Pyloric Stenosis

Welcome to the latest episode of Stay Current in Pediatric Surgery, a multimedia publication designed to spread the latest knowledge freely. This chapter is created and edited by Todd Ponsky, Ray Hankey, Zach Corp, and myself, Rod Gerardo. Do you get a pit in your stomach every time you study pyloric stenosis? Well then, join us as we break down this complex subject with Jillian Goddard and Bhargava Mulapudi. Hi, I'm Bhargava Mulapudi, a pediatric surgeon at Cincinnati Children's Hospital. And today, we're going to review pyloric stenosis. Pyloric stenosis, an acquired gastric outlet obstruction found in infants, can be fatal if left untreated. Today, we're going to review the basics of pyloric stenosis with the help of Dr. Bhargava Mulapudi, pediatric surgeon at Cincinnati Children's, and Jillian Goddard, pediatric surgery research fellow at Cincinnati Children's. What is pyloric stenosis? Pyloric stenosis is hypertrophy and hyperplasia of the inner circular layer with associated mucosal hypertrophy. It leads to gastric outlet obstruction in infants between two to ten weeks of age. It is not a congenital anomaly, but may have genetic predisposition that could be influenced by environmental factors. What causes pyloric stenosis? The etiology is likely multifactorial. There is a proposed role of nitric oxide synthase where the absence in the circular muscle layer results in extended periods of pylorospasm and eventually hypertrophic pyloric stenosis. As we know, nitric oxide synthase is an enzyme involved in the production of nitric oxide, which is a known smooth muscle relaxer. Are there any particular risk factors? There are several studies out there that have attempted to answer this question. Mostly, they're multifactorial. There is some associations between maternal pregnancy and perinatal risk factors. How often does it occur? The prevalence is noted to be around one to four children per 1000 live births in Caucasians. And the condition is less prevalent in other races. It's more common in males and the male to female ratio is somewhere between two to one to five to one. There is increased risk for firstborn infants with a positive family history. A child is more likely to have hypertrophic pyloric stenosis if his or her mother had it. However, it does not follow normal genetic patterns. How do these infants present? Patients with pyloric stenosis typically present with nonbilious vomiting. Usually seen between two to ten weeks of life. Infants are otherwise well-appearing and hungry after vomiting, and emesis will progress until it is projectile. Excessive vomiting can lead to dehydration and eventually lethargy. Time frame between onset of symptoms to hospital presentation is usually one to three weeks. Obviously, longer onset of symptoms worsens dehydration and electrolyte abnormalities. Hyperbilirubinemia can also occur in up to 14% of patients due to down regulation of hepatic enzymes associated with starvation and generally resolves with rehydration, surgery, and reinitiation of oral feeds. What are other differential diagnoses for nonbilious vomiting in an infant? Our differential diagnosis should include gastroesophageal reflux, gastroenteritis, pylorospasm, and other anatomical abnormalities such as duodenal or antral webs, pyloric atresia, duplications. But these tend to present very early after feeding. Bilious emesis should always be worked up to rule out intestinal malrotation with midgut volvulus. How do you diagnose pyloric stenosis? The workup should start with a good history. Onset and duration of symptoms, character and nature of emesis are important. Next, for physical exam, you may find a palpable epigastric mass, known as an olive, but this is more likely to be seen once patient is asleep. In resource poor countries, sometimes milk is given and you can actually see the peristalsis on abdominal exam. Next, laboratory data can be obtained and chemistries to check for electrolyte imbalances with particular attention to bicarb, chloride, and potassium. Next, an ultrasound, which is the gold standard, can be obtained. Usually, the pyloric muscle thickness of 3 millimeters and the length of 15 millimeters or greater is used. Easy way to remember this is remember the value of pi, as 314, 3 millimeters thick and 14 millimeters long, and anything above this is diagnostic. On Star, everything above has already been done by the time we are consulted, but it is important to know. Upper GI used to be the gold standard. And in fact, still obtained in some of the resource poor countries where ultrasound is not available. An elongated pyloric channel and indentation on antral outline is usually seen. Barium must also be seen exiting the stomach to exclude a pyloric web or pyloric atresia. A lot of infants are dehydrated when they present. How can the severity of dehydration be assessed clinically? The most important part during a physical exam is to look for signs of dehydration. A depressed fontanelle, decreased capillary refill, and low urine output are important. Moderate dehydration can present as restlessness and an irritable infant with sunken eyes and fontanels, dry mucus membranes, prolonged