Risk factors and implications associated with ultrasound-diagnosed nephrocalcinosis in cats with chronic kidney disease.

BACKGROUND: Microscopic nephrocalcinosis is a common pathological feature of chronic kidney disease (CKD) in cats. Detection of macroscopic nephrocalcinosis using ultrasonography and its implications remain unexplored. OBJECTIVES: Identify risk factors associated with ultrasound-diagnosed nephrocalcinosis and evaluate the influence of nephrocalcinosis on CKD progression. ANIMALS: Thirty-six euthyroid client-owned cats with CKD. METHODS: Prospective cohort study. Cats with CKD with and without ionized hypercalcemia were enrolled for renal ultrasonography. Cats were categorized according to the presence or absence of ultrasound-diagnosed nephrocalcinosis. Binary logistic regression was performed to identify nephrocalcinosis risk factors. The influence of nephrocalcinosis on CKD progression was assessed using linear mixed models. RESULTS: Ultrasound-diagnosed nephrocalcinosis was evident in 61% of CKD cats overall, with increased prevalence (81%) in those with hypercalcemia. At enrollment, higher blood ionized calcium concentration (odds ratio [OR], 1.27 per 0.1 mg/dL; P = .01), plasma phosphate concentration (OR, 1.16 per 0.1 mg/dL; P = .05), plasma creatinine concentration (OR, 1.29 per 0.1 mg/dL; P = .02) and alanine aminotransferase activity (OR, 2.08 per 10 U/L; P = .04) were independent nephrocalcinosis risk factors. The rate of change in log-transformed fibroblast growth factor-23 differed significantly between groups (P = .04). Cats with CKD and nephrocalcinosis had increasing plasma creatinine concentrations (.03 ± .01 mg/dL/month; P = .04) and phosphate concentrations (.06 ± .02 mg/dL/month; P < .001) and decreasing body weight (.02 ± .01 kg/month; P < .001) over time. CONCLUSIONS AND CLINICAL IMPORTANCE: Nephrocalcinosis is prevalent in cats with CKD, especially in those with hypercalcemia. This pathological feature appears to be associated with CKD progression in cats.

Detection of nephrocalcinosis using ultrasonography, micro-computed tomography, and histopathology in cats.

BACKGROUND: Identification of nephrocalcinosis in cats with chronic kidney disease (CKD) is of clinical interest but the ability of ultrasonography to detect nephrocalcinosis is uncertain. OBJECTIVES: To compare ultrasonography, micro-computed tomography (µCT) and histopathology for identification of nephrocalcinosis. ANIMALS: Twelve kidneys from 7 euthyroid client-owned cats with CKD. METHODS: Descriptive study. Renal ultrasonography was performed ante-mortem for nephrocalcinosis detection. Kidneys were grouped based on nephrocalcinosis: present, suspected, or absent. When cats died, necropsy was performed. Renal tissue was evaluated using µCT for macroscopic nephrocalcinosis, and nephrocalcinosis volume-to-kidney tissue ratio (macro-VN:KT) and sagittal nephrocalcinosis area-to-kidney tissue ratio (macro-AN:KT) were calculated. Each kidney subsequently was bisected longitudinally, formalin-fixed, and paraffin-embedded for microscopic nephrocalcinosis assessment using von Kossa and Alizarin red staining with AN:KT (VK-micro-AN:KT and AR-micro-AN:KT) quantified using ImageJ. Data are presented as median (range). Relationships between macroscopic and microscopic AN:KT were assessed using Spearman's correlation. RESULTS: Nephrocalcinosis by ultrasonography was considered to be absent in 3, suspected in 3, and present in 5 kidneys; 1 kidney had nephrolithiasis with nephrocalcinosis. The macro-VN:KT was 0.001%, 0.001%, and 0.019%, and the macro-AN:KT was 0.08%, 0.30%, and 1.47%, respectively. Histologically, VK-micro-AN:KT was 0.21%, 2.85%, and 4.56%, and AR-micro-AN:KT was 1.73%, 5.82%, and 8.90% for kidneys where ultrasonographic macro-nephrocalcinosis was absent, suspected, or present, respectively. A strong correlation was identified between macroscopic (macro-AN:KT) and microscopic (VK-micro-AN:KT) nephrocalcinosis (rs = 0.76; P = .01). CONCLUSIONS AND CLINICAL IMPORTANCE: Ultrasonographically diagnosed nephrocalcinosis correlates well with macroscopic and microscopic nephrocalcinosis at necropsy despite their separation in time.

