Composition of clogging material in pancreatic endoprostheses

Quantification and differentiation of composition of mixed pancreatic duct stones using single-source dual-energy CT: an ex vivo study

PURPOSE

To evaluate the feasibility of using single-source dual-energy CT (SS DECT) to quantify and differentiate calcium carbonate (CA) and non-calcium carbonate (NCA) components of pancreatic duct stones (PDS) with mixed composition.

MATERIALS AND METHODS

A total of 12 PDS harvested from general surgery department in our hospital were analyzed with micro-CT as a reference standard for CA and NCA composition. These stones were placed in a TOS water phantom of 35 cm diameter to simulate standard adult body size. High- and low-energy image sets were acquired from SS DECT scans with high/low tube potential pairs of 80 kVp/140 kVp. All the image sets were imported into an in-house software for further post-processing. CT number ratio (CTR), defined as the ratio of the CT number at 80 kVp to 140 kVp was calculated for each pixel of the images. Threshold was preset between 1.00 and 1.25 to classify CA and NCA components. Pixels in PDS with CTR higher than the threshold were classified as CA, and those with CTR lower than the threshold were classified as NCA. The percentages of CA and NCA for each stone were determined by calculating the number of CA and NCA pixels. Finally, the minimal, maximal and root-mean-square errors (RMSE) of composition measured by SS DECT under each threshold were calculated by referring to the composition data from micro-CT. The optimal threshold was determined with the minimal RMSE. A paired t test was used to compare the stone composition determined by DECT with micro-CT.

RESULTS

The optimal CTR threshold was 1.16, with RMSE of 6.0%. The minimum and maximum absolute errors were 0.22% and 11.35%, respectively. Paired t test showed no significant difference between DECT and micro-CT for characterizing CA and NCA composition (p = 0.414).

CONCLUSION

SS DECT is a potential approach for quantifying and differentiating CA and NCA components in PDS with mixed composition.

10 Fr S-Type Plastic Pancreatic Stents in Chronic Pancreatitis Are Effective for the Treatment of Pancreatic Duct Strictures and Pancreatic Stones

AIM

Endoscopic pancreatic stenting for refractory pancreatic duct strictures associated with impacted pancreatic stones in chronic pancreatitis cases has yielded conflicting results. We retrospectively evaluated the efficacy of endoscopic treatment in chronic pancreatitis patients with pancreatic duct strictures.

METHODS

Pancreatic sphincterotomy, dilatation procedures, pancreatic brush cytology, and pancreatic juice cytology were routinely performed, and malignant diseases were excluded. After gradual dilatation, a 10 Fr plastic pancreatic stent was inserted. The stents were replaced every 3 months and removed after the strictures were dilated. Statistical analyses were performed to determine the risk of main pancreatic duct restenosis.

RESULTS

Endoscopic pancreatic stents were successfully placed in 41 of a total of 59 patients (69.5%). The median duration of pancreatic stenting was 276 days. Pain relief was obtained in 37 of 41 patients (90.2%). Seventeen patients (41.5%) had recurrence of main pancreatic duct stricture, and restenting was performed in 16 patients (average placement period 260 days). During the follow-up period, pancreatic cancer developed in three patients (5.1%). Multivariate analysis revealed that the presence of remnant stones after stenting treatment was significantly associated with a higher rate of main pancreatic duct restenosis (p = 0.03).

CONCLUSION

The use of 10 Fr S-type plastic pancreatic stents with routine exchange was effective for both short-term and long-term outcomes in chronic pancreatitis patients with benign pancreatic duct strictures and impacted pancreatic stones.

