Anatomy
Duodenum means “two plus ten” and it is a retroperitoneal structure except the bulb portion. Duodenum has no mesentery. It is divided in to four sections: 1. Bulb; extends from pylor to the neck of gallbladder, 2. Descending portion: from neck of the gallbladder to genu, 3. Horizontal portion:from genu to abdominal aorta, 4. Ascending portion; extends from aorta to ligament of Treitz
CONGENITAL ABNORMALITIES
Malrotation
If there is abnormal rotation during the 6th week of embriological period, the duodenum does not acccross the aorta and remains in the right side of the abdomen. It may occur as an isolated anomaly or as a component of many abnormalities such as situs inversus, situs ambiguus, inferior vena cava anomalies, polysplenia, short pancreas etc. (2).
Type Ia is the most common type and findings are;
-superior mesenteric vein inversion (Figure 1)
-aplasia or hypoplasia of uncinate process of pancreas
-right sided small bowel
-left sided colon
-absence of the horizontal duodenum (Figure 2)
Type IIc is defined as reversed rotation of duodenum only (Figure 1). The duodenum passes anterior to the SMA.
Fig.: Figure 1. Duodenal malrotation. Barium study reveals anterior curving (arrow) of the duodenal sweep. Reversed localisation of superior mesenteric vein (arrow) on the left side of superior mesenteric artery is a sign of malrotation on CT slice.
Fig.: Figure 2. Duodenal malrotation. Note that horizontal duodenum (white arrow) is not seen between the superior mesenteric artery and abdominal aorta whereas it (black arrow) crosses anterior to pancreas. Large bowel (red arrow) is located on its original positon and can be seen on right upper quadrant.
Barium studies still play an important role in evaluation of malrotation especially in children. Suble signs of malrotation have been described as follows: a) unusual redundancy of the duodenum despite the location of the jejunum in the upper left quadrant, b) anormal-appearing sweep with duodeno-jejunal junction medial to left pedincle (3) (Figure 3).
Fig.: Figure 3. Duodenal malrotation in three different cases on barium studies. A) Clock wise rotation of the distal duodenum (duodenum inversum) and normal left sided jejunum. B) Malrotation with cork screw duodenum and jejunum. Note that duodenojejunal junction is medial to left pedincle C) In this symptomatic case, long and dilated duodenal sweep and right sided jejunum (small arrow) are sen on barium study. Partial rotation with obstructing Ladd bants (large arrow) were found at operation. B: bulb.
Duodenal Atresia
Duodenal atresia is present in more than 1 in 10,000 live births. Approximately 20-30% of infants with duodenal atresia have Downs syndrome.
Role of prenatal ultrasonography;
- Perform prenatal ultrasonography during any pregnancy with associated polyhydramnios. Examination of a fetus with duodenal atresia may reveal a dilated fluid-filled stomach and duodenum in addition to other (eg, cardiac) abnormalities. However, absence of these findings does not rule out duodenal obstruction.
- Erect and recumbent plain radiography of the abdomen When duodenal atresia is suspected, erect and recumbent plain radiography of the abdomen should be the first imaging study obtained .A characteristic finding of duodenal obstruction is the double bubble image of an air-filled stomach proximal to an air-filled first portion of the duodenum. Absence of gas in the remaining small and large bowel suggests atresia, whereas scattered amounts of gas distal to the obstruction suggests stenosis or malrotation/volvulus. (Figure 4).
- Upper gastrointestinal contrast evaluation; Upper gastrointestinal contrast evaluation in the infant with duodenal atresias is unnecessary unless correction is going to be delayed. An upper gastrointestinal contrast study may be useful if surgery is delayed to detect the presence of malrotation with midgut volvulus or to confirm the presence of an intrinsic duodenal obstruction (4).
Duodenal web (diaphragm)
It is congenital membrane like structure preferentially located in second part of duodenum. Varying degrees of obstruction may be seen. Barium study shows a thin band like radiolucency extending across the lumen as well as some degree of proximal dilatation (5) (Figure 4).
Fig.: Figure 4. Duodenal atresia and web. A) Typical double-buble appearence of gastric and duodenal airs (arrow) is well depicted on erect plain film in a case with duodenal atresia. B) Second portion of duodenum is partially obstructed by web (arrow) on barium study in another case. It was confirmed by endoscopy.
Diverticulum
It is usually located medial wall of the second and third portions of the duodenum. Barium studies, CT and MRI can reveal diverticulum as contrast material and air filled lumen (Figure 5). Infection, perforation, haemorrhage, pancreatitis or biliary obstruction can complicate diverticulum (2). Intraluminal diverticula are rare and show “windsock” deformity, with the contrast material filled diverticulum seen to project into the true lumen (1).