Diet-induced nephrocalcinosis in aquarium-raised juvenile spotted wolffish Anarhichas minor.

Wolffish are regularly housed in aquaria, but little data on their husbandry and health is available for caretakers. High occurrence rates of nephrocalcinosis and urolithiasis have been observed in Atlantic Anarhichas lupus and spotted A. minor wolffish housed at 2 Canadian zoological institutions. To explore the effect of diet on nephrocalcinosis and urolithiasis development, a 16 mo prospective study was conducted. A total of 32 juvenile spotted wolffish were randomly assigned to one of 4 experimental groups fed exclusively with the following diet: (1) Skretting® Europa 18 pellets; (2) Mazuri® LS Aquatic Carni-Blend Diet Formula; (3) vitamin-supplemented fish-based diet, and (4) vitamin-supplemented invertebrate-based diet. Urinalysis, radiographs, and complete necropsies were performed at the end of the study. None of the wolffish developed uroliths during the study period. All specimens fed with the fish-based and invertebrate-based diets developed nephrocalcinosis, whereas this condition was seen in 12.5 and 0% of the fish in the Skretting® and Mazuri® groups, respectively. Affected wolffish often presented with oxalate crystalluria and increased radiodensity of the posterior kidneys. Urinalysis and radiographic study were considered useful in the antemortem diagnosis of nephrocalcinosis. None of the previously published risk factors for the development of nephrocalcinosis in fish were supported by the results of this study. However, nutritional analyses of the 4 diets suggest that high dietary levels of gelatin or vitamin C or low levels of vitamin E could be potential risk factors for the development of nephrocalcinosis in spotted wolffish and thus warrant further study.

Glomerulocystic kidney in two red piranhas Pygocentrus nattereri.

Glomerulocystic kidney (GCK) is defined by a dilatation of the Bowman's space (greater than 2 times the normal size) of more than 5% of all glomeruli. Although GCK has been occasionally documented in dogs, cats, and humans with renal failure, in fish, reports of spontaneous GCK are rare. For the present study, 2 captive adult red piranhas Pygocentrus nattereri from a closed population were submitted for post-mortem examination. Clinical history included lethargy, inappetence, dyspnea, and altered buoyancy. Macroscopically, the fish displayed coelomic distension and ascites. The kidneys were markedly enlarged and dark yellow. Histologically, Bowman's space was noticeably dilated, occasionally with atrophic glomerular tufts. Degeneration and necrosis of the tubular epithelium, infiltration, and nephrocalcinosis were also present. To the authors' knowledge, this present study is the first report of spontaneously occurring GCK in red piranhas and freshwater fish in general. Despite being rare, GCK is a condition with the potential to impair the health of fish and mammals, and further studies are needed to shed new light on this condition.

Nephrocalcinosis in juvenile farmed Atlantic Salmon (Salmo salar) may be linked to osmoregulatory stress.

Nephrocalcinosis is a widespread challenge in intensive production of salmon smolt. There is however no consensus on its aetiology, which makes it problematic to implement proper measures to limit its development. We performed a survey of nephrocalcinosis prevalence and environmental factors in 11 different hatcheries in Mid-Norway as well as a 6-month monitoring in one of the hatcheries. A multivariate analysis indicated that the most influencing factor for the prevalence of nephrocalcinosis was the supplementation of sea water during smolt production. In the 6-month monitoring, the hatchery introduced salinity in the production water prior to the change in day length. Mismatch in those environmental signals may increase the risk for developing nephrocalcinosis. Salinity fluctuations prior to smoltification can cause osmotic stress and result in unbalanced levels of ions in fish blood. This was clearly illustrated in our study, as the fish experienced chronic hypercalcaemia and hypermagnesaemia. Both magnesium and calcium are excreted over the kidneys and it is possible that their prolonged, elevated levels in plasma resulted in an oversaturation of the urine when finally excreted. This again could have led to the aggregation of calcium deposits within the kidney. This study indicates a relationship between osmotic stress induced by salinity changes in juvenile Atlantic salmon and the development of nephrocalcinosis. Other factors that may affect the severity of nephrocalcinosis are currently subjects for discussion.

Gene expression patterns in Atlantic salmon (Salmo salar) with severe nephrocalcinosis.

