Salmonellosis

Salmonella is a gram-negative rod that is ingested with contaminated food or water. Colonic involvement may occur during the course of typhoid fever or as an acute dysentery. Typhoid fever is caused by Salmonella typhi or Salmonella paratyphi . Presenting symptoms include marked pyrexia, arthralgias, malaise, headaches, and right lower quadrant pain. The organism initially involves the reticuloendothelial system, particularly the spleen, mesenteric lymph nodes, and Peyer patches of the terminal ileum. Splenomegaly may occur after 1 week. Gastrointestinal involvement occurs in the second or third week in approximately 50% of cases, but is obscured by other symptoms. Right lower quadrant pain and tenderness are the most common findings. When colonic involvement is present, the barium enema may reveal narrowing and loss of haustration in the cecum caused by edema and spasm, as well as ileal fold thickening and ulceration. Aphthoid ulcers in the ascending colon have also been reported. The ileum is invariably involved. Hemorrhage and perforation occur in 1% to 3% of cases. Symptoms begin to resolve in the fourth week, but relapses are common. Blood cultures are positive during the first week in 90% of patients, and the organism may be isolated from stool cultures during the second and third weeks. Chloramphenicol is the treatment of choice.

In most reported cases, barium enemas have revealed a pancolitis with loss of haustration, often associated with superficial or even deep, so-called collar button ulcers. Thumbprinting has also been reported. Other patients may have extensive small bowel thickening and effacement associated with a pancolitis. Double-contrast studies may reveal punctate mucosal stippling, discrete superficial ulcers, or mucosal granularity. The descending and sigmoid colon are usually involved, with variable proximal extension. Although the rectum generally appears spared radiographically, there may be mild inflammation at endoscopy. A segmental ulcerating colitis in the left colon is rare. Fulminant disease and even toxic megacolon may occur, particularly in older or debilitated persons. Bacteremia is common, and the infection may spread to the gallbladder, bones, lungs, and kidneys.

Shigellosis

Infection with Shigella, a gram-negative rod, may be caused by three species— Shigella flexneri, Shigella dysenteriae, and Shigella sonnei . In the United States, S . sonnei is the offending organism in 70% of cases, whereas in Mexico and Asia, S . dysenteriae is most common. As with salmonellosis, infection may occur in outbreaks, particularly in warm weather. The incubation period is 1 to 3 days, and the presentation is usually similar to that of Salmonella infection. However, shigellosis produces a toxin that causes increased small bowel secretion and watery diarrhea, which lasts several days and then progresses to dysenteric symptoms. Systemic absorption of the toxin may also cause arthritis, pneumonitis, seizures, peripheral neuropathy, microangiopathy, and hemolytic-uremic syndrome. Bacteremia is rare but may cause vascular collapse. Stool cultures are positive within 1 day of onset and may remain positive for months. Toxic megacolon has also been reported. The disease is usually self-limited, lasting 7 to 10 days, but occasionally as long as 1 month. The mortality rate is 10% to 20% in immunocompromised patients or in patients with bacteremia.

Sigmoidoscopy almost always reveals an inflammatory process simulating ulcerative colitis; it varies from mild granularity and erythema to ulceration. Ulceration is more commonly seen than in salmonellosis. Ulcers are usually superficial and of varying size and shape. They are predominantly stellate but may be linear, serpiginous, or aphthoid and are superimposed on a diffusely friable mucosa. In patients with S . dysenteriae infection, the ulcerative phase is most marked in the second and third weeks of the disease, with erythema and edema more prominent in the first week. In many cases, the ulceration is most severe distal to the splenic flexure. Healing ensues with gradually decreasing erythema. The process is initially continuous and pancolonic. During recovery, involvement may become patchy. Although healing is usually complete, some patients may have residual strictures, inflammatory polyps, or even persistent colitis.

Barium enema reveals a predominantly left-sided colitis with deep ulcers, which may have a collar button appearance. Aphthoid ulcers may also be seen.