Fig.: Figure 5. Diverticulum. Extraluminal diverticulum (arrow) is typically shows a fluid-air level in medial wall of descending duodenum (D) beneath the pancreatic head on CT images. Double-contrasted barium study of the same case confirms the diverticula (arrow
Annular Pancreas
It is a congenital anomaly in which pancreatic tissue partially or totally encircles the second portion of the duodenum Imaging findings are related to duodenal obstruction, biliary obstruction, or both (5). Barium studies show concentric narrowing of second portion of duodenum whereas CT reveals pancreatic tissue encircling the duodenum (Figure 6,7,8,9).
Fig.: Figure 6. CT of complet annuler pancreas in a symptomatic case. A) A hypodens area (arrow) adjacent to pancreatic (P) head completely obstructs second portion of duodenum on arterial phase of dynamic CT scan
Fig.: Figure 7. Annuler pancreas. B) The hypodens area becomes isodens with the density of pancreatic (P) head on portal venous phase
Fig.: Figure 8. Annuler pancreas. C) Correlative barium study also reveals dilated duodenal bulb and typical concentric narrowing (arrows) of the second portion of duodenum resulting from annuler pancreas.
Fig.: Figure 9. Partial annuler pancreas in an asymptomatic case. Non contrasted (A, B) and contrast enhanced (C, D) CT scans reveal that a soft density lesion similar with pancreatic density is partially protruded to the medial wall of duodenum and only partially obstructed the duodenal lumen
Paraduodenal Hernias
Paraduodenal hernias are the most common type of internal abdominal hernias and are usually left sided (75%). The paraduodenal fossa (fossa of Landzert) is the only fossa to the left of the duodenum capable of developing hernia. Imaging findings of internal herniaitons have been described as (6,7);
· Saclike mass or cluster of dilated bowel loops and
· engorged, streched and displaced mesenteric vascular pedicle and
· dilated bowel loops having converging vessels
CT may demonstrate
· an encapsulated bowel loop that displaces the inferior mesenteric vein anteriorly, suggesting the the trapped loop is located behind the descending mesocolon (7). Herniation through mesenteric defects may be transient (Figure 10).
Fig.: Figure 10. Transient duodenal hernia. CT shows A) Herniated small bowel loops (arrows) in the left upper quadrant, B) The engorged mesenteric vessels (arrow) towards the entrance of the hernia sac. C) Regression of the hernia sac on follow-up CT and D) regression of the engorged mesenteric vessels on follow-up CT.
Lymphangiectasia
Lymphangectasia is the dilatation of abnormal lymphatic channels which have failed to establish normal communication with the rest of the lymphatic system (5). CT scans may show circumferential thickening of the small bowel wall with low attenuation (<30 H). (Figure 11).
Fig.: Figure 11. Duodenal lymphangiectasia. Mild mural thickening of second portion of duodenum is visualized on CT. Endoscopy revealed lymphangiectasia. Note also thickened folds of jejunum.
Superior Mesenteric Artery (SMA) Syndrome
Compression and obstruction of the third portion of the duodenum by the SMA as crosses over the duodenum. The angle between SMA and aorta can be come vey small under certain circumstances resulting in compression of duodenum with proximal dilatation at the site of the crossing (5) (Figure 13).
Fig.: Figure 13. Superior mesenteric artery (SMA) syndrome. Narrowed horizontal portion of duodenum (arrow) passing between suerior mesenteric artery (*) and abdominal aorta (*) is seen on CT scan. Note that proksimal duodnum (Duo) is dilated. with air-fluid level.
INFLAMMATORY PROCESSES
Many adjacent inflammatory process frequently affects the doudenum and these pathologies most commonly cause symmetric or asymmetric mural thickening and dilatation of lumen with air-fluid level called as “sentinel loop” (Figure 14).
Fig.: Figure 14. Duodenal sentinel loop. Markedly dilated duodenal lumen (*) with air-contrasted fluid level consistent with sentinel loop is demonstrated in three different cases with acute pancreatitis.
Acute Pancreatitis
It is the most common cause of duodenal mural involvement. Pancreatic exocrine enzymes may cause inflammation resulted in a smooth–mild wall thickening in a long segment of duodenum (Figure 15).
Fig.: Figure 15. Acute pancreatitis caused mural thickening (*) of duodenum in two different cases. Note that mural thickening is smooth and includes long segment of duodenum. Density of peripancreatic fat is also increased. P: pancreas.
Acute Cholecystitis
Inflammed gallbladder wall may also cause concentric mural thickening of duodenum mimicking tumoral lesions (Figure 16). In chronic cases, a gallstone may erode the duodenal wall and “gallstone ileus” can be encountered.
