Gastrointestinal and Hepatobiliary Systems: IBD, Polyps, and Familial Colorectal Cancers

Fecal lactoferrin and calprotectin

Stool biomarkers that test positive in inflammatory bowel disease (IBD) but negative in irritable bowel syndrome (IBS).

Ulcerative Colitis

A chronic inflammatory condition of the colon that always originates in and involves the rectum with continuous mucosal spread, characterized by crypt abscesses, pseudopolyps, and p-ANCA positivity.

Lead pipe appearance

The earliest radiological imaging finding in ulcerative colitis, caused by mucosal granularity and complete loss of colonic haustrations.

Truelove and Witts' classification

A clinical scoring system utilized to classify the severity of ulcerative colitis episodes.

Crohn's disease

A transmural, granulomatous inflammatory disease featuring non-caseating granulomas, skip lesions, and ASCA positivity, most commonly involving the terminal ileum.

Cobblestone appearance

The earliest imaging appearance in Crohn's disease, produced by the coexistence of aphthous ulcers and intersecting serpentine ulcers.

String sign

A radiological finding describing marked narrowing and stricture formation in the distal ileum, characteristic of Crohn's disease and intestinal tuberculosis.

Comb sign

A radiological sign produced by hypervascularity and engorgement of the vasa recta, indicating active Crohn's disease.

Montreal classification

A classification system for Crohn's disease based on age at diagnosis, location of ulcer, behavior of ulcer, and perianal disease status.

Ustekinumab

A targeted biologic agent effective for both forms of inflammatory bowel disease (Ulcerative Colitis and Crohn's disease) as well as psoriatic arthritis.

Peripheral manifestations of IBD

Extraintestinal manifestations of inflammatory bowel disease that parallel and respond to the treatment of gut inflammation, including peripheral migratory polyarthritis, erythema nodosum, and episcleritis.

Central manifestations of IBD

Extraintestinal manifestations that run an independent course and do not respond to gut treatment, including axial arthritis (ankylosing spondylitis), pyoderma gangrenosum, primary sclerosing cholangitis (PSC), and uveitis.

Renal stones

The most common extraintestinal manifestation associated specifically with Crohn's disease.

Hyperplastic polyp

The most common non-neoplastic polyp of the digestive tract, caused by cell overproduction and hallmarked by serrations confined strictly to the superficial $1/3$ mucosal layer.

Serrated sessile adenoma (SSA)

A premalignant colonic lesion histologically distinguished from a hyperplastic polyp by having serrations extending throughout the entire depth and thickness of the crypts.

Solitary Rectal Ulcer Syndrome (SRUS)

An inflammatory polyp of the rectum that classically presents with rectal bleeding and mucus discharge.

Villous adenoma

An adenomatous polyp carrying a poor prognosis ('villous = villain') due to high malignant risk, for which polyp size serves as the most important prognostic marker.

Juvenile polyposis syndrome

A hamartomatous polyposis syndrome linked to SMAD 4 gene mutations, presenting with cystic polyp spaces, rectal bleeding in young children, and pulmonary arteriovenous malformations (AVMs).

Peutz-Jeghers syndrome

An autosomal condition caused by STK 11 (LKB-1) mutations, featuring arborizing tree-like hamartomatous polyps that act as lead points for intussusception, mucocutaneous pigmentation, and a $100\%$ risk of pancreatic adenocarcinoma.

Cowden syndrome

A hamartomatous syndrome caused by a PTEN mutation on chromosome $10$, featuring benign trichilemmomas and a high risk of 'BET' malignancies: Breast, Endometrial, and Thyroid cancers.

Cronkhite-Canada syndrome

A sporadic, non-hereditary polyposis condition featuring hamartomatous polyps accompanied by ectodermal dysplasia.

Tuberous Sclerosis

A multi-organ hamartoma syndrome caused by mutations in Hamartin (chromosome $9$) and Tuberin (chromosome $16$).

Bannayan-Riley-Ruvalcaba syndrome

A hamartomatous polyposis disorder characterized clinically by macrocephaly and developmental delay.

Familial Adenomatous Polyposis (FAP)

An autosomal dominant syndrome caused by chromosome $5\text{q}$ APC gene mutations, leading to thousands of polyps, a $100\%$ chance of left-sided colon cancer by puberty, and ampullary cancer of the pancreas.

AK-53 sequence

The multi-step loss-of-function tumor suppressor pathway driving colorectal adenocarcinoma: APC (chromosome $5$) initiates early adenoma, K-RAS (chromosome $12$) drives late adenoma, and p-53 (chromosome $17$) drives adenocarcinoma.

Gardner's syndrome

A variant of FAP described as a 'garden of tumors,' presenting with supernumerary teeth, osteomas, fibromas, and congenital hypertrophy of the retinal pigment epithelium (CHRPE).

Turcot syndrome

A variant of familial polyposis associated with primary brain tumors ('turban: tumors in head'), including medulloblastoma (with drop metastases) and glioblastoma multiforme.

Hereditary Nonpolyposis Colorectal Cancer (HNPCC)

An autosomal dominant disorder (Lynch syndrome) caused by DNA mismatch repair defects in MLH-1 and MSH-2, carrying an $80\%$ lifetime risk of predominantly right-sided, bleeding colorectal cancers without preexisting diffuse polyposis.