Effect of liver disease and transplantation on urea synthesis in humans: Relationship to acid-base status

Robert E. Shangraw, Farook Jahoor

Research output: Contribution to journalArticlepeer-review

46 Scopus citations


It has been suggested that hepatic urea synthesis, which consumes HCO3/-, plays an important role in acid-base homeostasis. This study measured urea synthesis rate (R(a) urea) directly to assess its role in determining the acid-base status in patients with end-stage cirrhosis and after orthotopic liver transplantation (OLT). Cirrhotic patients were studied before surgery (n = 7) and on the second postoperative day (n = 11), using a 5-h primed-constant infusion of [15N2]urea. Six healthy volunteers served as controls. R(a) urea was 5.05 ± 0.40 (SE) and 3.11 ± 0.51 μmol·kg- 1·min-1, respectively, in controls and patients with cirrhosis (P < 0.05). Arterial base excess was 0.6 ± 0.3 meq/l in controls and -1.1 ± 1.3 meq/l in cirrhotic patients (not different). After OLT, R(a) urea was 15.05 ± 1.73 μmol·kg-1 min-1 which accompanied an arterial base excess of 7.0 ± 0.3 meq/l (P < 0.001). We conclude that impaired R(a) urea in cirrhotic patients does not produce metabolic alkalosis. Concurrent postoperative metabolic alkalosis and increased R(a) urea indicate that the alkalosis is not caused by impaired R(a) urea. It is consistent with, but does not prove, the concept that the graft liver responds to metabolic alkalosis by augmenting R(a) urea, thus increasing HCO-3 consumption and moderating the severity of metabolic alkalosis produced elsewhere.

Original languageEnglish (US)
Pages (from-to)G1145-G1152
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Issue number5 39-5
StatePublished - May 1999
Externally publishedYes


  • Acid-base metabolism
  • Ammonia
  • Base excess
  • Cirrhosis
  • Metabolic alkalosis

ASJC Scopus subject areas

  • Physiology
  • Hepatology
  • Gastroenterology
  • Physiology (medical)


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