Hypouricemia in acquired immunodeficiency syndrome

Clinical evaluations of hypouricemia in patients with the acquired immunodeficiency syndrome (AIDS) have shown that it is a common disorder resulting from defective renal handling of uric acid. We prospectively studied renal urate handling in 23 patients and reviewed the records of 73 consecutive patients with AIDS or AIDS-related complex (ARC), who were seen in our AIDS clinic between March 1985 and April 1988, to determine the incidence, significance, and, when possible, the cause of hypouricemia. Hypouricemia was defined as serum urate less than or equal to 0.18 mmol/L (3 mg/dL). Renal clearance studies were performed in 23 patients, 10 hypouricemic and 13 nonhypouricemic. Eight patients (six with hypouricemia) underwent central venous pressure (CVP) monitoring, which was performed for clinical signs and symptoms of extracellular volume depletion. Fourteen (eight with hypouricemia) had daily urine urate measured. Hypouricemia was found in 21 (21.9%) of 96 patients. It was more common in females and intravenous (IV) drug abusers, and was associated with more opportunistic illnesses, particularly mycobacterium avium intracellulare (MAI) and cytomegalovirus (CMV) infections. Hypouricemia occurred in three patients with ARC and 18 patients with AIDS and was associated with cerebral atrophy in all 12 hypouricemic and 14 of 28 nonhypouricemic patients who had cranial computed tomography (CT) scans. During a comparable follow-up period, 71.4% of the hypouricemic as compared with 38.7% of nonhypouricemic patients died. Eleven developed hypouricemia as outpatients. Fractional excretion of uric acid (FEua) was elevated in the eight patients with CVP less than 1 cm of water, and in 10 of 10 with and nine of 13 without hypouricemia, despite CVP less than 1 cm water in eight.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Serum ionized magnesium levels in type 2 diabetic patients with microalbuminuria or clinical proteinuria

BACKGROUND/AIMS: The association between microalbuminuria and magnesium depletion is a controversial issue, and serum ionized magnesium levels have not been previously studied in patients with different grades of diabetic nephropathy. Therefore, the aim of this study was to evaluate circulating ionized magnesium concentrations in patients with non-insulin-dependent diabetes mellitus (NIDDM) and incipient or overt diabetic nephropathy. METHODS: We measured fasting plasma glucose, creatinine, creatinine clearance estimate, total cholesterol and triglycerides, and serum ionized magnesium (ion-selective electrodes, ISE) in 30 NIDDM patients with urinary albumin excretion rate (UAER) <20 microg/min (normoalbuminuria), 30 NIDDM patients with microalbuminuria (20 < UAER < 200 microg/min), 30 NIDDM patients with clinical proteinuria (UAER >200 microg/min), and 20 healthy subjects. RESULTS: Serum ionized magnesium levels were significantly reduced in diabetic patients when compared to control subjects (0.39 +/- 0.06 vs. 0.58 +/- 0.05 mmol/l, p < 0.001). Moreover, diabetic patients with microalbuminuria or clinical proteinuria showed a significant decrease in serum ionized magnesium with respect to normoalbuminuria group (normoalbuminuria: 0.45 +/- 0. 02 mmol/l; microalbuminuria: 0.36 +/- 0.05 mmol/l, p < 0.001; clinical proteinuria: 0.35 +/- 0.04 mmol/l, p < 0.001). Serum ionized magnesium showed a significant negative correlation with plasma HbA1c and triglycerides in both microalbuminuria and clinical proteinuria groups. Multiple linear regression analysis showed that circulating ionized magnesium levels decrease together with the increase of plasma HbA1c and triglycerides in NIDDM patients with incipient or overt nephropathy, also after adjusting for age, sex, BMI, diabetes duration, systolic and diastolic blood pressure, hypoglycemic therapy, plasma creatinine, creatinine clearance, plasma cholesterol and fasting glucose. CONCLUSIONS: Microalbuminuria and clinical proteinuria, as well as poor glycometabolic control and hypertriglyceridemia, are associated to relevant alterations in magnesium metabolism, and the measurement of serum ionized magnesium seems to represent a useful biochemical tool for the study of magnesium disturbances in patients with different grades of diabetic nephropathy.     

