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This article discusses the pathophysiology, causes, diagnosis, treatment, and prognosis of renal tubular acidosis (RTA) in veterinary patients. RTA is classified as a non-anion-gap metabolic acidosis in the presence of a normal glomerular filtration rate. Proximal RTA occurs because of a deficiency in bicarbonate resorption in the proximal tubule, whereas distal RTA occurs because of decreased production of bicarbonate in the distal tubule. RTA can be transient or permanent and can occur secondary to other diseases. Therapy includes bicarbonate supplementation with careful acid-base and electrolyte monitoring and treatment of underlying causes. There are few published discussions of renal tubular acidosis (RTA) in the veterinary literature despite the abundance of reports of such disorders in humans. Although it is possible that the incidence of such conditions in small animals is less than that in humans, it is also plausible that tubular disorders are overlooked in veterinary patients (Table 1). RTA typically causes metabolic acidosis with both a normal anion gap and normal glomerular filtration rate (GFR). In contrast, renal failure is often associated with an increased anion gap due to the presence of phosphates, sulfates, and organic anions as well as a reduced GFR. Traditionally, RTA has been classified into four types in human medicine: type 1 (i.e., distal tubular acidosis), type 2 (i.e., proximal tubular acidosis), type 3 (i.e., an ill-defined combination of proximal and distal tubular acidosis), and type 4 (i.e., hyperkalemic RTA). Type 3 RTA is an obsolete term because it is no longer considered a distinct form of RTA. Type 4 RTA is associated with hyperkalemia and decreased renin and aldosterone concentrations. In humans, this is most commonly recognized in Continue reading >>
Renal Tubular Acidosis
Each time our internal organs do something, such as digesting food or healing damaged tissue, chemical reactions take place in the body's cells. These reactions cause acid to go into the bloodstream. Normally, the kidneys remove excess acid from blood, but certain diseases, genetic defects, or drugs can damage a kidney's ability to do this important job. This can allow too much acid to build up in the blood and cause problems. When this happens, it's called renal tubular acidosis (RTA). Without treatment, RTA can affect a child's growth and cause kidney stones , fatigue, muscle weakness, and other symptoms. Over time, untreated acidosis can lead to long-term problems like bone disease, kidney disease , and kidney failure. Fortunately, such complications are rare, since most cases of RTA can be effectively treated with medicines or by treating the condition that's causing the acid to build up. The kidneys are a pair of bean-shaped organs located toward the back of the abdominal cavity, just above the waist. The kidneys remove waste products and extra water from the food a person eats, returning chemicals the body needs (such as sodium, phosphorus, and potassium) back into the bloodstream. The extra water combines with other waste to become urine (pee). The main functional units of the kidneys, where the blood filtering happens, are tiny structures called nephrons. Each kidney has about a million nephrons, and each nephron has a renal tubule, a tube where the acid and waste products filtered from the blood are secreted into urine. Having a disease or defect can interfere with how the renal tubules function, which can lead to RTA. There are a few different kinds of RTA. The first two types are named for the part of the renal tubule in which the damage or defect is found. Continue reading >>
8.5 Renal Tubular Acidosis
Renal Tubular Acidosis (RTA) is a syndrome due to either a defect in proximal tubule bicarbonate reabsorption, or a defect in distal tubule hydrogen ion secretion, or both. This results in a hyperchloraemic metabolic acidosis with normal to moderately decreased GFR. Anion gap is normal. A typical situation where RTA would be suspected is if urine pH is greater than 7.0 despite the presence of a metabolic acidosis. In contrast, the acidosis that occurs with acute, chronic, or acute on chronic renal failure is a high anion gap metabolic acidosis. As a general overview to help understand why renal disease can give different types of acidosis consider the following:Acidosis due to renal disease is considered in 2 categories depending on whether the predominant site of renal damage is in the glomeruli or