Hyperuricemia as a clue for central diabetes insipidus (lack of V1 effect) in the differential diagnosis of polydipsia

The Urine Calcium/Creatinine Ratio and Uricemia during Hyponatremia of Different Origins: Clinical Implications

Background: Chronic hyponatremia is known to be associated with osteoporosis. It has been shown that chronic hyponatremia increases bone resorption in an attempt to release body stores of exchangeable sodium by different mechanisms. We wanted to know the calciuria of patients with hyponatremia of different origins. Material and Methods: We made a retrospective study of 114 consecutive patients with asymptomatic hyponatremia of different origins with the usual serum and urine chemistry. Result: In hyponatremia due to SIADH, we had a high urine calcium/creatinine ratio of 0.23 ± 0.096 while in patients with salt depletion the UCa/UCr ratio was low (0.056 ± 0.038), in patients with hyponatremia secondary to thiazide intake the value was also low (0.075 ± 0.047) as in hypervolemic patients (0.034 ± 0.01). In hyponatremia due to polydipsia, the value was high (0.205 ± 0.10). Correction of hyponatremia in the euvolemic patients was associated with a significant decrease in the UCa/UCr ratio. In patients with hyponatremia secondary to thiazide intake, we noted that in the patients with low uric acid levels (<4 mg/dL, suggesting euvolemia) we also observed a low UCa/UCr (<0.10). In nine patients with chronic SIADH (SNa 125.1 ± 3.6 mEq/L), the 24 h urine calcium excretion was 275 ± 112 mg and decreased to 122 ± 77 mg (p < 0.01) after at least 2 weeks of treatment. Conclusions: Patients with chronic hyponatremia due to SIADH usually have a high UCa/UCr ratio (>0.15). This is also observed in hyponatremia secondary to polydipsia. Patients with thiazide-induced hyponatremia usually have low UCa/UCr levels and this is the case even among those with a biochemistry similar to that in SIADH (uric acid < 4 mg/dL).

Diagnosis and management of diabetes insipidus for the internist: an update

Diabetes insipidus is a disorder characterized by excretion of large amounts of hypotonic urine. Four entities have to be differentiated: central diabetes insipidus resulting from a deficiency of the hormone arginine vasopressin (AVP) in the pituitary gland or the hypothalamus, nephrogenic diabetes insipidus resulting from resistance to AVP in the kidneys, gestational diabetes insipidus resulting from an increase in placental vasopressinase and finally primary polydipsia, which involves excessive intake of large amounts of water despite normal AVP secretion and action. Distinguishing between the different types of diabetes insipidus can be challenging. A detailed medical history, physical examination and imaging studies are needed to detect the aetiology of diabetes insipidus. Differentiation between the various forms of hypotonic polyuria is then done by the classical water deprivation test or the more recently developed hypertonic saline or arginine stimulation together with copeptin (or AVP) measurement. In patients with idiopathic central DI, a close follow-up is needed since central DI can be the first sign of an underlying pathology. Treatment of diabetes insipidus or primary polydipsia depends on the underlying aetiology and differs in central diabetes insipidus, nephrogenic diabetes insipidus and primary polydipsia. This review will discuss issues and newest developments in diagnosis, differential diagnosis and treatment, with a focus on central diabetes insipidus.

Longitudinal study of kidney water management in patients diagnosed with idiopathic hypercalciuria in childhood

INTRODUCTION

There is much debate about whether idiopathic hypercalciuria (IH) affects kidney water management. For the first time in the literature, we carried out a longitudinal study of kidney water management (KWM) in patients diagnosed with IH in childhood and followed-up until adulthood (mean follow-up 17.7±1.4 years).

METHODS

Twenty-nine patients (7 M, 22 F) over the age of 24 years (mean 28.2±2.9 years, range: 24.1-35.9) who were diagnosed with IH in childhood (mean 7.6±3.2 years, range: 1-14) were included. Maximum urine osmolality (UO) and/or urine volume adjusted for 100ml of glomerular filtration rate (V/GFR) in both age groups (paediatric and adult) were determined. Moreover, whenever possible, in both age groups plasma creatinine levels, plasma sodium levels, uric acid levels, the citrate/creatinine ratio and the calcium/citrate ratio were recorded and a renal and bladder ultrasound was performed.

