Pembrolizumab-induced Acute Tubulointerstitial Nephritis Accompanying Fanconi Syndrome and Type 1 Renal Tubular Acidosis

Pembrolizumab, an immune checkpoint inhibitor, is used to treat a variety of refractory malignancies. However, these agents are sometimes associated with immune-related adverse events. A 71-year-old woman received pembrolizumab-integrated chemotherapy to treat her recurrent mandibular gingival cancer. Five months after stopping pembrolizumab, she developed acute tubulointerstitial nephritis associated with Fanconi syndrome and type 1 renal tubular acidosis, which resolved with steroid therapy. We experienced a case of pembrolizumab-induced Fanconi syndrome and type 1 renal acidosis. We recommend follow-up of the tubular function in addition to the renal function even after discontinuation of pembrolizumab.

Bone mineral density and growth changes in patients with distal renal tubular acidosis after two-years treatment with a new alkalizing drug (ADV7103)

BACKGROUND AND OBJECTIVES

ADV7103 is a new prolonged-release treatment for distal renal tubular acidosis (dRTA), containing potassium citrate and potassium bicarbonate. Since acidosis may affect bone mineral contents, the effects of ADV7103 on bone mineral density (BMD) and growth in patients with dRTA over 24 months were evaluated.

PATIENTS AND METHODS

Thirty patients (24 paediatric patients and 6 adults) were included in an open-label extension study after a phase II/III trial. BMD, measured by densitometry, was assessed at baseline and at 24 months. Growth was evaluated throughout the study. Plasma bicarbonate, parathyroid hormone, 25-hydroxy vitamin D, 1,25-dihydroxy vitamin D, bone alkaline phosphatase, calciuria and citraturia, were also determined. Safety and treatment compliance were evaluated as well.

RESULTS

After 24 months of treatment with ADV7103, mean spine BMD z-score values significantly increased as compared with baseline (p=0.024). In adults, spine and whole-body densitometry z-scores showed a significant correlation with plasma bicarbonate levels (rS=0.82 and rS=0.97, respectively, p<0.005). There was an increase>0.5 units in z-scores for height and weight in 18% and 36% of the paediatric patients, respectively. With treatment, plasma bicarbonate concentration and calciuria at the different visits were normal in 69-86% and 93-96% patients, respectively. Only nine treatment-related gastrointestinal AEs of mild/moderate severity, were reported in five patients.

CONCLUSIONS

Two years of ADV7103 treatment improved growth and increased spine BMD. These results suggest that control of acidosis by ADV7103 treatment improves bone parameters.

Zonisamide-induced distal renal tubular acidosis and critical hypokalaemia

A woman in her 20s presented with rapidly progressive muscle weakness and a 1-month preceding history of fatigability, nausea and vomiting. She was found to have critical hypokalaemia (K+ 1.8 mmol/L), a prolonged corrected QT interval (581 ms) and a normal anion gap metabolic acidosis (pH 7.15) due to zonisamide-induced distal (type 1) renal tubular acidosis. She was admitted to the intensive care unit for potassium replacement and alkali therapy. Clinical and biochemical improvement ensued, and she was discharged after a 27-day inpatient stay.

Severe Hypophosphatemia as the Initial Presentation of Renal Fanconi's Syndrome and Distal Renal Tubular Acidosis Related to Zoledronic Acid: A Case Report and Literature Review

INTRODUCTION

Zoledronic acid (ZA) is a widely used bisphosphonate compound for the prevention of skeletal metastasis-associated osteolysis and treatment of post-menopause osteoporosis. Acute kidney injury is one of the commonly described renal complications. Electrolyte disorder has also been reported relevant to ZA exposure and nephrotoxicity. Syndrome of persistent hypophosphatemia, hypokalemia, and metabolic acidosis is regarded as the initial signs of acute kidney injury.

CASE PRESENTATION

We reported a 64-year-old female with bone metastasis from lung adenocarcinoma who received a 5-year history of 4-week cycle of ZA infusion. She initially presented with symptomatic severe hypophosphatemia and was finally identified with ZA-induced generalized tubular dysfunction as Fanconi's syndrome and distal renal tubular acidosis. Renal pathological findings revealed toxic renal tubular necrosis. The ZA infusion was thus extended to an 8-week cycle with oral phosphate supplementation and alfacalcidol. Although periodic changes pre- and post-ZA infusion existed yet, hypophosphatemia was effectively improved, and the rapid decline of eGFR was partially delayed. We reviewed the literature and mainly summarized the characteristics of bisphosphonate-associated hypophosphatemia. Moderate hypophosphatemia was more frequently mentioned in contrast to severe cases being predisposed to be reported. Progressive hypophosphatemia serves as an early sign of kidney injury.

CONCLUSION

Progressive electrolyte disorders and CKD were the long-term renal outcomes of the current patient. We would like to arouse more attention to electrolyte imbalance related to early ZA-induced kidney injury and emphasize the significance of close monitoring.

