Know More About Renal Tubular Acidosis!

Kidneys are the organs that play a crucial role in maintaining or regulating the acid-base balance in the body. Usually, a body constantly generates acids by breaking proteins down. The kidney excretes typically excessive acid through urine. But, due to some circumstances, this process might get disrupted and result in acid accumulation in the blood. This is known as metabolic acidosis. 

To thoroughly understand Acidosis Tubular Renal, one must first understand the physiology of the kidney and the functions performed by kidneys. Understanding renal physiology also aids in understanding Renal Tubular Acidosis types. 

Renal Tubular Acidosis

Each kidney comprises millions of its smallest functional units- nephrons. This smallest unit is a fine tubule, with one end folded like a cup structure. This cup-like structure is surrounded by a cluster called glomerulus made of tiny blood vessels. As blood enters the nephron, it gets filtered through the glomerulus. 

The tubule can get divided into two parts- proximal and distal tubule. The blood filtered from the glomerulus first enters the proximal tubule and then moves forwards to the distal tubule. When filtrate moves through these tubules, numerous substances are added, and numerous substances are reabsorbed. This leads to the formation of urine as the final product. 

From the filtrate, bicarbonate is reabsorbed in the proximal tubule. At the same time, acid is secreted in the distal tubule into the filtrate from the blood and is excreted through urine. If any of these two processes are disrupted, it results in metabolic acidosis. Acidosis Tubular Renal is a syndrome that results in the kidneys being unable to excrete enough acid, reabsorb enough base, or failing to do both. This syndrome can get divided into three Renal Tubular Acidosis types. 

Types of RTA and their causes

• Type 1 RTA

Type 1 Renal Tubular Acidosis is also known as Distal RTA as it is caused if nephrons in the distal tubule are not secreting enough acid in the urine. The list of causes for the Type 1 RTA is a long one. It is mainly caused due to illnesses that affect nephrons and make them unable to secrete enough acid in the urine. Autoimmune diseases like lupus, rheumatoid arthritis, Sjogren’s syndrome, and inherited diseases like sickle-cell anaemia, Ehlers-Danlos syndrome, Wilson’s disease, and Marfan syndrome are some diseases that can cause this type of acidosis tubular renal. Some renal tissue diseases like medullary nephrocalcinosis are also a common cause of Type 1 RTA. Chronic rejection after renal transplantation can also cause it. The disease is also associated with amphotericin B or lithium medications. 

• Type 2 RTA

This is also known as Proximal RTA. It is characterized by the failure of the Proximal tubules to reabsorb enough base from the filtrate. Type 2 RTA is not common, and just like Type 1, it also occurs due to other diseases. Fructose intolerance, Wilson’s disease, Fanconi syndrome, and Tyrosinemia are some hereditary diseases that can cause Type 2 RTA. Heavy metal poisoning and multiple myeloma are other causes of Type 2 RTA. Medications like acetazolamide can also result in this type of Acidosis Tubular Renal. 

• Type 4 RTA

Hormone Aldosterone deficiency results in Type 4 RTA or Hyperaldosteronism-associated RTA. It can also be caused if the kidney cells do not respond to aldosterone. Medications like angiotensin inhibitors, immunosuppressants, heparin, nonsteroidal anti-inflammatory drugs, some antibiotics, and diuretics can cause Type 4 RTA. It can also result from some disorders that affect the adrenal glands. There are also rare chances, but it can also be caused due to a low level of aldosterone or resistance to the action of aldosterone due to inherited conditions. 

Conclusion

Renal Tubular Acidosis is a disorder related to the kidneys. It is a clinical syndrome that fails the kidney to secrete the expected amount of acid through urine, reabsorb enough base from the filtrate or both. The Acidosis Tubular Renal is classified into Type 1 RTA, Type 2 RTA, and Type 4 RTA. All the Renal Tubular Acidosis types are caused due to varying reasons. Also, all these types have numerous causes behind them. Usually, RTA is caused due to other diseases, which may be inherited diseases, autoimmune diseases, or others.