Hello
Pain on the left side of the rib from last 6 months , weight loss 20 pounds within a month ( sudden loss ) .
Different tests indicates the enlargement of spleen .
Enlargement of spleen may be-
1 Enlargement due to increased demand for splenic function as
tuberculosis, malaria , splenic abscess, S L E ,
sarcoidosis, marrow infiltration by tumors, leukemias ( tumors & leukemias may be responsible for weight loss as pain is from last 6 months , so history is also suggestive).
Other reasons of enlargement are ,
amyloidosis , hyperlipidemias, lymphoma and carcinoma .
At present you must be investigated for tumor ( any where in abdominal organs with
blood cancer ) blood disorder and tuberculosis ( due to pain in the left side rib.
In my opinion
consult a pulmonologist and get his opinion as sometimes thickened pleaura may be responsible for such unexplained pain .
However weight loss sudden and 6 month history is an indication of tumor or leukemias.
Good luck.