in the tubules. Renal tubular acidosis is a form of hyperchloraemic metabolic acidosis which occurs when the renal damage primarily affects tubular function without much effect on glomerular function. The result is a decrease in H+ excretion which is greater than can be explained by any change in GFR. In contrast, if glomerular function (ie GFR) is significantly depressed (hence 'renal failure'), the retention of fixed acids results in a high anion gap acidosis. Predominantly tubular damage ---> Normal anion gap acidosis (Renal tubular acidosis - RTA) Predominantly glomerular damage ---> High anion gap acidosis Three main clinical categories or 'types' of renal tubular acidosis (RTA) are now recognised but the number of possible causes is large. The mechanism causing the defect in ability to acidify the urine and excrete acid is different in the three types. 1,2 8.5.2 Distal (Type 1) Renal Tubular Acidosis This is also referred to as classic RTA or distal RTA. The problem h Continue reading >>
Renal Tubular Acidosis (rta)
By L. Aimee Hechanova, MD, Assistant Professor of Medicine, Texas Tech University; Attending Nephrologist, University Medical Center (See also Introduction to Disorders of Kidney Tubules .) In renal tubular acidosis, the kidney tubules malfunction, resulting in excess levels of acid in the blood. The tubules of the kidneys that remove acid from the blood are damaged when a person takes certain drugs or has another disorder that affects the kidneys. Often muscle weakness and diminished reflexes occur when the disorder has been present for a long time. Blood tests show high acid levels and a disturbance of the body's acid-base balance. Some people drink a solution of baking soda every day to neutralize the acid. To function normally, body acids and alkali (such as bicarbonate) must be balanced. Normally, the breakdown of food produces acids that circulate in the blood. The kidneys remove acids from the blood and excrete them in the urine. This function is predominantly carried out by the kidney tubules . In renal tubular acidosis, the kidney tubules malfunction in one of two ways that tend to increase acids in the blood ( metabolic acidosis ): Too little of the acids the body produces are excreted, so acid levels in blood increase. Too little of the bicarbonate that filters through the kidney tubules is reabsorbed, so too much bicarbonate is lost in the urine. In renal tubular acidosis, the balance of electrolytes is also affected. Renal tubular acidosis may lead to the following problems: Low or high potassium levels in the blood Calcium deposits in the kidneys, which may lead to kidney stones Painful softening and bending of the bones (osteomalacia or rickets ) Renal tubular acidosis may be a permanent, inherited disorder in children. However, it may be an intermittent Continue reading >>
Renal Tubular Acidosis (rta)
Renal tubular acidosis (RTA)refers to anormal anion gap metabolic acidosis (also known as a hyperchloremic acidosis) caused by: decreased excretion of hydrogen ions and/or decreased reabsorption of sodium bicarbonate in the renal tubules The abnormal acid-base transport within the tubules cannot be solely explained by decreased a glomerular filtration rate (GFR) secondary to chronic kidney disease, obstructive uropathy, or some other non-specific nephropathic mechanism The precise pathophysiological mechanism underlying the disorder varies across RTA sub-types (I-IV), which are described in detail below. Normal Acid-Base Homeostasis within the Renal Tubules Acid-base handling in the renal tubule can be broken down into two stages: Proximal reabsorption of filtered bicarbonate Proximal Reabsorption of BicarbonateSoriano JR. Renal Tubular Acidosis: The Clinical Entity. JASN. 2002 The reabsorption of filtered bicarbonate in the proximal tubule depends on the activity of carbonic anhydrase and several transporters: Intracellular carbonic anhydrase (CA-II) creates carbonic acid from water and carbon dioxide, which in turn ionizes to form a hydrogen ion plus bicarbonate The newly created bicarbonate is passively transported into the blood along with sodium by the co-transporter NBC-1 The newly created hydrogen ion is excreted into the tubule by NHE-3, which is driven by the anti-transport of sodium (down its concentration gradient) Intraluminal carbonic anhydrase (CA-IV) combines the intraluminal bicarbonate and hydrogen ion into water and CO2, the latter of which diffuses back into the cell (and is used as substrate for CA-II), thus driving a net absorption of bicarbonate Distal Acidification of UrineSoriano JR. Renal Tubular Acidosis: The Clinical Entity. JASN. 2002 The ac Continue reading >>
