There are three main diseases that can cause a mixed nephritic/nephrotic syndrome:
1) Membranoproliferative Glomerulonephritis
2) IgA Nephropathy
Note: Rapidly Progressive (Crescentic) Glomerulonephritis (RPGN) usually presents with severe oligurira, nephritic syndrome, and moderate levels of proteinuria that can occasionally reach the nephrotic range. RPGN does not denote a specific etiology, but rather can result from numerous glomerulonephritides.
A pearl we learned from Dr. Naomi Anker at M&M last week: a urine sodium level less than 10 is sensitive for hepatorenal syndrome but not specific. Patients with cirrhosis can be in a majorly sodium-avid state (thus w/ urine sodium < 10) without having hepatorenal syndrome.
HRS is associated with a urine sodium <10, relatively low blood pressures, and a bland urine sediment.
See this August blog post for a discussion of the four types of proteinuria:
Alpers , CE. (2010). The Kidney. In Robbins and Cotran (Eds.) Pathologic Basis of Disease (905-969). Philadelphia, PA: Saunders-Elsevier.