Chloride deficiency as a presentation or complication of cystic fibrosis

Characteristics of electrolyte imbalance and pseudo-bartter syndrome in hospitalized cystic fibrosis children and adolescents

INTRODUCTION

Pseudo-Bartter syndrome (PBS) is a rare manifestation of Cystic fibrosis (CF) and can often be the initial presentation in these patients, however, due to significantly overlapping symptoms it is often misdiagnosed as simple dehydration or Bartter syndrome. The objective of our study was to highlight the key features of PBS and electrolyte imbalance in CF patients helping in early and prompt diagnosis.

METHOD

We performed a retrospective study from January 2015 to December 2019 at the Aga Khan University Hospital (AKUH), Pakistan. CF patients aged from 1-18 years, admitted at AKUH were enrolled and their laboratory data and individual charts were reviewed. Patients were categorized into three groups based on their serum electrolyte profile and their clinical findings were compared.

RESULT

We enrolled 72 CF patients, out of which 42 (58%) were categorized into the Normal Electrolyte (NE) group, 19 (26%) into the Electrolyte Imbalance (EI) group and 11 (15%) in the PBS group. Out of 11 cases, 6 (54.54%) patients in PBS group presented with features consistent with PBS leading to CF diagnosis labeled as "early presenters". Mean age of patients in the PBS group was 3.81± 0.86 years and their age at diagnosis were significantly lower as compared to other groups. Gastrointestinal disturbances including diarrhea, vomiting and constipation were more common in the EI and PBS groups. Polyuria was most common in the PBS (72%) group. Length of hospital stay showed no significant difference.

CONCLUSION

Pseudo-Bartter syndrome can be a presenting feature of cystic fibrosis. Electrolyte imbalance should be anticipated in hospitalized CF children and adolescent.

Targeting chloride transport in autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is the most frequent inherited kidney disease. Transepithelial fluid secretion is one of the key factors of cystogenesis in ADPKD. Multiple studies have suggested that fluid secretion across ADPKD cyst-lining cells is driven by the secretion of chloride, essentially mediated by the CFTR channel and stimulated by increased intracellular levels of 3',5'-cyclic adenosine monophosphate. This review focuses on the pathophysiology of fluid secretion in ADPKD based on the pioneering studies of Jared Grantham and colleagues, and on the follow-up investigations from the molecular level to the potential applications in ADPKD patients. Altogether, the studies of fluid and chloride transport in ADPKD paved the way for innovative therapeutic targets to prevent cyst volume expansion and thus, kidney disease progression.

Electrolyte abnormalities in cystic fibrosis: systematic review of the literature

BACKGROUND

Cystic fibrosis per se can sometimes lead to hyponatremia, hypokalemia, hypochloremia or hyperbicarbonatemia. This tendency was first documented 60 years ago and has subsequently been confirmed in single case reports or small case series, most of which were retrospective. However, this issue has not been addressed analytically. We have therefore systematically reviewed and analyzed the available literature on this subject.

METHODS

This was a systematic review of the literature.

RESULTS

The reports included in this review cover 172 subacute and 90 chronic cases of electrolyte imbalances in patients with cystic fibrosis. The male:female ratio was 1.57. Electrolyte abnormalities were mostly associated with clinically inapparent fluid volume depletion, mainly affected patients aged ≤2.5 years, frequently tended to recur and often were found before the diagnosis of cystic fibrosis was established. Subacute presentation often included an history of heat exposure, vomiting, excessive sweating and pulmonary infection. History of chronic presentation, in contrast, was often inconspicuous. The tendency to hypochloremia, hypokalemia and metabolic alkalosis was similar between subacute and chronic patients, with hyponatremia being more pronounced (P < 0.02) in subacute compared to chronic presentations. Subacute cases were treated parenterally; chronic ones were usually managed with oral salt supplementation. Retention of urea and creatinine was documented in 38 % of subacute cases.

