PROTEIN LOSING ENTEROPATHY IMAGING WITH Tc-99m DEXTRAN

Article Nº AJ01-4

Abstract

Protein losing enteropathy can be demonstrated by different methods. We applied a newly developed technique in one patient using endovenous ^99mTc –Dextran and serial scintigraphic images to confirm the suspected loss of this macromolecule that simulates albumin. This simple, inexpensive technique avoids the need of fecal recollection and also the risks of using human derivative products like human seroalbumin of the former techniques.

Key words : protein-losing enteropathy, Dextran, human seroalbumin, scintigraphy

Resumen

Existen diferentes métodos para confirmar una enteropatía perdedora de proteínas. Aplicamos la técnica recientemente descrita usando ^99mTc –Dextran endovenoso e imágenes cintigráficas seriadas en un paciente. La sustancia utilizada es una macromolécula que simula el comportamiento de la albúmina. Esta técnica, simple y de bajo costo, evita la necesidad de recolectar deposiciones y también los riesgos relacionados con el uso de productos de origen humano como la seroalbúmina humana que están presentes en las técnicas tradicionales.

Palabras claves : enteropatía perdedora de proteínas, Dextran, seroalbúmina humana, cintigrafía.

Introduction

Protein losing enteropathy is associated with many intestinal and extraintestinal diseases including inflammatory bowel disease, gluten sensitive enteropathy, ileocecal tuberculosis, intestinal lymphangiectasia (primary and secondary), hypertrophic gastropathy, gastric infection with Campylobacter pylori and allergic enteropathy (1,2,3,4). Methods like quantification of fecal alpha-1-antirypsin or ⁵¹Cr-chromium labeled albumin and imaging with ^99mTc-labeled human serum albumin, are being used to establish the diagnosis of protein losing enteropathy. There are some disadvantages with these methods that limit their application i.e. fecal recollection, use of human derivative products like seroalbumin. A new scintigraphic method using ^99mTc –labeled –Dextran was first described in 1995 by Bhatnagar et al. (1). This method demonstrated significative intestinal radiotracer accumulation at 3 – 4 hours postinjection in 22 patients, giving also information about localization and extension of the disease; in 4 of 12 healthy subjects there was minimal abdominal accumulation occurring late in the study period (5). This polysaccharides of molecular weight between 60.000 and 90.000 is being used as a plasma expander and, in radioactive tagged form, for lymphoscintigraphy and blood pool studies. Considering its availability, low cost and ability to demonstrate the site of protein loss we used this method in a patient with suspected protein-losing enteropathy.

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Case Report

A 14-year-old male was studied because of hipoproteinemia, especially hipoalbuminemia. His protein intake was good. Liver function tests and duodenal biopsy were normal. No proteinuria was found. A cardiopathy was surgically corrected 8 years before. Anterior abdominal images were obtained every 15 minutes for 1 hour after intravenous administration of 555MBq (15 mCi) of ^99mTc –Dextran (molecular weight of 70.000). Thereafter images were taken every 30 minutes for a total of 4 hours. Besides normal blood pool distribution, beginning at 2 hours, lower abdominal activity was seen with progression through small intestinal loops. No gastric or thyroid activity was seen. Protein losing enteropathy was confirmed but no ethiological diagnosis could be established. The patient recovered after dietary restrictions.

Comments

The noninvasive confirmation of clinically suspected gastrointestinal protein loss with topographic localization is highly desirable. The technique with ^99mTc –Dextran is easy to perform. About 50% of this polysaccharide, in its molecular weight form of 70000, is excreted unchanged in the urine within 24 hours. Part of it is slowly metabolized to glucose but also a small amount is excreted into the gastrointestinal tract and eliminated in the feces (6). This intestinal elimination could be a limitation for this method. The patient studied by Bhatnagar et al. (1) showed clear leak into the intestine in the subsplenic area and duodenal biopsy showed intestinal lymphangiectasia. In our patient the leak was seen in the lower abdomen, suggesting ileal loss, and this patient had a normal duodenal biopsy.

Bibliography

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