RESULTS

In the paediatric age group, KWM was altered in 9/29 cases (31%) (4 with reduced maximum UO and 5 with elevated V/GFR). In adulthood, KWM was found to be affected in 7/29 cases (24.1%) (6 with reduced UO and one with elevated V/GFR). Compared to the paediatric age group, adult patients had lower V/GFR, calcium/creatinine and citrate/creatinine values, as well as higher plasma creatinine, uric acid and calcium/citrate. There were no differences in the maximum UO in both age groups. However, UO in adulthood was significantly lower in subjects who had renal colic compared to those who did not (P=.04).

CONCLUSIONS

KWM was affected in approximately one third of patients with IH, which persisted 20 years after diagnosis. We think that these results may be due to adherence to the recommended protective diet and to the pharmacological treatment administered at the diagnosis of IH during childhood.

Pink Urine Syndrome: A Combination of Insulin Resistance and Propofol

Pink urine syndrome is mostly seen in patients treated with propofol anesthesia. The pink color is attributed to the presence of large concentrations of uric acid (and pigment), which is excreted in large amounts when propofol is given. We describe a case of propofol-induced pink urine syndrome and perform a comprehensive, evidence-based review. We discuss prior case studies already published in the literature as we speculate on the pathophysiology and how it translates to a clinically relevant entity.

Juvenile-onset gout and adipsic diabetes insipidus: A case report and literature review

The prevalence of juvenile-onset gout has been increasing. Hereditary factors and secondary diseases should be considered in these patients. Adipsic diabetes insipidus (ADI) is characterized by arginine vasopressin (AVP) deficiency, which results in hypotonic polyuria, and dysfunction of thirst osmoreceptors, which results in failure to generate a thirst sensation in response to hypernatremia. We herein report a case of a boy with gouty arthritis, refractory hyperuricemia, prominent hypernatremia, a high creatinine concentration, and a history of surgery for a hypothalamic hamartoma. The patient was diagnosed with central diabetes insipidus after endocrine evaluation. Because he never had symptoms of thirst, the final diagnosis was corrected to ADI. This is the first report of gout due to chronic ADI in an adolescent. Volume contraction due to ADI might be one cause of hyperuricemia and renal impairment in such patients. Moreover, AVP deficiency might directly lead to low urate clearance due to the lack of vasopressin receptor 1 stimulation. Lack of polydipsia and polyuria may delay the diagnosis of ADI and lead to severe complications of a chronic hyperosmolar status. Sufficient and effective establishment of normovolemia is critical for these patients.

Effect of sauna bathing and beer ingestion on plasma concentrations of purine bases

To determine whether sauna bathing alone or in combination with beer ingestion increases the plasma concentration of uric acid, 5 healthy subjects were tested. Urine and plasma measurements were performed before and after each took a sauna bath, ingested beer, and ingested beer just after taking a sauna bath, with a 2-week interval between each activity. Sauna bathing alone increased the plasma concentrations of uric acid and oxypurines (hypoxanthine and xanthine), and decreased the urinary and fractional excretion of uric acid, while beer ingestion alone increased the plasma concentrations and urinary excretion of uric acid and oxypurines. A combination of both increased the plasma concentration of uric acid and oxypurines, and decreased the urinary and fractional excretion of uric acid, with an increase in the urinary excretion of oxypurines. The increase in plasma concentration of uric acid with the combination protocol was not synergistic as compared to the sum of the increases by each alone. Body weight, urine volume, and the urinary excretion of sodium and chloride via dehydration were decreased following sauna bathing alone. These results suggest that sauna bathing had a relationship with enhanced purine degradation and a decrease in the urinary excretion of uric acid, leading to an increase in the plasma concentration of uric acid. Further, we concluded that extracellular volume loss may affect the common renal transport pathway of uric acid and xanthine. Therefore, it is recommended that patients with gout refrain from drinking alcoholic beverages, including beer, after taking a sauna bath, since the increase in plasma concentration of uric acid following the combination of sauna bathing and beer ingestion was additive.