Paint-thinner-induced Acute Kidney Injury: A Case Series and Review

Occupational health hazards contribute significantly to the morbidity and mortality of workers in factories. Toluene has become a widely abused inhaled volatile drug. The spectrum of toluene-induced renal injury includes rhabdomyolysis, myoglobinemia, distal renal tubular acidosis (RTA), acute tubular necrosis, glomerulonephritis, and interstitial nephritis. We describe two patients with paint-thinner-induced kidney injury who were affected through different routes of exposure and recovered well, with one requiring dialysis support; the second patient, who had developed Type 1 distal RTA and mild kidney injury, was managed with conservative measures. Toluene can cause acute neurological symptoms, accompanied by severe metabolic alterations, as well as organ injury and dysfunction. A common association of the development of hypokalemic paralysis and metabolic acidosis with toluene intoxication was observed. Liver injury and rhabdomyolysis are also common. Vomiting, dehydration, tubular injury, and rhabdomyolysis are all possible additional causes of acute renal failure in toluene intoxication. Type 1 distal RTA, which is characterized by an inability to lower urine pH despite acidemia, results in hyperchloremic metabolic acidosis with hypokalemia. The management of acute toluene toxicity is largely conservative, consisting of correcting the electrolytes and the acid-base balance, fluid alterations, and renal replacement therapy in severe acute kidney injury. A clinical suspicion of organ failure and prompt supportive care leads to encouraging results. Adequate protective steps for workplaces involved in the use of such substances in confined spaces include prior risk assessment, using low-toxicity chemical products, ensuring adequate ventilation, safety training, and using appropriate personal protective equipment.

Tenofovir disoproxil fumarate-induced distal renal tubular acidosis: A case report

Tenofovir disoproxil fumarate (TDF) is an anti-retroviral drug that is known to cause nephrotoxicity including renal tubular acidosis (RTA). With increasing literature on proximal RTA caused by TDF, reports on distal RTA are scarce, with only one case reported so far. We report a case of distal RTA in patient living with human immunodeficiency virus, who presented with nausea and fatigue giving a history of TDF-based therapy for two years. Laboratory investigations revealed non-anion gap metabolic acidosis, positive urine anion gap, hyperchloremia, and hypokalemia. The patient improved after discontinuing TDF and supportive management.

Harmful effects and acute lethal toxicity of intravenous administration of low concentrations of hydrofluoric acid in rats

The acute toxicity of hydrofluoric acid (HFA) was investigated in a 24-h lethal dose study of intravenous infusion in rats. The lethal dose lowest (LDLo) and LD50 were 13.1 and 17.4mg/kg, respectively. Harmful systemic effects were also studied 1 h after acute sublethal exposure to HFA. The maximum dose was set at 9.6mg/kg (LD 5). Rats were injected with HFA (1.6, 3.2, 6.4 or 9.6mg/kg), saline, sodium fluoride (NaF) or HCl solution. NaF and HCl solution concentrations corresponded to the F— and H+ concentrations of 9.6mg/kg HFA. Blood urea nitrogen (BUN) and Cr were significantly increased in response to HFA concentrations greater than 3.2mg/kg. Acute glomerular dysfunction also occurred at HFA concentrations greater than 3.2mg/kg. HCO 3 — and base excess (BE) were significantly decreased in the 6.4 and 9.6mg/kg groups. Ca2+ was significantly decreased, and K + was increased in the 9.6mg/kg group. BUN was significantly increased in the NaF and HFA groups and was increased in the HFA group compared with that in the NaF group. Cr was significantly increased in the HFA group only. HCO3 — and BE were significantly decreased in the NaF and HFA groups and were increased in the HFA group compared with values in the NaF group. Ca2+ was significantly decreased in the NaF and HFA groups, and K+ was significantly increased in the NaF and HFA groups. F— exposure directly affected serum electrolytes. Mortality was thought to be due to cardiac arrhythmia resulting from hypocalcemia and hyperkalemia. Metabolic acidosis and renal failure were more severe in response to HFA exposure than in response to NaF exposure because of more free F—, which has strong cytotoxicity, in the HFA group than in the NaF group. Lethal effects of HFA are promoted by exposure routes such as inhalation that cause rapid absorption into the body. Even low exposure to HFA can cause acute renal dysfunction, electrolyte abnormalities and metabolic acidosis. These complications result in a poor prognosis. Toxicology and Industrial Health 2007; 23: 5—12.

Late Metabolic Acidosis Caused by Renal Tubular Acidosis in Acute Salicylate Poisoning

A 16-year-old man was transferred to our emergency department seven hours after ingesting 486 aspirin tablets. His blood salicylate level was 83.7 mg/dL. He was treated with fluid resuscitation and sodium bicarbonate infusion, and his condition gradually improved, with a decline in the blood salicylate level. However, eight days after admission, he again reported nausea, a venous blood gas revealed metabolic acidosis with a normal anion gap. The blood salicylate level was undetectable, and a urinalysis showed glycosuria, proteinuria and elevated beta-2 microglobulin and n-acetyl glucosamine levels, with a normal urinary pH despite the acidosis. We diagnosed him with relapse of metabolic acidosis caused by renal tubular acidosis.

Metabolic acidosis in toluene sniffing

Toluene sniffing, frequently described under the generic category of "glue sniffing," is a potential cause of normal anion gap metabolic acidosis due to distal renal tubular acidosis. Urine anion gap is used to diagnose metabolic acidosis of a normal anion gap variety; however, pitfalls exist when using urine anion gap in the setting of toluene sniffing. We present the case of a young woman who had a normal anion gap metabolic acidosis due to toluene sniffing and an unexpectedly low urine anion gap. In such a scenario, the urine anion gap will underestimate the rate of ammonia excretion when the conjugate bases of acids other than HCl are excreted in large quantities. Estimation of the urine osmolal gap will provide a more accurate ammonia excretion rate in these circumstances. The challenges in interpretation of the urine anion gap and ammonia excretion in the setting of distal renal tubular acidosis due to toluene toxicity are discussed.

