Surgical Anatomy of the Abdomen

The abdominal cavity has a complex and intricate anatomy. A physician must know in which area of the abdomen every major structure is located to understand the clinical presentation of abdominal pathologies and/or in trauma situations to estimate which organs are most likely injured. The general surgeon, especially in emergency situations, uses this knowledge to execute the most advantageous surgical approach for a particular situation.

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Surface Anatomy of the Abdomen

Boundaries

Superior:

  • Xiphoid process
  • Costal cartilages of the 7th–10th ribs

Inferior:

  • Pubic bone and pubic symphysis
  • Inguinal ligaments

Lateral: 

  • Superior: inferior aspect of the 10th rib
  • Inferior: iliac crest

Landmarks

  • Umbilicus
  • Linea alba: fibrous junction of the right and left rectus muscles that runs down the midline of the abdomen 
  • Semilunar lines: lateral borders of the rectus abdominis muscles
  • Anterior superior iliac spine
  • Iliac crests 
  • Pubic symphysis
  • Inguinal grooves
Superficial anatomical landmarks abdomen

Superficial anatomical landmarks of the abdomen

Image by Lecturio. License: CC BY-NC-SA 4.0

Lines and planes

The following divide the abdomen into its 9 regions:

  • Right and left midclavicular lines
  • Subcostal plane
  • Transtubercular, or intertubercular, plane

Regions of the abdomen

  • Right and left hypochondria
  • Epigastrium
  • Right and left lateral abdominal regions or flanks 
  • Umbilical
  • Right and left inguinal regions or iliac fossae 
  • Hypogastrium

Dermatomes

  • T7–L1
  • Visceral pains are named according to their respective dermatomes. 
Dermatomes of the thorax, abdomen, and pelvis

Dermatomes of the thorax, abdomen, and pelvis

Image by Lecturio. License: CC BY-NC-SA 4.0

Abdominal wall

Layers

  • Skin
  • Superficial fascia (subcutaneous tissue):
    • Superficial fatty layer (Camper’s fascia) 
    • Deeper membranous layer (Scarpa’s fascia)
  • Anterior fascial layer:
    • Anterior rectus sheath (medial)
    • External abdominal oblique fascia (lateral)
  • Abdominal muscles:
    • Rectus abdominis
    • External abdominal oblique
    • Internal abdominal oblique
    • Transversus abdominis
  • Posterior fascial layer:
    • Posterior rectus sheath (medial; ends at the arcuate line midway between umbilicus and pubic symphysis)
    • Transversalis fascia (lateral)
  • Peritoneum
Diagram of the layers of abdominal wall

Layers of abdominal wall

Image: “Gray399” by Henry Gray. License: Public Domain, edited by Lecturio.

Relevant procedure

Ventral herniorrhaphy: surgical repair of hernias of abdominal wall

Right Hypochondrium

The surgically relevant structures of the right hypochondrium include the liver and the biliary tree.

Liver

Location: 

  • ¾ in the RUQ
  • Adjacent to the inferior surface of diaphragm
  • Location is breath-dependent (rises during exhalation, lowers during inhalation).
Location of the liver in the right hypochondrium and epigastrium

Location of the liver in the right hypochondrium and epigastrium

Image by Lecturio. License: CC BY-NC-SA 4.0

Limits:

  • Superior: 5th intercostal space during exhalation
  • Inferior: right costal arch during inhalation 

Surfaces: 

  • Diaphragmatic and visceral
  • Liver is intraperitoneal except for bare area, porta hepatis, and gallbladder fossa.
  • Enclosed in the Glisson capsule (external layer of fibrous connective tissue)

Biliary tree

Gallbladder:

  • Bile-filled sac located in a fossa on the inferior aspect of the liver beneath the junction of hepatic segments Ⅳb and Ⅴ
  • 7–10 cm in length, average capacity 30–50 mL
  • Anatomic divisions:
    • Fundus (superiormost aspect)
    • Corpus (body)
    • Infundibulum (round, blind end extending below the liver margin)
    • Neck (connects with cystic duct)
  • The cystic duct connects the gallbladder to the biliary tree.