Nephrocalcinosis is a common disorder in farmed Atlantic salmon, but the consequences for the fish physiology are not well understood. We performed a transcriptome study in kidneys of Atlantic salmon (Salmo salar) smolts without and with severe chronic nephrocalcinosis (NC). The study revealed that numerous genes are differentially expressed in fish with NC compared with healthy salmon. The most evident changes in gene expression patterns in the NC group were a massive downregulation of metabolism and energy production, upregulation of signalling pathways important for tissue repair and function maintenance and upregulation of inflammatory responses. Overall, the extensive tissue damage and the gene regulation responses that affect salmon with severe nephrocalcinosis are highly likely to have dramatic consequences on fish survival.

Risk factors and implications associated with renal mineralization in chronic kidney disease in cats.

BACKGROUND: Nephrocalcinosis is a pathological feature of chronic kidney disease (CKD). Its pathophysiological implications for cats with CKD are unexplored. OBJECTIVES: Identify nephrocalcinosis risk factors and evaluate its influence on CKD progression and all-cause mortality. ANIMALS: Fifty-one euthyroid client-owned cats with International Renal Interest Society (IRIS) stages 2-3 azotemic CKD. METHODS: Retrospective cohort study. Histopathological kidney sections were assessed for nephrocalcinosis (von Kossa stain). Nephrocalcinosis severity was determined by image analysis (ImageJ). Ordinal logistic regressions were performed to identify nephrocalcinosis risk factors. The influence of nephrocalcinosis on CKD progression and mortality risk were assessed using linear mixed model and Cox regression, respectively. Cats were categorized by their owner-reported time-averaged phosphate-restricted diet (PRD) intake, where PRD comprised ≥50%, 10-50%, or none of food intake. RESULTS: Nephrocalcinosis was rated as mild-to-severe in 78.4% and absent-to-minimal in 21.6% of cases. Higher baseline plasma total calcium concentration (tCa; odds ratio [OR] = 3.07 per 1 mg/dL; P = .02) and eating a PRD (10%-50%: OR = 8.35; P = .01; ≥50%: OR = 5.47; P = .01) were independent nephrocalcinosis risk factors. Cats with absent-to-minimal nephrocalcinosis had increasing plasma creatinine (0.250 ± 0.074 mg/dL/month; P = .002), urea (5.06 ± 1.82 mg/dL/month; P = .01), and phosphate (0.233 ± 0.115 mg/dL/month; P = .05) concentrations over a 1-year period, and had shorter median survival times than cats with mild-to-severe nephrocalcinosis. CONCLUSION AND CLINICAL IMPORTANCE: Higher plasma tCa at CKD diagnosis and PRD intake are independently associated with nephrocalcinosis. However, nephrocalcinosis is not associated with rapid CKD progression in cats.

A feline-focused review of chronic kidney disease-mineral and bone disorders - Part 2: Pathophysiology of calcium disorder and extraosseous calcification.

Derangements in mineral metabolism are one of the main entities in chronic kidney disease-mineral and bone disorder (CKD-MBD). This is the second of a two-part review of the physiology and pathophysiology of calcium homeostasis in feline CKD-MBD. While dysregulation in calcium homeostasis is known to contribute to the development of vascular calcification in CKD, evidence characterising the relationship between serum calcium concentration and nephrocalcinosis and nephrolithiasis is limited. Recently, fibroblast growth factor 23 (FGF23) and α-Klotho have gained increased research interest and been shown to be important biomarkers for the prediction of CKD progression in human patients. However, conflicting evidence exists on their role in calcium homeostasis and vascular and soft tissue calcification. This review details the pathophysiology of calcium disorders associated with CKD-MBD and its implications on vascular and soft tissue mineralisation in human and feline patients. Further prospective studies investigating the clinical consequences of calcium disturbances in cats with CKD are warranted and this may provide additional insight into the pathophysiology of feline CKD-MBD.

A multidisciplinary study of the extracutaneous pigment system of European sea bass (Dicentrarchus labrax L.). A possible relationship between kidney disease and dopa oxidase activity level.

Infectious diseases and breeding conditions can influence fish health status. Furthermore it is well known that human and animal health are strongly correlated. In lower vertebrates melano-macrophage centres, clusters of pigment-containing cells forming the extracutaneous pigment system, are widespread in the stroma of the haemopoietic tissue, mainly in kidney and spleen. In fishes, melano-macrophage centres play an important role in the immune response against antigenic stimulants and pathogens. Hence, they are employed as biomarker of fish health status. We have investigated this cell system in the European sea bass (Dicentrarchus labrax L.) following the enzyme activities involved in melanin biosynthesis. We have found a possible relationship between kidney disease of farmed fishes and dopa oxidase activity level, suggesting it as an indicator of kidney disease. Moreover variations of dopa oxidase activity in extracutaneous pigment system have been observed with respect to environmental temperature. At last, for the first time, using femtosecond transient absorption spectroscopy (Femto-TA), we pointed out that pigment-containing cells of fish kidney tissue present melanin pigments.

