Hyperoxaluria can be primary or caused by excess ingestion of oxalate-containing foods (eg, rhubarb, spinach, cocoa, nuts, pepper, tea) or by excess oxalate absorption due to various enteric diseases (eg, bacterial overgrowth syndromes, Crohn disease, ulcerative colitis, chronic pancreatic or biliary disease) or ileojejunal (eg, bariatric) surgery.