Type:
Educational Exhibit
Keywords:
Abdomen, Anatomy, Liver, CT, MR, Diagnostic procedure, Congenital
Authors:
E. ARAUJO1, U. S. Torres2, H. R. F. Dalla Pria2, L. R. Torres3, M. H. NAVES INACIO PEDROSO4, D. J. J. RACY4, G. D'Ippolito4; 1Sao paulo, Sao paulo/BR, 2Sao Paulo, SP/BR, 3São Paulo/SP, SP/BR, 4São Paulo/BR
DOI:
10.26044/ecr2019/C-1203
Background
Accessory liver lobes (ALL) are an uncommon condition and consist in the presence of a supernumerary lobe of normal hepatic parenchyma in continuity with the liver.
ALL results from a congenital ectopic hepatic tissue mostly due to embryonic heteroplasia,
although in rare instances an ALL may occur after trauma or surgery 1,2.
Some authors believe that ALL is associated with an autosomal recessive gene with a very low frequency.
Currently,
there are two hypotheses (A and B) on the mechanism of an ALL: (A) the embryonic liver curls outwards and forms an accessory lobe during the embryonic stage of development or (B) an accessory lobe arises owing to intra-abdominal hypertension caused by the development of the tunica muscularis recti and the enlargement of the liver 1,3.
In 1925 Cullen first proposed the term “accessory lobe” of the liver.
ALL are usually asymptomatic and found incidentally on imaging exams,
surgery or autopsy.
Most accessory lobes are located below the liver (infrahepatic) 4 Fig. 1.
In terms of frequency,
Watanabe et al. reported the occurrence of ALL in 0.9 % of 1,060 laparoscopy cases; Kappor et al. found them in 0.7 % of 1000 abdominal CT scans. The prevalence,
in general,
is considered as being lower than 1%,
but it is probably underestimated owing to the asymptomatic nature of this condition 5,6.