to establish that there is likely no significant difference between cobalamin levels in cats with IBD and lymphoma, however these two disease states are associated with lower cobalamin than other intestinal disease. This study did not find a correlation between low cobalamin and any specific ultrasound finding. Data suggests that a cut off of 500ng/L (369pmol/L) may be a more sensitive cut off for the diagnosis of GI disease than 300ng/L (221pmol/L). (MRK) See also:
Maunder CL, Day MJ, Hibbert A, et al. Serum cobalamin concentrations in cats with gastrointestinal signs: correlation with histopathological findings and duration of clinical signs. J Feline Med Surg 2012; 14: 686–693.