Colonoscopy allows gastroenterologists to find and remove polyps, which are small growths on the colon lining. Most polyps discovered are safely removed immediately, a process called polypectomy. However, physicians may deliberately choose not to remove a polyp, or only take a biopsy, due to patient safety concerns or the complexity of the lesion. This decision prevents immediate complications like bleeding or perforation, ensuring the patient receives the most appropriate, specialized treatment.
Polyp Size, Morphology, and Location
The physical characteristics of a polyp often dictate whether standard removal is feasible. Polyps measuring more than two centimeters are classified as “large.” Attempting to remove large polyps with standard techniques significantly increases the risk of complications, such as perforation or major bleeding, because the blood vessels supplying these growths are more substantial.
The shape, or morphology, of the polyp also affects safe removal. Pedunculated polyps, which have a distinct stalk, are generally easier to snare and remove. Conversely, sessile polyps, which are flat and attached directly to the colon wall, or laterally spreading tumors, are much harder to excise cleanly. The flat nature of these lesions makes it difficult to distinguish their margins and increases the risk of damaging the underlying muscle wall.
The location of the polyp within the colon is also a determining factor in the decision to defer removal. The wall of the right colon, specifically the cecum and ascending colon, is naturally thinner than the left side, making these areas particularly vulnerable to perforation. Polyps situated near anatomical landmarks, such as the appendix orifice or the ileocecal valve, are also difficult to approach safely.
When a large or morphologically challenging polyp is encountered, a gastroenterologist may defer the procedure until the patient can be scheduled for an advanced technique, such as Endoscopic Mucosal Resection (EMR) or Endoscopic Submucosal Dissection (ESD). These specialized methods often require additional equipment and time, and are generally performed by endoscopists with specialized training. EMR involves injecting a fluid cushion beneath the lesion to lift it away from the muscle layer, creating a protective barrier against perforation before removal.
Patient Health and Procedural Risk Factors
Factors external to the polyp, relating to the patient’s overall health and procedural conditions, can necessitate deferral of polypectomy. A major concern is the patient’s use of anticoagulant or antiplatelet medications, commonly referred to as blood thinners. Medications like warfarin or Direct Oral Anticoagulants (DOACs) significantly increase the risk of delayed post-polypectomy bleeding, particularly for larger polyps.
If patients must continue these medications due to a high risk of stroke or heart attack, the gastroenterologist must balance the risk of a clot against the risk of hemorrhage. If the patient could not safely stop their anticoagulant prior to the colonoscopy, the physician will frequently defer the polypectomy until the patient can be safely managed off the medication, often in consultation with the prescribing physician.
Underlying comorbidities, especially severe heart or lung conditions, introduce another layer of risk. Patients with fragile cardiovascular or respiratory systems are more susceptible to complications from sedation and the stress of a prolonged procedure. Since removing a large or complex lesion extends the duration of sedation, deferring the polypectomy to a specialized, planned setting may be the safest course of action to avoid serious cardiopulmonary events.
Inadequate bowel preparation can also make polypectomy unsafe. Residual stool or fluid obscures the visualization of the colon wall, reducing the ability to accurately identify the polyp’s margins. Poor visibility makes a clean, complete removal virtually impossible. When the bowel preparation is poor, the doctor may choose to stop the procedure and reschedule it, insisting on a more thorough preparation to ensure a clear field of view.
Suspicious Lesions Requiring Specialized Treatment
A polyp is not removed if its appearance strongly suggests it has progressed into an invasive cancer. When a lesion exhibits visual characteristics of deep invasion, the gastroenterologist will deliberately perform only a biopsy rather than a full resection. Visual cues for deep invasion include ulceration, an irregular or depressed surface, or a firm, stiff appearance upon contact.
A particularly important indicator is the “non-lifting sign,” which occurs when the physician injects fluid beneath the lesion and the polyp fails to lift away from the muscle layer. This lack of elevation is often caused by dense scar tissue resulting from the cancer invading the deeper layers of the colon wall. For lesions highly suspicious for invasive cancer, the immediate goal is to obtain a tissue sample to confirm the diagnosis and determine the depth of invasion.
Endoscopic removal of a deeply invasive lesion is inadequate because it cannot ensure the complete removal of cancerous tissue. Furthermore, an incomplete endoscopic removal can disrupt the surrounding tissue planes, making a subsequent surgical procedure more difficult. Leaving the lesion intact allows for detailed surgical consultation and planning for definitive treatment, typically a colectomy.
Colectomy involves surgically removing a segment of the colon containing the lesion. This ensures the best possible oncological outcome, as the surgeon can remove the entire tumor along with surrounding lymph nodes, which is the standard of care for invasive colorectal cancer.