In this post, he describes the difference between SU and BU in a straight-forward manner:
This is an issue I have been dealing with since the start of my practice. It’s the identical story over and over again. I came across the same thing 2 times this month. The issue is far from trivial because the proper diagnosis will change the method of treatment. Delayed diagnosis (sometimes for years) will delay and sometimes prevent pregnancy.
OK, what’s a bicornuate uterus? A bicornuate uters is an abnormality in the way the uterus is shaped. It does not develop; some women are born with them. Uterine and/or vaginal abnormalities that are present from birth are lumped into a category of Mullerian Abnormalities. There are many different varieties, and all are rare.
In a girl embryo, the uterus starts as 2 tubes that merge together to form a larger hollow structure. If the 2 tubes do not completely come together, a bicornuate uterus develops. It is a uterus with 2 horns , one going out to the left and one going out to the right.
This is a very general description. There are tons of variations. Some bicornuate uteri have larger horns and are not connected in the middle, and others are mostly connected in the middle with just a small amount sticking out as horns.
Here's the rub. I have seen many patients who were told they have bicornuate uteri but their real diagnosis was a septum. This mistake has happened even if the patient had a HSG, 3-d ultrasound, 3-d sonohysterogram, MRI or even hysteroscopy.
So what? It’s a big what. The uterus with the septum is smooth over the top. The bicornuate dips at the top, sometimes considerably.
So one nurse telling me it's "bi-corny-it" doesn't do it for me. I expect my RE to know the difference and properly diagnose me.
Dr. Licciardi describes the implications of different diagnoses in this post:
The reason it is vital to know your diagnosis has to do with treatment. If you have a septum, most (not all) doctors would recommend treatment. This is because an experienced reproductive surgeon can fix a septum relatively easily. It’s done through the vagina using a hysteroscope. The doctor looks in, then slides a tiny scissors through the scope and makes small cuts at the septum until it is gone, making the uterus normally shaped. Some doctors will recommend a laparoscopy at the same time to guide themselves through the surgery. Others will perform the surgery using the hysteroscope and an intra-operative ultrasound to guide them, avoiding the laparoscopy portion. In either case, patients go home the same day.
A bicornuate uterus is a whole different story. To fix this a doctor needs to perform a laparotomy (an incision into your abdomen), then slice the uterus wide open, then sew it up in such a way that the 2 sides come together to make one round uterus. As you can imagine, this has a much higher complication rate, and has a higher rate of infertility due to post-op scar tissue. Hospitalization can be 2-3 days. Full recovery is 6 weeks. Because this procedure is more difficult and has a higher complication rate, it is rarely performed.
This gets us back to the very beginning. If you have a septum, but your doctor calls it a bicornuate, you probably will not be offered treatment and be faced with continued increased odds of infertility and miscarriage. If the correct diagnosis of a septum is made originally, you could have a more simple procedure that may increase your odds of reaching your goal.
Many patients have come to me with a diagnosis of a bicornuate uterus. Told surgery was not a good option, they ask me what else can be done to help them get pregnant or reduce their odds of miscarriage. Some actually have a bicornuate uterus. Some are very surprised when I tell them they really have a septum and should revisit the surgical option.
If it turns out it is BU, so be it. But I won't believe it till I hear it from a specialist. Oh, and have I mentioned that SU is twice as common as BU? According to this study (PDF document; scroll to the second page for a chart), SU occurred in 1.4% of the population, and BU in only 0.7%. Now, we all know how I feel about the odds, but now that I'm much, MUCH more hopeful and optimistic (I WILL have babies), I feel comfortable with hoping for the most common of the MAs.