Pulmonary infiltrates with eosinophilia syndrome in ibuprofen overdose

We describe the case of a 45-year-old female who developed pulmonary infiltrates and mild eosinophilia following an overdose of ibuprofen. We believe this was a case of pulmonary infiltrates with eosinophilia (PIE) syndrome and discuss the relevant literature. Although rare, PIE syndrome should be considered in those taking nonsteroidal anti-inflammatories who develop unexplained pulmonary infiltrates.

[Migraine-induced kidney stones?]

A 42-year old woman was referred for a metabolic evaluation after two episodes of kidney stones. Her laboratory results revealed a normal anion-gap metabolic acidosis, a marked hypocitraturia (0,6 mmol/24h; norm 1,6-4,5) and a urinary pH of 7,0 confirming renal tubular acidosis (RTA). We identified topiramate, our patient's medication for migraine, as the cause of the RTA. Topiramate, a carboanhydrase inhibitor leads to RTA of a mixed (proximal and distal) type and thus significantly increases the risk for kidney stones.

Distal renal tubular acidosis that became exacerbated by proton pump inhibitor use

Acid-base imbalances and electrolyte disorders induced by proton pump inhibitors (PPIs) are extremely rare. However, under certain conditions, PPIs may cause metabolic acidosis or hypokalemia, probably due to an inhibitory action on the proton pump that contributes to H(+) and K(+) homeostasis in the kidney. We herein present a case of marked hypokalemia accompanied by distal renal tubular acidosis in which a PPI appeared to contribute to the pathophysiology of metabolic acidosis.

Pharmacologically-induced metabolic acidosis: a review

Metabolic acidosis may occasionally develop in the course of treatment with drugs used in everyday clinical practice, as well as with the exposure to certain chemicals. Drug-induced metabolic acidosis, although usually mild, may well be life-threatening, as in cases of lactic acidosis complicating antiretroviral therapy or treatment with biguanides. Therefore, a detailed medical history, with special attention to the recent use of culprit medications, is essential in patients with acid-base derangements. Effective clinical management can be handled through awareness of the adverse effect of certain pharmaceutical compounds on the acid-base status. In this review, we evaluate relevant literature with regard to metabolic acidosis associated with specific drug treatment, and discuss the clinical setting and underlying pathophysiological mechanisms. These mechanisms involve renal inability to excrete the dietary H+ load (including types I and IV renal tubular acidoses), metabolic acidosis owing to increased H+ load (including lactic acidosis, ketoacidosis, ingestion of various substances, administration of hyperalimentation solutions and massive rhabdomyolysis) and metabolic acidosis due to HCO3- loss (including gastrointestinal loss and type II renal tubular acidosis). Determinations of arterial blood gases, the serum anion gap and, in some circumstances, the serum osmolar gap are helpful in delineating the pathogenesis of the acid-base disorder. In all cases of drug-related metabolic acidosis, discontinuation of the culprit medications and avoidance of readministration is advised.

Pemetrexed-induced acute renal failure, nephrogenic diabetes insipidus, and renal tubular acidosis in a patient with non-small cell lung cancer

We report a patient with metastatic non-small cell lung cancer who developed renal toxicities manifest as acute renal failure associated with nephrogenic diabetes insipidus and distal renal tubular acidosis following sequential therapy with pemetrexed. The nephrotoxicity occurred concomitantly with severe myelosuppression. We postulate renal tubular toxicity may account for distinct patterns of injury including acute renal failure and tubular cell dysfunction of the distal nephron.

Effect of topiramate on acid-base balance: extent, mechanism and effects

Topiramate is licensed for the treatment of epilepsy and for migraine prophylaxis, but is also used off-licence for a wide range of indications. With the increasing use of topiramate, reports have emerged that topiramate can cause metabolic acidosis in some patients. It does this by impairing both the normal reabsorption of filtered HCO(3)(-) by the proximal renal tubule and the excretion of H(+) by the distal renal tubule. This combination of defects is termed mixed renal tubular acidosis (RTA). The mechanism involves the inhibition of the enzyme carbonic anhydrase, which is consistent with the fact that genetic deficiency of carbonic anhydrase is associated with mixed RTA. Topiramate-induced RTA can make patients acutely ill, and chronically, can lead to nephrolithiasis, osteoporosis and, in children, growth retardation. There is no proven method for predicting or preventing the effect of topiramate on acid-base balance, but patients with a history of renal calculi or known RTA should not receive topiramate. The utility of regular monitoring of HCO(3)(-) levels has not been proven and is not routine practice currently. For patients with persistent RTA, topiramate should usually be discontinued as alternative agents are available.

5-Oxoproline as a cause of high anion gap metabolic acidosis: an uncommon cause with common risk factors

High anion gap metabolic acidosis might be caused by 5-oxoproline (pyroglutamic acid). As it is very easy to treat, it might be worth drawing attention to this uncommon and probably often overlooked diagnosis. We present three cases of high anion gap metabolic acidosis due to 5-oxoproline seen within a period of six months.

Induction of Anti-Carbonic-Anhydrase-II Antibody Causes Renal Tubular Acidosis in a Mouse Model of Sjögren’s Syndrome

BACKGROUND/AIM

We recently reported that renal tubular acidosis (RTA) in Sjogren's syndrome (SjS) is associated with high titers of an autoantibody against carbonic anhydrase (CA) II, an important enzyme in renal acid-base regulation. The purpose of this study was to determine whether a CA-II antibody could cause RTA in a mouse model of SjS.