Renal Tubular Acidosis Key Highlights - Epocrates Online
Patients with renal tubular acidosis (RTA) are often asymptomatic but may present with complaints of muscular weakness related to associated hypokalemia. Patients with severe acidemia can show hyperventilation or Kussmaul breathing due to respiratory compensation. Patients with RTA have a low arterial pH and serum bicarbonate with hyperchloremia and a normal serum anion gap. The urine pH exceeds 5.5 in classic distal RTA, but is lower than 5.0 in patients with untreated proximal RTA and is low also in hyperkalemic distal RTA. Alkali therapy is the mainstay of treatment. Potassium supplementation may be required for hypokalemia, and low-potassium diets are used if hyperkalemia is present. If hyperkalemic distal RTA is due to mineralocorticoid deficiency, fludrocortisone can be given unless it is contraindicated due to the presence of fluid overload or uncontrolled hypertension. Proximal RTA occurs most often as a component of Fanconi syndrome, which is characterized by generalized dysfunction of the proximal tubule, with the resultant urinary loss of bicarbonate, calcium, phosphate, urate, amino acids, glucose, and other organic acids and bases. In children, Fanconi syndrome causes growth retardation, renal rickets, and severe metabolic acidosis. Adult cases exhibit similar urinary losses, but the clinical impact is largely restricted to metabolic acidosis. Fanconi syndrome is marked by the appearance in the urine of all amino acids. Specific amino aciduria as seen in isolated cystinuria, glucose loss in isolated glycosuria, and isolated phosphaturia do not constitute Fanconi syndrome. osteopenia, osteopetrosis, nephrocalcinosis, and cerebral calcifications measurement of fractional bicarbonate excretion tubular maximum (Tm) reabsorption of phosphate sodium alkali or po Continue reading >>
Renal Tubular Acidosis
Patients with renal tubular acidosis (RTA) are often asymptomatic but may present with complaints of muscular weakness related to associated hypokalemia. Patients with severe acidemia can show hyperventilation or Kussmaul breathing due to respiratory compensation. Patients with RTA have a low arterial pH and serum bicarbonate with hyperchloremia and a normal serum anion gap. The urine pH exceeds 5.5 in classic distal RTA, but is lower than 5.0 in patients with untreated proximal RTA and is low also in hyperkalemic distal RTA. Alkali therapy is the mainstay of treatment. Potassium supplementation may be required for hypokalemia, and low-potassium diets are used if hyperkalemia is present. If hyperkalemic distal RTA is due to mineralocorticoid deficiency, fludrocortisone can be given unless it is contraindicated due to the presence of fluid overload or uncontrolled hypertension. Proximal RTA occurs most often as a component of Fanconi syndrome, which is characterized by generalized dysfunction of the proximal tubule, with the resultant urinary loss of bicarbonate, calcium, phosphate, urate, amino acids, glucose, and other organic acids and bases. In children, Fanconi syndrome causes growth retardation, renal rickets, and severe metabolic acidosis. Adult cases exhibit similar urinary losses, but the clinical impact is largely restricted to metabolic acidosis. Fanconi syndrome is marked by the appearance in the urine of all amino acids. Specific amino aciduria as seen in isolated cystinuria, glucose loss in isolated glycosuria, and isolated phosphaturia do not constitute Fanconi syndrome. The term renal tubular acidosis (RTA) describes any one of a number of disorders, in which the excretion of fixed acid (distal RTA) or the reabsorption of filtered bicarbonate (proximal R Continue reading >>
Proximal Renal Tubular Acidosis
