My suspicion is there's extensive platelet and fibrin deposition caused by the endothelial damage (notably in the renal arterioles) seen in cases of super-high blood pressures. In other diseases, like eosinophilic granulomatosis with polyangiitis (Churg-Strauss), a mixture of immune complexes, platelets and fibrin pass through the endothelium, in the absence of HTN.