Renal Tubular Defect Research Articles

Renal Function in Adult Beta-Thalassemia/Hb E Disease

β-Thalassemia hemoglobin E (β-thal/Hb E) is the commonest form of hemoglobinopathy in Thailand. Shortened red cell life span, rapid iron turnover and tissue deposition of excess iron are major factors responsible for functional and physiological abnormalities found in various forms of thalassemia. Increased deposition of iron had been found in renal parenchyma of thalassemic patients, but no systematic study of the effect of the deposits on renal functions has been available. The purpose of this study is to describe the functional abnormalities of the kidney in patients with β-thal/Hb E and provide evidence that increased oxidative stress might be one of the factors responsible for the damage. Urine and serum samples from 95 patients with β-thal/Hb E were studied comparing with 27 age-matched healthy controls. No difference in the creatinine clearance was observed. β-thal/Hb E patients excreted significantly more urinary protein (0.8 ± 0.5 vs. 0.3±0.1 g/day, p < 0.001). Aminoaciduria was found in 16% of the patients. Analysis of urinary protein by SDS-PAGE electrophoresis and silver staining revealed abnormal pattern of protein with increased small molecular weight (<45 kD) bands. Morning urine analysis showed significant lower urine osmolality (578.3 ± 164.6 vs. 762.4 ± 169.9 mosm/kg, p < 0.001) in patients. Patients excreted more NAG (N-acetyl beta-D-glucosaminidase, 26.3 ± 41.3 vs. 8.4 ± 3.9 U/g Cr, p < 0.0001) and β₂-microglobulin, 124.3 ± 167 vs. 71 ± 65.5 µg/g Cr, p = 0.001. Plasma and urine MDA (malonyldialdehyde) levels were both raised (p < 0.0001). Nine patients were selected for renal acidification study. All were found to be normal, but showed poor response to DDAVP challenge (urine osmolality 533 ± 71). This is the first report of renal tubular defects found associated with β-thal/Hb E disease. The mechanism leading to the damage is not known but it might be related to increased oxidative stress secondary to tissue deposition of iron, as indicated by the raised levels of serum and urine MDA. It is not known whether these functional defects would have any long-term effects on the patients. Further studies are warranted and means of prevention of these defects should urgently be sought.

OSTEOPETROSIS IN CHILDREN

SUMMARYOver a 10‐year period, 28 Arab children with autosomal recessive osteopetrosis were seen in two hospitals in Riyadh, Saudi Arabia. Eighteen (64%) had osteopetrosis associated with metabolic acidosis probably due to a renal tubular defect; nine (32%) had a malignant infantile form of osteopetrosis and one had a mild form with delayed onset. Parental consanguinity was 56% and 40% among patients with and without acidosis respectively. Somatic and psychomotor retardation and recurrent bone fractures were common in both groups. Dental caries, cerebral calcification and optic atrophy were more frequent in patients with acidosis, while anaemia, hepatosplenomegaly and deafness were more common in patients without acidosis. To guarantee optimal rehabilitation, children with this progressive disease require an early multiteam approach.

Renal tubular disorders

Abstract Renal tubular disorders in childhood are rare, but, when present, may produce profound electrolyte and volume disturbances. Children with hereditary tubular dysfunction commonly present in the first year of life with failure to thrive and other non-specific symptoms. Biochemical analysis of both serum and urine, together with clinical history and examination, remain fundamental for their diagnosis, whilst localization of the renal tubular defect to the proximal or distal nephron is necessary for understanding of the underlying pathophysiology and appropriate management. During recent years, important new information concerning diagnosis and treatment of selective tubular disorders has been acquired.

