Ectopic jejunal pacemakers after jejunal transection and their relationship to transit

Steatorrhea and hyperoxaluria occur after gastric bypass surgery in obese rats regardless of dietary fat or oxalate

PURPOSE

We determined the effect of dietary fat and oxalate on fecal fat excretion and urine parameters in a rat model of Roux-en-Y gastric bypass surgery.

MATERIALS AND METHODS

Diet induced obese Sprague-Dawley® rats underwent sham surgery as controls (16), or Roux-en-Y gastric bypass surgery (19). After recovery, rats had free access to a normal calcium, high fat (40%) diet with or without 1.5% potassium oxalate for 5 weeks and then a normal (10%) fat diet for 2 weeks. Stool and urine were collected after each period. Fecal fat was determined by gas chromatography and urine metabolites were evaluated by assay spectrophotometry.

RESULTS

Daily fecal fat excretion remained low in controls on either diet. However, Roux-en-Y gastric bypass rats ingested a food quantity similar to that of controls but had eightfold higher fecal fat excretion (p <0.001) and heavier stools (p = 0.02). Compared to controls, gastric bypass rats on the high fat diet with potassium oxalate had a fivefold increase in urine oxalate excretion (p <0.001), while gastric bypass rats without potassium oxalate had a twofold increase in urine calcium (p <0.01). Lowering dietary fat in gastric bypass rats with potassium oxalate led to a 50% decrease in oxalate excretion (p <0.01), a 30% decrease in urine calcium and a 0.3 U increase in urine pH (p <0.001).

CONCLUSIONS

In this Roux-en-Y gastric bypass model high fat feeding resulted in steatorrhea, hyperoxaluria and low urine pH, which were partially reversible by lowering the dietary fat and oxalate content. Roux-en-Y gastric bypass rats on normal fat and no oxalate diets excreted twice as much oxalate as age matched, sham operated controls. Although Roux-en-Y gastric bypass hyperoxaluria appears primarily mediated by gut and diet, secondary causes of oxalogenesis from liver or other mechanisms deserve further exploration.

Bovine pericardium buttress limits recanalization of the uncut Roux-en-Y in a porcine model

In contrast to the traditional Roux-en-Y reconstruction, an uncut Roux-en-Y provides biliopancreatic diversion and may preserve myoelectric continuity. Previous iterations of the uncut Roux have been plagued by recanalization of the uncut staple line in the afferent small bowel. Our aim was to determine if bovine pericardium buttress prevents recanalization of the stapled small bowel partition in a porcine model. Sixteen female pigs ( approximately 30 kg) underwent a side-to-side stapled jejunojejunostomy, 20 cm distal to the ligament of Treitz, with placement of a nondivided stapled partition with a single row of 2.5 mm width staples in the intervening jejunal loop. Nine animals in the experimental group had a bovine pericardium buttressed staple line (5 permanent, 4 absorbable), whereas seven animals in the control group had a nonbuttressed staple line. At 6 or 12 weeks, necropsy was performed and the primary outcome, staple line recanalization, was assessed grossly and histologically. Statistical analysis was performed by means of the chi-square test. There were no major complications and all animals gained weight. Overall, eight of nine bovine pericardium buttressed staple lines were grossly and histologically intact at necropsy, whereas all nonbuttressed uncut staple lines had recanalized completely (P<0.05). At 6 weeks, both permanent (N=4) and absorbable (N=3) buttress preparations prevented recanalization. At 12 weeks the permanent buttress remained closed (N=1), but the absorbable buttress had allowed partial recanalization (N=1). The use of bovine pericardium buttress will prevent small bowel recanalization of uncut small bowel staple lines at early follow-up. Pilot data at intermediate follow-up suggest permanent buttress is more durable than absorbable buttress. These results warrant investigation of bovine pericardium for intestinal applications in humans.

