Bodyweight, not age, determines oesophageal length and breaking strength in rats

A novel piglet model of esophageal stricture following variable segmental esophageal resection and re-anastomosis

BACKGROUND

Esophageal strictures following esophageal atresia repair are a source of significant morbidity. To test new therapeutic approaches, we designed a piglet model of esophageal stricture by resecting variable lengths of esophagus with subsequent re-anastomosis. This study describes the model and validates its physiologic impact by blinded analysis of the weight gains of the piglets.

METHODS

A total of 24 two-week old Pietrain piglets had esophageal resections performed, ranging from 0 to 5 cm, with the goal of inducing postoperative esophageal strictures. Postoperative body-weights were evaluated by repeated analysis of variance followed by pairwise group-comparisons based on estimated marginal means. In addition, body weight was modeled by linear-mixed model regression. Different resection lengths were compared. The esophagi were evaluated postmortem for stricture.

RESULTS

Of 24 operated piglets, 23 reached the endpoint, and 90% developed an esophageal stricture that was radiologically visible in a contrast study, as well as appreciable macroscopically in the necropsy. We found differences in pre- and postoperative body weights for all piglets (F (1, 18) = 298.54, p < 0.001), but no differences between resection lengths (F (4, 18) = 0.36, p = 0.837).

CONCLUSION

Our model of postoperative esophageal stricture offers the opportunity to investigate potential treatments for strictures associated with esophageal atresia, since it reliably induces strictures and results in minimal loss of animals. The similar body weight gain in all groups indicates that stricture is mainly the result of esophageal resection and re-anastomosis, regardless of the length of the resected segment.

Oblique conformal anastomosis decreased the risks of cervical anastomotic leakage after totally minimally invasive esophagectomy

OBJECTIVE

To investigate the effectiveness of the original oblique conformal anastomosis presented in this research in reducing the incidence of cervical anastomotic leak after performing totally minimally invasive esophagectomy (TMIE).

METHODS

The esophagus and stomach of 27 fresh pigs, termed the esophagogastric model, were used to simulate human esophagogastric organs for this study's in vitro experimental objectives. Nine esophagogastric models of similar weight were divided into three groups. Esophagogastrostomy with circular-stapled end-to-side anastomosis was performed. A tension gauge was used to pull the anastomosis, and the tension at which anastomotic leakage occurred was recorded. Furthermore, a retrospective assessment of 539 patients who underwent TMIE was conducted to analyze the influencing factors of cervical anastomotic leakage.

RESULTS

Experiments on the esophagogastric models showed a higher fracture strength of oblique conformal anastomosis than that of conventional anastomosis (F2,18 = 40.86, P < 0.05), which was associated with a lower incidence of cervical anastomotic leakage (X2 = 9.0260, P = 0.0027). Retrospective analysis of 539 esophageal cancer patients who underwent TMIE showed that in contrast to conventional anastomosis, oblique conformal anastomosis was an independent protective factor against cervical anastomotic leakage (P = 0.0462, OR = 0.5872, 95% CI = 0.3497-0.9993).

CONCLUSION

Oblique conformation anastomosis was stronger and involved a more prominent reduced risk of cervical anastomotic leakage than conventional anastomosis after TMIE.

Analysis of gap length as a predictor of surgical outcomes in esophageal atresia with distal fistula: a single center experience

PURPOSE

Long-gap esophageal atresia (LGEA) is still a challenge for pediatric surgery. No consensus exists as to what constitutes a long gap, and few studies have investigated the maximum gap length safely repairable by primary anastomosis. Based on surgical outcomes at a single institution, we aimed to determine the gap length in LGEA with a high risk of complications.

METHODS

The medical records of 51, consecutive patients with esophageal atresia (EA) with primary repair in the early neonatal period between 2001 and 2021 were retrospectively reviewed. Three, major complications were found in the surgical outcomes: (1) anastomotic leakage, (2) esophageal stricture requiring dilatation, and (3) GERD requiring fundoplication. The predictive power of the postsurgical complications was assessed using receiver operating characteristic analysis, and the area under the curve (AUC) and the cutoff value with a specificity of > 90% were calculated.

RESULTS

Sixteen patients (31.4%) experienced a complication. The AUC of gap length was0.90 (p < 0.001), and the gap length cutoff value was ≥ 2.0 cm for predicting any complication (sensitivity: 62.5%, specificity: 91.4%).

CONCLUSION

A gap length ≥ 2.0 cm was considered as defining LGEA and was associated with an extremely high complication rate after primary repair.

