Home > Education, Gynecology > 5 Things I Learned From Netter

5 Things I Learned From Netter

I recently had the opportunity to go to the anatomy lab and help the first years go through the pelvic anatomy.  What a blast!  There is nothing like dissecting a cadaver to tune up one’s surgical anatomy skills, and helping young eager medical students through it is a great experience.

Prior to going into the lab, I spent many hours going through Netter’s atlas to brush up on the anatomy so I could accurately help the medical students.  Its amazing what one can learn reviewing what one used to know.  Here’s a few examples:

1. The small vessels we like to cut at cesarean have names, and we can avoid them.

Everybody that does cesarean deliveries knows that there are small vessels in the path of entry that sometimes get cut, but not everyone knows what they are called.  So for the record, the small vessels in the subcutaneous fat that get cut are superficial epigastrics (most people know this one) and the vessels that sometimes go during the lateral extension of the fascial incision are ascending branches of the deep circumflex iliac artery.  One can see that these ascending branches lie between above the transversalis muscle but beneath the obliques, which explains why sometimes taking the fascial layers separately allows one to miss them.  I’ve always felt that the routine sacrificing of these vessels was a surgical faux pas, and knowing this anatomy helps one to avoid it.

2. The small nerves we like to cut at cesarean have names, and we can avoid them.

Most patients that have cesareans notice a area of numbness above their incision that can last for months or even a year.  This is because there are several nerve cutaneous nerve branches that are often violated during a Pfanenstiel entry (the preferred method for a cesarean delivery.)  These nerves can be injured in two different parts of the entry.  During the extension of the fascial incision laterally, the anterior cutaneous branch of the iliohypogastric is in the strike zone, and if the incision is low enough, the ilioinguinal nerve is also in danger.  During the separation of the fascia from the rectus midline, the anterior branch of iliohypogastric is again in danger, but this time as a vertical band that goes from the belly of the rectus to the underside of the fascia.  Similarly, the cutaneous branch of T12 is in danger, but closer to the midline.

The non-surgeon audience may be horrified that these structures get damaged during a cesarean, but the surgeons know that small cutaneous nerves are often severed in surgical entry despite the best of intentions.  That said, understanding the anatomy allows one to avoid them with greater frequency.  For example, note how the anterior branch of iliohypogastric runs between the fascia of the external and internal obliques before it perforates the rectus fascia, and that it is running at the interface between the internal oblique muscle and its aponeurosis.  Even though the fascia may be opened wide enough to get to this nerve, with a little care one can visualize it and avoid it.  Similarly, if one takes care as the rectus fascia is dissected up off the midline one can preserve the neurovascular bundles of the distal iliohypogastric and T12.  If all these nerves are preserved, there should be no postoperative incisional numbness.  Its doable more often than not if you try.

3. The path of the arcus tendineous fascia pelvis

Every OB/GYN knows that this part of the anatomy is pretty confusing, and that the magic of urogynecologists is that they really understand it.  This is one of those things that I just really had confused.   The arcus is actually the aponeurosis of the levator ani (puborectalis, pubococcygeus, and iliococcygeus) and the obturator internus muscle.  The levators travel down off the arcus around the rectum and back up to the other side, while obturator internus comes down off the inside of the pelvis, bounces off the backside of the arcus, and then down and out onto the femur.  Arcus is the center of the connection of three structures – the obturator internus and its fascia, the levator ani, and the anterior vaginal wall.  Understanding this finally led me to better understand the idea of a paravaginal defect, which is that it is a separation of the anterior vaginal wall off the arcus.  Effectively, if there is a paravaginal defect, one could put a hole through the lateral vaginal mucosa and put a finger through that hole until they hit the pelvic peritoneum.  With the paravaginal connection to the arcus intact, a lateral dissection would run into the arcus before it got to the pelvic peritoneum.  We can also see how the arcus ends in the ischial spine, giving one a better idea of where the end of the paravaginal defect will be.  Oh, you urogyns get to have so much fun.

4. The medial umbilical ligament ends at the anterior hypogastric artery

Every OB/GYN dreads the day that they have so much bleeding at a cesarean that they have to consider a hypogastric artery ligation.  Some have even decided ahead of time they they aren’t comfortable enough with the retroperitoneal anatomy to do it, and if they are in that situation they are going to do a hysterectomy.   I was kind of in between until recently, but dissecting a pelvis really got me back into a comfort zone that would let me do that hypogastric dissection if I needed to.  One of the big pieces was the realization that the medial umbilical ligament running down the anterior abdominal wall is going to end in the hypogastric artery.    This structure is actually an obliterated umbilical artery, and in fetal life it coursed with blood, running deoxygenated blood from the fetus to the placenta.   Before this vessel obliterates, it gives off one or more superior vesicle artery branches to the bladder.

Ultimately this means you can open the retroperitoneum deep to the round ligament, identify the median umbilical on the anterior wall, and bluntly dissect with your fingers down this path to the hypogastric.  From there, one only needs to get distal to the posterior division and ligate, passing ones ligature lateral to medial.  Understanding this anatomy and being able to keep intraperitoneal bleeding out of the dissection, the hypogastric ligation is quite doable.  Its one of those things that most OB/GYNs think of as extremely difficult, but that people who know how to do it don’t think is so hard.  As the adage goes, “everything’s hard until you know how to do it”

5. Don’t F with the pancreas

Ok, I already knew this.  But looking at the amount of connections the pancreas has to its surrounding structures, it absolutely blows my mind that there are general surgeons that can remove this structure.  The uterus just has a few vessels and ligaments attached to it.  Easy peasy.   But the pancreas is serious invested in everything around it.   It has almost no free borders, many arterial connections, is attached to vascular supply of the spleen, and has a duct system that cannot be disconnected from the duodenum without removing a bunch of of the bowel and rerouting to restore some semblance of function (A Whipple).