Standard Roux-en-Y gastrojejunostomy vs. "uncut" Roux-en-Y gastrojejunostomy: a matched cohort study

Roux-en-Y gastrojejunostomy is a common method of reconstruction after subtotal gastrectomy. Maintaining myoneural continuity has been proposed to decrease the incidence of Roux stasis syndrome, with an "uncut" Roux-en-Y reconstruction. The aim of our study was to compare the clinical results in patients who have undergone uncut Roux-en-Y gastrojejunostomy with those in patients who have undergone a standard Roux-en-Y gastrojejunostomy. Eleven patients underwent gastrectomy and uncut Roux-en-Y gastrojejunostomy and were compared with a cohort of 14 patients who underwent gastrectomy and standard Roux-en-Y gastrojejunostomy. Patients were contacted and charts were reviewed for Visick grade, early and late morbidity and mortality, and incidence of staple line dehiscence. Early postoperative morbidity was 18% in patients undergoing uncut Roux gastrojejunostomy and 28% in patients undergoing standard Roux reconstruction. There were no early postoperative deaths in either group. In the patients undergoing the uncut Roux procedure, no cases of staple line dehiscence were detected clinically (mean follow-up 9 months, range 1 to 48 months). Visick grade improved following the uncut Roux procedure, but changed little after standard Roux reconstruction. Uncut Roux-en-Y gastrojejunostomy can be performed safely with improvement in symptoms. The uncut Roux procedure may provide an alternative for reconstructive gastric surgery.

The jejunal pouch as a rectal substitute after proctocolectomy

Our hypothesis was that a jejunal pouch used as a rectal substitute after proctocolectomy would slow enteric transit, delay defecation, and decrease stool frequency compared to an ileal pouch so used. Twelve dogs underwent proctocolectomy; six had a jejunal pouch-distal rectal anastomosis and six had an ileal pouch-distal rectal anastomosis. After recovery, postprandial mouth-to-anus transit was slower in jejunal pouch dogs (253 +/- 18 minutes [mean +/- SEM]) than in ileal pouch dogs (112 +/- 7.9 minutes; P <0.05). Moreover, jejunal pouch dogs passed only 4.1 +/- 0.3 stools during the 12 hours after eating, whereas ileal pouch dogs passed 6.3 +/- 0. 9 stools (P <0.05). The mean frequency of proximal ileal pacesetter potentials after feeding was less in jejunal pouch dogs (12 +/- 0.4 cycles/min) than in ileal pouch dogs (16 +/- 0.3 counts/min; P = 0. 01), and jejunal pouches had more action potentials (jejunal = 82% +/- 4.3% of pacesetter potentials had action potentials, ileal = 61% +/- 3.0%; P <0.05). In contrast, gastric emptying and pouch motility, emptying, mucosal integrity, and bacteriologic and histologic properties were similar in the two groups of dogs. We concluded that the jejunal pouch operation slowed enteric transit, delayed defecation, and decreased postprandial stooling compared to the ileal pouch operation.

Surgical treatment of Roux stasis syndrome

We wondered whether the slow gastric emptying of the Roux stasis syndrome could be improved by performing a corrective "uncut" Roux operation. Five dogs had a standard Roux gastrectomy and placement of serosal electrodes on the proximal jejunum and Roux limb. After recovery, baseline myoelectrical and gastric emptying data were collected. The animals then underwent a second operation: take down of the Roux limb, restoration of jejunal continuity, and construction of an "uncut" Roux limb. After the animals recovered, the tests were repeated. The slow frequency of pacesetter potentials (PPs) in the standard Roux limb (mean +/- standard error of the mean 14 +/- 0.4 cpm) was unchanged after the uncut Roux operation (14 +/- 0.5 cpm, P > 0.05). However, a greater percentage of PPs propagated aborally in the uncut Roux limb (81% +/- 4%) than in the standard Roux limb (53% +/- 7%, P <0.05). Nonetheless, gastric emptying of a 250 ml 10% dextrose liquid meal was not speeded by the uncut Roux operation (uncut Roux = 36% +/- 5% emptied by 20 minutes vs. standard Roux = 35% +/- 7%; P >0.05). Bile acid concentrations in gastric aspirates were minimal after both operations (0.7 +/- 0.2 micromol/L vs. 0.6 +/- 0.1 micromol/L; P >0.05). The conclusion was that more PPs propagated in the aborad direction in the uncut Roux limb than in the standard Roux limb, but gastric emptying was not speeded by the uncut Roux operation. Both operations were equally effective in preventing bile reflux into the gastric remnant.

