Relation between flow-pressure-diameter studies in experimental stenosis of rabbit and human small bowel

Ex vivo and in vivo evaluation of a modified interrupted Lembert pattern for small intestinal anastomoses in horses

OBJECTIVE

To compare single-layer anastomoses (modified continuous Lembert [mod-CL] and modified-interrupted Lembert [mod-IL]) and a 2-layer simple continuous anastomosis (2 L; seromuscular and mucosal) for jejunojejunal anastomoses in equine cadavers and to compare ex vivo to in vivo time to complete the anastomosis and stoma size with a mod-IL pattern.

STUDY DESIGN

Measurements in jejunum from cadaver and anesthetized horses.

ANIMALS

Ten live horses and 18 equine cadavers.

METHODS

Time to complete anastomosis, bursting pressures (BP), leakage sites, and anastomotic index (size ratio of anastomotic lumen to control lumen) were recorded. Time to completion and lumen size were compared between in vivo and ex vivo mod-IL patterns.

RESULTS

The mod-CL pattern was fastest (8.44 ± 1.30 min, p < .05), and the 2 L pattern was slower (17.07 ± 2.0 min) than the mod-CL and mod-IL (p < .05). The anastomotic index exceeded 100 and did not differ between patterns. Segments reached higher bursting pressures when anastomosed with mod-IL (145.94 ± 24.18 mm Hg) than mod-CL (p < .05). In vivo closure was approximately 8 minutes slower than ex vivo, and with a smaller anastomotic index.

CONCLUSIONS

All anastomoses increased lumen size over control segments ex vivo. Lumen size after placement of a mod-IL was greater ex vivo than in vivo, and completion was slower in vivo than ex vivo. [Corrections added on 26 Dec 2022, after online publication: added "ex vivo" to the first line of Conclusions in the Abstract.] CLINICAL SIGNIFICANCE: Slower and smaller anastomoses should be anticipated in vivo compared to ex vivo results. Anastomoses with a mod-IL pattern appear clinically advantageous, producing a comparable lumen size in less time than 2 L.

A novel animal model of colonic stenosis to aid the development of new stents for colon strictures

BACKGROUND

The incidence of colonic stenosis, primarily caused by colon cancer and Crohn's disease, is increasing each year. The development of safer stents for colonic stenosis is required because perforation associated with cancer stent placement worsens the prognosis and stent placement for anastomotic stenosis due to Crohn's disease or colectomy is not first choice due to the high migration rate. The wall of the large intestine where the stent is inserted receives the complex forces from the peristaltic movement of the large intestine and stool in addition to the reaction tension of the stent, causing perforation and migration. Animal models may help develop new and safe stents, but no animal model closely reproduces the condition of human colonic stenosis. Herein, we present a novel animal model of colonic stenosis, which closely replicates the human colonic size.

METHODS

The artificial colonic stenosis model was developed by wrapping the porcine colon with a silicone sheet after laparotomy. The usefulness of the model was evaluated by investigating the availability of endoscopic stent placement, morphological maintenance of colonic stenosis, adverse effects on pigs, and modeling time. The first three and the last three modeling times were analyzed using Student's t-test.

RESULTS

Endoscopic stent placement was performed in all cases without intraoperative complications. There were no postoperative model complications or deaths. Adhesions to the surrounding tissue in the abdominal cavity of the artificial colon stenosis were slight. The morphology of the isolated artificial stenoses was completely maintained, and no necrosis or perforation was observed.

CONCLUSIONS

We developed a novel and feasible animal model of colonic stenosis using pigs. We believe that this animal model will be useful for developing a safer stent for obstruction caused by benign diseases and colon cancer.