Knowing this, it makes the following video all the more impressive.  In fact I can hardly believe it happening right in front of me.   A Whipple through a laparoscope, with every anastamosis hand sewn and intracorporeally tied.  Incredible.

Categories: Education, Gynecology
  1. November 7, 2010 at 4:53 pm

    i’ve always thought an anatomy refresher should be required for anyone after doing a surgical residency (including ob-gyn). THis was a nice short version! Thanks!


  2. VW
    November 7, 2010 at 8:13 pm

    May I ask a frivolous question that has been fascinating me for years? Is there an anatomical reason why when I stick my finger deep into my belly button until I reach a hard ridge and wiggle it around, I can feel almost a burning sensation in my urethra? I’m not kidding you (but don’t remember how I figured this out in the first place). Is there a nerve there? (sorry, I have a hard time decoding the anatomy speak above)


    • November 8, 2010 at 1:32 am

      There is no named structure there, but the urachus connects the bladder and the umbilicus (obliterated umbilical vein), which may transmit some small nerves along with it. Most likely that’s what’s transmitting this feeling. I think everyone has done this at one time or another.


  3. Jes
    November 9, 2010 at 4:20 pm

    Thread jack: Will my awful c-section “flap” ever go away? I was in great shape before I was pregnant and had really great core/ab muscles. Now I have this weird overhang, despite the fact that I’ve lost my baby weight and resumed an exercise schedule. Also, if I have more c-sections, will it get worse? Were my ab muscles ruined from pregnancy, the c-section, or both?


    • November 9, 2010 at 4:43 pm

      Hard to say without looking. Your ab muscles shouldn’t have been affected by a cesarean. Might want to talk to a plastic surgeon if you’re fully healed and don’t like the way it looks. Could just be post pregnancy changes though. Either way a good plastic surgeon can fix it. Would certainly wait until after you’re done childbearing though.

      Totally theoretical advice though – your ob can give you some idea of if what’s going on.


      • erica
        November 12, 2010 at 9:35 am

        Complete lay person here, but I was surprised that the ab muscles aren’t effected by a cesarean. Since this is an anatomy post, would you mind explaining how you cut into the abdomen without affecting the ab muscles? (Or is there a difference between what the person on the street thinks of as the abdomen and what is technically/anatomically the abdomen?)


      • November 12, 2010 at 4:02 pm

        The approach to a cesarean splits between the rectus abdominis muscles without cutting them. They get pulled aside and put back together in the center during closure.


  4. November 10, 2010 at 7:19 pm

    Very interesting! I just noticed recently that I had all the sensation back along my incision site, and my daughter is two years old. It wasn’t something that really affected me in any meaningful way, but now I know why. I still have the flap, too, but I’m pretty sure it has nothing to do with my abdominal muscles, which were and are quite strong, and everything to do with the fact that I’m still 20 lbs heavier than I was before I got pregnant.


  5. Kristy
    November 14, 2010 at 2:30 am

    You mention numbness that “can last for months or even a year.” Loads of anecdotal experience (yes, I know the pitfalls of those words…) suggest many women experience permanent numbness. What factors are at play in the severity and duration of numbness?


    • November 15, 2010 at 12:05 pm

      Peripheral nerves grow back at a rate of about 1 millimeter a week, so depending on where it gets cut it can take a variable amount of time to regrow. Typically these nerves will grow back in 6 months to a year – but one’s mileage (and nerve regrowth) may vary.


  6. VW
    November 28, 2010 at 12:47 pm

    Dr Fogelson, may I asked you a question about aneuploidy screening in pregnancy?

    I moved from the US to NZ when I was pregnant with my daughter at age 33. At the time, they offered only the Nuchal Translucency scan, but not the first trimester blood screen. THE NT scan gave me a risk of 1 in 33 for Down’s Syndrome. I then had the second-trimester blood screen done, with lowered my risk to 1 in 70, still not very reassuring. In the end, I had an amnio and a diagnosis of 46XX, but this whole time was very stressful for me, especially because I heard conflicting information regarding the reliability (or even possibility) of combining the NT scan results with the second trimester blood screen.

    I’m pregnant again, and the first trimester blood screen is now available along with the NT scan. I know this is a much more reliable screening combination, but I’m wondering if there is any research on subsequent pregnancies of women who have had screen positives with these tests. In other words, do we know if once you’ve screened positive, are you more likely to screen positive (but have a normal amnio result) again in subsequent pregnancies? Anecdotally, my sister-in-law received 1 in 24 and in 20 results for the combined first trimester screen and both her children were healthy, so I’m wondering if someone has looked into this because the results may influence my decision whether to pursue the combined first trimester screen this time around.

    Thank you for any information you may have!


    • November 29, 2010 at 4:02 pm

      Great question, and a complicated one. Will work on it as a blog post with lot of detail. In short, you should screen if you care if the baby has T21. If you don’t, don’t screen.


      • VW
        February 5, 2011 at 9:39 pm

        I’d still love to see a blog post on this topic, but I’m happy to report that after proceeding with the combined first trimester screening, I got a 1:2800 for DS, which seems pretty much the other end of the spectrum from the 1:33 I got with my daughter. A huge relief.


  7. Shane Marsh
    July 10, 2011 at 2:21 pm

    Fascinating, Nicholas, thanks for this. My twitter name is giddeygirl and I just started following both your twitter accounts.


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