Vitamin B12 Status Predicts Survival in Cats with GI Disease—See the New Data

Prevalence of Hypocobalaminaemia and Hypercobalaminaemia in a Referral Population of Cats in the UK and Its Relevance to Clinical Presentation, Diagnosis and Prognosis

Simona Borgonovi, Will Bayton

Background
Cobalamin (vitamin B12) is essential for cellular metabolism and is often used in feline medicine as a marker of gastrointestinal (GI) health. While hypocobalaminaemia (low B12) has recognized associations with chronic enteropathy (CE), exocrine pancreatic insufficiency, and lymphoma, the clinical significance of hypercobalaminaemia (high B12) remains unclear. This study sought to evaluate the prevalence, clinical correlates, and prognostic implications of both hypo- and hypercobalaminaemia in a UK referral population of cats.

Methods
This retrospective study included 216 cats that underwent serum cobalamin testing, abdominal imaging, and serum biochemistry between December 2016 and December 2023 at a UK referral center. Cats were excluded if they had received cobalamin supplementation within 12 weeks or lacked diagnostic completeness. Cats were classified into three groups: hypocobalaminaemia (<400 pg/ml), normocobalaminaemia (400–1000 pg/ml), and hypercobalaminaemia (>1000 pg/ml). Clinical signs, diagnoses, imaging, pathology, and outcomes were analyzed, and survival data were evaluated using Kaplan–Meier curves and logistic regression.

Results
Hypocobalaminaemia was found in 35% (76/216) and hypercobalaminaemia in 31% (67/216) of cats. CE was the most common diagnosis in both groups (51% of hypo- and 58% of hypercobalaminaemic cats). Chronic vomiting, hyporexia, and weight loss were common presenting signs; however, chronic diarrhoea was more prevalent in hypercobalaminaemic cats. Imaging showed that lymphadenomegaly and intestinal wall thickening were more frequent in hypocobalaminaemic cats. Histopathology revealed a strong association between low cobalamin and low-grade intestinal T-cell lymphoma (LGITL). Median survival was significantly lower in the hypocobalaminaemic group (274 days) compared to hypercobalaminaemic (711 days) and normocobalaminaemic cats (389 days). Severe hypocobalaminaemia (<200 pg/ml) conferred a five-fold higher mortality risk.

Limitations
The study's retrospective nature introduces potential biases, including incomplete records and inconsistent diagnostic workups. Histopathologic confirmation of CE was not performed in most cases, limiting diagnostic specificity. The lack of methylmalonic acid testing and a smaller-than-required hypercobalaminaemic cohort may have affected power and interpretation. Additionally, cobalamin supplementation regimens were not standardized.

Conclusions
While serum cobalamin status had limited diagnostic utility for differentiating underlying diseases, it held strong prognostic value. Hypocobalaminaemia—especially when severe—was associated with significantly reduced survival, supporting early testing and supplementation. In contrast, hypercobalaminaemia was common and associated with better outcomes, though its pathophysiology remains unclear. These findings underscore the importance of routine cobalamin assessment in cats with GI disease and suggest further prospective studies are warranted to refine its diagnostic and prognostic roles.

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