Fig.: Figure 16. Acute cholecystitis. CT slice shows thickened gallbladder wall and adjacent fluid density (white arrow). Duodenal wall (asterix) is also concentrically and smoothly thickened through the long segment (black arrow)
Duodenal Ulcer
It occurs commonly in the duodenal bulb and rarely can be detected on cross-sectional images. However, perforated duodenal ulcers can be diagnosed on CT scans. CT findings are:
· duodenal wall thickening,
· periduodenal fluid,
· retroperitoneal air,
· free intraperitoneal air (1) (Figure 17).
Fig.: Figure 17. Perforated duodenal ulcus. A) Free air is seen on the right subdiaphragmatic space (*) and right upper quadrant regions (arrow) on scanogram. B) Free air densities on perforated duodenal bulb (D) and adjacent intraperitoneal area (*) are visualized on CT scan. Perforation point (arrow) is also well depicted on CT scan. GB gallbladder
Crohn’s Disease
The prevalance of duodenal involvement is reported between 0.5% and 4% in barium studies and 5% to 60 in endoscopic studies. Ulcer or stricture formation are seen as the primary involvement whereas fistulous comminications usually occur in secondary involvement. CT may show
- non-specific thickening of the valvulae conniventes or
- tubular strictures (2) (Figure 18).
Fig.: Figure 18. Crohn’s disease. CT shows markedly dilated duodenal (D) sweep due to fibrotic tubular obstruction (arrow) at the level of Treitz ligament. Note that the walls of duodenum are not thickened. S; stomach.
Coeliac disease
It is characterized by malabsorbtion and flattening, broadening coalescence and sometimes complete loss of jejunal villi.
Barium enema findings are
- dilatation,
- segmentaiton and
- flocculation of barium,
- Delayed transit time.
- Thickening of mucosal folds (is an artifact of increased intestinal secretion. (8) (Figure 19).
- In late stages duodenal and jejunal folds become rarefied and can not be detected whereas ileal folds may be come thickened (“inverted bowel” pattern) (5,8).
Fig.: Figure 19. Coeliac disease. Mild mural thickening of duodenum (arrows) and coalescence of prominent valvulae connivantes (*) of mildly dilated jejunal segments resulted from Coeliac disease are detected on CT images.
Ménétrier’s Disease
It is a rare condition of unknown aetiology that is characterized by hyperthropy of the glands in the stomach mucosa leading to thickening of gastric folds, hypochlorhydria and hypoproteinaemia. On barium studies, grossly thickened lobulated folds in gastric body with relative sparing antrum is seen (5) . Also US, endoscopic US, CT and MR enteroclysis may reveal similar findings (Figure 20, 21,22).
Fig.: Figure 20. Ménétrier’s disease. CT and barium study. A 22 years old woman with epigastric pain and symptoms of protein loosing enteropathy. CT scan shows prominent gastric folds (long arrows) and mural thickening (small black arrows) of duodenum (*) . Barium study also demonstrates lobulated gastric conturs and thickened duodenal mucosal patern (arrows). D duodenal bulb. Patient underwent gastrectomy and pathology confirmed the imaging findings.
Fig.: Figure 21. Menetrier’s disease US and endoscopic US. A) Transabdominal US shows prominent gastric fols (arrows) and endoscopic US also confirms thickened gastric folds especially thickened submucosal layer (arrows)
Fig.: Figure 22. Menetrier’s disease MR_enteroclysis. MR enteroclysis shows prominent gastric folds (arrows).
ADJACENT INFECTIOUS PROCESS
Since duodenum is adjacent to many abdominal organs, several infectious processes may affect duodenum and may cause non-spesific wall thickening.
Intrabdominal abscesses
Abscess is localized collection of pus and may be caused by inflammation, infection, perforation or trauma of organs (5). The specific location of peritoneal abscess is determined by the site of the leak escape, peritoneal recesses, gravity, intraabdominal pressure changes.
Direct radiologic signs include
· Soft tissue mass
· Loss of normal tissue planes
· Displacement of intraabdominal organs
· Extraluminal gas
· Extravasation of contrast medium
Subhepatic abscess (Figure 23), Mesenteric Panniculitis (Figure 24), Pyelonephritic psoas abscess (Figure 25), Perforated Large Bowel (Figure 26) may cause infectious mural thickening of the duodenum.
Fig.: Figure 23. Subhepatic abscess (white arrows) is seen as a collection with air-fluid levels in subhepatic region. Lateral duodenal wall (asterix) adjacent to the abscess is asymmetrically thickened
Fig.: Figure 24. Mesenteric panniculitis. A cicumferential hyperdensity (arrows) in paraduodenal fatty tissue is seen on CT image. Stranding of mesenteric fat and minimal mural thickening of adjacent lateral wall of duodenum (D) is also noted.
