LETTERS TO EDITOR

tinal Tract. A Allen, G Flemstrom, A Garner, W Silen, LA Turnberg, (eds). New York, Raven Press, 1984, pp 381-382

5. Ritchie WP Jr: Pathogenesis of acute gastric mucosal injury. Viewpoints on Dig Dis Sci 15:17-20, 1983

6. Seyle H: Hormones and Resistance. New York, Springer- Verlag, 1971

DIVERTICULAR RUPTURE

To The Editor: The article by Dr. Brayko and colleagues (Dig Dis

Sci 29:427-431, 1984) demonstrates that uncompli- cated diverticula within segments of human sigmoid colon removed 9 hr postmortem are less likely to rupture with increases in intraluminal pressure than contiguous bowel wall. Dr. Brayko and colleagues note the limitations of extrapolating this finding to colonoscopy in vivo. I would expand on this by pointing out that the risk of rupture of diverticula during colonoscopy may come not from general increases in intraluminal sigmoid colon pressure as measured in their study. Rather, the risk probably arises from rapidly rising intradiverticular pressures due to inadvertent intubation of the colonoscopic tip into a diverticulum and insufflation of air (1). The practicing colonoscopist will be familiar with the similarity of a diverticular orifice and the con- tracted colonic lumen proximal to the endoscope.

The danger is confounded by the absence of a sensing device preventing such pressure rises in some colonoscopes. This can be dramatically dem- onstrated by exploding a finger stall sealed over the colonscope tip. A standard Olympus colonoscope can generate a pressure of 800 cm H20 (570 mm Hg) in a 2- to 5-cm 3 "closed system" in less than 1/2 sec of air insufflation (1)! Fujinon endoscopes have microelectronic switches controlling air insuffla- tion, effectively precluding even tactile sensation of increasing pressure within the air channel.

Although perforation is uncommon during colon- oscopy (2), I do not think the design of Dr. Brayko's

study enables an appropriate assessment of the risk in the presence of diverticular disease.

FINLAY MACRAE, MD, FRACP, MRCP (UK)

The Royal Melbourne Hospital Department o f Gastroenterology

Parkville, 3050, Australia

REFERENCES

1. Williams CB, Lane RH, Sakai Y, Hanwell AE: Colonoscopy: an air-pressure hazard. Lancet 2:729, 1973

2. Macrae FA, Tan KG, Williams CB: Towards safer colonos- copy: A report on the complications of 5000 diagnostic and therapeutic colonoscopies. Gut 24:374-383, 1983

SMALL BOWEL NEOPLASM

To The Editor: We recently reported a malignant small bowel

neoplasm of enteric plexus derivation (plexosar- coma) [Dig Dis Sci 29(1):277-284, 1984].

After the case was published, we had the oppor- tunity of performing some immunocytochemistry stains on the tumor, the results of which I believe are important in the characterization of this neo- plasm. We performed vasoactive intestinal peptide and neuron-specific enolase immunostaining, and the neoplastic cells showed diffuse cytoplasmic positivity in both elements identified by light mi- croscopy. Serotonin immunocytochemistry was negative. We believe that the results of these immu- nocytochemistry stains, together with the negative results obtained for S-100 and glial fibrilliary pro- tein, support that this malignant neoplasm is de- rived from enteric plexus.

GUILLERMO A. HERRERA, MD VA Medical Center

Birmingham, Alabama

698 Digestive Diseases and Sciences, Vol. 30, No. 7 (July 1985)