Hypertrophic Pyloric Stenosis

Hypertrophic pyloric stenosis is hypertrophy and hyperplasia of the pyloric sphincter muscle. The condition is the most common cause of gastrointestinal obstruction in infants. Affected newborns typically present after the third to fifth week of life with progressive non-bilious vomiting and a firm, olive-like mass in the epigastrium. Ultrasound confirms the diagnosis based on the thickness and length of the pyloric muscle and channel diameter. Initial treatment consists of fluid resuscitation with correction of electrolyte imbalances, followed by either open or laparoscopic pyloromyotomy.

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Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

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Overview

Definition

Hypertrophic pyloric stenosis is a functional obstruction of the gastric outlet caused by hypertrophy and hyperplasia of both the circular and longitudinal layers of the pylorus in infants.

Hypertrophic pyloric stenosis

Hypertrophic pyloric stenosis

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Epidemiology

  • The most common cause of intestinal obstruction in infants
  • Occurs in 13 in 1,000 infants in the United States
  • More common in whites, males, firstborns, blood groups B or O, and those with a positive history of pyloric stenosis in mother or father

Etiology

  • Associations include eosinophilic gastroenteritis Gastroenteritis Gastroenteritis is inflammation of the stomach and intestines, commonly caused by infections from bacteria, viruses, or parasites. Transmission may be foodborne, fecal-oral, or through animal contact. Common clinical features include abdominal pain, diarrhea, vomiting, fever, and dehydration. Gastroenteritis, Apert syndrome, Zellweger syndrome Zellweger syndrome Zellweger syndrome (ZWS), also called cerebrohepatorenal syndrome, is a rare congenital peroxisome biosynthesis disorder and is considered an inborn error of metabolism. Zellweger syndrome is the most severe form of a spectrum of conditions called Zellweger spectrum disorder (ZSD), and is characterized by the reduction or absence of functional peroxisomes. Zellweger Syndrome, trisomy 18 Trisomy 18 Edwards syndrome, or trisomy 18, is a genetic syndrome caused by the presence of an extra chromosome 18. The extra chromosome is either from 3 full copies of chromosome 18 or an additional segment of chromosome 18. As the 2nd most common trisomy, Edwards syndrome is seen in 1 out of every 5,500 live births. Edwards Syndrome (Trisomy 18), use of erythromycin in first 2 weeks of pregnancy Pregnancy Pregnancy is the time period between fertilization of an oocyte and delivery of a fetus approximately 9 months later. The 1st sign of pregnancy is typically a missed menstrual period, after which, pregnancy should be confirmed clinically based on a positive β-hCG test (typically a qualitative urine test) and pelvic ultrasound. Pregnancy: Diagnosis, Maternal Physiology, and Routine Care, and maternal macrolide use during pregnancy Pregnancy Pregnancy is the time period between fertilization of an oocyte and delivery of a fetus approximately 9 months later. The 1st sign of pregnancy is typically a missed menstrual period, after which, pregnancy should be confirmed clinically based on a positive β-hCG test (typically a qualitative urine test) and pelvic ultrasound. Pregnancy: Diagnosis, Maternal Physiology, and Routine Care or breastfeeding Breastfeeding Breastfeeding is often the primary source of nutrition for the newborn. During pregnancy, hormonal stimulation causes the number and size of mammary glands in the breast to significantly increase. After delivery, prolactin stimulates milk production, while oxytocin stimulates milk expulsion through the lactiferous ducts, where it is sucked out through the nipple by the infant. Breastfeeding.
  • Reduced levels of neuronal nitric oxide synthase have been shown to be involved in the pathogenesis.

Clinical Manifestations

Symptoms

  • Initially, regurgitation after feeding
  • Later, non-bilious, projectile vomiting immediately after feeding
  • Usually starts after 3 weeks of age (range: 1 week to 5 months)
  • Poor weight gain
  • Infant shows signs of hunger (irritability, increased sucking reflex).

Signs

  • Firm, mobile, olive-shaped, 2-cm mass above and to the right of the umbilicus in epigastrium
  • Gastric peristaltic wave across the abdomen after feeding
  • Signs of dehydration including sunken fontanelles, delayed capillary refill, dry mucous membranes, and/or decreased urine output may be present.

Diagnosis

Laboratory studies

  • Hypochloremic metabolic alkalosis Metabolic alkalosis The renal system is responsible for eliminating the daily load of non-volatile acids, which is approximately 70 millimoles per day. Metabolic alkalosis also occurs when there is an increased loss of acid, either renally or through the upper GI tract (e.g., vomiting), increased intake of HCO3-, or a reduced ability to secrete HCO3- when needed. Metabolic Alkalosis
  • Hypokalemia Hypokalemia Hypokalemia is defined as plasma potassium (K+) concentration < 3.5 mEq/L. Homeostatic mechanisms maintain plasma concentration between 3.5-5.2 mEq/L despite marked variation in dietary intake. Hypokalemia can be due to renal losses, GI losses, transcellular shifts, or poor dietary intake. Hypokalemia
  • Elevated blood urea nitrogen (BUN) and creatinine with severe dehydration
  • Unconjugated (and occasionally conjugated) hyperbilirubinemia is the most common clinical association.

