Aim: Colonic mucosal pseudolipomatosis is a rare and benign endoscopic finding with distinct macroscopic and histological characteristics. Case series: We observed a form of unprecedented colitis in eight patients in a 3-month period. Operators have found, during colonoscopy, flat or slightly raised whitish-yellow plaques, in the colonic mucosa of all patients. Histological examination concluded to pseudolipomatosis. After investigation, the disinfectant machine was found to have technical malfunctioning of the rinse cycle of the endoscope during this period. No other cases were observed after the machine was fixed. Conclusion: Pseudolipomatosis is more an endoscopically induced lesion than a true pathological condition. A careful check of the disinfection process should be carried out when such lesions are detected.

A man in his 70s received anticancer chemotherapy with the anti-programmed cell death protein-ligand 1 antibody atezolizumab for non-small cell lung cancer. Ten days later, he developed diarrhea and skin rash, which were suspected to be due to immune-related adverse events, and was treated with prednisolone for 2 weeks. Five weeks after atezolizumab administration, he was admitted to our hospital for Common Terminology Criteria for Adverse Events Grade 3 diarrhea and hematochezia. Sigmoidoscopy revealed a dark red color in the mucosa of the transverse colon and multiple whitish mucosal plaques extending from the transverse colon to the rectum. Biopsy specimens revealed empty vacuoles in the lamina propria with infiltration of numerous inflammatory cells, including CD8⁺ T cells. Based on the findings of sigmoidoscopy and histology, the diagnosis was immune checkpoint inhibitor-related colitis with colonic pseudolipomatosis. The endoscopic findings and symptoms were markedly improved by prednisolone administration. We herein report the first case of immune checkpoint inhibitor-related colitis with characteristic endoscopic findings of colonic pseudolipomatosis. It is important to perform endoscopy and histological evaluation to determine the differential diagnosis and treatment strategy for patients treated with immune checkpoint inhibitors.

A 74-year-old Japanese woman was diagnosed with pseudolipomatosis of the cecum and ascending colon. Colonoscopy was performed, which revealed the presence of slightly elevated white lesions, while a magnifying observation showed microbubbles within the mucosa. A month after colonoscopy, the patient was diagnosed with pneumatosis intestinalis. Although the exact pathogenesis is unclear, pneumatosis intestinalis may arise secondary to pseudolipomatosis. This case also indicates that a magnifying observation during colonoscopy may aid in the diagnosis of pseudolipomatosis of the large intestine, since it shows microbubbles within the mucosa, which may be a distinctive feature reflecting the pathology of this disease.

Colonic mucosal pseudolipomatosis is rare, and its pathogenesis is controversial. A number of mechanisms, including mechanical injury during an endoscopic procedure or chemical injury by disinfectant, seem to contribute to its pathogenesis.

This retrospective study examined the colonic biopsies of 1370 patients. These biopsies were preserved at the Department of Pathology of Istanbul Training and Research Hospital between January 2012 and June 2013.

We found pseudolipomatosis in 14 of 1370 colonoscopy cases (1.02%). Of these 14 patients, 8 were male and 6 were female. The male patients were between 24 and 66 years, with a mean of 39; the female patients were between 26 and 58 years, with a mean of 42.

Many endoscopists are unaware of the lesion, and the diagnosis is generally possible only after pathological assessment of multiple biopsies taken from suspect lesions. Here we report and discuss colonic pseudolipomatosis incidentally found in a series of patients undergoing routine colonoscopy, and we underline the endoscopic pattern and diagnostic difficulties.

