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Root of the Small-Bowel Mesentery: Correlative Anatomy and CT Features of Pathologic Conditions¹

¹ From the Department of Radiology, Oita Medical University, Hasama-machi, Oita 879-5593, Japan. Presented as an education exhibit at the 2000 RSNA scientific assembly. Received February 7, 2001; revision requested April 6 and received July 9; accepted July 23. Address correspondence to Y.O. (e-mail: hosya@oita-med.ac.jp).

View larger version (95K): [in a new window]   Figure 1.   Drawing of the anatomy near the root of the SBM (RSBM). The root of the SBM (area within dashed circle) is contiguous superiorly to the hepatoduodenal ligament (HDL) along the SMV, anteriorly to the transverse mesocolon (TM), and posterolaterally to the ascending mesocolon and descending mesocolon (DM). The gastrocolic trunk (GT) is a landmark of the junction between the transverse mesocolon and the root of the SBM. The inferior mesenteric vein (IMV) is a landmark of the descending mesocolon and joins the SMV or splenic vein on the left side of the root of the SBM. IPDA = inferior pancreaticoduodenal artery, IPDV = inferior pancreaticoduodenal vein, PV = portal vein, SRL = splenorenal ligament.

View larger version (146K): [in a new window]   Figure 2.   Massive ascites in a patient with ovarian cancer. Coronal magnetic resonance (MR) image of the peritoneal folds clearly shows the relationships of the ligaments and mesenteries. Note that the root of the SBM (*) is contiguous to the hepatoduodenal ligament (HDL) and the right side of the transverse mesocolon (TM). SRL = splenorenal ligament.

View larger version (148K): [in a new window]   Figure 3a.   Contrast material-enhanced CT scans of the peritoneal folds and ligaments. (a) The root of the SBM is contiguous to the hepatoduodenal ligament (arrows) around the portal vein (PV) and SMV. CHA = common hepatic artery. (b, c) The root of the SBM is contiguous to the right side of the transverse mesocolon (TM) in the vicinity of the gastrocolic trunk (GT). The right side of the root is contiguous to the ascending mesocolon (arrowheads), which contains the right colic vein (RCV). The left side is contiguous to the descending mesocolon (arrows), which contains the inferior mesenteric vein (IMV). A = SMA, D = horizontal portion of the duodenum, J = jejunum, V = SMV. (d) The posterior attachment of the SBM (arrows) fixes the SBM to the posterior abdominal wall. IMV = inferior mesenteric vein.

View larger version (151K): [in a new window]   Figure 3b.   Contrast material-enhanced CT scans of the peritoneal folds and ligaments. (a) The root of the SBM is contiguous to the hepatoduodenal ligament (arrows) around the portal vein (PV) and SMV. CHA = common hepatic artery. (b, c) The root of the SBM is contiguous to the right side of the transverse mesocolon (TM) in the vicinity of the gastrocolic trunk (GT). The right side of the root is contiguous to the ascending mesocolon (arrowheads), which contains the right colic vein (RCV). The left side is contiguous to the descending mesocolon (arrows), which contains the inferior mesenteric vein (IMV). A = SMA, D = horizontal portion of the duodenum, J = jejunum, V = SMV. (d) The posterior attachment of the SBM (arrows) fixes the SBM to the posterior abdominal wall. IMV = inferior mesenteric vein.

View larger version (142K): [in a new window]   Figure 3c.   Contrast material-enhanced CT scans of the peritoneal folds and ligaments. (a) The root of the SBM is contiguous to the hepatoduodenal ligament (arrows) around the portal vein (PV) and SMV. CHA = common hepatic artery. (b, c) The root of the SBM is contiguous to the right side of the transverse mesocolon (TM) in the vicinity of the gastrocolic trunk (GT). The right side of the root is contiguous to the ascending mesocolon (arrowheads), which contains the right colic vein (RCV). The left side is contiguous to the descending mesocolon (arrows), which contains the inferior mesenteric vein (IMV). A = SMA, D = horizontal portion of the duodenum, J = jejunum, V = SMV. (d) The posterior attachment of the SBM (arrows) fixes the SBM to the posterior abdominal wall. IMV = inferior mesenteric vein.

