Evaluation of ultrasonographic staging systems for the assessment of Schistosoma mansoni induced hepatic involvement

For the sonographic assessment and grading of hepatosplenic morbidity induced by Schistosoma mansoni infection, several quantitative and qualitative classification systems have been used. In an attempt to evaluate two staging systems, a study was performed as part of a schistosomiasis research and control programme in Richard Toll, Senegal. A total of 700 residents of the township N'diangué were parasitologically, clinically and sonographically examined in July 1993. Two ultrasound observers (M.D. and E.D.) applied the Cairo and the Managil classification (E.D. only) for the grading of periportal thickening of the liver. In spite of high prevalence and intensity of infection, severe hepatic morbidity was rare. According to the Cairo classification, there was a high percentage of subjects with grade I periportal thickening, with considerable inter-observer variability. In the Cairo classification, which is based on the diameter of peripheral portal vein branches, firm cut-offs are used, independent of body height. We show the relationship between body height and portal vein diameters and recommend the use of body height-dependent reference values to avoid falsely high percentages of periportal thickening, especially in children. To minimize inter-observer variability, a clarification of existing instructions for taking measurements for grading is suggested. These suggestions have been considered during the follow-up expert meeting on the Cairo classification in Niamey under the auspices of the World Health Organization in October 1996.