| Normal anion gap acidosis | |
|---|---|
| Other names | Non-anion gap acidosis |
| Specialty | Endocrinology, nephrology  |
Normal anion gap acidosis is an acidosis that is not accompanied by an abnormally increased anion gap.
The most common cause of normal anion gap acidosis is diarrhea with a renal tubular acidosis being a distant second.
The differential diagnosis of normal anion gap acidosis is relatively short (when compared to the differential diagnosis of acidosis):
As opposed to high anion gap acidosis (which involves increased organic acid production), normal anion gap acidosis involves either increased production of chloride (hyperchloremic acidosis) or increased excretion of bicarbonate.
Acidosis is a process causing increased acidity in the blood and other body tissues. If not further qualified, it usually refers to acidity of the blood plasma.
Hyperparathyroidism is an increase in parathyroid hormone (PTH) levels in the blood. This occurs from a disorder either within the parathyroid glands or outside the parathyroid glands. Symptoms of hyperparathyroidism are caused by inappropriately normal or elevated blood calcium leaving the bones and flowing into the blood stream in response to increased production of parathyroid hormone. In healthy people, when blood calcium levels are high, parathyroid hormone levels should be low. With long-standing hyperparathyroidism, the most common symptom is kidney stones. Other symptoms may include bone pain, weakness, depression, confusion, and increased urination. Both primary and secondary may result in osteoporosis.
Electrolyte imbalance, or water-electrolyte imbalance, is an abnormality in the concentration of electrolytes in the body. Electrolytes play a vital role in maintaining homeostasis in the body. They help to regulate heart and neurological function, fluid balance, oxygen delivery, acid–base balance and much more. Electrolyte imbalances can develop by consuming too little or too much electrolyte as well as excreting too little or too much electrolyte.
Hypovolemic shock is a form of shock caused by severe hypovolemia. It could be the result of severe dehydration through a variety of mechanisms or blood loss. Hypovolemic shock is a medical emergency; if left untreated, the insufficient blood flow can cause damage to organs, leading to multiple organ failure.
Hyperchloremia is an electrolyte disturbance in which there is an elevated level of chloride ions in the blood. The normal serum range for chloride is 96 to 106 mEq/L, therefore chloride levels at or above 110 mEq/L usually indicate kidney dysfunction as it is a regulator of chloride concentration. As of now there are no specific symptoms of hyperchloremia; however, it can be influenced by multiple abnormalities that cause a loss of electrolyte-free fluid, loss of hypotonic fluid, or increased administration of sodium chloride. These abnormalities are caused by diarrhea, vomiting, increased sodium chloride intake, renal dysfunction, diuretic use, and diabetes. Hyperchloremia should not be mistaken for hyperchloremic metabolic acidosis as hyperchloremic metabolic acidosis is characterized by two major changes: a decrease in blood pH and bicarbonate levels, as well as an increase in blood chloride levels. Instead those with hyperchloremic metabolic acidosis are usually predisposed to hyperchloremia.
Metabolic acidosis is a serious electrolyte disorder characterized by an imbalance in the body's acid-base balance. Metabolic acidosis has three main root causes: increased acid production, loss of bicarbonate, and a reduced ability of the kidneys to excrete excess acids. Metabolic acidosis can lead to acidemia, which is defined as arterial blood pH that is lower than 7.35. Acidemia and acidosis are not mutually exclusive – pH and hydrogen ion concentrations also depend on the coexistence of other acid-base disorders; therefore, pH levels in people with metabolic acidosis can range from low, normal, to high.
Respiratory acidosis is a state in which decreased ventilation (hypoventilation) increases the concentration of carbon dioxide in the blood and decreases the blood's pH.
The anion gap is a value calculated from the results of multiple individual medical lab tests. It may be reported with the results of an electrolyte panel, which is often performed as part of a comprehensive metabolic panel.