CONCLUSIONS

The findings of our review suggest that physicians should be aware that electrolyte abnormalities can occur both as a presenting and a recurring feature of cystic fibrosis.

Nanoduct sweat conductivity measurements in 2664 patients: relationship to age, arterial blood gas, serum electrolyte profiles and clinical diagnosis

Background

The Nanoduct^® device has acceptable diagnostic accuracy, but there is not enough systematic data supporting its usage in the diagnosis of cystic fibrosis (CF).

Methods

A retrospective review of patients with an indication for the sweat test was conducted. The conductivity test was repeated in patients who had values higher than 60 mmol/L, and they were referred for sweat chloride measurements. Associations between sweat conductivity measurements and age, gender, (pH, HCO₃, pCO₂, Na, K, Cl), family history, consanguinity, indications for the test and number of hospitalization were studied.

Results

Among 2,664 patients, 16 children had sweat conductivity values higher than 80. The median age of patients diagnosed with CF was 4 months old. Age, pH, HCO₃, Na, Cl, K and the sweat conductivity test were statistically related (P < 0.001). The ROC curve showed very high agreement between the 2nd conductivity test and the sweat test.

Conclusions

Patients suspected to have CF can be screened using the Nanoduct^® conductivity device in non-qualified centers.

Prevalence of hyponatremia at diagnosis and factors associated with the longitudinal variation in serum sodium levels in infants with cystic fibrosis

OBJECTIVE

To determine the prevalence of hyponatremia at diagnosis in patients with cystic fibrosis and identify the factors associated with changes in serum sodium concentration over time.

STUDY DESIGN

This longitudinal study investigated whether variations in serum sodium concentration were associated with age, diet, infection status, and climate/temperature. Multivariate analysis was performed using the random-effects model for longitudinal data.

RESULTS

Hyponatremia at diagnosis was observed in 19 of the 20 patients (95%). Factors identified as associated with variations in serum sodium concentration were diet (P = .008) and climate/temperature (P = .005). Intake of solid foods appeared to greatly increase the serum sodium concentration (increase of 5 mEq/L after introduction of solid foods); however, a confounding factor between diet and age cannot be definitively ruled out. Climate/temperature contributed in an inverse way; a 1°C-increase in ambient temperature was associated with a 0.5-mEq/L decrease in serum sodium concentration.

CONCLUSION

Infants with cystic fibrosis who feed on breast milk or formula and live in a high-temperature environment are at increased risk for hyponatremia, even when receiving a higher salt intake in accordance with recommendations.

CFTR and defective endocytosis: new insights in the renal phenotype of cystic fibrosis

Inactivation of the chloride channel cystic fibrosis transmembrane conductance regulator (CFTR) causes cystic fibrosis (CF). Although CFTR is expressed in the kidney, no overwhelming renal phenotype is associated with CF. Recent studies have shown that the level of CFTR mRNA in mouse kidney approaches that found in lung. CFTR is particularly abundant in the apical area of proximal tubule cells, where it co-distributes with the Cl(-)/H(+) exchanger ClC-5 and Rab5a in endosomes. The biological relevance of CFTR in proximal tubule endocytosis has been tested in CF mouse models and CF patients. Mice lacking CFTR show a defective receptor-mediated endocytosis, as evidenced by impaired uptake of (125)I-beta(2)-microglobulin, a decreased expression of the cubilin receptor in the kidney, and a significant excretion of cubilin and its low-molecular-weight ligands into the urine. Low-molecular-weight proteinuria (and particularly transferrinuria) is similarly detected in CF patients in comparison with normal controls or patients with chronic lung inflammation. These studies suggest that the functional loss of CFTR impairs the handling of low-molecular-weight proteins by the kidney, supporting a role of CFTR in receptor-mediated endocytosis in proximal tubule cells. The selective proteinuria should be integrated in the pathophysiology of multi-systemic complications increasingly observed in CF patients.

