Monday, March 8, 2010  More ovaries...  In a recent post I
discussed a paper that claimed to show that dogs lived longer if
they kept their ovaries, despite a lot of evidence to the
contrary. This article got an inordinate amount of attention in
the secondary literature and the blogosphere, most of it quite
uncritical. With this kind of observational study, it is easy to
analyze the data in a way that will give a positive result, or
even to design the study in such a way that a positive result is
nearly guaranteed, as discussed here, and here.  In the most
recent issue of JAVMA, there is a paper that provides an
interesting counterpoint to the earlier paper. This paper
discussed dogs (and two cats) that had residual ovarian tissue
left after spay surgeries. Most of these animals had ovarian
tissue left in the normal anatomical position for ovaries to be,
indicating that failure to identify and remove the entire ovary
at the time of surgery is much more common than ectopic ovarian
tissue is (I have seen one ca