Acquired distal renal tubular acidosis

Antimicrobial-associated renal tubular acidosis

OBJECTIVE

To review the literature documenting the association of various antimicrobial medications with the development of renal tubular acidosis (RTA).

DATA SOURCES

A search of the English literature via MEDLINE (1966-November 2003) and International Pharmaceutical Abstracts (1970-November 2003) was conducted to identify human reports of RTA associated with various drugs from all available classes of antimicrobial agents. Major search terms included renal tubular acidosis, acidosis, antibiotics, and antimicrobials. Bibliographies of selected articles were also searched to identify additional reports of RTA.

STUDY SELECTION AND DATA EXTRACTION

Case reports, observational studies, and experimental studies documenting the association of any antimicrobial agent with the development of RTA were included.

DATA SYNTHESIS

Antimicrobial-associated RTA is a relatively uncommon adverse effect, with most reports involving amphotericin B, trimethoprim/sulfamethoxazole, and outdated tetracycline. These agents may induce RTA either through direct tubular toxicity or as a function of their pharmacologic action. The time course for the development of RTA varies depending on the antimicrobial utilized. In most instances, RTA is reversible; however, some patients may experience prolonged recovery after the offending agent is removed.

CONCLUSIONS

Given that antimicrobial-associated RTA is a relatively uncommon adverse effect, review of the patient's drug regimen may reveal these agents as otherwise unrecognized causes of RTA. Likewise, underlying causes of RTA other than medications must be ruled out. Diagnosing antimicrobial-induced RTA may be difficult, given many of these agents may be used in combination and some are intrinsically nephrotoxic.

Environmental distal renal tubular acidosis in Thailand: an enigma

Distal renal tubular acidosis is a common health problem in northeastern Thailand, with the population background of the low potassium intake, low urine citrate, and decreased red blood cell Na-K adenosine triphosphatase (ATPase) activity and the environment of the high soil vanadium. The disease is usually seen in the people with low socioeconomic status in summer. The patients have decreased gastric acidity and low urine potassium. There are varying degrees of renal function from normal to impairment. Gastric hypoacidity is an important clue. Defects in H-K ATPase and anion exchange (AE2) mechanism are considered. The urine vanadium is higher in the patients than that of normal rural northeastern villagers. Inhibition of H-K ATPase by vanadium seems possible and requires more supporting evidence. AE1 gene mutation is noted in few patients. The cause of dRTA is not apparent. The AE2 gene and H-K ATPase gene remain to be studied. Both environmental and genetic factors could contribute to the pathogenesis of the disease.

The importance of tubulointerstitial injury in the early phase of primary glomerular disease

OBJECTIVES

As tubulointerstitial damage is regarded secondary to glomerular injury in primary glomerulopathies, we assessed lesions to renal tubulointerstitium in recently diagnosed primary glomerular diseases and evaluated their impact on progression of the disease during the first 2 years after diagnosis.

DESIGN

A nonrandomized prospective study assessing tubulointerstitial morphometry at diagnosis, markers of tubular function within the next 6 months and progression of the disease (creatinine clearance) during 24 months' follow-up.

SETTING

Single tertiary referral centre.

SUBJECTS

Forty-six patients with primary glomerular disease, the diagnostic oligobiopsy performed within 2 months of the onset of clinical symptoms.

INTERVENTIONS

All patients were subjected to antiinflammatory/immunosuppressive treatment.

MAIN OUTCOME MEASURES

Alterations in results of tubulointerstitial morphometry and tubular function tests, correlations between these variables and parameters of nephrosis/renal function, selection of the most accurate predictor of disease progression within 24 months after diagnostic biopsy.

RESULTS

Function of proximal tubules, markedly deteriorated at the time of diagnosis, significantly improved 6 months later (urinary beta2-microglobulin: P < 0.0025), along with reduction in proteinuria (P < 0.00125). No appreciable alterations in function of distal tubules were noted. Morphometric indices revealing interstitial expansion and tubular atrophy significantly correlated with creatinine clearance at 6 months (P = 0.032) and were the best predictors of deteriorating renal function at 24 months. Excretion of beta2-microglobulin at the time of diagnosis was the best marker for impairment of glomerular filtration 6 months later.

CONCLUSIONS

Significant damage to cortical tubulointerstitium occurs concurrently with glomerular injury in primary glomerulopathies and may predict the clinical course of the disease already in its initial phase.

