CHAPTER 26 Laparoscopic and Open Pyloromyotomy
Step 1: Surgical Anatomy
♦ The pylorus is identified as a smooth muscle mass that normally measures 1 to 1.5 cm in diameter and 2 to 2.5 cm in length. When hypertrophic pyloric stenosis (HPS) is present, the musculature becomes enlarged, measuring up to 4 cm in length and 3 cm in diameter.
♦ As its name implies, in the presence of HPS, the pyloric musculature is hypertrophied without accompanying hyperplasia. There is an obvious demarcation between the distal aspect of the abnormal pylorus musculature and the normal thin-walled duodenum. The hypertrophied pylorus leads to protrusion of the muscle and mucosa into the distal duodenum, and care must be taken to not injure the duodenal mucosa at its transition at the time of pyloromyotomy.
Step 2: Preoperative Considerations
Presentation and Metabolic Abnormalities
♦ Infants with HPS are a remarkably homogeneous population. They are usually between 3 weeks and 3 months of age with a history of at least 2 weeks of nonbilious emesis. The emesis pattern associated with HPS is unique and is an important part of the history. Vomiting is postprandial and projectile, often described as “shooting across the room.” This forceful vomiting is due to the aggressive contractions of the gastric musculature in an attempt to push the gastric contents through the obstructed pylorus. Despite the vomiting, the infant remains hungry and will feed again almost immediately if allowed, only to vomit again. Often the family will have undertaken several changes in formula feeds at the recommendation of the pediatrician or primary care physician after a diagnosis of milk allergy or formula intolerance.
♦ At presentation, the infant can be below his or her birth weight as a result of progressive malnutrition and dehydration. Prolonged emesis results in loss of gastric secretions and severe dehydration, leading to the development of hypokalemic, hypochloremic metabolic alkalosis that can progress to paradoxical aciduria as a result of the renal response to volume contraction and increasing alkalosis. The kidneys attempt to expand intravascular volume, rather than correct the abnormal pH, by absorbing sodium and excreting a hydrogen ion from the hypokalemia. This proton excretion is what leads to the paradoxical aciduria.
Diagnosis
♦ Palpation of the abdomen in an infant with HPS reveals an enlarged pylorus classically described as an “olive” deformity located over the epigastrium. The pylorus is mobile in its superior-inferior direction and is more easily palpated with the stomach empty (after emesis).
♦ A small amount of sugar water on a pacifier or bottle nipple will usually allow several minutes of diminished agitation, thereby allowing a careful and accurate examination. Although this examination is described in what seems to be a straightforward and efficient manner, it is time consuming and difficult to perform by individuals not experienced in the technique. In our experience, nearly all patients routinely have undergone an abdominal ultrasound before surgical consultation, and we strongly feel that in this setting this is a more efficient diagnostic modality compared with a physical examination alone. Generally accepted guidelines for the diagnosis of HPS by ultrasound include a tumor depth of 4 mm and a pyloric channel length of at least 16 mm (Fig. 26-1).
♦ Although we do not recommend their use as a diagnostic modality today, upper gastrointestinal contrast studies have been utilized in the past. When performed in an infant with HPS, the stomach will appear distended and there will be delay in gastric emptying. Gastroesophageal reflux may be detected during this study, which is the result of the gastric outlet obstruction created by the hypertrophied pylorus. An elongated and narrowed line of contrast, classically described as a “string sign,” will identify the hypertrophied pyloric channel.
Preoperative Resuscitation and Preparation
♦ The preoperative resuscitation and preparation of a patient with HPS are paramount to any surgical procedure. As outlined, infants with HPS are usually dehydrated and malnourished and can have severe electrolyte abnormalities (hypokalemia, hypochloremia, and alkalosis).
