To me, at least the first reported stab to Eddowes' liver was quite likely collateral damage inflicted with the initial plunge of the knife into the abdomen, as Brown says: "Behind this [the ensiform cartilage], the liver was stabbed as if by the point of a sharp instrument".
He goes on to say "Below this was another incision into the liver of about two and a half inches, and below this the left lobe of the liver was slit through by a vertical cut." These could have been caused by the initial abdominal incision, and/or sustained as a result of the killer's going after the left kidney - it's perhaps significant in this context that Brown reports a slit in the left lobe of the liver, which would be some distance away from the otherwise midline cut down her upper abdomen. Brown also indicates that the spleen, another organ adjacent to the left kidney, had been damaged
In his statement (from the Ultimate JTR.Companion) Brown gives additional info on the cuts to the liver;
"There was a cut from the upper part of the slit on the under surface of the liver to the left side and another cut at right angles to this which were about an inch and a half deep and 2 1/2 inches long."
I must admit I find that description hard to picture, can anyone else? But could well be collateral damage from the kidney extraction. Except that Brown describes that as "carefully taken out"
and that the pancreas had been cut on the left hand side.
Again, according to his statement, Brown says "the pancreas was cut but not through on the left side of the spinal column", rather than the left side in general. So quite near the mid-line, most likely.