Feasibility of the unilateral-flange stent for the treatment of benign pancreatic duct stricture: a pilot study

Endoscopic placement of the plastic stent has been adopted as an initial treatment for chronic pancreatitis with pancreatic duct stricture. Stent fracture while attempting removal is one of the complications of stent exchange. The use of the unilateral-flange stent in these patients has never been reported. We investigated the outcomes associated with the use of this stent with regard to stent exchange and stent-related adverse events. From 2011 to 2015, 9 patients with chronic pancreatitis and main pancreatic duct (MPD) stricture treated with the unilateral-flange stent were included. Eleven endoscopic treatment sessions, 53 endoscopic stent deployments or exchange procedures were analyzed. Technical success rate was 100%. Forty-eight stents were exchanged on a regular basis in 1 to 6-month intervals. Another 5 stent exchange procedures were urgently performed due to stent obstruction and caused pancreatitis (n=2), symptomatic external stent migration (n=2), and concurrent cholangitis (n=1). The rate of symptomatic migration was 3.7%. The mean duration for stent exchange was 29 minutes and no stent fracture occurred during the procedure. Of 11 endoscopic treatment sessions, 7 were successful, 3 were changed to the metallic stents, and 1 was lost to follow-up. According to this study, unilateral-flange stent placement for benign MPD stricture is technically feasible and effective. Stent removal during the exchange period is unchallenging and without stent fracture.

Endoscopic Drainage of >50% of Liver in Malignant Hilar Biliary Obstruction Using Metallic or Fenestrated Plastic Stents

OBJECTIVES

Endoscopic drainage of complex hilar tumors has generally resulted in poor outcomes. Drainage of >50% of liver volume has been proposed as optimal, but not evaluated using long multifenestrated plastic stents (MFPS) or self-expanding metal stents (SEMS). We evaluated outcomes of endoscopic drainage of malignant hilar strictures using optimal strategy and stents, and determined factors associated with stent patency, survival, and complications.

METHODS

Cross-sectional study was conducted at an academic center over 5 years. MFPS (10 French or 8.5 French) or open-cell SEMS were used for palliation of unresectable malignant hilar strictures, with imaging-targeted drainage of as many sectors as needed to drain >50% of viable liver volume. Risk factors were evaluated using regression analysis. The cumulative risk was assessed using Kaplan-Meier analysis.

RESULTS

77 patients with malignant hilar biliary strictures (median Bismuth IV) underwent targeted stenting (41 MFPS and 36 SEMS). Comparing MFPS vs. SEMS, technical success (95.1 vs. 97.2%, P=0.64), clinical success (75.6 vs. 83.3%, P=0.40), frequency of multiple stents (23/41 vs. 25/36, P=0.19), survival and adverse events were similar, but stent patency was significantly shorter (P<0.0001). Factors associated with survival were Karnofsky score and serum bilirubin level at presentation. Outcomes were independent of Bismuth class with acceptable results in Bismuth III and IV.

CONCLUSIONS

Endoscopic biliary drainage with MFPS or open-cell SEMS targeting >50% of viable liver resulted in effective palliation in patients with complex malignant hilar biliary strictures. Patency was shorter in the MFPS group, but similar survival and complications were found when comparing MFPS and SEMS group.

Endoscopic therapy in chronic pancreatitis: current perspectives

Endoscopic therapy in chronic pancreatitis (CP) aims to provide pain relief and to treat local complications, by using the decompression of the pancreatic duct and the drainage of pseudocysts and biliary strictures, respectively. This is the reason for using it as first-line therapy for painful uncomplicated CP. The clinical response has to be evaluated at 6-8 weeks, when surgery may be chosen. This article reviews the main possibilities of endoscopic retrograde cholangiopancreatography (ERCP) and endoscopic ultrasound (EUS) therapies. Endotherapy for pancreatic ductal stones uses ultrasound wave lithotripsy and sometimes additional stone extractions. The treatment of pancreatic duct strictures consists of a single large stenting for 1 year. If the stricture persists, simultaneous multiple stents are applied. In case of unsuccessful ERCP, the EUS-guided drainage of the main pancreatic duct (MPD) or a rendezvous technique can solve the ductal strictures. EUS-guided celiac plexus block has limited efficiency in CP. The drainage of symptomatic or complicated pancreatic pseudocysts can be performed transpapillarily or transgastrically/transduodenally, preferably by EUS guidance. When the biliary stricture is symptomatic or progressive, multiple plastic stents are indicated. In conclusion, as in many fields of symptomatic treatment, endoscopy remains the first choice, either by using ERCP or EUS-guided procedures, after consideration of a multidisciplinary team with endoscopists, surgeons, and radiologists. However, what is crucial is establishing the right timing for surgery.