Renal tubular acidosis - proximal; Type II RTA; RTA - proximal; Renal tubular acidosis type II Proximal renal tubular acidosis is a disease that occurs when the kidneys don't properly remove acids from the blood into the urine. As a result, too much acid remains in the blood (called acidosis ). The kidneys are responsible for removing wastes from the body, regulating electrolyte balance and blood pressure, and the stimulation of red blood cell production. This is the typical appearance of the blood vessels (vasculature) and urine flow pattern in the kidney. The blood vessels are shown in red and the urine flow pattern in yellow. When the body performs its normal functions, it produces acid. If this acid is not removed or neutralized, the blood will become too acidic. This can lead to electrolyte imbalances in the blood. It can also cause problems with normal function of some cells. The kidneys help control the body's acid level by removing acid from the blood and excreting it into the urine. Acidic substances in the body are neutralized by alkaline substances, mainly bicarbonate. Proximal renal tubular acidosis (Type II RTA) occurs when bicarbonate is not properly reabsorbed by the kidney's filtering system. Type II RTA is less common than Type I RTA. Type I is also called distal renal tubular acidosis . Type II most often occurs during infancy and may go away by itself. Cystinosis (body is unable to break down the substance cysteine) Drugs such as ifosfamide (a chemotherapy drug), certain antibiotics that are no longer used much (tetracycline), or acetazolamide Fanconi syndrome , a disorder of the kidney tubes in which certain substances normally absorbed into the bloodstream by the kidneys are released into the urine instead Inherited fructose intolerance , a disorde Continue reading >>
Kidney Tubular Acidosis
Kidney tubular acidosisalso called renal tubular acidosis (RTA)is a condition that occurs when the kidneys do not properly filter acids from the blood into the urine causing the blood to become too acidic. Without treatment and over time, acidity of the blood can lead to one or more of the following: There are four types of renal tubular acidosis: Type 1. Type 1 renal tubular acidosisalso called distal RTAoccurs relatively far from the beginning of the renal tubule (the part of the kidney where acid and waste products are removed from the blood). A main effect of distal RTA is low blood potassium levels, which can cause extreme weakness, irregular heartbeat, paralysis and, more rarely, death. Type 1 RTA can be inherited or a symptom of: Type 2. Type 2 renal tubular acidosisalso called proximal RTAoccurs closer to the beginning of the renal tubule. This type of RTA occurs more often in infants as part of a disorder called Fanconi syndrome (a disorder in which certain needed minerals are passed into the urine instead of being reabsorbed into the bloodstream). Proximal RTA can also occur as a symptom of some inherited disorders that keep the body from effectively breaking down and using nutrients. Examples of inherited disorders that can lead to proximal RTA include cystinosis (a condition in which the amino acid cystine builds up in the body and damages cells) and Wilson's disease. Type 3. Type 3 renal tubular acidosis is considered to be a combination of Type 1 RTA and Type 2 RTA. Type 4. Type 4 renal tubular acidosisalso called hyperkalemic RTAoccurs when a part of the kidney called the distal tubule fails to move electrolytes from the blood to the urine, causing a buildup of electrolytes in the blood. Hyperkalemic RTA can happen if there is a deficiency of the hormone Continue reading >>
Renal Tubular Acidosis - General Practice Notebook
The whole terminology of renal tubular acidosis can be confusing to the newcomer. Important features to grasp are: The acidosis refers to the plasma, not the contents of the renal tubules. Indeed, in classical (type I) renal tubular acidosis the urine is often alkaline. Thus renal tubular acidosis is a metabolic acidosis of renal tubular origin. There are three main types, named I, II and IV. Type III has become obsolete. The three types have different sites of localisation in the renal tubule. However, again the terminology is confusing in that type II is proximal, type I distal. Home| About us| Facebook| Contact us| Authors| Help| FAQ This site is intended for the use of healthcare professionals only. A licensed medical practitioner should be consulted for diagnosis and treatment of any and all medical conditions. Copyright 2016 Oxbridge Solutions Ltd. Any distribution or duplication of the information contained herein is strictly prohibited. Oxbridge Solutions Ltd receives funding from advertising but maintains editorial independence more... GPnotebook stores small data files on your computer called cookies so that we can recognise you and provide you with the best service. If you do not want to receive cookies please do not use GPnotebook. Continue reading >>
Orphanet: Proximal Renal Tubular Acidosis
