Infantile hypertrophic pyloric stenosis (IHPS) is a common condition in the neonates, with an incidence of 1–4 per 1000 live births with a male : female ratio of 4 : 1 1.
The classic surgical treatment for IHPS is the technique described in 1912 by Ramstedt. He described longitudinal splitting of the seromuscular layer of the pylorus without suturing, termed pyloromyotomy. This procedure relieves the constriction and allows normal passage of stomach contents into the duodenum 2.
Laparoscopic pyloromyotomy (LP) was first described by Alain et al. 3. Since then, several studies using laparoscopy as the main line of treatment were published with some technical modifications regarding the instrument used for performing the pyloromyotomy 4. Retractable pyloromyotomy knife, arthrotomy knife, myringotomy knife, ophthalmic knife, monopolar hook diathermy, indigenous knife placed in a laparoscopic needle holder, and laparoscopic pyloric spreader have been used for performing LP by various authors 5–9.
Recently, myringotomy knife was introduced as an alternative device in performing pyloromyotomy in cases of IHPS, since the manufacturing of retractable and arthrotomy knives has been stopped 4.
The aim of this study was to evaluate LP using myringotomy knife (SM69) with regard to its efficacy, feasibility, safety, operative time, rate of conversion, complications, and short-term results.
Patients and methods
The study was approved by the Research Ethics Committee of Tanta Faculty of Medicine (number 30486/8/15) in August 2015. This prospective study was carried out on 20 consecutive patients (16 males and four females) presented to the Pediatric Surgery Unit of Tanta University Hospitals with proved diagnosis of IHPS during the period from October 2015 to September 2016. Preoperative resuscitation consisted of intravenous administration of 10% dextrose in 0.45 normal saline containing 10–30 mEq/L of potassium chloride and the infusion was given at a rate of 150–180 ml/kg/24 h. The aim was to correct serum electrolytes to nearly the normal. A nasogastric tube was inserted for the evacuation of gastric contents and to wash out of excess mucus.
Under general anesthesia with endotracheal intubation the patient was placed in supine cross-table position (Fig. 1). The surgeon stood at the baby’s legs with the assistant on his left side and both facing the monitor at the baby’s head. The first port (5 mm) is inserted at the umbilicus for 5 mm 30° telescope. Insufflation was started at a flow of 0.5 L/min and gradually increased to 1.5–2 L/min at a pressure of 8–10 mmHg. Two other 3 mm working instruments were introduced at the right and left midclavicular lines at the level of the umbilicus, either through ports or in a portless manner (Fig. 2).
After exploration and identification of the pyloric mass, a nontraumatic grasper is passed through the right working port and grasps the duodenum distal to the mass. A similar grasper is passed through the left working port to grasp the stomach proximal to the mass (Fig. 3); in this way, the mass was fixed in place. A 4 mm stab incision is made in the epigastrium directly over the middle of the mass through which the SM69 blade (Swann Morton; Swann Morton Ltd., Sheffield, UK) (Fig. 4), mounted on an SF1 handle (Swann Morton) (Fig. 5), is introduced (Fig. 6). An incision is done through the pyloric mass in an avascular plane starting 2 mm from the prepyloric vein and extending proximally to 0.5–1 cm proximal to the mass into the gastric wall (Fig. 7). The incision was deepened mainly in its middle. The knife is withdrawn and a 3 mm grasper or Maryland is passed and is used to spread the incision until a mucosal bulge is seen (Fig. 8). Spreading is continued both proximally and distally until pyloromyotomy is complete with caution on the duodenal side. Another maneuver for spreading is to hold both sides of the incision with graspers and tear them apart (Fig. 9). The pyloric region was immersed in normal saline and the stomach was inflated with 60 ml air to detect any mucosal perforation. The abdomen was desufflated and wounds were closed.
Oral feeding was started in all cases 6 h after operation and gradually increased according to patient tolerance; at first with distilled water and then with milk either breast feeding or half to full concentration formula milk and patients were discharged after tolerating full oral feeds.
Statistical analysis of the present study was conducted using the SPSS, version 16 (SPSS Inc., Chicago, Illinois, USA) for calculating the mean and SD.
