Direct and indirect bilirubinemia

 Q: Which of the following cause conjugated hyperbilirubinemia? (select one) 

A) Hemolysis 

B) Sepsis 

C) Impaired hepatic bilirubin uptake 

D) Dyserythropoiesis 

E) Total parenteral nutrition

Answer: E

Distinguishing hyperbilirubinemia between conjugated and unconjugated clears the path to diagnosis. Conjugated bilirubin is also called direct bilirubin, and unconjugated bilirubin indirect bilirubin. This can be remembered by knowing that most of the causes of indirect bilirubinemia are outside the liver and haven't got a chance to conjugate inside the liver.

The most common causes of unconjugated hyperbilirubinemia in ICU are hemolysis, dyserythropoiesis, and stress situations like sepsis. Conjugated hyperbilirubinemia is mostly seen in biliary obstruction, various forms of hepatitis, primary biliary cholangitis (PBC), drugs, toxins, and ischemia (shock liver). 

Total parenteral nutrition (TPN) is frequently used in ICU and usually causes conjugated hyperbilirubinemia.

#hepatology

References:

1. Mitra A, Ahn J. Liver Disease in Patients on Total Parenteral Nutrition. Clin Liver Dis. 2017 Nov;21(4):687-695. doi: 10.1016/j.cld.2017.06.00

2. Żalikowska-Gardocka M, Przybyłkowski A. Review of parenteral nutrition-associated liver disease. Clin Exp Hepatol. 2020;6(2):65-73. doi:10.5114/ceh.2019.955288. Epub 2017 Aug 19. PMID: 28987256.

3. Raman M, Allard JP. Parenteral nutrition related hepato-biliary disease in adults. Appl Physiol Nutr Metab. 2007 Aug;32(4):646-54. doi: 10.1139/H07-056. PMID: 17622278.