Hyperammonaemia due to cobalamin malabsorption in a cat with exocrine pancreatic insufficiency

Effect of oral or subcutaneous administration of cyanocobalamin in hypocobalaminemic cats with chronic gastrointestinal disease or exocrine pancreatic insufficiency

BACKGROUND

No prospective study has evaluated the efficacy of oral supplementation with cobalamin in hypocobalaminemic cats.

OBJECTIVES

To investigate the efficacy of oral or SC supplementation with cyanocobalamin in normalizing serum cobalamin and methylmalonic acid (MMA) concentrations in hypocobalaminemic cats with chronic gastrointestinal disease (CGID) or exocrine pancreatic insufficiency (EPI).

ANIMALS

Forty-eight client-owned hypocobalaminemic (<290 ng/L) cats with normal or abnormally high serum MMA concentrations.

METHODS

This study was conducted based on the prospective randomized clinical trial method. Cats with CGID or EPI were randomly assigned to 2 groups that received either oral or SC supplementation with cobalamin (250 μg/cat) for 12 and 10 weeks, respectively, in addition to other medical and dietary interventions. Each cat was evaluated 3 times (baseline, 6-week postsupplementation, and 1-week postcompletion) by measuring serum cobalamin and MMA concentrations.

RESULTS

In cats with CGID or EPI, cobalamin concentrations were normalized in all cats that received either oral or SC supplementation (mean 100% [95% CI: 80.6%-100%] in both groups in cats with CGID and 100% [67.6%-100%] in both groups in cats with EPI). Among 37 cats with elevated MMA concentrations at baseline (21 cats with CGID and 16 cats with EPI), MMA concentrations were normalized in most cats with CGID (70% in oral and 82% in SC group) or EPI (88% in both groups).

CONCLUSIONS AND CLINICAL IMPORTANCE

In hypocobalaminemic cats with CGID or EPI, in conjunction with other medical and dietary interventions, both oral and SC supplementation are effective at normalizing serum cobalamin and MMA concentrations.

Vitamin B12 in Cats: Nutrition, Metabolism, and Disease

Cobalamin is a water-soluble molecule that has an important role in cellular metabolism, especially in DNA synthesis, methylation, and mitochondrial metabolism. Cobalamin is bound by intrinsic factor (IF) and absorbed in the ileal tract. The IF in cats is synthesized exclusively by pancreatic tissue. About 75% of the total plasma cobalamin in cats is associated with transcobalamin II, while in this species, transcobalamin I is not present. In cats, the half-life of cobalamin is 11-14 days. Diagnostic biomarkers for B12 status in cats include decreased levels of circulating total cobalamin and increased levels of methylmalonic acid. The reference interval for serum cobalamin concentrations in cats is 290-1500 ng/L, and for the serum methylmalonic acid concentration, it is 139-897 nmol/L. Therapy for hypocobalaminemia mainly depends on the underlying disease. In some cases, subcutaneous or intramuscular injection of 250 μg/cat is empirically administered. In recent years, it has been demonstrated that oral cobalamin supplementation can also be used successfully in dogs and cats as a less invasive alternative to parental administration. This review describes the current knowledge regarding B12 requirements and highlights improvements in diagnostic methods as well as the role of hypocobalaminemia in its associated diseases.

Serum cobalamin concentrations in dogs infected with canine parvoviral enteritis

OBJECTIVE

To compare the serum cobalamin concentrations in canine parvovirus (CPV)-infected dogs with those of healthy control dogs.

Animals

45 dogs with CPV enteritis and 17 healthy age-matched control dogs.

Procedures

Infection was confirmed by visualization of CPV-2 through fecal electron microscopy. All dogs received supportive care. Serum samples taken at admission were used to determine cobalamin, C-reactive protein, and albumin concentrations.

Results

Serum cobalamin concentrations were significantly lower in the CPV-infected group (median [interquartile range], 173 pmol/L [< 111 to 722 pmol/L]) than in healthy control dogs (379 pmol/L [193 to > 738 pmol/L). There was no association between cobalamin concentration and C-reactive protein or albumin concentration.