Diet and kidney diseases in rats.

Diet-associated kidney diseases of rats includes nephropathy in both sexes and nephrocalcinosis in females. High protein content of diets appears to be the major cause for severe nephropathy and changing the source of protein to one such as soy protein, restricting caloric intake, or modifying the diet to decrease protein consumption could decrease the severity of nephropathy. The NTP-2000 diet with lower protein content than most diets decreases the severity of nephropathy and increases the survival of Fischer 344 rats without substantial changes in growth patterns and body weights. Nephrocalcinosis, characterized by mineralization of renal tubules at the corticomedullary junction, has been reported in young and adult female rats of most strains and stocks suggesting a major contribution of female sex hormones to the development of this lesion. Calcium (Ca), phosphorous (P), magnesium (Mg), and chloride (Cl) imbalances, especially a Ca:P ratio of less than 1.0 in diet, are considered to be associated with this lesion. Most commercial diets commonly used for toxicology studies have a Ca:P molar ratio of less than 1.0. Increasing the Ca:P molar ratio to more than 1.0 and closer to 1.3 in the AIN-93 purified diet and NTP-2000 nonpurified diet prevents the development of this lesion. Genetics will predispose rats to some diseases and environmental factors will influence the severity of these diseases. Diet is one of the most important environmental factors. Diets balanced for nutrients without excesses could markedly improve the health of rats used in chronic studies leading to substantial increases in survival and thereby accomplish the objective of chronic toxicity and carcinogenicity studies.

Unusual case of metabolic bone disease in a common marmoset (Callithrix jacchus).

Metabolic bone disease was diagnosed in an 11-month-old female common marmoset (Callithrix jacchus). It was depressed, reluctant to move, and was cachectic and small for its age. Laboratory findings included anaemia, azotaemia and an inverse calcium to phosphorus ratio. The radiological findings showed simultaneous signs of osteomalacia and soft-tissue calcification. There was decreased bone density with lytic areas in the pelvis and femur, and severe bilateral nephrocalcinosis. Postmortem examination revealed marked focal dystrophic calcification of the epi- and myocardium. Calcium and vitamin D3 deficiency (nutritional secondary hyperparathyroidism) was the most likely cause of the osteomalacia.

Dietary phosphorus restriction to half the minimum required amount slightly reduces weight gain and length of tibia, but sustains femur mineralization and prevents nephrocalcinosis in female kittens.

The effects of dietary P restriction to half the recommended minimum level on growth, bone and renal mineralization and urinary composition were studied in female kittens. In two separate experiments, 8-week-old weanling kittens were fed on purified diets containing either 4.6 or 9.2 mmol P/MJ (2.8 or 5.6 g P/kg diet). In the second experiment there was an additional low-P diet in which the Ca concentration was reduced from 9.5 to 4.8 mmol/MJ (7.5 v. 3.8 g Ca/kg diet). P restriction slightly but systematically reduced weight gain (to a maximum of 16%) and growth of the tibia (by 1-4%); the former effect was statistically significant (P < 0.05) between the ages of 15 and 20 weeks in Expt 1 only, and the latter did not reach statistical significance at any time point (P > or = 0.13). No adverse effect of P restriction was found on mineralization of femur at the age of 39 weeks. Kidney Ca concentrations were significantly lowered (Expt 1, 6 v. 20 mumol/g dry weight, P < 0.001; Expt 2, 7 v. 16 mumol/g dry weight, P < 0.01) in cats fed on the low-P diets, this effect not being affected by the dietary Ca:P ratio. Urinary P concentration was significantly depressed (by 50-96%) after feeding the low-P diets (P < 0.001). P intake did not influence P, Ca and Mg retention during the period of 15 to 39 weeks of age.

Nephrocalcinosis caused by hyperparathyroidism in progression of renal failure: treatment with calcitriol.

