Laboratory Studies
Serum protein levels
The most prevalent laboratory finding in intestinal lymphangiectasia is hypoproteinemia. This typically manifests as hypoalbuminemia, and patients may also exhibit lymphocytopenia and hypogammaglobulinemia, involving immunoglobulin A (IgA), immunoglobulin G (IgG), and immunoglobulin M (IgM). Cholesterol levels, however, are not typically elevated in this condition.
Alpha1-antitrypsin levels
In the analysis of random dry stools, alpha1-antitrypsin (AAT) levels are indirect indicators of protein leakage in the gastrointestinal (GI) tract. AAT is resistant to degradation by intestinal proteases and is excreted intact in the stool. However, although measuring stool AAT can be a useful initial screen for protein loss, several studies have revealed a limited correlation between stool AAT and its clearance measurement. This is partially attributed to the variable degradation of AAT in different environments, with higher breakdown observed in conditions where the pH level is less than 3, such as in the stomach or small bowel during states of hyperacidity.
The most precise test for assessing protein loss in the GI tract involves the direct measurement of AAT clearance from plasma. Values exceeding 24 mL/day in patients without diarrhea (as diarrhea can increase AAT clearance) and surpassing 56 mL/day in those with diarrhea indicate protein loss in the GI tract. In addition, GI bleeding has also been shown to increase AAT clearance because of whole blood loss.
Imaging Studies
Double-contrast radiographs of the small bowel can be valuable in diagnosing the condition, as they may reveal thickened folds caused by intestinal edema resulting from hypoproteinemia, nodular protrusions, and an absence of mucosal ulcerations.
Ultrasonography and computed tomography (CT) scanning are also useful in identifying dilated intestinal loops, regular and diffuse thickening of the intestinal walls, plical hypertrophy, and mesenteric edema. [13] In CT scans, circumferential thickening of the small bowel wall with low attenuation (typically < 30 Hounsfield units) may be observed.
Multidetector CT (MDCT) scanning following direct lymphangiography has proven to be an effective method for evaluating and diagnosing primary intestinal lymphangiectasia. In a retrospective study involving 55 affected patients, all of whom underwent MDCT after direct lymphangiography, investigators noted that MDCT successfully identified various abnormalities, including intra-intestinal, extra-intestinal, and lymphatic vessel issues. These abnormalities included different degrees of intestinal dilatation, small bowel wall thickening, ascites, mesenteric edema, mesenteric nodules, lumbar trunk and intestinal trunk reflux. [14]
Procedures
Endoscopy
Endoscopy has consistently proven its utility in diagnosing intestinal lymphangiectasis. Small bowel enteroscopy allows for the identification of mucosal changes and the collection of histologic samples. [15, 16, 17] During endoscopy, characteristic findings include white villi and/or spots (dilated lacteals), white nodules, submucosal elevations, and xanthomatous plaques.
Capsule endoscopy
Capsule endoscopy has been used to help identify the characteristic changes of intestinal lymphangiectasia, particularly in areas not reachable with standard endoscopy since this condition often occurs at jejunoileum. [18]
Jejunal biopsy
A jejunal biopsy provides a definitive diagnosis, revealing the dilation of mucosal and submucosal lymphatic channels. To enhance diagnostic accuracy, it is advisable to use large biopsy forceps when possible. Given the patchy nature of small bowel involvement, obtaining multiple biopsy samples from different areas is recommended.
Histologic Findings
Intestinal biopsy results display the characteristic dilatation of the lymph vessels of the mucosa, submucosa, and subserosa layers, often without any signs of inflammation. Surface epithelial cells are typically normal. [7] See the image below.
Intestinal villi of normal height with dilated lymphatics as usually seen on histology of villi in intestinal lymphagiectasia.
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Intestinal villi of normal height with dilated lymphatics as usually seen on histology of villi in intestinal lymphagiectasia.