Supervised autonomous robotic soft tissue surgery

The current paradigm of robot-assisted surgeries (RASs) depends entirely on an individual surgeon's manual capability. Autonomous robotic surgery-removing the surgeon's hands-promises enhanced efficacy, safety, and improved access to optimized surgical techniques. Surgeries involving soft tissue have not been performed autonomously because of technological limitations, including lack of vision systems that can distinguish and track the target tissues in dynamic surgical environments and lack of intelligent algorithms that can execute complex surgical tasks. We demonstrate in vivo supervised autonomous soft tissue surgery in an open surgical setting, enabled by a plenoptic three-dimensional and near-infrared fluorescent (NIRF) imaging system and an autonomous suturing algorithm. Inspired by the best human surgical practices, a computer program generates a plan to complete complex surgical tasks on deformable soft tissue, such as suturing and intestinal anastomosis. We compared metrics of anastomosis-including the consistency of suturing informed by the average suture spacing, the pressure at which the anastomosis leaked, the number of mistakes that required removing the needle from the tissue, completion time, and lumen reduction in intestinal anastomoses-between our supervised autonomous system, manual laparoscopic surgery, and clinically used RAS approaches. Despite dynamic scene changes and tissue movement during surgery, we demonstrate that the outcome of supervised autonomous procedures is superior to surgery performed by expert surgeons and RAS techniques in ex vivo porcine tissues and in living pigs. These results demonstrate the potential for autonomous robots to improve the efficacy, consistency, functional outcome, and accessibility of surgical techniques.

A novel animal model of gastrointestinal obstruction for the development of stent

BACKGROUND

The need for newer gastrointestinal (GI) stents has been continuously raised. Newly developed stents are generally tested for physical properties in vitro and directly introduced to clinical practice because there is no reliable animal model of GI obstruction. The aim of this study was to establish an animal model both that can represent obstruction of the GI tract and be used to develop new stents.

MATERIAL AND METHODS

Surgical obstruction of the descending colon by wrapping with a nonabsorbable synthetic mesh and rubber bands was made in 17 healthy mongrel dogs. Four days later, a covered self-expanding metallic stent was placed for the obstructed segment in each dog under fluoroscopic guidance. Patency and migration of the inserted stents were evaluated clinically on a daily basis and fluoroscopically on a weekly basis. After sacrifice of the dogs, the degree and extent of residual colonic obstruction were assessed fluoroscopically. The specimen of the colonic obstructed segment was examined microscopically.

RESULTS

In all 17 mongrel dogs, segmental obstruction in the descending colon was successfully created and confirmed with fluoroscopic examination using a contrast medium. The percentage of luminal narrowing ranged from 99%-100%. Stent placement was technically successful in all 17 dogs. During the follow-up period, stent migration occurred in 12 dogs and indwelling time of a stent ranged from 0-95 d (mean 29.2 ± 38.8 d). On postmortem pathologic examination, it was found that fibrosis had newly formed outside the colonic longitudinal muscle layer in all dogs.

CONCLUSIONS

Our canine colonic obstruction model is the first animal model that can be feasible for developing a new design of stent and provide in vivo data on complications, particularly stent migration.

Renal artery diameter, renal function and resistant hypertension in patients with low-to-moderate renal artery stenosis

BACKGROUND

Atherosclerotic renovascular disease is associated with resistant hypertension and chronic kidney disease, although the causal relationship is discussed. To date, the role of renal artery diameter on these pathological conditions was not clearly studied. We aimed to identify the association of reference diameter and minimal luminal renal artery diameter with glomerular filtration rate (GFR) and resistant hypertension in a high cardiovascular risk population.

METHODS

In this cross-sectional, single-center study, we enrolled 734 patients who underwent a renal angiography immediately after a coronary angiography indicated for a diagnosis of ischemic heart disease.

