Title: A Single-arm, Open-label, Prospective, Multicenter Safety Study to Evaluate the Occurrence of Essential Fatty Acid Deficiency (EFAD) in Pediatric Patients With Parenteral Nutrition-associated Cholestasis (PNAC) Who Require More Than Eight Weeks of Omegaven Treatment

Inclusion Criteria: 1. Patient's parent(s) or legal guardian(s) has provided a signed and dated Informed Consent Form (ICF). 2. Pediatric patient (\<18 years) has been diagnosed with PNAC, defined as direct or conjugated bilirubin (DBil) ≥ 2.0 mg/dL with no other known cause of liver dysfunction at the time of enrollment and is expected to require Omegaven treatment for at least eight weeks. 3. Patient has oral or enteral feeding intolerance or at least one gastrointestinal disorder requiring PN. Exclusion Criteria: 1. Patient has received Omegaven within four weeks before inclusion in the study 2. Patient has any other known cause of chronic liver disease such as hepatitis C, cystic fibrosis, biliary atresia, alpha-1-antitrypsin deficiency, passive hepatic congestion due to heart failure, etc. 3. Patient has known cirrhosis (liver biopsy is not required under this protocol). 4. Patient has been previously diagnosed with, or has prior evidence of, portal vein thrombosis. 5. Patient has previously received a liver-only or liver-inclusive transplant. 6. Patient has hemodynamic instability due to any major cardiac anomaly. 7. Patient has a major life-threatening disease (e.g., sepsis requiring high-dose vasopressors, acute respiratory distress syndrome, veno-occlusive disease, cancer). 8. Patient has multi-organ failure, septic shock, hypotension requiring pressor therapy, persistent pulmonary hypertension requiring inhaled nitric oxides, or requires extracorporeal membrane oxygenation (ECMO) or similar intervention. 9. Patient has renal failure and requires renal replacement therapy. 10. Patient has a severe hemorrhagic disorder. 11. Patient has severe hyperlipidemia or a severe disorder of lipid metabolism characterized by hypertriglyceridemia (i.e., serum triglyceride level \> 1,000 mg/dL). 12. Patient has a record of EFAD before inclusion in the study 13. Patient has been diagnosed with or is suspected to have an inborn error of metabolism. 14. Patient has a known hypersensitivity to fish or egg protein or to any of the active ingredients or excipients of Omegaven. 15. Patient is subject to treatment limitation. 16. Patient is enrolled in any other study with an investigational medicinal product during the course of the current study.