When trying to figure out the significance of a symptom you may be having, it's helpful to think in terms of what's the most likely diagnosis and what's the most lethal. Hopefully they are not the same. For example, the most likely cause of red blood in the stool is hemorrhoids, but the most lethal is colon cancer.
Taking a close look at your stool can tell you a lot about what's going on in your intestines and can lead you to make the right changes to improve your digestive and overall health. If you know what to look for, it's like reading tea leaves! I tell my patients that if they pay close attention to what's going on in the bowl, they might not need my services.
Here's a guide to some of the most likely – and most lethal – conditions that can lead to changes in the shape, size, smell and shade of your stool.
Insufficient fiber in the diet, diverticulosis, bowel spasm or excessive straining are common causes of a change in stool shape. Diverticulosis causes pothole-like craters in the lining of the colon, as well as a narrowing of the internal diameter of the colon due to wall thickening. The result is narrow, pellet-like stools that often fall apart in the bowl and can be difficult to expel. Other associated symptoms of diverticulosis include a dull ache in the lower abdomen, a feeling of incomplete evacuation even though you may be having multiple bowel movements, and lots of gas and bloating. Endometriosis, uterine fibroids, masses in the abdomen or tumors in other organs, like the ovaries or bladder, can cause thin stools due to external compression of the colon. Colon cancer definitely needs to be excluded by a colonoscopy in anyone experiencing new onset of pencil-thin stools, which can occur as a tumor gets larger and grows inward, reducing the colonic diameter.
Size matters. Small, hard stools are typical in people eating a low-fiber Western diet, and are associated with a higher risk for ultimately developing diverticulosis and colon cancer. Constipation is often associated with small, difficult-to-pass stools, and people suffering from constipation-predominant irritable bowel syndrome (IBS) are particularly prone to having small stools. A high-fiber diet or regular use of a bulking agent like psyllium husk will lead to larger, softer stools in most people, making defecation easier. Even though a fiber-deficient diet is the most likely culprit, colon cancer is again on the list as most lethal.