The anterior abdominal wall and peritoneum, MMed Anatomy, Imaging

Lesson10, The anterior abdominal wall and peritoneum, MMed Anatomy, Imaging

Imaging methods

v  Peritoneum

Ø  CT Contrast (standard)

§  Gastrograffin – peritoneal collections of fluid or masses

§  IV Contrast – blood vessels and peritoneal reflections

Ø  MRI  Degraded by peristalsis and respiration movement

Ø  US Limited by reflections of bowel gas. Used for focal masses.

Ø  Conventional Radiography, with contrast is superseded by CT.

v  Anterior abdominal wall

Ø  CT (standard)

Ø  MRI limited by respiratory movement

Ø  US useful for focal masses

Ø  Conventional Radiography No place in evaluation of anterior abdominal wall

Anatomy of the peritoneum Grants p122   

Males: Closed sac

Females: Penetrated by the fallopian tubes

Potential space between the parietal peritoneum lining the abdominal wall, and visceral peritoneum lining the organs.

The greater and lesser omental bursa communicate via the epiploic foramen (foramen of Winslow). The flow of intraperitoneal fluid determines disease spread, and is directed by gravity.

Peritoneal ligaments, mesenteries, and omenta serve as boundaries for disease processes and also for disease spread.

In an infant, the omental bursa (lesser sac) is an isolated part of the peritoneal cavity, lying dorsal to the stomach and extending superiorly to the liver and diaphragm (superior recess of the omental bursa) and inferiorly between layers of the greater omentum (inferior recess of the omental bursa).

In an adult, after fusion of the layers of the greater omentum, the inferior recess of the omental bursa now extends inferiorly only as far as the transverse colon.

  

Peritoneal spaces

Transverse colon and it’s mesentery divide the peritoneal spaces into the supramesocolic and inframesocolic space. The root of the transverse colons mesentery extends from the infraampullary segment of the descending duodenum, the head of the pancreas and continues on the lower edge of the body and tail of the pancreas.

v  The supramesocolic compartment

Ø  The right supramesocolic space

Ø  The right subphrenic space

Ø  The right subhepatic space

Ø  The lesser sac

Ø  Left supramesocolic space

Ø  The left anterior anterior perihepatic space

Ø  The left posterior perihepatic space

Ø  The left anterior subhepatic space

Ø  The left posterior subhepatic space (perisplenic) space

v  The inframesocolic space

Ø  The inframesocolic compartment

Ø  The right inframesocolic space

Ø  The left inframesocolic space

Ø  The paracolic gutters

Ø  The pelvic peritoneal spaces

Peritoneal reflections

v  Peritoneal Ligaments

Ø  The right coronary ligament

Ø  The gastrosplenic ligament

Ø  The falciform ligament

Ø  The phrenicocoliac ligament

Ø  The splenorenal ligament

Ø  The hepatoduodenal ligament

Ø  The dudenocoliac ligament

v  Mesenteries

Ø  Small bowel mesentery

Ø  The transverse mesocolon

Ø  The sigmoid mesocolon

Ø  The mesoappendix

v  Omenta

Ø  The greater omentum

Ø  The lesser omentum (gastrohepatic ligament)

Anatomy of the anterior abdominal wall

v  The superficial fascia

v  Muscles

Ø  Rectus Abdomini

Ø  The external oblique

Ø  The Internal Oblique

Ø  The transverse Abdominis

v  Transverse Fascia

v  The extraperitoneal connective tissue

The root of the mesentery of the small intestine: 15 to 20 cm in length. Extends between the duodenojejunal junction and the ileocecal junction.

Chron’s disease and Ulcerative colitis. Chronic inflammation of the colon (Chron’s disease and Ulcerative colitis) is characterised by chronic inflammation and ulceration of the colon and rectum.  In some patients a colectomy is performed, during which the terminal ileum, and colon as well as the rectum and anal canal is removed. An ileostomy is then constructed to establish an artificial cutaneous opening between the ileum and the skin of the anterolateral abdominal wall.

Lesson11, The gastrointestinal tract, MMed Anatomy, Imaging

Clinical

Duodenal ulcers. Most inflammatory erosions of the duodenal wall, duodenal (peptic) ulcers, are in the posterior wall of the superior (1^st ) part of the duodenum within 3 cm of the pylorus. (Grants p134).

Large Intestine: the features of the large intestine are the taeniae coli; haustra; and omental appendices.  

