Calcium and Phosphorus Homeostasis in Dogs with Spontaneous Chronic Kidney Disease at Different Stages of Severity

Background: Studies in dogs with experimental chronic kidney disease (CKD) have demonstrated that abnormalities of calcium-phosphorus (Ca-P) homeostasis occur frequently and have a negative effect on kidney function and survival. However, the prevalence of these alterations in dogs with naturally occurring CKD at different stages of severity has not yet been investigated.
Hypothesis: Abnormalities of Ca-P metabolism occur early in the course of CKD with an increased prevalence in more severe stages.
Animals: Fifty-four dogs with CKD and 22 healthy dogs.
Methods: Blood and urine samples were obtained for a CBC, biochemistry, determination of parathyroid hormone (PTH), calcitriol, and ionized calcium concentrations and urinalysis. Based on urine protein/creatinine ratio and serum creatinine concentration, dogs were grouped according to the IRIS classification for CKD.
Results: Hyperparathyroidism (HPTH) (PTH ≥ 48 pg/mL) was diagnosed in 41 (75.9%) dogs with CKD. Its prevalence increased from 36.4% (stage 1) to 100% (stage 4). Hyperphosphatemia ( P > 5.5 mg/dL) was present in 37 (68.5%) dogs; increasing in prevalence from 18% (stage 1) to 100% (stage 4). Receiver-operating characteristic curve analysis showed that serum phosphorus concentration in the 4.5–5.5 mg/dL range correctly identified the presence of HPTH in most dogs. Calcitriol concentration progressively decreased in dogs with CKD and differences became statistically significant by stage 3.
Conclusion and Clinical Relevance: HPTH and hyperphosphatemia occur frequently in dogs with naturally occurring CKD, even at early stages of CKD in some dogs. These findings highlight the importance of monitoring these parameters early in the course of CKD.     

Safety and efficacy of oral low-volume sodium phosphate bowel preparation for colonoscopy in dogs

BACKGROUND: Sodium phosphate (NaP) is a low-volume, hyperosmolar laxative that is an effective bowel-cleansing agent in humans. HYPOTHESIS: NaP will be as safe and efficacious as polyethylene glycol (PEG) bowel preparation for colonoscopy in dogs. ANIMALS: Eight purpose-bred healthy dogs. METHODS: In phase I, standard (NaP and enemas; NaP(1)) and control preparations (PEG and enemas) were compared in a crossover design to determine the safety and efficacy of NaP. Serial clinical and serum analytical evaluations were used to determine the safety of NaP. In phase II, the efficacy of the standard NaP preparation was compared with 3 other NaP variations, which excluded enema or included bisacodyl, with or without enemas in a crossover design. An observer blinded to the bowel preparation assigned a score of 1-4 (1=clean colon; 4=unacceptable colon cleansing preventing adequate endoscopic evaluation) to each of 5 regions of the colon. RESULTS: The mean total colon cleansing score (TCS), defined as the sum of scores from each region, of the control (9.4) was less than NaP(1) (13.6) (P < 0.05). There were no significant differences in regional or TCS for the remaining 4 NaP protocols. NaP(1) resulted in moderate, but clinically occult, hyperphosphatemia and hypocalcemia, which resolved within 24 hours. CONCLUSIONS AND CLINICAL IMPORTANCE: Despite the safety and ease of administration of the NaP preparations, the NaP bowel-cleansing preparations used in this study cannot be recommended for use because of the inadequate quality of bowel preparation compared with the protocol using PEG-containing fluids.     

Phosphorus homeostasis in dairy cows with abomasal displacement or abomasal volvulus

Abnormal phosphorus homeostasis occurs in dairy cows with an abomasal displacement or volvulus. The goal of this study was to identify potential mechanisms for hypophosphatemia and hyperphosphatemia in cows with a left displaced abomasum (LDA), right displaced abomasum (RDA), or abomasal volvulus (AV). Accordingly, the results of preoperative clinicopathologic analyses for 1,368 dairy cows with an LDA (n = 1,189), RDA, or AV (n = 179) (data set 1) and for 44 cows with an AV (data set 2) were retrieved. Laboratory values were compared by Student's t-tests, and correlation and regression analyses were performed. Thirty-four percent of the animals from data set 1 (463/1,368) were hypophosphatemic (serum phosphorus concentration ([Pi]) < 1.4 mmol/L), and 9% (122/1,368) were hyperphosphatemic ([Pi] >2.3 mmol/L). Serum [Pi] was significantly lower (P < .05) in cows with an LDA (1.60 +/- 0.53 mmol/L; mean +/- SD) than in cows with an RDA or AV (1.85 +/- 0.68 mmol/L). For cows with an LDA, [Pi] was correlated with serum urea nitrogen concentration ([SUN]) (r = 0.34) and serum concentration of magnesium ([Mg]) (r = 0.20). For cows with an RDA or AV, linear correlations existed between [Pi] and [SUN] (r = 0.45), [Mg] (r = 0.43), and serum chloride concentration ([Cl]) (r = -0.27). Stepwise logistic regression analysis indicated that low [SUN] and the diagnosis of an LDA had the strongest associations with hypophosphatemia. In cows with hyperphosphatemia, [Pi] was most strongly associated with azotemia. In cows with an AV, the strongest correlations with [Pi] were found for [SUN] and serum creatinine. We conclude that hypophosphatemia in cows with an LDA is primarily due to decreased feed intake. In contrast, hyperphosphatemia in cattle with an RDA or AV appears to result from dehydration and decreased renal blood flow.