The influence of anastomotic techniques on postoperative anastomotic complications: Results of the Oesophago-Gastric Anastomosis Audit

BACKGROUND

The optimal anastomotic techniques in esophagectomy to minimize rates of anastomotic leakage and conduit necrosis are not known. The aim of this study was to assess whether the anastomotic technique was associated with anastomotic failure after esophagectomy in the international Oesophago-Gastric Anastomosis Audit cohort.

METHODS

This prospective observational multicenter cohort study included patients undergoing esophagectomy for esophageal cancer over 9 months during 2018. The primary exposure was the anastomotic technique, classified as handsewn, linear stapled, or circular stapled. The primary outcome was anastomotic failure, namely a composite of anastomotic leakage and conduit necrosis, as defined by the Esophageal Complications Consensus Group. Multivariable logistic regression modeling was used to identify the association between anastomotic techniques and anastomotic failure, after adjustment for confounders.

RESULTS

Of the 2238 esophagectomies, the anastomosis was handsewn in 27.1%, linear stapled in 21.0%, and circular stapled in 51.9%. Anastomotic techniques differed significantly by the anastomosis sites (P < .001), with the majority of neck anastomoses being handsewn (69.9%), whereas most chest anastomoses were stapled (66.3% circular stapled and 19.3% linear stapled). Rates of anastomotic failure differed significantly among the anastomotic techniques (P < .001), from 19.3% in handsewn anastomoses, to 14.0% in linear stapled anastomoses, and 12.1% in circular stapled anastomoses. This effect remained significant after adjustment for confounding factors on multivariable analysis, with an odds ratio of 0.63 (95% CI, 0.46-0.86; P = .004) for circular stapled versus handsewn anastomosis. However, subgroup analysis by anastomosis site suggested that this effect was predominantly present in neck anastomoses, with anastomotic failure rates of 23.2% versus 14.6% versus 5.9% for handsewn versus linear stapled anastomoses versus circular stapled neck anastomoses, compared with 13.7% versus 13.8% versus 12.2% for chest anastomoses.

CONCLUSIONS

Handsewn anastomoses appear to be independently associated with higher rates of anastomotic failure compared with stapled anastomoses. However, this effect seems to be largely confined to neck anastomoses, with minimal differences between techniques observed for chest anastomoses. Further research into standardization of anastomotic approach and techniques may further improve outcomes.

Textbook outcome following oesophagectomy for cancer: international cohort study

Background

Textbook outcome has been proposed as a tool for the assessment of oncological surgical care. However, an international assessment in patients undergoing oesophagectomy for oesophageal cancer has not been reported. This study aimed to assess textbook outcome in an international setting.

Methods

Patients undergoing curative resection for oesophageal cancer were identified from the international Oesophagogastric Anastomosis Audit (OGAA) from April 2018 to December 2018. Textbook outcome was defined as the percentage of patients who underwent a complete tumour resection with at least 15 lymph nodes in the resected specimen and an uneventful postoperative course, without hospital readmission. A multivariable binary logistic regression model was used to identify factors independently associated with textbook outcome, and results are presented as odds ratio (OR) and 95 per cent confidence intervals (95 per cent c.i.).

Results

Of 2159 patients with oesophageal cancer, 39.7 per cent achieved a textbook outcome. The outcome parameter ‘no major postoperative complication’ had the greatest negative impact on a textbook outcome for patients with oesophageal cancer, compared to other textbook outcome parameters. Multivariable analysis identified male gender and increasing Charlson comorbidity index with a significantly lower likelihood of textbook outcome. Presence of 24-hour on-call rota for oesophageal surgeons (OR 2.05, 95 per cent c.i. 1.30 to 3.22; P = 0.002) and radiology (OR 1.54, 95 per cent c.i. 1.05 to 2.24; P = 0.027), total minimally invasive oesophagectomies (OR 1.63, 95 per cent c.i. 1.27 to 2.08; P &lt; 0.001), and chest anastomosis above azygous (OR 2.17, 95 per cent c.i. 1.58 to 2.98; P &lt; 0.001) were independently associated with a significantly increased likelihood of textbook outcome.

