Clinical practice guideline for renal hypouricemia (1st edition)

Renal hypouricemia (RHUC) is a disease caused by dysfunction of renal urate reabsorption transporters; however, diagnostic guidance and guidelines for RHUC have been lacking, partly due to the low evidence level of studies on RHUC. This review describes a world-first clinical practice guideline (CPG) and its first version in English for this condition. It was developed following the "MINDS Manual for Guideline Development" methodology, which prioritizes evidence-based medicine. It was published in Japanese in 2017 and later translated into English. The primary goal of this CPG is to clarify the criteria for diagnosing RHUC; another aim is to work towards a consensus on clinical decision-making. One of the CPG's unique points is that it contains textbook descriptions at the expert consensus level, in addition to two clinical questions and recommendations derived from a systematic review of the literature. The guidance shown in this CPG makes it easy to diagnose RHUC from simple blood and urine tests. This CPG contains almost all of the clinical foci of RHUC: epidemiology, pathophysiology, diagnostic guidance, clinical examinations, differential diagnosis, and complications, including exercise-induced acute kidney injury and urolithiasis. A CPG summary as well as a clinical algorithm to assist healthcare providers with a quick reference and notes from an athlete for both physicians and patients are included. We hope that this CPG will help healthcare providers and patients to make clinical decisions, and that it will promote further research on RHUC.

Feasibility of long-term continuous subcutaneous magnesium supplementation in a patient with irreversible magnesium wasting due to cisplatin

A 39-year-old woman presented with severe, uncontrolled and irreversible hypomagnesaemia, following cisplatin treatment in her childhood. Because high-dose oral magnesium supplementation therapy was insufficient and not tolerated, continuous subcutaneous magnesium supplementation was successfully instituted and continued in the outpatient setting. This case demonstrates that continuous subcutaneous magnesium supplementation is effective in maintaining magnesium levels within the normal range, is well tolerated and may provide a long-term solution for chronic hypomagnesaemia due to intractable renal losses.

A Practical Approach to Hypocalcaemia in Children

Hypocalcaemia is one of the commonest disorders of mineral metabolism seen in children and may be a consequence of several different aetiologies. These include a lack of secretion or function of parathyroid hormone, disorders of vitamin D metabolism and abnormal function of the calcium-sensing receptor. A practical approach to the investigation, diagnosis and subsequent management of hypocalcaemic disorders is presented.

[A case of hypomagnesemia linked to refractory hypokalemia and hypocalcemia with short bowel syndrome]

We report a case of a 59-year old Japanese woman with short bowel syndrome, whose hypokalemia and hypocalcemia were successfully treated with magnesium (Mg) supplementation. Two years previously, she underwent Mile's operation for advanced rectal cancer, which could have been the cause of subsequent extensive resection of the small intestine by strangulation. After serial resection, she gradually developed chronic diarrhea and anorexia. Three weeks before admission, she developed general fatigue and tetany, and was hospitalized at another hospital. On admission, her serum K and Ca were 2.5 mEq/L and 4.3 mg/dL, respectively, hence regular fluid therapy containing potassium (K) and calcium (Ca) was provided following admission. However, her hypokalemia and hypocalcemia persisted, and she also displayed renal dysfunction and thereafter was transferred to our department for further evaluation and treatment. Since the laboratory tests revealed severe hypomagnesemia (0.4 mg/dL), we started intravenous Mg supplementation together with fluid therapy containing K and Ca. After the combination therapy, her clinical symptoms and electrolyte disorders were remarkably improved within a week. As Mg is essential for PTH secretion in response to hypocalcemia and to inhibit the K channel activity that controls urinary K excretion, hypomagnesemia can cause hypocalcemia and hypokalemia, which is refractory to repletion therapy unless Mg is administered. Therefore, for patients who present with signs of Mg deficiency, early and accurate diagnosis of Mg deficiency should be made and corrected.

Gitelman Syndrome: Report of Three Cases and Literature Review

Gitelman syndrome (GS) is a rare autosomal recessive, inherited renal tubular disorder. Herein, we report three cases of GS, one sporadic case and two siblings. They have typical laboratory findings, including hypokalemia, metabolic alkalosis, hypomagnesemia, and hypocalciuria. All of them were treated with oral potassium and magnesium supplements. They received regular pediatric clinic follow-up to check electrolytes and monitor development. These three cases reminded us that doctors should be alert to unexplained hypokalemia, which is usually the initial presentation of GS.

A serum potassium level above 10 mmol/l in a patient predisposed to hypokalemia

BACKGROUND

A 58-year-old man, previously diagnosed with Bartter's syndrome, presented with a short history of vomiting, diarrhea and weakness. He had severe hyperkalemia (serum potassium levels >10 mmol/l), which was successfully managed. Post hoc investigation suggested that the patient had Gitelman's rather than Bartter's syndrome.

