Surface Anatomy of the Abdomen
Diaphragm
Surface anatomy of diaphragm
Standring (2015) found the surface anatomy of the diaphragm to be at end tidal inspiration to extend down to the right 5th intercostal space and left r6 both in the midlclavicular line. It can range from the 4th intercostal space to below the costal margin.
Anatomy of the thorax and diaphragmatic rib attachments
5th intercostal space attaches onto the lower part of the manubrium. It is formed between r5 and r6.
r7 costal cartilage forms the upper and lateral part of the epigastrium.
Diaphragmatic attachment to the ribs are r6-12.
Stomach (gastro-oesophageal margin) (Standring 2015)
Left of the midline posterior to the left r7 costal cartilage (upper and lateral part of the epigastrium). This is at the level of T11 (range T10-L1/2). Lower in females and higher in the obese.
Duodenum (Standring 2015)
The transpyloric plane (half way between xiphisternum --> umbilicus) lies at L1. This is the landmark that is palpated around to locate the duodenum:
D1: sometimes ascends above the transpyloric plane (L1).
D2: just to right of the midline L2-3.
D3: crosses the midline at L3.
D4: ascends to the left side of L2 reaching the transpyloric plane (L1).
D/J flexure: left side of L1 (T11-L3).
Suspensory ligament of the duodenum (ligament of Trietz): right crus of the diaphragm --> connective tissue around the superior mesenteric artery & coeliac artery --> D/J flexure. Suspends the D/J flexure. The surface anatomy of this ligament as well as its relations with the root of the small intestine mesentery, transverse mesocolon and renal fascia is discussed in 'superior mesenteric artery'.
Small intestine mesentery
Anatomy of the small intestine mesentery
Coffey and O’Leary (2017) found the mesentery to be suspended by the superior mesenteric artery alone, with a resultant tendency to twist around it. This suspension from the artery holds the mesentery up preventing it from collapsing down into the pelvis.
From this location, the mesentery fans out to span the entire gastrointestinal tract from the D/J junction to its termination at the distal mesorectum. Interestingly the attachments these authors describe parallel the work of Leonardo da Vinci.
The mesentery of the small and large intestine is thus likened to a Chinese fan.
The handle of the fan is the mesenteric root twisted around the superior mesenteric artery.
The leaves of the fan, the small intestine mesentery, flatten against the posterior abdominal wall, attached to it by a peritoneal reflection. This attachment is a line running from just to the left of L1 between T11-L3 (paralleling the D/J flexure on the posterior abdominal wall) and extends obliquely down to the right anterior sacroiliac region (paralleling the I/C junction on the posterior abdominal wall) and then onto the small intestine.
These leaves of the small intestine mesentery continue laterally forming the large intestine mesentery the mesocolon.
Okino et al (2001) found the root of the mesentery contiguous with:
Superiorly: hepatoduodenal ligament around the superior mesenteric vein and portal vein*.
Anteriorly: transverse mesocolon around the gastrocolic trunk and uncinate process of the pancreas. The gastrocolic trunk represents the convergence of the transverse mesocolon, greater omentum, and mesenteric root (Aldouri 2017).
Posterolaterally: ascending and descending mesocolons (anterior pararenal space).
Superior mesenteric artery and vein and the gastrocolic trunk pass through the root of the mesentery (Aldouri 2017)
*: the portal vein is formed at the confluence of the splenic vein and superior mesenteric vein. It passes into the liver via the hepatoduodenal ligament at the liver hilum.
The attachments of the root of the small intestine mesentery, transverse mesocolon, suspensory ligament of the duodenum (ligament of treitz) and anterior kidney fascia to the superior mesenteric artery is discussed under 'superior mesenteric artery'.
Surface anatomy of the root of the small intestine mesentery
The surface anatomy of the root of the small intestine mesentery is:
Root of the small intestine mesentery at the superior mesenteric artery: transpyloric plane close to the left midclavicular-umbilical line (left side of L1).
Follows an oblique line to attaching to the posterior abdominal wall by peritoneal reflections to ....
Termination of the small intestine mesentery at the right iliac fossa (anterior to the right sacroiliac joint): I/C junction
Large Intestine
Anatomy of the mesocolon
The mesocolon attaches the large intestine to the posterior abdominal wall and superior mesenteric artery.
Coffey et al (2015) found the ascending and descending mesocolon attaches the ascending and descending colon to the posterior abdominal wall via Toldt's fascia and the transverse mesocolon attaches the transverse mesocolon to the superior mesenteric artery.
The attachments of the ascending and descending mesocolon to Toldt's fascia is by its flattening against this tissue rather than by strong fibrous bonds.
The descending mesocolon is continuous at its superior end with the transverse mesocolon and at its inferior end with the mesosigmoid and mesorectum (+ Chang et al 2019).
The mesorectum is the fat surrounding the rectum. It blends superiorly with the sigmoid mesentery and extends down to the levator ani. It is enclosed by the mesorectal fascia.
The attachments of the transverse mesocolon, root of the small intestine, suspensory ligament of the duodenum (ligament of treitz) and anterior renal fascia is discussed under 'superior mesenteric artery'.
Surface anatomy of the large intestine
The surface anatomy of the large intestine corresponds to the midclavicular line (lateral border of rectus abdominis) and the transpyloric plane:
Ascending colon: on and just to the right of the midclavicular line.
Transverse colon: middle section goes through the transpyloric plane*.