Fig.: Figure 25. Pyelonephritic psoas abscess. Circumferential mild mural thickening and air-fluid level (arrows) in horizontal portion of duodenum is consistent with inflammatory changes and sentinel loop appearance secondary to left psoas abscess (*) and pyelonephritic changes (small arrow) on CT scan. P; psoas.
Fig.: Figure 26. Perforation of descending colon in a case with acute pancreatitis. Peripancreatic fluid (arrow) and free air densities (*) are seen on CT slice. Note that duodenal lumen is filled with fluid density (sentinel loop) and duodenal wall is mildy thickened. P; pancreas, D duodenum.
Perforated Gallbladder
CT findings are;
· Pericholecystic fluid collections
· Streaky infiltration in the omentum or mesentery
· Gallbladder defect (5).(Figure 27).
Fig.: Figure 27. Perforated gallbladder. Asymmetric mural thickening of lateral wall of duodenum (D) adjacent to inlammated gallbladder (straight black arrow) is depicted on CT scan. Concentrically thickened prepyloric antrum (curved black arrow) and increased density of adjacent fat tissue (*) deu to inflammation is also noted. GB gallbladder. Continious CT slice shows perforation point (arrow) of gallbladder (GB)
Gossipyboma (Textiloma)
It is a term used to indicate cotton based retained post operative foreign bodies in a body space. They can often be asymptomatic but can progress to abscess formation, fistula or obstruction. Radiographically detection of lap pads may be difficult, due to poor quality post operative films. On CT, hemostatic sponges have mixed or low attenuation and can have focal gas pockets. Infected gossipybomas may cause protein loosing enteropathy resulting in mural thickening of duodenum and jejunal segments (5)(Figure 28).
Fig.: Figure 28. Gossipyboma (textiloma). A. Mild mural thickening of horizontal duodenal segment (arrw) is seen on CT. B. Jejunal segments also show thickened folds (arrow). C. CT slice at the level of pelvis reveals a large encapsulated hypodens lesion (arrows) including flocculated air densities mimicking large bowel. Operation revaled a infected gossipyboma.
Hematologic Abnormalities
Henoch-Schönlein Purpura
It is a systemic small vessel vasculitis hypersensitivity disease. CT may show multifocal areas of bowel thickening, and mesenteric edema (Figure 29). Gastrointestinal involvement occurs 70% of cases. Increased capillary fragility is responsible for the extravasation of the seroangineous fluid into intestinal wall which causes oedema of the mucosa and submucosa. US and CT may demonstrate mural thickening of the affected bowel. (5) (Figure 29).
Fig.: Figure 29. Henöch-Schönlein Vasculitis (HSV). CT scan demonstrates prominent duodenal plica (arrow) and prominent jejunal valvulae connivantes. Endoscopic biopsy revealed histological findings consistent with HSV.
NEOPLASMS
Primary benign and malignant tumors can be seen in duodenum.
Gastrointestinal Stromal Tumor (GIST)
The most encountered benign tumor of GI tract is benign gastrointestinal stromal tumor (GIST). Clinically, gastrointestinal bleeding and abdominal pain can be seen. CT findings include; heterogenous solid mass with moderate enhancement, and an annular narrowing of the lumen with abrupt concentric or irregular edges (Figure 30).
Fig.: Figure 30. Gastrointestinal stromal tumor (GIST). A solid and heterogeniously enhanced tumor (arrows) with smooth conturs located on duodenum partially obliterates the lumen on CT scan. Concentrically narrowed duodenal lumen (arrows) with “apple core” appearance is seen on barium study.
Adenocarcinoma
It is very uncommon tumor (0.3-0.4% of all GI tract tumors), however adenocarcinoma is the most common form of malignant duodenum tumors.
Barium study signs include: a lobular, filling defect in polypoid lesions or annuler stenosis with overhanging edges in constructing and ulcerated lesions. US may show psewudokidney appearance in large tumors, whereas CT reveals the tumoral wall thickening and enlarged lymph nodes (Figure 31).
Fig.: Figure 31. Duodenal adenocarcinoma. A) US demonstrates pseudokidney appearance of duodenal mural thickening. B) CT scan confirms concentric duodenal mural thickening and C) barium study also reveals irregular mucosal filling defects and mild dilation of duodenal genu.
Lymphoma
Only for 12% of all malignant duodenal neoplasia are duodenal lymphomas. Radiologic appearance on barium study are
Aneurysmal dilatation with or without fistula formation, multipl nodular defects, segmental irregular narrowing of lumen.(5).