View larger version (138K): [in a new window]   Figure 3d.   Contrast material-enhanced CT scans of the peritoneal folds and ligaments. (a) The root of the SBM is contiguous to the hepatoduodenal ligament (arrows) around the portal vein (PV) and SMV. CHA = common hepatic artery. (b, c) The root of the SBM is contiguous to the right side of the transverse mesocolon (TM) in the vicinity of the gastrocolic trunk (GT). The right side of the root is contiguous to the ascending mesocolon (arrowheads), which contains the right colic vein (RCV). The left side is contiguous to the descending mesocolon (arrows), which contains the inferior mesenteric vein (IMV). A = SMA, D = horizontal portion of the duodenum, J = jejunum, V = SMV. (d) The posterior attachment of the SBM (arrows) fixes the SBM to the posterior abdominal wall. IMV = inferior mesenteric vein.

View larger version (96K): [in a new window]   Figure 4.   Drawing of the neural plexus near the pancreatic head. The pancreatic capital plexus is attached to the medial margin of the pancreatic head near the SMA and celiac trunk. The second branch of the plexus (II) surrounds the inferior pancreaticoduodenal artery and vein.

View larger version (141K): [in a new window]   Figure 5.   Direct invasion by cancer of the pancreatic body. Postcontrast CT scan shows a pancreatic tumor (T) directly invading the SBM root (arrows).

View larger version (117K): [in a new window]   Figure 6.   Direct invasion by jejunal leiomyosarcoma. Postcontrast CT scan shows a jejunal leiomyosarcoma (L) invading the root of the SBM (arrows) along the SBM itself.

View larger version (147K): [in a new window]   Figure 7a.   Neural plexus invasion by cancer of the lower bile duct. Postcontrast CT scans show a tumor (* in a) of the lower bile duct. Neural plexus invasion is seen as extension of the mass through the root of the SBM and along the inferior pancreaticoduodenal artery and first jejunal artery (arrows in b) to the right aspect of the SMA (arrowheads in a). D = duodenum, P = pancreatic head, V = SMV.

View larger version (148K): [in a new window]   Figure 7b.   Neural plexus invasion by cancer of the lower bile duct. Postcontrast CT scans show a tumor (* in a) of the lower bile duct. Neural plexus invasion is seen as extension of the mass through the root of the SBM and along the inferior pancreaticoduodenal artery and first jejunal artery (arrows in b) to the right aspect of the SMA (arrowheads in a). D = duodenum, P = pancreatic head, V = SMV.

View larger version (127K): [in a new window]   Figure 8.   Cancer of the pancreatic body extending through the ligaments. Postcontrast CT scan shows a tumor (T) of the pancreatic body, located in the SBM, extending to the splenorenal ligament (arrows) through the transverse mesocolon.

View larger version (127K): [in a new window]   Figure 9.   Drawing of the pathways for pancreatic fluid to the SBM. Pancreatic fluid can spread to remote sites along the ligaments and mesentery. For the pathway via the transverse mesocolon (TM), the lateral limits are the hepatic flexure on the right side and the splenic flexure on the left side. For passage of pancreatic fluid via the SBM, the inferior limit is the ileocecal region. PCL = phrenocolic ligament, SRL = splenorenal ligament.

View larger version (52K): [in a new window]   Figure 10a.   Acute pancreatitis. (a) Drawing of the pathway for pancreatic fluid shows the fluid extending through the root of the SBM anteriorly into the transverse mesocolon (TM) and in a left lateral direction into the anterior pararenal space behind the descending mesocolon (DM). Note the relationship between the inferior mesenteric vein (IMV) and the pathway for pancreatic fluid from the root of the SBM to the left anterior pararenal space behind the descending mesocolon. DC = descending colon, P = pancreatic head. (b, c) Postcontrast CT scans (b obtained superior to c) show pancreatic fluid extending to the SBM and transverse mesocolon (arrowheads). The fluid also extends laterally to the left anterior pararenal space behind the descending mesocolon (*) and to the right anterior pararenal space behind the ascending mesocolon (**). The inferior mesenteric vein, which is the landmark for the descending mesocolon, is clearly visualized (arrow).

