Pneumobilia

Pneumobilia is the presence of gas in the biliary system. Causes include a biliary-enteric anastomosis, an incompetent sphincter of Oddi and spontaneous biliary-enteric fistula(due to gallstones etc)

Pathogenesis

In a normal healthy individual with a normally functioning sphincter of Oddi there should be no air within the biliary tree. Pneumobilia is commonly seen after biliary instrumentation but can be seen due to other causes such as incompetent sphincter of Oddi, biliary enteric surgical anastomosis, spontaneous biliary enteric fistula (cholecystoduodenal ~70%), infection (emphysematous cholecystitis), bronchopleuralbiliary fistula (rare), and congenital anomalies.

Anatomically common bile duct is located in proximity to the duodenum, crossing the first and second part of the duodenum posteriorly and further coursing down ending at the ampulla of Vater, where it is separated from the duodenum by pancreatic tissue. Nissen in his description of duodenal and peptic ulcer in 1945 claimed that this lateral separation isolates the common bile duct from complications of duodenal ulcer disease thus making choledochoduodenal an uncommon clinical entity.

It is essential to distinguish between air in the biliary tree from air in the portal venous system in making a diagnosis of pneumobilia.^[1]

Ulcerogenous choledochoduodenal fistula have been occasionally reported in the literature in the past and there have been very limited reports of such cases in recent years presumably due to better diagnostic and early therapeutic management of peptic ulcer disease.

Biliary-enteric fistula was first described by Bartholin in 1654, but it was only in 1840 that Long established its etiological association with duodenal ulcer. Hunt and Herbst in 1915 first reported the radiographic diagnosis of spontaneous internal biliary fistula: that is, cholecystoduodenal fistula complicating cholelithiasis. Cholelithiasis is a common cause of these fistulas accounting for up to 90% of cases while ulcer disease accounts for only about 5 percent of biliary-enteric communications.^[2] While cholelithiasis has been associated with cholecystoduodenal fistulas, peptic ulcer accounts for up to 80% of choledochoduodenal fistulas.

Other rare causes that have been reported include duodenal diverticulum, paraduodenal abscess, operative trauma, and carcinoma of the duodenum, stomach and bile duct.^[3][4]

Diagnosis

Intravenous cholangiography, endoscopic retrograde cannulation of the common bile duct and endoscopy can be used to visualize such a fistulous communication but there are no reports in literature describing the use of these techniques. Also barium studies can be used to demonstrate such a fistulous communication but the appearances should be distinguished from reflux of barium through the ampulla of Vater. In case of reflux the common bile duct fills only in its distal portion, whereas there is usually filling of the intrahepatic ducts in choledochoduodenal fistula. Another radiological finding that can be seen in such biliary enteric fistulas is pneumobilia which is the presence of air in the biliary tree.

Pneumobilia in the non operated patient, is almost pathognomonic of some form of internal biliary fistula.^[5] Unfortunately, this finding is inconsistent: it is manifested in only 14 to 58 percent of patients with choledochoduodenal fistula and although helpful when present, its absence should not preclude the diagnosis.

Differential Diagnosis

• Emphysematous cholangitis
• Tumors
• Ischemic colitis
• Pancreatitis

Management

Treatment of choledochoduodenal fistula secondary to duodenal ulcer stands divided between prophylactic surgery and conservative medical therapy. Experience from our case favors the latter but it also depends on the case presentation. There have been reports of worsening of biliary disease with non surgical management of choledochoduodenal fistula but in the absence of primary biliary disease, a choledochoduodenal fistula created by perforating duodenal ulcer presents a minimal risk of cholangitis or future biliary stricture, although the potential must at least be acknowledged. Indeed, Waggoner, LeMone and others report closure of a choledochoduodenal fistula with medical management. For such reasons Jordan and Stirrett [^[6]], and later Isaacson et al. [^[7]], were the first to actively suggest intensive medical management, especially in asymptomatic or poor risk patients. Evidence towards intensive medical management has grown over the past decades. A case series by Constant and Turcotte demonstrated successful medical management of four cases for up to a period of 11 years. recent consensus acknowledges treatment of the ulcer disease itself as the major goal and suggests surgical intervention in high risk or asymptomatic patients only for the usual indications in peptic ulcer disease, that is, hemorrhage, obstruction or intractability.

Epidemiology

Typically, patients with choledochoduodenal fistulas are usually in the fifth or sixth decade of life and have a long history of symptomatic dyspepsia. While women comprise approximately 70 percent of all cases of internal biliary fistula secondary to gall- bladder disease,^[8] men outnumber women by 3 to 1 or greater in biliary communications arising from penetrating duodenal ulcer. In 80%, the cause of choledochoduodenal fistula is usually penetrating duodenal ulcer disease in patients with a long ulcer history.^[9]

References

• Sherman SC, Tran H (February 2006). "Pneumobilia: benign or life-threatening". The Journal of emergency medicine 30 (2): 147–53. doi:10.1016/j.jemermed.2005.05.016. PMID 16567248.