Additionally, tumoral wall thickening and enlarged lymph nodes are shown by CT, US and MRI (Figure 32). Radiological differential diagnosis include tuberculosis, inflammatory bowel disease and carcinoma.
Fig.: Figure 32. Duodenal lymphoma. Non-contrast (A) and contrasted (B) CT scans show narrowed lumen and concentrically thichkened horizontal portion of duodenum (arrows). C) US image demonstrates pseudokidney appearence (arrow) of duodenal wall thickening. D) Barium study also reveals narrowed and irregular mucosa patern (arrows) of horizontal duodenum.
Tumors of Papilla Vateri (Carcinoma of ampulla of Vater)
Most ampullary carcinomas are typical adenocarcinomas. It is the cause of 8% of cases of malignant biliary obstruction.
These tumors appear on barium studies as filling defects on medial border of the 2nd portion of the duodenum and may exhibit an irregular or smooth surface. ERCP is diagnostic tool. However percutan transhepatic cholangiography,can be used as an alternative. US is useful in confirming the obstructive of the jaundice. CT will provide the same information as US but may be additionally able to visualize the protruding tumor into the duodenum. MRCP provides no specific findings other than to demonstrate the dilated bile ducts (5). (Figure 33).
Fig.: Figure 33. Papilla Vateri tumor. A) CT slice shows a hypodens mass (arrow) protruding in to the duodenal lumen at the level of papila Vateri.. B) T2W source MRI of MRCP also demonstrates papilla Vateri tumor (arrow). C) Dilated distal common bile duct (C) is obstructed at the papilla level (arrow) on MRCP. D; duodenum. D) Operation revealed papilla Vateri tumor (arrow) corresponding with imaging findings.
SECONDARY NEOPLASTIC INVOLVEMENT OF DUODENUM
Secondary neoplastic infiltration of duodenum can be arised from local extension of adjacent malignant tumors of gallbladder, pancreas, stomach, colon, over and kidneys (Figures 34,35,36).
Fig.: Figure 35. Pancreatic carcinoma. CT slices of four different cases with pancreatic carcinoma showing duodenal involvement. Infiltration patterns (arrows) may be seen as a local asymmetric (upper images), or circumferential (lower images) mural thickening mimicking primary duodenal adenocarcinoma.
Fig.: Figure 36. Gastric carcinoma. Duodenal bulb (arrow) is infiltrated with the gastric mass extending from prepyloric antrum through the pyloric canal.
PARADUODENAL SOLID MASSES
Pancreatic head lipoma
Pancreatic head lipoma is incidentally diagnosed and can mimic fatty paraduodenal tumors on imaging however, it can easily be diagnosed with CT (Figure 37).
Fig.: Figure 37. Pancreatic head lipoma. Fat density mass medial to duodenum (D) is located in pancreatic head and is consistent with lipoma.
Dermoid cyst
Dermoid cysts are fatty masses and depending on the location of the lesion, occasionally, they contain horny masses and hairs, dental, cartilagelike, and bonelike structures. Paraduodenal location of dermoid is very rare. Imaging findings are typical and shows characteristics of fatty tissue. On US it is echogenic and, on CT it is hypodens compatible with fat tissue. Also, MRG features are of diagnostic value (Figure 38).
Fig.: Figure 38. Dermoid cyst. US image shows a solid hyperechoic mass and CT image confirms that the solid paraduodenal mass is of fat density and corresponded with dermoid cyst.
Paraganglioma
Gangliocytic paragangliomas are unusual neoplasms that may be identified anywhere within the gastrointestinal tract, but predominate in the periampullary region. These tumors are considered benign, yet occasionally metastasize to regional lymph nodes, as well as to distant organs Their radiological features are commonly those of submucosal tumors and similar to those of a leiomyoma (5) (Figure 39).
Fig.: Figure 39. Paraganglioma. Dynamic and perfusion CT: A soft tissue mass (asterix) located on duodenal region is detected on A) non-contrast, B) arterial and C) portal venous pahses of contrasted dynamic CT. Additional perfusion CT also demonstrates a well perfused mass (*) coded dominantly as red colour.
Plasmocytoma (primary extramedullary)
Solitary extramedullary plasmacytoma arising in the duodenum is very rare and it may simulate carcinoma of the head of the pancreas. Primary extramedullary plasmacytoma (EMP) is a solitary tumor that arises outside the bone marrow in patients without clinical evidence of coexisting multiple myeloma. The tumor generally occurs in the submucosal tissue of the upper airway or oral cavity. 10% of all EMP occur in the gastrointestinal tract. Only 8 cases of EMP in the duodenum have been reported in literature. (Figure 40).