Biliary tree:

  • The right and left hepatic ducts join to form the common hepatic duct.
  • The cystic duct joins the common hepatic duct to form the common bile duct.
  • The cystic duct length is highly variable.
Anatomy of the gallbladder and the biliary tree

Anatomy of the gallbladder and the biliary tree

Image by Lecturio. License: CC BY-NC-SA 4.0

Relevant procedures

  • Cholecystectomy (open and laparoscopic): surgical removal of the gallbladder, usually because of cholelithiasis (gallstone disease) with or without cholecystitis
  • Choledochostomy: surgical incision on the common bile duct
  • Choledochojejunostomy: anastomosis of a common bile duct to the jejunum (for oncologic resections or treatment of common bile duct injuries)
  • Hepatic lobectomy: surgical removal of a lobe of the liver
  • Hepatic segmentectomy: surgical removal of a segment of the liver
  • Needle biopsy of the liver
  • Hepatic abscess drainage
Laparoscopic cholecystectomy

Incisions for open (left) and laparoscopic (right) cholecystectomy

Image by Lecturio. License: CC BY-NC-SA 4.0

Epigastrium

The epigastrium contains the transverse colon, the duodenum, and the pancreas.

Transverse colon

  • Part of the colon distal to the ascending colon and proximal to the descending colon that travels transversely across the upper abdomen
  • Suspended by mesentery (transverse mesocolon)
  • Supplied by ileocolic and middle colic branches of the superior mesenteric artery
  • Venous drainage is through the superior mesenteric vein that joins the portal vein.
Colon in situ covered by the greater omentum

Colon in situ, covered by the greater omentum

Image by BioDigital, edited by Lecturio

Duodenum

  • First C-shaped segment of the small intestine
  • Surrounds the head of the pancreas
  • Consists of 4 segments
  • The 2nd, or descending, segment contains the ampulla of Vater (opening of the common bile duct).
  • 1st segment (duodenal bulb): intraperitoneal
  • Descending, horizontal, and ascending parts: retroperitoneal
  • Ends at duodenojejunal flexure: fixed to the posterior abdominal wall by the ligament of Treitz
Anatomy of the gallbladder and the biliary tree (cholecystectomy)

Duodenum and its relation with the pancreas and biliary ducts

Image by Lecturio. License: CC BY-NC-SA 4.0

Pancreas

Segments:

  • Caput pancreatis (head)
  • Uncinate process
  • Collum pancreatis (neck)
  • Corpus pancreatis (body)
  • Cauda pancreatis (tail): the only intraperitoneal segment of the pancreas 

Ducts:

  • Pancreatic duct (Wirsung’s duct) and common bile duct open into ampulla of Vater, which presents as major duodenal papilla.
  • Major duodenal papilla contains the hepatopancreatic sphincter (sphincter of Oddi), which regulates the secretion of bile and pancreatic fluid.
  • Accessory pancreatic duct (when present) opens into minor duodenal papilla.
The pancreas

Different parts of the pancreas and its surroundings

Image: “The pancreas” by OpenStax College. License: CC BY 3.0

Relevant procedures

  • Transverse colostomy: an opening along the length of the transverse colon to the exterior skin surface
  • Transverse hemicolectomy: surgical removal of the transverse colon
  • Pancreaticojejunostomy (Puestow procedure): surgically made communication between the pancreas and the jejunum (treatment of chronic pancreatitis)
  • Pancreaticoduodenectomy (Whipple procedure): surgical removal of the head of the pancreas and the duodenum
  • Distal pancreatectomy: removal of the body and tail of the pancreas
  • Total pancreatectomy: surgical removal of the pancreas

Left Hypochondrium

The most important structures of the left hypochondrium are the spleen and the stomach.

Spleen

Location:

  • Positioned against ribs 9–11
  • Intraperitoneal

Relations:

  • Anterior: stomach
  • Lateral: abdominal muscles
  • Medial: left kidney
  • Posterior: diaphragm
  • Inferior: colon and left colic flexure

Ligaments:

  • Gastrosplenic
  • Splenorenal
  • Phrenicocolic

Blood supply: splenic artery and vein

Stomach

Segments:

  • Has 2 curvatures (lesser and greater) 
  • Cardia: 
    • Entrance of the stomach
    • Originates from the z-line and creates the angle of His, or angle of the cardiac orifice (the angle between the fundus and abdominal esophagus)
    • Crucial landmark in the construction of the gastric pouch 
  • Fundus: a dome-shaped region located at the highest point of the stomach
  • Body: 
    • Main section of the stomach
    • Extends from the fundus to the pylorus
    • Bordered by the lesser and greater curvatures
  • Pylorus: 
    • Connects to the duodenum
    • Contains the pyloric sphincter
    • Consists of a wide pyloric antrum and narrow pyloric canal