The descending colon is the narrowest part of the large intestine and retroperitoneal.

Barium enema and colonoscopy of colon: (grant’s p138)

v  Single contrast study: A barium enema has filled the colon

v  Double contrast Study: Barium can be seen coating the walls of the colon, which is distended with air (the double contrast per Dr F Joseph, UP), providing a vivid view of the mucosal relief and haustra.

v  Diverticulosis:

Ø  Fiberoptic Flexible Colonoscopy: The interior of the colon can be observed with an elongated endoscope, usually fiberoptic flexible colonoscope. The endoscope is a tube that inserts into the colon through the anus and rectum.

Ø  Diverticulosis of the colon can be photographed through a colonoscope. (does this mean that there is diverticulosis elsewhere in the GIT?)

Ø  Diverticulosis is a disorder in which multiple false diverticula (external evaginations or out-pocketing of the mucosa of the colon) develop along the intestine. It primarily affects middle aged or elderly people. Diverticulosis is commonly (60%) found in the sigmoid colon. Diverticula are subject to infection and rapture, leading to diverticulitis, and they can distort and erode the nutrient arteries, leading to hemorrhage.

Ilead diverticulum of Meckle. Ilial diverticulum is a congenital anomaly that occurs in 1 to 2 % of persons. It is a pouch like remnant (3 to 6 cm long) of the proximal part of the yolk sac, typically within 50 cm of the ileocecal junction. It sometimes becomes inflamed and produces pain that may mimic that produced by appendicitis. Grant p139.

Appendicitis: Acute inflammation of the appendix is a common cause of acute abdomen (severe abdominal pain arising suddenly). The pain of appendicitis usually commences as a vague pain in the periumbilical region because of the afferent pain fibres enter the spinal cord at the T10 level. Later, severe pain in the right lower quadrant results from irritation of the parietal peritoneum lining the posterior abdominal wall.

Superior Mesenteric Artery

Ø  The superior mesenteric artery ends by anastomosing with one of its own branches, the ilial branch of the ileocolic artery.

Ø  Vasa recta from the Arterial arcades of the Jejunum are longer than the short vasa recta of Arterial Arcades the Ileum.

Ø  The left renal vein, duodenum and uncinate process pass between the superior mesenteric artery and the aorta. Compressed.

Ø  Ileus of the paralytic type:

§  Occlusion of the vasa recta: by emboli results in ischemia of the part of the intestine concerned. If the ischemia is severe, necrosis of the involved segment results and ileus (obstruction of the intestine) of the paralytic type occurs. Ileus is accompanied by severe colicky pain, along with abdominal distension, vomiting, and often fever and dehydration. If the condition is diagnosed early by superior mesenteric angiogram, the obstructed part of the vessel may be cleared surgically.

Inferior Mesenteric Artery. Grant 142

v  The inferior mesenteric artery arises about 4 cm superior to the aortic bifurcation and crosses the left common iliac vessels to become the superior rectal artery

v  Branches seen on inferior mesenteric angiogram

Ø  Left colic artery

§  Ascending and Descending branches

Ø  Several Sigmoidal Arteries (Four)

§   (The inferior two sigmoidal arteries branch from the superior mesenteric artery)

Ø  Superior Rectal Artery

§  Supplies the rectum,

Ø  the superior rectal anastomoses is formed by the branches of the middle and inferior rectal arteries (from internal iliac artery)

v  Critical point: the point at which the last artery to the colon branches from the superior rectal artery is known as the critical point; this branch has no anastomotic connections with the superior rectal artery.

Lesson12, The Liver, MMed Anatomy, Imaging

Clinical

v  Liver biopsy Hepatic tissue may be obtained for diagnostic purposes by liver biopsy. The needle puncture is commonly made through the right 10^th intercostal space in the midaxillary line. Before the physician takes the biopsy, the person is asked to hold his breath in full expiration  to reduce the costodiaphragmatic recess and to lessen the possibility of damaging the lung and contaminating the pleural cavity.

v  Liver Coronary Ligaments to Diaphragm. The three parts of the coronary ligaments are attached to the diaphragm, except the inferior Vena Cava, suprarenal gland and kidney intervene.

v  Function of the Liver:

Ø  with the exception of lipids, every substance absorbed by the alimentary tract is received first by the liver, via hepatic portal vein.