INVESTIGATIONS

Physical examination, urine and blood analyses, chest radiography, electrocardiogram, renal ultrasound, and genetic analysis focusing on the SLC12A3 gene, which encodes the thiazide-sensitive Na/Cl cotransporter.

DIAGNOSIS

Gitelman's syndrome and hyperkalemia secondary to acute renal failure plus exogenous potassium supplementation.

MANAGEMENT

Intravenous calcium gluconate, insulin and dextrose administration. Temporary continuous venovenous hemodiafiltration. Genetic confirmation of the underlying molecular defect. Long-term treatment for Gitelman's syndrome with oral potassium and magnesium supplements and epithelial sodium channel-blocking drugs. Review of patient education regarding renal salt-wasting syndromes.

[Familial hypomagnesemia with hypercalciuria and nephrocalcinosis. Association with ocular abnormalities]

BACKGROUND

Familial hypomagnesemia with hypercalciuria and nephrocalcinosis is an unusual disease that usually leads to end-stage renal failure. There is no specific treatment and, to a variable degree, patients with this disease present ocular abnormalities. The illness is due to a defect in the reabsorption of magnesium and calcium at the thick ascending limb of Henle because of a mutation of the PCLN-1 gene, which encodes a protein, paracellin-1, which intervenes in the reabsorption of both cations.

OBJECTIVE

To review outcome and the incidence of ocular abnormalities in our patients and in cases described in Spain and to compare the incidence found with that in groups from other countries.

METHOD

Retrospective study of a group of patients with familial hypomagnesemia with hypercalciuria and nephrocalcinosis diagnosed at a hospital.

RESULTS

There were six girls and three boys with clinical symptoms of polyuria, polydipsia, and less frequently, urinary tract infections and lithiasis. All had hypomagnesemia, hypercalciuria and nephrocalcinosis. Five of the patients had renal failure at diagnosis and four underwent transplantation without recurrence. Eight patients had diverse ocular abnormalities. Eighty-one percent of Spanish patients had ocular abnormalities compared with 24 % of those from other countries. There was no evidence of successful medical treatment.

CONCLUSIONS

Almost half of the patients presented chronic renal failure at diagnosis and most of the patients reached end-stage renal failure in the second or third decade of life. Normal glomerular filtration rate was found only in patients diagnosed at an early age. The most frequent extra-renal association in Spanish patients (81 %) corresponded to ocular abnormalities. Effective treatment consists of kidney transplantation that completely corrects the tubular disorder.

Hypokalemic metabolic alkalosis--three case reports

The two most common forms of inherited normotensive hypokalemic metabolic alkalosis are Bartter's and Gitelman's syndromes. Bartter's syndrome typically present with normal or increased calcium excretion. Hypomagnesemia occurs in only one third of affected individuals. In contrast, hypomagnesemia and hypocalciuria are considered hallmarks of Gitelman's syndrome. In most patients, the symptom of muscle weakness and polyuria occur early in life, which may be attributed to potassium depletion. Despite hyperaldosteronism, the patients tend to be normotensive, which is at least explained by vascular hyperresponsiveness to prostaglandins. Therapeutic approaches to Bartter's and Gitelman's syndromes include potassium supplementation, prostaglandin synthesis inhibitors (nonsteroid anti-inflammatory agents), aldosterone antagonists and converting enzyme inhibitors. Three patients with hypokalemia, normal blood pressure, metabolic alkalosis, hyperreninemia and hyperaldosteronism are described. Two patients had Bartter's syndrome and one patients had Gitelman's syndrome.

Monogenic tubular salt and acid transporter disorders

In this review I will briefly discuss two major categories of inherited renal tubular transport disorders: those primarily affecting sodium and potassium (whether retention or wasting), and the primary renal acidopathies. The kidney does not of course carry out any of its myriad homeostatic functions in a vacuum, and interactions with other systems form an important part of the overall picture. This is perhaps most marked in the context of salt homeostasis, where the endocrine system, particularly the mineralocorticoid axis and aldosterone, are closely dovetailed. While these disorders are in general rare, the insights gained in understanding their molecular bases have added significantly to our understanding of normal human physiology. The hope is that these findings may in the future prove relevant to the understanding and treatment of more common disorders.

Pseudohypoaldosteronism

Three children, two of whom were siblings, had pseudohypoaldosteronism. The features of this condition include failure to thrive, hyperkalemia, metabolic acidosis, salt wasting, elevated peripheral renin activity, and increased plasma aldosterone concentration. Hyperplasia of juxtaglomerular apparatus was seen in a renal biopsy specimen from one of these patients. Administration of large quantities of salt normalized the serum electrolyte abnormalities and permitted normal growth. Furthermore, the serum electrolyte abnormalities were prevented by administration of increased amounts of salt to one of these children from birth.