Prevalence is unknown but isolated hereditary pRTA is very rare. Drug-induced pRTA occurs relatively frequently. The onset of hereditary pRTA varies from infancy to adulthood, manifesting initially with very alkaline urine due to bicarbonate wastage. Autosomal recessive pRTA (AR pRTA; see this term) is associated with severe growth retardation leading to short stature, intellectual disability and ocular abnormalities such as band keratopathy, cataracts, and glaucoma. Growth retardation and reduced bone density, due to metabolic acidosis, are seen in autosomal dominant pRTA (AD pRTA; see this term). Hypokalemia may be present in some cases of pRTA and can occasionally cause symptoms of hypokalemic periodic paralysis (see this term). Rickets and osteomalacia are common due to vitamin D deficiency and phosphate wasting. In cases where pRTA is associated with primary Fanconi syndrome (see this term), glycosuria, aminoaciduria, phosphaturia, uric acid wastage and tubular proteinuria can occur. Isolated pRTA can be acquired or is inherited either recessively (in most cases) or dominantly. AR pRTA is due to a mutation in the SLC4A4 gene (4q13.3) that encodes the electrogenic sodium bicarbonate cotransporter 1 (kNBC1). AD pRTA is due to mutations in a gene that has not yet been identified. As the proximal tubule reabsorbs around 80% of the filtered load of bicarbonate, a defect in it leads to the loss of bicarbonate. Certain drugs can be responsible for the development of acquired pRTA. Carbonic anhydrase inhibitors cause isolated pRTA while others (including oxaplatin, ifosfamide, adefovir, tenofovir, cidofovir, valproic acid, aminoglycosides, topiramate and didanosine) can all cause pRTA associated with Fanconi syndrome (see this term). In glomerular diseases, pRTA has been Continue reading >>
Renal Tubular Acidosis: The Clinical Entity
Renal Tubular Acidosis: The Clinical Entity Department of Pediatrics, Hospital de Cruces, Vizcaya, Spain. Correspondence to Professor J. Rodrguez-Soriano, Department of Pediatrics, Hospital de Cruces, Plaza de Cruces s/n, Baracaldo, 48903 Vizcaya, Spain. Phone: 34-94-6006357; Fax: 34-94-6006044; E-mail: jsoriano{at}hcru.osakidetza.net The term renal tubular acidosis (RTA) is applied to a group of transport defects in the reabsorption of bicarbonate (HCO3), the excretion of hydrogen ion (H+), or both. This condition was first described in 1935 ( 1 ), confirmed as a renal tubular disorder in 1946 ( 2 ), and designated renal tubular acidosis in 1951 ( 3 ). The RTA syndromes are characterized by a relatively normal GFR and a metabolic acidosis accompanied by hyperchloremia and a normal plasma anion gap. In contrast, the term uremic acidosis is applied to patients with low GFR in whom metabolic acidosis is accompanied by normo- or hypochloremia and an increased plasma anion gap. The renal acid-base homeostasis may be broadly divided into two processes: (1) reabsorption of filtered HCO3, which occurs fundamentally in the proximal convoluted tubule; and (2) excretion of fixed acids through the titration of urinary buffers and the excretion of ammonium, which takes place primarily in the distal nephron. The mechanisms for proximal reabsorption of approximately 80 to 90% of filtered HCO3 are displayed in Figure 1 . The foremost processes occurring in this segment are H+ secretion at the luminal membrane via a specific Na+- H+ exchanger (NHE-3) and HCO3 transport at the basolateral membrane via a Na+- HCO3 cotransporter (NBC-1). In the proximal tubules, carbonic acid (H2CO3) is formed within the cell by the hydration of CO2, a reaction catalyzed by a soluble cytoplasmic carbonic Continue reading >>
Renal Tubular Acidosis And Uraemic Acidosis
Metabolic acidosis can occur in both acute and chronic renal disorders the anion gap may be elevated, due to uraemic acidosis the anion gap may be normal, due to renal tubular acidosis (RTA) Uraemic acidosis results from the loss of functional nephrons decreased glomerular filtration rate (GFR) (e.g. <20 mL/min) accumulation of acidic anions such as phosphate and sulfate occurs causes high anion gap metabolic acidosis (HAGMA) patients manifest as renal failure, often have prolonged survival and develop chronic complications such as bone demineralisation Renal tubular acidosis (RTA) involves defects isolated to the renal tubules only GFR may be normal or only minimally affected primary problem is defective renal acid-base regulation due to impaired ability to acidify the urine and excrete acid results in net acid retention and hyperchloremic normal anion gap metabolic acidosis (NAGMA) may be incomplete and only develop in the presence of an acid load occurs despite a