METHODS

PL/J mice were immunized with human CA II to induce CA II antibody formation, whereas controls were injected with phosphate-buffered saline and adjuvant. After 6 weeks, anti-CA-II antibody titers were measured, then ammonium chloride was administered orally for 1 week to detect any acidification defect.

RESULTS

CA-II-immunized mice showed higher anti-CA-II antibody titers than control mice. Pathologically, lymphocytic and plasma cell infiltration was seen in the salivary glands and kidneys of CA-II-immunized mice, but not in controls. On acid loading, blood pH and urine pH decreased in both groups of mice, but the slope of urine pH versus blood pH was less steep in the CA-II-immunized mice, suggesting that these mice had an impaired ability to reduce their urine pH in the face of metabolic acidosis.

CONCLUSION

CA-II-immunized mice had a urinary acidification defect, which may be similar to that seen in patients with SjS.

Combined renal tubular acidosis and diabetes insipidus in hematological disease

BACKGROUND

A 39-year-old male with multiple myeloma was admitted for treatment with melphalan and autologous stem cell reinfusion. He presented with hypokalemia and hyperchloremic non-anion-gap metabolic acidosis with a high urinary pH. He also had hypomagnesemia, hypophosphatemia, hypouricemia, proteinuria and glucosuria. The patient subsequently developed polyuria with a low urine osmolality, hypernatremia and, finally, acute renal failure.

INVESTIGATIONS

Physical examination, blood and urine analyses, kidney biopsy and tonicity balance.

DIAGNOSIS

Fanconi syndrome with proximal (type II) renal tubular acidosis caused by myeloma kidney. Renal tubular acidosis was complicated by probable nephrogenic diabetes insipidus and acute renal failure.

MANAGEMENT

Potassium supplementation, sodium bicarbonate therapy, intravenous fluid therapy and dialysis.

Dietary protein induces endothelin-mediated kidney injury through enhanced intrinsic acid production

Dietary protein as casein (CAS) augments intrinsic acid production, induces endothelin-mediated kidney acidification, and promotes kidney injury. We tested the hypothesis that dietary CAS induces endothelin-mediated kidney injury through augmented intrinsic acid production. Munich-Wistar rats ate minimum electrolyte diets from age 8 to 96 weeks with 50 or 20% protein as either acid-inducing CAS or non-acid-inducing SOY. Urine net acid excretion and distal nephron net HCO3 reabsorption by in vivo microperfusion (Net J(HCO3)) were higher in 50 than 20% CAS but not 50 and 20% SOY. At 96 weeks, 50% compared the 20% CAS had higher urine endothelin-1 excretion (U(ET-1)V) and a higher index of tubulo-interstitial injury (TII) at pathology (2.25+/-0.21 vs 1.25+/-0.13 U, P<0.03), but each parameter was similar in 50 and 20% SOY. CAS (50%) eating NaHCO3 to reduce intrinsic acid production had lower Net J(HCO3), lower U(ET-1)V, and less TII. By contrast, 50% SOY eating dietary acid as (NH4)2SO4 had higher Net J(HCO3), higher U(ET-1)V, and more TII. Endothelin A/B but not A receptor antagonism reduced Net J(HCO3) in 50% CAS and 50% SOY+(NH4)2SO4 animals. By contrast, endothelin A but not A/B receptor antagonism reduced TII in each group. The data support that increased intake of acid-inducing dietary protein induces endothelin B-receptor-mediated increased Net J(HCO3) and endothelin A-receptor-mediated TII through augmented intrinsic acid production.

Regulation of renal amino acid transporters during metabolic acidosis

The kidney plays a major role in acid-base homeostasis by adapting the excretion of acid equivalents to dietary intake and metabolism. Urinary acid excretion is mediated by the secretion of protons and titratable acids, particularly ammonia. NH(3) is synthesized in proximal tubule cells from glutamine taken up via specific amino acid transporters. We tested whether kidney amino acid transporters are regulated in mice in which metabolic acidosis was induced with NH(4)Cl. Blood gas and urine analysis confirmed metabolic acidosis. Real-time RT-PCR was performed to quantify the mRNAs of 16 amino acid transporters. The mRNA of phosphoenolpyruvate carboxykinase (PEPCK) was quantified as positive control for the regulation and that of GAPDH, as internal standard. In acidosis, the mRNA of kidney system N amino acid transporter SNAT3 (SLC38A3/SN1) showed a strong induction similar to that of PEPCK, whereas all other tested mRNAs encoding glutamine or glutamate transporters were unchanged or reduced in abundance. At the protein level, Western blotting and immunohistochemistry demonstrated an increased abundance of SNAT3 and reduced expression of the basolateral cationic amino acid/neutral amino acid exchanger subunit y(+)-LAT1 (SLC7A7). SNAT3 was localized to the basolateral membrane of the late proximal tubule S3 segment in control animals, whereas its expression was extended to the earlier S2 segment of the proximal tubule during acidosis. Our results suggest that the selective regulation of SNAT3 and y(+)LAT1 expression may serve a major role in the renal adaptation to acid secretion and thus for systemic acid-base balance.