Arterial supply:

  • Left gastric artery: main supply of the gastric pouch in a gastric bypass
  • Right gastric artery
  • Right and left gastroepiploic (gastro-omental) arteries
  • Splenic artery
  • Short gastric arteries
  • Posterior gastric artery

Venous drainage:

  • Homonymous veins that accompany the arteries
  • Right and left gastric veins drain into the portal vein.
  • Left gastroepiploic vein drains into the splenic vein.
  • Right gastroepiploic vein drains into the superior mesenteric vein.

Innervation:

  • Parasympathetic innervation: anterior and posterior vagal trunk
  • Sympathetic innervation: greater splanchnic nerve and gastric branches from celiac plexus
Blood supply and innervation of the stomach

Blood supply and innervation of the stomach

Image by BioDigital, edited by Lecturio

Relevant procedures

  • Splenectomy: surgical removal of the spleen
  • Splenorrhaphy: surgical repair of the spleen, usually performed after trauma
  • Bariatric surgery: group of invasive procedures that surgically reduce the size of the stomach to produce early satiety and decrease food intake (restrictive type) and/or alter digestion and artificially induce malabsorption of nutrients (malabsorptive type).
  • Total and subtotal gastrectomy: surgical removal of a part of or an entire stomach (for oncologic resections and gastric ulcers)
  • Truncal or selective vagotomy: transection of the vagal nerves or branches that can be combined with partial gastric resections to control acid secretion and prevent ulcer recurrence

Right and Left Flanks

Ascending and descending colon

  • Ascending and descending portions of the large intestine found in the right flank and the left flank, respectively
  • Arterial supply: superior and inferior mesenteric arteries
  • Venous drainage: superior and inferior mesenteric veins that join portal circulation
Colon blood supply, anterior view

Colon in situ, anterior view, with the greater omentum and small intestines removed

Image by BioDigital, edited by Lecturio

Kidneys

Location:

  • Between T12 and L3, in the paravertebral gutter
  • Their superior pole rests at the level of the 11th and 12th ribs.
  • The parietal peritoneum anchors them to the posterior abdominal wall. 
  • Retroperitoneal

Renal capsule:

  • Holds the kidneys in position
  • Consists of:
    • Paranephric adipose tissue (fat)
    • Renal fascia

Relations:

  • Superomedially: adrenal glands
  • Posteriorly:
    • Nerves: subcostal, iliohypogastric, ilioinguinal
    • Muscles: diaphragm, quadratus lumborum

External characteristics:

  • Superior pole
  • Inferior pole
  • Convex lateral surface
  • Concave medial surface: renal hilum

Blood supply: renal arteries and veins

Transverse cross section of the abdomen focused on the kidneys

Transverse cross section of the abdomen focused on the kidneys:
Note how the kidney is embedded in adipose tissue within the gutters (paranephric and perinephric fat), which is continuous with the fat in the renal sinuses.

Image by Lecturio. License: CC BY-NC-SA 4.0

Relevant procedures

  • Right hemicolectomy: surgical removal of the right segment of the transverse colon and ascending colon
  • Left hemicolectomy: surgical removal of the left segment of the transverse colon and descending colon
  • Nephrectomy: surgical removal of the kidney
  • Kidney transplantation: surgical implantation of a donated kidney

Umbilical Region

Small intestine

  • Average length: 6–7 m
  • Segments:
    • Duodenum
    • Jejunum
    • Ileum

Blood supply: 

  • Duodenum: superior and inferior pancreaticoduodenal arteries
  • Jejunum and ilium: jejunal arteries and ileal arteries
    • Form anastomotic loops that run parallel to the small intestine = arcades
    • Small branches leave these arcades = vasa recta (or straight arteries)
  • Venous drainage: portal system
Small intestine and its parts

Small intestine and its parts

Image: “2417 Small IntestineN” by OpenStax College. License: CC BY 3.0

Abdominal aorta

  • Retroperitoneal
  • Extending from the aortic hiatus of the diaphragm (T12) to its bifurcation into the common iliac arteries (L4)

