Aim: To identify and describe changes in spleen volume occurring in patients with colorectal metastases to the liver after partial hepatectomy. Materials and methods: Forty-one consecutive patients (20 men, 21 women) with histopathology-proven colorectal liver metastases who underwent partial hepatectomy between August 2007 and April 2011 were included. Liver and spleen volumes were measured by computed tomography (CT) volumetry on the most recent CT prior to surgery and on all CTs obtained within a year after partial hepatectomy. Patients were carefully evaluated for and excluded if they had co-morbid conditions known to cause splenomegaly or risk factors for portal hypertension such as underlying liver disease and portal vein thrombosis. Results: Thirty-two (78%) patients demonstrated an increase in spleen volume on the first post-operative CT, with more than a double increase in volume amongst five patients. Spleen volume increased by an average of 43% within 3 months of partial hepatectomy (p < 0.0001) and remained increased through 6 months after surgery, returning to near baseline thereafter. In the remaining nine (22%) patients, the spleen was observed to decrease an average of 11% in volume on first postoperative CT (p < 0.005). Conclusions: Splenic enlargement after partial hepatectomy of colorectal metastases is a common finding on CT. Increased familiarity amongst radiologists of this phenomenon as likely reflecting physiological changes is important in order to avoid unnecessary evaluation for underlying conditions causing interval enlargement of the spleen.