Reversible tubular dysfunction that mimicked Fanconi's syndrome in a patient with anorexia nervosa

[Quality management in weight restitution in Anorexia nervosa--pathophysiology, evidence-based practice and prevention of the refeeding syndrome]

During refeeding syndrome-a well-known and dreaded complication of weight-restauration in anorexia nervosa-a shift of electrolytes and fluid can occur in malnourished patients and might therefore lead to-potentially fatal-cardiovascular, respiratory and neurological symptoms. Causes of this are metabolic and hormonal changes during re-establishment of a carbohydrate-rich diet. This syndrome is most commonly associated with hypophosphatemia, which can however be accompanied by other chemical laboratory abnormalities. Standardized guidelines for the prevention and management of the refeeding syndrome have not yet been established. In case and cohort studies different low- and high-calorie diet protocols led to comparable results with similar complication rates. A focus should be placed on prevention of serious complications by careful monitoring. The pathophysiology, the main constituents in the development of the refeeding syndrome, recommendations for risk assessment and treatment, and current evidence are discussed.

To the limit of extreme malnutrition

Extreme malnutrition with body mass index (BMI) as low as 10 kg/m(2) is not uncommon in anorexia nervosa, with survival enabled through complex metabolic adaptations. In contrast, outcomes from hunger strikes and famines are usually fatal after weight loss to about 40% below expected body weight, corresponding to BMI 12 to 13 kg/m(2) in adults. Thus, many years of adaptation in adolescent-onset anorexia nervosa, supported by supplements of vitamins and treatment of intercurrent diseases, may allow survival at a much lower BMI. However, in the literature only a few cases of survival in patients with BMI <9 kg/m(2) have been described. We report on the case of a 29-y-old woman who was successfully treated in a specialized unit. She had a BMI of 7.8 kg/m(2). To our knowledge, this level of extreme malnutrition has not previously been reported. The present case emphasizes the importance of adherence to guidelines to decrease refeeding complications.

Transient renal dysfunction with reversible splenial lesion

We report the case of a 6-month-old boy with transient renal dysfunction who had an intensified signal in the splenium of the corpus callosum on magnetic resonance imaging. He presented to hospital with fever and sudden disturbance of consciousness. Cerebrospinal fluid analysis did not show pleocytosis. The mild consciousness disturbance disappeared after 30 min, but the splenial signal persisted even after 8 days. Further, renal glucosuria, increased excretion of select amino acids, and abnormal fractional excretion of electrolytes were observed, indicating renal tubular dysfunction. The abnormal urinary findings spontaneously resolved by day 9 of hospitalization. The splenial lesion took 21 days to normalize. There were no signs of neurological complications 2 months later. This case suggests the possibility of renal involvement in splenial lesions.

The clinical biochemistry of anorexia nervosa

In anorexia nervosa, under-nutrition and weight regulatory behaviours such as vomiting and laxative abuse can lead to a range of biochemical problems. Hypokalaemia is the most common electrolyte abnormality. Metabolic alkalosis occurs in patients who vomit or abuse diuretics and acidosis in those misusing laxatives. Hyponatraemia is often due to excessive water ingestion, but may also occur in chronic energy deprivation or diuretic misuse. Urea and creatinine are generally low and normal concentrations may mask dehydration or renal dysfunction. Abnormalities of liver enzymes are predominantly characterized by elevation of aminotransferases, which may occur before or during refeeding. The serum albumin is usually normal, even in severely malnourished patients. Amenorrhoea is due to hypogonadotrophic hypogonadism. Reduced concentrations of free T4 and free T3 are frequently reported and T4 is preferentially converted to reverse T3. Cortisol is elevated but the response to adrenocorticotrophic hormone is normal. Hypoglycaemia is common. Hypercholesterolaemia is a common finding but its significance for cardiovascular risk is uncertain. A number of micronutrient deficiencies can occur. Other abnormalities include hyperamylasaemia, hypercarotenaemia and elevated creatine kinase. There is an increased prevalence of eating disorders in type 1 diabetes and the intentional omission of insulin is associated with impaired metabolic control. Refeeding may produce electrolyte abnormalities, hyper- and hypoglycaemia, acute thiamin depletion and fluid balance disturbance; careful biochemical monitoring and thiamin replacement are therefore essential during refeeding. Future research should address the management of electrolyte problems, the role of leptin and micronutrients, and the possible use of biochemical markers in risk stratification.

Hypouricemia in individuals admitted to an inpatient hospital-based facility

BACKGROUND

Decreased serum uric acid levels resulting from renal urate wasting occasionally are reported in hospitalized patients because of isolated or generalized proximal tubular damage. There are limited recent findings with regard to the incidence and cause of hypouricemia in patients admitted to an internal medicine clinic. The aim of this study is to examine the prevalence of hypouricemia in individuals admitted to our inpatient hospital-based facility and identify underlying causes and pathogenetic mechanisms and any association of hypouricemia and uricosuria with other tubular defects.

METHODS

A total of 7,250 serum urate measurements were available on patients' admission. Hypouricemia is defined as a serum urate level less than 2.5 mg/dL (149 micromo/L). In all hypouricemic cases, a detailed clinical and laboratory investigation was performed.

RESULTS

Hypouricemia was found in 90 patients (1.24%). In all except one patient, hypouricemia was associated with inappropriate uricosuria (urate fractional excretion [FE] > 10%; range, 10.8% to 94%). There was an inverse correlation between serum uric acid level and its FE (r = -0.73; P < 0.0001). The most common causes of hypouricemia were obstructive jaundice of any cause (n = 18), solid or hematologic neoplasias (n = 17), diabetes mellitus (n = 12), drugs affecting urate homeostasis (n = 10), and intracranial diseases (n = 8). Seventeen patients with hypouricemia showed one or more other manifestations of proximal tubular damage, such as glucosuria, inappropriate phosphaturia leading to hypophosphatemia, and kaliuria resulting in hypokalemia.

CONCLUSION

Hypouricemia caused by inappropriate uricosuria is not rare in patients admitted to an internal medicine clinic, is related to underlying diseases, and may be associated with other abnormalities of proximal tubular function.