The effects on morphologically and electrophysiologically characterized myenteric neurons of activation of intestinal reflex pathways were examined in vitro. Opened segments of guinea pig small intestine were pinned serosa down in an organ bath that had two balloons set into its base. A 5-10-mm-wide strip of myenteric plexus between the balloons was exposed from the mucosal side, and neurons were impaled with microelectrodes. Reflex pathways were stimulated by inflation of the balloons to distend the intestinal wall, and by deforming the exposed mucosal villi with a brush. Impaled neurons were classified electrophysiologically as AH-neurons or S-neurons (Hirst et al., 1974) and were injected with biocytin to determine their shapes and projections. None of the 58 AH-neurons responded to distension. In contrast, 63 of 131 S-neurons responded to distension with a burst of fast EPSPs; about one-third of the responding S-neurons received input from ascending reflex pathways, one-third received input from descending reflex pathways, and one-third received input from both ascending and descending pathways. Most neurons in this last group supplied extensive varicose branches to the tertiary plexus and were probably longitudinal muscle motor neurons. Neurons receiving input from only one pathway usually projected in the direction of that pathway; many of these were circular muscle motor neurons. Almost all neurons responding to distension were also excited by deforming the villi. Responses evoked by distension or deforming the mucosa declined when stimuli were repeated at intervals less than 10 sec. This was seen in ascending and descending pathways but was more prominent in the former. Deforming the mucosa evoked a normal response even when the response to repeated distensions had disappeared. It is concluded that distension and deforming the mucosa excite separate populations of sensory neurons to activate reflex pathways that converge onto common motor neurons and probably onto common interneurons.

Recordings were made from myenteric neurons of the guinea-pig ileum during reflexes evoked by mechanical stimulation of the mucosa. Impaled neurons were injected with dye (Lucifer yellow or biocytin), and their shapes were determined. All neurons were 5-12 mm from the stimulus, a brush stroke that deformed the mucosal villi. Neurons were classified as S-neurons or AH-neurons (Hirst et al., 1974). About 40% of S-neurons oral to a stimulus responded with bursts of fast EPSPs (average frequency, 15-40 Hz); these neurons were in ascending reflex pathways. About 60% of S-neurons anal to a stimulus responded with similar bursts of fast EPSPs or slow depolarizations; these neurons were in descending pathways. Only 2 of 48 AH-neurons responded, both in descending pathways. Most S-neurons in either ascending or descending pathways received inputs from at least 2 or 3 other neurons. Action potentials evoked during a response averaged 3-10 Hz in frequency, with occasional bursts at up to 100 Hz. The speed of conduction along the reflex pathways was about 0.5 m/sec. All S-neurons were uniaxonal, but they differed in size, dendritic morphology, and projections. The axons of S-neurons injected with biocytin were followed up to 7 mm within the myenteric plexus. Three S-neurons projected to the tertiary plexus and were probably longitudinal muscle motor neurons; 2 of these were in descending pathways. Five S-neurons projected along the intestine and had varicose collaterals in some ganglia. These neurons were probably interneurons; 3 were descending and 2 ascending, and all responded in the appropriate reflex pathway. Many S-neurons had short axons that entered the circular muscle and were probably circular muscle motor neurons. Others projected several millimeters along the intestine before entering the circular muscle or fading beyond detection. From this study, we have been able to deduce the circuits mediating ascending and descending mucosa-to-muscle reflexes. It is concluded that AH-neurons are primary sensory neurons and S-neurons are interneurons and muscle motor neurons in the circuits.

Routine biopsies of long-standing fistula tracts in patients with Crohn's disease should be strongly considered and may yield an earlier diagnosis of cancer in the fistula tracts.

We assessed the nonoperative and operative management of adhesive small bowel obstruction (ASBO) and compared complication rates and surgical outcomes. ASBO is a common complication of abdominopelvic surgery. Although patients may respond to nonoperative management, many require surgery. We retrospectively studied patients admitted to Mount Sinai Hospital with a diagnosis of complete ASBO to determine outcomes of nonoperative management. Patients admitted with complete ASBO from 2001 to 2011 were included. Patients with no previous abdominopelvic surgery, surgery within the six weeks preceding admission and obstruction due to other identifiable causes, such as incarcerated hernia, were excluded. Complication rates and outcomes were compared between patients managed with immediate surgery and those managed initially with non-operative strategies. Of 460 patients admitted with complete ASBO, 106 (23.0%) had surgery within 24 hours of admission. At surgery, 20 (18.9%) had ischemic bowel and 8 (7.5%) had perforations. The remaining 354 patients had a trial of nonoperative management lasting at least 24 hours. Of 354 patients managed initially without surgery, 100 (28.2%) patients were discharged without operative intervention during their index admissions. Among the patients having surgery more than 24 hours after admission, indications for surgery were generally failure to resolve, worsening clinical status, and change in imaging findings. Of those patients observed for at least 24 hours, 40 (15.7%) were found to have ischemic bowel and 5 (2.0%) had perforation at surgery. Rates of bowel resection, stoma creation and postoperative complications were similar for the immediate and delayed surgery groups. Among the delayed surgery group, 71 (28.0%) required a bowel resection and 11 (4.3%) stoma creation. Twenty one per cent had postoperative complications, most commonly ileus. There were no statistically significant differences in the outcomes between immediate and delayed groups regardless of duration of delay. Among patients observed with complete ASBO, 24.6 per cent of patients with adhesive obstruction resolved without surgery or readmission. Delaying operative management did not affect surgical findings or complication rates.