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  • Sphincter of Oddi function and dysfunction: SO MANOMETRY

The development of techniques to measure pressure across the SO has enhanced our understanding of the normal physiology of the human SO and has also defined, with accu­racy and reproducibility, the presence of manometric disor­ders of the sphincter. The miniaturized manometry catheters that are used for pressure measurement have three lumens and are made of either polyethylene or teflon. They have an outer diameter of 1.7 mm. Three side holes are made at the recording tip of the catheter at 2 mm intervals, start­ing at 10 mm from its distal tip. Thus, the three lumens rec­ord across a length of 5 mm from within the SO. The catheter is connected to a pneumohydraulic capillary perfu- sion system with pressure force transducers in series. The catheter is perfused with deionized, bubble-free water at a flow rate of 0.13 mL/min to 0.25 mL/min, and the whole sys­tem is capable of accurately recording pressure changes of up to 300 mmHg/s. Mild sedation is usually achieved with intra­venous benzodiazepine (diazepam or midazolam) or propofol. These medications have been shown not to be associated with alterations in SO manometirc recordings. Be­fore and during the manometric recording, drugs that alter sphincter motility, such as atropine and opiate analgesics, are avoided.

When the duodenoscope is in an appropriate position in relation to the papilla, the manometry catheter is inserted through the biopsy channel. The catheter is then passed into either the bile duct or pancreatic duct to record the duct pressure. It is then withdrawn so that all three recording ports are positioned within the sphincter segment (Figure 2). The response to an intravenous bolus dose of CCK-octapeptide 20 ng/kg is then assessed. Catheter position, either in the pan­creatic duct or bile duct, may be assessed by injecting a small volume of contrast medium (less than 1 mL) through the most distal port while briefly screening by fluoroscopy. Ideally, the catheter should record from the sphincter region of clinical interest (ie, biliary for biliary type pain, pancreatic for pan­creatic pain) because discordant pressure recordings between the biliary and pancreatic portions of the sphincter have been reported. The overall risk of developing pan­creatitis is 8% and is higher for patients with suspected pancre­atic sphincter dysfunction than for suspected biliary sphincter dysfunction. Sacrificing one of the three recording chan­nels to act as an aspiration port has been shown to reduce the incidence of pancreatitis in patients undergoing pancreatic sphincter manometry for suspected pancreatic sphincter dys­function. High perfusion flow rates have also been shown to increase the risk of pancreatitis.

Normal and abnormal manometric recordings have been identified in patients with clinically suspected SO dysfunc­tion (Table 1). As discussed above, manometrically proven SO dysfunction has been subdivided into two major groups, ir­respective of whether the symptoms are primarily biliary or pancreatic (Table 2). This manometric division of SO stenosis and SO dyskinesia has allowed targeting of specific therapy for patients in whom diagnosis of SO dysfunction is made.
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