The study included 20 patients over a 12-month period. Sixteen (80%) infants were males and four (20%) infants were females with a mean age at presentation of 7±2.59 weeks. Ultrasonography was done for all cases. It was enough to ensure diagnosis in 85% of cases, whereas an upper gastrointestinal series was needed to confirm the diagnosis in 15% of cases. The mean weight at presentation was 2.85±0.51 kg (range: 2.25–3.3 kg). The mean duration of vomiting before operative intervention was 24.60±18.34 days, with a range from 6 to 43 days. The pyloric tumor was palpable in 50% of patients at preoperative examination, but was felt in all cases under general anesthesia at the right upper quadrant. The mean K+ levels were 3.56±0.74 with a range from 2.82 to 4.3 mEq/l. Eighteen (90%) cases had metabolic alkalosis, whereas one (5%) case had combined respiratory and metabolic alkalosis and one (5%) case had metabolic acidosis. The mean preoperative measurement of pyloric muscle thickness was 7.13±2.5 mm, with a range of 4.7 to 9.6 mm. and that of pyloric canal length was 21.45±3.09 mm, with a range from 18.36 to 24.54 mm. Two cases had associated congenital inguinal hernia, unilateral in one case and bilateral in the other case (Table 1).
The mean operative time was 35.55±16.52 min with a range of 20–60 min. No bleeding, mucosal perforation, or incomplete pyloromyotomy occurred. Three (15%) cases had superficial gastric and duodenal serosal injuries. One (5%) case was converted to open surgery by a right upper transverse incision because of the inability to complete the procedure laparoscopically. This occurred during our early experience with the technique in the first case. The mean length of pyloromyotomy was 2.2±0.22 cm (Table 2).
The mean time to reach full oral feeding was 28±10.44 h. Six cases tolerated full oral intake within 18 h, eight cases within 24 h and four cases within 48 h. Postoperative vomiting persisted in one case with the residual coming from nasogastric tube still being nonbilious. Upper gastrointestinal follow through showed gastric outlet obstruction and open exploration showed an associated pyloric antral diaphragm. One (5%) case developed port-site hernia in the 5-mm epigastric incision and resolved spontaneously after 2 months of follow-up. One (5%) case died on the third postoperative day in the incubator, from an unrelated cause most probably due to aspiration. The mean postoperative hospital stay was 48 h (Table 3).
There are multiple techniques for performing LP, including using retractable pyloromyotomy knife, arthrotomy knife, Bovie blade, hook electrocautery, and ophthalmic knife 5–9.
We used the SM69 (Swann Morton) blade mounted on an SF1 (Swann Morton) handle in performing pyloromyotomy. We directly introduced it through an epigastric incision just above the pyloric mass perpendicular to the anterior abdominal wall. This makes the knife perpendicular to the mass during cutting which is a safe cutting angle similar to that used in the open technique. This helped easier handling to incise the seromuscular layer of the mass and easier cutting both proximally and distally. The handle is rounded and almost the size of the shaft of a 4 mm laparoscopic instrument. The SM69 blade that we used in this study has a rounded end that is sharp on both sides, which enables us to work both ways without the need to rotate the knife. The rounded sharp end of the knife has no sharp points, which decreases the incidence of mucosal perforation.
Abu-Kishk and colleagues have used a miniature myringotomy knife and stated that it is a fine instrument designed to provide improved precision and control in delicate, pediatric myringotomy procedures. However, this instrument requires extensive experience in laparoscopic surgery because of the absence of a guard or sheath, which would allow the surgeon to safely control the depth of the cut. However, he also stated that the myringotomy knife has a 3-mm cutting edge while the thickness of the pyloric wall, in pyloric stenosis, is 4 mm or more which minimizes the possibility of mucosal injury 4. He used the knife to make only the superficial cut and we used the same technique.
Parelkar and colleagues in India used a 3-mm hook with low power monopolar electrocautery as an alternative to the pyloromyotomy knife. This technique was effective and resulted in a bloodless operative field, thus facilitating complete spreading of the pyloric muscle by a Maryland dissector. Judicious use of an insulated hook minimizes the risk of mucosal perforation 5,7.
