LAUSR

Splenomegaly is known to occur with the progression of liver cirrhosis (LC) and idiopathic portal hypertension. The incidence rate is reported as 50%–70% in LC patients. Although the precise pathogenic mechanisms causing spleen enlargement in patients with portal hypertension are still poorly elucidated, it was clear that there were some architectural alterations, including pulp hyperplasia, congestion from increased blood flow, and fibrosis in the spleen. There was a rat‐ model report showing a significant correlation between spleen weight and portal hypertension, and I previously reported that there was a positive correlation between spleen diameter and spleen stiffness in carbon tetrachloride (CCL4) rat model. 6 The diameter of spleen became larger according to the administration of CCL4. This phenomenon seems to reflect the portal hypertension state. As general spleen pathological findings, reticular fiber is existing around splenic cords, in which splenic arterial blood flows. In LC patients, however, this reticular fiber and collagen fiber around splenic cords in red pulp will be diffuse thickening. Finally, this fibrogenesis change leads to splenic blood flow obstruction and congestion with narrowing of splenic‐cord width and narrowing of splenic‐sinus lumens. For the secure calculation method of spleen size, volumetry using computed tomography (CT) has been considered as the standard method. But this method requires a lot of labors and time. While, spleen index (SI) measurement by ultrasonography is not invasive and very speedy. The problem is that SI measurement method has not been unified yet and depends on the skill of inspector. There are 2 calculation formulas in the two‐dimensional (2D) SI measurement. The one is defined as maximum length in the longitudinal view � maximum width in the longitudinal view. The other is the length until splenic hilum in the longitudinal view � maximum width in the longitudinal view. Recently, volumetry of spleen using ultrasonography has also been reported, which is called three‐dimensional (3D) SI. However, there are also many measurement methods in 3D SI calculation, and it has not been clear yet, which one is best. Nemati et al. has defined the formula of 3D SI as follows: 0.524 � maximum length in the transverse view � maximum width in the transverse view � 1/2 (maximum length + craniocaudal length) in the longitudinal view. And the formula by Chow et al. was described as follows: 0.52 � maximum length in the longitudinal view � maximum width in the longitudinal view � maximum length in the transverse view. I read with great interest the original article written by Hirooka et al. They clarified which SI measurement by ultrasonography (including 2D, 3D method, spleen length, and width) was most correlated with spleen volume by CT. Their formula of 3D SI was simplified as follows; maximum length in the longitudinal view�maximumwidth in the longitudinal view � maximum length in the transverse view. As the result, each correlation coefficient was 0.91, 0.91, 0.78, 0.87, 0.84, and 0.41 (Hirooka's 3D, Chow's 3D, Nemati's 3D, 2D SI, spleen length, and spleen width, respectively). In this report, 3D SI formula by Hirooka seems to have highest reliability, but even 2D SI and spleen length could be useful to predict the spleen volume with high correlation. I had been very skeptical about whether spleen length measurements or 2D SI accurately reflect actual spleen volume, but this report has resolved my doubts. They also clarified the difference of diagnostic accuracy for predicting high‐risk esophageal varices (EVs) between fourmethods (CT volumetry, 3D SI, 2D SI, and spleen length). Each area under the curve (AUC) was 0.814, 0.804, 0.796, and 0.768. From this result, it was turned out that 2D SI and spleen length are enough to predict EVs. Interestingly, they additionally validated the diagnostic accuracy for EVS using platelet count (PLT). Each AUC of