Clinical Relevance

While hypocobalaminemia was common in CPV-infected dogs, the clinical relevance of this finding remains to be determined. Studies assessing markers of cellular cobalamin deficiency in dogs with CPV infection appear warranted.

EXOCRINE PANCREATIC INSUFFICIENCY-LIKE SYNDROME IN FOUR CAPTIVE TIGERS (PANTHERA TIGRIS)

Exocrine pancreatic insufficiency (EPI) is a condition characterized by a decreased synthesis and secretion of pancreatic enzymes, which results in weight loss, poor hair coat, and diarrhea. The diagnostic test of choice for EPI in domestic cats is feline serum trypsin-like immunoreactivity (fTLI). This paper details four tigers (Panthera tigris) with clinical signs compatible with EPI. On the basis of domestic cat reference ranges, fTLI assays for all four clinically affected tigers were diagnostic for EPI (median 1.0 µg/L; range 0.5-1.2 µg/L). All four tigers had a rapid clinical response to pancreatic enzyme supplementation. Serum from 10 clinically healthy tigers was submitted for the fTLI assay, for comparative purposes. The healthy tigers' fTLI assays were also within range for a diagnosis of EPI in domestic cats (median 3.1 µg/L; range 1.9-4.5 µg/L); however, clinically affected tigers had significantly lower serum fTLI concentrations than healthy tigers (P = 0.0058). Serum cobalamin was below the detection limit in both the affected and healthy tigers (<150 ng/L). Measuring fTLI appears to be a useful tool in the diagnosis of EPI-like syndrome in tigers. As in other species, EPI-like syndrome in tigers may also be associated with cobalamin deficiency.

Signalment and Clinical Data of Cats with Exocrine Pancreatic Insufficiency Diagnosed Using Feline Trypsin-like Immunoreactivity in Routine Diagnostics

Serum feline trypsin-like immunoreactivity (fTLI) is commonly used to diagnose feline exocrine pancreatic insufficiency (EPI). This study aimed to describe signalment and clinical data of cats with EPI. Determination of TLI was performed using an in-house ELISA; the reference interval was defined using a Reference Limit Estimator. Groups were formed from 4813 cats (2019-2020), based on their fTLI concentration: 1 (<8 µg/L; decreased; n = 275), 2 (8-88 µg/L; reference interval; n = 4256), and 3 (>88 µg/L; increased; n = 282). Males and Domestic Shorthairs were most common in all groups. Group 3 had the highest (13 years), and group 1 had the lowest (9 years), median age. Clinical information was available for 200 cats (decreased fTLI: n = 87, lower reference interval (8-12 µg/L): n = 113). Treatment response was observed in 83% (decreased fTLI) and 66% (lower reference interval). EPI cats displayed weight loss (69%), diarrhoea (68%), vomiting (41%), anorexia (39%), poor hair coat (35%), lethargy (33%), and/or polyphagia (21%). The lower the serum fTLI concentration, the more often good treatment response was reported (p = 0.022) but there were no statistically significant clinical signs. In conclusion, fTLI is a helpful parameter to diagnose EPI but predicting treatment response based on signalment or clinical signs is not possible.

Hyperammonemia in azotemic cats

OBJECTIVES

Hyperammonemia occurs in cats with hepatobiliary and nutritional (cobalamin and arginine deficiency) disorders, and has also been documented in four cats with renal azotemia. We hypothesized that in cats with renal azotemia, fasting hyperammonemia would correlate with indices of worsening kidney function, and would be independent of cobalamin, potassium, systemic inflammation or urinary tract infection (UTI) with urease-producing bacteria.

METHODS

A fasted blood sample was prospectively collected for ammonia and cobalamin analysis from 18 client-owned cats with renal azotemia (creatinine [Cr] ⩾1.6 mg/dl, urine specific gravity <1.030 or documentation of historical chronic kidney disease [CKD]). Correlations between blood ammonia and selected biochemical parameters were analyzed using Pearson's correlation coefficient.