Hyponatremic dehydration as a presentation of cystic fibrosis

BACKGROUND

The purpose of this study is to present a case report of a child with hyponatremic dehydration diagnosed after CF and to review the cases of 13 patients with CF who had the same initial presentation in our hospital.

METHODS

This report reviewed the clinical records of children diagnosed with CF to ascertain the prevalence of metabolic alkalosis with electrolyte depletion as the presentation of CF. It also used sweat tests to diagnose a child with CF.

RESULTS

The laboratory tests of a 12-month-old girl presented 3 times to the ;pediatric emergency department with vomiting and weight loss showed hyponatremia, hypochloremia, and metabolic alkalosis. The patient was subsequently diagnosed with CF by means of 2 positive sweat tests. Meanwhile, the review of the clinical records of all children diagnosed with CF from 1985 to 2004 (N = 77) showed that the prevalence of metabolic alkalosis with electrolyte depletion as the presentation of CF was 16.8%. The age of the infants ranged from 3 to 14 months. All episodes took place during summer.

CONCLUSIONS

There are not many causes of metabolic alkalosis with hyponatremic dehydration, and one of them is CF. This report emphasizes sodium depletion as a common sign of CF presentation. This is most important in countries where the neonatal screening test for CF is not available because the disease may be asymptomatic or oligosymptomatic for several months or even years. Cystic fibrosis should be considered in differential diagnosis of any child presenting with unexplained hyponatremic dehydration.

Inherited Renal Tubulopathies Associated With Metabolic Alkalosis: Effects on Blood Pressure

Inherited tubular disorders associated with metabolic alkalosis are caused by several gene mutations encoding different tubular transporters responsible for NaCl renal handling. Body volume and renin-angiotensin-aldosterone system status are determined by NaCl reabsorption in the distal nephron. Two common hallmarks in affected individuals: hypokalemia and normal / high blood pressure, support the differential diagnosis. Bartter's syndrome, characterized by hypokalemia and normal blood pressure, is a heterogenic disease caused by the loss of function of SLC12A1 (type 1), KCNJ1 (type 2), CLCNKB (type 3), or BSND genes (type 4). As a result, patients present with renal salt wasting and hypercalciuria. Gitelman's syndrome is caused by the loss of funcion of the SLC12A3 gene and may resemble Bartter's syndrome, though is associated with the very low urinary calcium. Liddle's syndrome, also with similar phenotype but with hypertension, is produced by the gain of function of the SNCC1B or SNCC1G genes, and must be distinguished from other entities of inherited hypertension such as Apparently Mineralocorticoid Excess, of glucocorticoid remediable hypertension.

Clinical features and treatment approaches in cystic fibrosis with pseudo-Bartter syndrome

INTRODUCTION

Infants with cystic fibrosis (CF) are prone to develop episodes of hyponatraemic, hypochloraemic dehydration with metabolic alkalosis, which are biochemical hallmarks of the pseudo-Bartter syndrome (PB).

METHOD

We reviewed the clinical and laboratory features and treatment approaches of 29 children with CF and PB who were under follow-up in our institution from May 1992 to November 2003.

RESULTS

Of 241 patients with CF, PB was detected in 29 (12%) with a median age of 4 months at the time of the first attack. Most patients experienced vomiting, loss of appetite and dehydration during episodes of PB. All patients were managed with intravenous fluids and sodium chloride solutions. During follow-up, 12/29 cases required hospital admission for recurrent PB attacks. The oldest age at the time of the last attack was 48 months.

CONCLUSIONS

CF should be considered in the differential diagnosis of metabolic alkalosis in young children. Vomiting and loss of appetite are important warning signs of possible PB in CF patients, particularly before 4 years of age. To prevent serious complications, it is crucial that parents and physicians recognise PB as early as possible.