Conclusion

Textbook outcome is achieved in less than 40 per cent of patients having oesophagectomy for cancer. Improvements in centralization, hospital resources, access to minimal access surgery, and adoption of newer techniques for improving lymph node yield could improve textbook outcome.

Textbook outcome following oesophagectomy for cancer: international cohort study

BACKGROUND

Textbook outcome has been proposed as a tool for the assessment of oncological surgical care. However, an international assessment in patients undergoing oesophagectomy for oesophageal cancer has not been reported. This study aimed to assess textbook outcome in an international setting.

METHODS

Patients undergoing curative resection for oesophageal cancer were identified from the international Oesophagogastric Anastomosis Audit (OGAA) from April 2018 to December 2018. Textbook outcome was defined as the percentage of patients who underwent a complete tumour resection with at least 15 lymph nodes in the resected specimen and an uneventful postoperative course, without hospital readmission. A multivariable binary logistic regression model was used to identify factors independently associated with textbook outcome, and results are presented as odds ratio (OR) and 95 per cent confidence intervals (95 per cent c.i.).

RESULTS

Of 2159 patients with oesophageal cancer, 39.7 per cent achieved a textbook outcome. The outcome parameter 'no major postoperative complication' had the greatest negative impact on a textbook outcome for patients with oesophageal cancer, compared to other textbook outcome parameters. Multivariable analysis identified male gender and increasing Charlson comorbidity index with a significantly lower likelihood of textbook outcome. Presence of 24-hour on-call rota for oesophageal surgeons (OR 2.05, 95 per cent c.i. 1.30 to 3.22; P = 0.002) and radiology (OR 1.54, 95 per cent c.i. 1.05 to 2.24; P = 0.027), total minimally invasive oesophagectomies (OR 1.63, 95 per cent c.i. 1.27 to 2.08; P < 0.001), and chest anastomosis above azygous (OR 2.17, 95 per cent c.i. 1.58 to 2.98; P < 0.001) were independently associated with a significantly increased likelihood of textbook outcome.

CONCLUSION

Textbook outcome is achieved in less than 40 per cent of patients having oesophagectomy for cancer. Improvements in centralization, hospital resources, access to minimal access surgery, and adoption of newer techniques for improving lymph node yield could improve textbook outcome.

Development and evaluation of an objective laparoscopic assessment tool: LapPass®

INTRODUCTION

Laparoscopic surgery is technically challenging and assessment of competency is necessary to ensure patient safety and guide training. We report on the development of LapPass®, an accessible objective simulation assessment tool with credentialing potential. We provide a preliminary evaluation of its usability and aspects of validity.

METHODS

The domains of LapPass® were defined through a consensus process by the executive council of the Association of Laparoscopic Surgeons of Great Britain and Ireland (ALSGBI). A survey of both assessors and trainees was used to test for usability, face and content validity of LapPass®. Internal consistency was tested with Cronbach's alpha, and a composite marker of validity and usability was obtained.

RESULTS

LapPass® was developed to consist of four tasks: (1) grasping and manipulation, (2) simulated appendicectomy, (3) cutting a disk and (4) intracorporeal suturing. A total of 76 participants contributed to the evaluation of LapPass®: 13 assessors and 63 trainees. For assessors, Cronbach's alpha for usability of tasks 1-4 was 0.84, 0.84, 0.76 and 0.86, whereas validity was 0.80, 0.85, 0.88, 0.95, respectively. For trainees, Cronbach's alpha was 0.75, 0.77, 0.80 and 0.85 for usability, and 0.79, 093, 0.87 and 0.91 for validity. Consensus was that each task was usable and had face and content validity, with median scores of 4.0 or higher (interquartile range 0.0-1.0).

CONCLUSION

LapPass® has potential for the objective assessment of basic laparoscopic skills but further research is required to explore its predictive capabilities in a clinical setting.