♦ All patients should be admitted to the hospital and have an intravenous catheter inserted and a basic chemistry profile obtained. Fluid resuscitation should begin with an initial fluid bolus of 10 to 20 mL/kg of normal saline, after which the bolus resuscitation can be determined by the clinical state of the infant (urine output, skin turgor, mucous membranes, normalization of serum electrolytes). Maintenance fluids should be continued at a volume of 1.5 times the hourly maintenance rate of D5 1/2 normal saline. Then 20 meq KCl/L should be added after urine output has been established. Only after patients have been adequately resuscitated and have normal serum electrolytes can they be considered for operative correction. In our institution, we use a serum chloride of greater than 90 mEq/dL and a serum bicarbonate of less than 30 mEq/dL as safe electrolyte levels for general anesthesia in HPS patients.
♦ Preoperative anesthetic concerns must also be addressed. Before any progression toward anesthetic induction, the stomach is emptied with several passes of an orogastric tube connected to suction in remove any gastric contents that are retained in the obstructed stomach. Anesthesia is induced in a rapid sequence manner with great care taken to protect the airway from aspiration of gastric contents. Gentle cricoid pressure can be applied to assist in occluding the esophagus, thus decreasing the aspiration risk during the induction and intubation portion of the anesthetic.
Step 3: Operative Steps
Laparoscopic Pyloromyotomy
Positioning and Preparation
♦ After induction of anesthesia, the patient is placed in the supine position on the operation table in a transverse orientation. This position allows both the operating surgeon and the camera operator to stand at the feet of the patient while providing easy access for the anesthesiologist to the patient if necessary (Fig. 26-2). Before beginning the operation, an orogastric red rubber catheter is placed. The abdomen is then prepped and draped in a sterile fashion.
Instrument Placement
♦ A 5-mm cannula is introduced via a Step sheath (Autosuture, Tyco Healthcare, Norwalk, CT) directly into the peritoneal cavity through the umbilicus after spreading the center of the incompletely closed umbilical skin with a hemostat.
♦ The abdomen is then insufflated with CO2. We use a pressure of 12 mm Hg and a flow rate of 3 L/min to prevent overpressurization of the abdomen and possible hemodynamic consequences in these fragile patients.
♦ Under direct visualization, the two operating instruments are inserted into the abdominal cavity via 3-mm stab incisions, one in the right and one in the left upper abdominal quadrant. An atraumatic grasper is inserted into the abdomen through the patient’s right upper quadrant stab incision, and an arthroscopy knife is inserted through the left upper quadrant incision (Fig. 26-3).
Pyloromyotomy Technique
♦ The hypertrophied pylorus is assessed visually and via palpation to confirm the diagnosis of HPS. The duodenum is stabilized with the atraumatic grasper in the surgeon’s left hand by grasping the duodenopyloric junction. With the pylorus secured, the blade of the arthroscopy knife is deployed to 2 mm, and the serosa of the pylorus is incised starting just proximal to the duodenopyloric junction and extending proximally onto the gastric antrum (Fig. 26-4).
♦ The pyloric musculature is initially separated using the shaft of the arthroscopy knife after returning the blade to its closed position to provide enough separation to introduce the pyloric spreader (Fig. 26-5). The muscle is then completely divided using a laparoscopic pyloric spreader until the mucosa is identified (Fig. 26-6). When the pyloromyotomy is completed, the two halves of the pyloromyotomy are grasped and rocked independently to ensure complete division of the pyloric ring. A 2-cm pyloromyotomy has been shown to be an adequate length in order to prevent an incomplete pyloromyotomy.
♦ Having completed the pyloromyotomy, the stomach is insufflated with air through the red rubber catheter, and the mucosa is inspected for evidence of perforation. Once hemostasis is ensured, a tongue of omentum is draped over the myotomy and the abdomen is desufflated. The umbilical fascial defect is closed using 3-0 absorbable suture, and the stab incisions are closed with Steri-strips (Fig. 26-7). Local anesthetic is instilled into the subcutaneous and deep tissue for postoperative pain control, and sterile dressings are applied.
Open Pyloromyotomy
Incisions
♦ For a right upper abdominal approach, a transverse incision is made just to the right of the midline, approximately one third the distance between the xiphoid process and the umbilicus (Fig. 26-8).
♦ The anterior fascia is opened, and the muscles can be either divided in a transverse fashion or spread in a vertical direction. The posterior rectus fascia is then divided and the abdomen entered. An alternative to the right upper quadrant incision is the upper midline incision, where an incision is made in a vertical fashion between the xiphoid and umbilicus and the linea alba is incised to allow entry to the abdominal cavity.
