O valor da fase sem contraste na tomografia computadorizada do abdome

Abstract

OBJECTIVE: To determine the role of the unenhanced phase of abdominal computed tomography in patients without a definite diagnosis or undergoing tumor staging. MATERIALS AND METHODS: A prospective and transversal study was developed with 100 consecutive patients submitted to unenhanced and contrastenhanced abdominal computed tomography. Two observers evaluated all the computed tomography images in the contrast-enhanced phase (first analysis) and, later, in the unenhanced phase (second analysis) in an attempt to establish the primary and secondary diagnoses as a function of the clinical indication for the study. The frequency of changes in the diagnoses resulting from a combined analysis of the images in the pre-and post-contrast phases was evaluated. Cases with changes in the diagnosis were reviewed by clinical specialists for determining possible changes in the therapeutic approach. RESULTS: Primary and secondary diagnoses were changed in respectively 1 and 18 cases (p = 1.000; p = 0.143) as follows: steatosis, adrenal nodules, nephrolithiasis, renal cysts and hepatic calcification. In the cases where the unenhanced phase changed the diagnosis, the specialists changed the therapeutic approach in 14 of the 19 patients (73%) (p = 0.038). CONCLUSION: No significant change was observed in the primary or secondary diagnosis as a result of the findings in the unenhanced phase. However, changes in secondary diagnoses affected the therapeutic approach adopted by the specialists. Keywords: Computed tomography; Contrast media; Abdomen.OBJETIVO: Determinar o valor agregado da fase sem meio de contraste da tomografia computadorizada do abdome em pacientes sem diagnóstico determinado ou em estadiamento tumoral. MATERIAIS E MÉTODOS: Estudo prospectivo e transversal em 100 pacientes consecutivos submetidos a tomografia computadorizada abdominal sem e com meio de contraste intravenoso. Dois examinadores avaliaram todos os exames, procurando estabelecer, através da fase com meio de contraste intravenoso (primeira análise) e posteriormente através da fase sem contraste (segunda análise), o diagnóstico principal e os secundários em função da indicação clínica do exame. Mediu-se a freqüência de mudança diagnóstica decorrente da análise combinada das fases pré-e pós-contraste intravenoso. Casos que tiveram mudança diagnóstica foram avaliados por especialistas clínicos para determinar se implicaria mudanças de conduta. RESULTADOS: Diagnósticos principal e secundário foram modificados em 1 e 18 casos, respectivamente (p = 1,000; p = 0,143). Os diagnósticos modificados foram: esteatose, definição de nódulo em adrenal, nefrolitíase, classificação de cistos renais e calcificação hepática. Nos casos em que a fase sem contraste modificou o diagnóstico, os especialistas mudaram sua conduta em 14/19 (73%) dos pacientes (p = 0,038). CONCLUSÃO: A fase sem contraste não modificou significativamente o diagnóstico principal ou secundário. Porém, as mudanças nos diagnós-ticos secundários influenciaram na conduta adotada pelos especialistas. Unite...

When the non-contrast-enhanced phase is unnecessary in abdominal computed tomography scans? A retrospective analysis of 244 cases

“…Iannaccone et al (8) , in 2005, reported that the combined use of the arterial, portal and equilibrium phases present sensitivity and positive predictive value of 92.8% and 97.3%, respectively, for detection of HCC in cirrhotic patients, concluding that the non-contrast-enhanced phase does not add value to justify its utilization for the investigation of such tumors. In 2008, Leite et al (9) evaluated 100 patients with undefined clinical indication or in tumor staging/re-staging, demonstrating that the non-contrast-enhanced phase is not indispensable for such evaluations.…”

“…Among such strategies, the suppression of some of the studies' phases seems to be a practical and safe way to achieve dose reduction, since the reliability and diagnostic accuracy of the exams are maintained (9) .…”

“…Most of such protocols utilize the non-contrast-enhanced phase which precedes the contrast-enhanced phases. In spite of being widely and universally adopted for determined clinical indications, the use of such protocols have implications related to radiation dose, images acquisition time and x-ray tube wear, and would only be justifiable in case it added supplementary data indispensable for the establishment of an accurate diagnosis, thus positively interfering in the approach to patients and prognosis (9) .…”

Quando a fase de equilíbrio pode ser suprimida nos exames de tomografia computadorizada de abdome?

“…When such strategies are applied together, a significant reduction is observed in the radiation dose to which the patient is exposed (6) , in some specific clinical situations attaining equivalent doses lower than 2 mSv (23) , which correspond to three views of plain abdominal radiography or one cranial CT (25) . Besides the above mentioned strategies, suppression of one or more imaging phases has been showing to be a feasible and effective alternative (7,11) . In the present study, considering the evaluation of a wide range of clinical indications, frequently with four acquisition phases, the authors obtained an estimated mean effective dose of 41.2 mSv per scan, with an average of 12.5 mSv per phase.…”

Determinação da dose em pacientes submetidos a exames de tomografia computadorizada de abdome em um serviço de radiologia e diagnóstico por imagem

“…Imbriaco et al analisaram exames com suspeita de câncer de pâncreas e demonstraram que a realização de apenas uma fase pós-contraste era o suficiente para um diagnóstico e estadiamento desta neoplasia (IMBRIACO et al, 2005). Leite et al concluíram que a fase sem contraste não era fundamental para o diagnóstico em várias indicações clínicas (LEITE et al, 2008). Metser et al comprovaram que para detecção de tumores do trato urinário alto e baixo, a fase portal é mais eficiente que a fase de equilíbrio, sendo esta última desnecessária para o seu diagnóstico (METSER et al, 2012).…”