Difference in solute excretion during correction of hyponatremic patients with cirrhosis or syndrome of inappropriate secretion of antidiuretic hormone by oral vasopressin V2 receptor antagonist VPA-985

VPA-985 is an orally active, competitive vasopressin V(2) receptor antagonist that in normal human beings increases water excretion without affecting solute excretion. Whether solute excretion is affected in patients with hyponatremia resulting from inappropriate secretion of antidiuretic hormone (SIADH) or from cirrhosis treated with VPA-985 is unknown. Six hyponatremic patients with SIADH and 5 hyponatremic patients with cirrhosis with ascitis (CWAs) were treated with 50 or 100 mg VPA-985 twice daily. Evolution of creatinine, urea, uric acid, sodium, potassium, and osmotic clearance were determined. Volume hormones (plasma renin [PR], aldosterone, antidiuretic hormone [ADH], atrial natriuretic factor [ANF]) were also determined before and after treatment. In patients with SIADH, serum sodium concentration (SNa) was generally corrected in 1 day (SNa: 126 +/- 4.5 mmol/L at t = 0 hours and 133 +/- 5.6 mmol/L at t = 24 hours) and associated with a decrease in sodium excretion (from 82 +/- 22 mmol/24 hours to 45 +/- 21 mmol/24 hours; P < 0.05) without modification in potassium excretion. Despite an increase in diuresis (from 0.84 +/- 0.2 ml/min to 1.46 +/- 0.4 ml/min) urea and uric acid clearances decreased. Urine osmolality decreased from 414 +/- 148 mOsm/kg H(2)O to 209 +/- 55 mOsm/kg H(2)O. Volume hormones did not change. In the CWAs the rise of SNa was more progressive (SNa: 126 +/- 2.8 mmol/L at t = H0 to 133 +/- 4.9 mmol/L at t = 48 hours) and parallel to an augmentation in sodium excretion (from 23 +/- 18 mmol/24 hours to 65 6 60 mmol/24 hours the second day of VPA administration). The higher sodium excretion was also connected with a progression in potassium excretion (from 22 6 7 mmol/24 hours to 36 +/- 18 mmol/24 hours). The increase in diuresis under VPA from 0.42 +/- 0.2 mL/min to 1.7 +/- 0.9 mL/min resulted in a higher urea clearance. Urine osmolality decreased from 509 +/- 142 mOsm/kg H(2)O before VPA to 194 +/- 106 mOsm/kg H(2)O after VPA. ADH increased in CWAs treated with VPA, from 1.9 +/- 1.2 pg/mL to 5.3 +/- 2.8 pg/mL (P <.05) while other volume hormones did not change. VPA-985 is a highly effective drug in the short-term management of hyponatremic patients with SIADH or CWAs. SNa correction is associated with urinary sodium retention in SIADH, whereas in CWAs a mild increase in sodium excretion is observed.

Evidence that chronicity of hyponatremia contributes to the high urate clearance observed in the syndrome of inappropriate antidiuretic hormone secretion

The high fractional excretion (FE) of uric acid observed in hyponatremia associated with the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is commonly attributed to the volume-expanded state, although volume expansion in normonatremic volunteers is unable to increase urate clearance to a degree similar to that in SIADH. The goal of the present study is to analyze whether hyponatremia by itself could influence the FE of uric acid, as well as the effects of intravascular volume and glomerular filtration rate on FE of uric acid in SIADH. This study examines the effects of a 2-L infusion of isotonic saline over 24 hours on FE of uric acid in 9 normonatremic volunteers and 17 hyponatremic patients with SIADH. We also studied the FE of uric acid in 6 patients with SIADH with only mild water retention and the urate and creatinine clearances in 18 hyponatremic patients with SIADH before and after normalization of serum sodium levels by water restriction. When infusing 2 L of isotonic saline over 24 hours in healthy subjects, there was a decrease in plasma protein concentration of 8%, suggesting a similar degree of volume expansion than in patients with SIADH. The FE of uric acid did not increase to the same extent (9% +/- 1.5% versus 17% +/- 1.5%; P: < 0.01). Conversely, in 6 hyponatremic patients with mild water retention (1 L), the FE of uric acid was still high despite indirect signs of only a small increase in plasma volume. The mainstay of these observations is that chronicity of hyponatremia by itself could affect urate excretion. We also observed that in the patients with SIADH, high FE of uric acid inversely correlated with glomerular filtration rate (r = -0.66; P: < 0.01) only during the hyponatremic state. These data suggest that hyponatremia by itself, combined with mild volume expansion and glomerular filtration rate, has a role in the high FE of uric acid in the SIADH.