An unusual presentation of cystic fibrosis in an adult

The diagnosis of cystic fibrosis (CF) generally is made within the first few years of life, although some cases will not be diagnosed until adulthood. For most patients the diagnosis is suggested by typical CF-related symptoms such as chronic respiratory infection or maldigestion. The authors describe an adult patient with newly diagnosed CF whose presenting abnormalities consisted of hypokalemia and metabolic alkalosis. These are known complications of CF but are not common presenting features that lead to the diagnosis of CF. The authors discuss their patient's presentation and review his metabolic manifestations of CF.

Cystic fibrosis presenting as metabolic alkalosis in a boy with the rare D579G mutation

We report on a 10-month-old boy with hypotonic dehydration and metabolic alkalosis. Sweat test was borderline and genetic analysis was negative for common mutations. Analysis of the whole coding regions of the CFTR gene revealed the rare mutation D579G in homozygosity.

Dehydration deaths in infants and young children

Dehydration in developed countries is an uncommon but important mechanism resulting in the death of infants and children. The clinicopathological features of a series of 37 fatal dehydration cases autopsied at the Adelaide Children's Hospital over a 33-year period (1961-1993) are presented. Causative factors for dehydration included gastroenteritis (21 cases), gastroenteritis with high environmental temperature (one case), high environmental temperatures (six cases), neglect/failure to thrive (four cases), mental retardation/chromosomal abnormality (three cases), congenital adrenal hyperplasia (one case), and unsuspected cystic fibrosis (one case). The mean age at death was 11.4 months (range 2 weeks to 6.25 years; median 6 months; 95% confidence interval 6 months to 1 year and 4 months; male-to-female ratio, 19:18). Sixteen of the 22 cases of fatal gastroenteritis (73%) occurred during the fall/winter months (March to August). There were a total of seven aboriginal or part aboriginal children in the group (19%). Children with mental retardation were at higher risk of dehydration, and previously unsuspected cases of child abuse/neglect also presented with lethal dehydration. Vitreous humor electrolyte levels and immunoassay for rotavirus were useful diagnostic adjuncts.

Urinary chloride excretion distinguishes between renal and extrarenal metabolic alkalosis

The aetiology of normotensive hypokalaemic metabolic alkalosis is sometimes not obtainable from the history. Observations in adults indicate that the urinary chloride excretion is low in metabolic alkalosis of extrarenal origin. The chloride/creatinine ratio in random urines was therefore compared in 283 healthy children and in eight paediatric patients with metabolic alkalosis. The urinary chloride/creatinine ratio was reduced in four patients with metabolic alkalosis of extrarenal origin and within reference values or above in four patients with metabolic alkalosis of renal origin.

CONCLUSION

The study confirms that urinary chloride/creatinine ratio discriminates between extrarenal and renal forms of metabolic alkalosis.

Potassium homeostasis and its disturbances in children

Although only 2% of the body potassium is present in the extracellular space, its concentration is finely regulated by the internal balance, or distribution of potassium between the intracellular and extracellular compartments, and by the external balance, or difference between intake and output of potassium. Internal balance is modulated by a host of factors, including insulin, epinephrine, extracellular pH and plasma tonicity. Potassium output from the body is mainly determined by renal excretion. Renal secretion of potassium takes place predominantly in the principal cells of late distal and cortical collecting tubules, by a process involving the accumulation of potassium in the cell by the activity of the basolateral Na+,K(+)-ATPase and its exit through luminal conductive channels. The factors regulating renal potassium secretion are potassium intake, rate of tubular fluid flow, distal sodium delivery, acid-base status and aldosterone. Hypokalaemia may result from a low potassium intake, excessive gastrointestinal, cutaneous or renal losses and altered body distribution. Aetiological diagnosis and therapy are best accomplished when the acid-base status is assessed at the same time. Before establishing the diagnosis of hyperkalaemia, spurious hyperkalaemia due to haemolysis or release of potassium from cells during clot retraction (pseudohyperkalaemia) should be ruled out. Hyperkalaemia may result from exogenous or endogenous loading, decreased renal output and altered body distribution. Acute hyperkalaemia represents an emergency situation which requires immediate therapy.