Retroperitoneum Part A Holdorf Outline Anatomy Curs of the diaphragm Peritoneum Retroperitoneum Abdominal Aorta Inferior Vena Cava AzygosHemiazygos Veins Ascending Lumbar veins Retroperitoneal fibrosis ID: 909094
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Slide1
SON 2112Ultrasound of the Abdomen Part II
Retroperitoneum Part A
Holdorf
Slide2Outline
Anatomy
Curs of the diaphragm
Peritoneum
Retroperitoneum
Abdominal Aorta
Inferior Vena Cava
Azygos/Hemiazygos Veins
Ascending Lumbar veins
Retroperitoneal fibrosis
Slide3Crus of the diaphragm
The diaphragmatic crura begin as musculo-tendinous fibers arising form the lumbar vertebra and travel along the anterior lumbar vertebrae to insert into the diaphragm. The right cru is broader and longer than the left crus. The right is anteriolateral to the IVC and posteriomedial to the right adrenal and right lobe of the liver. The left cur is lateral to the aorta.
Slide4Crus of the diaphragm
The crus of the diaphragm is located:
Anterior to the aorta
Superior to the celiac axis
Posterior to the inferior vena cava
The crus of the diaphragm can be imaged in transverse and longitudinal planes. The curs is located medial and posterior to tall structures except the aorta.
Slide5Slide6Technique
Scanning the retroperitoneum involves scanning the Kidneys, aorta, IVC, pancreas, and pelvic areas. This is usually a general overview scan and not organ specific, unless pathology is discovered in an organ. A 3.5 MHz sector, vector or curvilinear transducer is used although a lower frequency transducer may be needed on larger patients or to image deeper structures. Linear array transducers can be used to evaluate large masses and superficial areas. Longitudinal and transverse scans are performed with the patient in supine and decubitus positions. Scanning will include using the transducer to press bowel gas out of the way to see underlying structures. To reduce bowel gas, patients should be NPO for at least 6-8 hours.
Slide7Laboratory Values
Hematocrit levels and red blood cell (RBC) counts will drop with hemorrhage and hematomas.
White blood cell counts (WBC) will increase with leukemia, malignancies, infection and abscesses.
WBC counts will decrease with Hodgkin’s and non-Hodgkin’s lymphoma.
Epinephrine and nonepinephrine will increase with pheochromcytomoas.
Cortisol levels can increase in Cushing’s syndrome and decrease in Addison’s disease.
Masses, Adenopathy
The lymphatic system consists of small vessels and functioning nodes whose function is to return excess water, electrolytes and colloids to the bloodstream. Normal lymph nodes are too small to see with ultrasound. Enlargement of lymph nodes (Adenopathy) are visible and require careful scanning along the aorta and IVC. The normal distance between the SMA and aorta may be increased, mesenteric and visceral vessels may be displaced, and the aorta may be lifted off the spine when lymph nodes are enlarged. Adenopathy may be regional or extensive.
Slide9Enlargement may be due to infection or malignant disease. Malignant Adenopathy is commonly caused by metastases or by lymphoma. The most common primary is adenocarcinoma of the GI tract. Lymphatic drainage of the gonads are to the high pre-aortic nodes; therefore ovarian and testicular malignancies may be the cause of upper abdominal lymph Adenopathy.
Sonographically, enlarged lymph nodes are seen in the abdomen as oblong masses of uniform, low level echoes. Superficial lymph nodes are oval or round masses. Enlarged lymph nodes from an infectious process usually have echogenic centers, resembling small kidneys. Arterial and venous blood flow to and from the lymph nodes can be visualized, especially in superficial lymph nodes. Malignant lymph nodes are usually homogenous in appearance.
Slide10Primary neoplasms are extremely rare and include liposarcoma, leiomyosarcomas. Benign masses include lipomas and fibromas. Some of these tumors can grow quite large before being detected.
Slide11Retroperitoneal Fibrosis is usually idiopathic in origin but may be the result of infections, enteritis (inflammation of the small intestine), or seen in patients on medications for migraines. It can also be associated with leaking abdominal aortic aneurysms. Sonographically, it appears as hypoechoic tissue anterior, posterior or lateral to the aorta or IVC and may look similar to Adenopathy, although it usually does not displace the aorta form the spine and has smoother margins. Since this process extends laterally to the ureters, it may cause Hydronephrosis.
Hematomas
Bleeding may occur into the retroperitoneum, called a hemoperitoneum, as a result of trauma, surgery, leaking or ruptured aortic aneurysms or malignancy. Free fluid or organized collections may be seen on the ultrasound exam. Patients with a leaking aneurysm may present with back pain, flank pain and decreasing hematocrit. Sonographically, complex fluid collections may be observed in the flanks. Suspected leaking aneurysms are a medical emergency and may be a sign of impending aortic rupture.
Slide13PERITONEUM
The peritoneum is the serous membrane that forms the lining of the abdominal cavity and covers most of the abdominal organs. It consists of two layers:
Parietal peritoneum (outer layer)-lines the abdominal wall
Visceral peritoneum (inner layer)-covers the abdominal organs.
The space between the two layers is the peritoneal cavity.
The peritoneal cavity contains two separate compartments:
Slide14Peritoneum
Slide15Psoas Muscles
Slide16Quadratus Lumborum Muscles
Slide17Large lymph nodes- causing displacement of the abdominal organs
Slide18Malignant lymph nodes w/Liver metasteses
Slide19Malignant lymph nodes
Slide20HematomasAbdominal Aorta rupture
Slide21The diaphragm PE or Ascites?
Slide22Lesser Sac-space that is situated between the liver, pancreas and stomach. The entrance
to the lesser sac is the epiploic foramen (area just above the pancreas).