Vascular branches: 

  • Unpaired (forward branches):
    • Celiac trunk
    • Superior mesenteric 
    • Inferior mesenteric 
  • Paired visceral (lateral): 
    • Renal
    • Gonadal
  • Paired parietal (posterolateral): inferiormost intercostal

Relevant procedures

  • Small intestine resection: surgical removal of a segment of the small intestine, usually because of adhesions, volvulus, obstruction, and regional ileitis
  • Ileostomy: surgically made communication between the ileum and the skin 
  • Aortic aneurysm repair using grafts

Right and Left Inguinal Regions (Iliac Fossae)

Appendix

  • Also referred to as vermiform appendix
  • Slender, hollow, blind-ended pouch arising from the proximal cecum
  • The appendiceal orifice is always located at the confluence of the taenia coli.
  • On average, the appendix is approximately 9 cm long, but it can vary from 2 to 22 cm.

McBurney’s point:

  • Junction between the lateral and medial thirds of a line drawn from the anterior superior iliac spine (ASIS) to the umbilicus
  • Localized tenderness at this point is a classic sign of appendicitis.
  • Both McBurney’s and Rocky-Davis incisions for open appendectomy are performed through this point.

Inguinal canals

Boundaries:

  • Superior: inferior edge of the internal oblique and transverse abdominal muscles
  • Inferior: inguinal ligament (continuation of the external abdominal oblique aponeurosis)
  • Anterior: aponeurosis of the abdominal external oblique muscle
  • Posterior: transversalis fascia and interfoveolar ligament

Course:

  • The inguinal canal is approximately 4 cm long, situated in the lower anterior abdominal wall, connecting its outer and inner layers above the inguinal ligament (superior anterior iliac spine to pubic tubercle).
  • Runs from an upper lateral to an inferior medial direction.
  • Inner orifice/deep inguinal ring: evagination of the transversalis fascia (surrounding the spermatic cord as the internal spermatic fascia)
  • External orifice/superficial inguinal ring: fissure in the aponeurosis of the abdominal external oblique muscle
The layers of the anterior abdominal wall

The layers of the anterior abdominal wall, depicting the course of the inguinal canal and the composition of the deep and superficial inguinal rings

Image by Lecturio. License: CC BY-NC-SA 4.0

Contents:

  • Men: 
    • Spermatic cord (cremaster muscle, internal and external spermatic fasciae surrounding the vas deferens, pampiniform plexus, lymphatic vessels, testicular neurovasculature, and tunica vaginalis)
    • Ilioinguinal nerve
    • Genital branch of the genitofemoral nerve
  • Women: 
    • Round ligament and artery
    • Ilioinguinal nerve 
    • Genital branch of the genitofemoral nerve
Boundaries and contents of the male inguinal canal

Boundaries and contents of the male inguinal canal
Note that the ilioinguinal nerve runs along the inguinal canal externally from the spermatic cord.

Image by Lecturio. License: CC BY-NC-SA 4.0

Descending and sigmoid colon

  • Suspended by mesentery (sigmoid mesocolon)
  • Arterial supply: inferior mesenteric artery (sigmoid arteries)
  • Venous drainage: inferior mesenteric vein → portal vein

Fallopian tubes

Segments:

  • Uterine (intramural)
  • Isthmus
  • Ampulla
  • Infundibulum (opens into the peritoneal cavity)

Broad ligament (ligamentum latum):

  • Runs from the uterus to the lateral pelvic wall
  • Contains the fallopian tubes
  • Segments:
    • Mesometrium (uterine part of the ligament)
    • Mesosalpinx (tubal part of the ligament)
    • Mesovarium (ligament to the ovary)

Blood supply:

  • Arterial: ovarian and uterine arteries
  • Venous supply is from ovarian veins: 
    • The right ovarian vein drains into the inferior vena cava.
    • The left ovarian vein drains into the left renal vein.

