Schistosomiasis mansoni in low transmission areas: abdominal ultrasound

Mem Inst Oswaldo Cruz, Rio de Janeiro, Vol. 97(Suppl. I): 153-159, 2002 153 Schistosomiasis Mansoni in Low Transmission Areas. Abdominal Ultrasound R Ruiz, P Candia*, M Garassini*, C Tombazzi*, G Certad, AC Bruces, O Noya, B Alarcón de Noya/+ Sección de Biohelmintiasis, Instituto de Medicina Tropical and Cátedra de Parasitologia *Cátedra de Gastroenterologia, Escuela de Medicina “Luis Razetti”, Facultad de Medicina, Universidad Central de Venezuela, Apartado Postal 47706, Los Chaguaramos, Caracas 1041-A, Venezuela In endemic areas with low prevalence and low intensity of infection, the diagnosis of hepatic pathology due to the Schistosoma mansoni infection is very difficult. In order to establish the hepatic morbidity, a double-blind study was achieved in Venezuelan endemic areas, with one group of patients with schistosomiasis and the other one of non-infected people, that were evaluated clinically and by abdominal ultrasound using the Cairo classification. Schistosomiasis diagnosis was established based on parasitologic and serological tests. The increase of the hepatic size at midclavicular and midsternal lines (in hepatometry) and the hard liver consistency were the clinical parameters able to differentiate infected persons from non infected ones, as well as the presence of left lobe hepatomegaly detected by abdominal ultrasound. The periportal thickening, especially the mild form, was frequent in all age groups in both infected and uninfected patients. There was not correlation between the intensity of infection and ultrasound under the current circumstances. Our data suggest that in Venezuela, a low endemic area of transmission of schistosomiasis, the hepatic morbidity is mild and uncommon. The Cairo classification seems to overestimate the prevalence of periportal pathology. The specificity of the method must be improved, especially for the recognition of precocious pathology. Other causes of hepatopathies must be investigated. Key word: ultrasound - schistosomiasis - low transmission - Venezuela The diagnosis of schistosomiasis in Venezuela is very difficult due to the low prevalence, low intensity of the infection and to the unspecificity of clinical signs usually associated with this disease (Ruiz et al. 1999). For this reason, the Venezuelan Schistosomiasis Research Group has recommended the employment of immunological techniques for the diagnosis of schistosomiasis (Alarcón de Noya et al. 1992). Moreover, the prevalence of hepatic morbidity in schistosomiasis is difficult to determine because some of the methods that could be used for diagnosis such as the biopsy, or those that evaluate the hemodynamic alterations of the liver, are dangerous and invasive procedures that can not be performed on patients under field conditions. Periportal fibrosis is one of the most characteristic alteration in the liver of infected patients with schistosomiasis (Prata 1987) and it is considered, the most frequent cause of hepatic fibrosis worldwide (Warren 1984). Abdominal ultrasound has shown to be an alternative method for diagnosis, when the liver biopsy is contraindicated or This work was financed by the “Programa de Control de Enfermedades Endémicas” of Malariología-World Bank (PCEE/ PNDU) and partially by the “Consejo de Desarrollo Científico y Humanístico” de la Universidad Central de Venezuela for facilitating travel expenses for congress communications. + Corresponding author. Fax:+ 58-212-6053563. E-mail: Received 18 June 2002 Accepted 15 August 2002 impracticable (El-Rooby 1985). This method is relatively inexpensive, rapid, portable, causes no biological hazards to the patients and its sensitivity and specificity in the recognition of periportal fibrosis, is comparable with the one reported for hepatic biopsy (Abdel-Wahab et al. 1989, Cerri et al. 1984, Homeida et al. 1988), percutaneous transhepatic portography, angiography (Hatz et al. 1992a), and clinical examination (Kardorff et al. 1997). It reflects the dynamic changes produced by portal hypertension, since it measures the portal vein diameter and the presence of systemic collateral blood vessels that are correlated with esophageal varices (Abdel-Latif et al. 1981, Davidson et al. 1991, Abdel-Wahab et al. 1993, Richter et al. 1998). However, this tool requires well-trained physicians, and its standardization is still a matter of debate after two WHO workshops (Cairo Working Group 1992, Niamey Working Group 2000). Some studies have reported that ultrasound could improve the accuracy of clinical examination in endemic areas of schistosomiasis (Lambertucci et al. 2000). Moreover, it has been shown that ultrasound could be an excellent indicator for diagnosis, and very useful for planning and monitoring control programs in areas of different endemicity (Hatz et al. 1990, 1992b, Lambertucci et al. 2000). Almost all investigations on abdominal ultrasound have been done in hospitalized patients or in endemic areas with high schistosomiasis prevalence and intensity of infection. The aim of this work was to evaluate the use of abdominal ultrasound using the Cairo classification for the schistosomiasis hepatic fibrosis diagnosis in Venezuela, a low transmission endemic area with low prevalence and morbidity. 154 Ultrasound in Schistosomiasis • R Ruiz et al. MATERIALS AND METHODS Study area and population - This transverse and double blind study was carried out between 1998 and 2001 in three villages situated in the Venezuelan endemic area for schistosomiasis: Caraballeda, La Curía and Belén. Participants were considered cases of schistosomiasis according to a recent proposal of our group (Ruiz et al. 1999) and described below. Simultaneously, we selected a group of non infected persons from endemic areas to match them according to sex and age with the infected ones. These persons did not have antecedents of schistosomiasis and all the laboratorial tests for this disease were negatives. Stool evaluation and serologic tests - Stool samples were collected and examined for the presence of S. mansoni eggs by the Kato Katz technique (Katz et al. 1972). For the serological diagnosis of schistosomiasis different immunological tests were performed: Enzyme Linked Immuno Absorbent Assay with Sodium Metaperiodate (SMPELISA) (Alarcón de Noya et al. 2000), Circumoval Precipitin Test (COPT) (Spencer et al. 1991) and Alkaline Phosphatase Immunoassay (APIA) (Pujol & Cesari 1990). Clinical evaluation - This evaluation included a medical history, epidemiological data, current symptoms and a physical examination. Informed consent was obtained from each patient or representing in the case of children, and only volunteers were admitted in this study. Experienced observers carried out an abdominal ultrasound employing a portable Toshiba equipment with curved 3.75 MHz transducer. The echographers make first diagnostic impression and cataloged as normal, periportal fibrosis, hepatomegaly and hepatic steatosis according the obser (...truncated)