Decreased renal clearance of xanthine and hypoxanthine in a patient with renal hypouricemia: a new defect in renal handling of purines.

Renal handling of urate, xanthine and hypoxanthine was studied in a hypouricemic patient who had increased plasma concentrations of xanthine and hypoxanthine. The patient, a 50-year-old man, had been suffering from Parkinson's disease, while neither systemic disorders nor particular renal diseases known to affect plasma purine levels were found. His serum urate level was 58 +/- 6 mumol/l (healthy controls for males, 310 +/- 48 mumol/l, mean +/- SD) and the renal uric acid clearance was 3 times higher than that of the controls, establishing a diagnosis of renal hypouricemia. Xanthine and hypoxanthine concentrations in the plasma were elevated to 1.3 +/- 0.1 mumol/l (controls, 0.5 +/- 0.3) and 5.9 +/- 3.5 mumol/l (controls, 1.6 +/- 0.4), respectively. Both renal xanthine and hypoxanthine clearance was only half the value of the controls, indicating reduced urinary excretion of xanthine, and hypoxanthine appears to be responsible for their elevation in plasma. A probenecid loading test revealed no response of urinary urate excretion but normal responses of xanthine and hypoxanthine excretion. However, urinary excretion of urate, xanthine or hypoxanthine did not respond at all to pyrazinamide administration. These findings indicate that the patient had a defective renal handling of xanthine and hypoxanthine as well as urate.     

Plasma total homocysteine and cysteine in relation to glomerular filtration rate in diabetes mellitus

BACKGROUND: The plasma concentrations of total homocysteine (tHcy) and total cysteine (tCys) are determined by intracellular metabolism and by renal plasma clearance, and we hypothesized that glomerular filtration is a major determinant of plasma tHcy and tCys. We studied the relationships between the glomerular filtration rate (GFR) and plasma tHcy and tCys in populations of diabetic patients with particularly wide ranges of GFR. METHODS: We measured GFR, urine albumin excretion rate (UAER), plasma tHcy, tCys, methionine, vitamin B12, folate, C-peptide, and routine parameters in 50 insulin-dependent diabetes mellitus (IDDM) and 30 non-insulin-dependent diabetes mellitus (NIDDM) patients. All patients underwent intensive insulin treatment and had a serum creatinine concentration below 115 micromol/liter. RESULTS: Mean plasma tHcy in diabetic patients (0.1 micromol/liter) was lower than in normal persons (11.1 micromol/liter, P = 0.0014). Mean plasma tCys in diabetic patients (266.1 micromol/liter) was also lower than in normal persons (281.9 micromol/liter, P = 0.0005). Seventy-three percent of the diabetic patients had relative hyperfiltration. Plasma tHcy and tCys were closely and independently associated with GFR, serum folate, and serum B12. However, plasma tHcy was not independently associated with any of the 22 other variables tested, including age, serum creatinine concentration, UAER, total daily insulin dose, and glycemic control. CONCLUSIONS: Glomerular filtration rate is an independent determinant of plasma tHcy and tCys concentrations, and GFR is rate limiting for renal clearance of both homocysteine and cysteine in diabetic patients without overt nephropathy. Declining GFR explains the age-related increase in plasma tHcy, and hyperfiltration explains the lower than normal mean plasma tHcy and tCys concentrations in populations of diabetic patients.     

Increased glomerular filtration rate as a predictor of diabetic nephropathy--an 8-year prospective study.