normal or only mildly reduced glomerular filtration rate (GFR) RTA is often detected incidentally through an abnormal blood workup, but some patients present with clinical features such as poor growth, dehydration, or altered mental state COMPARISON OF TYPES OF RENAL TUBULAR ACIDOSIS (RTA) urine pH remains >5.5 despite severe acidaemia (HCO3 < 15mmol/L) HCO3loading test leads to increased urinary HCO3 may require an acid load test to see whether urinary pH remains > 5.5 hyperchloraemic acidosis, alkaline urine, and renal stone formation secondary hyperaldosteronism results in increased K+ loss in urine NaHCO3 (corrects Na+ deficit, ECF volume and corrects hypokalaemia) sodium and potassium citrate solutions can be useful if hypokalaemia persistent citrate also binds Ca2+ in the urine and can help to prevent Continue reading >>
Renal Tubular Acidosis
Renal tubular acidosis (RTA) is acidosis and electrolyte disturbances due to impaired renal hydrogen ion excretion (type 1), impaired bicarbonate resorption (type 2), or abnormal aldosterone production or response (type 4). (Type 3 is extremely rare and is not discussed.) Patients may be asymptomatic, display symptoms and signs of electrolyte derangements, or progress to chronic kidney disease. Diagnosis is based on characteristic changes in urine pH and electrolytes in response to provocative testing. Treatment corrects pH and electrolyte imbalances using alkaline agents, electrolytes, and, rarely, drugs. RTA defines a class of disorders in which excretion of hydrogen ions or reabsorption of filtered bicarbonate is impaired, leading to a chronic metabolic acidosis with a normal anion gap. Hyperchloremia is usually present, and secondary derangements may involve other electrolytes, such as potassium (frequently) and calcium (rarelysee Table: Some Features of Different Types of Renal Tubular Acidosis* ). Chronic RTA is often associated with structural damage to renal tubules and may progress to chronic kidney disease . Some Features of Different Types of Renal Tubular Acidosis* Treatment of concomitant abnormalities related to potassium, calcium, and phosphate metabolism Treatment consists of correction of pH and electrolyte balance with alkali therapy. Failure to treat RTA in children slows growth. Alkaline agents such as sodium bicarbonate, potassium bicarbonate, or sodium citrate help achieve a relatively normal plasma bicarbonate concentration (22 to 24 mEq/L). Potassium citrate can be substituted when persistent hypokalemia is present or, because sodium increases calcium excretion, when calcium calculi are present. Vitamin D (eg, ergocalciferol 800 IU po once/day) Continue reading >>
Omim Entry - 179830 - Renal Tubular Acidosis, Proximal
Proximal RTA is distinct from classic, or distal, RTA (see 179800 ), which is characterized by an inability of the distal tubule to generate a sufficiently large hydrogen ion gradient between blood and tubular fluid. Thus, excretion of ammonium ions and titratable acid are reduced, and urinary pH is usually above 6.5 despite overt acidosis. In the proximal, or bicarbonate-wasting, type of RTA, excretion of acid in the distal tubule is normal, and the urine is normally acidic, with a pH down to 5 during acidosis. In this type of RTA, an inability to reabsorb bicarbonate in the proximal tubules causes hyperchloremic acidosis. Type II RTA is a feature of the Fanconi syndrome (see 134600 ). As an isolated defect, it is a transitory condition in male infants, with growth retardation as the main clinical feature ( Nash et al., 1972 ). Also see proximal renal tubular acidosis with ocular abnormalities and mental retardation ( 604278 ). Brenes et al. (1977) studied a family in which 9 members had hyperchloremic acidosis with normal plasma creatinine and good ability to acidify urine. Renal functions, other than bicarbonate wasting, were normal. The acidosis persisted into adult life. All affected persons were asymptomatic but showed diminished stature. No hypercalciuria, rickets or osteomalacia was found. The authors suggested autosomal dominant inheritance. However, because of no male-to-male transmission, failure of expression in at least 3 persons who by the dominant hypothesis must have had the affected genotype, and the possibility (not excluded by the report) of consanguinity leading to a pseudodominant pedigree pattern, the mode of inheritance cannot be considered certain. Fry and Karet (2007) reviewed the clinical features and molecular genetics of the inherited renal Continue reading >>