Postoperative outcomes in oesophagectomy with trainee involvement

BACKGROUND

The complexity of oesophageal surgery and the significant risk of morbidity necessitates that oesophagectomy is predominantly performed by a consultant surgeon, or a senior trainee under their supervision. The aim of this study was to determine the impact of trainee involvement in oesophagectomy on postoperative outcomes in an international multicentre setting.

METHODS

Data from the multicentre Oesophago-Gastric Anastomosis Study Group (OGAA) cohort study were analysed, which comprised prospectively collected data from patients undergoing oesophagectomy for oesophageal cancer between April 2018 and December 2018. Procedures were grouped by the level of trainee involvement, and univariable and multivariable analyses were performed to compare patient outcomes across groups.

RESULTS

Of 2232 oesophagectomies from 137 centres in 41 countries, trainees were involved in 29.1 per cent of them (n = 650), performing only the abdominal phase in 230, only the chest and/or neck phases in 130, and all phases in 315 procedures. For procedures with a chest anastomosis, those with trainee involvement had similar 90-day mortality, complication and reoperation rates to consultant-performed oesophagectomies (P = 0.451, P = 0.318, and P = 0.382, respectively), while anastomotic leak rates were significantly lower in the trainee groups (P = 0.030). Procedures with a neck anastomosis had equivalent complication, anastomotic leak, and reoperation rates (P = 0.150, P = 0.430, and P = 0.632, respectively) in trainee-involved versus consultant-performed oesophagectomies, with significantly lower 90-day mortality in the trainee groups (P = 0.005).

CONCLUSION

Trainee involvement was not found to be associated with significantly inferior postoperative outcomes for selected patients undergoing oesophagectomy. The results support continued supervised trainee involvement in oesophageal cancer surgery.

Mortality from esophagectomy for esophageal cancer across low, middle, and high-income countries: An international cohort study

BACKGROUND

No evidence currently exists characterising global outcomes following major cancer surgery, including esophageal cancer. Therefore, this study aimed to characterise impact of high income countries (HIC) versus low and middle income countries (LMIC) on the outcomes following esophagectomy for esophageal cancer.

METHOD

This international multi-center prospective study across 137 hospitals in 41 countries included patients who underwent an esophagectomy for esophageal cancer, with 90-day follow-up. The main explanatory variable was country income, defined according to the World Bank Data classification. The primary outcome was 90-day postoperative mortality, and secondary outcomes were composite leaks (anastomotic leak or conduit necrosis) and major complications (Clavien-Dindo Grade III - V). Multivariable generalized estimating equation models were used to produce adjusted odds ratios (ORs) and 95% confidence intervals (CI95%).

RESULTS

Between April 2018 to December 2018, 2247 patients were included. Patients from HIC were more significantly older, with higher ASA grade, and more advanced tumors. Patients from LMIC had almost three-fold increase in 90-day mortality, compared to HIC (9.4% vs 3.7%, p < 0.001). On adjusted analysis, LMIC were independently associated with higher 90-day mortality (OR: 2.31, CI95%: 1.17-4.55, p = 0.015). However, LMIC were not independently associated with higher rates of anastomotic leaks (OR: 1.06, CI95%: 0.57-1.99, p = 0.9) or major complications (OR: 0.85, CI95%: 0.54-1.32, p = 0.5), compared to HIC.

CONCLUSION

Resections in LMIC were independently associated with higher 90-day postoperative mortality, likely reflecting a failure to rescue of these patients following esophagectomy, despite similar composite anastomotic leaks and major complication rates to HIC. These findings warrant further research, to identify potential issues and solutions to improve global outcomes following esophagectomy for cancer.

Preterm Prelabor Rupture of Membranes: Outcomes with Expectant Management until 34 versus 35 Weeks

OBJECTIVE

To evaluate outcomes with expectant management of preterm prelabor rupture of membranes (PROM) until 35 weeks versus immediate delivery at ≥34 weeks.