♦ Recently several authors have reported the use of a circumumbilical incision as a cosmetic advantage to the open epigastric or midline incisions. This approach uses an incision made in the superior fold of the umbilicus approximately two thirds to three fourths of the distance around the umbilicus (Fig. 26-9).
Pyloromyotomy Technique
♦ Once the peritoneal cavity has been entered, the omentum can usually be identified and grasped. This will lead the surgeon to the transverse colon and then to the greater curvature of the stomach. By grasping the greater curve of the stomach with a moist sponge and gently rocking the pylorus, the surgeon can deliver the hypertrophied pylorus through the incision for pyloromyotomy.
♦ With any “open approach,” the pyloromyotomy is initiated by incising the serosa of the pylorus from 1 to 2 mm proximal to the duodenopyloric junction (identified by a color change from the white thickened pylorus to the normal duodenum) to well back onto the normal gastric antrum (Fig. 26-10). The outer longitudinal and inner circular muscle fibers of the pylorus are divided using the back of a forceps or knife handle (Fig. 26-11). The remaining muscle fibers lying in close approximation to the pyloric mucosa are divided using a pyloric spreader (Fig. 26-12).
♦ When all the muscle fibers have been divided, the mucosa should pouch outward through the divided muscle incision (Fig. 26-13). Particular attention should be focused on the division of the fibers near the duodenopyloric junction. With overzealous attempts at muscle division in this area, duodenal mucosal perforations can occur.
♦ Now that the muscle has been divided, the two halves of the divided pylorus can be grasped and individually rocked in opposite directions to ensure complete division of the pyloric muscular ring. The pylorus is returned to the abdomen and inspected to ensure hemostasis. The incision is then closed in the standard fashion with absorbable suture.
Step 4: Postoperative Care
Recovery
Feeding Management
♦ Patients begin a weight-controlled, volume feeding schedule 2 hours after completion of the operation, regardless of technique. The infants receive the volume of oral feeds equal to 2 hours of their intravenous maintenance fluid requirements/hour. For example, a 4-kg infant will receive 32 mL of Pedialyte initially every 2 hours. The schedule is advanced sequentially with another feeding of Pedialyte given 2 hours after the first one, followed by two feedings of half-strength formula or breast milk given 2 hours apart, followed by two feedings of full-strength formula or breast milk given 2 hours apart followed by ad libitum breast or bottle feeds or the previously used home feeding regimen.
♦ Infants with two emesis episodes at a given level on the feeding schedule are held at that level until they tolerate that level of feeding. More than two emesis episodes is considered a “setback.” The feeding schedule is halted for 6 hours, followed by subsequent reinstitution of oral intake at the previous level. Use of this feeding regimen has been shown to result in an average discharge from the hospital in approximately 20 hours, regardless of operative technique.
Pain Control
♦ Postoperatively no narcotics are given to patients because of the risk of respiratory depression. Acetaminophen 10 to 15 mg/kg given orally or parenterally has been shown to be effective in controlling the discomfort associated with either approach, with the laparoscopic technique requiring fewer (mean per patient = 1.5 vs. 2.25) doses than the open technique.
Step 5: Pearls and Pitfalls
♦ Assess for the hydration status of the patient at admission and before induction of anesthesia. Failure to rehydrate and correct electrolyte abnormalities can lead to hemodynamic problems and cardiac arrhythmias.
♦ Gently advancing and spreading with a hemostat in the center of the incompletely healed umbilical skin, without making an incision, will allow for insertion of a 5-mm cannula that will fit snugly and not move during the operation.
♦ During a laparoscopic approach, placing the right upper quadrant atraumatic grasper superior to the liver edge will allow the operating surgeon to retract the liver during the operation with the shaft of this instrument.
♦ Identification and retraction on the omentum to gain a secure grasp on the distal aspect of the greater curve of the stomach will allow for gentle manipulation of the pylorus in order to “deliver” it through an open incision for pyloromyotomy.
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