The nephropathy of type I tyrosinemia after liver transplantation

ABSTRACT: Type I tyrosinemia (HTI) is an autosomally recessively inherited disease caused by deficiency of fumarylacetoacetate hydrolase. The disease manifests with liver failure, renal tubular defects, and neurologic crises. Currently orthotopic liver transplantation (OLT) enables patients to survive. However, renal fumarylacetoacetate hydrolase deficiency is not corrected by OLT, and the long-term prognosis of the nephropathy is not known. We investigated tyrosine metabolism, GFR, renal tubular function, and histopathology before and 18-36 mo after OLT in eight patients with HTI. Progressive renal dysfunction was not documented despite continuing, although diminished, urinary succinylacetone excretion in all patients. The mean GFR was 82 mL/min/1.73 m2 before and 102 mL at 18 mo and 93 mL at 36 mo after OLT. All patients showed tubular dysfunction before OLT. At 18 mo, glucosuria occurred in one, amino aciduria and phosphaturia in three, and hypercalciuria in six patients. Only hypercalciuria was seen at 36 mo. Renal biopsies showed mild nonspecific changes caused either by minimal progression of the renal disease or by mild cyclosporine nephrotoxicity. In conclusion, patients with HTI had normal GFR, but showed signs of tubular dysfunction 18–36 mo after OLT. Renal function and histopathology should be monitored after OLT for HTI.

Liddle's syndrome, an underrecognized entity: A report of four cases, including the first report in black individuals

Liddle's syndrome, a rare cause of hypokalemic hypertension, is characterized by a renal tubular sodium channel defect resulting in excessive sodium absorption and concomitant potassium wasting. In this disorder, although the clinical manifestations resemble primary aldosteronism, serum and urine aldosterone are suppressed. The syndrome is transmitted in an autosomal dominant pattern. It has been reported previously in white and oriental populations but not in the black individuals. We identified four patients (two of whom are black) in our nephrology clinic, with severe hypokalemic hypertension not correctly diagnosed for several years. All patients underwent an extensive work-up for secondary hypertension because of persistent severe hypertension (average blood pressure, 210 130 mm Hg) despite high-dose multi-drug therapy. Primary aldosteronism was excluded because of low serum aldosterone. Cushing's syndrome, pheochromocytoma, renal artery stenosis, and enzymatic deficiencies of cortisol synthesis (11β-hydroxylase, 17α-hydroxylase, 5β-reductase, and 11β-hydroxysteroid dehydrogenase) were ruled out with extensive endocrine and radiologic studies. Once the diagnosis of Liddle's syndrome was suspected, all patients were treated with either triamterene or ameloride, with resolution of hypokalemia and correction of hypertension occurring within 5 to 7 days. Our findings suggest that Liddle's syndrome can occur in the black population. Although the actual incidence of this syndrome remains unknown, it may be significantly more common than we are led to believe since it is inherited in a Mendelian pattern. Whether there is a subset of low-renin, salt-sensitive black hypertensive patients who have the same or similar sodium channel defect remains to be elucidated.

The nephropathy of type I tyrosinemia after liver transplantation.

Type I tyrosinemia (HTI) is an autosomally recessively inherited disease caused by deficiency of fumarylacetoacetate hydrolase. The disease manifests with liver failure, renal tubular defects, and neurologic crises. Currently orthotopic liver transplantation (OLT) enables patients to survive. However, renal fumarylacetoacetate hydrolase deficiency is not corrected by OLT, and the long-term prognosis of the nephropathy is not known. We investigated tyrosine metabolism, GFR, renal tubular function, and histopathology before and 18-36 mo after OLT in eight patients with HTI. Progressive renal dysfunction was not documented despite continuing, although diminished, urinary succinylacetone excretion in all patients. The mean GFR was 82 mL/min/1.73 m2 before and 102 mL at 18 mo and 93 mL at 36 mo after OLT. All patients showed tubular dysfunction before OLT. At 18 mo, glucosuria occurred in one, amino aciduria and phosphaturia in three, and hypercalciuria in six patients. Only hypercalciuria was seen at 36 mo. Renal biopsies showed mild nonspecific changes caused either by minimal progression of the renal disease or by mild cyclosporine nephrotoxicity. In conclusion, patients with HTI had normal GFR, but showed signs of tubular dysfunction 18-36 mo after OLT. Renal function and histopathology should be monitored after OLT for HTI.

Severe Renal Hypouricemia Secondary to Hyperbilirubinemia

A 64-year-old man with alcoholic liver cirrhosis had a progressive decrease in the serum uric acid (UA) until it became undetectable, an increase renal UA clearance, mild glycosuria with normal serum glucose and a decrease in the tubular reabsorption of phosphate in association with cholestasis secondary to a gallbladder carcinoma. All these abnormalities returned to normal when the serum bilirubin levels decreased following surgical treatment. This clinical observation suggests that the reversible renal tubular transport defect was secondary to high levels of serum bilirubin.

