polypus

Polypus, also spelled polyp, is a growth projecting from a mucous membrane. In modern medical usage, a polyp is a lesion that protrudes from mucosa into a hollow organ or duct. Polyps occur in many parts of the body, most commonly in the nasal passages and sinuses, colon and rectum, stomach, uterus, and bladder. They vary in size and shape, being pedunculated (on a stalk) or sessile (broad-based).

Histologically, polyps may be inflammatory, hyperplastic, hamartomatous, familial adenomatous, or adenomatous, with some having potential for malignant transformation, particularly in the colon where adenomatous polyps are considered precancerous lesions. Nasal polyps are commonly associated with chronic rhinosinusitis or allergic disease; colorectal polyps may be found incidentally during screening colonoscopy. Most polyps are asymptomatic but can cause bleeding, obstruction, or anemia depending on their site.

Diagnosis is typically by endoscopic examination with biopsy for histology, supported by imaging when needed. Treatment usually involves removal of the polyp (polypectomy), often during endoscopy; removal reduces the risk of progression and relieves symptoms. Surveillance colonoscopy is commonly recommended after removal of colorectal polyps to detect recurrent lesions or new growths.

In zoology, polypus can refer to the polyp stage of certain cnidarians (for example, hydras and sea anemones), a body form that is typically sessile and asexual. The term is largely historical in medicine but remains in use in some contexts.