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Differential Diagnosis

Localization of the pathological and radiological changes in giardiasis to the duodenum and jejunum is a great help in differential diagnosis, since many other gastrointestinal diseases are thus excluded. The principal differential problems include other parasitic diseases such as strongyloidiasis and hookworm disease, as well as other inflammatory diseases of the proximal small bowel such as Whipple's disease and eosinophilic enteritis. Intestinal lymphangiectasia, lymphoma, amyloidosis, vascular diseases and pancreatitis may rarely be considered, but are unlikely to be confused with giardiasis. These latter diseases may have more pronounced changes in the mucosal fold pattern, but less extensive spasm, fragmentation and secretions than are seen in giardiasis.

The disease which most closely resembles giardiasis is strongyloidiasis, and indeed, in many patients, the radiographic appearance of mucosal fold distortion from edema, inflammation, spasm and increased secretions may be so similar in the two diseases that it is impossible to differentiate them on this basis. In other patients with strongyloidiasis, there is a greater tendency for changes of malabsorption with dilatation of the small bowel; in chronic cases, especially those with repeat or autoinfections, there may be pipestem stenosis and ulceration of the proximal small bowel, and occasionally inflammatory changes in the colon, none of which occur in giardiasis. Autoinfections generally prolong the disease to produce a low-intensity but chronic state, a common situation in strongyloidiasis. However, hyperinfection, which occurs in immunosuppressed patients, usually leads to a progressive, severe, often fatal malabsorptive diarrhea.

In giardiasis where the so-called "deficiency pattern" is prominent, the differential diagnosis will include other causes of malabsorption, such as sprue and celiac disease, but these entities would rarely simulate the overall roentgen pattern seen in giardiasis, especially when the prominent inflammatory changes and spasm in the duodenum and jejunum are properly evaluated.

Finding cysts and trophozoites of G. lamblia in stools or duodenal aspirates confirms the diagnosis. A therapeutic trial with Atabrine or Flagyl or other appropriate medication resulting in clinical and radiographic improvement likewise confirms that the symptoms and radiographic changes were indeed caused by giardiasis.

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