capillary refill, cool extremities, skin turgor with less than 2 seconds recoil. A severe dehydration can present as lethargy, tachycardia, weakly palpable pulses, absent tears, mottled or cyanotic extremities. Severely dehydrated and alkalotic infants are at risk of apnea, and some may require intubation due to decreased respiratory drive. Once you diagnose pyloric stenosis, what electrolyte abnormalities are you concerned about? The classic electrolyte abnormality is a hypochloremic, hypokalemic metabolic alkalosis. The mechanism is simple. Prolonged gastric outlet obstruction leads to persistent vomiting and loss of hydrochloric acid, which leads to hypochloremia and loss of protons leading to metabolic alkalosis. Then the kidneys try to compensate for dehydration and they increase the activity of the sodium potassium pump in an attempt to retain fluid. This leads to urinary excretion of potassium to preserve sodium and water. Eventually this leads to hypokalemia, and in later stages, excretion of protons leads to paradoxical aciduria, which further worsens metabolic alkalosis. Activation of aldosterone mediated reabsorption of fluid also worsens these derangements. How is pyloric stenosis treated? First step is to resuscitate to correct volume and electrolyte abnormalities. Definitive treatment is pyloromyotomy. Is there a non-operative option for pyloric stenosis management? Rehydration with frequent small feedings can lead to prolonged hospital stays and is also associated with higher risk of mortality. In the US, pyloromyotomy is the standard of care. In some countries, atropine is used as a non-surgical option with a success rate of about 60 to 90%. If resources are limited, theoretically small frequent feedings can be used to rehydrate the infants and wait several weeks for the hypertrophied muscle to relax. But this is associated with a high risk of mortality. What is the proper way to resuscitate infants with pyloric stenosis? Institutions may have their own protocols involving fluid boluses, increasing maintenance fluid rates and repeating lab draws. At Cincinnati Children's, we follow a protocol published by the Children's Mercy Group in Kansas City that takes the guesswork out of how many boluses to give and how frequently you should draw labs. Could you talk us through that guideline really quickly? Essentially, you first resuscitate based on chloride levels. If chloride is less than 85, give three boluses normal saline with 20 ml per kilo, which are usually separated by an hour and then recheck labs. If chloride is between 85 and 97, give two boluses. If chloride is greater than 97, give one bolus. If chloride is normal, the resuscitation is based on bicarb. If bicarb is greater than 40, give three boluses. If bicarb is greater than or equal to 33, give two boluses. If chloride and bicarb are normal, but potassium is low, give one bolus. The boluses can be followed by one to one and a half times maintenance fluids with dextrose. Check out the full article review summary or a review of the Cincinnati Children's guideline by searching the Stay Current app. Be sure to avoid excessive and aggressive rehydration as this may cause electrolyte shifts and can lead to seizures. Prior to going to the operating room, electrolytes must be corrected. Serum chloride corrected to greater than 100 and most importantly bicarb to less than 30 and ensure adequate urine output. Should a nasogastric tube be placed pre-operatively for continuous emesis? Usually a nasogastric tube is discouraged as it may worsen dehydration and electrolyte derangements. Most institutions temporarily place a nasogastric tube to empty the stomach just prior to induction of general anesthesia. Now that we've resuscitated and brought the patient back to the operating room, what are the key steps of a pyloromyotomy? Either laparoscopic or open, the surgical principle of myotomy is the same. The pyloric channel needs to be held in place so that the incision and spreading is exact. A superficial longitudinal incision is made in the serosa between the proximal and distal end of the pylorus, staying within the edges. This can be done with a pyloromyotomy blade or a bovie. If you want to sound like a superstar in the OR, remember to change the bovie settings to a blend of cut and coag at eight. You need to understand the anatomic landmarks that guide the extent of incision. The proximal edge can be easily identified as the antrum transitions to a thick pylorus. The distal extent is generally to the crossing vein of mayo or the white line. This marks the pyloroduodenal junction. After the incision, you use the pyloric spreader to extend the myotomy down to the submucosa. This should be done gently with multiple spreads. When I was in training, one of my attendings used to say, you want a lot of singles and not a home run. It is important to identify a mucosal perforation right away. It is easier to visualize during open than laparoscopic approaches. It is important to identify a mucosal perforation right away. It is easier to visualize during open than laparoscopic approach. Not everyone does a leak test, but is usually done by insufflating some