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Infantile Hypertrophic Pyloric Stenosis 369

thin abdominal wall. On examination, a mobile, ovoid mass, commonly Serum Electrolytes
referred to as an “olive”, is palpable in the epigastrium or the right Serum electrolytes should be measured immediately when the patient
upper quadrant. arrives in hospital. If vomiting has been ongoing for several days,
If the pylorus is palpated by an experienced clinician, no further serum electrolytes are frequently deranged. The nature of derange-
imaging is necessary. In some cases, however, other structures may be ment is a spectrum, 15,16 ranging from mild to severe hyponatraemia,
confused with hypertrophied pylorus, including the caudate lobe of the hypochloraemia, hypokalaemia, and metabolic alkalosis. The degree of
liver, the right kidney, the vertebrae, or an orogastric tube in the distal elevation of serum urea is directly related to the severity of dehydration.
stomach. If there is any doubt, or in the absence of a palpable “olive”, Haemogram/Full Blood Count
diagnostic imaging can be helpful.
Infants presenting late are often malnourished and may have some
Ultrasonography degree of anaemia, which may require correction. Therefore, a haemo-
In situations where doubt exists, examination by ultrasound (US) gram and full blood count are warranted.
should be performed. This would normally confirm the presence of a Treatment
pyloric “tumour”. The characteristic appearance of pyloric stenosis on
ultrasound is that of a “doughnut” or “bull’s eye” on cross section of Correction of Electrolyte and Fluid Depletion
the pyloric channel. Pyloric dimensions with positive predictive value Patients with pyloric stenosis may have severe electrolyte disturbances,
greater than 90% are muscle thickness greater than 4 mm and a pyloric so the serum electrolytes should always be estimated. Mild electrolyte
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channel length greater than 17 mm. These limits may be lower in disturbances can be corrected preoperatively with 0.45% normal saline
infants younger than 30 days of age (Figure 59.1). with 5% dextrose solution. Severe disturbances require correction with
An experienced sonographer will recognize periods of relaxation in 0.9% normal saline bolus of 10 to 20 ml/kg, followed by administra-
infants with pylorospasm, commonly confused with pyloric stenosis at tion of 0.9% saline in 5% dextrose solution. Potassium can be added
examination. Pylorospasm has been hypothesized to be an early stage if necessary when adequate urine output (1.5–2 ml/kg per hour) is
of IHPS, but this has not been proven. established and under electrocardiogram (ECG) monitor. Fluid should
Upper Gastrointestinal Contrast Study be administered at a rate of 25–50% above maintenance.
Following resuscitation and correction of electrolyte imbalance,
In an occasional case where doubt still persists after US examination,
maintenance IV with 0.45% saline in 5% dextrose with 20 mmol
an upper gastrointestinal (UGI) series may be done. The UGI series
potassium chloride should be given at 25-50% above the standard rate.
would show a narrow pyloric channel, the so-called “string sign” and
Meticulous care and time should always be taken to correct fluid and
the “shoulder sign”, caused by the impression of the pylorus into the
electrolyte depletion before any surgical correction. It is important to
stomach (Figure 59.2).
emphasize that mortalities from pyloric stenosis are attributable to fluid
and electrolyte problems.
Nasogastric Decompression
Once diagnosis is made, all feeds are stopped. It is helpful to aspirate
all gastric content by nasogastric tube (NGT). Frequently, this con-
tent comprises milk curds, which may require lavage with saline to
adequately evacuate the stomach. Keeping the stomach empty would
help prevent aspiration from vomiting. Once the stomach is emptied,
the NGT is either closed off or removed to avoid worsening electrolyte
depletion by aspirating gastric content.
In the West, gastric lavage is not routinely performed. An NGT
is passed, size 8 Fr or above. Gastric losses are monitored and
replaced milliliter for milliliter with 0.9% saline. To avoid iatrogenic
hyperkalaemia, no potassium is added to the replacement fluid.
Figure 59.1: Ultrasound features of pyrolic stenosis.
Surgical Correction
Surgical correction of pyloric stenosis is not an emergency, and there-
fore the electrolyte disturbances can and should be meticulously cor-
rected before operation. Occasionally, children with pyloric stenosis
will have jaundice due to a transient impairment of glucuronyl transfer-
ase activity. This is self-limited once postoperative feeding is initiated.
Infants undergoing pyloromyotomy are assumed to have a full
stomach and the anaesthesiologist should keep this in mind. Both the
anaesthesiologist and surgeon should be vigilant during the operation
to prevent aspiration of gastric juice. The stomach must be evacuated
in the operating room, particularly if NGT had not been inserted earlier.
Preoperative antibiotics are controversial; data supporting their use
with the standard right upper quadrant incision are scant. They may be
of benefit when performing the operation through the umbilical skinfold.
Operative Details
The standard operation is the Ramstedt pyloromyotomy. Classically,
the operation has been approached through a right upper quadrant
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muscle-splitting approach . Alternatively, the approach may be via a
supra-umbilical transverse skinfold incision.
1. Once the peritoneum is entered, the omentum is retrieved into
Figure 59.2: UGI contrast showing pyloric stenosis.