Nephrocalcinosis is accepted to contribute to the progression of renal failure. We have reviewed evidence that nephrocalcinosis is caused directly by the excess parathyroid hormone produced in renal disease. Evidence that hyperparathyroidism in uremic patients results from calcitriol deficiency and the mechanisms by which this comes about have been discussed. We have shown that renal secondary hyperparathyroidism can be eliminated or substantially reduced without increasing blood calcium using a low-dosage regimen of calcitriol. Decreasing PTH concentrations to or near normal alleviates this hormone's toxicity to many organs, including the kidneys. Potential benefits for the uremic patient include an increase in the quality and length of life. Calcitriol treatment provides a powerful means to reduce PTH concentration in uremic patients that may not be achieved with other methods. Further prospective clinical studies of uremic dogs and cats are warranted to document preservation of renal function and histology during calcitriol treatments.

Vitamin D, within its range of fluctuation in commercial rat diets, does not influence nephrocalcinogenesis in female rats.

Massive, toxic doses of vitamin D have been shown to cause nephrocalcinosis in rats, but the effect of this vitamin within its range of fluctuation in commercial rat diets was unknown. Therefore, in two experiments with young female rats, the effect on nephrocalcinosis of a moderately increased level of vitamin D in the diet was studied, that is 5000 IU/kg versus the recommended concentration of 1000 IU/kg. This was done using purified diets with 0.5% (w/w) calcium and 0.04% magnesium containing either 0.2 or 0.6% phosphorus (P). Rats fed the diets containing 0.6% P showed severe kidney calcification compared to those fed the 0.2%-P diets. The level of vitamin D in the 0.2 and 0.6%-P diets did not affect kidney calcification. Bone density was increased after feeding diets containing 5000 instead of 1000 IU of vitamin D/kg. This study suggests that, within 28 days, a moderate increase of the amount of vitamin D in the diet has no influence on the development of kidney calcification. This in turn suggests that the variation in nephrocalcinosis severity and incidence seen in practice in rats fed different commercial diets is unlikely to be related to the different vitamin D concentrations in these diets. However, in rats fed such diets bone metabolism may be influenced differently.

A case of solanum malacoxylon toxicity in pigs.

The postmortem and histological changes seen in the kidneys, lungs and vascular system in spontaneous Solanum malacoxylon poisoning on a pig farm in Buenos Aires Province, Argentina, are reported. Macroscopic calcified plaques in the endocardium, aorta, and pulmonary artery and mineralization in renal pelvis were observed. Microscopic examinations revealed tubulonephrosis and calcification of the elastic fibers of kidney vessels. Severe calcinosis of the endocardium and elastic fibers of arteries (aorta, pulmonary, renal) were seen. In the lung, calcification of the elastic fibers of the alveolar wall and the lamina propia of the bronchia were also noted.

Nutrition and kidney calcification in rats.

Nephrocalcinosis is a 'spontaneous' disorder in rats which refers to the deposition of calcium salts in the kidney, preferably in the cortico-medullary region. Studies using defined, semi-purified diets have shown that low dietary concentrations of magnesium, high concentrations of calcium, high concentrations of phosphorus and low calcium: phosphorus ratios induce kidney calcification. Dietary phosphorus induced nephrocalcinosis in female rats is associated with increased kidney size and weight, tubular hyperplasia, fibrosis and increased excretion of albumin in urine. This suggests that nephrocalcinosis may impair kidney function. In rats fed different commercial diets the incidence of nephrocalcinosis can vary considerably. Differences in the degree of nephrocalcinosis in different experiments may negatively influence the comparability of experimental outcome, especially when this is affected by kidney function and structure. Experimental data are needed so that diets can be formulated that do not produce nephrocalcinosis without inducing other disorders.

[Pathological study on nephrocalcinosis in Fischer 344/Du Crj rats].

Histopathological examinations on nephlocalcinosis of the Fischer 344 (F344) rats were carried out. As the results of comparison on its appearance among F344, Wistar and SD strains of rats, F344 female rats showed the most severe nephrocalcinosis. Nephrocalcinosis developed between 4 weeks and 8 weeks and was likely to keep its appearance through 108 weeks of the survival period of the rats. Histologically, mineral deposit was always observed at cortico-medullary junction. It seemed to locate at the outer portion of the basement membrane of the tubular epithelium, adjacent to the capillary wall in the connective tissue. Four weeks after ovariectomy at 4 weeks of age, the rats showed a decrease in degree of nephrocalcinosis. In contrary, the rats treated with estorone following ovariectomy revealed an increase in degree of nephrocalcinosis. It was suggested that the oestrogen-type sex hormone appeared to give a role in nephlocalcinosis.