Antireflux Mechanism in Nissen Fundoplication - -An Experimental Study--

Naomi IWAI, Hirofumi KANEDA, Toshiaki TSUTO, Kyozo HASHIMOTO, Jun YANAGIHARA and Susumu MAJIMA

ABSTRACT: The antireflux mechanism of the Nissen fundoplication was investigated in 15 mongrel dogs by esophageal manometry. Nissen fun- doplication increased the lower esophageal resting pressure for 2 weeks after operation; however, by 4 weeks it had decreased to a level which did not differ significantly from the preoperative value. Thus, lower esophageal sphincter (LES) length, unlike LES pressure, was maintained for a long period. These results suggest that restoration of competence at the gastro- esophageal junction after Nissen fundoplication depends on an adequate length of LES as well as increased LES pressure. The gastrin-stimulated LES pressure 1, 2 and 4 weeks after operation was significantly higher than the preoperative stimulation pressure. Therefore, it seems that the anti- reflux mechanism is associated not only with the mechanical aspect of the wrapping but also with creation of a new muscular sphincter substitute that reacts sufficiently to gastrin stimulation.

KEY WORDS: Nissen fundoplication, gastro-esophageal reflux, lower esophageal sphincter

INTRODUCTION

G astro-esophageal reflux, which is often found in patients with hiatal hernia, is pre- vented by the Nissen fundoplication, and it is assumed that tt~e lower esophageal sphinc- ter (LES) and the gastroesophageal angle are the primary factors responsible for the pre- vention of reflux in patients with hiatal hernia. However, the precise nature of the mechanism which prevents the gastroeso- phageal reflux has not been clearly defined.

The purpose of this study was to investi- gate by esophageal manometry, the anti-

First Department of Surgery, Kyoto Prefectural Uni- versity of Medicine, Kyoto, Japan

Reprint requests to : Naomi Iwai, First Department of Surgery, Kyoto Prefectural University of Medicine, Kamigyo-ku, Kyoto 602, Japan

JAPANESE JOURNAL OF SURGERY, VOL. 14, No. 3 pp.

reflux mechanism of the gastro-esophageal junction after Nissen fundoplication. An understanding of this mechanism should pro- vide information which will enhance the success of the Nissen fundoplication, without any complications.

MATERIALS AND METHODS

Fifteen adult mongrel dogs with a body weight of 12 to 16 kg were used in these ex- periments. Nissen fundoplication was per- formed with the dogs under general anes- thesia with sodium pentobarbital 15 mg/kg i.v.

Esophageal manometry was performed before and 20 minutes after the injection of tetragastrin (4 r/kg), under intravenous anes- thesia with pentobarbital. These tests were done preoperatively, intraoperative, and 1,

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Volume 14 Number 3 Nissen fundoplication 259

2, 4, and 8 weeks after the operation. A5 lumen tube was used which had 3 recording orifices; measuring 2 m m in diameter, 2 situated a round the catheter 5 cm from the tip, and the other 10 cm from the tip. After insertion of the catheter into the s tomach it was d rawn at a constant speed (1 ram/see) from the s tomach th rough the LES into the esophagus dur ing continuous perfusion (30 ml/hour) . This appara tus was connected to a t ransducer (Toyo Baldwin Co., Tokyo, Japan) , and the pressure was recorded on a polygraph.

The magni tude of the high pressure zone was taken as the difference between the intragastric pressure and the m a x i m u m pressure observed in the lower esophagus, and the mean value obtained from the 3 dif- ferent orifices was defined as the mean LES pressure. The length of the high pressure zone was also measured in centimeters, and the mean value obtained from the 3 differ- ent orifices was defined as the mean LES length.

Results were expressed as m e a n s • and Student 's t-test was used for statistical analysis. A P-value of less than 0.05 was considered to be significant.

Mean LESP (cmH20~)

60

50

40

30

20

10

tt

Mean LESP (emH20)

7O

60

5O

4O

3O

2O

10

i I I �89 l I preop, intraop. 1 4 8

week weeks weeks weeks after op.

