Does coronal oblique length of spleen on CT reflect splenic index?

Splenic dimension of >12 cm on coronal plane on ultrasound is considered to represent splenomegaly. We sought to estimate the accuracy of similar coronal oblique length of spleen on CT in identifying splenomegaly by comparing it with CT splenic index. We also sought to establish the splenic width, craniocaudal dimension (CC), thickness, and coronal oblique length in both normal and splenomegaly groups.

319 consecutive patients undergoing CT abdomen were included in the study and measurements of width (W), CC, thickness (T), and coronal oblique length (L) made. Splenic index was calculated based on the formula CC × W × T. Diagnostic accuracy of coronal oblique length in identifying splenomegaly on the basis of splenic index was assessed. Patients with splenic trauma were excluded. Patients with perisplenic collection that precluded proper measurement of spleen were excluded.

Of the 319 patients, 41 patients had splenomegaly with splenic index >480. 278 patients showed normal splenic index less than or equal to 480. Sensitivity and specificity of coronal oblique length as ≥12 cm in identifying splenomegaly were 97.8% and 34.1%, respectively. Positive and negative predictive values for the same were 91% and 70%, respectively (p value-0.000). There is overlap of numerical values for thickness and coronal oblique length in the normal and splenomegaly groups for a 95% confidence interval, whereas there is no significant overlap between these groups with respect to the craniocaudal length and width. Hence, craniocaudal length of 9.5 cm and width of 10.6 cm may be used as upper cutoff limit for normal spleen.

Coronal oblique dimension of spleen >12 cm is highly sensitive and shows good positive predictive value in diagnosing splenomegaly but has poor specificity and negative predictive value. Ideally, splenic index calculated using the CC, width, and thickness is the most reliable measurement for diagnosing splenomegaly. But if single measurements are to be used for identifying splenomegaly, craniocaudal length >9.5 cm, width of >10.6 cm, and coronal oblique dimension >12 cm may be used.