View larger version (126K): [in a new window]   Figure 10b.   Acute pancreatitis. (a) Drawing of the pathway for pancreatic fluid shows the fluid extending through the root of the SBM anteriorly into the transverse mesocolon (TM) and in a left lateral direction into the anterior pararenal space behind the descending mesocolon (DM). Note the relationship between the inferior mesenteric vein (IMV) and the pathway for pancreatic fluid from the root of the SBM to the left anterior pararenal space behind the descending mesocolon. DC = descending colon, P = pancreatic head. (b, c) Postcontrast CT scans (b obtained superior to c) show pancreatic fluid extending to the SBM and transverse mesocolon (arrowheads). The fluid also extends laterally to the left anterior pararenal space behind the descending mesocolon (*) and to the right anterior pararenal space behind the ascending mesocolon (**). The inferior mesenteric vein, which is the landmark for the descending mesocolon, is clearly visualized (arrow).

View larger version (124K): [in a new window]   Figure 10c.   Acute pancreatitis. (a) Drawing of the pathway for pancreatic fluid shows the fluid extending through the root of the SBM anteriorly into the transverse mesocolon (TM) and in a left lateral direction into the anterior pararenal space behind the descending mesocolon (DM). Note the relationship between the inferior mesenteric vein (IMV) and the pathway for pancreatic fluid from the root of the SBM to the left anterior pararenal space behind the descending mesocolon. DC = descending colon, P = pancreatic head. (b, c) Postcontrast CT scans (b obtained superior to c) show pancreatic fluid extending to the SBM and transverse mesocolon (arrowheads). The fluid also extends laterally to the left anterior pararenal space behind the descending mesocolon (*) and to the right anterior pararenal space behind the ascending mesocolon (**). The inferior mesenteric vein, which is the landmark for the descending mesocolon, is clearly visualized (arrow).

View larger version (137K): [in a new window]   Figure 11a.   Acute pancreatitis with pancreatic fluid extending through the portal venous system. (a, b) Postcontrast CT scans show a pseudocyst (* in b) in the uncinate process of the pancreas. A low-attenuation area within the portal venous system is also identified (arrows in a). (c) Endoscopic retrograde cholangiopancreatogram shows contrast medium filling the biliary tract and entering the portal venous system through the pseudocyst (*). C = common bile duct, PV = portal vein, SPV = splenic vein. (d) MR cholangiopancreatogram shows high signal intensity of the portal venous system in contiguity with the pseudocyst (*). C = common bile duct, MPD = main pancreatic duct, PV = portal vein, SPV = splenic vein.

View larger version (130K): [in a new window]   Figure 11b.   Acute pancreatitis with pancreatic fluid extending through the portal venous system. (a, b) Postcontrast CT scans show a pseudocyst (* in b) in the uncinate process of the pancreas. A low-attenuation area within the portal venous system is also identified (arrows in a). (c) Endoscopic retrograde cholangiopancreatogram shows contrast medium filling the biliary tract and entering the portal venous system through the pseudocyst (*). C = common bile duct, PV = portal vein, SPV = splenic vein. (d) MR cholangiopancreatogram shows high signal intensity of the portal venous system in contiguity with the pseudocyst (*). C = common bile duct, MPD = main pancreatic duct, PV = portal vein, SPV = splenic vein.

View larger version (133K): [in a new window]   Figure 11c.   Acute pancreatitis with pancreatic fluid extending through the portal venous system. (a, b) Postcontrast CT scans show a pseudocyst (* in b) in the uncinate process of the pancreas. A low-attenuation area within the portal venous system is also identified (arrows in a). (c) Endoscopic retrograde cholangiopancreatogram shows contrast medium filling the biliary tract and entering the portal venous system through the pseudocyst (*). C = common bile duct, PV = portal vein, SPV = splenic vein. (d) MR cholangiopancreatogram shows high signal intensity of the portal venous system in contiguity with the pseudocyst (*). C = common bile duct, MPD = main pancreatic duct, PV = portal vein, SPV = splenic vein.