The bioburden (blood, protein, pathogens and biofilm) on flexible endoscopes after use is often high and its removal is essential to allow effective disinfection, especially in the case of peracetic acid-based disinfectants, which are easily inactivated by organic material. Cleaning processes using conventional cleaners remove a variable but often sufficient amount of the bioburden. Some formulations based on peracetic acid are recommended by manufacturers for the cleaning step. We performed a systematic literature search and reviewed the available evidence to clarify the suitability of peracetic acid-based formulations for cleaning flexible endoscopes. A total of 243 studies were evaluated. No studies have yet demonstrated that peracetic acid-based cleaners are as effective as conventional cleaners. Some peracetic acid-based formulations have demonstrated some biofilm-cleaning effects and no biofilm-fixation potential, while others have a limited cleaning effect and a clear biofilm-fixation potential. All published data demonstrated a limited blood cleaning effect and a substantial blood and nerve tissue fixation potential of peracetic acid. No evidence-based guidelines on reprocessing flexible endoscopes currently recommend using cleaners containing peracetic acid, but some guidelines clearly recommend not using them because of their fixation potential. Evidence from some outbreaks, especially those involving highly multidrug-resistant gram-negative pathogens, indicated that disinfection using peracetic acid may be insufficient if the preceding cleaning step is not performed adequately. Based on this review we conclude that peracetic acid-based formulations should not be used for cleaning flexible endoscopes.

Colonic pseudolipomatosis is rare and its pathogenesis is still unclear. A number of mechanisms, including mechanical injury during an endoscopic procedure or chemical injury by disinfectant, seem to contribute to its pathogenesis. In our endoscopy unit, pseudolipomatosis occurred in an epidemic pattern after changing the endoscopic disinfectant from 2% glutaraldehyde to peracetic acid compound to decrease the length of endoscope reprocessing time. We assumed that pseudolipomatosis could be a type of chemical colitis produced by the residual disinfectant solution that remained on the surface or in a channel of the endoscope after reprocessing. The aim of this report was to highlight a series of 12 cases of colonic pseudolipomatosis in order to describe the endoscopic and pathological features and discuss the harmful effect of disinfectants as a possible cause of pseudolipomatosis. To identify the cause of the lesions, we systematically reviewed each patient history and the endoscopic and histological features. From March 2004 to February 2005, 1276 colonoscopies were performed and 12 cases (0.94%) of colonic pseudolipomatosis were diagnosed at the Kangnam Sacred Heart Hospital of Hallym University. The pathogenesis of colonic pseudolipomatosis is not well-known, but our experience indicates the endoscopic disinfectant as the probable cause of pseudolipomatosis rather than either mechanical traumatic injury or intraluminal air pressure-related injury.

Segmental colitis associated with diverticulosis (SCAD) is a disease that affects colon harboring diverticula, mostly located in the sigmoid region. It has been considered a rare disease for many years, but new studies may contribute to easier recognition. Although its pathogenesis is not yet well defined, in the past SCAD has been considered a complication of diverticular disease, whilst new endoscopic, histological, and clinical data have encouraged the concept that SCAD includes pathogenetic and therapeutic aspects peculiar to inflammatory bowel diseases. We therefore describe herein current knowledge about this disease, and why it can be considered a truly autonomous entity instead of a complication of diverticular disease.

Pseudolipomatosis refers to optically clear vacuoles that artifactually contaminate specimens, and it most commonly affects the gastrointestinal tract. Pseudolipomatosis closely resembles adult white fat and is of group "A" or "B" when vacuoles have mild or marked variation in size, respectively. Pseudolipomatosis has yet to be reported to occur in the endometrium. Pseudolipomatosis in the endometrium might be easily mistaken for extrauterine adipocytes and misdiagnosed as perforation. We retrospectively reviewed 50 consecutive specimens from endometrial biopsies to determine the prevalence of endometrial pseudolipomatosis and whether pseudolipomatosis was related to perforation. All 50 specimens contained pseudolipomatosis of group "B," and lacked extrauterine tissue. To our knowledge, all patients lacked clinical evidence of perforation at follow-up. Pseudolipomatosis commonly affects specimens from endometrial biopsies and is likely unrelated to perforation. Awareness of pseudolipomatosis is necessary to avoid misdiagnosing uterine perforation.