Partner in hospital 7 days (on a gastroenterology ward under the care of a gastroenterologist!). They have admitted they haven’t a clue what is wrong with her?

My partner is a 47 year old female who had major abdominal surgery (mesh repair of failed linea alba) just under 6 weeks ago. Prophylactic Clexane wasn’t give first 2 days by mistake then given for four days thereafter. She developed a small blue lump under the second toe on the right foot the day after the op. 2 weeks after the op, she developed distended veins in the left side of the neck – external jugular, anterior jugular, some small veins joining the two. A few days later she also showed distended veins up into the temple and between her eye and the bridge of her nose. Coincident with the veins becoming obvious, she started suffering pre-syncope when exercising (e.g. 10 minutes walking) culminating in a full syncope episode at 4 weeks post op. She was re-admitted to hospital at this point. d-Dimer significantly raised (more than would be expected from prior surgery). No other markers for inflammation or infection – surgical wound site appears infection free. Chest X-ray clear. CT Angiogram also clear. ECG clear. Monitoring shows BP is high (at least for this patient) and does not drop during syncope events. Pulse also high (100-110 resting and pushing 150 with low level exercise). Patient feels OK when lying down but gradually develops pre-syncope over 5-10 minutes when upright and walking. Has now developed pea-sized lump in back of left leg around 1.5cm above knee and slightly lateral to the centre line. There is a 2cm diameter bruise adjacent to this and oedema distal to it. We are told Doppler ultrasound of the neck area was clear but weren’t massively impressed by the skill/knowledge of the ultrasonographer. She has now been in hospital 7 days (on a gastroenterology ward under the care of a gastroenterologist!). They have admitted they haven’t a clue what is wrong with her. She has been given a cursory exam by a vascular surgeon who seemed uninterested because the Doppler of the neck was clear. I’d really appreciate suggestions for what possible diagnoses might fit this pattern. To me there’s one obvious suggestion (which I won’t mention because I want to confirm whether I’m going mad or not) but I’m also interested in possible alternatives so we can try to guide the staff into doing something about this. Many thanks in advance for your help.