View larger version (85K): [in a new window]   Figure 11d.   Acute pancreatitis with pancreatic fluid extending through the portal venous system. (a, b) Postcontrast CT scans show a pseudocyst (* in b) in the uncinate process of the pancreas. A low-attenuation area within the portal venous system is also identified (arrows in a). (c) Endoscopic retrograde cholangiopancreatogram shows contrast medium filling the biliary tract and entering the portal venous system through the pseudocyst (*). C = common bile duct, PV = portal vein, SPV = splenic vein. (d) MR cholangiopancreatogram shows high signal intensity of the portal venous system in contiguity with the pseudocyst (*). C = common bile duct, MPD = main pancreatic duct, PV = portal vein, SPV = splenic vein.

View larger version (147K): [in a new window]   Figure 12a.   Perforation of a jejunal diverticulum. Nonenhanced CT scans show air perforations within the root of the SBM and the retroperitoneal fat (straight arrows in a). Intraluminal gas is seen in the small intestine (curved arrow in b).

View larger version (130K): [in a new window]   Figure 12b.   Perforation of a jejunal diverticulum. Nonenhanced CT scans show air perforations within the root of the SBM and the retroperitoneal fat (straight arrows in a). Intraluminal gas is seen in the small intestine (curved arrow in b).

View larger version (109K): [in a new window]   Figure 13.   Rotation anomaly (nonrotation). Postcontrast CT scan shows dilated bowel loops due to sigmoid colon cancer. The whole colon is located on the left side of the abdominal cavity. Note that the SMA (straight arrow) is to the right of the SMV. The inferior mesenteric vein (curved arrow) is in the normal position within the right margin of the descending mesocolon.

View larger version (110K): [in a new window]   Figure 14.   Midgut volvulus. Precontrast CT scan shows a typical whirl sign (arrowheads) around the SMA (the root of the SBM). Note the high-attenuation structure (arrow) in the whirled loops, which represents a thrombus within the SMA.

View larger version (84K): [in a new window]   Figure 15.   Drawing of a left paraduodenal hernia. The jejunum enters the hernia sac behind the descending mesocolon through a peritoneal defect situated near the inferior mesenteric vein. (Adapted and reprinted, with permission, from reference 12.)

View larger version (146K): [in a new window]   Figure 16a.   Left paraduodenal hernia. Axial (a) and coronal (b) postcontrast CT scans show an encapsulated bowel loop (black arrows) in the left paraduodenal fossa. The inferior mesenteric vein (arrowheads) is displaced anterolaterally by the bowel loop and joins the SMV through the root of the SBM. Note the mesenteric fat and the jejunal vein (white arrows) within the bowel loop.

View larger version (173K): [in a new window]   Figure 16b.   Left paraduodenal hernia. Axial (a) and coronal (b) postcontrast CT scans show an encapsulated bowel loop (black arrows) in the left paraduodenal fossa. The inferior mesenteric vein (arrowheads) is displaced anterolaterally by the bowel loop and joins the SMV through the root of the SBM. Note the mesenteric fat and the jejunal vein (white arrows) within the bowel loop.

View larger version (93K): [in a new window]   Figure 17.   Drawing of a right paraduodenal hernia. The jejunum enters the mesentericoparietal fossa of Waldeyer (yellow arrow). The right colic vein (RCV), a landmark of the ascending mesocolon, runs within the ascending mesocolon and joins the gastrocolic trunk (GT) through the transverse mesocolon. (Adapted and reprinted, with permission, from reference 12.)

