In the later stages, the cecum characteristically loses its normal sac-like appearance and gradually narrows until it becomes cone-shaped or pyramidal in outline (Figs. 1.23, 1.24, 1.25,1.26). The ileocecal valve often moves downward and may appear to lie close to the tip of the cecum. The valve is invariably thickened, rigid and fixed in an open position, allowing reflux to occur in virtually all barium enema examinations, unlike tuberculosis in which reflux is uncommon. The combination of a conical cecum with a normal-appearing terminal ileum helps to rule out other entities, such as tuberculosis and Crohn's disease, in most patients, although the terminal six inches of ileum may be involved in 10% or more of patients with severe cecal amebiasis.

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Fig. 1.23 Cecal amebiasis with classical conical or pyramidal deformity of the cecum and marked thickening and fixation of the ileocecal valve in two different patients (A and B). There is also shortening of the ascending colon in patient (A). In both patients, there is reflux into a normal terminal ileum which permits differentiation in most patients from Crohn's disease, tuberculosis, and other inflammatory diseases of the right colon and ileocecal area. (C) Gross specimen of the ascending colon, cecum and terminal ileum of another patient with amebiasis showing several ulcers within a contracted cecum as well as marked thickening of the ileocecal valve and the cecal wall. The ileum is normal. AFIP 113157-05011.

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Fig. 1.24 Amebiasis of the cecum and ascending colon in 4 patients. (A) Multiple edematous, confluent wall masses resulting in a conical shaped cecum. There are milder segmental lesions in the transverse colon. (Courtesy of Drs. Kimura and Stoopen, Mexico City.) (B) The cecum is markedly shrunken and deformed, and there are two separate skip areas of inflammatory stenoses involving the midascending colon and cecum. There are also ulcers in the cecum and lateral wall of the hepatic flexure. The cecal wall is thickened in the region of the ileocecal valve, but there is no significant reflux into the distal ileum. (C) Multiple amebomas (arrows) have produced filling defects in the cecal tip and ileocecal valve area. There is reflux into the slightly involved distal ileum because of the indurated, fixed ileocecal valve. (D) The cecum is short, narrow and conical (arrows) with no visible haustra.The ileocecal valve is patulous and reflux has occurred into a normal-appearing terminal ileum. Skip areas, stenoses, deep ulcers, and involvement of the cecum and right colon are typical of two granulomatous diseases of bowel, namely Crohn's disease and tuberculosis. In both of these diseases, the distal ileum is commonly involved, which is unusual in amebiasis.

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Fig. 1.25 Chronic amebiasis with acute exacerbation showing severe involvement of the cecum, ascending colon, and terminal ileum (A and B). Numerous deep ulcers have undermined the mucosa and extended deep into the submucosa and muscularis. Several fistulas extend from the tip of the cecum, which is deformed in a typical conical or pyramidal shape. The ileocecal valve is fixed and incompetent as it is in most patients with amebiasis. In (B) there is also fixation, rigidity, ulceration, and a tubular appearance of the terminal foot of ileum, as well as marked spasm of the transverse colon. Such pronounced involvement of the ileum is unusual in amebiasis, occurring in about 10% of patients with colonic amebiasis. (Courtesy of Dr. Julio Astacio, San Salvador.) (C) Gross specimen from fatal amebiasis showing numerous large, ragged, deep ulcers in the ascending colon and cecum with marked thickening and deformity of the cecal wall. Note the severe thickening around the ileocecal valve and ulceration and denudation of mucosa in the distal ileum, an uncommon finding in amebiasis. AFIP 196764-1.

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Fig. 1.26 (A) Advanced amebiasis of the right colon and cecum with involvement also of the ileocecal valve and terminal ileum. There is marked thickening and deformity of the wall of the cecum, ascending colon and hepatic flexure; numerous ulcers are present. The tip of the cecum is deformed in typical conical or pyramidal fashion. The ileum is rigid and tubular. There are numerous irregular radiolucent defects in the barium column in the hepatic flexure from ragged mucosal remnants remaining after most of the mucosa has been denuded through severe ulceration. This appearance in some patients with chronic amebiasis can mimic pseudopolyp formation from mucosal tag remnants seen in chronic ulcerative colitis. (B) "Sea anemone" type of ulcerated mucosa in chronic amebic colitis. A shaggy yellow-white slough fills the large ulcers. Removal of this slough exposes the involved muscularis. There are ragged mucosal remnants which may project into the bowel lumen to cause irregularly shaped filling defects, such as those seen in (A). AFIP 68-2723-3. (From Hunter's Tropical Medicine, ed 5, Philadelphia, Saunders, 1976).