Underrecognition and Underestimation of Disturbances in Calcium-Phosphate Balance in Kidney Transplant Recipients

Phosphate balance during dialysis and after kidney transplantation in patients with chronic kidney disease

PURPOSE OF REVIEW

In patients with chronic kidney disease (CKD), hyperphosphatemia is associated with several adverse outcomes, including bone fragility and progression of kidney and cardiovascular disease. However, there is a knowledge gap regarding phosphate balance in CKD. This review explores its current state, depending on the stage of CKD, dialysis modalities, and the influence of kidney transplantation.

RECENT FINDINGS

Adequate phosphate control is one of the goals of treatment for CKD-mineral and bone disorder. However, ongoing studies are challenging the benefits of phosphate-lowering treatment. Nevertheless, the current therapy is based on dietary restriction, phosphate binders, and optimal removal by dialysis. In the face of limited adherence, due to the high pill burden, adjuvant options are under investigation. The recent discovery that intestinal absorption of phosphate is mostly paracellular when the intraluminal concentration is adequate might help explain why phosphate is still well absorbed in CKD, despite the lower levels of calcitriol.

SUMMARY

Future studies could confirm the benefits of phosphate control. Greater understanding of the complex distribution of phosphate among the body compartments will help us define a better therapeutic strategy in patients with CKD.

Surgical Treatment of Hyperparathyroidism After Kidney Transplant

Chronic renal impairment is often associated with complex bone disorders. Improvement of secondary hyperparathyroidism (HPT) is expected after kidney transplant (KT) if the glomerular filtration rate is normalized.

PATIENTS AND METHODS

There were 888 KTs performed between 1996 and 2017 at our department. A total of 558 general patients have been operated on for HPT during the same period. The 2 populations had a common part: out of the 558, a total of 69 (12.4%) were in end-stage renal failure when operated on because of secondary HPT. That also means that 7.8% of all KTs were associated with HPT. Retrospective, single-center analysis was performed using the patients' medical records. The aim of our study was to analyze the results of parathyroidectomies after KT.

RESULTS

Parathyroid surgery was performed on 19 patients (2.14%) because of HPT after KT. The applied surgical technique was total parathyroidectomy with autotransplant in 6 cases, subtotal parathyroidectomy in 3 cases, and selective parathyroidectomy in 10 cases. In all cases, histology revealed benign disease. Complications were observed in 10 cases (52%); there were 6 cases of postoperative hypocalcaemia (31.58%), 1 case of transient laryngeal recurrent nerve paresis (5.26%), and 6 cases of recurrent HPT (31.58%).

SUMMARY

The first step of HPT management is calcimimetic drug treatment. It is essential to prevent possible complications with regular laboratory monitoring. If the proper conservative therapy is refractory or severe in complications, surgery should be chosen. If the patient is already waiting for a KT, it is worth performing the parathyroid surgery before KT. Close collaboration with endocrinologists and nephrologists is needed to achieve successful therapy.

Influence of Pre-renal Transplant Secondary Hyperparathyroidism on Later Evolution After Transplantation

Persistence of secondary hyperparathyroidism (SHPT) is common after renal transplantation. Good diagnosis and treatment are important to avoid complications. The objective of our work was to perform a retrospective analysis of the evolution of SHPT after renal transplantation. We selected patients who had received a kidney transplant at our hospital between 2000 and 2014. The biochemical variables of chronic kidney disease-metabolic bone disorders (CKD-MBD) were collected at pretransplantation and at 3, 6, 12, and 24 months post-transplantation. Treatments related to SHPT were also analyzed. Five hundred forty-three renal transplants were included. The average preoperative parathyroid hormone (PTH) was 241.14 pg/mL, 115.7 pg/mL at 3 months, and at 12 and 24 months postoperatively, PTH levels stabilized to 112 pg/mL. Treatment related to SHPT was present in 27.3% of patients during the preoperative period, 40.4% at 3 months postoperatively, 24.2% at 12 months postoperatively, and 23.2% at 24 months postoperatively. There was a significant association between requiring some type of treatment preoperatively and the rest of the postoperative periods (P < .005). The sample was later divided into 3 groups based on preoperative PTH (1: <150 pg/mL, n = 223 [41.1%]; 2: 150-300 pg/mL, n = 173 [31.9%]; 3: >300 pg/mL, n = 147 [27.1%]) and their evolutions were compared. Higher levels of postoperative PTH in group pre-PTH 3 were observed. Group 3 also presented with greater need for treatment in the postoperative periods, with significant association (P < .05). A regression analysis was performed and found that postoperative PTH were dependent on preoperative PTH adjusted by glomerular filtration. In conclusion, parameters related to CKD-MBD (mainly PTH) after kidney transplant, dependent on preoperative levels and glomerular filtration. Patients with a greater grade of SHPT presented with higher levels of postoperative PTH despite receiving more intensive treatment.

Vitamin D deficiency and anemia is highly prevalent and dependent on the etiology of heart failure: A pilot study

BACKGROUND

Anemia and vitamin D deficiency are common factors in chronic heart failure (CHF). The aim of this study was to assess vitamin D levels as well as its binding protein and anemia in relation to a cause of CHF: coronary heart disease, valvular disease and cardiomyopathy.

METHODS

One hundred and sixteen consecutive patients (36 females and 80 males) with CHF were admitted for percutaneous coronary interventions (PCI). Hemoglobin concentration, serum creatinine, B-type natriuretic peptide (BNP), 25-hydroxyvitamin D [25(OH)D] and its binding protein-VDBP were measured.

RESULTS

The prevalence of anemia was 22%. BNP was the highest in the group with coronary artery disease. Ejection fraction was the lowest in cardiomyopathy group. 25(OH)D was lowest in valvular disease group, significantly lower than in the coronary artery group. A similar pattern of change showed vitamin D binding protein. The prevalence of vitamin D deficiency (level below 20 ng/mL) in the whole group was 95%, in 49% of the patients 25(OH)D was below 10 ng/mL. In univariate analysis 25(OH)D correlated with hemoglobin, red blood cell count, hematocrit, mean corpuscular volume and BNP in patients with CHF in the whole group. In multiple regression analysis, predictors of 25(OH)D were estimated, glomerular filtration rate, BNP and valvular disease.

CONCLUSIONS

25(OH)D deficiency is common in CHF patients. Valvular disease is associated the most severe vitamin D deficiency and worsened kidney function. A higher prevalence of anemia in CHF due to coronary heart disease may be associated with wider use of angiotensin converting enzyme inhibitors and acetylsalicylic acid. Heart and kidney function are predictors of 25(OH)D level in the patients of this study.