A novel, simple method of functional spleen volume calculation by liver-spleen scan

Spleen enlargement is commonly associated with portal hypertension from cir rhosis and may cause thrombocytopenia. Thus, accurate assessment of spleen size may be helpful in the clinical evaluation. Spleen length is not a prec ise estimate of spleen size because of the variation in spleen configuratio n, and spleen volumes measured by edging techniques can be tedious. We pres ent a new method of measuring the functional spleen volume by liver-spleen scan (LSSs), validation experiments and some clinical data. Methods: The me thod involves measurement of the total spleen counts by SPECT and dividing by a representative voxel concentration on a single frame to obtain the org an volume. Validation included phantom studies and clinical evaluation in 4 43 consecutive patients, including 216 with histologic assessments of chron ic liver disease (CLD) and 11 healthy volunteers. Results: A calibration fa ctor determined from phantoms was used to convert the calculated volume (CV ) to the "true" volume (V): V = CV (0.956) - 66.5 (r = 0.9991; P < 0.001). The volume calculations were validated in a second group of phantoms (r = 0 .981; P < 0.0001). Spleen volumes were expressed as volume (cm(3)) and as V olume per pound ideal body weight (IBW) (cm(3)/lb) (the conversion factor t o convert cm3/lb IBW to cm(3)/kg IBW is 2.2). Clinical studies of reproduci bility included demonstration of a significant (P < 0.0001) linear correlat ion between Volumes calculated from repeat LSSs within 9 mo of the initial LSS in 11 healthy volunteers and 32 patients with CLD: y = 1.02x - 25; r = 0.968. The correlation with spleen volumes from autopsy or splenectomy was significant: y = 0.766x + 57; r = 0.845; P < 0.001. The normal spleen Volum e in 11 patients was 201 +/- 77 cm(3) and 1.43 +/- 0.68 cm(3)/lb IBW (upper limits of normal: 335 cm(3) or 2.5 cm(3)/lb IBW). In 443 consecutive LSSs over 15 mo, half of the patients had spleen volumes above the upper limits of healthy volunteers, and CLD was present in 90.9% of these patients. In 2 16 patients with histologically proven liver disease, a progressive increas e in the percentage of spleen volumes above the upper limits of normal was noted from no fibrosis (10%) to mild to moderate fibrosis (36.7%) to early cirrhosis (52%) to advanced liver disease (75%). The correlation of spleen Volume with platelet count was excellent (r = 0.7635; P < 0.005). Conclusio n: This novel spleen Volume measurement detects serious liver disease and c orrelates with splenic hyperfunction.