Obstructive component analysis of radioactive stents and common plastic stents in the bile duct

BACKGROUND

Endoscopic placement of a iodine-125 radioactive stent is useful to treat obstructive jaundice with unresectable periampullary tumors. This study aimed to retrospectively evaluate the obstructive component of biliary radioactive stents and discuss the different obstructive mechanism with common plastic stents.

PATIENTS AND METHODS

Twenty consecutive patients with malignant obstruction underwent insertion of stents into the common bile duct, including 10 radioactive stents and 10 polyethylene stents. The radioactive stents were withdrawn after ∼3 months or earlier if clinical signs suggested stent clogging. Polyethylene stents were withdrawn after physical signs suggested stent clogging. Bacteriologic analyses included identification of aerobic and anaerobic bacteria. Stent surfaces were observed by scanning electron microscopy. Stent deposition was identified by Fourier-transformed infrared spectroscopy and pyrolysis derivatization/gas chromatography/mass spectrometry.

RESULTS

Radioactive stent group and polyethylene stent group stents were placed for 86 days (interquartile range 62, 114) and 146 days (interquartile range 105, 181) respectively. The placement duration of the two types of stents was statistically significant. A variety of microorganisms were cultured from the stent deposits. Scanning electron microscope images showed a thicker necrotic layer on the external surface of polyethylene stent than the radioactive stent group. The proportions of obstructive components in each stent were different, but none of them were statistically significant. Necrotic tumor tissue was found in the radioactive stent group.

CONCLUSION

Similar clogging events occurred in both radioactive stents and polyethylene stents. The median duration time of the radioactive stent was shorter, probably because of the smaller inner diameter, and the radioactive seeds exerted no beneficial effect in inhibiting microorganisms.

Does heparin coating reduce encrustation of biliary plastic endoprostheses? A prospective randomized trial

OBJECTIVE

Common bile duct stenting is widely performed for bridging benign and malignant obstructions. A major limitation is early stent occlusion making regular stent exchange necessary. Covalent binding of glycosaminoglycanes to polyethylene stents proved to reduce encrustation in urological implants. Since development of urological and biliary stent occlusion shows parallels, the aim of the study was to evaluate the efficacy of heparin coating of biliary endoprostheses in preventing encrustation.

MATERIAL AND METHODS

In a prospective randomized trial, heparin-coated and native stents were endoscopically placed for almost 90 days on average. After removal, all stents were dried (50°C, 24 h), weighed and after longitudinal incision visible encrustation and discoloration recorded. Fifty-three patients (21 females/32 males, 70 ± 12 (42-87) years) were included; 13 patients (4 females/9 males, 58-79 years) completed the study according to the protocol.

RESULTS

After removal, mean weight of encrustation in native stents was more than double as high as of covered stents (native: 37.9 ± 19.8 (16-93) mg; covered: 17.6 ± 6.7 (9-33) mg). In 12 of 13 cases, the encrustation weight of the native stent was higher than that of the corresponding covered stent in the same patient. Premature stent explantation became necessary in 3 of 13 native stents, because of recurrent jaundice or cholangitis but only in 1 of 13 covered stents. After longitudinal incision, the three uncovered stents showed excessive encrustation whereas no significant encrustation was found in the covered prosthesis. Altogether, covered stents showed less visible accumulation of clogging material and discoloration than native stents.

CONCLUSIONS

Covalent bound heparin is highly effective in preventing encrustation of biliary polyethylene endoprostheses.

Cleaning of occluded pancreatic duct endoprostheses: a new indication for extracorporeal shock wave lithotripsy?

BACKGROUND

Pancreatic duct stenting is widely performed for bridging main pancreatic duct obstruction in patients with chronic pancreatitis. The major limitation is early stent occlusion, making regular stent exchange necessary.

OBJECTIVE

To date, no measures are available to prevent stent occlusion. The aim of this study was to evaluate the cleansing effect of shock wave application (SWA) on occluded pancreatic duct stents in vitro.

