Oral Manifestations of Chronic Kidney Disease and Renal Secondary Hyperparathyroidism: A Comparative Review

Blood fibroblast growth factor 23 concentration in cats with and without chronic kidney disease: a scoping review

OBJECTIVES

This study undertook a scoping review of research on blood fibroblast growth factor 23 (FGF-23) concentrations in healthy non-azotemic cats and cats with chronic kidney disease (CKD) to describe the volume and nature of existing literature, to determine whether published studies provide adequate evidence to support the use of FGF-23 as a biomarker in clinical practice and to identify any existing gaps in knowledge.

METHODS

PRISMA Extension for Scoping Reviews guidelines were used to design and perform the scoping review. Online databases were used to identify observational and clinical studies of blood FGF-23 concentrations in healthy cats and cats with CKD published before December 2022. Study and population characteristics and descriptive data on FGF-23 concentrations were extracted.

RESULTS

A total of 205 publications were reviewed; 17 were retained for inclusion. Most studies were retrospective. Most studies included cats with International Renal Interest Society stage 2-4 CKD, with some variation. Key concepts explored in the literature include FGF-23 concentrations by CKD stage, effect of dietary phosphate restriction on FGF-23 concentrations, relationship between FGF-23 concentrations and blood phosphorus, calcium and magnesium concentrations, and FGF-23 concentrations in cats with progressive CKD. FGF-23 concentrations tended to be higher in cats with CKD compared with healthy cats, with an overlap between healthy and CKD populations, and there was significant variation within stages of CKD.

CONCLUSIONS AND RELEVANCE

FGF-23 is a biomarker of interest for the management and monitoring of phosphate overload in cats. Studies support several potential clinical applications for measuring FGF-23 concentration in practice; however, evidence is limited. Research on FGF-23 in cats with CKD would benefit from longitudinal, prospective studies that standardize CKD diagnosis and categorize cats by stage using current guidelines. Studies should include cats with early-stage, non-azotemic CKD and use commercially available assays so such results are comparable across studies.

The circulating renin-angiotensin-aldosterone system is down-regulated in dogs with glomerular diseases compared to other chronic kidney diseases with low-grade proteinuria

Glomerular diseases (GD) lead to a variety of disorders of the vascular and the total body water volumes. Various pathomechanisms, including vascular underfill and overfill, have been suggested to explain these disturbances. Accordingly, the circulating renin-angiotensin-aldosterone system (cRAAS) is expected to be activated as either a cause or a result of these fluid disorders. The aim of this study was to characterize the activity of the cRAAS in dogs with GD and to evaluate its relationship with the vascular volume status. In a prospective study, we evaluated the plasma renin activity and the serum aldosterone concentration in 15 dogs with GD. Their fluid volume status was estimated with clinical variables reflecting volemia and hydration, echocardiographic volume assessment, N-terminal pro B-type natriuretic peptide, blood urea nitrogen:creatinine ratio, and the urinary fractional excretion of sodium. Ten dogs with chronic kidney disease (CKD) with matching degree of azotemia were recruited as controls. The activity of the cRAAS was low in 10 dogs, normal in 3 dogs, high in 1 dog and equivocal (high renin—low aldosterone) in 1 dog with GD. These dogs had a lower cRAAS activity than dogs with CKD (p = 0.01). The clinical evaluation showed 8 hypovolemic and 7 non-hypovolemic dogs; 3 dehydrated, 9 euhydrated and 3 overhydrated dogs. The cRAAS activity was not different between hypovolemic and non-hypovolemic dogs. The down-regulated cRAAS without obvious association with the clinical volume status of these dogs with GD, suggests different mechanisms of fluid volume dysregulation in dogs with GD than previously assumed. This finding however should be confirmed in a focused larger scale study, as it may influence the use of cRAAS blockers as part of the standard therapy of GD in dogs.

Renal secondary hyperparathyroidism should be considered a differential diagnosis in forensic cases where animal abuse is suspected

This case description reports an adult dog with multiple rib fractures that was initially suspected to be the victim of non-accidental trauma, but eventually was diagnosed with severe chronic interstitial nephritis and renal secondary hyperparathyroidism leading to fibrous osteodystrophy and multiple pathological fractures. The importance of the specific expertise of a dedicated expert panel on animal abuse is discussed. This case illustrates the significance of the identification of normal, pathological, and breed-related variations within an animal in addition to forensic expertise, emphasizing that the presence of multidisciplinary teams in an expert panel on animal abuse is crucial.

