A 56-year-old man with renal failure who missed his last dialysis appointment presents with dizziness, lethargy, difficulty breathing, rales at the bases, BP 160/90, SpO2 92%. What is the most likely diagnosis?

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Fluid overload from missed dialysis in renal failure causes the body to retain excess fluid, which backs up into the lungs and leads to pulmonary edema. The crackles you hear at the lung bases, the trouble breathing, and the drop in oxygen saturation all come from fluid accumulating in the alveoli and interstitial spaces, impairing gas exchange. The high blood pressure reflects volume expansion and elevated preload rather than poor perfusion from shock. This pattern fits fluid overload much more than the other conditions.

Hyponatremia typically presents with confusion, seizures, or neurologic symptoms rather than overt pulmonary edema. Hyperkalemia causes muscle weakness and characteristic heart rhythm changes, not primarily pulmonary symptoms. Cardiogenic shock features reduced perfusion with usually lower blood pressure, not the elevated pressure and fluid-backed signs seen here.