Renal Tubular Acidosis or RTA is a kidney disease in which the kidneys are unable to maintain the acid-base balance in the body. The condition causes increased acidic contents in the blood and decreases excretion of acid molecules in urine. In this article, we will read about the different causes, symptoms, and treatments for Renal Tubular Acidosis.
What Is Renal Tubular Acidosis?
- Renal Tubular Acidosis (RTA) causes accumulation of acidic content in the body
- Increased accumulation of acid in the blood is caused by kidney failure resulting in decreased excretion of acid in urine.
- Acid content in the blood increases because of following reason-
- Kidney is unable to retain alkaline molecules or bicarbonates.
- Kidney retains and is unable to discharge hydrogen molecules or acid content in the urine.
- Renal tubular acidosis causes metabolic acidosis.
- Renal tubular acidosis reduces blood pH resulting in academia.
Types Of Renal Tubular Acidosis
There Are Four Types of Renal Tubular Acidosis:
Type-I Renal Tubular Acidosis (RTA):
- This condition is also called Distal Renal Tubular Acidosis.
- This is one of the most common forms of Renal Tubular Acidosis.
- The disease is caused by reduced hydrogen (acid) molecules excretion in distal tubule and increased excretion of HCO3 (alkaline) molecule.
- The H+ molecule is reabsorbed as acid molecule causing decreased blood pH or acidic pH resulting in metabolic acidosis.
- Type 1 Renal Tubular Acidosis is associated with renal stone.1
- Plasma HCO3 level is less the 15 mEq/L (normal level over 23 mEq/L).
- Plasma K level is low resulting in hypokalemia.1
- This condition is associated with high levels of calcium in the blood
- Renal tubular acidosis is often observed in patients suffering with sickle cell disease, lupus and Sjogren syndrome.
Type-II Renal Tubular Acidosis (RTA):
- This disease is also known as Proximal Renal Tubular Acidosis.
- The defect is in close proximity to the origin of the tubule.
- Disease is caused by defects in proximal tubules, which results in decreased reabsorption of alkaline molecule HCO3.
- The defects causes increased excretion of HCO3, which results in increased blood acidosis.
- Plasma HCO3 level is more than 15 mEq/L
- Plasma K+ level is low resulting in hypokalemia.
- This condition is generally found in infants and has a close relationship with a medical disorder called as Fanconi Syndrome.
- The disease can be caused by Vitamin D deficiency, fructose intolerance, and certain medications like amphotericin B or toluene.2
Type-III Renal Tubular Acidosis:
- This condition is a combination of Type-I and Type-II Renal Tubular Acidosis.
- It is extremely rare and is not used as a classification now
Type-IV Renal Tubular Acidosis:
- This is also called as Hyperkalemic Renal Tubular Acidosis.
- The disease is caused by impaired cation exchange in distal tubule.
- The type 4 RTA is usually caused by a disorder where the cellular exchange of electrolytes such as sodium, potassium, chloride and bicarbonate are abnormal.
- Plasma HCO3 level is higher than 15 mEq/L.
- Plasma K+ is elevated.
- This usually results in abundant potassium retention, which can cause problems for the heart and other vital organs of the body.
- The Type 4 RTA is caused by UTIs, autoimmune dysfunction, sickle cell disease and diabetes.
Causes Of Renal Tubular Acidosis
- Gene Mutation- ATP6V1B1, ATP6V0A4 and SLC4A1 genes mutations were seen in distal renal tubular acidosis.3
- Autoimmune4– Sjogren’s syndrome is known autoimmune disease associated with Renal Tubular Acidosis.5 Other autoimmune disease associated with Renal Tubular Acidosis are SLE and Thyroiditis.
- Primary hyperparathyroidism,6
- Drugs e.g. amphotericin B and toluene inhalation.2
- Toxins- e.g. snake poisons7
Symptoms Of Renal Tubular Acidosis
Some Of The Symptoms Of Renal Tubular Acidosis Are:
- Back pain
- Lower abdominal pain
- Painful urination
- Cloudy urine
- Increased Urinary urgency
- Muscle weakness
- Muscle cramping in the back and abdomen
Diagnosis of Renal Tubular Acidosis
- For a confirmatory diagnosis of Renal Tubular Acidosis, the treating physician does a detailed physical examination and orders a blood test.
- A urinalysis is also done.
- A favorable plan of treatment is made when a diagnosis of Renal Tubular Acidosis is suspected on the tests conducted.
Treatment For Renal Tubular Acidosis
- Discontinue the medication, which may have caused the Renal Tubular Acidosis.
- Treat the autoimmune disease with heavy dosage of corticosteroids or cyclophosphamides.
- Treat primary hyperparathyroidism.
- Another form of treatment for Renal Tubular Acidosis can be alkaline medications to restore acid-base balance in the blood like sodium bicarbonate, which helps to cut down the acidic concentration in the blood.
- Oral bicarbonate supplement- The amount of bicarbonate prescribed is depended on the losses in urine and blood level of bicarbonate as well as correction of acidosis and blood pH
- Thiazide diuretics- Thiazide diuretics retain bicarbonate and helps to correct acidosis.
1. Electrolyte imbalances and nephrocalcinosis in acute phosphate poisoning on chronic type 1 renal tubular acidosis due to Sjögren’s syndrome.
Cho SG1, Yi JH, Han SW, Kim HJ.
J Korean Med Sci. 2013 Feb;28(2):336-9.
2. On the mechanism of toluene-induced renal tubular acidosis.
Batlle DC1, Sabatini S, Kurtzman NA.
3. Mutation analysis and audiologic assessment in six Chinese children with primary distal renal tubular acidosis.
Gao Y1, Xu Y, Li Q, Lang Y, Dong Q, Shao L.
Ren Fail. 2014 Jun 30:1-7.
4. Everything you need to know about distal renal tubular acidosis in autoimmune disease.
Both T1, Zietse R, Hoorn EJ, van Hagen PM, Dalm VA, van Laar JA, van Daele PL.
Rheumatol Int. 2014 Mar 29.
5. Bilateral nephrocalcinosis, distal renal tubular acidosis and interstitial nephritis in primary Sjögren’s syndrome.
Chen YM1, Hsieh TY2, Chen DY3, Lan JL4.
Joint Bone Spine. 2014 Jun 21. pii: S1297-319X(14)00109-2.
6. Distal renal tubular acidosis due to primary hyperparathyroidism.
Muthukrishnan J1, Hari Kumar KV, Jha R, Jha S, Modi KD.
Endocr Pract. 2008 Dec;14(9):1133-6.
7. Type IV renal tubular acidosis following resolution of acute kidney injury and disseminated intravascular coagulation due to hump-nosed viper bite.
Karunarathne S1, Udayakumara Y, Govindapala D, Fernando H.
Indian J Nephrol. 2013 Jul;23(4):294-6. doi: 10.4103/0971-4065.114476.