RESULTS

Seven castrated males and 11 spayed females with a median age of 12 years (range 4-19 years) were enrolled. Ten of 18 (56%) cats presented for acute kidney injury (AKI) or acute on chronic kidney disease (AoCKD), and 8/18 (44%) presented for progressive CKD. The median Cr was 5.9 mg/dl (range 1.9-24.7 mg/dl). Hyperammonemia was documented in 4/18 (22%) cats, with a median of 95 µmol/dl (range 85-98 µmol/dl), and all four of these cats were classified as AKI/AoCKD. Blood ammonia concentrations had a significant moderate positive correlation between blood urea nitrogen (BUN) (r = 0.645, P = 0.003), Cr (r = 0.578, P = 0.012) and serum phosphorus (r = 0.714, P = 0.0009) but not with cobalamin, potassium or white blood cell count. No cats had UTIs with urease-producing bacteria.

CONCLUSIONS AND RELEVANCE

A correlation exists between blood ammonia and BUN, Cr and phosphorus in cats with renal azotemia. Future studies are warranted in a larger population of cats to determine the true prevalence, etiology and potential therapeutic effect of medical management of hyperammonemia on long-term prognosis in cats with kidney disease.

Transient hyperammonaemia following epileptic seizures in cats

OBJECTIVES

The aim of this study was to determine whether transient postictal hyperammonaemia exists in cats.

METHODS

The medical records of all feline patients that presented at a Swedish veterinary hospital between 2008 and 2018 were retrospectively reviewed to find those that had a recent or ongoing epileptic seizure. To qualify for inclusion, the medical record had to include information on at least one ammonia value taken in close proximity to, or during, an active seizure, the cat must have exceeded the normal upper limit of blood ammonia concentration on initial testing (reference interval 0-95 μmol/l), and there needed to be a follow-up ammonia value available within a maximum of 3 days.

RESULTS

Five cats were included in the study, and they had blood ammonia concentrations on initial testing ranging from 146 to 195 µmol/l. They were all retested within a period of 2 h to 3 days of the original reading. All five cats had a spontaneous decrease in ammonia levels without any specific treatment for hyperammonaemia.

CONCLUSIONS AND RELEVANCE

Pursuant to the findings of this retrospective study, transient hyperammonaemia may be noted after epileptic seizure in cats. Consequently, a differential diagnostic list in feline patients with hyperammonaemia could, depending on the context, include non-hepatic-related pathologies, such as epileptic seizures.

Acquired urea cycle amino acid deficiency and hyperammonaemic encephalopathy in a cat with inflammatory bowel disease and chronic kidney disease

Case summary

A 5-year-old male neutered Persian cat was referred for investigation of a 4 week history of weight loss, inappetence and intermittent vomiting. Chronic kidney disease (CKD) and inflammatory bowel disease were diagnosed, and despite immunosuppressive therapy and assisted enteral nutrition, the cat experienced persistent anorexia, vomiting and severe weight loss. After 2 additional weeks of treatment, the cat developed acute-onset neurological signs associated with severe hyperammonaemia and was euthanased. Plasma amino acid assessment revealed deficiency of several amino acids involved in the urea cycle, including arginine.

Relevance and novel information

To our knowledge, this is the first reported case of an acquired urea cycle amino acid deficiency without nutritional deprivation in a cat. Several contributing factors were suspected, including intestinal malabsorption and CKD. This case demonstrates the importance of urea cycle amino acids in feline metabolism and possible necessity for parenteral supplementation, particularly in the context of persistent weight loss despite adequate enteral nutrition.

Effects of 6 Weeks of Parenteral Cobalamin Supplementation on Clinical and Biochemical Variables in Cats with Gastrointestinal Disease

Background

Effects and duration of commonly used protocols for cobalamin (Cbl) supplementation on cellular Cbl deficiency have not been determined in hypocobalaminemic cats.

Hypothesis/Objectives

To evaluate effect of Cbl supplementation on clinical signs, serum and urine methylmalonic acid (MMA) concentrations over 16 weeks.

Animals

Twenty client‐owned hypocobalaminemic cats with enteropathy.

Methods

Prospective study. Serum Cbl and serum and urine MMA concentrations were determined prospectively in cats at enrollment (t0), immediately before (t6), and 4 (t10) and 10 weeks (t16) after 6th Cbl injection (250 μg, IM q 7 days). Clinical signs severity (activity, appetite, vomiting, diarrhea, body weight) graded at each time point and expressed as clinical disease activity score.

