CT Scan

Case 31

Presentation

A 58-year-old man with hypertension presented with complaints of a 3-day his- tory of chills, intermittent fever with mid abdominal pain, and a 24-hour his- tory of vomiting bright red blood. He did not have a history of peptic ulcer dis- ease or alcoholism. Upon examination he is found to be anxious; his pulse rate is 108 bpm, and his blood pressure is 110/68 mm Hg. His abdomen is soft with mild epigastric tenderness. Family history is significant for abdominal aortic aneurysm (AAA). No lesion was seen in the first or second part of the duodenum on upper endoscopy. A computed tomography (CT) scan is ordered.

CT Scan

Figure 31.1

CT Scan Report

CT scan demonstrates a 4.5-cm AAA in close approximation to the duodenum with air in the aortic wall.

Differential Diagnosis

---

      The differential diagnosis includes an upper gastrointestinal (GI) bleed from a gastric or duodenal ulcer, sepsis from unidentified source with GI bleeding from gastritis, and primary aorto-enteric fistula (PAEF).

Case Continued

---

      The patient begins to re-bleed, as evident from the nasogastric tube output. Esophagogastroduodenoscopy (EGD) is repeated. The bleeding appears to be coming from the fourth portion of the duodenum.

Diagnosis

---

      Based on the history of abdominal pain, upper GI bleeding in the absence of peptic ulcer, and the CT findings of air in the aortic wall in close proximity to the duodenum, the diagnosis of primary aorto-enteric fistula is made.

Based on the history of abdominal pain, upper GI bleeding in the absence of peptic ulcer, and the CT findings of air in the aortic wall in close proximity to the duodenum, the diagnosis of primary aorto-enteric fistula is made.

---

      Blood transfusion is initiated and the patient is taken to the operating room. EGD by an experienced endoscopist is the test of choice and should visualize the third and fourth portion of the duodenum. This will also rule out other more common causes of an upper GI bleed. CT scan with intravenous contrast will show pathol- ogy either in the aorta (aneurysm) or in the vicinity. Arteriogram does not add more information, and can potentially precipitate hemorrhage. Treatment is sur- gical to control bleeding and establish vascular continuity.

Surgical Approach

      Proximal control of the supraceliac aorta is obtained prior to mobilization of the duodenum. The PAEF is identified (Fig. 31-2). A communication of the aorta with the GI tract makes it a contaminated field. However, in an unstable pa-

Figure 31.2 Duodenal erosion of the PAEF.

tient, there is no time to obtain autogenous graft or perform an extra-anatomic bypass. An in-situ rifampin-soaked graft is placed with omentum between the graft and the bowel. Cultures are obtained from the aortic wall.

Discussion

PAEF is a ruptured or leaking aorta emptying into the GI tract. The communica- tion is a result of degenerative process, which is most commonly aneurysm, lo- cal infection, foreign body, or even radiation. PAEFs are extremely difficult to di- agnose preoperatively. In a report by Sweeny and Gadazc of 118 cases of PAEF, 97 patients died before a definitive diagnosis could be made. In another series, only one third of the patients were treated with surgical repair, with periopera- tive mortality of 55%. Crucial to diagnosis is timely endoscopy with visualiza- tion to the fourth portion of the duodenum. CT scan finding of loss of a plane between the aorta and the duodenum with air in the aortic wall or the retroperi- toneal area is suggestive of an aorto-enteric fistula. The triad of symptoms of ab- dominal pain, an upper GI bleed, and abdominal aneurysm together occur in about one third of the patients. A common scenario is that a general surgeon will discover it at the time of celiotomy in acute circumstances. If the patient has been stable, local debridement can be attempted with extra-anatomic by- pass or autogenous reconstruction. However, in an unstable patient or inexperi- enced hands, in situ replacement with rifampin-soaked graft is quite acceptable. In a review for a 15-year period, no reports of postoperative graft infections have been reported in 8 patients. If there is extensive contamination, an interval (8- to –10-day) replacement of the aorta can be performed, if possible, with the su- perficial femoral vein used as a neoaorta or an extra-anatomic bypass. By this time, final culture results are also available. An interval of a week also allows for surgery prior to formation of dense adhesions. Interval replacement is recom- mended if gram-negative fungal infections are present, or if there is communi- cation with the large bowel. The idea of endovascular exclusion is attractive in theory, but may depend on graft availability, advance knowledge of the diagno- sis, and the logistics of surgeon/operating room training. An endovascular ap- proach may serve as a bridge to more definitive treatment.

Case Continued

---

After undergoing in situ tube graft, a nasogastric tube is placed to the duode- num. Diet is started after 5 days. Cultures do not grow any organism, but initial gram stain demonstrated a few white blood cells. The patient is discharged on a 6-week course of oral Bactrim.

Suggested Readings

---