Fig.: Figure 40. Plasmocytoma, Perfusion CT. A hypoechoic solid mass (*) is detected on US examination. CT also demonstrates a hypodens solid mass (*) on paraduodenal region. Red colored mass on perfusion CT images indicates that mass (*) is well perfused. Patient underwent oparation and diagnesed as soliter plasmocytoma.
Lymphnodes
Metastatic and infectious lymph node involvement of many diseases especially occur in paraduodenal region. Seminoma (Figure 41), and non-Hodgkin lymphoma (Figure 42) can clinically be manifested only by paraduodenal lymph node enlargement. Metastatic lymph nodes of mesothelioma (Figure 43) can also be located on paraduodenal area. Rarely encountered infectious processes such as pancreatic tuberculosis may be manifested by paraduodenal lymph node enlargement (Figure 44).
Fig.: Figure 41. Paraduodenal lymphadenopathy of seminoma. A lobulated hypodens mass (arrow) located on paraduodenal region is visualized on CT scan. A testiculer mass is also found on Us examination and fine needle aspiration biopsy revealed metastatisis of seminoma.
Fig.: Figure 42. Non-Hodgkin lymphoma. Non-contrasted CT scans. Duodenal sweep is not seen on its original anatomic location and bulb (arrow) is displaced to anterior due to multipl paraduodenal and aorta caval lymphadenomegalies (*). S stomach. Note also periheapatic fluid.
Fig.: Figure 43. Metastatic lymph node of mesothelioma. CT demonstrates a soft tissue density nass (*) compressing duodenal lumen beneath the pancreatic head. Thoracic CT revealed mesothelioma and fine needle aspiration biopsy confirmed metastatic nodal involvement.
Fig.: Figure 44. Pancreatic tuberculosis. A hypodens area (*) between the pancreatic head and duodenum (D) is seen on non-contrast CT scan. Hypodens lesion (*) is more easily visualized on contrast enhanced CT slice. US image also reveals a hypoechoic solid (*) mass. Patient was operated and tuberculosis was diagnosed with pathological examination.
Mesenteric Liposarcoma
It is very rare and can grow very slowly. Liposarcomas, due to presence of more solid and myxoid elements besides fat, may have variable appearances on CT and MRI.(5). They can be seen as lipomatous or soft tissue masses similar to muscle or close to water (Figure 45).
Fig.: Figure 45. Liposarcoma. Soft tissue density lesion (arrows) between the duodenum (D) and pancreatic head is demonstrated on both CT and US (*) images.
PARADUODENAL CYSTIC MASSES
Many cystic lesions originated from adjacent organs can be encountered and may mimic primary duodenal cystic lesions and differential diagnosis may be difficult. Choledochal cyst, choledochocele, pancreatic pseudocysts, duplicated gallbladder, intestinal lymphangiectatic cysts, cysts of policystic disease, and hydatic disease (cyst) can be seen in this region.
Choledochal Cyst
It is characterized by a globular or fusiform dilatation of the common bile duct just below the site of entry of cystic duct. Indicence is 0.2-0.5% per million population. It is anatomically classified to V types. Fluid containing cystic masses in continuity with extrahepatic bile ducts mostly situated within the panvreatic head is the typical radiological finding (5). (Figure 46). However it may be difficult to differentiate choledochal cyst from duplicated gall with many imaging modalities (Figure 47).
Fig.: Figure 46 . Choledochal cyst. CT scan shows a thin walled cyst (C) located between pancreatic head and second part of duodenum (D). GB; gallbladder
Fig.: Figure 47. Choledochal cyst. Two cystic lesions medial to gallbladder (arrow) are seen in gallbladder fossa on CT scan. D; duodenum. Axial MRI shows that cystic (*) lesion is connected with the adjacent to gallbladder (GB) wheras MRCP reveals that cystic lesion (*) is seperated from adjacent gallbladder and mimicks duplicated gallbladder. However ERCP revealed cholodochal cyst.
Choledochocele
It is a protrusion of a dilated intramural common bile duct into the duodenum There are two anatomical types that can not always be differentiated by radiological imaging. In the first the common bile duct terminates into the choledochocele which drain into the duodenum via an aperture in its wall. The second type occurs when common bile duct enters normally ino the papilla (5). Although large choledochoceles may be diagnosed easily small ones may be difficult to differentiate from other hypodens papilla Vatreri lesions. (Figure 48).
Fig.: Figure 48. Choledochocele. A cystic density (*) protruding into the duodenal lumen at the level of papilla Vateri is visualised on CT image. A choledochocele.was found by ERCP.