Campylobacteriosis

Campylobacter is the most common cause of bacterial colitis. This organism has been isolated in 7% to 10% of stool cultures obtained from patients with diarrhea. The offending agent is Campylobacter fetus subspecies jejuni . The disease is usually self-limited, lasting less than 7 days, but symptoms may persist as long as 1 month. In some cases, barium enemas reveal a pancolitis with diffuse granularity and loss of haustration simulating ulcerative colitis, whereas in others, barium enemas have revealed aphthous ulcers, resembling those of Crohn’s disease. The left side of the colon is almost always involved. Hemorrhage, perforation, and toxic megacolon have also been reported as complications. The diagnosis requires culture on selective media; serologic studies may also be helpful for confirmation.

Yersinia Enterocolitis

Infection by Yersinia enterocolitica, a gram-negative rod, tends to be more common in certain regions, such as Japan, Canada, and Scandinavia. Specific strains may be endemic to each of these locations, and these strains have different clinical and pathologic manifestations. Patients younger than 5 years usually present with acute right lower quadrant pain and fever, simulating appendicitis. In contrast, adults may present with acute or protracted fever, pain, and diarrhea evolving over a 4- to 6-week period. Other patients may have associated arthralgias, arthritis, or rashes, such as erythema nodosum or erythema multiforme.

The terminal ileum is invariably involved on barium enemas; the radiographic findings depend on the stage of the disease. The most common findings include small nodules caused by enlarged lymphoid follicles or discrete punctate, aphthoid, or larger oval ulcers. Folds may also be thickened but, unlike in Crohn’s disease, stenosis is not a feature. Colonic changes are manifested by aphthoid ulcers that are predominantly located in the right side of the colon, but left-sided colonic involvement is occasionally noted. The evolution and resolution of these clinical and radiologic abnormalities may require several months. Perforation is rare, but hepatic abscess and septicemia are well-documented complications. Diagnosis requires special culture media or serologic studies. Although no treatment has been proved to be effective, the diagnosis of Yersinia enterocolitis is important primarily for the purpose of excluding other entities.

Colitis Caused by Escherichia coli O157:H7

Escherichia coli strains are the most common cause of traveler’s diarrhea and are usually self-limited. However, the subtype E. coli O157:H7 has drawn increased attention because it is associated with a high morbidity and mortality. Outbreaks of this infection have been noted in Canada; residents of nursing homes have been particularly susceptible. Patients typically present with watery diarrhea (without fever) that progresses over several days to a hemorrhagic colitis. The most serious complication, the hemolytic-uremic syndrome, results from a toxin associated with this infection. The overall mortality may be as high as 33%. The findings on barium enemas are similar to those of ischemic colitis, with thumbprinting, narrowing, and spasm of the involved bowel. Computed tomography (CT) may reveal low-density thickening of the wall caused by edema ( Fig. 58-1 ). Most reported cases have involved the transverse colon, often associated with extension to the right, left, or both sides of the colon. The morphologic changes are caused predominantly by ischemia, and histologic specimens may resemble pseudomembranous colitis. Treatment is supportive, but this diagnosis is important so that isolation procedures can be instituted.

Colitis caused by Escherichia coli O157:H7.

Coronal reformatted CT scan shows marked mural thickening of a redundant sigmoid colon associated with submucosal edema, inflammatory change in the adjacent mesentery, and ascites.

Tuberculosis

Although once considered rare in Western countries, tuberculosis has been increasing in incidence. As a result, reports of gastrointestinal tract involvement have become more common. Patients with AIDS have been noted to be at greater risk than the general population. Although most cases are secondary to a pulmonary source, most patients have no evidence of active or previous pulmonary tuberculosis on chest radiographs. In endemic areas of Asia, most cases of gastrointestinal tuberculosis are caused by ingestion of the bovine bacillus. Colonic involvement is often associated with ileal disease.