Metabolic acidosis has dual effects on sodium handling by rat kidney

Chronic metabolic acidosis (CMA) is associated with decreased NaCl reabsorption in the proximal tubule (PT). However, the effect of CMA on Na(+) transport in the distal tubule (DT) and collecting duct (CD) is poorly understood. Rats were placed in metabolic cages and had access to water (control), 0.28 M NH(4)Cl, or 0.28 M KCl solutions in a pair-feeding protocol for 5 days (5d). Metabolic acidosis developed within 24 h in NH(4)Cl-, but not in KCl-loaded rats. Interestingly, NH(4)Cl- but not KCl-loaded rats exhibited a significant natriuresis after 24 h of treatment. Urinary Na(+) excretion increased from 1.94 to 2.97 meq/24 h (P < 0.001) and returned to below baseline level (1.67 meq/l) after 5d of CMA. The protein abundance of the cortical Na-Cl cotransporter (NCC) remained unchanged at 24 h, but increased significantly (P < 0.01) after 5d of CMA. The protein abundance of alpha-, beta-, and gamma-subunits of the epithelial Na(+) channel (ENaC) in the cortex decreased sharply during the first 24 h and then returned to baseline levels after 5d of CMA. Interestingly, Sgk1 expression decreased after 24 h (-31%, P < 0.05) and then returned to baseline after 5d of CMA. Nedd4-2 expression was not altered during CMA. CMA enhanced serum aldosterone levels by 54% and increased the expression of aldosterone synthase in the adrenal gland by 134% after 5d of CMA. In conclusion, metabolic acidosis has dual effects on urinary Na(+) excretion. The early natriuresis results from decreased Na(+) reabsorption in the PT and Sgk1-related decreased ENaC activity in the DT and CD. Aldosterone-induced upregulation of NCC, Sgk1, and ENaC likely contributes to the antinatriuretic phase of metabolic acidosis. This adaptation prevents Na(+) wasting and volume depletion during chronic acid insult.

Effects of NH4Cl intake on renal growth in rats: role of MAPK signalling pathway

BACKGROUND

There is a surprising lack of experimental data on the mechanisms of NH4Cl-induced chronic metabolic acidosis which causes kidney hypertrophy. The NH4Cl treatment results in an absolute increase in kidney mass. Despite findings to indicate a close interaction between NH4Cl-induced chronic metabolic acidosis and renal enlargement, the role of the stimulated serine kinase cascade, mediated by the stepwise activation of extracellular signal-regulated kinase (ERK) signalling, on kidney hypertrophy has not yet been investigated.

METHODS

To test this hypothesis, the present study was undertaken to further explore the possible involvement of mitogen-activated protein kinase (MAPK) signalling pathway in renal growth in chronic NH4Cl-treated rats by western blot analysis.

RESULTS

Our major findings are as follows: (1) Urinary sodium excretion significantly increased during the early phases of NH4Cl-induced acidosis, (2) This occurrence is associated with sustained renal hypertrophy, and (3) sustained basal phosphorylation of IRS-1, Shc, and MAPK/ERKs in acidotic kidneys.

CONCLUSIONS

The present study confirms that NH4Cl-induced acidosis causes disturbances in renal sodium handling. In addition, these findings demonstrate a sustained pre-stimuli activation of kidney MAPK/ERKs signalling pathways in the NH4Cl-treated rats that may correlate with an increased rate of kidney hypertrophy and a transient renal tubule inability to handle sodium. Thus, the altered renal electrolyte handling may result from a reciprocal relationship between the level of renal tubule metabolic activity and ion transport. In addition, the study shows that the appropriate regulation of tyrosine kinase protein phosphorylation, and its downstream signal transduction pathway, plays an important role on renal growth in the NH4Cl-treated rats.

Renal expression of the ammonia transporters, Rhbg and Rhcg, in response to chronic metabolic acidosis

Chronic metabolic acidosis induces dramatic increases in net acid excretion that are predominantly due to increases in urinary ammonia excretion. The current study examines whether this increase is associated with changes in the expression of the renal ammonia transporter family members, Rh B glycoprotein (Rhbg) and Rh C glycoprotein (Rhcg). Chronic metabolic acidosis was induced in Sprague-Dawley rats by HCl ingestion for 1 wk; control animals were pair-fed. After 1 wk, metabolic acidosis had developed, and urinary ammonia excretion increased significantly. Rhcg protein expression was increased in both the outer medulla and the base of the inner medulla. Intercalated cells in the outer medullary collecting duct (OMCD) and in the inner medullary collecting duct (IMCD) in acid-loaded animals protruded into the tubule lumen and had a sharp, discrete band of apical Rhcg immunoreactivity, compared with a flatter cell profile and a broad band of apical immunolabel in control kidneys. In addition, basolateral Rhcg immunoreactivity was observed in both control and acidotic kidneys. Cortical Rhcg protein expression and immunoreactivity were not detectably altered. Rhcg mRNA expression was not significantly altered in the cortex, outer medulla, or inner medulla by chronic metabolic acidosis. Rhbg protein and mRNA expression were unchanged in the cortex, outer and inner medulla, and no changes in Rhbg immunolabel were evident in these regions. We conclude that chronic metabolic acidosis increases Rhcg protein expression in intercalated cells in the OMCD and in the IMCD, where it is likely to mediate an important role in the increased urinary ammonia excretion.

Topiramate and severe metabolic acidosis: case report

Topiramate infrequently induces anion gap metabolic acidosis through carbonic anhydrase inhibition on the distal tubule of the nephron - a type 2 renal tubular acidosis. We report on a 40 years old woman previously healthy that developed significant asymptomatic metabolic acidosis during topiramate therapy at a dosage of 100mg/day for three months. Stopping medication was followed by normalization of the acid-base status within five weeks. This infrequent side effect appears unpredictable and should be given careful attention.

