Electromotor activity of the cecum and ascending colon: the concept of 'individual pacemakers'.
OBJECTIVE
The cecum is described as differing anatomically from the ascending colon (AC); yet their similarity or difference in terms of motile activity has not been studied sufficiently. The cecum is separated from the AC by the cecocolonic junction (CCJ) which contains a cecocolonic sphincter. We assumed that the motile activity of the AC is different from that of the cecum and hypothesized that both the AC and the cecum might have different pacemakers which initiate the motile activity. This hypothesis was investigated in the current study.


METHODS
The study was performed in 10 subjects (mean age 41.6 +/- 12.8 SD years; 7 women) during the repair of huge abdominal incisional hernias. The electric activity was recorded from 2 monopolar electrodes applied each to the cecum, CCJ and AC. The CCJ was then anesthetized by xylocaine and the electric waves of the cecum, CCJ and AC were registered after 10 and 90 min. The test was repeated using normal saline instead of xylocaine.


RESULTS
Electric waves were recorded from the cecum, CCJ and AC in the form of monophasic pacesetter (PPs) and action potentials (APs). The PPs occurred regularly and the APs randomly. The frequency, amplitude and conduction velocity of the waves recorded from the CCJ and AC had higher readings than those from the cecum (p < 0.05). The CCJ and AC showed similar frequency and conduction velocity (p > 0.05). Ten minutes after CCJ anesthetization, electric waves were recorded from the cecum but not from the CCJ or AC; however, electric activity returned after 90 min. Saline injection did not affect the electric activity of the cecum, CCJ and AC.


CONCLUSIONS
The electric wave parameters of the cecum differed from those of the CCJ and AC, suggesting that the motile activity of the CCJ and AC is not a continuation of the motile activity of the cecum and that it might be evoked by 2 different pacemakers. The similarity in frequency and conduction velocity of electric waves of the CCJ and AC, however, most likely denotes that the AC waves are a continuation of those of the CCJ, and that both are evoked by the same pacemaker probably located in the CCJ. The higher amplitude of cecal waves might be due to the thicker cecal musculature compared to that of the AC.
Shafik
A
A
Department of Surgery and Experimental Research, Faculty of Medicine, Cairo University, Cairo, Egypt. shafik@ahmed-shafik.org
Mostafa
Randa M
RM
El-Sibai
O
O
Shafik
I A
IA
D000328:Adult; D000779:Anesthetics, Local / Q000494:pharmacology; D001683:Biological Clocks; D002432:Cecum / Q000187:drug effects / Q000503:physiopathology*; D044682:Colon, Ascending / Q000187:drug effects / Q000503:physiopathology*; D004576:Electromyography; D005260:Female; D006801:Humans; D008012:Lidocaine / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D016065:Myoelectric Complex, Migrating / Q000187:drug effects
D000779:Anesthetics, Local; D008012:Lidocaine