air into the stomach, although this is not very reliable. How do you know your myotomy is adequate? After the pyloromyotomy is completed, you notice the submucosa bulge into the myotomy site. Each side of the pylorus should move independently. You can also insufflate air through the NG tube and see the mucosa bulge and the air pass into the first part of duodenum. Are outcomes different between laparoscopic and open approaches? Statistically, there is a slight increased risk of incomplete myotomy and perforation with the laparoscopic approach. But the overall low incidence of complications decreases the clinical significance of the differences between the two approaches. What are potential complications from surgery? The complications usually are incomplete myotomy, mucosal perforation, aspiration, wound infection, and incisional hernias. While doing the pylomyotomy, you perforate mucosa. What do you do? Depending on the extent of perforation, you can either close the mucosa, typically using a low profile needle and a suture like a five O vicryl on a TF needle, or you could perform a full thickness repair of the myotomy and redo a myotomy about 180 degrees from the first one, usually on the posterior wall of the pylorus. When this happens, usually a NG tube is left in place for a day or so. And upper GI can also be performed based on surgeon's discretion. When can infants begin feeding after the operation? Most infants can be fed immediately after the operation. Different institutions use different protocols. Evidence supports ad lib feeds once the infant is alert and awake should be a standard of care. These infants achieve full feeds sooner with no increase in readmission rates. Check out the postop management guideline in the Stay Current app. Is there a risk of apnea after pyloromyotomy? Yes, there is concern that alkalosis even after correction may play a role in increased risk of postop apnea. This may be increased with narcotic use. Postoperatively, all these patients should have cardio respiratory monitoring and narcotics should be avoided. Usually, you only need Tylenol for pain management in these patients. An infant continues to have persistent vomiting after surgery. What is your differential diagnosis? Small episodes of emesis are almost to be expected as the stomach recovers from days to weeks of progressive dilation and this should not defer feeding. Studies show that odds of emesis is slightly higher in early and ad lib feedings compared to gradual or delayed feedings. But the length of the stay for ad lib feedings is much shorter and there is no difference in outcomes. However, your differential should also include an incomplete myotomy. This may require a repeat myotomy, but is usually very rare. A leak from mucosal perforation can have other signs such as tachycardia and worsening abdominal tenderness. Esophageal reflux disease can also present as postop emesis. It is important to ask history of reflux prior to developing pyloric stenosis symptoms as they may persist after the surgery from gastric dysmotility from prolonged symptoms. So before we dive into the steps of the operation, how should we be positioning the patient? After general anesthesia and intubation, the patient is usually positioned transversely on the table. A roll should be placed in the mid back at the level of the xyphoid to open the subcostal space. Less ideal is to place the roll too low and then you close the space. For a laparoscopic procedure, how should we be placing our ports? If you're performing the operation laparoscopically, one approach is to insert a 5 millimeter umbilical port for the camera. Then make two working stab incisions, one for the grasper and the other for performing the pyloromyotomy. Usually, the stab incision for the grasper is more lateral, while the incision for pyloromyotomy is more medial to make sure you're able to work perpendicular to the pylorus. So what if we get in there laparoscopically and the edge of the liver is obscuring the pylorus? What do we do? Usually this can happen if the bump behind the patient is too far low. You can check to see and move the bump more behind the xyphoid to open up the space. If that does not work, you can place a transabdominal stitch in the epigastric region, usually a two O vicryl across the falciform ligament to retract the left lobe up and away from the pylorus and tie it over a folded ratec for cushion. Now that you worked through pyloric stenosis, what would you say are your key takeaways from today? Be sure to understand the typical presentation of these patients with progressively worsening nonbilious emesis, persistent hunger and increasing dehydration. Know their typical physiologic derangement of hypochloremic, hypokalemic metabolic alkalosis. And finally, understand the main stay of treatment. First with appropriate resuscitation and second, a pyloromyotomy along the length of the hypertrophied pylorus. This is Rod Gerardo from Cincinnati Children's Hospital, the contributing editor for this audio chapter. What else do you want to hear? Let us know in the Stay Current app, Twitter, Facebook, or Instagram pages. And remember, knowledge should be free.