DESIGN

In vitro study.

PATIENTS

We analyzed occlusion rates of 25 plastic endoprostheses removed from 21 patients with chronic pancreatitis.

INTERVENTION

We administered 350 shock wave pulses every 10 mm along the prosthesis, which was stored in a latex balloon filled with gas-free physiologic saline solution, by using a pressure of 42 megapascals.

MAIN OUTCOME MEASUREMENTS

After SWA, the occlusion rate was measured again, and the cleansing rate was calculated in comparison with the native prosthesis.

RESULTS

The mean (± SD) occlusion rate was significantly reduced (64.7 ± 28.7 [15%-100%]) before SWA vs 9.8 ± 25.3 [0-100%]) after SWA; P = .038). In 16 of 25 prostheses (64%), cleaning was complete. Four of the remaining 9 prostheses (16%) showed satisfactory cleaning of 95%, on average. Residual clogging material was found mainly at the duodenal tip and the middle of the stent. No significant association was found between patient-related or stent-related parameters and the cleansing effect of SWA.

LIMITATIONS

In vitro study design.

CONCLUSION

SWA is effective in cleaning occluded pancreatic endoprostheses in vitro. Prolongation of stent placement seems possible if regular SWA is performed. Extracorporeal shock wave lithotripsy therefore might become a new indication for patients under treatment with pancreatic endoprostheses.

Endoscopic stenting for palliation of malignant biliary obstruction

Malignant biliary obstruction results in jaundice, often with symptoms that decrease the quality of life. Biliary stent placement has largely supplanted surgical bypass for palliation of malignant biliary obstruction. Traditional rigid plastic stents are commonly used, inexpensive and easily removed, although with limited duration of stent patency. Self-expandable metal stents (SEMS) attain larger luminal diameters and provide longer patency than traditional rigid plastic stents in patients with distal bile duct obstruction. SEMS are composed of a variety of metals and can be uncoated, partially covered, or fully covered. Data do not support a prolongation of patency with covered SEMS for distal obstruction, although they have the potential for removability. The data to support SEMS for palliation of hilar biliary obstruction are not as convincing and reintervention for stent occlusion can be difficult. In this article, the design and performance of expandable metal stents for treatment of malignant biliary obstruction will be reviewed.

Pancreatic stone protein/regenerating protein family in pancreatic and gastrointestinal diseases

Pancreatic stone protein (PSP; reported in 1979), pancreatitis-associated protein (PAP; 1984) and regenerating protein (Reg I; 1988) were discovered independently in the fields of the exocrine (pancreatitis) and endocrine (diabetes) pancreas. Subsequent analysis revealed that PSP and Reg I are identical and PAP belongs to the same protein family. PSP/Reg I and PAP share a selective and specific trypsin cleavage site and result in insoluble fibrils (PTP, PATP). Search for a functional role of PSP had led to the idea that it might serve as an inhibitor in pancreatic stone formation and PSP was renamed lithostathine. Inhibitory effects of lithostathine in stone formation have been questioned. Evidence so far obtained can support a lithogenic role rather than a lithostatic role of PSP. PAP and its isoforms have been investigated mainly regarding responses to inflammation and stress. Reg I and its isoforms have been examined on regeneration, growth and mitogenesis in gastrointestinal neoplastic diseases as well as diabetes. Evidence obtained can be applied in the prediction of prognosis and therapy for inflammatory and neoplastic diseases.

Endotherapy for pain in chronic pancreatitis

Pain is the most distressing symptom of chronic pancreatitis. Although the pathogenesis of pain is still poorly understood, an increase in intraductal pressure may be the dominant factor. The management of pain can involve medical, endoscopic, neurolytic, and surgical therapies. Endotherapy includes pancreatic sphincterotomy, extraction of stones, placement of stent, and dilatation of strictures, sometimes preceded or followed by extracorporeal shock-wave lithotripsy. Several studies have now shown that endotherapy provides partial or complete relief of pancreatic pain in a majority of patients with an acceptable frequency of early and late complications. Endotherapy should now graduate from an experimental form of treatment to a realistic treatment option in patients with chronic or relapsing pain, particularly in the setting of calcific chronic pancreatitis.