Ø  liver stores glycogen and secretes bile

v  Cirrhosis of the liver: there is progressive destruction of hepatocytes in cirrhosis of the liver and replacement by fibrous tissue. This tissue surrounds the intrahepatic blood vessels and bile ducts, making the liver firm and impeding circulation of blood through it.

v  Hepatic Segmentation. Since the right and left hepatic arteries and ducts and branches do not communicate, it is possible to perform hepatic lobectomies (removal of the right or left lobe of the liver) and segmentectomies. There are 7 segments. Grant p151.

v  Portal triad:

v  Portosystemic Shunt: A Common method for reducing portal hypertension is to divert blood from the portal venous system to the systemic venous system by creating a communication between the portal vein and the IVC. This portacaval anastomoses of portosystemic  shunt may be created where these vessels lie close to each other

Ø  posterior to the liver.

Ø  Note the proximity of the splenic vein and the left renal vein, enabling a splenorenal shunt to be established surgically to relieve portal hypertension. The splenorenal ligament containing splenic artery and vein.

v  Vessels in potal triad Grants p153

v  ERCP. Endoscopic Retrograde Cholangiography and Pancreatography demonstrates the bile and pancreatic ducts.

Ø   Left and right hepatic ducts collect bile from the liver. Common hepatic duct hepatic duct unites with the cystic duct superior to the duodenum to form the Bile Duct. The Bile Duct descends posterior to the superior duodenum (1^st part of the duodenum). The bile duct joins the main pancreatic duct to form the hepatopancreatic ampulla which opens in the duodenal papilla. This passage is the narrowest part of the biliary passages and is the common site for impaction of gallstones.  Gallstones may produce biliary colic (pain in the epigastric region).

Ø  Endoscopic retrograde cholangiography is done by first passing a fiberoptic endoscope through the mouth, esophagus, and stomach. Then the duodenum is entered  and a canicula is inserted into the major  duodenal papilla and is advanced under fluoroscopic control into the duct of choice (bile duct or pancreatic duct) for injection of contrast medium.

v  Developmental variability of the pancreatic ducts p157

v  Variations in Hepatic and Cystic Arteries p158

v  Variations of cystic and hepatic ducts and gallbladder.

Portal hypertension, Cirrhosis: Portocarval system

1.       Esophageal veins Azygos veins (systemic) and the left gastric vein (portal)

a.       Esophgeal varices can be seen through endoscopy

2.       Inferior and Middle Rectal Veins drain into the IVC (Systemic) and Superior Rectal Vein continuing as the inferior mesenteric vein (Portal)

a.       Hemorrhoids result of the vessels are dilated

3.       Small epigastric veins (systemic) and Periumbilical Veins (Portal)

a.       Radiate varicose from “caput madusae”

4.       Systemic Retroperitoneal veins (Systemic) with twigs of Colic Veins (portal)

Left renal vein

v  Drains the left testis, left suprarenal gland and left kidney. Renal arteries are posterior to the renal veins.

Ureter

v  Ureter crosses the external iliac artery just beyond the common iliac bifurcation.

v  Testicular arteries cross anterior to the ureter and join the ductus deferens to deep inguinal ring.

Pyelogram: Identify the following structures

v  12^th Rib                         Major Calyx                        Minor Calyx                        Renal Pelvis

v  Ureter                          Gas in Intestine                                Sacrum                                 Ureter

v  Catheter in bladder

v  Note the renal papilla bulging into the minor calices, which empty into the major calyx that open into the renal pelvis drained by the ureter.

Renal Transplantation: is an established for chronic renal failure. Remove the kidney without damaging the suprarenal gland. The site of transplanting the kidney is in the iliac fossa of the greater fossa. The renal artery and vein are joined to the external iliac artery and vein and the ureter is sutured into the bladder.

Kidney Structure:

v  Superior and inferior pole. Vessels enter the renal sinus and the superior and inferior renal pole.

v  Adult polycystic disease is an important cause of chronic renal failure.

Anomalies of Kidney and ureter

v  Bifid pelvis

v  Duplicated or bifid ureters

Ø  Complete or incomplete. Unilateral or Bilateral

v  Retrocaval ureter. The ureter courses posterior then anterior to the inferior vena cava

v  Horseshoe kidney. The right and left kidneys are fused in the midline

v  Ectopic pelvic kidney. Pelvic Kidneys have no fatty capsule and can be unilateral or bilateral. Obstructed or injured during labour.