Renal Osteodystrophy due to Secondary Hyperparathyroidism in a Cat

A 6 yr old neutered male mixed-breed cat presented for renal transplantation (RTx) for chronic kidney disease. Severe periodontal disease was identified, and before initiation of immunosuppressive therapy, a comprehensive oral health assessment and treatment procedure was performed to reduce the burden of existing oral infection. Dental radiography revealed diffuse, severe bone demineralization across the mandible and maxilla, with thinning of the cortices. Nasal turbinates were easily visualized owing to the decreased opacity of maxillary bone. Generalized bone resorption left teeth to appear minimally attached. A Vitamin D panel revealed a severely elevated parathyroid hormone level. Full mouth extractions were performed. Seven days following this procedure, RTx was performed. Serum creatinine concentration was within normal limits by 48 hr after surgery and remained normal until discharge 12 days after RTx. At 3.5 mo after RTx, the cat was mildly azotemic, and the parathyroid hormone level was elevated but significantly decreased from the original measurement. Secondary hyperparathyroidism is a common abnormality in cats with chronic kidney disease. However, clinical manifestations of hyperparathyroidism are rare in this species. This is a novel presentation of a cat demonstrating bone loss in the oral cavity as a result of renal secondary hyperparathyroidism.

Dystrophic mineralization in uremic dogs: an update

ABSTRACT: Pathological mineralization is the abnormal deposition of minerals in body tissues, previously injured or not. In these lesions, in addition to calcium, other minerals can be found at lower concentrations. Classically, mineralization is divided into two types: dystrophic and metastatic. However, currently, there is no consensus among researchers on the type of mineralization that occurs in uremic dogs. The objective of this study was to elucidate the type of pathological mineralization that occurs in dogs with uremic syndrome through the correlation of biochemical examinations with gross and histopathological changes, given the existence of controversial information on this theme in the specialized literature. The Shapiro-Wilk, D’Agostino and Pearson tests were used to evaluate data normality distribution, and analysis of variance (ANOVA) was applied to compare the data between more than two groups. Additionally, the Dunnett’s multiple comparison test was used in the comparison between the Control Group (CG) and the Experimental Groups (G1, G2, and G3). Serum levels of urea, creatinine, total and ionized calcium, phosphorus, calcium-phosphorus product (CPP), parathyroid hormone (PTH), and albumin of 40 azotemic dogs with chronic kidney disease (CKD) were evaluated. Dogs were categorized by degree of azotemia (mild, moderate, and severe). Ionized hypocalcemia was observed in 97.5% (39/40) of the dogs, and no animals presented ionized hypercalcemia. Hyperphosphatemia was frequent (62.5%), especially in dogs with severe azotemia. PTH concentration increased with progression of azotemia, and high PTH levels were verified in 100% of the dogs with severe azotemia. CPP >60mg2/dl2 was observed in 75% (30/40) of the dogs. Of the 29 dogs that died during the study period, 16 were necropsied. Soft tissue mineralization was observed in 93.7% (15/16) of these dogs at gross and histopathological evaluation (HE and Von Kossa), regardless of the degree of azotemia, in nine organs/tissues: kidneys (75%), lungs (50%), stomach (31.2%), heart (25%), larynx (25%), intercostal muscles (25%), aorta (6.2%), intestines (6.2%), and tongue (6.2%). In one animal, the serosa of all segments of the small intestine showed whitish, rough, irregular, multifocal plaques of varying sizes, confirmed by histopathology as dystrophic mineralization of the longitudinal outer muscular layer, which presented necrosis of coagulation and of the intestinal serosa. This intestinal lesion has not been described in dogs with uremic syndrome to date. In conclusion, the laboratory and histopathologic data previously described, especially regarding tissue and vascular mineralization, which occur in association with previous degenerative/necrotic lesions in the absence of hypercalcemia in dogs with CKD, assist with clarifying inconsistencies found in the existing literature. Therefore, conceptually, mineralization that occurs in uremic dogs should be considered dystrophic.