0016-5107/88/3502-0093$02.00 GASTROINTESTINAL ENDOSCOPY Copyright © 1989 by the American Society for Gastrointestinal Endoscopy
Mucosal pseudolipomatosis: an air pressurerelated colonoscopy complication J. Patrick Waring, MD, Rao K. Manne, MD Darrell D. Wadas, MD, Robert A. Sanowski, MD Phoenix, Arizona
Mucosal pseudolipomatosis is a recently described colonoscopic finding, most likely caused by intramucosal air. We describe four asymptomatic patients with this lesion which completely resolved 3 weeks later on repeat colonoscopy. This is a benign, transient lesion with distinct endoscopic and histologic findings. The similarity between mucosal pseudolipomatosis and pneumatosis cystoides intestinalis is supportive of the mechanical theory for pneumatosis cystoides intestinalis. (Gastrointest Endosc 1989;35:93-94)
A number of air pressure-related colonoscopic complications have been identified including intramural air/ benign pneumoperitoneum,2 serosal tear,3 and pneumatosis cystoides coli. 4- 6 Each has been described in the absence of obvious perforation. A colon lesion with histologic evidence of intramucosal air has been recently described. 7 It was termed mucosal pseudolipomatosis because of its similarity to the previously recognized rectal lipomatosis.8 The clinical significance of this lesion is not clearly understood. We will review the endoscopic and histologic features of four patients with mucosal pseudolipomatosis and discuss its clinical significance. MATERIALS AND METHODS
Three asymptomatic patients ages 59 to 64 underwent follow-up colonoscopy for previously identified lesions (see Table 1). All received standard oral preparation with Colyte® (Reed-Carnick Industries, Piscataway, N.J.) and were sedated with meperidine or diazepam. Colonoscopy was performed to the cecum with either Olympus CV-lOL video colonoscope or CF-lOL instrument (Olympus Corporation, Lake Success, N.Y.) without complication. The characteristic mucosal lesions were seen in each patient on initial colonoscopy. Patient 3 had a barium enema 4 days after colonoscopy. All patients had repeat colonoscopy 3 weeks later. A fourth patient had a flexible sigmoidoscopy 3 weeks after colonoscopic polypectomy. These four patients represent 0.3% of the 1388 colonoscopies and sigmoidoscopies performed in our endoscopy unit in 1986. Biopsies from affected areas were stained with hematoxylin and eosin, Oil Received January 4, 1988. For revision January 26, 1988. Accepted February 24,1988. From the Departments of Gastroenterology and Pathology, Veterans Administration Medical Center, Phoenix, Arizona. Reprint requests: J. Patrick Waring, MD, Department ofGastroenterology, VA Medical Center, 7th Street and Indian School Rd., Phoenix, Arizona 85012. VOLUME 35, NO.2, 1989
Red 0, mucicarmine, and periodic acid-Schiff in addition to evaluation under polarized light. RESULTS
The four patients each had multiple, slightly raised, adherent, white, confluent lesions in various areas of the colon (Fig. 1). Three patients also had polyps, but not in the same areas. No biopsies were taken before visualizing the white lesions. Biopsies showed multiple small, round intramucosal cystic spaces (Fig. 2). Staining with Oil Red 0, mucicarmine, and periodic acidSchiff were negative, indicating that these spaces were not filled with fat or mucin. Polarized light examination showed no cholesterol crystals. No inflammation, pseudomembrane, ulcerations, or submucosal spaces were identified. Patient 3 had a normal barium enema 4 days postcolonoscopy. On repeat colonoscopy 3 weeks later all lesions had resolved. DISCUSSION
We have encountered a transient entity that is clinically, endoscopically, and histologically distinct Table 1. Patient data at initial colonoscopy Patient
Location of MPL
F/U" polyps F/U rectal ca
F/UCUP F/U polyp
Cecum/ascending Ascending/ descending Cecum/ascending Descending
Other findings Normal 1 polyp 5 polyps 3 polyps
"F/U, follow-up; CUP, carcinoma, unknown primary. b Flexible sigmoidoscopy.
but it is unlikely to be simply an air pressure phenomenon. The initial injury during overinflation of colon segments is serosal laceration not mucosal damage.3,4 Indeed, we could not reproduce these lesions by simply overinflating cadaver colons. Perhaps mucosal injury from stretching, abrasive trauma, or biopsy, coupled with overinflation of the colon could lead to the development of MPL. The role of colon gas composition is unclear, certainly much of the air in the colons of our patients was inserted during the procedure. Pneumatosis cystoides intestinalis has been reported to be an air pressure-related colonoscopy complication. Intramucosal air-filled spaces similar to those seen in our patients have been recognized in PCL 9 Eleven of 13 patients in that PCI study had mucosal architectural abnormalities and the authors suggested that the mucosal air, along with various degrees of mucosal inflammation, led to the development of PCL Heer et a1. 6 also made the observation that colonoscopy-induced PCI did not occur in the absence of predisposing conditions. Evidence of PCI was not seen in the four patients in our study with MPL and no mucosal inflammation but, perhaps, PCI might have developed if our patients had mucosal inflammation. Mucosal pseudolipomatosis is a rare, benign, transient lesion that must not be confused with similar but more serious medical problems. It is rather easy to recognize endoscopically and, if necessary, by routine histologic study. It does not require additional evaluation or therapy. It is likely an air pressurerelated colonoscopy complication and, in the absence of underlying inflammation, should not progress to PCL Figure 1. Confluent, raised white patches seen on video colonoscopy. Figure 2. Intramucosal cystic spaces (H & E, x40).
from pneumatosis cystoides intestinalis (PCI), colitis cystica profunda, pseudomembranous colitis, inflammatory bowel disease, or neoplasia. We believe these intramucosal cystic lesions are filled with air, as proposed by Snover et al. 7 in their original article on mucosal pseudolipomatosis (MPL). They described MPL in 24 patients undergoing colonoscopy for guaiac-positive stools. No other lesion was found in 21 of those patients, suggesting that MPL may have been responsible for occult gastrointestinal bleeding. However, our patients were all asymptomatic, with no rectal bleeding specifically, and no abdominal pain, fever, or diarrhea. MPL was not seen on repeat colonoscopy 3 weeks later. No common variable was identified, as MPL was seen by several different endoscopists, using a variety of endoscopes, light sources, and preparations. The cause of these lesions is unknown. The transient presence of MPL in asymptomatic patients suggests it is more likely a complication of the procedure, 94
The authors wish to thank Joan Hillier for her assistance in preparation of the manuscript.
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