Circadian periodicity of the time of onset of acute lower gastrointestinal bleeding.

We investigated the chronobiological parameters of acute gastrointestinal (GI) bleeding in 51 patients able to time-specify the onset of bleeding within 30 min of occurrence. Bleeding was determined to be either from the upper or lower GI tract. The upper GI bleeding group consisted of 32 patients (22 male, 10 female) who bled from peptic ulcer disease (16), Mallory-Weiss tear (4), gastritis (3), esophageal varices (3), gastric neoplasm (2), Dieulafoy's lesion (1), and unknown (3). The lower GI bleeding group consisted of 19 patients (9 male, 10 female) who bled from diverticulosis coli (5), hemorrhoids (2), arteriovenous malformations (2), colonic polyps (2), cecal ulcer (1), antibiotic-associated colitis (1), and unknown (6). Rhythmicity was evaluated by inferential statistics. The time of onset of lower GI bleeding (34 episodes) displayed significant circadian periodicity (p = 0.014) with its peak at 1100 h. Single cosinor analysis revealed: MESOR-1.42 (95% CI = 0.86- 1.97); amplitude = 1.22 (0.44-1.99); phase angle = -165.12 (-201.66 -128.58). Upper GI bleeding (42 episodes) displayed no circadian periodicity (p = 0.46). When both upper and lower GI bleeding were evaluated together, no circadian rhythm was evident (p = 0.07). We conclude that there is a circadian periodicity in the time of onset of only acute lower GI bleeding with its peak at 1100 h. The pacemaker of this periodicity remains unknown.