Which of the following conditions could cause fluid accumulation in the body's tissues?

Fluid accumulation in the body's tissues, often referred to as edema, can be influenced significantly by sodium levels. When there is excessive sodium intake, the body retains water to maintain electrolyte balance. This retention leads to an increase in fluid volume in the vascular system and can subsequently cause fluid to leak into surrounding tissues, resulting in edema. High sodium levels are often associated with conditions like heart failure or kidney disease, where the body's ability to manage fluid is compromised.

In contrast, low sodium levels typically lead to water being retained by the kidneys, but this can sometimes result in dilutional effects rather than fluid accumulation. High potassium levels usually do not directly contribute to tissue fluid accumulation, and increased calcium intake is more related to bone health and muscular function rather than fluid balance. Therefore, it is the excessive sodium intake that most clearly correlates with fluid retention in the body's tissues.