Proteomic analysis of protein plugs: causative agent of symptoms in patients with choledochal cyst

Symptoms of choledochal cysts are caused by protein plugs. We performed proteomic analysis of protein plugs to elucidate formation mechanism. Protein plugs were obtained from three pediatric patients with choledochal cyst. Proteins were separated using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Gel bands common to the samples were excised for mass spectrometry. Mass spectra were compared with the NCBI database for protein identification. Gel bands of protein plug samples were predominant at 14 kilodaltons (kDa), followed by 29 kDa. Four other thin bands were common to the plug samples. Four bands (including 14 and 29 kDa) were identified as lithostathine, and one band as serum albumin. Plugs consisted mostly of lithostathine, a protein secreted by pancreatic acinar cells into pancreatic juice. The mechanism involves trypsinogen and lithostathine regurgitating into the cyst through an aberrant union of pancreaticobiliary ducts. Activated trypsin cleaves soluble lithostathine into insoluble forms that aggregate to form plugs.

Pancreatic endoprostheses in chronic pancreatitis: criteria to predict stent occlusion

BACKGROUND

Good clinical results of main pancreatic duct (MPD) stent placement in chronic pancreatitis (CP) are clouded by early stent occlusion. The aim of this study was to increase knowledge about stent occlusion and its effects on clinical symptoms, and to define criteria that enable the prediction of clogging.

METHODS

A total of 100 pancreatic endoprostheses of 47 patients (32 men, 15 women; mean age, 53 years; standard deviation, 9 years) with CP were bench tested by simulating the pathophysiologically increased MPD pressure. The main study parameter was the reduction of water flow through clogged stents in comparison with native endoprostheses of identical type, length, and diameter. Major stent occlusion was defined as flow reduction by > or = 75%. The association between time to stent occlusion and stent- or patient-related variables was evaluated.

RESULTS

Occlusion took place in nearly all endoprostheses (97%). No significant association of occlusion with clinical or blood parameters was found. Multifactorial analysis proved 4 risk factors for major stent occlusion: (A) stent diameter > 8.5F, (B) stent length > 8 cm, (C) female gender, (D) exocrine pancreatic insufficiency that required regular oral enzyme supplementation. According to the relative risk, these factors were given the following scores: A, 3 points; B to D, 2 points. Stents in patients with a score sum > 5 showed a significantly higher risk of major stent occlusion within 90 days.

CONCLUSIONS

Stent clogging in CP seems to be an inevitable phenomenon. Because clinical and laboratory data do not reliably indicate clogging, stent removal or exchange should be performed in high-risk patients (score sum > 5) within 3 months.

Interventional endoscopic therapy in chronic pancreatitis including temporary stenting: a definitive treatment?

OBJECTIVE

In the past 15 years there have been tremendous advances in endoscopic management of chronic pancreatitis (CP). However, the value of endoscopic pancreatic stenting is still debatable.

MATERIAL AND METHODS

In 98 patients suffering from symptomatic CP (84 M, 14 F, 49+/-12, age range 23-83 years) endotherapy including temporary stenting of the pancreatic duct was performed. After final stent removal, indicating the primary end-point of endotherapy, 96 patients were followed for 35+/-28 (8 days-111) months. All data were assessed retrospectively.

RESULTS

As well as other endoscopic procedures, a total of 358 prostheses were inserted in the pancreatic duct and left in place for 3+/-1 (1 day-11) months. Total stent treatment time was 10+/-10 (6 days-49) months. At 46+/-27 (4-111) months after limited endotherapy, 57 patients had no need for secondary intervention, two-thirds were even without further pain sensations. In 22 patients, surgical treatment and in 17 patients further endoscopic therapy became necessary, which was significantly correlated with continued alcohol consumption.

CONCLUSIONS

Temporary stent placement as a part of interventional endoscopic therapy in CP shows a high rate of technical and long-term clinical success, with no need for secondary treatment in a remarkable number of patients. Continued cessation of alcohol consumption supports the treatment benefit significantly.