Brief Answer: it can be idiopathic Detailed Answer: Hello XXXXXXX In such a case, where all reports are normal, it could be considered idiopathic. That is without any known cause or problem. One reason that I can think of when heart, kidney and lungs are normal is a thyroid dysfunction. Is your father's thyroid function normal? This can cause leg/feet swelling as well. Another possibility is blood stasis due to physical inactivity or sitting or standing for long time. I would suggest him to go on regular walks and do moderate physical activity to prevent this. It definitely helps. He can also do a limb elevation using pillows while sleeping. Hope this gives you a clue. Regards,

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