STUDY DESIGN

This was a multicenter retrospective cohort study of singletons with preterm PROM at >20 weeks from 2011 through 2017. Groups were defined as expectant management until 35 weeks versus immediate delivery at ≥34 weeks. Primary outcome was composite neonatal morbidity: need for respiratory support, culture positive neonatal sepsis, or antibiotic administration for >72 hours. Univariate and general estimating equation models were used with p < 0.05 considered significant.

RESULTS

A total of 280 mother-infant dyads were included. There was no difference in composite neonatal outcome in pregnancies managed with expectant management compared with immediate delivery (43.4 vs. 37.5%; p = 0.32). Those with expectant management had shorter length of neonatal intensive care unit (NICU) admission but higher rates of neonatal antibiotics for > 72 hours, endometritis, and histological chorioamnionitis. There were no cases of fetal demise, neonatal death, or maternal sepsis, and only three cases of neonatal sepsis.

CONCLUSION

There is no difference in composite neonatal morbidity in pregnancies with preterm PROM managed with expectant management until 35 weeks as compared with immediate delivery at 34 weeks. Expectant management is associated with a decreased length of NICU admission but increased short-term infectious morbidity.

Maternal obesity: significance on the preterm neonate

BACKGROUND

What is known of neonatal outcomes associated with maternal obesity is limited. The impact on the preterm neonate, delivery room (DR) course and need for neonatal intensive care unit (NICU) admission has not been well established.

METHODS

A review was done of our 17 county perinatal regions from the New York State Perinatal Data System database over the 3-year period of 1 January 2010-31 December 2012 for mother/baby dyad information for all live births 34-36 6/7 weeks' gestation. The National Institutes of Health body mass index (BMI) classification was used for maternal BMI with the category definitions of underweight, normal, overweight, obese Level I, obese Level II, and obese Level III.

RESULTS

Information was obtained on 2155 women. In this group, 29% had obese BMIs. The incidence of pre-pregnancy diabetes mellitus (DM), DM during gestation and cesarean delivery (CD) in obese mothers was significantly different from normal weight mothers, P<0.001. More infants of Level III mothers required DR resuscitation when compared with infants of normal BMI mothers, 36 vs 16%, P <0.001. The need for assisted ventilation beyond 6 h of age and need for NICU admission was more likely in infants of Level III mothers, P<0.001. Women in all of the obese subgroups had preterm infants with increased birth weights (BWs) compared with preterm infants of normal weight mothers, P<0.001.

DISCUSSION

Late preterm infants born to obese mothers are more likely to be delivered by cesarean section and have larger BWs. We found that infants born to obese Level III mothers are much more likely to require assisted ventilation in the DR and NICU admission.

Computer science security research and human subjects: emerging considerations for research ethics boards

This paper explores the growing concerns with computer science research, and in particular, computer security research and its relationship with the committees that review human subjects research. It offers cases that review boards are likely to confront, and provides a context for appropriate consideration of such research, as issues of bots, clouds, and worms enter the discourse of human subjects review.

The risk of gallbladder cancer from polyps in a large multiethnic series

BACKGROUND

The aim of this study is assess whether patients with Indian ethnic background are at an increased risk of developing gallbladder cancer (GBC) if they have been diagnosed with ultrasonic abnormalities of the gallbladder.

METHODS

Between January 1998 and July 2006, 137,655 abdominal ultrasound examinations were performed in Leeds Teaching Hospitals NHS Trust. After the exclusion of repeat scans and those performed for renal or pelvic disease, 71,431 reports were included in this analysis. Patients in whom the diagnosis of GBC has been made without histology have been identified from the database of Northern and Yorkshire Cancer Registry and the presence of GBC was correlated with ultrasonic gallbladder abnormalities.

RESULTS

Gallbladder polyps (GBP) were detected in 3.3% of patients and these were larger than 10 mm in 0.1% of the cases. Age above 60 years, Indian ethnic background, single GBP larger than 10mm, the presence of gallstones, severe gallbladder wall thickening and irregular thickening were independently associated with the higher odds of developing GBC. The prevalence of malignancy in those with GBP was significantly higher among patients with Indian ethnic background compared to Caucasian patients, 5.5% versus 0.08%, p<0.001.

