Patients
The study included 73 patients with mild-severe acute pancreatitis (MSAP) and severe acute pancreatitis (SAP) that were admitted to our hospital from January 2015 to January 2021. All patients developed WON with accompanying infection four weeks after the onset of MSAP/SAP and subsequently underwent PCD. MSAP, SAP, and WON were diagnosed on the basis of the revised standards of Atlanta [2]. The first 38 patients included from January 2015 to June 2018 underwent UC-PCD, whereas the next 35 patients included from June 2018 to January 2021 underwent CUC-PCD, as we gradually observed the efficacy of the choledochoscope for drainage tube placement in the process of UC-PCD. This study was performed in accordance with clinical study protocols and the principles of the Declaration of Helsinki (modified 2000) and was approved by the Research Care and Ethics Committee at our institution (No. SPPHCT2021–0012). Informed consent for the interventional procedures was obtained from all patients or their families. Data were collected and analysed retrospectively.
Inclusion and exclusion criteria
Inclusion criteria
(1) Adults (> 18 years old) who experienced their first episode of MSAP or SAP, and underwent PCD. (2) Only one WON (encapsulated aggregation) diagnosed according to abdominal CT images. (3) WON accompanied by infection (diagnostic basis: excessive leukocytes in routine blood examination, fever, and positive bacterial culture of the drainage liquid obtained by fine needle aspiration).
Exclusion criteria
(1) Patients with WON whose CT images showed no viable percutaneous puncture route for PCD. (2) Patients with independent and multiple WONs, needing several drainages. (3) Patients with autoimmune deficiency, suspected malignancy of the pancreas or biliary tree, or previous abdominal operation.
Technical procedures
Therapeutic equipment and materials
GE LOGIQ E9 diasonograph (from 3.5 to 5.0 MHz) with C1-5 probe (GE, USA), magnetic positioner and spare parts (GM, USA), disposable laparoscopic puncture trocar (JL5MN, Youjun Care, China), electronic choledochoscope (CHF-P60, Olympus, Japan), hydrophilic drainage catheter (Neo-Hydro, Bioteque Corp., Taiwan), T-tube (Zhanjiang Star Enterprise Co., Ltd., China), and guide wire (MTN-BM-89/45-A, Micro-tech Nanjing, China) were used.
PCD intervention
Location and size of the WON were assessed by two radiologists (> 5 years and 1000 times of CT-mediated abdominal punctures) by reviewing the imaging results. The PCD procedures were performed by attending surgeons with consistent technique and were guided by US doctors (> 5 years and 3000 times of US-mediated abdominal punctures).
Catheter placement by imaging fusion in UC-PCD
Patients in the UC-PCD group underwent real-time imaging fusion to determine the puncture pathway and drainage placement. Seldinger technique was performed by placement of a pig tail drainage catheter (8 Fr) along the route in the sloping position of the WON.
Tunnel establishment
According to previous reports, the ultrasound/CT image fusion-guided puncture procedures are briefly described as follows [12]: The CT images (DICOM format) for fusion were imported into the diasonograph to obtain the imaging data. Then, the popular in vivo visualisation method was used to offer a real-time display of the corresponding plane, using an US probe for scanning (Fig. 2a). The WON position, scope, and surrounding important organs were identified in the US and CT images (Fig. 2b). The trocar puncture point was determined, and a safe puncture pathway was displayed to facilitate the insertion of the choledochoscope into the WON. After marking the skin surface and administering local anaesthesia, the trocar was placed according to the quasi-puncture path to access the necrotic space under US guidance.
Catheter placement by choledochoscopy in CUC-PCD
The core of the trocar was slowly withdrawn (Fig. 3a), followed by choledochoscope insertion through the fixed trocar (Fig. 3b). Necrotic materials could be visualised by the choledochoscope (Fig. 3b1), which was guided by US/CT (Fig. 3b2) to reach the sloping position in the necrotic cavity. Then, a guidewire was introduced (Fig. 3b3), and a home-made multi-side-hole drainage catheter (16 Fr) was placed along the guidewire to the choledochoscope-guided position (Fig. 3c). To confirm the configuration and drainage range of the drainage catheter, a US contrast agent (SonoVue, Bracco Diagnostics Inc., Sweden) was injected into the catheter and visualised by means of contrast-enhanced US. Finally, the unobstructed catheter was used to drain the liquid abscess (Fig. 3d).
Catheter expansion and necrosectomy
When insufficient drainage of the liquefied necrotic tissue was observed 7 days after the initial intervention, patients underwent catheter expansion to dilatate the sinus tract under US guidance. In the UC-PCD group, the 8 Fr drainage tube was expanded to 16–24 Fr; while in CUC-PCD group, the 16 Fr T-tube was expanded to 20–24 Fr. The visualised necrotic materials were removed by a combination of cholangioscopic interventions, including intermittent lavage as well as extraction by basket and biopsy clamp.
Indicators for removal of the drainage catheter
The drainage tube was removed when all of the following conditions were satisfied: (1) absence of fever for three consecutive days; (2) no abdominal pain and a normal white blood cell count; (3) the necrotic cavity had shrunk to 2 cm or disappeared on a serial CT scan/US; and (4) less than 10 ml of fluid was drained from the abscess for 3 consecutive days.
Observation indicators
Observation indicators included the demographic indexes (sex, age) of the patients, aetiology, classification of AP, location of the WON, relevant laboratory inflammatory indexes (white blood cell [WBC] count, and C-reactive protein [CRP] level before and after PCD intervention), severity scores (acute physiology and chronic health evaluation [APACHE] II, computed tomography severity index [CTSI], and Ranson), necrotic fluids volume before and 48 h after the PCD procedure, operation indexes of PCD (including time from the onset to the first PCD, puncture area, diameter of the drainage tubes used, necrosectomy time), complications of PCD intervention and infection of AP, hospitalisation, and treatment costs. The size of the WON was measured by virtual organ computer-aided analysis (VOCAL) using three-dimensional US [13]. Effective imaging was defined as a decrease in the WON size, measured by VOCAL, by more than 60% after the PCD intervention compared to the size at the onset.
Statistical analyses
All statistical analyses were performed using SPSS 19.0 (IBM SPSS, USA). All data are presented as percentages or means ± standard deviation. Statistical comparisons were done by using the t test or Wilcoxon rank sum test for continuous variables, and the chi-square test or Fisher’s exact test for categorical variables. A p value < 0.05 was defined as significant.