Ifosfamide‐induced renal tubular defect

We describe 2 cases of proximal tubular defects induced by the administration of ifosfamide at a dosage of 6 g/m2/course over 2 days in children with a diagnosis of malignant mesenchymal tumors. This adverse effect could be minimized dividing dosage of the drug. However at present it is not clear if divided doses are completely safe.

The Frusemide Test: Simple Screening Test for Renal Acidification Defect in Urolithiasis

Urinary pH was first labelled as a risk factor for patients with recurrent calcium stone disease of the renal tract in 1978. The standard diagnostic test for patients with a history of stones, who appear to have urinary acidification defects is the ammonium chloride test. However, the performance of this test results in significant morbidity, particularly nausea and vomiting, and as a result there is little enthusiasm for screening for such defects. We describe a screening test that may be used to determine which patients require more definitive testing. It involves an oral dose of frusemide (40 mg) followed by half-hourly urine sampling for pH. For the detection of a renal tubular acidification defect, the frusemide test had sensitivity = 100%, specificity = 82%, predictive value of a positive result = 40%, predictive value of a negative result = 100%, screening efficiency = 84%, and there was no morbidity. During the ammonium chloride test 80% of the patients vomited or felt very nauseated.

Nephrolithiasis, hypocitraturia, and a distal renal tubular acidification defect in type 1 glycogen storage disease

Renal stones containing calcium can occur in patients with type 1 glycogen storage disease. We studied 11 patients with glycogen storage disease. Five patients had renal calculi, nephrocalcinosis, or both, and five had hypercalciuria. Serum levels of calcium, phosphorus, parathyroid hormone, and urate were normal. Serum levels of 1,25-dihydroxyvitamin D were elevated in each patient. None of the patients had a metabolic acidosis, but all nine who were tested had evidence of impaired acid excretion. In response to an acid load, eight of the nine patients had subnormal titratable acid excretion, and nine had subnormal ammonia excretion; six of nine patients were unable to secrete hydrogen ions in response to bicarbonate administration. These data indicate that patients with type 1 glycogen storage disease have an incomplete form of distal renal tubular acidosis. This may be the cause of hypercalciuria and nephrocalcinosis in these patients.

Hypercalciuria in children with renal glycosuria: Evidence of dual renal tubular reabsorptive defects

During the past 5 years, we have identified idiopathic hypercalciuria in five of seven patients referred for evaluation of renal glycosuria between 1985 and 1991. The children, all boys, ranged in age from 6 to 12 years. Endocrine function was normal, and none of the patients had hyperparathyroidism, hypercalcemia, renal tubular acidosis, or other secondary causes of hypercalciuria. The calcium/creatinine ratio in a fasting urine specimen was elevated in all five children who had hypercalciuria, with a mean value (+/- SD) of 0.34 +/- 0.06 (normal, < 0.2). In one child who had renal colic with spontaneous passage of gravel-like material, the idiopathic hypercalciuria persisted after 1 week on a diet containing 2000 mg of sodium and 300 mg of calcium. On the basis of studies that examined the site along the nephron responsible for hypercalciuria in rats with streptozocin-induced diabetes, we speculate that in children with renal glycosuria, there is defective reabsorption of glucose and calcium in the straight portion of the proximal tubule or in the collecting duct. It is likely that a similar mechanism accounts for the idiopathic hypercalciuria in children with diabetes mellitus.

Renal tubular acidosis in primary Sjögren's syndrome

Renal tubular acidosis (RTA) is a frequent extraglandular manifestation of Sjögren's syndrome; however, no distinction on the incidence of this renal tubular defect between primary and secondary Sjögren's syndrome has been reported. This study was undertaken in order to define the frequency of RTA and the possible pathogenetic mechanisms in a group of 21 randomly selected primary Sjögren's syndrome patients. RTA was found in 7 (33%) patients. The incomplete type of the disorder was the most frequent. It seems that the etiology of RTA is multifactorial. Renal excretion of monoclonal proteins and the immunologically-induced interstitial inflammation are the main possible factors of this renal tubular defect.

Elemental mercury vapour toxicity, treatment, and prognosis after acute, intensive exposure in chloralkali plant workers. Part II: Hyperchloraemia and genitourinary symptoms.