CONCLUSIONS

The presence of GBP, irrelevant of size, amongst patients of Indian ethnic decent, is an indication for further investigation and/or cholecystectomy.

An unusual case of ureteric obstruction

We report a case of a 33-year-old female presenting with right sided abdominal pain, a right iliac fossa mass and right hydronephrosis. The mass was subsequently shown to represent an isolated desmoid tumour compromising the adjacent ureter. The patient had no predisposing factors for this pathology. This is an uncommon occurrence and we discuss the imaging features and differential diagnosis.

DNA damage levels are raised in Barrett's oesophageal mucosa relative to the squamous epithelium of the oesophagus

Barrett's oesophagus (BE) is a pre-malignant metaplastic tissue predisposing to oesophageal adenocarcinoma (EC), and gastro-oesophageal reflux is a risk factor for both conditions. Reflux of acid and bile can cause mucosal injury and initiate chronic inflammation. These processes can induce DNA damage, possibly via an oxidative stress mechanism, thus increasing the likelihood of progression from Barrett's metaplasia to dysplasia and finally carcinoma. The comet assay was optimized for the detection of DNA damage (strand breaks and alkali-labile sites) in oesophageal biopsies, including incorporation of the DNA repair enzyme Fapy-DNA glycosylase (Fpg). Fpg allows the detection of 8-hydroxy-2-deoxyguanosine (8-OHdG) sites, a known pro-mutagenic DNA lesion. BE patients were recruited from BE surveillance clinics and oesophageal biopsies collected at endoscopy. Comet analysis revealed significantly increased (p < 0.001) DNA damage in Barrett's epithelium compared with matched squamous epithelium, with median % tail DNA values of 25.1% (first to third quartile 21.7-29.6%) and 18.6% (first to third quartile 16.9-21.4%), respectively. The median % tail DNA was up to 70% higher in the matched BE tissue compared with squamous epithelium from the same patient. Fpg sensitive sites were demonstrated in both tissue types at similar levels. The raised level of DNA damage in the premalignant BE may contribute to the accumulation of genetic alterations occurring during progression to EC. Understanding these underlying mechanisms provides a basis for cancer prevention strategies in BE patients.

Chromoendoscopy with methylene blue and associated DNA damage in Barrett's oesophagus

Chromoendoscopy with methylene blue has been proposed to improve targeting of biopsies to specialised intestinal metaplasia and dysplasia in Barrett's oesophagus. However, methylene blue can induce oxidative damage of DNA when photosensitised by white light. We show that damage to DNA is increased in Barrett's mucosa after chromoendoscopy with methylene blue, an effect apparently dependent on presence of both methylene blue and endoscopic white light. Exposure of Barrett's mucosa to DNA damage during endoscopy warrants caution since it could accelerate carcinogenesis. This risk needs to be carefully balanced against the possible benefit of improved early detection of preneoplastic lesions with methylene blue chromoendoscopy.

Micropuncture cholecystectomy vs conventional laparoscopic cholecystectomy: a randomized controlled trial

BACKGROUND

The aim of this study was to compare micropuncture laparoscopic cholecystectomy (MPLC), with three 3.3-mm cannulas and one 10-mm cannula with conventional laparoscopic cholecystectomy (CLC).

METHODS

Patients were randomized to undergo either CLC or MPLC. The duration of each operative stage and the procedure were recorded. Interleukin-6 (IL-6), adrenocorticotropic hormone (ACTH), and vasopressin were sampled for 24 h. Visual analogue pain scores (VAPS) and analgesic consumption were recorded for 1 week. Pulmonary function and quality of life (EQ-5D) were monitored for 4 weeks. Statistical analysis was performed using the Mann-Whitney test or Fisher's exact test. Results are expressed as median (interquartile range).

