Question: I am doing my best to prepare for the ICD-10 coding changes, but I’m still struggling with some similar-sounding conditions. I’m wondering what the difference is between diverticulosis and diverticulitis. How should I code these conditions? Illinois Subscriber Answer: Diverticulosis (such as K57.30, Diverticulosis of large intestine without perforation or abscess without bleeding) occurs when 3 mm – 3 cm “diverticula,” or pockets, poke out from the colon’s muscle wall. This happens most often in the sigmoid colon where there is the most pressure and is most common in people 40 years of age or older. Other risk factors are low-fiber diets, constipation, and dehydration. As many as 80 percent of people with diverticulosis don’t know they have it, and physicians sometimes discover it while they are performing diagnostic tests related to other GI signs and symptoms. Diverticulosis becomes more problematic when small perforations occur within the pockets so that they become infected and inflamed, creating diverticulitis. Because the small blood vessels at the edge of the diverticuli are fragile, another common problem is bleeding (such as K57.31, Diverticulosis of large intestine without perforation or abscess with bleeding). Patients with diverticulitis (such as K57.32, Diverticulitis of intestine, part unspecified, without perforation or abscess without bleeding) have abdominal pain and fever. About 80 percent of these patients respond to treatments such as temporary liquid or very low-fiber diets, antibiotics, and without CT-guided percutaneous drainage. If something in the E/M service or CAT scan indicates abscess or perforation or both, other ICD-10 codes pertain. Bleeding from diverticulosis can be very severe, often requiring emergency procedures to stop the bleeding. Fortunately, the bleeding usually stops spontaneously. Some residents, however, require colon resection surgery.