Gallbladder Duplication
Although estimated to occur once in every 4000 autopsies, the incidence of reported symptomatic cases is probably very low. Ultrasound, MRCP, CT scan, scintigraphy and oral cholecystography have their limitations and are not 100% sensitive in identifying biliary ductal anomalies. The ultrasonographic appearance may be confused with choledochal cysts, gallbladder diverticulum, pericholecystic fluid collections, focal adenomyomatosis, Phrygian cap, extrinsic fibroud bands across the gallbladder and a folded gallbladder (9).(Figure 49).
Fig.: Figure 49. Duplicated Gallbladder. US shows acustic shadows arised from cholelithiasis and adjacent cystic mass (*). CT also confirms cholelithiasis and an adjacent cystic mass located lateral to duodenum on gallbladder fossa. Differentiation of duplicated gallbladder from choledochocele with CT and US alone is difficult and ERCP may be helpful for the diagnosis.
Hydatic Disease
It is a parasitic disease caused by echinococcus granulosus or less frequently by E. multilocularis. Many forms can be seen I- pure cystic forms II-Cyst including inner daughter cyst developing from inner germinal layer and III- Cyst with inner ondulating membranes which can be seen as a solid mass The presence of curvilenear calcification in the wall of the cyst is also a typical finding of hydatid disease. It is frequently located on liver and lungs however, it can be located anywhere in the body (Figure 50). When liver hydtid cysts are perforated, inner membranes may be detected as ondulating densities and may cause obstruction of bile ducts (Figure 51).
Fig.: Figure 50. Hydatic cyst. A smooth walled pure cystic lesion located on paraduodenal region is seen on CT. Note that the presence of inner multiple daughter cysts which are typical for hydatic disease.
Fig.: Figure 51. Perforated hydatic cyst. Intra and extrahepatic bile ducts are dilated and enlarged common bile duct adjacent to duodenum is seen as a cystic mass on CT. Note the presence of inner curving densities (arrows) in dilated bile duct lumen consistent with inner membranes of perforated hydatic cyst. CT also shows a cystic mass with inner ondulating membranes typical for hydatic disease. GB gallbladder.
Pancreatic Pseudocyst
Mostly they are related to acute fluid collections seen at the onset of pancreatitis. It appears as a rounded well encapsulated fluid collections of varying attenuation on CT and they are most frequently located close to pancreas (Figure 52).
Fig.: Figure 52. Pancreatic pseuodcyst. Pancreatic pseudocyst (*) compressing duodenal ans is seen as a pancreatic cystic mass on non contrast and contrasted CT images. There is also another huge pseudocyst posterior to stomach.
Paraduodenal abscess
Intraabdominal abscesses are localised and encapsulated fluid collections and may exhibit varied radiological appearences according to their stages. Differentiaiton from aother cystic mass is usually made by the presence of air densities or levels, presence of relatively thck walls usually demonstrating contrast enhancement and, adjacent soft tissue changes such as streaky infiltration of fatty tissue (Figure 53).
Fig.: Figure 53. The paraduodenal abscess (black arrows) is seen as large cystic paraduodenal mass including air (*) densities. Pericholecystic fluid is also seen. D:duodenum, GB Gallbladder, P pancreas.
Polycystic Disease
Radiological findings include enlarged kidneys with multiple non-commnunicating cysts. Calcification of cyst wall, hemorrhage and tones can be seen. Enlarged renal cyst may casue compression of adjacent structures as well as duodenum (Figure 54).
Fig.: Figure 54. Policystic renal disease (dominant). Non-contrast CT images show that genu of duodenal swep (arrow) is compressed by adjacent cysts of right kidey while distal part shows prominent duoıdenal mucosal folds (arrows).
Intestinal lymphangiectasia
Intestinal lymphangiectasia is a disease characterized by hypoproteinemia and lymphocytopenia, resulting from blocked intestinal lymphatics and loss of lymph fluid into the gastrointestinal (GI) tract. The dilated lymphatic channels conglomerate and form a unilocular cystic mass. Uncomplicated fluid is seen with in the mass or locules, which are separated by thin septa (Figures 55,56,57). Imaging studies are:
- Double-contrast radiographs of the small bowel may show thickened folds due to intestinal edema from hypoproteinemia, nodular protrusions, and absence of mucosal ulcerations (Figure 57).
- Ultrasound and CT scans are also useful in identifying dilated intestinal loops, regular and diffuse thickening of the intestinal walls, plical hypertrophy, and mesenteric edema (Figures 55,56).
Fig.: Figure 55. Intestinal lymphangiectasia. A 65 years old female presenting with symptoms of protein loosing enteropathy A) US demontrates two thin walled pure cystic lesion (C) adjacent to pancreatic head (P). CT also shows cystic lesion encircling pancreatic head and medial to duodenum (D) but cystic septa is not depicted on CT images.