RESULTS

Forty-four patients entered the study, but four were excluded due to unsuspected choledocholithiasis (n = 3) or the need to reschedule surgery (n = 1). The groups were comparable in terms of age, duration of symptoms, and indications for surgery. Total operative time was similar (CLC, 63 [52-81] min vs MPLC 74 [58-95] min; p = 0.126). However, time to place the cannulas after skin incision (CLC, 5:42 [3:45-6:37] min vs MPLC, 7:38 [5:57-10:15] min; p = 0.015) and to clip the cystic duct after cholangiography (CLC, 1:05 [0:40-1:35] min vs MPLC, 3:45 [2:26-7:49] min; p <0.001) were significantly longer for MPLC. Six CLC patients and one MPLC patient required postoperative parenteral opiates (p = 0.04). Oral analgesic consumption was similar in both groups (p = 0.217). Median VAPS were lower at all time points for MPLC, but this finding was not significant (p = 0.431). There were no significant differences in postoperative stay, IL-6, ACTH or vasopressin responses, pulmonary function, or EQ-5D scores.

CONCLUSIONS

The thinner instruments did not significantly increase the total duration of the procedure. MPLC reduced the use of parenteral analgesia postoperatively, which may prove beneficial for day case patients, but it did not have a significant impact on laboratory variables, lung function or quality of life.

Predicting mortality and morbidity of patients operated on for perforated peptic ulcers

HYPOTHESIS

Since the early 1990s, the laparoscopic technique has been increasingly used for the treatment of perforated peptic ulcer. It is important to validate a risk scoring system that can stratify patients into various risk groups before comparing the treatment outcome of laparoscopic repair against that of conventional open surgery. The scoring system should be able to predict the likelihood of mortality and morbidity. Boey score and APACHE II (Acute Physiology and Chronic Health Evaluation II) score may be of use in patient stratification.

DESIGN

Retrospective review of relevant case notes by one reviewer.

SETTING

A teaching hospital treating 0. 5 million to 1 million patients during the study period.

PATIENTS

Patients operated on for perforated peptic ulcer between January 1989 and December 1998. Patients treated conservatively were excluded.

MAIN OUTCOME MEASURES

Mortality and postoperative complications (morbidity).

RESULTS

A total of 436 patients (365 male and 71 female) with a mean +/- SD age of 51.5 +/- 18.3 years (range, 14-92 years) were studied. Duodenal perforation accounted for 344 (78.9%) of 436 cases. The mortality rate was 7.8% (34/436), and 89 patients had postoperative complications. Multivariate analysis demonstrated that only the APACHE II score predicted both mortality and morbidity. Although the Boey score predicted mortality, it failed to predict morbidity. However, the Boey score predicted the chance of conversion in patients undergoing laparoscopic repair.

CONCLUSIONS

The APACHE II score may be a useful tool for stratifying patients into various risk groups, and the Boey score might select appropriate patients for laparoscopic repair.

Molecular, biochemical and functional analysis of a novel and developmentally important fibrillar collagen (Hcol-I) in hydra