Results

Clinical disease activity score decreased during supplementation and increased after treatment discontinuation. Median serum Cbl concentration increased significantly from t0 (111 pmol/L, range 111–212) to t6 (2,332.5 pmol/L, range 123–22,730) (P < 0.01). Values at t10 were 610.5 pmol/L (range, 111–2,527) and 180.5 pmol/L (range, 111–2,262) at t16 (P < 0.01). Median baseline serum MMA concentration (372 μmol/L, range 0.39–147,000) decreased significantly to 1.62 μmol/L (range, 0.18–806) at t6 (P < 0.01) and gradually increased to 5.34 μmol/L (range, 0.13–1,730) at t10 and 189 μmol/L (range, 0.4–983) at t16. Similar, nonsignificant, pattern observed for urine MMA concentration. Serum and urine MMA concentrations had not normalized in 12 and 6 cats, respectively, at t6.

Conclusion and Clinical Importance

The Cbl supplementation protocol used here did not lead to complete normalization of cellular Cbl deficiency in all examined cats, and biochemical improvements were transient.

Feline Exocrine Pancreatic Insufficiency: A Retrospective Study of 150 Cases

Background

Little information is available about the clinical presentation and response to treatment of cats with exocrine pancreatic insufficiency (EPI).

Objectives

To describe the signalment, clinical signs, concurrent diseases, and response to treatment of cats with EPI.

Animals

One hundred and fifty cats with EPI.

Methods

Retrospective case series.

Results

Questionnaires were sent to 261 veterinarians, and 150 (57%) were returned with data suitable for statistical analysis. The median age of the cats with EPI was 7.7 years. The median body condition score was 3 of 9. Ninety‐two of 119 cats (77%) had hypocobalaminemia, and 56 of 119 cats (47%) had increased and 6 of 119 cats (5%) had decreased serum folate concentrations. Clinical signs included weight loss (91%), unformed feces (62%), poor hair coat (50%), anorexia (45%), increased appetite (42%), lethargy (40%), watery diarrhea (28%), and vomiting (19%). Eighty‐seven cats (58%) had concurrent diseases. Treatment response was reported to be good in 60%, partial in 27%, and poor in 13% of 121 cats. Trypsin‐like immunoreactivity <4 μg/L was associated with a positive response to treatment (OR, 3.2; 95% CI, 1.5–7.0; P = .004). Also, cobalamin supplementation improved the response to treatment (OR, 3.0; 95% CI, 1.4–6.6; P = .006).

Conclusions and Clinical Importance

Exocrine pancreatic insufficiency in cats often has a different clinical presentation than in dogs. The age range for EPI in cats is wide, and many cats can be ≤5 years of age. Most cats respond well to appropriate treatment for EPI, and cobalamin supplementation appears to be necessary for a good response.

Hyperammonaemia in four cats with renal azotaemia

Hyperammonaemia is well reported in animals with advanced hepatic disease and portosystemic shunts, but is unreported in cats with renal disease. This case series describes four cats with severe renal azotaemia in which elevated ammonia levels were detected during the course of treatment. In two cases hyperammonaemia was detected at a time when neurological signs consistent with encephalopathy had developed. This raises the possibility that hyperammonaemia may play a role in the development of encephalopathy in cats with renal azotaemia.

Cobalamin in companion animals: diagnostic marker, deficiency states and therapeutic implications

Measurement of the water-soluble vitamin cobalamin has long been of interest as a marker of gastrointestinal disease in companion animals due to the highly localized presence of cobalamin receptors in the ileum. An increasing body of evidence suggests that cobalamin deficiency is an important co-morbidity in many companion animal patients with gastrointestinal and pancreatic disease. Congenital disorders of cobalamin absorption and cellular metabolism are also increasingly recognized in companion animal breeds. The early recognition of these disorders and timely treatment with parenteral cobalamin can be life-saving. In this article, the normal mechanisms of cobalamin absorption, the use of cobalamin as a marker of intestinal disease and data on the prevalence of hypocobalaminemia in a variety of diseases are described. The prognostic impact of and rational therapy for hypocobalaminemia in domestic animals are discussed.