I was surprised to find recently that when a premature baby has infant pyloric stenosis (PS), there are some notable differences from the way full-term babies present with this condition. It is important for general practice medical doctors and pediatricians to be aware of these differences, so I’ll pass on what I learnt for the interest and benefit of readers: survivors, parents, and medical workers.
What motivated me to research this subject?
A recent web chat with a fellow PS survivor who was born 3 months premature taught me that early arrival lowers the risk of PS. However, because PS so often comes with stress and an increased incidence of other congenital abnormalities, I had assumed that prematurity would increase the incidence of PS. Fair enough as an assumption, but apparently I was wrong: the medical literature I have read mostly (but not unanimously) tells me that premature infants have less chance than full-termers of having infant pyloric stenosis. My research surprised me in several ways…
Pyloric stenosis in the premature infant is rather hazardous because it usually presents in a more deceptive way than in full-term babies. In full-term babies, the diagnosis of PS is all-too-often delayed until the baby has almost expired. Because prematurity comes with its own list of dangers and complications, the recognition of PS is even more often delayed. In addition to this, compared with the PS symptoms of an average full-term baby, the premature infant with PS will usually present differently.
1 Vomiting is more likely to be more intermittent and less forceful.
2 As always, medical (drug) treatment is likely to reduce the condition’s severity, often making surgery unnecessary – but sometimes delaying surgery while the baby loses still more of its already more delicate condition.
3 Informed parents will look out for the rather dramatic PS symptoms of projectile non-bilious (without bile) vomiting, ravenous hunger after vomiting, severe weight loss, lack of bowel motions and even urination which are typical of the infant brought to the clinic or hospital from home: these are all likely to be less severe in premature babies.
4 Alert doctors will look for the visible signs of PS present in full-term babies: severe vomiting, seeing gastric peristalsis (waves of muscle action over the stomach) after feeding, and finding “the pyloric olive” (swollen pylorus): these are (or were once) valuable and often sufficient diagnostic tools. But in premature infants these clinical symptoms are also typically unclear. So barium and ultrasound tests may be needed, which take time – which is especially critical for a tiny sick baby.
5 Added to this, the pyloric measurements (pyloric wall thickness, length and width of the pyloric passage) as measured by sonography give a clear diagnostic indication in full-term babies but less so in premature infants. (See also #7 below.)
6 The medical literature informed me that whereas the average age of the onset of PS symptoms in a full-term baby is 3 weeks, it averages 5 weeks in a premature infant. However, the several reports I read included several pre-term babies whose PS developed earlier than 3 weeks!
7 At operation, the swollen pylorus of premature infants is softer, more pliable, less gritty and thinner than that found in full-term babies.
8 Several journal articles mentioned that the common practice of feeding tiny infants by a tube that passes past their pyloric muscle is suspected of both causing some PS cases and often delaying its diagnosis.
9 Findings about the incidence of PS in pre-term infants seem to vary somewhat. A Taiwanese project reported on all the IHPS patients admitted to all the country’s hospitals between 1991 and 2004 enrolled 214 babies, 18 of whom were premature. The average age overall at diagnosis was 40 days. A significantly older age of symptom onset, a lower body weight at admission, more cases diagnosed by barium meal study and higher postoperative complication rates were noted in the preterm group versus full-term infants with IHPS. Cases diagnosed before 3 weeks and pre-term infants had higher complication rates and longer hospital stays.
A 2009 Australian study however, reported in its Abstract: IHPS occurs more frequently in male and ex-premature infants. It commonly presents without the full spectrum of ‘classic’ symptoms and signs. Given the availability of ultrasound diagnosis, IHPS should be considered in all babies with any one of the classic findings.
A 2012 U.S. study seemed to bear out these surprising findings! Again in its Abstract, it reported: The authors found pyloric stenosis to be significantly associated with male sex, age between 2 and 7 weeks, early study period, being first born, maternal smoking during pregnancy, preterm delivery, small weight for gestational age, Caesarean section, and congenital malformations.
Nowhere have I read that premature babies with PS have been found to be less likely to survive the condition and its treatment. The death rate from infant PS remains less than 1% in countries with a good standard of health care. However, each of pre-maturity, PS and surgery carries its own risks.
One Report concluded: A premature infant, 3 months of age or less who vomits gastric contents, fails to gain weight, and is constantly hungry, is likely to have pyloric stenosis. Palpation of the pyloric tumor is certain evidence of the diagnosis.