Use of the urine-to-blood carbon dioxide tension gradient as a measurement of impaired distal tubular hydrogen ion secretion among neonates

To evaluate the utility of the urinary-minus-blood partial pressure of carbon dioxide (U-B PCO2) gradient for the diagnosis of distal renal tubular acidosis in neonates, we measured the U-B PCO2 gradient corresponding to different urinary bicarbonate concentrations in 40 neonates. The U-B PCO2 gradient in these neonates had a significant linear relationship to the urinary bicarbonate concentration. When the urinary bicarbonate concentration was > 10 mmol/L, in all the neonates the U-B PCO2 could be increased above the 20 mm Hg level. We conclude that it is appropriate to determine the U-B PCO2 gradient as an index of distal urinary acidification and that it is a necessary test for diagnosis of distal renal tubular acidosis in neonates.

Urine-to-blood carbon dioxide tension gradient and maximal depression of urinary pH to distinguish rate-dependent from classic distal renal tubular acidosis in children

We determined the prevalence and clinical features of rate-dependent distal renal tubular acidosis (dRTA) in 31 children examined for possible renal tubular acidosis by measuring the urinary-minus-blood partial pressure of carbon dioxide (U-B PCO2) gradient, minimal urinary pH, and fractional excretion of bicarbonate. Of 20 patients with low U-B PCO2 gradients, nine could not lower urinary pH < or = 5.5, indicating classic dRTA, whereas 11 could lower urinary pH < or = 5.5, as described in rate-dependent dRTA. When patients with rate-dependent dRTA and classic (type I) dRTA were compared, there was no difference in the mean U-B PCO2 gradient or in clinical findings, including age, reason for referral, presence of nephrocalcinosis, or depression of linear growth. We conclude that children with rate-dependent dRTA are susceptible to at least some of the same sequelae as children with classic dRTA. Measurement of minimal urinary pH will not detect this subtle form of dRTA. Determination of the U-B PCO2 gradient should be considered a routine part of evaluation for suspected renal tubular acidosis in a child.

Kidney function in very low birth weight infants with furosemide-related renal calcifications at ages 1 to 2 years

To determine whether long-term renal sequelae follow the use of furosemide in preterm infants, we evaluated renal function in 27 former very low birth weight infants (less than 1500 gm) at 1 to 2 years of age. Patients were classified into three groups on the basis of status at the time of discharge from the hospital: group 1 (n = 7) had no furosemide treatment or renal calcifications, group 2 (n = 10) had furosemide therapy but no calcifications, and group 3 (n = 10) had furosemide therapy with renal calcifications. Renal ultrasonography at the time of the study demonstrated resolution of the calcifications in six patients in group 3. No differences in renal function were observed between groups 1 and 2. Creatinine clearance (mean +/- SEM) in group 3 (83.6 +/- 7.8 ml/min per 1.73 m2) was significantly lower than clearance in groups 1 and 2 (103.2 +/- 6.5 and 109.1 +/- 5.1, respectively; p less than 0.05). Children in group 3 had significantly higher urinary calcium/creatinine ratios and fractional excretion of sodium and lower tubular reabsorption of phosphate than children in the two other groups had. Urine-blood difference in carbon dioxide tension after oral acetazolamide load, which indicates the ability of the distal tubule to secrete hydrogen ions, was 8.4 +/- 3.4 mm Hg in group 3, significantly lower than values in groups 1 and 2 (22.6 +/- 3.1 and 28.0 +/- 4.3 mm Hg, respectively, p less than 0.05). Within group 3 the four children with persistent renal calcifications had significantly lower urine-blood carbon dioxide tension differences than did those with resolution of calcifications (p = 0.02). We conclude that furosemide-related renal calcifications in very low birth weight infants may lead to glomerular and tubular dysfunction; further long-term follow-up of this population is recommended.

Urinary acidification in renal stone patients from northeastern Thailand

Hypokalemia, hypokaliuria and hypocitraturia are common findings in patients with renal stone disease in Northeastern Thailand. However, hyperchloremic metabolic acidosis seldom is seen. Therefore, we studied renal acidification in 29 renal stone disease patients who were living in rural Northeast Thailand. Baseline blood and average 24-hour urine biochemical parameters were measured. Hypokalemia, hypokaliuria and hypocitraturia were found in 10%, 83% and 93% of the patients, respectively. By multiple regression, urinary citrate excretion correlated positively with serum potassium and urinary potassium excretion, and negatively with urinary ammonium (r = 0.640, p = 0.005). An abnormal response to acid loading was found in only 1 patient. Thus, hypokaliuria and hypocitraturia in our renal stone disease subjects were infrequently due to distal renal tubular acidosis. Perhaps potassium depletion might be a contributing factor in these metabolic abnormalities.