The objective was to study the natural history and the predictive value of glomerular filtration rate, albumin excretion rate, blood pressure, and hemoglobin A1c for diabetic nephropathy. A cohort of 75 type-1 diabetic adolescents with a diabetes duration of 8 years was studied. Thirty-one females, 33 males, mean age 16.9 +/- 0.3 (SEM) participated in the follow-up study. Glomerular filtration rate, albumin excretion rate, blood pressure, and hemoglobin A1c were measured every second year during 8 years to determine the predictive value of glomerular filtration rate for future nephropathy. Initial differences and patterns of changes in glomerular filtration rate, albumin excretion rate, and hemoglobin A1c were examined in patients who did (group 1) and did not (group 2) develop incipient or overt nephropathy. Five of 64 patients developed overt nephropathy. They had an initial glomerular filtration rate of greater than 125 ml/min/1.73 m2. Fifteen of 53 initially normoalbuminuric patients developed incipient and three of 53 overt nephropathy. Age, age at onset, diabetes duration, initial albumin excretion rate, initial blood pressure, and hemoglobin A1c were similar in groups 1 and 2. Glomerular filtration rate was initially higher in group 1 than in group 2 (P = 0.01). The positive predictive value for combined incipient and overt nephropathy of an initial glomerular filtration rate greater than 125 ml/min was 53%. The negative predictive value of glomerular filtration rate less than 125 ml/min was 95%. In initially normoalbuminuric patients multiple regression revealed initial glomerular filtration rate as the only significant independent predictor for nephropathy when also corrected for hemoglobin A1c (P = 0.04).(ABSTRACT TRUNCATED AT 250 WORDS)     

Renal tubular hypouricemia: evidence for defect of both secretion and reabsorption

Two patients had hypouricemia due to increased uric acid clearance. They showed no decrease of urate clearance to creatinine clearance ratio (Cua/Ccr) following pyrazinamide administration, and no increase of Cua/Ccr after probenecid. One patient showed a limited decline in Cua/Ccr after intravenous furosemide. In the other patient, neither acetylsalicylate nor furosemide produced any noticeable change in Cua/Ccr. Both showed a normal diuretic response after intravenous furosemide. The results indicate that they had massive defects in urate transport along the nephron, probably including both secretion and reabsorption.     

Two cases of nephrotic syndrome (NS)-induced acute kidney injury (AKI) associated with renal hypouricemia

Renal hypouricemia is a clinical disorder attributed to an increased renal urate excretion rate and is well known to involve a high risk of urolithiasis and exercise-induced acute kidney injury (AKI). This report concerns two interesting cases of nephrotic syndrome (NS)-induced AKI associated with renal hypouricemia. A 64-year-old female (Case 1) and a 37-year-old male (Case 2) were hospitalized because of AKI (serum creatinine: 2.07 mg/dl and 3.3 mg/dl, respectively), oliguria and NS. They were treated with prednisolone and temporary hemodialysis. Renal function improved, but hypouricemia persisted during hospitalization. Histological findings in both cases led to a diagnosis of minimal change nephrotic syndrome and identification of the diuretic phase of tubulointerstitial damage because of findings such as acute tubular necrosis. Furthermore, distal tubules of Case 2 showed an amorphous mass, possibly a uric acid crystal. Analysis of the two cases with the URAT1 gene, encoded by SLC22A12, found a homozygous mutation in exon 4 (W258stop) of each one. Our cases show that patients with renal hypouricemia may be susceptible to AKI without involvement of exercise if they possess some facilitators. Renal hypouricemic patients should therefore be carefully examined for all complications from renal hypouricemia because of high risk of AKI.     

Hypouricemia due to increased tubular urate secretion

A 45-year-old woman had hypouricemia (serum uric acid, 1.0-2.3 mg/dl) with increased uric acid clearance (29.8 +/- 9.3 ml/min/1.73 m2). Uric acid clearance to creatinine clearance ratio (Cua/Ccr) was suppressed markedly by pyrazinamide to 2.3% and surprisingly enhanced by probenecid to 227.8%. No other renal tubular or metabolic abnormalities were detected. This previously unreported high postprobenecid Cua/Ccr suggests that markedly increased urate secretion by the renal tubule is responsible for hypouricemia in this patient.     