Barium studies may reveal abnormalities in the ascending and proximal transverse colon that are indistinguishable from those of Crohn’s disease. It has been suggested that certain abnormalities are characteristic, such as oval or circumferential transverse ulcers, loss of anatomic demarcation between the ileum and the right colon (Stierlin sign), and a right-angle intersection between the ileum and cecum, with marked hypertrophy of the ileocecal valve (Fleischner’s sign). These findings result from the exuberant mural thickening, which tends to be greater than that in Crohn’s disease. Other suggestive features include extremely short segments of involvement of the ileum or cecum, markedly enlarged lymph nodes, particularly with low density on CT, and ascites. However, the most frequent findings include some combination of narrowing, deep ulceration, and mucosal granulation with nodularity and inflammatory polyps. Less common findings include aphthous ulcers, diffuse colitis, segmental colitis distal to the hepatic flexure, and short strictures, simulating carcinoma. Fistulas and sinus tracts are also rare.

The diagnosis can be made on endoscopic biopsy specimens that reveal caseating granulomas or positive cultures for the acid-fast bacilli. However, the yield from endoscopy has been variable. As a result, surgical specimens are sometimes required for a definitive diagnosis. Tuberculous colitis is an important diagnosis because of the potentially catastrophic consequences of administering corticosteroids to these patients because of a mistaken diagnosis of inflammatory bowel disease.

Actinomycosis

Actinomyces israelii is an anaerobic bacterium that occurs as part of the normal flora of the bowel but, when there is contact with tissues not normally exposed to this organism, a pathologic process ensues. Gastrointestinal involvement occurs after infection of mesenteric and peritoneal tissues from penetrating trauma, abdominal surgery, or long-standing intrauterine devices. These patients may develop inflammatory masses and fistulas that involve the colon. Presenting symptoms include a palpable mass, vague abdominal pain, and diarrhea.

Barium enemas may reveal extrinsic masses involving the colon with reactive changes, distortion, and strictures, with or without fistula formation. Fistulas can extend to the skin, where characteristic colonies of sulfur granules may be identified. The ileocecal region is the most common site of gastrointestinal involvement. Many of these patients have a history of prior appendectomy. In contrast, the rectosigmoid colon is the usual site of involvement in patients with intrauterine devices. Ultrasonography and CT may also reveal large inflammatory masses. Surgery is often necessary for a definitive diagnosis and for differentiating these inflammatory masses from neoplasms.

Anisakiasis

Within 12 to 24 hours after the ingestion of raw fish, infestation by larvae of the nematode Anisakis can produce severe abdominal pain, sometimes accompanied by fever, nausea and vomiting, and/or diarrhea. Anisakiasis has a predilection for the stomach and small intestine, but the colon may occasionally be involved by this infection. Eosinophilia is not often present in the serum but is invariably identified on biopsy specimens. The ascending colon and, less commonly, the transverse colon are involved; barium enemas may reveal segmental thumbprinting of the affected bowel. The diagnosis of anisakiasis can be suggested when double-contrast barium enemas show the actual larvae as thin, linear filling defects 12 to 20 mm long and 0.7 mm wide at the proximal portion of the diseased segment of bowel. Serologic studies may be performed to confirm the diagnosis. The worm is present in the stool in less than 25% of cases. The process is self-limited, usually lasting 7 to 10 days.

Amebiasis

Colonic amebiasis is rare in the United States. The cysts are ingested and subsequently develop into the invasive trophozoite. This organism is harbored by 20% of the world population. Infestation by this protozoan may vary from the carrier state to fulminant colitis, and symptoms may be indolent or acute. Spread to the liver and then the lungs may result in abscesses in either of these organs.