Hypoaldosteronism is an endocrinological disorder characterized by decreased levels of the hormone aldosterone. Similarly, isolated hypoaldosteronism is the condition of having lowered aldosterone without corresponding changes in cortisol.
Metabolic alkalosis is a metabolic condition in which the pH of tissue is elevated beyond the normal range (7.35–7.45). This is the result of decreased hydrogen ion concentration, leading to increased bicarbonate, or alternatively a direct result of increased bicarbonate concentrations. The condition typically cannot last long if the kidneys are functioning properly.
In physiology, base excess and base deficit refer to an excess or deficit, respectively, in the amount of base present in the blood. The value is usually reported as a concentration in units of mEq/L (mmol/L), with positive numbers indicating an excess of base and negative a deficit. A typical reference range for base excess is −2 to +2 mEq/L.
Hyperchloremic acidosis is a form of metabolic acidosis associated with a normal anion gap, a decrease in plasma bicarbonate concentration, and an increase in plasma chloride concentration. Although plasma anion gap is normal, this condition is often associated with an increased urine anion gap, due to the kidney's inability to secrete ammonia.
Renal tubular acidosis (RTA) is a medical condition that involves an accumulation of acid in the body due to a failure of the kidneys to appropriately acidify the urine. In renal physiology, when blood is filtered by the kidney, the filtrate passes through the tubules of the nephron, allowing for exchange of salts, acid equivalents, and other solutes before it drains into the bladder as urine. The metabolic acidosis that results from RTA may be caused either by insufficient secretion of hydrogen ions into the latter portions of the nephron or by failure to reabsorb sufficient bicarbonate ions from the filtrate in the early portion of the nephron. Although a metabolic acidosis also occurs in those with chronic kidney disease, the term RTA is reserved for individuals with poor urinary acidification in otherwise well-functioning kidneys. Several different types of RTA exist, which all have different syndromes and different causes. RTA is usually an incidental finding based on routine blood draws that show abnormal results. Clinically, patients may present with vague symptoms such as dehydration, mental status changes, or delayed growth in adolescents.
Acid–base homeostasis is the homeostatic regulation of the pH of the body's extracellular fluid (ECF). The proper balance between the acids and bases in the ECF is crucial for the normal physiology of the body—and for cellular metabolism. The pH of the intracellular fluid and the extracellular fluid need to be maintained at a constant level.
Contraction alkalosis refers to the increase in blood pH that occurs as a result of fluid losses. The change in pH is especially pronounced with acidic fluid losses caused by problems like vomiting.
Acid–base imbalance is an abnormality of the human body's normal balance of acids and bases that causes the plasma pH to deviate out of the normal range. In the fetus, the normal range differs based on which umbilical vessel is sampled. It can exist in varying levels of severity, some life-threatening.
High anion gap metabolic acidosis is a form of metabolic acidosis characterized by a high anion gap. Metabolic acidosis occurs when the body produces too much acid, or when the kidneys are not removing enough acid from the body. Several types of metabolic acidosis occur, grouped by their influence on the anion gap.
The urine anion gap is calculated using measured ions found in the urine. It is used to aid in the differential diagnosis of metabolic acidosis.
Distal renal tubular acidosis (dRTA) is the classical form of RTA, being the first described. Distal RTA is characterized by a failure of acid secretion by the alpha intercalated cells of the distal tubule and cortical collecting duct of the distal nephron. This failure of acid secretion may be due to a number of causes. It leads to relatively alkaline urine, due to the kidney's inability to acidify the urine to a pH of less than 5.3.
Delta ratio, or "delta-delta", is a formula that can be used to assess elevated anion gap metabolic acidosis and to evaluate whether a mixed acid–base disorder is present. The anion gap (AG) without potassium is calculated first and if a metabolic acidosis is present, results in either a high anion gap metabolic acidosis (HAGMA) or a normal anion gap acidosis (NAGMA). A low anion gap is usually an oddity of measurement, rather than a clinical concern.