Establishment of an RI for the urine ammonia-to-creatinine ratio in dogs

Correlation between urine anion gap and urine ammonia-creatinine ratio in healthy cats and cats with kidney disease

BACKGROUND

Ammonium excretion decreases as kidney function decreases in several species, including cats, and may have predictive or prognostic value in patients with chronic kidney disease (CKD). Urine ammonia measurement is not readily available in clinical practice, and urine anion gap (UAG) has been proposed as a surrogate test.

OBJECTIVES

Evaluate the correlation between urine ammonia-to-creatinine ratio (UACR) and UAG in healthy cats and those with CKD and determine if a significant difference exists between UAG of healthy cats and cats with CKD.

ANIMALS

Urine samples collected from healthy client-owned cats (n = 59) and those with stable CKD (n = 17).

METHODS

Urine electrolyte concentrations were measured using a commercial chemistry analyzer and UAG was calculated as ([sodium] + [potassium]) - [chloride]. Urine ammonia and creatinine concentrations had been measured previously using commercially available enzymatic assays and used to calculate UACR. Spearman's rank correlation coefficient between UAG and UACR was calculated for both groups. The UAG values of healthy cats and cats with CKD were assessed using the Mann-Whitney test (P < .05).

RESULTS

The UAG was inversely correlated with UACR in healthy cats (P < .002, r0  = -0.40) but not in cats with CKD (P = .55; r0  = -0.15). A significant difference was found between UAG in healthy cats and those with CKD (P < .001).

CONCLUSIONS AND CLINICAL IMPORTANCE

The UAG calculation cannot be used as a substitute for UACR in cats. The clinical relevance of UAG differences between healthy cats and those with CKD remains unknown.

Development of a reference interval for urinary ammonia-to-creatinine ratio in feline patients

BACKGROUND

Disruption of acid-base homeostasis can lead to many clinical problems. Ammonia excretion by the kidneys is critical to maintaining acid-base homeostasis through bicarbonate production. Measurement of ammonia excretion may help determine if the kidneys are properly functioning in maintaining acid-base balance. Reference intervals are essential tools for clinical decision-making but do not currently exist for urinary ammonia-to-creatinine ratio (UACR) in feline patients.

OBJECTIVE

This study aimed to generate a reference interval (RI) for UACR in healthy adult cats.

METHODS

The study used samples from client-owned adult healthy cats that presented to the University of Florida Primary Care and Dentistry service (n = 92). Physical examination, serum biochemistry, urinalysis, urine ammonia, and creatinine concentrations were measured. Cats were excluded if there were significant abnormalities in their urinalysis or biochemistry panel. The RI for UACR was calculated according to the recommendation of the American Society for Veterinary Clinical Pathology. The UACR was evaluated for correlation with serum bicarbonate, weight, age, and sex.

RESULTS

The RI for UACR was 3.4-20.7 with 90% confidence intervals for the lower and upper limits of (3.0-3.7) and (16.0-23.7), respectively. No significant correlation with age, sex, or weight was found. There was no discernable relationship between serum bicarbonate and UACR.

CONCLUSIONS

Establishing an RI for UACR in healthy adult cats will allow further studies to determine if changes in UACR are observed during specific disease states.

Establishment of a reference interval for 12-hour fasted serum gastrin concentration in adult dogs

BACKGROUND

Adherence to traditional 24-h fasting periods for serum gastrin concentration in dogs can be challenging and may delay the institution of therapies for suspected hypergastrinemia. Peer-reviewed publications regarding serum gastrin reference intervals (RI) are lacking. Hypercalcemia is associated with hypergastrinemia in people; limited data exist in dogs.

OBJECTIVE

The objective of the study was to generate a RI for a 12-h fasted serum gastrin concentration in dogs and to investigate whether correlations exist with age, weight, sex, and total calcium concentration.

METHODS

Fifty-five healthy adult dogs (>1 year of age). The screening included: medical history, physical examination, CBC (15 dogs), and serum chemistry (55 dogs). Gastrin was measured via a commercial radioimmunoassay. The RI for 12-h fasted serum gastrin concentration was calculated according to the recommendations of the American Society for Veterinary Clinical Pathology. Additionally, data were evaluated for correlation with selected variables.

RESULTS

The RI for serum gastrin following a 12-h fasting period was 15.1-78.9 ng/L with 90% confidence intervals for the lower and upper limits of 14.0-22.9 and 68.3-83.0 ng/L, respectively. A generalized linear model did not detect significant relationships between gastrin and age (P = 0.48), sex (P = 0.30), weight (P = 0.93), or total calcium concentration (P = 0.84).

CONCLUSIONS

A 12-h fasted serum gastrin concentration RI has been established. Given the limited range of serum calcium concentrations in our healthy study population, additional investigations are needed to determine the effects of hypercalcemia on serum gastrin concentrations in dogs and for any potential clinical consequences thereof.