title: Mechanism of diarrhea in microscopic colitis.
abstract: OBJECTIVE
  To search the pathophysiological mechanism of diarrhea based on daily stool weights, fecal electrolytes, osmotic gap and pH.
  
  
  METHODS
  Seventy-six patients were included: 51 with microscopic colitis (MC) (40 with lymphocytic colitis (LC); 11 with collagenous colitis (CC)); 7 with MC without diarrhea and 18 as a control group (CG). They collected stool for 3 d. Sodium and potassium concentration were determined by flame photometry and chloride concentration by titration method of Schales. Fecal osmotic gap was calculated from the difference of osmolarity of fecal fluid and double sum of sodium and potassium concentration.
  
  
  RESULTS
  Fecal fluid sodium concentration was significantly increased in LC 58.11+/-5.38 mmol/L (P<0.01) and CC 54.14+/-8.42 mmol/L (P<0.05) than in CG 34.28+/-2.98 mmol/L. Potassium concentration in LC 74.65+/-5.29 mmol/L (P<0.01) and CC 75.53+/-8.78 mmol/L (P<0.05) was significantly less compared to CG 92.67+/-2.99 mmol/L. Chloride concentration in CC 36.07+/-7.29 mmol/L was significantly higher than in CG 24.11+/-2.05 mmol/L (P<0.05). Forty-four (86.7%) patients had a secretory diarrhea compared to fecal osmotic gap. Seven (13.3%) patients had osmotic diarrhea.
  
  
  CONCLUSIONS
  Diarrhea in MC mostly belongs to the secretory type. The major pathophysiological mechanism in LC could be explained by a decrease of active sodium absorption. In CC, decreased Cl/HCO3 exchange rate and increased chloride secretion are coexistent pathways.
authors.affiliation: Center for Gastroenterology and Hepatology, Zvezdara Clinical Center, Belgrade 11 000, Serbia and Montenegro. marijanaprotic@beotel.yu
authors.forename: Marijana
authors.initials: M
authors.lastname: Protic
authors.forename: Njegica
authors.initials: N
authors.lastname: Jojic
authors.forename: Daniela
authors.initials: D
authors.lastname: Bojic
authors.forename: Svetlana
authors.initials: S
authors.lastname: Milutinovic
authors.forename: Dusanka
authors.initials: D
authors.lastname: Necic
authors.forename: Bozidar
authors.initials: B
authors.lastname: Bojic
authors.forename: Petar
authors.initials: P
authors.lastname: Svorcan
authors.forename: Miodrag
authors.initials: M
authors.lastname: Krstic
authors.forename: Obren
authors.initials: O
authors.lastname: Popovic
mesh_terms: D016022:Case-Control Studies; D046729:Colitis, Collagenous / Q000150:complications / Q000503:physiopathology; D046730:Colitis, Lymphocytic / Q000150:complications / Q000503:physiopathology; D046728:Colitis, Microscopic / Q000150:complications* / Q000503:physiopathology; D003967:Diarrhea / Q000209:etiology* / Q000503:physiopathology; D004573:Electrolytes / Q000032:analysis; D005243:Feces / Q000737:chemistry; D006801:Humans; D006863:Hydrogen-Ion Concentration
chemical_list: D004573:Electrolytes