Restoration of myoelectrical propagation across a jejunal transection using microsurgical anastomosis

The aim of this study was to determine whether microsurgical anastomosis can restore propagation of jejunal pacesetter potentials (PPs) across a site of canine jejunal transection and preserve motility and transit in bowel distal to the transection. A complete jejunal transection with exact microsurgical anastomosis was performed in five dogs, while five dogs with intact jejunum and five dogs with complete transection and end-to-end conventional macrosurgical anastomosis were used as controls. Long-term recording electrodes and intraluminal, open-tipped pressure catheters were implanted in all dogs. The mean frequency of PPs decreased distal to the transection in both groups of transected dogs. However, aborad propagation of PPs across the anastomosis occurred episodically by 3 months in each dog that had a microsurgical anastomosis, but never occurred in any dog with a conventional macroanastomosis. Moreover, the motility and transit in bowel distal to the transection were unaltered in the dogs with a microsurgical anastomosis, whereas they decreased in the dogs with a macroanastomosis. The conclusion was that microsurgical anastomosis of transected canine jejunum restored episodic propagation of PPs across the anastomosis, and preserved motility and maintained transit in bowel distal to the anastomosis. The conventional macroanastomosis did none of these.

Proctocolectomy with jejunal pouch-distal rectal anastomosis: an alternative to ileal pouch reconstruction

The aim of this study was to determine whether a jejunal pouch would have a lower resting pressure, be more distensible, and have more interdigestive migrating myoelectric complexes and less fecal bacterial overgrowth than would an ileal pouch after proctocolectomy and pouch-distal rectal anastomosis. In six conscious dogs with a jejunal pouch-distal rectal anastomosis and six with an ileal pouch-distal rectal anastomosis (controls), pouch distensibility and motility were measured using a barostat and perfused pressure-sensitive catheters passed per anum, pouch electrical activity was recorded using chronically implanted electrodes, and the number of bacteria per gram of stool was assessed by culture. Dogs with a jejunal pouch had lower resting pouch pressures, more distensible pouches, faster frequencies of pacesetter potentials in the pouch, more phase 3 intervals of the interdigesive migrating myoelectric complex reaching the pouch, but similar numbers and types of bacteria in their stools compared to the dogs with an ileal pouch. We concluded that jejunal pouches have a lower resting pressure, are more distensible, have more cleansing contractions, but a similar fecal flora compared to ileal pouches. A jejunal pouch has features that make it an attractive alternative to an ileal pouch for pouch-distal rectal or pouch-anal canal anastomosis after proctocolectomy.

Use of an ileal Roux limb to prevent the Roux stasis syndrome

The aim of this study was to determine whether the use of an ileal Roux limb, rather than a jejunal Roux limb, would prevent the Roux stasis syndrome that can occur after Roux gastrectomy. An ileal Roux limb was constructed in eight dogs and anastomosed to the gastric remnant after distal hemigastrectomy. Flow of chyme through the jejunum was preserved via an ileojejunostomy and a jejunoileostomy. Six dogs with distal gastrectomy and a conventional Roux gastrojejunostomy served as a control group. Chronic enteric recording electrodes and intraluminal, open-tipped pressure catheters were implanted in all dogs. After recovery, the electrical activity and motility of the Roux limbs and the rates of gastric emptying of liquids and solids were measured. Dogs with a Roux gastroileostomy had a slower frequency of pacesetter potentials in the Roux limb, a greater Roux motility index, and a faster rate of gastric emptying of liquids and solids than did dogs with a Roux gastrojejunostomy. Stomal ulcers, however, developed in seven of the eight ileal Roux limbs but in none of the jejunal Roux limbs. It was concluded that Roux gastroileostomy does ameliorate the Roux stasis syndrome, but there is a greater risk of stomal ulceration in the limb.