Glomerular hyperfiltration and increased glomerular filtration surface are associated with renal function decline in normo- and microalbuminuric type 2 diabetes

The prevalence of glomerular hyperfiltration in type 2 diabetic patients varies widely. Here we studied whether glomerular hyperfiltration in diabetic nephropathy in type 2 patients is related to renal structural changes and predicts the functional development of diabetic nephropathy. Thirty normo- or microalbuminuric type 2 diabetic patients having a renal biopsy were followed every 6 months for a mean of 6.2 years. The glomerular filtration rate (GFR) at the time of biopsy, determined by iohexol clearance, correlated with filtration surface per glomerulus, but no other quantitative microscopic morphometric parameter. The filtration surface was positively associated with the decrease in GFR during the first year but not associated in subsequent years following the renal biopsy. The GFR showed a statistically significant linear decrease in 9 of the 30 patients; however, slopes of the regression lines were almost zero in 11 patients. The GFR increased and decreased in a parabolic manner in two patients. Seven of the nine patients with a statistically significant decline in renal function did not show any appreciable worsening of albuminuria, while two patients developed persistent proteinuria. Thus, in renal biopsy-proven normo- or microalbuminuric type 2 diabetic patients, glomerular hyperfiltration is closely associated with an increased glomerular filtration surface. An elevated GFR predicts its subsequent decline, which may occur without worsening of albuminuria.     

Exercise-induced acute renal failure in 3 patients with renal hypouricemia

Three cases of exercise-induced non-oliguric acute renal failure in patients with renal hypouricemia, an isolated defect of the renal urate transport system, are described. During acute renal failure, the serum uric acid levels were 5.6, 2.7 and 5.8 mg/dl, respectively, and were within normal limits. The values representing the fractional excretion of uric acid (FEUA) were 28.7, 60.0 and 12.7%, with accompanying serum creatinine levels of 8.1, 3.9 and 3.3 mg/dl, respectively. After recovery, the serum uric acid fell to 0.6, 0.7 and 1.0 mg/dl and the FEUA increased to 79.3, 52.8 and 43.2%, respectively. Two of the patients examined exhibited decreased reabsorption of filtered urate. These 3 examples of renal hypouricemia represented 23% of 13 cases of mild exercise-induced acute renal failure encountered within our experience.     

Glomerular size-selective dysfunction in NIDDM is not ameliorated by ACE inhibition or by calcium channel blockade

BACKGROUND: In patients with insulin-dependent diabetes mellitus (IDDM) and overt nephropathy glomerular barrier size-selectivity progressively deteriorates with time and is effectively improved by angiotensin converting enzyme (ACE) inhibition. Whether similar glomerular functional changes develop in proteinuric patients with non-insulin-dependent diabetes mellitus (NIDDM), and whether antihypertensive agents can favorably affect glomerular filtration of macromolecules in these patients, has not been documented yet. METHODS: We investigated renal hemodynamics and fractional clearance of neutral dextrans of graded sizes, in nine proteinuric patients with NIDDM and renal biopsy findings of typical diabetic glomerulopathy. Six healthy volunteers served as controls. We also investigated the effects of an ACE inhibitor and of a calcium channel blocker, both given in doses targeted to achieve a comparable level of systemic blood pressure control, on glomerular hemodynamics and sieving function. Theoretical analysis of glomerular macromolecule transport was adopted to evaluate intrinsic glomerular membrane permeability properties. RESULTS: Fractional clearance of large macromolecules (42 to 66 A in radius) was significantly higher in diabetic patients than in controls, and the distribution of membrane pore radii was calculated to be shifted towards larger pore sizes in diabetics (mean radius increased from 55 to 60 A). Despite effective blood pressure control, neither antihypertensive affected glomerular hemodynamics to any significant extent. Fractional clearance of dextrans, as well as of albumin and IgG, and total urinary proteins were not modified by either treatments. CONCLUSIONS: These data indicate that patients with NIDDM and overt nephropathy develop abnormalities in size-selective function of the glomerular barrier and, at variance to IDDM, such changes were not ameliorated either by ACE inhibition or calcium channel blockade.     