The body wall of hydra (a member of the phylum Cnidaria) is structurally reduced to an epithelial bilayer with an intervening extracellular matrix (ECM). Previous studies have established that cell-ECM interactions are important for morphogenesis and cell differentiation in this simple metazoan. The ECM of hydra is particularly interesting because it represents a primordial form of matrix. Despite progress in our understanding of hydra ECM, we still know little about the nature of hydra collagens. In the current study we provide a molecular, biochemical and functional analysis of a hydra fibrillar collagen that has similarity to vertebrate type I and type II collagens. This fibrillar collagen has been named hydra collagen-I (Hcol-I) because of its structure and because it is the first ECM collagen to be identified in hydra. It represents a novel member of the collagen family. Similar to vertebrate type I and II collagens, Hcol-I contains an N-terminal propeptide-like domain, a triple helical domain containing typical Gly-X-Y repeats and a C-terminal propeptide domain. The overall identity to vertebrate fibrillar collagens is about 30%, while the identity of the C-terminal propeptide domain is 50%. Because the N-terminal propeptide domain is retained after post-translational processing, Hcol-I does not form thick fibers as seen in vertebrates. This was confirmed using transmission electron microscopy to study rotary shadow images of purified Hcol-I. In addition, absence of crucial lysine residues and an overall reduction in proline content, results in reduced crosslinking of fibrils and increased flexibility of the molecule, respectively. These structural changes in Hcol-I help to explain the flexible properties of hydra ECM. Immunocytochemical studies indicate that Hcol-I forms the 10 nm fibrils that comprise the majority of molecules in the central fibrous zone of hydra ECM. The central fibrous zone resides between the two subepithelial zones where hydra laminin is localized. While previous studies have shown that basal lamina components like laminin are expressed by the endoderm, in situ hybridisation studies show that Hcol-I mRNA expression is restricted to the ectoderm. Hcol-I expression is upregulated during head regeneration, and antisense studies using thio-oligonucleotides demonstrated that blocking the translation of Hcol-I leads to a reversible inhibition of head morphogenesis during this regenerative process. Taken in total, the data presented in this study indicate that Hcol-I is required for morphogensis in hydra and represents a novel fibrillar collagen whose structural characteristics help to explain the unique biophysical properties of hydra ECM. Interestingly, the structure of Hcol-I mimics what is seen in Ehlers-Danlos syndrome type VII in humans; an inherited pathological condition that leads to joint and skin abnormalities. Hcol-I therefore illustrates an adaptive trait in which the normal physiological situation in hydra translates into a pathological condition in humans.

Identification and characterization of hydra metalloproteinase 2 (HMP2): a meprin-like astacin metalloproteinase that functions in foot morphogenesis

Several members of the newly emerging astacin metalloproteinase family have been shown to function in a variety of biological events, including cell differentiation and morphogenesis during both embryonic development and adult tissue differentiation. We have characterized a new astacin proteinase, hydra metalloproteinase 2 (HMP2) from the Cnidarian, Hydra vulgaris. HMP2 is translated from a single mRNA of 1.7 kb that contains a 1488 bp open reading frame encoding a putative protein product of 496 amino acids. The overall structure of HMP2 most closely resembles that of meprins, a subgroup of astacin metalloproteinases. The presence of a transient signal peptide and a putative prosequence indicates that HMP2 is a secreted protein that requires post-translational processing. The mature HMP2 starts with an astacin proteinase domain that contains a zinc binding motif characteristic of the astacin family. Its COOH terminus is composed of two potential protein-protein interaction domains: an “MAM” domain (named after meprins, A-5 protein and receptor protein tyrosine phosphatase mu) that is only present in meprin-like astacin proteinases; and a unique C-terminal domain (TH domain) that is also present in another hydra metalloproteinase, HMP1, in Podocoryne metalloproteinase 1 (PMP1) of jellyfish and in toxins of sea anemone. The spatial expression pattern of HMP2 was determined by both mRNA whole-mount in situ hybridization and immunofluorescence studies. Both morphological techniques indicated that HMP2 is expressed only by the cells in the endodermal layer of the body column of hydra. While the highest level of HMP2 mRNA expression was observed at the junction between the body column and the foot process, immunofluorescence studies indicated that HMP2 protein was present as far apically as the base of the tentacles. In situ analysis also indicated expression of HMP2 during regeneration of the foot process. To test whether the higher levels of HMP2 mRNA expression at the basal pole related to processes underlying foot morphogenesis, antisense studies were conducted. Using a specialized technique named localized electroporation (LEP), antisense constructs to HMP2 were locally introduced into the endodermal layer of cells at the basal pole of polyps and foot regeneration was initiated and monitored. Treatment with antisense to HMP2 inhibited foot regeneration as compared to mismatch and sense controls. These functional studies in combination with the fact that HMP2 protein was expressed not only at the junction between the body column and the foot process, but also as far apically as the base of the tentacles, suggest that this meprin-class metalloproteinase may be multifunctional in hydra.