Fig.: Figure 56. Intestinal lymphangiectasia. T1W and T2W MRI images show a septated cystic mass (C) (arrows) adjacent to pancreatic (P)head. GB gallbladder.
Fig.: Figure 57. Intestinal lymphangiectasia. Enteroclysis demonstrates increased fold distance of jejunal segment. Patient underwent operation and pathologic specimen revealed intestinal lymphangiectaisa. Underlying disease was not found in follow up period for 4 years.
Duodenal hematoma
The most common cause of duodenal hematoma is blunt trauma. It is assumed that compression of the best fixed parts the duodenum, particularly of second and third portion, btween the ventral abdominal wall and vertebral column is responsible for the lesion. CT depicts a high attenuation mass in direct contact with the duodenal lumen which is narrowed to a variable degree (Figure 58 ).
Fig.: Figure 58. Duodenal hematoma. CT scan demonstrates a hypodens mass and peripheric hyperdens oral contrast material in dilated duodenal lumen in a traumatised patient.
Foreign Bodies
Most ingested foreign bodies will pass through the pyloris. Once beyond the pyloric canal most objects, even sharply edged foreign bodies, such as pieces of glass or nails, will pass without harm until the terminal ileum. Most ingested bodies are more or less radiopaque and will be recognised readily on a plain radiograph.(ensik) However their anatomical location can easily be revealed by CT (Figure 59).
Fig.: Figure 59. Ingested foreign body (nail) on duodenum. Scanogram shows a lineer metallic opacity (arrow) on right upper quadrant in a child who ingested metallic nail. CT slice reveals the metallic artifact of the nail (arrow) in the doudenum. The nail was removed from duodenum by endoscopy.
POST-OPERATIVE EVALUATION
Whipple operation
The operation involves excising the head of the pancreas as well as the adjacent duodenum and bile duct in cases with cancer of pancreatic head. In the "Standard Whipple Procedure," part of the stomach is also removed while, in the "Pylorus-Preserving Whipple Procedure," the entire stomach is retained. After completing the resection, it is reconnected the intestine to the bile duct, pancreas, and stomach. (Figure 60).
Fig.: Figure 60. Whipple operation was performed in a case with pancreatic carcinoma. Since pancreatic head and duodenum is surgically removed, jejunum (arrows) should not be mistaken for duodenum on CT scans.
Chelodocho-duodenostomy
Side to side choledochoduodenostomy is an established procedure for effecting intrenal drainage of common bile duct. However reflux from duodenum into the biliary tract can occur in these cases and can be demonstrated by barium studies (Figure 61).
Fig.: Figure 61. Choledochoduodenostomy. Barium studies show reflux of contrast material from duodenum to the biliary tract in two diffrent cases with choledochoduodenostomy.
Duodenal stents and catheters
Stents are usually used in cases with malignant outlet obstructions for palliation or pending surgey in debilitated patients. They positioned under flouroscopic or endoscopic guidance. Occlusion may occur due to ingrowth or overgrowth of tumor. The positons of these materials can easiliy be visualized by CT scans (Figure 62,63).
Fig.: Figure 62. Catheters and stents of common bile duct. A) A choledocho-duodenal catheter (arrow) is performed in a case who had obstructed common bile duct due to benign stricture. B). Obstructed common bile duct was treated with metallic stent (arrow) in a case with cholangiocarcinoma.
Fig.: Figure 63. Oesophago-duodenal stent. Metallic stent extending from esophagus to descending duodenum is seen on scanogram (A), CT slice (B), and C) barium study of a case operated for gastric carcinoma,
Afferent loop syndrome
It is a complication following subtotal gastrectomy with Billroth II procedure and characterized by obstruction of the afferent loop with variable severity. The afferent loop can become dilated by partial obstruction leading to lumen dilatation. Peroral contrast studies may show non opacification of afferent loop. CT and US can be useful by visualizing a dilated afferent loop as multiple spherical ovoidor thin-walled fluid-containing structures (on CT) or as an anechoich tubular structure (on US) (Figure 64,65).
Fig.: Figure 64. Afferent loop syndrome. In a case with distal gastrectomy and gastrojejunostomy, US and CT slice located upper position shows markedly dilated horizontal duodenum. Other CT scan (lower position) reveals that the obstruction is resulted from recurrent gastric carcinoma (white arrow). *Superior mesenteric artery,
Fig.: Figure 65. Afferent loop syndrome. Barium study of the same case confirms that duodenum is not filled by contrast material and duodenogastric anastomosis (green arrows) is markedly obstructed whereas passage of barium through the gastro-jejunal junction (white arrow) is normal.