Greater sac- this is the rest of the peritoneal cavity. When you are imaging ascites with Floating bowel, this is the greater sac area.
Slide23Slide24Inter-peritoneal structures
Stomach
Jejunum
1
st
part of the duodenum
Appendix
Spleen
Cecum
Transverse colon
Rectum (part of)
Liver
Uterus
Fallopian tubes/Ovaries
Slide25The stomach to the rectum
Slide26Slide27Kidneys and adrenal glands lie within the peri-renal space and are separated from the pararenal spaces by the anterior and posterior renal fascia (Gerota’s Fascia).
Slide28The following structures are located in the retroperitoneum:
Kidneys
Adrenal Glands
Ascending and Descending Colon
2
nd
, 3
rd
, and 4
th
parts of the duodenum
Pancreas
Aorta and IVC
Ureters
Renal vessels
Superior mesenteric vessels
Gonadal vessels
Lymphatics
Prostate
Slide29Abdominal Aorta
The aorta enters the abdominal cavity in a posterior location. It becomes progressively more anterior as it travels caudally.
The IVC, in contrast, maintains a more horizontal course throughout the retroperitoneum.
Slide30Slide31Celiac Axis
The celiac axis is the first major branch as the aorta descends through the diaphragm. It is only 2-3 cm long and is located superior to the pancreas. It branches into three arteries
Common hepatic artery
Left Gastric Artery
Splenic artery (the longest of the three)
The celiac axis terminates with the bifurcation of the common hepatic artery and the splenic artery (Sea Gull or dove sign)
The left gastric artery is usually not visible, however occasionally can be seen extending cranially from the celiac axis.
As the common hepatic artery courses toward the liver, it bifurcates into the proper hepatic artery and the gastro-duodenal artery (GDA).
Slide32Celiac Axis/trunk
Slide33Superior Mesenteric Artery
The superior mesenteric artery branches off the aorta about 1 cm inferior to the celiac axis. It parallels the aorta and is seen posterior/inferior to the body of the pancreas.
SMA Doppler waveforms:
Fasting state- high resistance
Postprandial – low resistance-increased velocity
NOTE: The celiac should always be low resistant
Slide34SMA
Slide35SMA
Slide36Renal Arteries
The renal arteries arise from the lateral walls of the aorta just below the origin of the SMA.
The right renal artery passes posterior to the IVC to enter the renal hilum. The left renal artery is shorter as the aorta lies to the left of the midline.
Slide37Slide38Renal Arteries
Slide39Gonadal Arteries
The right and left Gonadal arteries arise from the distal aorta and are rarely imaged.
Slide40Cartoon of the Gonadal Arteries
Slide41Inferior Mesenteric Artery
The IMA arises from the anterior aspect of the distal aorta and is rarely imaged.
Slide42IMA
Slide43Inferior Vena Cava
The IVC lies to the right of the aorta and posterior to the pancreatic head and liver.
The IVC dilates with cardiac failure and fluid overload.
The most common tumor in the IVC is renal-cell carcinoma.
Thrombus of the IVC is most commonly caused by Budd-Chari Syndrome.
The IVC is easily displaced. The following are reasons for IVC displacement.
Liver mass (Medial and lower)
Right renal artery aneurysm (anterior)
Lymphadenopathy (has tendency to accumulate posteriorly – displace anteriorly
Tortuous aorta (right)
Right renal /adrenal mass (anterior and medially)
Retroperitoneal Tumor
Slide44IVC with Hepatic veins
Slide45IVC filtersIVC filters are used to prevent the ascent of lower extremity vein thrombus. The most common filter is the Greenfield Filter.
Proper location for an IVC filter is inferior to the renal veins.
Slide46Slide47Hepatic Veins There are three hepatic veins: right, middle and left, which drain into the IVC.
Slide48Hepatic Veins
Slide49Renal veins
The right renal vein is short, draining directly into the IVC. The left renal vein is longer, passing between the SMA and aorta as it travels from the left kidney to the IVC.
The NUTCRACKER SYNDOME is the engorgement of the left renal vein due to its compression by the SMA and aorta.
Slide50Renal Veins
Slide51Gonadal Veins The right Gonadal vein drains into the IVC. The left Gonadal vein drains into the left renal vein.
Slide52Gonadal veins
Slide53Azygos/Hemiazygos Veins
The Azygos and Hemiazygos veins provide an alternate pathway for venous return in the case of caval obstruction. They connect the proximal abdominal IVC to the superior vena cava and unless dilated, are normally not visualized.
The Azygos vein is located on the right. The Hemiazygos vein is located on the left.
Slide54Slide55Ascending lumbar veins
The ascending lumbar veins are branches of the common iliac veins.
They are the abdominal counterparts of the Azygos-hemiazygos system. These veins travel in a path lateral to the spine and posterior to the psoas muscle.
Slide56Ascending lumbar veins
Slide57Retroperitoneal Fibrosis
Retroperitoneal fibrosis, also known as Ormond’s disease, or inflammatory aneurysm, is a dense fibrous tissue proliferation confined to the para-vertebral region.
The fibrosis rarely extends superior to the level of Lkk-2 and may extend inferiorly to the dome of the bladder. Generally, it is centered at the aortic bifurcation.
Sonographically, the appearance is usually a hypoechoic midline mass.
It is associated with bilateral ureteral obstruction as it envelopes structures rather than displacing them.
A large percentage of cases are idiopathic.
Other causes include:
malignancies
various drugs and chemicals
Crohn’s disease
Sclerosing cholangitis
Radiation therapy
Chemotherapy
Aortic aneurysms
Slide58Retro Fibrosis
Slide59