A novel ultrasound-based algorithm for the detection of pancreatic stents placed for prophylaxis of post-ERCP pancreatitis: a prospective trial

Abstract

Purpose

Before removal of retained pancreatic stents placed during endoscopic retrograde cholangiopancreatography to avoid post-ERCP pancreatitis, imaging is recommended. The aim of the present study was to evaluate a new ultrasound-based algorithm.

Materials and Methods

Patients who received a pancreatic stent for PEP prophylaxis were included. Straight 5Fr (0.035inch) 6cm stents with an external flap that were visualized by ultrasound were removed endoscopically with no further imaging. If the ultrasound result reported the stent to be dislodged or was inconclusive, X-ray imaging was performed. The endpoints were positive and negative predictive value, specificity, sensitivity, and contingency coefficient between ultrasound and X-ray and/or endoscopy.

Results

88 patients were enrolled in the present study. X-ray was performed in 23 (26%) patients. Accordingly, the ultrasound algorithm saved an X-ray examination in 65 cases, leading to a reduction of 74%. Stents were retained in 67 patients (76%) and visualized correctly by ultrasound in 54 patients with a sensitivity of 81%. The positive predictive value was 83%. The specificity was 48%, because ultrasound described 10/21 dislodged stents correctly. The negative predictive value was 43%, since 10/23 stents were correctly classified by ultrasound as dislodged. In 11 patients (13%), esophagogastroduodenoscopy was performed even though the pancreatic stent was already dislodged.

Conclusion

A novel ultrasound-based algorithm reduced the need for X-ray imaging by three quarters. To avoid unnecessary endoscopic examinations, the algorithm should be implemented with a learning phase and procedures should be performed by experienced examiners. An important limitation might be stent length since shorter stents might be more difficult to visualize by ultrasound.

Zusammenfassung

Hintergrund

Aktuell wird vor der Entfernung von prophylaktisch gelegten Pankreas-Stents nach einer endoskopischen retrograden Cholangiopankreatikografie eine Bildgebung empfohlen. Ziel der vorliegenden Studie war es, einen neuen ultraschallbasierten Algorithmus zu evaluieren.

Material und Methoden

Eingeschlossen wurden Patienten nach prophylatischer Pankreas-Stent-Anlage. Gerade 5 Fr-Stents (0,035 inches) mit 6cm Länge vom externen Flansch, die mittels Ultraschall sichtbar waren, wurden endoskopisch ohne weitere Bildgebung entfernt. Wenn das Ultraschall-Ergebnis den Stent als disloziert beschrieb, wurde eine Röntgenaufnahme durchgeführt. Die Endpunkte waren der positive und negative Vorhersagewert, die Spezifität, Sensitivität und der Kontingenzkoeffizient zwischen Ultraschall und Röntgen und/oder Endoskopie.

Ergebnisse

88 Patienten wurden in die Studie eingeschlossen. Bei 23 (26%) Patienten musste eine Röntgenaufnahme durchgeführt werden. Entsprechend hat der Ultraschall-Algorithmus in 65 Fällen (74%) eine Röntgenuntersuchung eingespart. Stents waren bei 67 Patienten (76%) verblieben und wurden bei 54 Patienten korrekt mit einer Sensitivität von 81% mittels Ultraschall visualisiert. Der positive Vorhersagewert betrug 83%. Die Spezifität betrug 48%, da der Ultraschall 10/21 dislozierte Stents korrekt beschrieb. Der negative Vorhersagewert betrug 43%, da 10/23 Stents korrekt als disloziert klassifiziert wurden. Bei 11 Patienten (13%) wurde eine Ösophagogastroduodenoskopie durchgeführt, obwohl der Pankreas-Stent bereits disloziert war.

Fazit

Ein ultraschallbasierter Algorithmus reduzierte den Bedarf an Röntgen-Bildgebung um 3/4. Um unnötige endoskopische Untersuchungen zu vermeiden, sollte der Algorithmus mit einer Lernphase implementiert und das Verfahren von erfahrenen Untersuchern durchgeführt werden. Eine wichtige Einschränkung könnte die Länge der Stents sein, da kürzere Stents mit Ultraschall schwieriger zu visualisieren sein könnten.

Keywords

ERCP - ultrasound - x-ray - abdomen - post-ERCP pancreatitis

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