[Kidney function of patients with healthy kidneys during cyclosporin treatment]

Long-term administration of ciclosporin has been complicated by side-effects, the predominant being nephrotoxicity. We performed renal function studies on 20 patients treated with ciclosporin (group 1) and on 12 patients serving as controls (group 2). Only patients with serum creatinine less than 1.3 mg/dl entered the study. The renal function studies consisted of: Inulin clearance, PAH clearance, sodium sulphate loading, sodium bicarbonate loading. Plasma renin activity (PRA), inactive renin (IR) and aldosterone (ALDO) were measured basally and after stimulation with 40 mg furosemide i.v. Serum creatinine was not significantly impaired under ciclosporin with 1.1 +/- 0.1 mg/dl vs 0.9 +/- 0.1 mg/dl in the control group (ns). Glomerular filtration rates as measured by creatinine and inulin clearance were significantly impaired in group 1 as compared to group 2. Inulin clearance was impaired by ciclosporin with 93.5 +/- 4.4 ml/min/1.73 m2 as compared to 121 +/- 6.6 ml/min/1.73 m2 (p less than 0.05) in patients of group 2. The PAH clearance in ciclosporin treated patients was impaired, with 379 +/- 22.1 ml/min/1.73 m2 in group 1 as compared to 605 +/- 39 ml/min/1.73 m2 (p less than 0.001) in group 2. Mean arterial pressure and renovascular resistance were significantly increased in ciclosporin treated patients. We demonstrated, by means of sodium sulphate and bicarbonate loading, incomplete distal tubular acidosis in 3 patients from group 1 but in none of group 2. There was no difference in basal plasma renin activity (PRA), but during volume contraction induced by furosemide there was only blunted response by PRA in patients receiving ciclosporin with 2.7 +/- 0.3 ng/ml/h as compared to 7.7 +/- 0.5 ng/ml/h in controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Oral acetazolamide in the assessment of (urine-blood) PCO2

Urine-blood (U-B)Pco2 difference in children is usually assessed following urine alkalinization with oral sodium bicarbonate (NaHCO3). Since oral NaHCO3 is often poorly tolerated by children, we compared oral acetazolamide with oral NaHCO3 in a study of (U-B)Pco2. In the first phase of the study 14 children and adolescents aged 11.1 +/- 3.7 years (mean +/- SD) were studied. Eight participants had normal kidney function and 6 had disturbed distal acidification capacity. Each child was studied twice, once with oral NaHCO3 (2.5 mEq/kg) and once with acetazolamide (17 +/- 2 mg/kg). All studies were performed according to the standard protocol. Acetazolamide administration resulted in a lower blood pH than NaHCO3 (7.30 +/- 0.03 vs 7.38 +/- 0.06, P less than 0.001) and a lower serum bicarbonate (HCO3-) concentration (25.1 +/- 2.2 mEq/l vs 27.5 +/- 2.1 mEq/l, P less than 0.025). Acetazolamide also resulted in a higher urine Pco2 (81.9 +/- 26.2 mm Hg vs 71.6 +/- 18.2 mm Hg) than NaHCO3 (P less than 0.025). No significant differences between acetazolamide and NaHCO3 were observed with respect to their effects on urinary pH and HCO3- concentration, plasma Pco2 and (U-B)Pco2. Good linear correlations were found between the effects of acetazolamide and NaHCO3 on urine Pco2 (r = 0.878, P less than 0.001), and on (U-B)Pco2 (r = 0.795, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Renal tubular acidosis