Antiviral Drug-Induced Nephrotoxicity

Drug-induced kidney injury is a major side effect in clinical practice, frequently leading to acute renal failure (ARF). It accounts for more than 2% to 15% of cases of ARF in patients admitted to the hospital or in the intensive care unit, respectively. The exact frequency of nephrotoxicity induced by antiviral drugs is difficult to determine. Antiviral drugs cause renal failure through a variety of mechanisms. Direct renal tubular toxicity has been described with a number of new medications with unique effects on epithelial cells of the kidney. These include cidofovir, adefovir dipivoxil, and tenofovir, as well as acyclovir. Additionally, crystal deposition in the kidney may promote the development of renal failure. Several different drugs have been described to induce crystal nephropathy, including acyclovir and the protease inhibitor indinavir. Renal injury associated with antiviral drugs involves diverse processes having effects on the renal transporters, as well as on tubule cells. In this article, we review the pathogenesis of antiviral drug-induced kidney injury, common nephrotoxic renal syndromes, and strategies for preventing kidney injury.

Renal tubular acidosis and severe hypophosphataemia due to toluene inhalation

A 21-year-old woman developed severe muscle paralysis after sniffing toluene-containing thinner solution for 2 weeks. Her serum chemistries revealed severe hypokalaemia and a normal anion gap hyperchloraemic metabolic acidosis secondary to renal tubular acidosis. Her initial presentation mimicked hypokalaemic periodic paralysis, but toxicology screening of her blood and urine revealed the correct diagnosis of toluene poisoning. Her electrolyte and acid-base status returned to normal 4 days after cessation of toluene sniffing. On another occasion, apart from renal tubular acidosis, the patient also developed severe hypophosphataemia with the phosphate level decreasing to 0.15 mmol/L. Hypophosphataemia with such a low phosphate level after toluene poisoning has been rarely reported in the literature. Toluene inhalation can result in multiple electrolyte and acid-base abnormalities, and should be considered in the diagnosis of any young patient who presents with unexplained hypokalaemia and normal anion gap metabolic acidosis.

Cyclosporin A produces distal renal tubular acidosis by blocking peptidyl prolyl cis-trans isomerase activity of cyclophilin

Cyclosporin A (CsA), a widely used immunosuppressant, causes distal renal tubular acidosis (dRTA). It exerts its immunosuppressive effect by a calcineurin-inhibitory complex with its cytosolic receptor, cyclophilin A. However, CsA also inhibits the peptidyl prolyl cis-trans isomerase (PPIase) activity of cyclophilin A. We studied HCO(3)(-) transport and changes in beta-intercalated cell pH on luminal Cl(-) removal in isolated, perfused rabbit cortical collecting tubules (CCDs) before and after exposure to media pH 6.8 for 3 h. Acid incubation causes adaptive changes in beta-intercalated cells by extracellular deposition of hensin (J Clin Invest 109: 89, 2002). Here, CsA prevented this adaptation. The unidirectional HCO(3)(-) secretory flux, estimated as the difference between net flux and that after Cl(-) removal from the lumen, was -6.7 +/- 0.2 pmol.min(-1).mm(-1) and decreased to -1.3 +/- 0.2 after acid incubation. CsA in the bath prevented the adaptive decreases in HCO(3)(-) secretion and apical Cl(-):HCO(3)(-) exchange. To determine the mechanism, we incubated CCDs with FK-506, which inhibits calcineurin activity independently of the host cell cyclophilin. FK-506 did not prevent the acid-induced adaptive decrease in unidirectional HCO(3)(-) secretion. However, [AD-Ser](8) CsA, a CsA derivative, which does not inhibit calcineurin but inhibits PPIase activity of cyclophilin A, completely blocked the effect of acid incubation on apical Cl(-):HCO(3)(-) exchange. Acid incubation resulted in prominent "clumpy" staining of extracellular hensin and diminished apical surface of beta-intercalated cells [smaller peanut agglutinin (PNA) caps]. CsA and [AD-Ser](8) CsA prevented most hensin staining and the reduction of apical surface; PNA caps were more prominent. We suggest that hensin polymerization around adapting beta-intercalated cells requires the PPIase activity of cyclophilins. Thus CsA is able to prevent this adaptation by inhibition of a peptidyl prolyl cis-trans isomerase activity. Such inhibition may cause dRTA during acid loading.

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.

Possible association between cell membrane band 3 impairment function and renal tubular acidosis (liver diseases, malignancies and adverse drug reactions)

Renal tubular acidosis (RTA) more frequently develops in case of chronic diseases of inflammatory-immunological origin. RTA is well known to be associated with chronic liver disease (CLD), with nephrolithiasis, common cases of RTA occur among cancer patients. Abnormalities in the expression or function of band 3 in cell membrane may play a role in the pathogenesis of RTA. Cl-/HCO3- anion exchanger (AE2) is an isoform of band 3 protein, which is expressed in cell membranes of organs such as liver cells and kidney endothelium. There are reports on downregulated AE2 immunoreactivity in the liver of patients with chronic liver diseases and in the kidney tubular tissue of patients with RTA. The proteolytic damage of cell membrane band 3 in tissues could be related to inflammatory-immunological processes. Another important factor able to disturb the band 3 function is medicinal products used in the treatment of certain pathologies. The active substance of a drug itself may have a direct effect on this protein or trigger a pathological process. In such cases ADR can take place and may be evaluated as such. Acid-base disturbances, notably metabolic acidosis, are a serious complication of drug treatment. Reduced AE2 expression or its changed activity (congenital or acquired) could be related with alterations of intracellular pH. This could lead to antigenic changes and autoimmunity. The derangement of band 3 function in organ cell membrane could act as a factor which creates an "acidotic environment" for organ cells. Such circumstances could be the reason for unsuccessful treatment or determine resistance of tumor treatment. The understanding of the mechanisms of RTA development, early diagnostics, and knowledge of the drugs that can cause RTA, are of particular practical significance.