Fig. 1. Serial changes in lower esopha- geal sphincter pressure following Nissen fundoplication. (mean• SE)

RESULTS

Lower esophageal sphincter pressure changes before and after Nissen fundoplication (Fig. 1) The mean preoperat ive LES pressure was

24.6:k3.7 c m H 2 0 , while the mean intra- operative, postrepair LES pressure was 4 5 . 3 i 7 . 2 c m H 2 0 , significantly higher ( p < 0.01) than the preoperat ive value. The mean LES pressure measured 1 week and 2 weeks after operat ion was 4 9 . 8 i 9 . 5 c m H 2 0 and 38.54-6.6 c m H 2 0 , respectively. These values are also significantly higher (p<0 .05) than the preoperative value. At 4 and 8 weeks after the operation, however, the mean LES pressure did not differ significant- ly from the preoperat ive value.

Serial changes in lower esophageal sphincter pressure before and after tetragastrin stimulation (Fig. 2) As shown in Fig. 2, the injection of 4 ~'/kg

of tetragastrin significantly (p<0 .05) raised the LES pressure in dogs, both preoperatively and for 8 weeks postoperatively.

preop 1 2 4 8 weeks weeks weeks weeks

after op. Fig. 2. Serial changes in lower esopha-

geal sphincter pressure before and after tetragastrin stimulation. (mean!SE) [ - - ] , before tetragastrin stimulation (4 ~,/kg); ///////, after stimulation

260 Iwai et al. Jpn. J. Surg. May 1984

Mean LESL (cml

4

I I I I I

preop, intraop. 1 2 4 week weeks weeks weeks

after op.

Fig. 3. Serial changes in lower esopha- geal sphincter length following Nissen fundoplication. (mean~ SE)

The mean LES pressure after tetragastrin stimulation increased from 38.1 • 3.5 c m H 2 0 before the operation to 63.0• c m H 2 0 1 week after operation and to 65.0• c m H 2 0 2 weeks after operation (p<0.005). After 4 weeks the stimulation LES pressure had decreased to 47.44-2.5 cmHzO, but was still significantly higher than the preopera- tive value. However, there was no sig- nificant difference between the preoperative stimulation LES pressure and that 8 weeks after operation.

Lower esophageal sphincter length changes before and after Nissen fundoplication (Fig. 3) Figure 3 shows the serial changes in LES

length before and after Nissen fundopli- cation. Mean LES length before operation was 1.84-0.2 cm. The mean LES length measured intraoperatively and 1 and 2 weeks after operation was 3.64-0.3 cm, 3 .2• cm, and 3.14-0.2 cm, respectively, sig- nificantly longer (p<0.005) than the pre- operative value. The mean LES length 4 and 8 weeks after operation was 2.84-0.2 cm and 2 .7• cm, respectively. The post- operative fall in LES length 4 and 8 weeks after operation was significant. However, the mean LES length was still significantly greater than the preoperative measurement.

Mean LESL (cm)

4

1 preop. 1

weeks after op.

4 weeks weeks weeks

Fig. 4. Serial changes in lower esopha- geal spincter length before and after pentagastrin stimulation. (mean~zSE) I 1, before tetragastrin stimulation (4 T/kg) ; i///////_!, after stimulation

Serial changes in lower esophageal sphincter length before and after tetragastrin stimulation (Fig. 4) As shown in Fig. 4 no significant changes

occurred in LES length before and after tetragastrin stimulation, at any time after operation.

DISCUSSION

The goal of the Nissen fundoplication is not only the repair of any sliding hiatal hernia but also the restoration of competence at the gastro-esophageal junction. Goodall and TemplO showed that the Nissen fun- doplication increases the pressure in the LES and that it increases the high pressure zone in the abdominal cavity, with progress in clinical improvement. However, Noble et al., 2 after long term observation, reported a decline in LES pressure between early and late follow-up examina t ions . Bjerkest et al. 8 have also shown that the LES pressure 6 and 12 months after surgery did not differ significantly from the preoperative value.