The term renal tubular acidosis (RTA) is applied to a group of transport defects in the reabsorption of bicarbonate (HCO3-), the excretion of hydrogen ions, or both. On clinical and pathophysiological grounds, RTA can be separated into three main types: distal RTA (type 1), proximal RTA (type 2) and hyperkalaemic RTA (type 4). Some patients present combined types of proximal and distal RTA or of hyperkalaemic and distal RTA. Diagnosis of RTA should be suspected when a patient presents a normal plasma anion gap, and hyperchloraemic metabolic acidosis. A normal plasma anion gap (Na(+)-[Cl- + HCO3-] = 8-16 mEq/l) reflects loss of HCO3- from the extracellular fluid via the gastro-intestinal tract or the kidney, dilution of extracellular buffer or administration of hydrochloric acid (HCl) or its precursors. Distinction of RTA from other disorders is greatly facilitated by the study of the urine anion gap (Na+ + K+ - Cl-). This index estimates the urinary concentration of ammonium in a patient with hyperchloraemic metabolic acidosis. A negative urine anion gap (Cl- much greater than Na+ + K+) suggests the presence of gastro-intestinal or renal loss of HCO3-, while a positive urine anion gap (Cl- less than Na+ + K+) is indicative of a distal acidification defect. Determination of plasma potassium, of urine pH at low plasma HCO3- concentration, and of urine PCO2 and fractional excretion of HCO3- at normal plasma HCO3- concentration permits the differentiation between the various types of RTA.

An in vivo study of voltage-dependent renal tubular acidosis induced by amiloride

It has been proposed that most forms of hyperkalemic distal renal tubular acidosis (dRTA) result from a voltage-dependent acidification defect in the cortical collecting tubule (CCT) in which hydrogen and potassium secretion are decreased secondary to a reduced, transepithelial potential difference (PD) arising from impaired sodium reabsorption. The present in vivo study examines one model of hyperkalemic dRTA, induced by chronic amiloride administration, to examine the relationship between urinary excretion of hydrogen and potassium ions and CCT PD in the rat kidney. Chronic administration of amiloride produced a significant metabolic acidosis with a plasma bicarbonate of 21.3 mmol/liter compared to 25.9 mmol/liter in control rats. Plasma potassium was higher in experimental animals (4.9 mmol/liter vs. 3.3 mmol/liter in controls) and was associated with a significantly reduced fractional excretion of potassium of 11.2% versus 37.4% in controls. When animals were loaded with DOCA and infused with 4% sodium sulphate to maximize urine acidification, urine pH was significantly higher in the experimental group (6.35 vs. 5.55 in controls) while the mean PD in cortical collecting tubules was markedly lower at -21.1 mV versus -58.9 mV in controls. These results support a voltage dependent mechanism to explain the defect in hydrogen and potassium ion secretion induced by amiloride.

Effect of amphotericin B on renal tubular acidification in the rat

Amphotericin B, a polyene antibiotic known to induce cation-selective pore formation in biological cell membranes, was given to rats by peritoneal injection (10 mg/kg for 21-26 days) or added to luminal perfusates (2 x 10(-5) M). Kinetics of tubular acidification and alkalinization after perfusion with alkaline or acid phosphate Ringer's solution was studied by means of double barrelled antimony/reference microelectrodes in cortical distal tubules. Stationary pH increased both in early and late distal segments. Acidification and alkalinization half-times decreased markedly from 15-18 s to 6-8 s, a value similar to that found in proximal tubule. Net H-ion secretion rates as well as H-ion back-flux approximately doubled after Amphotericin B. Apparent H-ion permeability of distal tubule epithelium measured during perfusion of lumen and peritubular capillaries with phosphate Ringer's solutions doubled both in early and late segments. These data show that amphotericin B produces a distal acidification defect which impairs formation of normal transepithelial pH gradients by increasing H-ion back-flux without reducing rates of net H-ion secretion.

The kidney in hypergammaglobulinemic purpura

A 25-year-old woman with long-standing hypergammaglobulinemic purpura developed distal renal tubular acidosis and a urine-concentrating defect. The acidification defect was characterized as suggestive of impaired distal proton secretion by infusion of neutral phosphate. The concentrating defect was a form of acquired nephrogenic diabetes insipidus. On renal biopsy, IgM mesangial nephropathy was found along with multiple large hyaline tubular casts. The renal findings in hypergammaglobulinemic purpura are reviewed.

The urine anion gap: a clinically useful index of ammonium excretion

In patients with a normal plasma anion gap type of metabolic acidosis, knowledge of the rate of ammonium excretion can provide valuable information to determine if there is a renal cause for the disorder. Unfortunately, few hospital biochemistry laboratories offer routine determination of the urine ammonium concentration. Data are presented that demonstrate a direct linear relationship between the urine anion gap (Na+ + K+ - Cl-) and the urine ammonium concentration. In a 24-hour urine collection, the relationship is urine ammonium equals -0.8 (urine anion gap) +82 (r = 0.97 p less than 0.01). The applications of this index of ammonium excretion are discussed.

