Infantile hypertrophic pyloric stenosis in an extremely preterm male twin; a case report and review.

Sir,

Infantile hypertrophic pyloric stenosis (IHPS) is quite rare in extremely preterm babies [born at or before 28 weeks of gestation (GW)]. IHPS has been reported at birth and even in utero among term babies.[1] We report a unique case of IHPS presenting in an extremely preterm male twin.

A 42-day-old preterm, male baby [twin B] born at 28 GW with low birth weight (LBW) of 900 g, along with his sister (twin A weighing 1000 g) was refereed to us with a diagnosis of severe gastroesophageal reflux (GER). Twin B had repeated copious, nonbilious, nonprojectile vomiting after every feed; followed by voracious appetite since 4th week of life. Examination revealed a very small dehydrated infant weighing 1,300 g, with epigastric fullness and weak visible gastric peristalsis (VGP). The pyloric “olive” was not palpable. Arterial blood gases revealed mild metabolic alkalosis. There was hyponatremia, hypokalemia, and hypochloremia. X-ray abdomen showed air distended stomach with a paucity of intestinal gas. Ultrasound abdomen demonstrated hypertrophied pyloric wall, measuring 16 × 14 × 6 mm in length, external diameter wall and thickness, respectively [Figure 1]. After resuscitation at surgery, a 2 × 1.5-cm white glistening, pliable, elongated, and thickened pylorus was found hence pyloromyotomy was performed. Postoperatively, baby required 6 h of mechanical ventilation, accepted oral feeds on day 2 and was discharged home on day 4. Baby is thriving well. His sister, twin A is under observation.

Figure 1

(a) Showing dizygotic opposite sex twins with low-birth weight male twin having a surgical scar of pyloromyotomy. (b) Ultrasonography image showing classical target sign [Left] and longitudinal section image [Right] showing pyloric dimensions suggestive of IHPS

The incidence of IHPS in premature babies is only 3.1%.[2] Even in twins, males have a higher risk of developing IHPS than females,[3] Preterm babies with IHPS present later during the 5th week of life; when compared to 3rd week in term infants.[4] However, when gestational age is considered, IHPS, in fact presents earlier in preterm babies (between 32 and 42 GW) than in term ones (45-52 weeks) because both require certain degree of extra-uterine maturation of the gut. This gastrointestinal (GI) maturation leading to hypertrophic pylorus occurs quite early and rapidly in preterm babies. Premature babies with IHPS can present well before the infant even becomes a “term baby”.[5]

Feed intolerance in preterm manifesting as recurrent emesis and abdominal distention is often attributed to GER, or “gut immaturity” rather than IHPS,[6] further delays the diagnosis. Rarity of the disease, atypical presentation, absence of classical electrolyte, and acid base abnormalities, along with a poorly defined sonological diagnostic criteria further compound confusion to the diagnosis of IHPS in preterm babies.[4]

The characteristic projectile vomiting, VGP and metabolic alkalosis, and palpable pyloric olive (despite thin abdominal wall) are usually absent in preterm infants with IHPS.[4] Hence early ultrasonogram and or complementary upper GI contrast study must be done to confirm or refute the presence of IHPS in a preterm.

Mild or even absence of classical electrolyte and acid base disturbances of IHPS,[4] are attributed to the proportionate loss of water and sodium from a relatively large extracellular fluid volume and relatively less secretion of gastric acid in the preterm. The pyloric mass is softer, more pliable, less gritty, and thinner in preterms than in term infants.

Prolonged medical treatment associated with delayed diagnosis and malnutrition increase the postoperative complications and recovery time which is due to physiological immaturity of the organs and LBW of a preterm rather than IHPS per se.[4] Early surgical intervention can decrease the morbidity and mortality. IHPS should always be considered in the differential diagnoses in a preterm with feed intolerance, GER, or recurrent vomiting.