Volume 5, Case 17
Loren G. Yamamoto, MD, MPH
Kapiolani Medical Center For Women And Children
University of Hawaii John A. Burns School of Medicine
This is a 3-week old male with a history of vomiting for three days. He vomits only after being fed. It resembles partially digested formula without blood or bile. He feeds well, but vomits 1-2 hours following feeding. The emesis is forceful. His mother describes the emesis as being able to project about 30 cm, rather than just dribbling down his mouth. He has already vomited 5 times today. He has also had two loose stools (no mucus, no blood, not foul). There is no history of irritability, fever, or ill contacts. His birth history is unremarkable.
Exam: VS T36.5 (rectal), P 140, R 37, BP 91/48. Weight 3.4 kg (birth weight 3.1 kg). Alert, active, looks around, focuses on mother. Anterior fontanelle flat. Sutures not splayed. Eyes normal. TM's normal. Oral mucosa moist without erythema. Neck supple. Heart regular without murmurs. Lungs clear. Abdomen soft, flat, bowel sounds active, no masses, no hernias. There is no palpable olive. Testes normal, descended. Hips, good range of motion without clicks or dislocatability. No CVA tenderness noticeable. Extremities, good tone and pulses. Color, perfusion, turgor good.
An abdominal series is obtained.
View abdominal series.
The view on the left is a supine view. The view on the right is an upright view. The supine view shows a dilated stomach, though not necessarily dilated with gas. The inferior margin of the stomach can be seen because it pushes the small bowel inferiorly. The upright view shows a moderate sized gastric air bubble. The gastric dilatation is not as clearly visible here. However, note that the small bowel does not seem to rise upward. It appears to be pushed inferiorly even though the patient is upright. This is probably because a dilated fluid-filled stomach is pushing it inferiorly.
Although gaseous distention of the stomach is commonly seen in crying infants or infants who swallow a lot of air, this is usually accompanied by lots of gas seen in the small bowel as well. In this case, the stomach is prominent, while the small bowel gas pattern is minimal, suggesting the presence of some type of gastric outlet obstruction. These plain films, in conjunction with the patient's history are highly suggestive of pyloric stenosis.
An ultrasound study is ordered to confirm the presence of pyloric stenosis.
View pyloric ultrasound.
US-1 shows the measurements of the pylorus. The pyloric length measures 21.6 mm (line #1). The pyloric wall thickness measures 4.6 mm (line #2). The pyloric diameter measures 9.3 mm (line #3). Exceeding the measurements of 16 mm, 4 mm, and 14 mm, respectively is indicative of pyloric stenosis.
US-2 shows another view of the pylorus. The pyloric length measures 21.4 mm in this view. The black arrow points to a prominent indentation of the pylorus into the stomach. This finding is also indicative of hypertrophic pyloric stenosis.
Discussion
Hypertrophic pyloric stenosis occurs in roughly 1 in every 500 to 1000 live births. It is more common in male infants. The etiology is unclear. There is a moderate hereditary predisposition in children of affected parents.
Although pyloric stenosis is felt to be congenital, nearly all affected infants do not have symptoms as a newborn. Vomiting usually begins at about three weeks of age, but ranges from 1 week to 5 months. Initially, infants may vomit 1 to 2 times per day. As the obstruction worsens, vomiting becomes more forceful and more frequent. The vomitus is non-billious. It may occasionally contain blood due to capillary rupture secondary to the forceful vomiting.
Gastric peristalsis can often be seen as an impressive wave passing from left to right. These infants are typically very hungry. While feeding, palpation of the abdomen may reveal an olive shaped mass in the right upper quadrant. Palpation of an olive is pathognomonic for pyloric stenosis. It should be noted that palpation of an olive is very difficult. It is most accurately identified by highly experienced clinicians.
Initially, there may be modest dehydration with hyponatremia, hypokalemia, and a metabolic alkalosis. An Addisonian crisis in infant males with undiagnosed congenital adrenal hyperplasia (21-hydroxylase deficiency) may also present with vomiting; however, Addisonian crisis infants have HYPERkalemia and usually are acidotic.
If appropriate treatment for pyloric stenosis is not implemented, the dehydration will worsen and continued weight loss with failure to thrive will occur. Hypoglycemia may also occur.
In the past, upper GI barium contrast radiographs were most commonly used to confirm the diagnosis of pyloric stenosis. The contrast study would identify an elongated and thin pyloric canal. The thickness of the pyloric wall could not be assessed with barium contrast.
Ultrasound is currently the most frequently used study to identify pyloric stenosis. There is no radiation exposure and it keeps the stomach empty to reduce the risk of regurgitation and aspiration during anesthesia induction if surgery is required. Examining the length of the pylorus, the thickness of the pyloric wall, the diameter of the pylorus, and the shape of the pylorus are all helpful signs in establishing the diagnosis of pyloric stenosis.
Plain films of the abdomen are often obtained before an ultrasound is ordered. The finding of a dilated stomach (fluid or air filled) associated with not much gas in the small intestine, is highly suggestive of pyloric stenosis if the clinical history is consistent. However, ultrasound should still be used to confirm pyloric stenosis.
Surgical intervention (pyloromyotomy) is the most efficient means to relieve the pyloric stenosis. However, medical management, including fluid resuscitation and correction of metabolic abnormalities, is often required prior to surgical intervention.
References