Renal Tubular Acidosis Secondary to FK506 in Living Donor Liver Transplantation: A Case Report

FK506 is an immunosuppressant that is thought to be less nephrotoxic than cyclosporine A. However, complications due to renal tubular acidosis (RTA) have recently been reported. We report a case of RTA secondary to FK506 administration in liver transplantation. A 6-month-old girl was treated with FK506 after undergoing living donor liver transplantation for fulminant hepatitis. On postoperative day 17, she demonstrated hyperkalaemia and metabolic acidosis; she was diagnosed to have hyperkalaemic distal RTA with aldosterone deficiency (type IV). Intravenous sodium bicarbonate and furosemide, and intrarectal calcium polystyrenesulfonate were administered to correct the acidosis and promote potassium secretion. Thereafter, the FK506 concentration in whole blood gradually decreased, and the hyperkalaemia and metabolic acidosis following RTA improved. RTA is one type of nephrotoxicity induced by FK506, and it is reversible in mild cases when appropriately treated. The mechanism of RTA induced by FK506 has not yet been clearly elucidated. Surgeons and physicians should therefore be aware of the potential for RTA to occur with FK506 after any organ transplantation. The treatment for acidosis and hyperkalaemia should be started as soon as RTA is diagnosed, and the dosage of FK506 should also be reduced if possible.

Severe hypokalaemia and weakness due to Nurofen misuse

Nephrotoxicity from non-steroidal anti-inflammatory drugs (NSAID) is well recognized. We report a case of severe hypokalaemia and weakness due to renal tubular acidosis in a young woman who was taking 40-60 tablets per day of Nurofen Plus (ibuprofen 200 mg and codeine phosphate 12.8 mg). Proprietary brands of ibuprofen are freely available to the public and those containing codeine may be potentially subject to abuse. This case highlights the need to be aware of this potential and of the life-threatening electrolyte and acid-base disturbances that might be encountered with the widespread availability of these types of NSAID.

Nitric oxide production modulates cyclosporin A-induced distal renal tubular acidosis in the rat

Cyclosporine A (CsA) causes distal renal tubular acidosis (dRTA) in humans and rodents. Because mice deficient in nitric-oxide (NO) synthase develop acidosis, we examined how NO production modulated H+ excretion during acid loading and CsA treatment in a rat model. Rats received CsA, L-arginine (L-Arg), or N omega-nitro-L-arginine methyl ester (L-NAME), or combinations of CsA and L-NAME or L-Arg, followed by NH4Cl (acute acid load). In vehicle-treated rats, NH4Cl loading reduced serum and urine (HCO3-) and urine pH, which was associated with increases in serum [K+] and [Cl-] and urine NH3 excretion. Similar to CsA (7.5 mg/kg), L-NAME impaired H+ excretion of NH4Cl-loaded animals. The combination CsA and L-NAME reduced H+ excretion to a larger extent than either drug alone. In contrast, administration of L-Arg ameliorated the effect of CsA on H+ excretion. Urine pH after NH4Cl was 5.80 +/- 0.09, 6.11 +/- 0.13*, 6.37 +/- 0.16*, and 5.77 +/- 0.09 in the vehicle, CsA, CsA + L-NAME and CsA + L-Arg groups, respectively (*P < 0.05). The effect of CsA and alteration of NO synthesis were mediated at least in part by changes in bicarbonate absorption in perfused cortical collecting ducts. CsA or L-NAME reduced net HCO3- absorption, and, when combined, completely inhibited it. CsA + L-Arg restored HCO3- absorption to near control levels. Administration of CsA along with L-NAME reduced NO production to below levels observed with either drug alone. These results suggest that CsA causes dRTA by inhibiting H+ pumps in the distal nephron. Inhibition of NO synthesis may be one of the mechanisms underlying the CsA effect.

The application of immunohistochemical findings in the diagnosis in methamphetamine-related death-two forensic autopsy cases-

Forensic autopsy cases detecting methamphetamine (MA) are usually diagnosed according to its toxicological concentration. It has been reported that the lethal blood concentration of MA is 4.48 microg/ml (3.0 micromol/dl). We autopsied two MA-detected cadavers, and immunohistochemical staining was performed on the skeletal muscle with an anti-myoglobin antibody, and on the kidney with an anti-the 70 kDa heat shock protein (HSP70) antibody. One case showed a high rectal temperature (40 degrees C). The toxicological examination revealed 0.75 microg/ml of MA in the blood, and 16.8 microg/ml in the urine. Myoglobin was negative and HSP70 was positive in the kidney immunohistochemically. From the toxicological and immunohistochemical findings, it was considered that the subject died of hyperthermia and acidosis caused by muscular hyperactivity. In another case, the autopsy revealed highly congested lungs, with dark-red bloody fluid and foam in the trachea and bronchus. MA (17.0 microg/ml) was detected in the blood. HSP70 was negative and myoglobin was positive immunohistochemically. It was thought that the subject died of acute MA intoxication based on the high MA concentration, although rhabdomyolysis was suspected. It is suggested that myoglobin and HSP70 immunostaining are useful to diagnose MA poisoning.

