In a patient with oliguria and jugular vein distention, without elevated isoenzymes, what condition is most likely present?

The presence of oliguria (reduced urine output) and jugular vein distention indicates fluid overload and possible heart failure. Congestive heart failure occurs when the heart is unable to pump effectively, leading to a backlog of fluid in the veins and resulting in elevated venous pressure. This fluid accumulation can cause symptoms such as oliguria due to compromised kidney perfusion or peripheral edema.

The absence of elevated isoenzymes suggests that the current condition is not related to myocardial infarction or other acute cardiac events that would show elevated cardiac biomarkers. Therefore, in the context provided, congestive heart failure aligns more closely with the symptomatology presented, as it can lead to both jugular vein distention and oliguria due to impaired renal blood flow as the kidneys receive less blood and oxygen when the heart cannot pump efficiently.

The other conditions, such as diabetes insipidus, acute kidney injury, and chronic kidney disease, do not typically present with jugular vein distention and the given symptoms in the same way as congestive heart failure.