Colonic amebiasis is usually an acute ulcerative colitis (95%) manifested by skip lesions, although the intervening bowel may be involved to a much lesser extent. At times, the affected bowel is characterized by short regions of involvement with marked granulation (ameboma). Such amebomas are seen in approximately 10% of cases and are usually located in the right side of the colon. Although diffuse colitis is not unusual, the right side of the colon tends to be more severely involved. Barium enemas usually reveal deep ulcers or bowel wall edema, but some patients may have aphthous ulcers, discrete ulcers appearing as marginal defects, or granularity with barium flecks. The terminal ileum is invariably spared. The coned cecum is a suggestive but nonspecific finding. Residual deformity and stricture formation may occur, even after appropriate therapy. Less than 1% of patients present with toxic megacolon, and approximately 3% present with typhloappendicitis.

The diagnosis of amebiasis is usually established by the presence of trophozoites in the stool or on rectal smear. Serologic studies are also sensitive. When amebiasis is suspected, trial therapy may be warranted, even if the diagnosis is not confirmed; the disease may progress rapidly if these patients are inappropriately treated with corticosteroids for presumed inflammatory bowel disease.

Schistosomiasis

Schistosomiasis belongs to the trematode or fluke group of worms; different strains are endemic to specific geographic areas. Schistosoma mansoni is found in the United States, Puerto Rico, and the tropics. Schistosoma haematobium is the primary form in Africa and southern Asia, and Schistosoma japonicum usually occurs in eastern Asia. Mixed infection with S . mansoni and S . haematobium is not uncommon, particularly in Egypt. The larva penetrates the skin, where it enters the systemic circulation. It eventually reaches the liver and matures into the adult form. Upstream migration occurs through the portal venous system to the colon, where the worms invade the bowel wall and lay eggs. Portal hypertension with secondary hepatosplenomegaly is frequently associated. Although some patients may develop a pancolitis, S . mansoni has a predilection for the inferior mesenteric vein and left side of the colon, S . japonicum infects the superior mesenteric vein and right side of the colon and terminal ileum, and S . haematobium infects the hemorrhoidal veins and rectum and urinary tract. Most patients present with bloody diarrhea, but some may have chronic abdominal pain, intermittent diarrhea, and a palpable abdominal mass.

Barium enema examinations may reveal nonspecific colitis involving a variable extent of colon, with narrowing, loss of haustration, and ulceration. However, a hallmark of this disease is the presence of inflammatory polyps as a result of granulation reaction to the deposition of eggs in the bowel wall. Another suggestive finding is calcification of the bowel wall or liver, which is usually associated with S . haematobium but also with S . japonicum . CT is particularly sensitive to these changes. The diagnosis can be established by demonstrating the eggs in biopsy specimens or in the stool. Eosinophilia is frequently present.

Strongyloidiasis

The nematode Strongyloides stercoralis also gains entrance through the skin. It spreads to the lungs, ruptures into the tracheobronchial tree, and is subsequently ingested. The primary sites of involvement are the stomach, duodenum, and proximal small bowel; and a chronic host-parasite relationship ensues. In most cases, eggs are passed into the stool. However, in patients with decreased immunity, the eggs progress to the filariform larval stage and invade the portal system, producing a repeated cycle or autoinfection. The excess parasite load results in a distal accumulation of filariform larvae with subsequent colonic involvement. Because of the setting of severe debilitation, this process is often fatal. Barium enemas typically reveal findings of a diffuse ulcerative colitis. Aphthoid ulcers may be identified in the colon. Fistulas and sinus tracts may also be present. Eosinophilia is the rule, but the diagnosis requires identification of cysts, larvae, or both, in the stool.

Trichuriasis

The whipworm Trichuris trichiura predominantly involves children in tropical areas. The worm is minimally invasive but invades the mucosa, with resultant bleeding, anemia, diarrhea, malaise, and cramps. Intussusception and rectal prolapse are common; the adherent worms serve as the lead point for this intussusception. Eosinophilia is usually present. The barium enema shows clumping and granularity of the barium because of excessive production of mucus. The worms are identified as wavy, linear lucencies 3 to 5 cm in length, sometimes terminating in a ring shape, with a central barium collection.