RESULTS

Mean age was 64 ± 10 years (men 72%). GFR was 79 ± 22 ml/min per 1.73 m(2). Five hundred and eighteen patients had no luminal narrowing and 216 patients had low-to-moderate luminal narrowing (10-70%, mean 36%). A positive significant association between reference diameter and GFR was detected in patients without luminal narrowing [beta 2.2 ml/min per 1.73 m(2) for 1 mm increase, 95% confidence interval (CI) 0.3-4.0, P < 0.05] and in those with low-to-moderate luminal narrowing (beta 7.7 ml/min per 1.73 m(2) for 1 mm increase, 95% CI 4.2-11.1, P < 0.001). The lowest quartile of reference diameter (<5.2 mm) was associated with GFR less than 60 ml/min per 1.73 m(2) [odds ratio (OR) 3.18, 95% CI 1.61-6.29, P < 0.001]. Patients with resistant hypertension had low minimal diameter and reference diameter. Reference diameter less than 5.2 mm was associated with an increased risk of resistant hypertension (OR 2.63, 95% CI 1.02-6.77, P < 0.05).

CONCLUSIONS

Small renal arteries, defined by a low reference diameter or minimal luminal diameter, are independently associated with low GFR and resistant hypertension, independent of the degree of stenosis and major confounders.

Retrospective study assessing efficacy of treatment of large colonic impactions

Cases with a history of colic due to a large colonic impaction were recruited retrospectively to assess the treatment efficacy and complications of oral and parenteral fluid therapy regimes for correction of primary large colon impactions. Oral isotonic fluids had been administered at varying intervals following initial treatment with magnesium sulphate and water. There was no significant difference in complication rates between groups. Considering complication rates with impaction clearance, hourly administration of oral fluids appears to be the most appropriate treatment regime of those investigated.

Effects of enteral and intravenous fluid therapy, magnesium sulfate, and sodium sulfate on colonic contents and feces in horses

OBJECTIVE

To assess changes in systemic hydration, concentrations of electrolytes in plasma, hydration of colonic contents and feces, and gastrointestinal transit in horses treated with IV fluid therapy or enteral administration of magnesium sulfate (MgSO4), sodium sulfate (NaSO4), water, or a balanced electrolyte solution.

ANIMALS

7 horses with fistulas in the right dorsal colon (RDC).

PROCEDURE

In a crossover design, horses alternately received 1 of 6 treatments: no treatment (control); IV fluid therapy with lactated Ringer's solution; or enteral administration of MgSO4, Na2SO4, water, or a balanced electrolyte solution via nasogastric intubation. Physical examinations were performed and samples of blood, RDC contents, and feces were collected every 6 hours during the 48 hour-observation period. Horses were muzzled for the initial 24 hours but had access to water ad libitum. Horses had access to hay, salt, and water ad libitum for the last 24 hours.

RESULTS

Enteral administration of a balanced electrolyte solution and Na2SO4 were the best treatments for promoting hydration of RDC contents, followed by water. Sodium sulfate was the best treatment for promoting fecal hydration, followed by MgSO4 and the balanced electrolyte solution. Sodium sulfate caused hypocalcemia and hypernatremia, and water caused hyponatremia.

CONCLUSIONS AND CLINICAL RELEVANCE

Enteral administration of a balanced electrolyte solution promoted hydration of RDC contents and may be useful in horses with large colon impactions. Enteral administration of either Na2SO4 or water may promote hydration of RDC contents but can cause severe electrolyte imbalances.

Effects of feeding large amounts of grain on colonic contents and feces in horses

OBJECTIVE

To assess changes in systemic hydration, concentrations of plasma electrolytes, hydration and physical properties of colonic contents and feces, and gastrointestinal transit in horses with access to large amounts of grain.

ANIMALS

6 horses with right dorsal colon (RDC) fistulas.

PROCEDURE

In a crossover design, horses were alternately fed 1 of 3 diets: orchard grass hay ad libitum after being adapted to this diet for at least 5 days, orchard grass hay ad libitum and 4.55 kg of grain offered every 12 hours after being adapted to orchard grass hay ad libitum for at least 5 days, or orchard grass hay ad libitum and 4.55 kg of grain offered every 12 hours after being adapted to this diet for at least 5 days. Physical examinations were performed and samples of blood, colonic contents, and feces were collected every 6 hours during a 48-hour observation period.

