Infantile Hypertrophic Pyloric Stenosis

Authors:

Shiela Beroukhim
David Geffen School of Medicine at UCLA, Los Angeles, California

George Gershman, MD
Department of Pediatrics, Division of Gastroenterology, Harbor–UCLA Medical Center, Torrance, California

Jennifer K. Yee, MD
Department of Pediatrics, Division of Pediatric Endocrinology, Harbor–UCLA Medical Center, Torrance, California

Citation:

Beroukhim S, Gershman G, Yee JK. Infantile hypertrophic pyloric stenosis [published online February 27, 2018]. Consultant for Pediatricians.

A 3-week-old neonate, born at 37 3/7 weeks’ gestational age, presented to our clinic after 5 days of projectile, nonbilious emesis and poor weight gain. His toddler sibling had just recovered from an acute vomiting illness after foreign travel. The neonate’s physical examination findings at the time were normal, and no masses were palpable in the abdomen. An abdominal ultrasonogram showed a pylorus with normal measurements and gastric contents passing through in real-time imaging. Electrolyte levels were normal. One week later, persistent vomiting had led to a 6% loss of body weight, and the patient was admitted to the hospital.

Physical examination. In the hospital, the neonate appeared eager for feeding but had forceful vomiting of both formula and oral rehydration solution.

Laboratory tests. Laboratory test results included the following values: sodium, 135 mEq/L; potassium, 4.3 mEq/L; chloride, 89 mEq/L; bicarbonate, 28 mEq/L; blood urea nitrogen, 6 mg/dL; creatinine, 0.6 mg/dL; glucose, 94 mg/dL; and total bilirubin, 7.0 mg/dL.

The electrolyte levels returned to normal after rehydration. A second abdominal ultrasonogram, performed 1 week after the initial examination in our clinic, showed a pylorus with normal wall thickness (3.0 ´ 14.4 ´ 9.8 mm, Figure 1).¹ The pylorus was opening widely intermittently, and gastric contents were passing through. A kidney, ureter, and bladder radiograph demonstrated a normal gas pattern. An upper gastrointestinal radiographic series showed a markedly dilated stomach, reflux of stomach contents into the esophagus, and delay in gastric emptying, but no anatomic abnormalities (Figure 2).

Figure 1. Abdominal ultrasonogram showing the pylorus with normal measurements.

Figure 2. Image from upper gastrointestinal series showing a dilated stomach.

The patient then underwent upper gastrointestinal endoscopy, which demonstrated a narrow opening to the pylorus, edematous pyloric folds with mucosal hypertrophy, and antral nippling (protrusion into the stomach) (Figure 3). The patient received a diagnosis of infantile hypertrophic pyloric stenosis (IHPS). He received definitive surgical treatment by pyloromyotomy. Subsequently, he tolerated oral feedings and was discharged home.

Figure 3. Image from upper gastrointestinal endoscopy showing a narrow opening of the pylorus, edematous pyloric folds with mucosal hypertrophy, and antral nippling (protrusion into the stomach).

Discussion. IHPS is a common cause of gastrointestinal tract obstruction, occurring in approximately 2 to 3 neonates per 1000 births.² Classically, IHPS presents between 4 and 8 weeks of life³ with forceful nonbilious, nonbloody emesis, a palpable olive-like mass in the abdomen, hypochloremia with metabolic alkalosis, and ultrasonography findings of a thickened pylorus. However, in this case, no olive-like mass was palpable, and the patient had 2 abdominal ultrasonograms that showed normal results.

This case illustrates that IHPS should remain in the differential diagnosis for newborns with forceful vomiting despite normal abdominal examination findings and normal ultrasonography findings. Studies have shown that palpation of the abdominal olive-like mass is highly predictive of IHPS. However, the clinical examination has low sensitivity.^4,5 Therefore, a lack of physical examination findings does not necessarily exclude the condition. One study demonstrated that the sensitivity of the physical maneuver dropped from 87% in the 1970s to 49% in the late 1980s, during which time dependence on imaging for diagnostic purposes increased.⁶

Similarly, normal ultrasonography findings should not exclude the diagnosis. Serial ultrasonography scans may be required before enlargement of the pylorus becomes apparent.⁷ While the sensitivity of ultrasonography in detecting a hypertrophied pylorus is upward of 95%,⁵ our patient’s case illustrates that development of pyloric stenosis is a progression in which the early stages can produce symptoms without being apparent on imaging. The dilated stomach on upper gastrointestinal imaging suggested a gastric outlet obstruction. Therefore, it is important to pursue the diagnosis of IHPS despite normal pyloric measurements on initial ultrasonograms.

Our patient’s hypochloremia was an important clinical clue. Electrolyte abnormalities are only observed in approximately half of infants with IHPS. One study that compared infants with IHPS with infants with gastroesophageal reflux disease determined that the sensitivities of hypochloremia (≤98 mEq/L) and metabolic alkalosis (≥29 mEq/L) were low (approximately 50% and 36%, respectively). However, their presence was highly predictive (97% and 96%, respectively) and highly specific (both 99%) for IHPS.⁸ Therefore, when clinical symptoms strongly suggest IHPS, we advocate for the use of clinical judgment for prompt referral for surgical management. If confirmation of IHPS is desired in inconclusive cases to avoid unnecessary surgery, upper gastrointestinal endoscopy allows direct visualization of the hypertrophied pylorus.⁹

Conclusion. Hypochloremia in the setting of projectile emesis in this neonate was suggestive of IHPS. IHPS develops over time and may not be apparent on initial ultrasonograms. Providers caring for infants with projectile vomiting should maintain clinical suspicion for IHPS even in the absence of the classical olive-like mass on physical examination or ultrasonographic evidence.

References

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Acknowledgement:

The authors acknowledge Steven Lee, MD, associate professor of surgery in the Division of Pediatric Surgery at Harbor–UCLA Medical Center in Los Angeles, California.