How does Acute Kidney Injury (AKI) cause Renal Tubular Acidosis (RTA)?

From the Guidelines

Acute kidney injury (AKI) can cause renal tubular acidosis (RTA) through mechanisms related to tubular dysfunction, as evidenced by the definition of AKI as an increase in creatinine by 0.3 mg/dL within 48 hours or an increase in serum creatinine to 1.5 times baseline, which can lead to impaired renal function and acid-base disturbances 1. AKI is a common condition, affecting up to 20% of hospital inpatients and between 30% to 60% of critically ill patients, with a significant impact on patient morbidity and mortality 1. The condition can be categorized as prerenal, renal, or postrenal, with renal and prerenal etiologies accounting for more than 97% of AKI cases 1.

Key Mechanisms

• Damage to the renal tubules in AKI impairs their ability to properly reabsorb bicarbonate and secrete hydrogen ions, leading to acid-base disturbances characteristic of RTA.
• The most common form of RTA that develops in AKI is Type 4 (hyperkalemic) RTA, which occurs when AKI affects the distal tubules and collecting ducts, reducing aldosterone activity or response 1.
• Type 2 (proximal) RTA can develop when AKI damages the proximal tubules, impairing bicarbonate reabsorption and causing bicarbonate wasting in the urine.
• Type 1 (distal) RTA may occur when AKI affects the distal tubule's ability to secrete hydrogen ions, preventing urine acidification.

Management

• Management of RTA in AKI focuses on treating the underlying cause of AKI, correcting electrolyte imbalances, and providing bicarbonate supplementation when necessary to normalize acid-base status while the kidneys recover.
• Evaluation of the patient with AKI includes a thorough history, physical examination, and laboratory analysis of blood and urine, with renal biopsy may be indicated for differentiation of nephritic and nephrotic syndromes 1.

From the Research

Acute Kidney Injury (AKI) and its Relation to Renal Tubular Acidosis (RTA)

• AKI is a common clinical syndrome characterized by a sudden decline in or loss of kidney function 2
• The etiology of AKI is conceptually classified into three general categories: prerenal, intrarenal, and postrenal 2
• AKI can lead to various complications, including acidosis, which is a condition where the body's fluids become too acidic 3, 4
• Renal Tubular Acidosis (RTA) is a condition where the kidneys are unable to remove excess acid from the body, leading to acidosis 3, 4

Pathophysiology of AKI and RTA

• Acute tubular necrosis, caused by either ischemia or nephrotoxicity, is common in the setting of AKI 2
• The timely and accurate identification of AKI and a better understanding of the pathophysiological mechanisms that cause kidney dysfunction are essential 2
• AKI can lead to RTA due to the kidney's inability to regulate acid-base balance, resulting in excess acid accumulation in the body 3, 4

Association between AKI and RTA

• There is evidence to suggest that AKI can lead to RTA, particularly in critically ill patients 5
• The use of sodium bicarbonate supplements has been studied as a potential treatment for AKI and RTA, but the results are inconclusive 3, 4
• Further research is needed to fully understand the relationship between AKI and RTA, and to develop effective treatments for these conditions 6, 2, 5