AIM To evaluate the prevalence of nodular lymphoid hyperplasia(NLH) in adult patients undergoing colonoscopy and its association with known diseases. METHODS We selected all cases showing NLH at colonoscopy in a three-year timeframe, and stratified them into symptomatic patients with irritable bowel syndrome(IBS)-type symptoms or suspected inflammatory bowel disease(IBD), and asymptomatic individuals undergoing endoscopy for colorectal cancer screening.Data collection included medical history and final diagnosis. As controls, we considered all colonoscopies performed for the aforementioned indications during the same period.RESULTS One thousand and one hundred fifty colonoscopies were selected. NLH was rare in asymptomatic individuals(only 3%), while it was significantly more prevalent in symptomatic cases(32%). Among organic conditions associated with NLH, the most frequent was IBD, followed by infections and diverticular disease. Interestingly, 31% of IBS patients presented diffuse colonic NLH. NLH cases shared some distinctive clinical features among IBS patients: they were younger, more often female, and had a higher frequency of abdominal pain, bloating, diarrhoea, unspecific inflammation, self-reported lactose intolerance and metal contact dermatitis. CONCLUSION About 1/3 of patients with IBS-type symptoms or suspected IBD presented diffuse colonic NLH, which could be a marker of low-grade inflammation in a conspicuous subset of IBS patients. AIM To evaluate the prevalence of nodular lymphoid hyperplasia (NLH) in adult patients undergoing colonoscopy and its association with known diseases. METHODS We selected all cases showing NLH at colonoscopy in a three-year timeframe, and stratified them into symptomatic patients with irritable bowel syndrome (IBS) -type symptoms or suspected inflammatory bowel disease (IBD), and asymptomatic individuals undergoing endoscopy for colorectal cancer screening. Data Collection included medical history and final diagnosis. As controls, we considered all colonoscopies performed for the to indications during the same period .RESULTS One thousand and one hundred fifty colonoscopies were selected. NLH was rare in asymptomatic individuals (only 3%), while it was significantly more prevalent in symptomatic cases (32%). Among organic conditions associated with NLH, the most frequent was IBD , followed by infections and diverticular disease. Interestingly, 31% of IBS patients presented diffuse c olonic NLH. NLH cases shared some distinctive clinical features among IBS patients: they were younger, more often female, and had a higher frequency of abdominal pain, bloating, diarrhea, unspecific inflammation, self-reported lactose intolerance and metal contact dermatitis. 1/3 of patients with IBS-type symptoms or suspected IBD presented diffuse colonic NLH, which could be a marker of low-grade inflammation in a conspicuous subset of IBS patients.