From the Guidelines
The correct answer is C. Hypercalcemia, as it is the most common electrolyte abnormality associated with malignancy, particularly in lung cancer patients, occurring in approximately 10-25% of patients with lung cancer, as stated in the American College of Chest Physicians evidence-based clinical practice guidelines 1.
Clinical Presentation and Mechanisms
The symptoms described in the case, such as confusion and constipation, are classic manifestations of hypercalcemia. This electrolyte imbalance typically develops through several mechanisms in cancer patients: tumor secretion of parathyroid hormone-related protein (PTHrP), local osteolytic bone destruction by tumor cells, or production of vitamin D-like substances by certain tumors. In lung cancer specifically, the most common mechanism is PTHrP secretion, which increases bone resorption and renal calcium reabsorption, leading to elevated serum calcium levels 1.
Diagnosis and Management
The diagnostic evaluation of hypercalcemia includes measuring serum concentrations of intact parathyroid hormone (iPTH), PTHrP, 1,25-dihydroxyvitamin D, 25-hydroxyvitamin D, calcium, albumin, magnesium, and phosphorus. Management of hypercalcemia may involve oral hydration for mild cases, while moderate to severe hypercalcemia requires rehydrating with IV crystalloid fluids not containing calcium, giving loop diuretics as needed, and administering bisphosphonates, which are usually effective 1.
Prognosis and Quality of Life
It's essential to note that the median survival after discovery of hypercalcemia of malignancy in patients with lung cancer is about 1 month 1, highlighting the need for prompt diagnosis and management to improve quality of life. Early recognition and treatment of hypercalcemia can alleviate symptoms, prevent further complications, and potentially improve outcomes in patients with lung cancer.
From the Research
Electrolyte Abnormalities in Malignancy
The patient's symptoms of confusion and constipation, along with laboratory results confirming an electrolyte imbalance, suggest a possible connection to the underlying malignancy. The most common electrolyte abnormalities associated with malignancy are:
- Hyponatremia
- Hypokalemia
- Hypercalcemia
- Hypomagnesemia
Association with Malignancy
Studies have shown that hypercalcemia is a common electrolyte abnormality in patients with malignancy, particularly in those with lung cancer 2, 3, 4. Hypercalcemia can be caused by the production of parathyroid hormone-related protein (PTHrP) by tumor cells, leading to an increase in serum calcium levels 2, 3, 4.
Comparison of Options
Comparing the options provided:
- A. Hyponatremia: while it can occur in patients with malignancy, it is not as commonly associated with lung cancer as hypercalcemia 5.
- B. Hypokalemia: can occur in patients with malignancy, but it is not as specifically linked to lung cancer as hypercalcemia 5.
- C. Hypercalcemia: is commonly associated with malignancy, particularly in patients with lung cancer 2, 3, 4.
- D. Hypomagnesemia: can occur in patients with malignancy, but it is not as specifically linked to lung cancer as hypercalcemia 6.
Most Commonly Associated Electrolyte Abnormality
Based on the evidence, hypercalcemia is the most commonly associated electrolyte abnormality with malignancy, particularly in patients with lung cancer 2, 3, 4.