Sorry for late reply and inconvenience.
Thanks for all these additional information.
I understand your concern.
Well as you describe,he has no other symptoms so chances of DVT are less likely.
However sudden increase swelling on foot and ankle indicate other possible causes like Lymphatic obstruction,Cellulitis.
You shouldn't ignore his symptoms and I strongly recommend to see him to doctor ASAP.
Elevate his leg.
Also apply cool compresses on affected area.
His blood pressure should be monitored.
Let me know if you have any further query so we can discuss it thoroughly in every aspect.
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