Comparing Aachen Minipigs and Pietrain Piglets as Models of Experimental Pediatric Urology to Human Reference Data

INTRODUCTION

Swine had special roles in the development of minimally invasive procedures to treat vesicoureteral reflux, and minipigs have been gaining ground in recent years in experimental pediatric urology as they combine small size with less vulnerable adult physiology, but their suitability as a model has never been assessed. We therefore compared a landrace piglet with a juvenile minipig to elucidate comparability.

METHODS

We evaluated five 3-week old Pietrain piglets and five 3-month old Aachen Minipigs as representatives of landrace and minipig models based on their expected bodyweight being similar to a newborn human. We compared renal weight, volume - via the ellipsoid formula - and ureteral length. In addition, we calculated porcine renal function via Gasthuys' formula. In order to compare the groups with previously published values for infants, we used resampling techniques to allow comparison to humans.

RESULTS

Renal weight was higher in humans than in Pietrain piglets (ΔL = 7.6 g; ΔR = 5.4 g) and Aachen Minipigs (ΔL = 11 g; ΔR = 9.4 g). Renal volumes in humans were higher than in both Pietrain piglets (ΔL = 5.6 mL, p < 0.001; ΔR = 3.7 mL, p = 0.004) and Aachen Minipigs (ΔL = 8.1 mL; ΔR = 6.6 mL; both p < 0.001). Ureteral lengths in humans and both pig breeds were comparable as were estimated renal functions between both pig breeds.

DISCUSSION AND CONCLUSION

Both landrace piglets and juvenile minipigs are suitable models for experimental pediatric urology as parameters did not differ between them. In addition, the anatomic parameters are comparable or smaller than in infants. This might facilitate translational research as technical failure is less likely in larger organs. Additional research is necessary to cover higher age ranges than those included in the present pilot study.

Using simple interrupted suture anastomoses may impair translatability of experimental rodent oesophageal surgery

Background/purpose: Irreproducibility and missing translatability are major drawbacks in experimental animal studies. Hand-sewn anastomoses in oesophageal surgery are usually continuous, whereas those in experimental oesophageal surgery are widely performed using the simple interrupted technique. It has been implicated to be inferior in tolerating anastomotic tension, which we aimed to test in rats due to their importance as an animal model in oesophageal surgery.Methods: We determined linear breaking strengths for the native oesophagus (n = 10), the simple interrupted suture anastomosis (n = 11), and the simple stitch (n = 9) in 8-week old Sprague-Dawley rats. Experiments were powered to a margin of error of 10% around the results of exploratory investigations. The comparison of anastomotic resilience between native organ and simple interrupted suture anastomosis was a priori powered to 99%.Results: Native oesophagi sustained traction forces of 4.25 N (95% CI: 4.03-4.58 N), but the simple interrupted suture anastomosis had only 38.6% (Δ= -2.78 N, 95% CI: -2.46 to -3.11 N, p < .0001) of the resilience of native oesophagi.Conclusions: Oesophageal division and re-anastomosis markedly decreases resilience to traction forces compared to the native organ. This effect is even more pronounced in rats compared to other species and might impair transferability of results.

Using multidimensional scaling in model choice for congenital oesophageal atresia: similarity analysis of human autopsy organ weights with those from a comparative assessment of Aachen Minipig and Pietrain piglets

Swine models had been popular in paediatric oesophageal surgery in the past. Although being largely replaced by rodent models, swine experienced a revival with the establishment of minipig models. However, none of them has ever been investigated for similarity to humans. We conducted a pilot study to determine whether three-week old Pietrain piglets and three-month old Aachen Minipigs are suitable for experimental paediatric oesophageal atresia surgery. We tested the operation's feasibility, performed a necropsy, weighed organs, measured organ length and calculated relative weights and lengths, and measured laboratory parameters. We used multidimensional scaling to assess the similarity of the swine breeds with previously published human data. Pietrain piglets had a higher a priori bodyweight than Aachen Minipigs (Δ = 1.31 kg, 95% confidence interval (CI): 0.37-2.23, p = 0.015), while snout-to-tail length was similar. Pietrain piglets had higher absolute and relative oesophageal lengths (Δ = 5.43 cm, 95% CI: 2.2-8.6; p = 0.0062, q1* = 0.0083 and Δ = 11.4%, 95% CI: 5.1-17.6; p = 0.0025, q3* = 0.0053). Likewise, absolute and relative small intestinal lengths were higher in Pietrains, but all other parameters did not differ, with the exception of minor differences in laboratory parameters. Multidimensional scaling revealed three-week old Pietrain piglets to be similar to two-month old humans based on their thoracoabdominal organ weights. This result indicates three-week old Pietrain piglets are a suitable model of paediatric oesophageal atresia surgery, because clinically many procedures are performed at around eight weeks age. Three-month old Aachen Minipigs were more dissimilar to eight-week old humans than three-week old Pietrain piglets.