From the Guidelines
Hypochloremic metabolic alkalosis is primarily caused by conditions that lead to excessive loss of chloride ions, such as congenital chloride diarrhea, Bartter syndrome, and cystic fibrosis, as well as other rare tubulopathies, as evidenced by recent studies 1. The causes of hypochloremic metabolic alkalosis can be broadly categorized into several key areas, including:
- Congenital conditions, such as Bartter syndrome, which is characterized by hypokalemic and hypochloremic metabolic alkalosis, as noted in a 2021 study published in Kidney International 1
- Gastrointestinal disorders, including congenital chloride diarrhea, which leads to pronounced hypokalemic and hypochloremic metabolic alkalosis secondary to watery diarrhea
- Renal disorders, such as pseudo-Bartter syndrome, occasionally observed in cystic fibrosis due to salt loss in sweat
- Other rare tubulopathies, as listed in Table 4 of the study, which can also exhibit metabolic alkalosis Key characteristics of these conditions include:
- Hypokalemic and hypochloremic metabolic alkalosis
- Polyuria and polyhydramnios
- Variable plasma Cl/Na ratio
- Other findings, such as mild hypomagnesemia, deafness, and risk for chronic kidney disease It is essential to distinguish between renal and extrarenal salt losses, using urinary chloride excretion assessed by either fractional chloride excretion or urinary sodium/chloride ratio, to guide diagnosis and treatment 1.
From the Research
Causes of Hypochloremic Metabolic Alkalosis
The causes of hypochloremic metabolic alkalosis can be attributed to several factors, including:
- Loss of chloride-rich body fluids, such as through vomiting or diuretics use 2, 3, 4
- Excessive hydrogen ion loss by the gastrointestinal tract or by the kidney 4
- Exogenous base gain 4
- Maintenance of alkalosis due to hypovolemia, chloride depletion, hypokalemia, hyperaldosteronism, renal failure, or a combination of these factors 3, 4
- Surreptitious ingestion of substances with mineralocorticoid activity, such as baking soda 5
- Use of loop diuretics 4
Underlying Mechanisms
The underlying mechanisms of hypochloremic metabolic alkalosis involve:
- Impaired renal base excretion, often produced by hypochloremia 3
- Inability of the kidney to excrete excess bicarbonate due to various factors, including hypovolemia, chloride depletion, and hypokalemia 4
- Generation of alkalosis through excessive hydrogen ion loss or exogenous base gain, and maintenance of alkalosis due to the aforementioned factors 4
Clinical Implications
The clinical implications of hypochloremic metabolic alkalosis include:
- Increased risk of death in severe cases 3
- Need for careful evaluation of volemic status and measurement of urinary chloride and plasma levels of renin and aldosterone to identify the cause(s) of metabolic alkalosis 4
- Importance of correcting existing depletions and preventing further losses as the cornerstone of treatment 4