Riedel's Lobe of the Liver.

A previously healthy 54-year-old woman presented to the gastroenterology department with liver test abnormalities at a medical check-up. Laboratory evaluation showed that serum aspartate aminotransferase and alanine aminotransferase levels were elevated to 199 IU/L (range, 13-33) and 242 IU/L (range, 6-27), respectively. Vital signs were normal, and she had no symptoms. Her abdomen was soft and non-tender. Although no hepatic lesions were detected by ultrasonography, computed tomography revealed a caudal prolongation of the right hepatic lobe (Fig. 1). Thus, a diagnosis of Riedel’s lobe was incidentally made. A positive antinuclear antibody and interface hepatitis on biopsy confirmed that abnormal liver function tests were due to autoimmune hepatitis. Prednisolone therapy normalized her liver functions.

FIG. 1

Downward elongation of the liver (arrows), ending at the level of the iliac crest.

Riedel’s lobe is an anatomical variation, and the exact etiology is still unclear.12 The reported incidence varies considerably (3.3-31%); this may be because the diagnostic criteria and methods are different from the previous reports.123 The original definition of Riedel’s lobe is a downward tongue-like projection of the right hepatic lobe to the level of, or below the umbilicus.3 Most patients are asymptomatic; however, some patients present with a right-sided abdominal palpable mass.2 In addition, extrinsic compression or torsion can occur.2 Asymptomatic or uncomplicated Riedel’s lobe requires no specific treatments and has a good prognosis.2

The differential diagnoses include hepatomegaly and accessory liver lobes. Although most accessory lobes are located below the liver, the prevalence has been reported to be less than 1%.4 Therefore, Riedel’s lobe is clinically important to avoid a false impression of hepatomegaly. In the present case, hepatomegaly was excluded since the transverse diameter and the greatest anteroposterior diameter on the level with the upper pole of the right kidney were approximately 17 cm and 10 cm, respectively (normal range, 20-23 and 10-12.5, respectively) (Fig. 2).5

FIG. 2

The transverse diameter and the greatest anteroposterior diameter on the level with the upper pole of the right kidney.