Renal and systemic pH imaging by contrast-enhanced MRI

Perturbations of renal and systemic pH accompany diseases of the kidney, such as renal tubular acidosis, and the ability to image tissue pH would be helpful to assess the extent and severity of such conditions. A dual-contrast-agent strategy using two gadolinium agents, the pH-insensitive GdDOTP(5-) and the pH-sensitive GdDOTA-4AmP(5-), has been developed to generate pH maps by MRI. The renal pharmacokinetics of the structurally dissimilar pH-insensitive contrast agents GdDTPA(2-) and GdDOTP(5-) were found to be similar. On that basis, and on the basis of similarity of structure and charge, the renal pharmacokinetics of GdDOTP(5-) and GdDOTA-4AmP(5-) were assumed to be identical. Dynamic T(1)-weighted images of mice were acquired for 1 hr each following boluses of GdDOTP(5-) and GdDOTA-4AmP(5-). The time-varying apparent concentration of GdDOTP(5-) and the time-varying enhancement in longitudinal relaxation rate following GdDOTA-4AmP(5-) were calculated for each pixel and used to compute pH images of the kidneys and surrounding tissues. MRI pH maps of control mice show acidic regions corresponding to the renal papilla, calyx, and ureter. Pretreatment of mice with the carbonic anhydrase inhibitor acetazolamide resulted in systemic metabolic acidosis and accompanying urine alkalinization that was readily detected by this dual-contrast-agent approach.

Solvent abuse in pregnancy: a perinatal perspective

OBJECTIVE

To review the scope and sequelae of solvent abuse in women presenting to a Manitoba teaching hospital.

METHODS

Fifty-six patient charts with a diagnosis of solvent abuse in pregnancy were identified through computer search in the medical records of Winnipeg Health Sciences Centre, General Hospital. These charts were reviewed and data obtained from birthing records and associated pediatric charts.

RESULTS

Renal tubular acidosis was diagnosed in three patients (5.3%). Two patients (3.6%) had adverse neurological sequelae. One patient was diagnosed with brain damage, including expressive aphasia. Twelve patients (21.4%) delivered preterm infants. Nine infants (16.1%) had major anomalies. Seven infants (12.5%) had fetal alcohol syndrome (FAS)-like facial features. Six neonates (10.7%) had hearing loss.

CONCLUSION

Substance abuse in pregnancy is associated with severe maternal and neonatal sequelae. Physicians must be aware of this increasing problem in the obstetrical population and assistance should be offered to each woman, ideally before a woman becomes pregnant, but at least at the first contact a pregnant woman makes with the health care community.

Life threatening hyperkalemia and acidosis secondary to trimethoprim-sulfamethoxazole treatment

We present a 77-year-old male with moderate chronic renal insufficiency from diabetic nephropathy who developed severe metabolic acidosis and life threatening hyperkalemia on treatment with regular dose of trimethoprim-sulfamethoxazole (TMP-SMZ) for urinary tract infection. The metabolic acidosis and hyperkalemia resolved upon appropriate medical intervention and discontinuation of TMP-SMZ. While hyperkalemia has commonly been reported with high dose of TMP-SMZ, severe metabolic acidosis is quite uncommon with regular dose TMP-SMZ. We emphasize that patients with renal tubular acidosis (RTA), renal insufficiency, aldosterone deficiency, old age with reduced renal mass and function, and angiotensin converting enzyme (ACE)-inhibitor therapy are at high risk of developing these severe and potentially life threatening complications.

Transient renal tubular acidosis in a neonate following transplacental acetazolamide

Renal tubular acidosis (RTA) was observed in a preterm boy shortly after birth. His mother had glaucoma and had been treated during pregnancy with oral acetazolamide, a carbonic anhydrase inhibitor. When RTA developed, acetazolamide was detected in his serum demonstrating transplacental acetazolamide passage.

Hypokalemic muscular paralysis causing acute respiratory failure due to rhabdomyolysis with renal tubular acidosis in a chronic glue sniffer

CASE REPORT

A 34-year-old male was admitted to the emergency department with the development of quadriparesis and respiratory failure due to hypokalemia after prolonged glue sniffing. The patient was subsequently given mechanical ventilatory support for respiratory failure. He was weaned from the ventilator 4 days later after potassium replacement. Toluene is an aromatic hydrocarbon found in glues, cements, and solvents. It is known to be toxic to the nervous system, hematopoietic system, and causes acid-base and electrolyte disorders. Acute respiratory failure with hypokalemia and rhabdomyolysis with acute renal failure should be considered as potential events in a protracted glue sniffing.

Renal tubular acidosis associated with zonisamide therapy

PURPOSE

We sought to report a previously undescribed adverse effect, renal tubular acidosis associated with zonisamide (ZNS) therapy.

METHODS

Ammonium chloride, bicarbonate, and furosemide loading tests were performed in an epileptic patient with metabolic acidosis and episodic hypokalemia who was treated with ZNS.

RESULTS

Distal renal tubular acidosis was diagnosed. On reexamination 7 weeks after ZNS had been replaced with phenytoin, the renal tubular acidosis disappeared.

CONCLUSIONS

This case indicates, for the first time, that ZNS might be a potential cause of renal tubular acidosis. Blood gases and serum electrolytes should be measured in patients undergoing ZNS therapy.