RESULTS

Grain ingestion had several effects, including changes in the concentrations of electrolytes in plasma; RDC contents became more homogenous, dehydrated, foamy, and less dense; RDC contents flowed spontaneously when the cannula was opened; RDC contents expanded when heated in an oven; and feces became fetid and less formed. Horses did not have any clinical signs of colic, endotoxemia, or laminitis.

CONCLUSIONS AND CLINICAL RELEVANCE

Changes observed in the colonic contents and feces may be explained by the large amounts of hydrolyzable carbohydrates provided by grain. Access to large amounts of grain may increase the risk of tympany and displacement of the large intestine.

Treatments to promote colonic hydration: enteral fluid therapy versus intravenous fluid therapy and magnesium sulphate

Although large intestine impactions are commonly treated with i.v. fluids combined with the osmotic laxative MgSO4, enteral fluids are less expensive and also appear to be efficacious for impactions. Therefore, this study was conducted to compare the systemic and gastrointestinal effects of enteral fluids with the changes produced by i.v. fluids combined with MgSO4. Four horses with a fistula in the right dorsal colon alternately received both treatments in 2 periods one week apart. Sixty litres of fluids were administered continuously (10 l/h) through a venous catheter or a nasogastric tube. Magnesium sulphate (1 g/kg bwt) was administered via nasogastric tube before i.v. fluid therapy. Two horses had mild abdominal discomfort at the end of enteral fluid therapy. Pollakiuria, hypostenuria, increased bodyweight, increased faecal and ingesta hydration, and decreased PCV, plasma protein and plasma magnesium were produced by both treatments. Abdominal distention and more pronounced changes in bodyweight and ingesta hydration were seen with enteral fluids. Intravenous fluids plus MgSO4 produced hypocalcaemia and more pronounced changes in plasma protein. These results indicate that enteral fluid therapy is more effective in promoting ingesta hydration and produces less pronounced systemic effects than i.v. fluid therapy plus MgSO4.

Importance of endoscopically visualized recurrent ileitis and small-bowel resection for symptoms in Crohn's disease

BACKGROUND

The relationship between the endoscopic appearance of the ileal mucosa in Crohn's disease and the symptoms has not been studied. Although surgery is important, morbidity caused by intestinal resections and its relation to recurrent inflammation have been poorly evaluated.

METHODS

The relationship of symptoms to various ileoscopic signs of inflammation and previous intestinal resection was prospectively studied in 75 postresection Crohn patients.

RESULTS

Multivariate analysis showed that a combination of anastomotic width, pus, and length of previous small-bowel resection best explained a symptom score (r = 0.53, p < 0.001). Of 40 patients with the anastomosis strictured to less than 15 mm, only 9 had moderate to severe symptoms. Patients with a stricture diameter < 10 mm differed significantly in symptom score (p < 0.05) from those with wider anastomoses.

CONCLUSIONS

The study indicated that intestinal resection was as important for symptoms as endoscopically viewed recurrent ileal inflammation. The diameter at which an intestinal stricture produces symptoms is less than previously argued, and the association of small-bowel resection with symptoms underlines the advisability of minimal surgery.

Crohn's disease and anastomotic recurrence: microvascular ischaemia and anastomotic healing in an animal model

Microvascular injury and ischaemia may be factors in anastomotic recurrence after resection for Crohn's disease. This hypothesis was explored in a ferret model of multifocal intestinal infarction. At laparotomy, isolated loops of small intestine were injected intraarterially with styrene microspheres (test loop) or saline (control). At a second laparotomy 72 h later, test and control loops were divided and an end-to-end anastomosis performed between test loops (n = 2), test and control loops (n = 9) or control loops (n = 2). Abnormalities including chronic transmural inflammation, ulceration and granuloma formation were identified 2 weeks after the second operation in ten of the 11 surviving animals; changes were confined to the test loops and were more prominent adjacent to the anastomosis. No abnormalities were seen in control loops. The combination of two self-limiting ischaemic insults can produce a pattern of intestinal inflammation similar to that seen in anastomotic recurrence in Crohn's disease.