Professional and Linguistic Assessments Board (PLAB) Practice Exam

Which of the following is a key characteristic of SIADH?

1. Urine retention

2. Hyponatremia

3. Fluid overload

4. All of the above

The correct answer is: All of the above

The condition known as SIADH, or Syndrome of Inappropriate Antidiuretic Hormone secretion, is characterized by several key features, all of which are indeed mentioned in the choices. In SIADH, there is excessive release of antidiuretic hormone (ADH), which leads to significant water retention in the body. This results in the following: The presence of hyponatremia is a hallmark of SIADH. Due to the excess water retention, the sodium concentration in the blood becomes diluted, leading to low sodium levels, or hyponatremia. This is a primary diagnostic criterion for SIADH. Fluid overload is also a characteristic of this condition, as the retention of fluid can lead to an increase in total body water. Patients may present with signs of volume overload such as edema or hypertension despite the low serum sodium levels. Urine retention in this context refers to the retention of excess fluid as a result of the body's inability to excrete it appropriately due to elevated ADH levels. This retention contributes to the dilution of sodium in the bloodstream. Thus, the combination of hyponatremia, fluid overload, and urine retention encapsulates the essential features of SIADH, validating that all the listed