View larger version (123K): [in a new window]   Figure 18a.   Right paraduodenal hernia. (a) Postcontrast CT scan shows an encapsulated bowel loop (arrows) in the Waldeyer fossa. The right colic vein (arrowheads) is displaced anteriorly by the bowel loop. (b) Surgical photograph obtained after withdrawal of the herniated bowel loops shows the hernial hiatus (Waldeyer fossa) (*). Note the congestion of the SBM. PJ = proximal jejunum withdrawn from the sac, T = Treitz ligament.

View larger version (132K): [in a new window]   Figure 18b.   Right paraduodenal hernia. (a) Postcontrast CT scan shows an encapsulated bowel loop (arrows) in the Waldeyer fossa. The right colic vein (arrowheads) is displaced anteriorly by the bowel loop. (b) Surgical photograph obtained after withdrawal of the herniated bowel loops shows the hernial hiatus (Waldeyer fossa) (*). Note the congestion of the SBM. PJ = proximal jejunum withdrawn from the sac, T = Treitz ligament.

View larger version (111K): [in a new window]   Figure 19.   SMA thrombosis. Postcontrast CT scan shows a filling defect in the proximal SMA (arrow).

View larger version (142K): [in a new window]   Figure 20a.   Acute SMV thrombosis. (a) Postcontrast CT scan shows a filling defect in the SMV (arrow). (b) Postcontrast CT scan shows a dilated small-bowel loop (SB) with a thickened wall, an appearance suggestive of congestive change. The increased attenuation of the SBM represents mesenteric congestion or edema (arrows).

View larger version (146K): [in a new window]   Figure 20b.   Acute SMV thrombosis. (a) Postcontrast CT scan shows a filling defect in the SMV (arrow). (b) Postcontrast CT scan shows a dilated small-bowel loop (SB) with a thickened wall, an appearance suggestive of congestive change. The increased attenuation of the SBM represents mesenteric congestion or edema (arrows).

View larger version (151K): [in a new window]   Figure 21.   SMA dissection. Postcontrast CT scan shows enlarged diameter of the SMA (arrows) with narrowing of the lumen. Increased attenuation in the root of the SBM is also seen (arrowheads).

View larger version (123K): [in a new window]   Figure 22.   Gas gangrene involving the small intestine. CT scan shows air attenuation in the SMV (arrows). The presence of Clostridium perfringens in the bowel wall was proved after resection of the jejunum.

View larger version (130K): [in a new window]   Figure 23a.   Mesenteric tear. (a) Precontrast CT scan shows a convex, high-attenuation mass (arrows) within the SBM, which represents a mesenteric hematoma. The irregular areas of increased attenuation (arrowheads) in the root of the SBM represent a mesenteric tear with small areas of hemorrhage. (b) Surgical photograph shows the mesenteric tear (arrows), which runs from the root of the SBM to the mesenteric border.

View larger version (132K): [in a new window]   Figure 23b.   Mesenteric tear. (a) Precontrast CT scan shows a convex, high-attenuation mass (arrows) within the SBM, which represents a mesenteric hematoma. The irregular areas of increased attenuation (arrowheads) in the root of the SBM represent a mesenteric tear with small areas of hemorrhage. (b) Surgical photograph shows the mesenteric tear (arrows), which runs from the root of the SBM to the mesenteric border.

View larger version (170K): [in a new window]   Figure 24.   Retroperitoneal fibrosis. Postcontrast CT scan shows a mass of soft-tissue attenuation (arrows) encircling the SMA in the root of the SBM. Biopsy at laparotomy revealed diffuse fibrosis of the pancreas and peripancreatic mesentery. Note the left hydronephrosis (H) caused by ureteral involvement. Ao = aorta.

View larger version (160K): [in a new window]   Figure 25.   Mesenteric lymphoma. Postcontrast CT scan shows a mass of soft-tissue attenuation (arrows) in the root of the SBM. The patency of the vessels within the mass is preserved.

View larger version (142K): [in a new window]   Figure 26.   Retroperitoneal teratoma located at the root of the SBM. Postcontrast CT scan shows a multiloculated mass (arrows) in the root of the SBM. The medial part of the mass (arrowhead) extends between the SMV and SMA.