Relevant procedures

  • Appendectomy: surgical removal of the vermiform appendix, most commonly because of appendicitis
  • Inguinal herniorrhaphy: surgical repair of inguinal hernias; can be done laparoscopically or via an open approach (Lichtenstein technique is the most common)
  • Salpingectomy: surgical removal of the fallopian tube, commonly performed to treat ectopic pregnancy
  • Salpingostomy: incising the fallopian tube open, commonly to remove an occupying lesion (ectopic pregnancy), leaving the remainder of the tube intact
  • Sigmoid colectomy: surgical removal of a sigmoid colon, commonly performed for cancer or diverticulitis
  • Rectosigmoidectomy: surgical removal of the sigmoid colon and rectum
  • Descending colon colostomy

Hypogastrium

Urinary bladder

  • In females, the urinary bladder is anterior to the uterus and anterior vaginal wall. 
  • In males, it is anterior to the rectum.
  • Anchored by median umbilical ligament

Prostate

Location: 

  • Surrounding the neck of the urinary bladder
  • Inferior to the pubic symphysis and anterior to the rectal ampulla

Lobes:

  • Anterior lobe (isthmus): located anterior to the urethra 
  • Posterior lobe:
    • Posterior to urethra
    • Inferior to ejaculatory ducts
  • Lateral lobes: located on either side of the urethra 
  • Median lobe: lies between the urethra and ejaculatory ducts

Related structures:

  • The urethra enters the prostate near its anterior border and usually passes between its anterior and middle thirds.
  • The ejaculatory ducts pass anteroinferiorly through its posterior region to open into the prostatic urethra.

Accessory glandular structures:

  • Seminal vesicles
  • Bulbourethral glands (Cowper’s glands)
Prostate gland and main prostate zones

Prostate gland and main prostate zones:
Peripheral, transitional, and central zones in relation to other structures of the male genitourinary system
Note how the prostate is positioned around the prostatic urethra.

Image: “Prostate zones” by Mikael Häggström. License: CC0 1.0

Uterus

Location:

  • 7–9 cm long, found within the pelvis, connected to the end of the vaginal canal via the uterine cervix 
  • Dorsal to the urinary bladder, anterior to the rectum, in an anteverted and anteflexed position
  • Rectovaginal space or Douglas pouch: lowermost recess of the peritoneum, located between the uterus and rectum
  • Vesicouterine pouch: shallower pouch between urinary bladder and uterus

Structure:

  • Fundus: comprises all the uterus superior to the fallopian tubes
  • Body: region between the fundus and cervix
  • Isthmus: the narrowing at the cervix–body transition
  • Cervix: comprised of the internal orifice (aperture to the uterine body), cervical canal, and the external orifice (vagina–cervical canal junction)

Supporting structures:

  • Broad ligament
  • Round ligament (ligamentum teres) runs from the tubouterine junction through the inguinal canal to the labia majora. Corresponds to the vas deferens in men.
  • Cardinal ligament (ligamentum transversum cervicis) consists of the transversalis fascia connecting the cervix with the pelvic wall. 

Blood supply: 

  • Arterial:
    • Primary supply: uterine artery, a branch of the anterior division of the internal iliac artery, located in the broad ligament
    • Secondary supply: ovarian artery, which originates from the aorta at the level of L2
  • Venous: Uterine veins drain into internal iliac veins.
Blood supply of the uterus and ovaries

Blood supply of the uterus and ovaries:
Note the ovarian artery traveling along the ovarian suspensory ligament, supplying both the ovaries as well as the lateral ⅓ of the uterine tube. The ovarian artery continues in the mesosalpinx to anastomose with branches of the uterine artery.

Image by Lecturio. License: CC BY-NC-SA 4.0

Relevant procedures

  • Cystotomy: surgical incision performed on the urinary bladder for repair (cystoplasty), bladder laceration, or rupture due to trauma or a defect in the bladder wall
  • Cystectomy: surgical removal of the urinary bladder, usually indicated by malignancy
  • Urostomy: surgically made communication between the bladder and skin to facilitate evacuation of bladder contents
  • Abdominal hysterectomy: surgical removal of the uterus via an infraumbilical midline laparotomy
  • C-section: delivery of a fetus via a horizontal incision (Pfannenstiel or Joel-Cohen)
  • Suprapubic prostatectomy: surgical removal of the prostate via an infraumbilical midline laparotomy

References

  1. Blackbourne, L. (2015). Surgical Recall. Philadelphia: Wolters Kluwer Health.
  2. Phillips, N., Hornacky, A. (2021). Berry & Kohn’s Operating Room Technique. St. Louis: Elsevier.
  3. Rothrock, J., McEwen, D. (2019). Alexander’s Care of the Patient in Surgery. St. Louis: Elsevier.

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