Descending colon: on and just to the left of the midclavicular line.
Appendix: right lower quadrant abdomen. Highly variable. Rarely McBurney’s point.
*The middle section of the transverse colon going through the transpyloric plane corresponds to the transverse mesocolon attachments to the superior mesenteric artery (transpyloric plane close to the left midclavicular-umbilical line, refer 'superior mesenteric artery').
Liver (Standring 2015)
Inferior border
End tidal inspiration: right r10 costal cartilage in the midaxillary line --> left 5th costal interspace/r6 in the midclavicular line.
Superior border
Right r5 or intercostal space in the midclavicular line --> left 5th intercostal space/r6 in the midclavicular line
Gall Bladder (Standring 2015)
Fundus: tip of right 9th costal cartilage in or just below the transpyloric plane.
Spleen (Standring 2015)
Normal size spleen equates to that of a clenched fist.
It is located at the left r9 to 12 in anterior midaxillary line.
Medial border: 5cm to the left of T11 SP (PSIS to a line perpendicular to T11) --> lateral border: 3cm anterior to the midaxillary line.
Pancreas (Standring 2015)
The pancreas is located at the right side of L2 (in duodenal curve)
Neck: transpyloric plane (L1-2 IVD)
Body: slightly above transpyloric plane.
Kidney (Standring 2015)
Left kidney
The left kidney is located between r12(11) T12 --> L3/4
Renal hilum: L1/2 or L2.
Right kidney
The right kidney is located between r12(11) L1 --> L4 (T11-L5)
Renal hilum: slightly lower than L2.
The relations of the anterior renal fascia with the suspensory ligament of the duodenum (ligament of Treitz), root of the small intestine mesentery and transverse mesocolon is discussed under 'superior mesenteric artery'.
Ureter (Standring 2015)
The ureter is located in the transpyloric plane, (slightly lower on the right) 5cm from the midline (just medial to the tips of L1-5 TP’s). In pelvic cavity curves medial to the midline to enter the bladder.
Superior mesnteric artery
Anatomy of superior mesenteric artery
The origin of the superior mesenteric artery from the abdominal aorta is at L1 which corresponds to the transpyloric plane (half way between the xiphoid --> umbilicus) close to the left midclavicular-umbilical line. This is slightly to the right of the D/J junction.
The artery then descends to the right iliac fossa supplying along its course the pancreas and intestine (lower part of the duodenum --> appendix, ascending and transverse colon).
Connective tissue anatomy of the superior mesenteric artery
The superior mesenteric artery is an important landmark for the:
Anterior renal fascia.
Root of the small intestine mesentery and transverse mesocolon.
Suspensory ligament of the duodenum (ligament of Treitz).
Martin (1942) found below the superior mesenteric artery the anterior renal fascia crosses the midline to join the contralateral anterior renal fascia. Superior to the artery it covers the mass of connective tissue surrounding the origins of the coeliac axis (artery) and superior mesentery artery (in which lies the coeliac and superior mesenteric autonomic plexus).
Coffey et al (2015) found the root of the mesentery for the small and large intestine to start from where the superior mesenteric artery originates from the pancreatic bed (retroperitoneal space the pancreas and D1 shares).
Suspensory ligament of the duodenum (ligament of Trietz): double fold of peritoneum. It comprises two parts:
Part one: right crus of diaphragm --> connective tissue around coeliac and superior mesenteric artery.
Part two: muscular part which suspends D/J junction. Connective tissue around coeliac artery --> duodenum: between pancreas and left renal vein.
The suspensory ligament of the duodenum (ligament of Trietz) as well as suspending the D/J junction from the retroperitoneum surrounds and protects the superior mesenteric artery and coeliac trunk.
Surface anatomy
The superior mesenteric artery branches from the abdominal aorta in the transpyloric plane (L1) close to the left midclavicular-umbilical line.
References
Standring S. Gray’s Anatomy 41st edition. Anatomy. The anatomical basis of clinical practice
A NOTE ON THE RENAL FASCIA (1942) BY C. P. MARTIN
Mesenteric-Based Surgery Exploits Gastrointestinal, Peritoneal, Mesenteric and Fascial Continuity from Duodenojejunal Flexure to the Anorectal Junction. A Review (2015). J. Calvin Coffey, Mary E. Dillon, Rishabh Sehgal, Peter Dockery, Fabio Quondamatteo, Dara Walsh, Leon Walsh
Respiration-Induced Deformations of the Superior Mesenteric and Renal Arteries in Patients with Abdominal Aortic Aneurysms (2013). Ga-Young Suh, Gilwoo Choi, Robert J. Herfkens, Ronald L. Dalman and Christopher P. Cheng
Navigating the Root of the Mesentery: A Guided Approach to an Artery-First Pancreatoduodenectomy (2017). Amer Aldouri, M
Root of the Small-Bowel Mesentery: Correlative Anatomy and CT Features of Pathologic Conditions (2001). Yuriko Okino, Hiro Kiyosue, Hiromu Mori, Eiji Komatsu, Shunro Matsumoto, Yasunari Yamada, Koji Suzuki, Kenichiro Tomonari
Anatomical relationship between fascia propria of the rectum and visceral pelvic fascia in the view of continuity of fasciae (2019). Chang Y, Liu HL, Jiang HH, Li AJ, Wang WC, Peng J, Lyu L, Pan ZH, Zhang Y, Xiao YH, Lin MB