Evidence of enhanced uric acid clearance in macrohematuric patients with IgA nephropathy: prognostic significance of macrohematuria

Renal handling of uric acid and clinical prognosis following episodes of macroscopic hematuria (EMH) were examined in 113 patients with IgA nephropathy (IgAN). EMH was observed in 34 out of 113 patients (30.1%). The levels of blood urea nitrogen, proteinuria, serum uric acid, beta 2-microglobulin in sera and the degrees of glomerular sclerosis in renal tissues in macrohematuric patients were significantly decreased than those in patients without EMH. The levels of uric acid clearance (Cua) and fractional excretion of uric acid (FEua) was significantly enhanced in macrohematuric patients (p less than 0.01, p less than 0.05, respectively). There was a significant correlation between the tubular atrophy and the levels of Cua in macrohematuric patients (p less than 0.005). The levels of serum creatinine in macrohematuric patients before and after three years were significantly decreased when compared with microhematuric patients (p less than 0.005). It is concluded that enhanced Cua was related to renal tubular atrophy, and EMH did not clinically influence the glomerular deterioration in patients with IgAN.     

Underexcretory-type hyperuricemia, disproportionate to the reduced glomerular filtration rate, in two boys with mild proteinuria

Two unrelated boys with mild persistent proteinuria and underexcretory-type hyperuricemia of more than 9.0 mg/dl (535 mumols/l) are described. The proteinuria was detected at age 10 and 6 years, respectively. The fractional excretion of uric acid in both was low at 2-3%, when the creatinine clearance was decreased by about 50%. Tissue examination revealed focal interstitial fibrosis in both patients and medullary urate crystals in one patient in whom medullary tissue was obtained on biopsy. An immunofluorescence study was negative for immunoglobulins, complements and fibrin. Treatment of hyperuricemia did not prevent further deterioration of their renal function. One of them underwent a renal transplantation and then his serum uric acid level returned to the normal range. Neither patient had a family history of hyperuricemia, gout or inherited progressive renal disease. Both patients are likely to be sporadic cases of familial nephropathy with gout, an autosomal dominant disease, due to a new mutation. Hyperuricemia due to diminished uric acid clearance may be a risk factor or predictor for the development of progressive renal disease in some subjects.     

Hypouricemia, an old subject and new concepts

DEFINITION OF HYPOURICEMIA: Hypouricemia (serum uric acid less than 120 micro mol/l) is a biological abnormality often discovered accidentally and with a low prevalence depending on its permanent or transitory nature ranging from 0.15 to 3.38%. NEW PHYSIOLOGICAL CONCEPTS OF ITS PATHOGENESIS: Recently, our knowledge of the physiopathological mechanisms of hypouricemia has been emphasized by the identification of three systems of renal and extra-renal uric acid transport: a Cl/urate (URAT1) transporter, a multispecific organic anion transporter (OAT) and a urate transporter/channel. ETIOLOGY AND COMPLICATIONS OF HYPOURICEMIA: Through questioning, drugs and toxics (allopurinol.) are generally rapidly recognized as responsible for half of the hypouricemia encountered. It can be concomitant to a known disease: severe liver disease, neoplasia, diabetes, AIDS, syndrome of inappropriate antidiuretic hormone secretion. Hypouricemia can also be isolated and justifies the measurement of uric acid clearance, the normality or reduction of which orients towards a deficiency in xanthine-oxydase, the increase in which suggests an abnormality in uric acid transport in the proximal tubule (Fanconi syndrome, primary hereditary anomaly of tubular uric acid transport). Hypouricemia does not appear to expose the patient to any danger, but the onset of nephrolithiasis or acute renal failure secondary to the combination of severe hypouricemia and oxidant stress is always possible.     

贫血加重IgA肾病患者的临床和病理改变

目的 分析IgA肾病合并贫血患者的临床病理特征.方法 收集经肾活检确诊的IgA肾病患者临床资料409例,按照贫血与否分为非贫血组和贫血组,回顾性分析两组患者的临床和病理资料.结果 与非贫血组比较,贫血组患者的肾小球损伤和肾小管间质萎缩程度较重、24 h尿蛋白增多和eGFR降低.Spearman相关分析结果显示,血红蛋白、eGFR与肾脏病理损伤呈负相关(P＜0.05),血尿酸、24h尿蛋白与肾脏病理损伤呈正相关(P＜0.05).多因素Logistic回归分析发现贫血是肾小管间质萎缩的独立危险因素.结论 IgA肾病合并贫血患者的临床和病理损伤重于IgA肾病非贫血的患者,贫血参与IgA肾病的进展.     

