Hello, Flat stool in most of the cases is very much normal. A few causes of flat or narrow stools are irritable bowel syndrome, constipation, colon polyps, benign prostatic hyperplasia, fecal impaction, hemorrhoids, rectal ulcers and colorectal cancer which is very rare. To those who come to my clinic with similar symptoms, I recommend to contact a physician if there is any recent diet change and if the flat stool is associated with abdominal pain and also blood in stools. If the flat stools occur randomly it s not a matter of concern. If no other symptoms like fever, blood in stool, abdominal pain, weight loss are present, you can relax. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Pallavi M., Anesthesiologist