Hyperkalemic distal renal tubular acidosis in salt-losing congenital adrenal hyperplasia

Functional indices of distal urinary acidification were assessed in two male infants, aged 1 and 3 months, with salt-losing congenital adrenal hyperplasia. In both cases the diagnosis was sustained by the presence of elevated plasma levels of 17-hydroxyprogesterone, hyponatremia, hyperkalemia, metabolic acidosis and increased plasma renin activity. Both patients were unable to lower urinary pH below 5.9 either during acute ammonium chloride-induced acidosis or after i.v. administration of furosemide. One patient also failed to decrease urine pH below 5.5 and to increase urinary potassium excretion during sodium sulfate infusion. Oral sodium bicarbonate loading was given to both patients but failed to induce a significant increase in the urine minus blood PCO2 gradient. This gradient remained low also after neutral phosphate administration. Repeated studies after acute administration of fludrocortisone in one case or after prolonged administration of hydrocortisone in the other resulted in complete normalization of all functional studies. We conclude that salt-losing congenital adrenal hyperplasia can lead to hyperkalemic distal renal tubular acidosis in early infancy. The defective renal secretion of hydrogen ion and potassium is probably related to the abolishment of the negative potential difference in the cortical collecting tubule induced by the impaired reabsorption of sodium.

Acid-base disturbances in liver disease

There are several important associations between the liver and acid-base balance. First, primarily because of its metabolism of certain cationic amino acids and organic acid anions, particularly lactate, the liver has a surprisingly important influence on normal acid-base homeostasis. Second, in the presence of the necessary pathogenic milieu, the liver may produce a life-threatening number of hydrogen ions. Examples include accelerated ketogenesis during insulinopenic states, or lactate production during severe hepatic parenchymal hypoxia. Third, patients with various types of liver disease, both acute and chronic, often develop complicating acid-base disturbances. In addition, liver disease may predispose the patient to a particular acid-base disorder such as phenformin-induced lactic acidosis. Finally, the acid-base disturbance may be a complication of therapy, as when diuretic therapy directed at ascites results in metabolic alkalosis.

Validation of the difference in urine and blood carbon dioxide tension during bicarbonate loading as an index of distal nephron acidification in experimental models of distal renal tubular acidosis

Recent classifications of the several pathophysiologic types of distal renal tubular acidosis (secretory, voltage dependent, and gradient) have been based on the response of acidification parameters to a series of provocative maneuvers in vivo and in vitro. A reduction in the difference in urine and blood CO2 tension during bicarbonate loading (U-B pCO2 gradient), a widely applied parameter, has been employed as an index of reduced distal nephron proton secretion. This study was designed to test the validity of the U-B pCO2 gradient in a variety of experimental models of distal renal tubular acidosis by measuring and comparing disequilibrium pH (a direct technique to detect H+ secretion in situ) with the pCO2 in the papillary collecting duct of the rat in vivo during bicarbonate loading. Chronic amiloride, lithium chloride, and amphotericin-B administration, and the post-obstructed kidney models were employed. Amiloride resulted in an acidification defect which did not respond to sulfate infusion (urine pH = 6.15 +/- 0.08), and was associated with an obliteration of the acid disequilibrium pH (-0.26 +/- 0.05- -0.08 +/- 0.03) and reduction in papillary pCO2 (116.9 +/- 3.2 - 66.9 +/- 2.5 mmHg). The defect induced by lithium administration responded to Na2SO4 (urine pH = 5.21 +/- 0.06) but was similar to amiloride with respect to the observed reduction in disequilibrium pH (-0.04 +/- 0.02) and pCO2 (90.3 +/- 3.0 mmHg). The post-obstructed kidney model was characterized by an abnormally alkaline urine pH unresponsive to sulfate (6.59 +/- 0.06) and a reduction in disequilibrium pH (+0.02 +/- 0.06) and pCO2 (77.6 +/- 3.6 mmHg). Amphotericin-B resulted in a gradient defect as characterized by excretion of an acid urine after infusion of sodium sulfate (5.13 +/- 0.06). Unlike other models, however, amphotericin-B was associated with a significant acid disequilibrium pH (-0.11 +/- 0.05) and an appropriately elevated urine pCO2 (119.8 +/- 6.4 mmHg) which did not differ from the respective values in control rats. Thus, these findings support the use of the U-B pCO2 as a reliable means of demonstrating impaired distal nephron proton secretion in secretory and voltage-dependent forms of distal renal tubular acidosis (RTA) and supports the view that proton secretion is not impaired in gradient forms of distal RTA.