Volume 14 Number 3 Nissen fundoplication 261

These clinical reports indicate that the anti- reflux mechanism in the Nissen fundoplica- tion includes not only a high resting LES pressure but other factors as well.

Gastro-esophageal competence after Nissen fundoplication depends on various factors. Esophageal manomet ry in the present experi- ment showed that Nissen fundoplicat ion in- creased the lower esophageal resting pressure for 2 weeks after operation, however by 4 weeks after operation, the LES pressure had decreased to a level not significantly dif- ferent from the preoperat ive value. Thus, the previous clinical reports and the findings of the present s tudy indicate tha t fundoplica- tion creates a high pressure in the lower esophageal sphincter zone, but tha t this high resting LES pressure is not the main con- tributor to the competence of the gastro- esophageal junct ion. Fur thermore , the com- plications of dysphagia or "gas-bloat syn- drome," which often occur after Nissen fundoplication, m a y result from too tight a fundoplication. Therefore, too tight a fun- doplication which markedly increases LES pressure is not necessary in Nissen's pro- cedure. A loose wrap is bet ter for successful antireflux repair wi thout any complications.

With regard to LES length after Nissen fundoplication, the present experimental study showed that 8 weeks after operat ion the LES length was still significantly longer than before surgery. Thus, LES length, unlike LES pressure, was mainta ined for a long period. Therefore, it appears that the anti- reflux function of the Nissen fundoplicat ion is the creation of an adequate length of LES as well as increase in LES pressure. In addition, Skinner 4 advocated a loose wrap not longer than 4 era, minimizing the im- portance of LES length in the prevent ion o f the postfundoplicat ion syndrome.

Gastrin has been shown to increase lower esophageal sphincter pressure in both hu- mans and dogs. 5-8 Accordingly, our ex- periment was designed to ascertain whether or not the competence of the lower esopha- geal sphincter after Nissen fundoplicat ion

was influenced by gastrin stimulation. I t is notewor thy that 4 weeks after operat ion the st imulation LES pressure was still significant- ly higher than the preoperat ive st imulation pressure. Nevertheless, 8 weeks after opera- tion the st imulation LES pressure did not differ significantly from the preoperative value. Bjerkest found a sustained increase in the LES pressure only after gastrin stimu- lation, while the resting LES pressure at 6 and 12 months did not differ significantly from the preoperative value. These results indicate that the antireflux mechanism after Nissen fundoplicat ion is associated not only with the mechanical component of the wrap- ping but also with the creation of a new muscular sphincter substitute tha t reacts adequate ly to gastrin stimulation.

(Received for publicat ion on Dec. 10, 1983)

References

1. Goodall RJR, Temple JG. Effect of Nissen fun- dopllcation on competence of the gastro-eso- phageal junction. Gut 1980; 21: 607-613.

2. Noble HGS, Christie DL, Cahill JL. Follow-up studies on patients undergoing Nissen fundopli- cation utilizing intraoperative manometry. J Pediatr Surg 1982; 17: 490~-93.

3. Bjerkeset T, Nordgard K, Schjonsby H. Effect of Nissen fundoplication operation on the com- petence of the lower esophageal sphincter. Scand J Gastro 1980; 15: 213-217.

4. Skinner DB. Complications of surgery for gastro- esophageal reflux. World J Surg 1977; 1: 485- 492.

5. Lipshutz W, Cohen S. Physiological determinants of lower esophageal sphincter function. Gastro- enterology 1971; 6: 16-24.

6. Jennewein HM, Waldeck F, Siewert R, Weiser F, Thimm R. The interaction of glucagon and pentagastrin on the lower esophageal sphincter in man and dog. Gut 1973; 14." 861-864.

7. Zwick R, Bowes KL, Daniel EE, Sarna SK. Mechanism of action of pentagastrin on the lower esophageal sphincter. J Clin Invest t976; 57- 1644-1651.

8. Okazaki Y. Experimental and clinical studies on the operative treatment of sliding esophageal hiatal hernia. Arch Jap Chirg 1980; 49: 3-36.