Two cases of persistent hypouricemia associated with diabetes mellitus.

Two patients with diabetes mellitus had persistent hypouricemia due to increased urate clearance; the degree of the apparent renal hypouricemia with uricosuria was quite mild. At the onset of diabetes, their serum urate levels were normal. Even after good diabetes control in both cases, hypouricemia continued. Based on the pharmacological evaluation in both patients, pyrazinamide administration could partially decrease urate clearance, however, suppression by pyrazinamide was less than in normal subjects, and probenecid increased urate clearance. These results suggest that the present cases had a renal abnormality affecting tubular presecretory reabsorption of urate, which might be due to diabetes mellitus.     

Clinical predictors of non-diabetic renal disease in patients with non-insulin dependent diabetes mellitus

Background: Several studies had suggested that non-diabetic renal disease (NDRD) was common among non-insulin dependent diabetes mellitus (NIDDM) patients with renal involvement. Methods: We prospectively studied the prevalence of NDRD among a Chinese NIDDM population. Renal biopsy specimens were evaluated with light-, immunohistological and electron-microscopy. The cohort consisted of 51 patients who had NIDDM and proteinuria >1 g/24 h. Results: Patients with both isolated diabetic nephropathy (DN, n=34) and NDRD (n=17) had comparable duration of DM, creatinine clearance, serum creatinine, albumin and glycosylated haemoglobin levels, as well as incidences of retinopathy, neuropathy and hypertension. Significantly more patients with NDRD had microscopic haematuria (P=0.043) or non-nephrotic proteinuria (P=0.004). IgA nephropathy accounted for 59% of the NDRD identified. Conclusions: In this study, microscopic haematuria and non-nephrotic proteinuria predicted the presence of NDRD among NIDDM patients presenting with renal disease.     

Hemodynamic alterations in long-term insulin-dependent diabetic patients with overt nephropathy: role of blood hyperviscosity and plasma protein changes

The possible relationship among blood rheology pattern, renal hemodynamics and proteinuria was investigated in 22 long-term insulin-dependent diabetic patients with overt nephropathy. Higher blood, plasma and serum viscosity and lower erythrocyte filtrability were found in our patients with overt nephropathy, than in patients without renal microvascular complications. Several negative correlations between blood viscosity and renal hemodynamic parameters (i.e., glomerular filtration rate and renal plasma flow) were demonstrated in the diabetics with overt nephropathy. Furthermore increased plasma fibrinogen, fibronectin and acute-phase protein levels were found in diabetics with overt nephropathy, compared to diabetics without renal changes. The data may suggest a pathogenetic role for blood rheology changes in the progression of diabetic glomerular complications.     

Insulin-dependent diabetes and renal hypouricemia

We studied 14 patients (11 women and 3 men) from 18 to 33 years old, suffering from type I diabetes mellitus with normal renal function (creatinine clearance 106.91 +/- 28.73 ml/min) and serum uric acid below 2.5 mg/dl (2.34 +/- 0.11 mg/dl) as well as a high uric acid clearance (23.04 +/- 5.92 ml/min) and fractional urate excretion (21.4 +/- 2.6) versus urate clearance 9.82 ml/min and fractional urate excretion 8.80 +/- 1.3 in 14 normal control subjects. The study of the uricosuric mechanisms was conducted by the combination of probenecid (PB) test which inhibits the reabsorption of secreted urate, and pyrazinamide (PZA) test, which inhibits its tubular secretion. The results of studies indicate that the increase in urate clearance was accounted for by increased PZA-nonsuppressible urate suggesting a decreased reabsorption of filtered urate. Increased PZA-suppressible urate excretion combined with impaired response to a uricosuric drug is consistent with impaired reabsorption of secreted urate. According to our findings, increased urate excretion in diabetic patients may be attributed to the inhibition of both filtered and secreted reabsorption. This reabsorptive tubular abnormality is consistent with the view of an interference of tubular reabsorption of glucose with the tubular capacity for uric acid reabsorption.