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Cecum and Colon

The radiological abnormalities to be considered are: foreign bodies, tumor or stricture, colitis, obstruction, diverticulosis, and polyps.

Ingested Materials. Malnutrition results in anemia: to relieve the hunger and perhaps to obtain minerals, children may eat almost anything, including dirt (pica and geophagia). In some communities they are even fed soil. This can produce unexpected densities on radiographs of the abdomen or echoes on ultrasonography. The findings will depend very much on the quantity ingested but, for example, one 16-year-old girl in Nigeria ate a 2 pound (1-kilogram) bag of sand and 48 hours later her colon was as opaque as if she had ingested barium or had a barium enema (Fig. 44.8 A). Pica seldom causes obstruction but it may produce abdominal symptoms, and result in diarrhea or constipation. In many patients, however, it will be a chance finding on a plain abdominal film taken for some other reason.

Tumors and Strictures. Tumors and strictures are common radiological abnormalities on contrast examinations of the large bowel in the tropics, but neither is likely to be malignant (see Chapter 43 on Geographic Variations of Malignant Neoplastic Diseases). A tumor, particularly in the cecum, is most probably an ameboma or helminthoma. Ileocecal intussusception may cause an intracecal tumor and colocolic (or ileocolic) intussusception may cause a tumor anywhere in the colon. Polyps of any variety other than those due to schistosomiasis are rare. Distortion of the cecum may be caused by tuberculous lymphadenopathy producing a "pseudotumor" by extrinsic pressure. An appendix abscess can also cause a similar deformity, but appendicitis is still relatively rare in the tropics, although increasing in frequency. A tubo-ovarian abscess is more common. Shrinkage of the cecum is caused by either amebiasis or tuberculosis, but either may also appear as a "mass", the granulomatous ameboma or tuberculoma which is radiologically and clinically very similar to carcinoma. However, intrinsic cecal malignancy is unusual in the tropics.

A stricture or narrowing of any part of the colon is most likely due to amebiasis or tuberculosis. Other possibilities are schistosomiasis, helminthoma, or adhesions following peritonitis or gynecological infection. Malignancy is unlikely, but the differential diagnosis can be very difficult because both an ameboma and a tuberculoma can produce an annular ("apple-core" or "napkin ring") constriction or form a mass indistinguishable from carcinoma (see Fig. 43.6). The presence of colitis or other changes of amebiasis or tuberculosis elsewhere in the colon may be helpful, but, of course, the two conditions may coexist. In most countries a therapeutic trial is not only of diagnostic help but a wise precaution preoperatively. It is in such cases that knowledge of the rarity of bowel malignancy in the tropics will guide the interpretation of the radiological findings, and this should also be remembered if the patient has recently lived or even traveled in the tropics.

Colitis. the differential diagnosis of any colitis, lengthy or interrupted, in a patient in the tropics must include amebiasis, schistosomiasis, and tuberculosis. The possibility of idiopathic ulcerative colitis is slight. Ulcerative colitis is seen in India but is less severe than in Europe or in North America. It is still exceedingly uncommon in most of Africa, but may be occurring somewhat more often in some regions (Fig. 44.8 B). However, in most of the tropics, amebiasis is the most likely cause of bowel ulceration and it may mimic idiopathic ulcerative colitis even to the extent of causing a toxic megacolon or eventually fibrosis and contraction (see Chapter 1 on Amebiasis).

In many tropical countries it is customary to give enemas to children and they are used by adults also with almost ritual fervor. (For example, the late Mahatma Ghandi had an enema almost every day, either self-administered or given by one of his attendants. He regarded it as evidence of his special friendship when offering to administer an enema to others). Up to 50% of some populations may admit to habitual use of enemas, and some adults have given themselves over 200 enemas a year. In many countries in Africa, traditional healers use enemas for anything wrong below the waist. One mixture is of yellow and black beetles, which are baked, powdered, and blown into the bowel. This mixture is very acidic, and causes septicemia. Many other enemas contain herbs and very few are isotonic, so that colitis is a frequent result (often evoking yet further "curative" enemas). After continued use of enemas, the pelvic colon and lower descending colon may be narrowed and show loss of haustration as well as ulceration (Fig. 44.8 C, D). These findings may be mistaken for either ulcerative colitis or Crohn's disease unless it is remembered that neither is likely in the tropics.




Fig. 44.8. (A) The colon of a 16-year-old Nigerian girl, 48 hours after she had eaten 2 pounds of sand. Pica must be remembered if otherwise unexplained opacities are present in the bowel at any level. (B) A rare disease: ulcerative colitis in a young African female (from Zimbabwe). The colitis in this patient was "idiopathic" without any evidence of parasites or infection: this is almost as surprising as the ulcerative colitis, which is very uncommon in Africans. (C,D) Repeated enemas with various herbs may result in colitis which must be distintinguished from amebiasis, and all other causes of colonic ulceration. These are both patients from southern Africa: it is radiologically and clinically very difficult to be sure of the correct diagnosis (A courtesy of Dr. B.T. Jackson and the B.M.J. Foundation 1992).(E) Recurrent volvuus may result in a persistent constriction, as in the sigmoid colon of this African from Zimbabwe. (F) A diagram of a "double volvulus" in which both the small and large intestine have become twisted. On a plain radiograph, the combination of small and large intestine dilatation makes this recognizable. (C and D courtesy of the University of Cape Town Radiology Library).

For those who must administer a contrast enema, a word of warning is necessary. In Sri Lanka and elsewhere in southern India, patients, commonly children or their embarrassed parents, complain of beetles "zooming away" from the child's newly passed stool. The local name is kurumini mandama or beetle marasmus. Dung beetles (Scarabaeidae, family Coleoptera, subfamily Coprinae) come into contact with the children when they are playing outside the home. Whether the beetle is swallowed by the child and completes the life cycle in the gut or gains access via the anus is undecided: the common belief is that the beetle survives the transition through the bowel. It is worth noting that this was described in the nineteenth century medical literature and was regarded as a sign of mental disturbance. So far as we know, the beetle has not actually been demonstrated on a contrast enema or, even more interesting, seen at the end of an endoscope. But we have found only one modern reference to this phenomenon and must reserve judgment.

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