A patient with abdominal distention, weakness, and occasional diarrhea has a history of renal failure. What condition is he most likely experiencing?

The patient's symptoms of abdominal distention, weakness, and occasional diarrhea, combined with a history of renal failure, strongly suggest he is experiencing hyperkalemia.

In cases of renal failure, the kidneys' ability to excrete potassium decreases, leading to an accumulation of potassium in the bloodstream. Hyperkalemia can present with gastrointestinal symptoms such as abdominal distention and diarrhea, as the elevated potassium levels can impact muscle function, including the muscles of the gastrointestinal tract. Additionally, weakness is a common symptom due to the effects of high potassium on neuromuscular function, potentially leading to muscle fatigue or paralysis.

While the other conditions listed—hypokalemia, hypernatremia, and hyponatremia—could present with different symptoms, they do not align with the clinical picture described. For instance, hypokalemia would typically cause weakness and potentially constipation rather than diarrhea, while hypernatremia and hyponatremia would primarily affect fluid balance and produce different neurological and cardiovascular symptoms. Thus, considering the clinical context and the described symptoms, hyperkalemia is the most plausible diagnosis for this patient.