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This Article Full Text Full Text (PDF) All Versions of this Article: 295/4/G760    most recent 00333.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by van de Poll, M. C. G. Articles by Dejong, C. H. C. PubMed PubMed Citation Articles by van de Poll, M. C. G. Articles by Dejong, C. H. C.

LIVER AND BILIARY TRACT

The gut does not contribute to systemic ammonia release in humans without portosystemic shunting

Departments of ¹Surgery and ³Radiology, University Hospital Maastricht, Nutrition and Toxicology Research Institute Maastricht, Maastricht University, the Netherlands; ²Department of Surgery, Vrije Universiteit (VU) University Medical Center, Amsterdam, the Netherlands; and ⁴Department of Surgery, Royal Infirmary of Edinburgh, United Kingdom

Submitted 23 July 2007 ; accepted in final form 2 August 2008

The gut is classically seen as the main source of circulating ammonia. However, the contribution of the intestines to systemic ammonia production may be limited by hepatic extraction of portal-derived ammonia. Recent data suggest that the kidney may be more important than the gut for systemic ammonia production. The aim of this study was to quantify the role of the kidney, intestines, and liver in interorgan ammonia trafficking in humans with normal liver function. In addition, we studied changes in interorgan nitrogen metabolism caused by major hepatectomy. From 21 patients undergoing surgery, blood was sampled from the portal, hepatic, and renal veins to assess intestinal, hepatic, and renal ammonia metabolism. In seven cases, blood sampling was repeated after major hepatectomy. At steady state during surgery, intestinal ammonia release was equaled by hepatic ammonia uptake, precluding significant systemic release of intestinal-derived ammonia. In contrast, the kidneys released ammonia to the systemic circulation. Major hepatectomy led to increased concentrations of ammonia and amino acids in the systemic circulation. However, transsplanchnic concentration gradients after major hepatectomy were similar to baseline values, indicating the rapid institution of a new metabolic equilibrium. In conclusion, since hepatic ammonia uptake exactly equals intestinal ammonia release, the splanchnic area, and hence the gut, probably does not contribute significantly to systemic ammonia release. After major hepatectomy, hepatic ammonia clearance is well preserved, probably related to higher circulating ammonia concentrations.

liver; kidney; interorgan; hepatectomy