Exposure to elemental mercury vapour is known to influence renal function; however, severe renal disease has not been consistently identified. Eleven men were evaluated for renal disease after acute, massive mercury poisoning. Significant hyperchloraemia was identified in this group of patient and a reversible renal tubular defect was suggested by low normal serum bicarbonate, a normal serum anion gap and a positive urinary anion gap. The only other evidence of renal dysfunction was transient, mild proteinuria in one of the 11 patients. During this same time period, neuropsychological impairment was identified on a test of cognitive and visual-motor function, 'Trailmaking B', in seven of the 11 patients. Additionally, dysuria and ejaculatory pain occurred without evidence of urological disease. These complaints were more frequent in those patients with impairment on 'Trailmaking B' suggesting a neurological basis for these symptoms. The findings of this study support earlier observations that the brain rather than the kidney is the critical target organ after elemental mercury vapour exposure.

Cholangiocarcinoma and Severe Renal Hypouricemia: A Study of the Renal Mechanisms

Hypouricemia in malignant neoplasms is rarely reported. We present a previously unreported case of cholangiocarcinoma associated with severe persistent hypouricemia (serum uric acid levels ranged from 0.07 to 0.08 mmol/L [1.16 to 1.40 mg/100 mL], and increased urate clearance (50.90 to 57.33 mL/min v a mean value in 20 normal subjects of 9.75 +/- 1.65 mL/min). High fractional urate clearance (Cus/Ccr = 0.50 to 0.58 v 0.09 +/- 0.01 in normals) was suppressed only slightly following pyrazinamide (PZA), to 0.29 versus 0.007, and was surprisingly enhanced by probenecid (PB) to 1.78 versus 0.63 in normals. No other renal tubular or metabolic abnormalities were detected. This previously unreported association of a high PZA-nonsuppressible urate excretion with a postprobenecid urate clearance exceeding glomerular filtration rate suggests that a combined renal tubular defect is responsible for hypouricemia. The patient described here provides evidence to support the presence of a presecretory reabsorptive defect in association with a "relatively high" urate secretion by the renal tubule. This report adds to the list of hypouricemic conditions and presents an important clue to elucidate urate handling mechanisms in man.

Tyrosinaemia type I — an update

Tyrosinaemia type I is a recessively inherited disorder caused by a deficiency of fumarylacetoacetase (FAH), the last enzyme in tyrosine degradation. The presumed toxic agents are fumaryl- and maleylacetoacetate which are converted to succinylacetone (SA), a metabolite found in increased amounts in urine and plasma of the patients. The major clinical features are progressive liver damage and renal tubular defects with hypophosphataemic rickets. Renal tubular dysfunctions with secondary rickets may be lacking altogether, even in chronic patients. Hepatocellular carcinoma is a major cause of death in the chronic form. Diagnosis of the disorder is made by assay of SA in urine and serum and by determination of FAH in lymphocytes or fibroblasts. Prenatal diagnosis is performed by SA assay in amniotic fluid supernatant and FAH analysis in cultured amniotic fluid cells or chorionic villus material. Presence of a 'pseudodeficiency' gene for FAH prevents prenatal diagnosis by enzyme analysis in some families, and this gene also precludes identification of heterozygotes outside tyrosinaemia families. Immunoblot analyses show that acute patients and some chronic patients lack immunoreactive FAH protein. cDNA probes for FAH have been developed and several polymorphisms related to the FAH gene have been reported, which may allow prenatal diagnosis in families with complex genotypes. The gene for FAH has been mapped to chromosome 15 q23-q25. Liver transplantation is the ultimate treatment; most patients continue to excrete SA in urine after liver transplantation and therefore there is a possibility of kidney disease after transplantation.

Increased Chloride Reabsorption as an Inherited Renal Tubular Defect in Familial Type II Pseudohypoaldosteronism

HYPERKALEMIA is a common electrolyte disorder. Among its common causes are renal insufficiency; adrenal insufficiency; hyporeninemic hypoaldosteronism, usually associated with diabetes mellitus, mi...

Culture of renal tubular cells from the urine of patients with nephropathic cystinosis.