Ultrasound

  • Diagnosis based on:
    • Pyloric muscle thickness: > 3 mm (the most discriminating and accurate criterion) 
    • Pyloric muscle length: > 15 mm
    • Pyloric diameter: > 15 mm

Contrast studies

  • If diagnosis not confirmed by ultrasound, but still suspected
  • String sign: elongated pyloric channel
  • Shoulder sign: pyloric bulging into channel
  • Double-track sign: parallel streaks of contrast in narrowed channel

Treatment

Preoperative care Preoperative Care Thorough preoperative care is important for patients scheduled to undergo surgery so that they can have the best possible outcomes after their surgical procedure. The preoperative process begins once the decision has been made to proceed with a surgical procedure. Preoperative Care

  • Fluid replacement + decompression
  • Correct electrolyte abnormalities
  • Restoration of acid-base balance

Surgery

  • Ramstedt pyloromyotomy: short transverse skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin incision plus longitudinal incision of pyloric muscle up to submucosa
  • Laparoscopy Laparoscopy Laparoscopy is surgical exploration and interventions performed through small incisions with a camera and long instruments. Laparotomy and Laparoscopy: equally effective with shorter hospital stay
Hypertrophic pyloric stenosis surgery

This is the classic definitive surgical treatment of hypertrophic pyloric stenosis called a “Ramstedt pyloromyotomy”, in which a longitudinal incision of the anterior surface of the pylorus is made down through the muscle layer only to the level of the submucosa, leaving the submucosa and mucosa in a prolapsed state.

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Postoperative care Postoperative care After any procedure performed in the operating room, all patients must undergo close observation at least in the recovery room. After larger procedures and for patients who require hospitalization, observation must continue on the surgical ward. The primary intent of this practice is the early detection of postoperative complications. Postoperative Care

  • Oral feeding can be initiated within 1224 hours.
  • Persistent vomiting suggests incomplete pyloromyotomy or an alternative diagnosis.

Conservative approach

  • If surgery not tolerated or unavailable
  • Oral and intravenous atropine and cardiac monitoring → gradual introduction of feeding

