A sigmoid polyp is a small growth on the inner lining of the sigmoid colon, the S-shaped section of your large intestine that sits just above the rectum in your lower left abdomen. Most sigmoid polyps cause no symptoms and are discovered during a routine colonoscopy. While the majority are harmless, some types can slowly develop into colorectal cancer over years, which is why doctors remove them when they find them.
Where the Sigmoid Colon Is
The sigmoid colon is the final stretch of the large intestine before it connects to the rectum. It curves in an S-shape across the lower pelvis, roughly behind your left hip bone. Because of its position at the end of the digestive tract, stool spends more time in contact with the sigmoid lining than with many other parts of the colon. This prolonged contact is one reason polyps develop here frequently. The sigmoid is also the section most easily reached during a flexible sigmoidoscopy, a shorter screening procedure that examines only the lower colon.
Types of Sigmoid Polyps
Not all polyps carry the same risk. The type is determined by examining the removed tissue under a microscope, and it directly affects what follow-up you’ll need.
- Hyperplastic polyps are the most common type found in the sigmoid and rectum. Small ones (under 10 mm) are generally considered harmless, and finding one typically doesn’t change your screening schedule. However, research has shown that people with a hyperplastic polyp in the left colon have a 49% chance of also having an adenomatous polyp somewhere else in the colon, compared to just 15% in people without one. That’s why doctors sometimes recommend a full colonoscopy even after spotting what looks like a simple hyperplastic polyp during a sigmoidoscopy.
- Adenomatous polyps (adenomas) are the ones that matter most. These are precancerous, meaning they have the potential to turn into cancer if left in place long enough. They come in subtypes: tubular adenomas are the most common and lowest risk, while villous and tubulovillous adenomas carry a higher risk of becoming cancerous. Size matters too. Adenomas larger than 10 mm, or those showing abnormal cell patterns called high-grade dysplasia, are considered advanced.
- Sessile serrated lesions are a newer category that doctors have come to recognize as potentially precancerous. They tend to be flat and can be harder to spot during a colonoscopy. When found in the sigmoid, they’re monitored with the same seriousness as adenomas.
Shape and Appearance
Polyps also vary in how they attach to the colon wall, and this affects how they’re removed. A pedunculated polyp hangs from a stalk, like a mushroom. A sessile polyp is flat or dome-shaped, sitting directly on the lining without a stalk. Some polyps are completely flat or even slightly depressed into the wall, making them harder to detect. Your colonoscopy report will typically describe both the type and shape, because both influence your risk level and follow-up plan.
Symptoms (or Lack of Them)
Most sigmoid polyps produce no symptoms at all. This is exactly why screening colonoscopies exist: you can have polyps for years without knowing it. When symptoms do occur, they tend to come from larger polyps and can include visible blood in your stool, a change in how often you go or in the shape of your stool (narrower than usual), or a slow, invisible bleed that gradually causes iron deficiency anemia. Anemia from a bleeding polyp can show up as fatigue and weakness before you ever notice blood.
What Causes Sigmoid Polyps
Polyps form when cells in the colon lining grow and divide faster than normal. Several factors raise your risk. Age is the biggest one: polyps become increasingly common after 45, which is why screening recommendations start around that age. A family history of polyps or colorectal cancer significantly increases your chances, and certain inherited genetic conditions can cause hundreds of polyps to develop.
Diet and lifestyle play a measurable role. Diets high in red meat (beef and pork), processed meats (bacon, sausage, hot dogs, lunch meats), and fried or fatty foods are linked to higher polyp rates. On the other side, eating more fruits, vegetables, beans, and high-fiber foods like bran cereal is associated with lower risk. Being overweight also raises your chances, and maintaining a healthy weight is one of the more actionable things you can do to reduce your risk.
How Sigmoid Polyps Are Found and Removed
Colonoscopy is the primary tool for both finding and removing sigmoid polyps. During the procedure, a doctor guides a flexible camera through the entire colon. When a polyp is spotted, it’s almost always removed on the spot rather than left for a separate procedure. The tissue is then sent to a lab to determine its type.
The removal technique depends on the polyp’s size and shape. For small polyps under 5 mm, cold snare removal is now the preferred method. The doctor loops a thin wire around the polyp and clips it off without using electrical current. This approach avoids heat-related tissue damage, takes less time, and carries a lower risk of delayed bleeding. For polyps up to about 9 mm that aren’t cancerous, cold snare removal works well too.
Larger polyps or those with a stalk are typically removed with a hot snare, which uses electrical current to cut and seal the tissue simultaneously. For flat polyps larger than about 20 mm, a technique called endoscopic mucosal resection lifts the polyp away from the underlying muscle layer before removing it. Procedure times for these larger removals average around 35 minutes, with a delayed bleeding rate under 1% and perforation (a small tear) occurring in roughly 0.4% to 1.3% of cases.
Recovery After Removal
Recovery from a sigmoid polypectomy is quick, usually just a few days. You’ll need someone to drive you home because the sedation takes time to fully wear off, and you may feel groggy or unfocused for several hours. Most people take over-the-counter or prescription pain medication for a day or two at most.
Some light bleeding in your stool is normal in the days following removal. Heavy or persistent bleeding is not, and warrants a call to your doctor. Rarely, a complication called postpolypectomy syndrome can develop, usually within 12 hours but sometimes a few days later. Symptoms include abdominal pain, fever, and a general feeling of being unwell. This happens when the electrical current used during removal irritates the full thickness of the colon wall. It’s uncommon and typically resolves with conservative treatment, but it needs medical attention. You’ll want to take it easy on your digestive system for a few days after the procedure, sticking to gentle foods while things heal.
Follow-Up Schedule After a Sigmoid Polyp
The type, size, and number of polyps you had removed determine when you need your next colonoscopy. These intervals are based on how likely new polyps are to develop and how quickly they could progress.
If only small hyperplastic polyps (under 10 mm) were found in the sigmoid or rectum, you’re treated essentially the same as someone with no polyps. Your next screening can wait 10 years. If you had one or two small tubular adenomas under 10 mm, follow-up is recommended in about 5 years. Three or four small adenomas also call for a 5-year follow-up colonoscopy.
The timeline shortens for higher-risk findings. Five or more adenomas, any adenoma 10 mm or larger, adenomas with villous features, or high-grade dysplasia all warrant a repeat colonoscopy in 3 years. The same 3-year interval applies to larger sessile serrated lesions or those showing dysplasia. If more than 10 adenomas were found in a single colonoscopy, a follow-up in just 1 year is recommended, along with possible genetic counseling to check for inherited polyposis syndromes.
Once you’ve had two consecutive clear colonoscopies at the recommended intervals, you may be able to return to standard screening every 10 years. Your doctor will use your full history of findings to guide that decision.