Duodenal perforation may occur in the setting of peptic

Duodenal perforation may occur in the setting of peptic ulcer, trauma, procedural
complications (ERCP, endoscopy) or secondary to malignancy. Iatrogenic
perforation as a complication of ERCP is usually suspected at the time of
endoscopic examination (Figure 6) (19, 20). In these cases, the combination of
history and CT findings can help guide the diagnosis, with a characteristic
pattern of gas in the retroperitoneum (Figure 7). Duodenal perforation may also
occur in the setting of peptic ulcer disease (Figure 1) and duodenal
diverticulitis (rare) (Figure 3). CT findings of duodenal perforation include discontinuity
in the duodenal wall with associated wall edema and periduodenal stranding (Figures
6), air bubbles in close contact with the duodenal rent, retroperitoneal air
adjacent to the duodenum and extending into the mesentery and peritoneum,
extravasation of oral contrast into retroperitoneum (if administered), fluid in
the retroperitoneum (more common) between duodenum and pancreatic head (10,17).
Location of free air can help diagnose site of duodenal perforation for example
free air crossing the midline and extending along falciform ligament or
ligamentum teres could be due to duodenal bulb perforation, free air in lesser
sac could be due to 1st or 2nd part duodenum perforation
and air in right anterior pararenal space or retropancreatic region could be
due to 3rd part duodenum perforation (17).

 

Vascular pathology

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Duodenal hemorrhage can occur in the setting of ulcer disease, tumor,
trauma and gastroduodenal artery pseudoaneurysm. The diagnosis is made with CT
angiogram acquisition done with rapid rate of intravenous contrast injection, thin
collimation and multiphase protocol, which enables depiction of IV contrast
extravasation into the bowel lumen in the setting of active gastrointestinal
bleeding (Figure 8). Multiplanar reconstructions assist in locating the site of
bleeding especially the double oblique plane in early arterial phase acquisition
might best depict the extravasation blush (21). Risk factors for gastroduodenal
artery (GDA) pseudoaneurysm include pancreatitis and pancreaticoduodenectomy
with pancreaticojejunal leak, ulcers, or iatrogenic causes (surgery, endoscopy
with biopsy) (Figure 9). In cases of ongoing hemorrhage, visualization of
bleeding is dependent on the rate and duration of bleeding as well as CT
technique (21). In patients with gastrointestinal hemorrhage, IV contrast
should be administered and positive oral contrast must be avoided as it obscures
visualization of active bleeding. Negative or neutral contrast may dilute the
hemorrhage and reduce conspicuity (22).
 An uncommon cause of duodenal hemorrhage
is rupture of an untreated abdominal aortic aneurysm into the duodenal lumen or
an aneurysm sac that continued to enlarge after endovascular stent placement(Figure
10). Arteriovenous malformation such as duodenal angiodysplasia or hereditary hemorrhagic
telangiectasia can be a cause of episodes of occult melena but rarely can cause
acute bleeding with presentation to the emergency department (22).

Duodenal hematoma can result from blunt abdominal trauma
classically seen in seat belt injury. However, it may also be seen with
coagulation disorders or rarely iatrogenic reasons (17). Management is usually
conservative, but precise diagnosis is important to exclude other causes such
as malignancy and the distinction is facilitated by use of a coronal MPR for
characterization (Figure 11).

 

Duodenal Obstruction

Acute duodenal obstruction can result from primary duodenal or other
periampullary tumors. Clinical symptoms include nausea, vomiting and the inability
to tolerated oral intake. Approximately 20% of small bowel neoplasms arise in
the duodenum (23). Duodenal malignancies can be classified as benign or
malignant. The most common symptomatic benign neoplasm of the duodenum is a
benign gastrointestinal stromal tumor (GIST) (24). GIST appear as heterogeneous
masses, with varying degrees of enhancement based on the size, and can be
exophytic and may cause narrowing of the lumen. Duodenal lipomas are benign lesions
with smooth margins and negative Hounsfield unit measurement (-20 to -100HU).
Adenomas of the duodenum include tubular type, villous adenoma (malignant
potential), and Brunner gland adenoma (24,25).

The most common primary malignancy of the duodenum is
adenocarcinoma (Figure 12), with 50%–70% of small bowel adenocarcinomas
occurring either in the duodenum or proximal jejunum (1,26). Lymphomatous involvement of the duodenum can occur with
both primary duodenal lymphoma and involvement from systemic disease. The
duodenum can also be obstructed by local extension of other malignancies, for
example pancreatic adenocarcinoma or gallbladder cancer (1,27). Other rare
causes of obstruction include congenital peritoneal bands, annular pancreas, strictures
due to severe duodenal ulcers and Bouveret syndrome (obstruction by gall stones
following a cholecystoduodenal fistula) (1).

 

CONCLUSION

Acute, critical duodenal pathology may be overlooked if the radiologist
is not knowledgeable about the range of potential duodenal pathologies as the
cause of a patient’s acute clinical presentation and hence should include the
duodenum in their search pattern for all gastrointestinal presentations. Proper
CT technique includes the use of intravenous contrast, thin sectionacquisition
and multiplanar reconstructions at a work station in the emergency department
setting.