Nephropathic cystinosis represents a prototype for lysosomal storage diseases and is the most common cause of renal tubular Fanconi's syndrome. Mechanisms of the tubular transport defects in this disease have not been defined, however, in part because the cells readily cultured from affected patients, leukocytes and fibroblasts, do not express epithelial transport functions. Except for a single autopsy report, renal tubular cells from these patients have not been studied in vitro. In these studies, noninvasive harvesting and culture of renal tubular cells from the urine of patients with cystinosis is described. Cultures of renal tubular cells could be established from over 50% of the isolates which contained viable cells and which remained uncontaminated in vitro. Cells had an epithelial morphology in culture, and the majority of cultured cells expressed proximal tubular brush border marker enzyme. Cultured cells also expressed the storage defect in vitro, containing cystine levels up to 100 times those of normal cells. Cultured cells could be depleted of cystine by using the thiol cysteamine. This in vitro model system should be very useful for studying the mechanisms of renal tubular transport defects in this disease.

Hematin therapy for the neurologic crisis of tyrosinemia

Hereditary tyrosinemia (tyrosinemia type I) is an autosomal recessive disorder caused by a defect of the final enzyme in tyrosine metabolism. The disease is associated with renal tubular defects, acute and chronic liver failure, and hepatocellular carcinoma. An elevation in serum 6-aminolevulinic acid concentration is common and is due to competitive inhibition of ALA dehydrase by succinylacetone, a metabolite of tyrosine degradation. 1 A syndrome of acute neurologic crises, which has striking similarity to the acute porphyrias, is seen in as many as 40% of the children with this disorder. 2 As in the acute porphyrias, the episodes of acute neuropathy associated with tyrosinemia are best correlated with ALA excretion. 2 Hematin suppresses ALA synthase, the first committed step in heme synthesis. 3 Clinical studies in patients with porphyria have established the efficacy of hematin in decreasing ALA excretion and the improvement of clinical symptoms after intravenous administration. 4 The drug has few side effects and has been used without major complications in the treatment of numerous patients with acute porphyria. 4 We describe a case of severe neurologic crises associated with extremely high serum ALA levels in a child with tyrosinemia I. We elected to treat this patient with hematin, followed by liver transplantation. We believe this to be a rational course given the marked similarities of this disorder to the acute porphyrias.

Distal renal tubular acidosis: the value of urinary pH,PCO2 and NH4 + measurements

Distal renal tubular acidosis (dRTA) is not a single disease. The experimental forms of the syndrome are unsatisfactory as models of the naturally occurring disease, not least because they are seldom complicated by nephrocalcinosis, which is present in the majority of patients with spontaneous disease and contributes to the renal tubular defects found in the syndrome. Impairment of minimal urine pH, reduced urine carbon dioxide tension (PCO2) during passage of alkaline urine, and reduced urinary ammonium (NH4+) excretion, have all been advocated as essential criteria for the diagnosis of dRTA. Minimal urine pH, measured during metabolic acidosis, sulphate infusion, or after oral frusemide, is the yardstick against which other criteria should be assessed. A reduced urinary PCO2 is commonly found in dRTA but is not specific for the syndrome and may be accounted for by tubular defects other than those involving reduced distal hydrogen ion secretion. NH4+ excretion is reduced in most patients with renal acidosis whatever the nature of the underlying renal disease; this function is closely related to nephron mass, and is not specifically impaired in renal tubular disease.

The possible involvement of calcium in renal proximal tubular reabsorptive defect in the rat after release of ureteral obstruction

The temporal relationship between changes in cytosolic free calcium and proximal tubular function was examined in rats following 24 h of unilateral and bilateral ureteral obstruction. Immediately after release of unilateral ureteral obstruction, proximal tubular functions were found to be normal. Cytosolic free calcium in isolated proximal tubules of the ureteral obstructed and contralateral kidneys were 160 +/- 8 and 172 +/- 15 nM, respectively. On the 7th day after release, cytosolic free calcium was not different from the sham control value (135 +/- 6 vs. 149 +/- 7 nM). In contrast, immediately after release of bilateral ureteral obstruction, cytosolic free calcium was increased significantly to 219 +/- 6 from 139 +/- 9 nM in sham-operated controls. Subsequent declines in cytosolic free calcium to 196 +/- 15 and 148 +/- 7 nM were observed at 3 and 7 days after release of bilateral ureteral obstruction, respectively. Over this period, renal tubular functions gradually returned to normal. Changes in cytosolic free calcium correlate well with the reported improvement in renal tubular function after release of bilateral ureteral obstruction. Therefore, one possible mechanism for the impairment of tubular function observed in bilateral ureteral obstruction may be an increase in cytosolic free calcium.