Harris and Cywes 10 presented a simple technique and used an extended tip cautery and two reusable, laparoscopic pyloric spreaders. Thomas and colleagues, compared using the Bovie blade along with the arthrotomy knife for performing the pyloromyotomy. The latter was used as an alternative to the arthrotomy knife after it became unavailable in 2010. The advantage of the Bovie blade is a tip that is sharp enough to enter the muscle but not as sharp as a blade 11.
Ostlie et al. 12 and Bufo et al.  have used an arthroscopy knife and a pyloric spreader for pyloromyotomy. Rothenburg used the slice and pull technique for LP using a laparoscopic Babcock clamp and and a 3-mm serrated sheathed arthroscopy knife 6. Anwar et al.8, described using an ophthalmic knife for performing the pyloromyotomy complemented with a Benson spreader.
In our technique, we used four ports: umbilical for camera, two midclavicular ports (right and left) as working ports, and the fourth epigastric for knife introduction. Fixation of the mass is crucial in LP. The use of four ports has the advantages of better fixation of the pyloric tumor. This fixation provides a steady pylorus which facilitates incising and spreading the pyloric muscle.
The maneuver, we used in our technique, of grasping every pyloric muscle side, after splitting and mucosal bulge, and tearing them apart to complete the pyloromyotomy is a practical way especially in the absence of a LP spreader. The maneuver is done first toward the stomach then toward the duodenum with the wound full open and under complete vision.
In our study, the mean operative time was 35.55 min (range: 20–60 min). In different studies, the mean operative time ranged from 25 to 40 min 7,9,12,13 in the study by Rothenberg  and in the study by Turial et al. 14 study it was 13 min and it was 50 min in the study by Leclair et al. 15. Longer time in our study was reported in initial cases and became as low as 20 min with improving experience.
In our work, we have no cases with incomplete pyloromyotomy. The tips we used for avoiding this complication are: a minimum pyloromyotomy length of 2 cm and carrying the pyloromyotomy for 0.5–1 cm beyond the mass on the gastric side. The latter step can be confirmed by the visual appreciation of muscle thickness where the thick pyloric muscle tapers to the normal gastric wall muscle.
The incidence of incomplete pyloromyotomy in different studies is variable, it ranges from 1.1–8.3% 15–17, whereas others reported a 0% incidence of incomplete pyloromyotomy 7,12,14.
In our study, we have no cases with mucosal perforation. Some surgeons reported no mucosal perforation in LP 7,14. In other published studies the perforation rate, which includes both duodenal and gastric injuries, has ranges of 0.4–10% 12,15,16,18. With loss of tactile advantage in LP, tips to minimize perforation include starting the incision 2 mm from the prepyloric vein, deepening the incision at its middle (thickest) part, and completing the duodenal side last with fully open wound and good visualization.
In our work, three (15%) cases had superficial gastroduodenal injuries, one in the form of duodenal serosal tear, one case had a duodenal hematoma and one case had a small gastric hematoma. These injuries were due to manipulations by laparoscopic graspers and had no ominous consequences. Yagmurlu and colleagues stated that, duodenal injury as a result of the use of the laparoscopic grasper is an injury unique to the laparoscopic technique. These injuries occurred when the duodenum slipped from the grasper 2. Incidences in the literature range from 0 7,12,14 to 2–5% 15,16.
In our work, only one (5%) case was converted to open technique through RUQ incision. It was the first case in our case series, in the early learning curve of LP. This was because of the inability to adequately stabilize the pylorus and inability to complete the pyloromyotomy laparoscopically. The rate of conversion in different studies ranges from 6 to 12.5% 5,15,16. In other studies it is 0% 7,12,14. Reported causes of conversion include, technical difficulties, suspected mucosal perforation, adhesions, an enlarged left liver lobe 17,19.
LP using the myringotomy knife SM69 (Swann Morton) is safe and feasible. The knife makes the incision with easiness. Fixation of the mass is essential for effecting LP. With sufficient training, the operative skills become better and the operative time becomes less. Besides, meticulous work and following proper rules can lessen complications such as perforation and incomplete pyloromyotomy.
The authors thank Mr Sean Marven, Consultant Pediatric Surgeon at Sheffield Children’s Hospital, UK, for inspiring and demonstrating the idea and the technique.
Conflicts of interest
There are no conflicts of interest.
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