How To Measure The Spleen On Ultrasound | Splenic Length, Width, Thickness & Volume Measurements & Size USG Longitudinal (Length) measurement: With the probe in the longitudinal plane, measure the spleen from its most superior (cranial) to its most inferior (caudal) edge. Width (medio-lateral) measurement: Still in the transverse orientation, measure the spleen from its medial to lateral edge. Transverse (Thickness) measurement: Rotate the probe to a transverse orientation. Measure the spleen fr