Examining each option:
Option 1: Hypertension is a medical condition characterized by high blood pressure.
Option 2: Ulcer is a medical condition involving sores in the digestive system lining.
Option 3: Kidney is an organ in the human body responsible for filtering blood and producing urine.
Option 4: Anaemia is a medical condition characterized by deficiency of red blood cells or hemoglobin.
Options 1, 2, and 4 (Hypertension, Ulcer, and Anaemia) are all diseases or medical conditions.
Option 3 (Kidney) is an organ of the body, not a disease or medical condition.
Therefore, the odd one out is Option 3: Kidney, as it represents a body organ while all other options represent diseases or medical conditions.