This condition, in my opinion and studies, is created by a biochemical change in the body. Something invaded/damaged (changed/altered DNA) caused by a surgery, implant, infection, prescription medication such as ASA, toxin, etc.(something damaging natural function), and it damaged the immune system/gut. About 70-80 percent of our immune system is in the gut. In the holistic community, it is known as Leaky Gut Syndrome and Systemic Capillary Leak Syndrome (Clarkson's) in the regular medical profession.
No matter what you call it, it can and does cause a world of damage in the body depending on the severity of damage, affected body system or part and even death. It can cause hypotension, hemoconcentration, compartment syndrome, pleural effusion, severe interstitial (third spacing) edema and pain, just to mention a few. There are no standard tests for it. Sealing the gut is the key.
The patient is leaking everything at a molecular level, not just plasma. Take control of what leaks! The GAPS diet works wonders. Eat fermented foods to aid digestion, raw honey (allergy permitting), natural probiotics, all non-GMO (genetically mutated organisms) foods and organic foods are a great start.
Find a doctor who cares and listens to you and your body. Keep everything as pure as possible that comes in contact with the patient. That includes soaps, shampoos, make up, cleaning supplies, air, water, perfumes (spray only on distant clothes only if you must use). Even toothpaste can have a detrimental effect on the leaking patient due to the chemicals in the toothpaste. A leak phase can last from three to seven days, but I believe the recovery phase is where most damage occurs. Also, IVIG administration has had limited success and should be further explored and discussed with your trusted doctor. Good luck and stay well to all!