Differential Diagnosis

  • Gastroesophageal reflux disease Gastroesophageal Reflux Disease Gastroesophageal reflux disease (GERD) occurs when the stomach acid frequently flows back into the esophagus. This backwash (acid reflux) can irritate the lining of the esophagus, causing symptoms such as retrosternal burning pain (heartburn). Gastroesophageal Reflux Disease ( GERD GERD Gastroesophageal reflux disease (GERD) occurs when the stomach acid frequently flows back into the esophagus. This backwash (acid reflux) can irritate the lining of the esophagus, causing symptoms such as retrosternal burning pain (heartburn). Gastroesophageal Reflux Disease): a chronic disorder in which gastric acid, food, or fluids back up from the stomach Stomach The stomach is a muscular sac in the upper left portion of the abdomen that plays a critical role in digestion. The stomach develops from the foregut and connects the esophagus with the duodenum. Structurally, the stomach is C-shaped and forms a greater and lesser curvature and is divided grossly into regions: the cardia, fundus, body, and pylorus. Stomach into the esophagus Esophagus The esophagus is a muscular tube-shaped organ of around 25 centimeters in length that connects the pharynx to the stomach. The organ extends from approximately the 6th cervical vertebra to the 11th thoracic vertebra and can be divided grossly into 3 parts: the cervical part, the thoracic part, and the abdominal part. Esophagus. Patients often present with heartburn, bad breath, chest pain Chest Pain Chest pain is one of the most common and challenging complaints that may present in an inpatient and outpatient setting. The differential diagnosis of chest pain is large and includes cardiac, gastrointestinal, pulmonary, musculoskeletal, and psychiatric etiologies. Chest Pain, and regurgitation. Gastroesophageal reflux disease Gastroesophageal Reflux Disease Gastroesophageal reflux disease (GERD) occurs when the stomach acid frequently flows back into the esophagus. This backwash (acid reflux) can irritate the lining of the esophagus, causing symptoms such as retrosternal burning pain (heartburn). Gastroesophageal Reflux Disease can lead to damage to the teeth Teeth Normally, an adult has 32 teeth: 16 maxillary and 16 mandibular. These teeth are divided into 4 quadrants with 8 teeth each. Each quadrant consists of 2 incisors (dentes incisivi), 1 canine (dens caninus), 2 premolars (dentes premolares), and 3 molars (dentes molares). Teeth are composed of enamel, dentin, and dental cement. Teeth, esophagitis Esophagitis Esophagitis is the inflammation or irritation of the esophagus. The major types of esophagitis are medication-induced, infectious, eosinophilic, corrosive, and acid reflux. Patients typically present with odynophagia, dysphagia, and retrosternal chest pain. Esophagitis, and Barrett’s esophagus Esophagus The esophagus is a muscular tube-shaped organ of around 25 centimeters in length that connects the pharynx to the stomach. The organ extends from approximately the 6th cervical vertebra to the 11th thoracic vertebra and can be divided grossly into 3 parts: the cervical part, the thoracic part, and the abdominal part. Esophagus. Treatment includes lifestyle changes and medical therapy with antacids, proton pump inhibitors (PPIs), and prokinetics. 
  • Cyclical vomiting syndrome (CVS): a condition of unknown pathogenesis characterized by recurrent episodes of nausea, vomiting, and lethargy. Symptoms can last hours or days. Cyclical vomiting syndrome most commonly occurs in children but can affect individuals of any age. 
  • Gastroenteritis: inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of the gastrointestinal tract most often caused by viruses, but also bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology: Overview or parasites. Symptoms usually last less than 14 days and include increased stool frequency or diarrhea Diarrhea Diarrhea is defined as ≥ 3 watery or loose stools in a 24-hour period. There are a multitude of etiologies, which can be classified based on the underlying mechanism of disease. The duration of symptoms (acute or chronic) and characteristics of the stools (e.g., watery, bloody, steatorrheic, mucoid) can help guide further diagnostic evaluation. Diarrhea, fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, vomiting, or abdominal pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain
  • Congenital adrenal hyperplasia Congenital adrenal hyperplasia Congenital adrenal hyperplasia (CAH) consists of a group of autosomal recessive disorders that cause a deficiency of an enzyme needed in cortisol, aldosterone, and androgen synthesis. The most common subform of CAH is 21-hydroxylase deficiency, followed by 11β-hydroxylase deficiency. Congenital Adrenal Hyperplasia (CAH): a group of rare autosomal recessive Autosomal recessive Autosomal inheritance, both dominant and recessive, refers to the transmission of genes from the 22 autosomal chromosomes. Autosomal recessive diseases are only expressed when 2 copies of the recessive allele are inherited. Autosomal Recessive and Autosomal Dominant Inheritancediseases characterized by defects in enzymes Enzymes Enzymes are complex protein biocatalysts that accelerate chemical reactions without being consumed by them. Due to the body's constant metabolic needs, the absence of enzymes would make life unsustainable, as reactions would occur too slowly without these molecules. Basics of Enzymes of the adrenal glands Adrenal Glands The adrenal glands are a pair of retroperitoneal endocrine glands located above the kidneys. The outer parenchyma is called the adrenal cortex and has 3 distinct zones, each with its own secretory products. Beneath the cortex lies the adrenal medulla, which secretes catecholamines involved in the fight-or-flight response. Adrenal Glands involved in cortisol, androgen, and aldosterone synthesis. Patients may present with a wide range of symptoms, including virilization in females, salt-wasting leading to hypotension Hypotension Hypotension is defined as low blood pressure, specifically < 90/60 mm Hg, and is most commonly a physiologic response. Hypotension may be mild, serious, or life threatening, depending on the cause. Hypotension and other electrolyte abnormalities, and premature completion of growth resulting in short stature.
  • Increased intracranial pressure Increased Intracranial Pressure Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP): a medical emergency defined by an intracranial pressure exceeding 20 mm Hg that can lead to a decrease in cerebral perfusion as well as herniation of the brain. Common symptoms include headache, vomiting, altered mentation, papilledema, and bradycardia. Causes include increased production or partially obstructed outflow of cerebrospinal fluid, bleedings, tumors, and infections.
  • Volvulus Volvulus A volvulus is the twisting or axial rotation of a portion of the bowel around its mesentery. The most common site of volvulus in adults is the colon; most frequently the sigmoid volvulus. Patients typically present with symptoms of bowel obstruction such as abdominal pain, distension, vomiting, and constipation/obstipation. Volvulus: a condition in which a loop of intestine twists around itself and the surrounding mesentery, causing bowel obstruction. Volvulus Volvulus A volvulus is the twisting or axial rotation of a portion of the bowel around its mesentery. The most common site of volvulus in adults is the colon; most frequently the sigmoid volvulus. Patients typically present with symptoms of bowel obstruction such as abdominal pain, distension, vomiting, and constipation/obstipation. Volvulus is often caused by a birth defect and presents early in life, but can occur at any age. Common symptoms include vomiting, abdominal pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain and bloating, constipation Constipation Constipation is common and may be due to a variety of causes. Constipation is generally defined as bowel movement frequency < 3 times per week. Patients who are constipated often strain to pass hard stools. The condition is classified as primary (also known as idiopathic or functional constipation) or secondary, and as acute or chronic. Constipation, and bloody stool that may be gradual or sudden in onset. Emergency surgery is necessary to prevent necrosis of the intestinal structures.

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