Abdomino-pelvic Overview

 

 

Reading Assignment

Chapters: 5 & 6

 

 

<          The abdomino-pelvic region is the most variable region that you will encounter - either in this course, or clinically.  Added to this is the fact that there are significant differences between the male and female - especially in the pelvic region.  The intra-abdominal region is also prone to variability based on the amount of intra-abdominal adipose that is present. 

 

 

Applied Anatomy Concepts

(Questions from this segment will appear on the written portion of Exam II.)

 

            Migration of certain organs (e.g., the testes) during embryonic development complicates the understanding of clinically important concepts such as lymphatic drainage.  The testes actually start development in the abdominal cavity, in close approximation to the kidneys.  Eventually they migrate down to the anterior-inferior region, and commence their decent through the inguinal canal and on into the scrotum.  The opening at each end of this inguinal canal is often termed an inguinal ring, and can sometimes be larger than necessary for the descent of the testes.  In these cases, it is possible for abdominal viscera (mostly intestines or colon) to migrate down the inguinal canal towards the scrotum.  This condition is often termed an inguinal hernia. 

 

            Intra-abdominal (intra-coelomic) fat, as opposed to sub-cutaneous fat, can actually help with certain imaging modalities.  This is due to the fact that the various organs of the abdomino-pelvic cavity are separated by the intra-abdominal fat - thus making the structures easier to differentiate.  Some of the fat can be stored in the epiploic appendages, while a significant amount can be found in the greater omentum.

 

            The concept of the "peritoneal cavity" is quite challenging - as are the terms "intra-peritoneal" and "retro-peritoneal".  Hopefully you will eventually be able to understand the relationships between retro-peritoneal organs such as the kidneys, and intra-peritoneal organs like the stomach.  These relationships become very important clinically, especially in situations involving hemorrhage.

 

            In actuality, there are no true anatomical structures that reside inside of the peritoneal cavity. Structures are either totally surrounded by peritoneum (intraperitoneal), or they are partially enveloped (retroperitoneal). 

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`            CLINICAL CASE:  In 1988, a University of Illinois Vet student was murdered in Urbana.  She was stabbed once in the lateral abdomen.  There was no significant blood at the scene or in the ambulance that transported her to the ED of a local hospital.  Upon arriving at the ED, she appeared to be in shock, and exhibited signs of "bleeding out" - though, again, no significant blood was found associated with either her apartment or the ambulance.  Exploration of the peritoneal cavity showed no significant blood, nor did a similar examine of the thoracic cavity.  Things went from bad to worse, and she was eventually scheduled for exploratory surgery.  Complications ensued, and she eventually died.  (The family sued the hospital and settled out of court for a significant amount of money.)  As you might expect, the object that she was stabbed with actually tore the aorta, and all of the bleeding was retroperitoneal. This explains the fact that no blood was found upon examining the peritoneal cavity.  The anatomical correlation is that the great vessels are located behind the peritoneum, i.e., they are retroperitoneal.

 

        IF YOU ARE HAVING DIFFICULTY UNDERSTANDING THE CONCEPT OF INTRA AND RETROPERITONEAL - PLEASE FEEL FREE TO STOP BY MY OFFICE FOR A BRIEF TUTORIAL!!!!  THIS IS MUCH EASIER TO EXPLAIN IN PERSON THAN IT IS VIA KEYBOARD AND DISPLAY SCREEN:) - jm

 

                CLINICAL CASE:  Notice in the above diagram that the bladder is technically below the peritoneal cavity.  Thus, a needle (clinically called a suprapubic catheter) can be inserted immediately above the pubic symphysis in order to decompress a bladder that is distended secondary to urethral obstruction.  This does not involve any entry into the peritoneal cavity.    

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                The following is a short list of important anatomical relationships in either the abdominal or pelvic cavities:

 

            •    The right kidney is generally displaced inferiorly by the presence of the liver.  Thus, the left kidney is usually seen first when progressing from cranial to caudal.

 

            •    Vascular reference points:  It is important to know the sequence of the 4 major arteries emerging from the anterior abdominal aorta.  From cranial to caudal they are:  celiac trunk a., superior mesenteric a., renal a (2), and the inferior mesenteric artery.

 

            •    The GI system undergoes significant counterclockwise rotation during embryonic formation.  The actual junction of the ileum and cecum originates midline of the abdominal cavity.  It then rotates (around an axis through the umbilicus) a total of 270° so that it is at its normal location - the right lower quadrant of the abdominal cavity. (LINK to gut rotation images.)

 

            •    In most individuals, the appendix is easily visualized upon entering the abdominal cavity - either surgically or laparoscopically. Occasionally, however, the surgeon cannot initially visualize the appendix - the patient seems to have already had an appendectomy.  In actuality, the appendix is present, but is "trapped" between the posterior surface of the cecum and the posterior abdominal wall.  Stated another way - it is hiding "behind" the cecum.  This condition is known as a retrocecal appendix.