Infantile hypertrophic pyloric stenosis (IHPS) is a condition seen in infants, wherein the muscles in the pylorus (lower part of the stomach) become enlarged enough to prevent the food from entering into the intestine. This results in projectile vomiting, where the food is ejected forcefully from the mouth, sometimes over a distance of several feet. Characteristically, no bile is present in the food thrown up. Since little or almost no food reaches the intestine, stools are smaller and fewer, and the infant fails to gain weight. In more advanced cases of the disease, fluid and salt abnormalities with hypochloremic metabolic alkalosis may also set in. No definite etiology has been proved for IHPS. Most theories indicate that the condition may be due to abnormal muscle innervations, immature ganglion cells, decreased nitric-oxide stimulation of muscle fibers, and/or abnormal levels of gastrin.
IHPS is seen most commonly between the age of 3-6 weeks. Around 2-3 per 1000 infants suffer from this condition and the disease has an incidence rate of about 1 in every 500 live births. In fact, IHPS accounts for a third of all non-bilious vomiting occurrences in infants, and is the most common reason for laprotomy before one-year of age. Diagnosis depends upon the triad of projectile vomiting, visible peristalsis, and a palpable pyloric tumor or radiographic evidence of "string sign". Ultrasound analysis is the preferred mode of diagnosis. Treatment involves pyloromyotomy, a surgical procedure involving cutting through the thickened muscles of the pylorus. This is a relatively simple surgery, and patients are usually sent home 48 hours post-surgery.
A definite genetic basis has been attributed to IHPS, considering that an increased incidence is observed in families in which a sibling or parent has had the disease. However, the pattern of inheritance is debatable. On the one hand, a sex-modified model of multifactorial inheritance has been proposed considering the fact that the disease affects males four times more than females. On the other hand, pedigrees consistent with autosomal dominant mode of inheritance have also been reported. The nitric oxide synthase 1 (NOS1) gene on chromosome 12 has been implicated as a candidate gene. It has been proposed that patients may have a defect in production of nitric oxide, a chemical that relaxes the pylorus muscle.
Al Rasromani and Kamath (1988) performed a prospective study over a period of 7-years to measure the initial electrolyte changes in 59 patients with IHPS (11-90 days of age), treated with pyloromyotomy. The patients were assigned to four different groups according to their serum bicarbonate values: Group 1 (< 18mmol/ L; 2%), Group 2 (>18 < 25 mmol/L; 35%), Group C (>25 < 30 mmol/L; 39%), and Group D (> 30 mmol/L; 26%). Interestingly, group D, apart from showing the highest mean bicarbonate level, also showed significantly lower mean serum potassium as well as mean chloride values when compared to the other groups. Elevated bicarbonate levels, accompanied with depressed potassium and chloride levels are characteristic of the metabolic alkalosis exhibited in IHPS. The duration of vomiting was also observed to be most severe in group C and D, and the patients in these groups had moderate to severe dehydration as compared to the mild dehydration exhibited in the other two groups. Most importantly, 15% of the patients studied had normal serum electrolyte levels. No demographic characters were able to distinguish these patients from those with typical metabolic alkalosis. Al Rasromani and Kamath (1988) therefore, stressed the need for contrast study in doubtful cases for an accurate diagnosis, as serum electrolytes may show atypical findings which may delay the diagnosis.
[Al Rasromani KH, Kamath BM. Serum electrolytes in hypertrophic pyloric stenosis. Bahrain Med Bull. 1988; 10(3):145-7.]
Ali and Haddad (1996) reported a newborn baby with hypertrophic pyloric stenosis on the first day of life. It is suggested that this case report documents the youngest baby ever operated upon for infantile hypertrophic pyloric stenosis at 26 hours of age.
Kakish (2002) conducted a retrospective study that included 72 patients with cystic fibrosis and revealed the presence of IHPS in two. The incidence of 2.7% is greater than the 0.3% incidence expected in the general population. Kakish (2002) suggested that the nine fold increase in IHPS in patients with CF could be due to an association between the two disorders and warrants further investigation.
Rajyashree and Nayar (2000) reported a four-day old male neonate with symptoms of pyloric stenosis. The patient presented since the first day of life with feeds intolerance and increasing gastric aspirates (>30 ml/day), along with upper abdominal distension, jaundice, and constipation for two days. He was born at term with a history of birth asphyxia to a 35-year old mother who had history of polyhydramnios at pregnancy. Family history revealed that all his siblings had similar physical appearance, two siblings had died at the ages of three and six months, respectively, and one male sibling was operated on for infantile pyloric stenosis at the age of one month. Clinically, he was dehydrated, with dysmorphic features such as unfolded pinna, thick skinned with coarse hair all over, had and stiff joints, dysplastic nails, and bilateral undescended testicles. His abdominal examination revealed a full upper abdomen with a vague mass in the right upper quadrant. Investigations revealed gas in the stomach with minimal gas on the left side distally on plain abdominal X-ray, and upper gastrointestinal contrast study showed evidence of gastric outlet obstruction at the pylorus. Minimally dilated lateral ventricles of the brain were also evident on investigating this neonate. Blood investigations were normal except for elevated urea level. On the sixth day, Ramstedt's pyloromyotomy was done, as at surgery the typical pyloric tumor was confirmed. The postoperative period was uneventful and the baby was discharged after tolerating feeds in the 12th day.
[Rajyashree NK, Nayar PM. Hypertrophic pyloric stenosis at birth, a case report and review of literature. Oman Med J. 2000; 17(2):43-5.]
Al-Salem et al. (1990) reported three cases of infantile hypertrophic pyloric stenosis who had concomitant congenital diaphragmatic hernia.
Sayed and Al-Alaiyan (1996) reported a full-term infant who presented with Hirschsprung disease and hypertrophic pyloric stenosis, along with agenesis of corpus callosum; a combination reported for the first time. The authors believed that this combination was probably due to an underlying pathophysiologic mechanism.
Dawson et al. (1996) conducted an 11-year retrospective study among indigenous Emiratis in order to uncover the incidence of infantile hypertrophic pyloric stenosis. From 1984-1994, 10 male patients were recorded giving an incidence rate of 0.61 per 1,000 live births, which means it is a rare condition. This finding reflects no increase in the number of cases over time and yearly fluctuations were comparable to date from the UK. [Dawson KP, Ghazala BS, Shawis R. Infantile hypertrophic pylotic stenosis is rare in an indigenous population of the United Arab Emirates. Med Princ Pract. 1996; 5(4):218-21.]
Hosani and Czeizel (2000) evaluated the pilot dataset [March-May 1998] of the UAE National Congenital Abnormality Registry (NCAR). A total of 4,861 births were recorded in this study period, with a birth prevalence of total congenital anomalies being 30.3 per 1,000 births. Congenital pyloric stenosis was identified in two neonates, resulting in an incidence rate of 0.41 per 1,000 births.