Saturday, April 28, 2012

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Hypertrophic pyloric stenosis of infancy


Epidemiology: 
Incidence of 3/1000 births. 
4 times more in males. 
Aetiology is unknown. In some cases there seems to be a familial association. In such families the mother has suffered from the condition in 50 per cent of cases. Characteristically it is a first-born male child that is most commonly affected. The condition is most commonly seen at 4 weeks after birth ranging from the third week to, on rare occasions, the seventh. Inexplicably, it is the time following birth that seems important and not the child’s gestational age. A premature infant will also develop the condition at about 4 weeks after birth.

Pathology:
Grossly hypertrophied musculature of the pylorus and adjacent antrum, the hypertrophy being maximum in the pylorus itself. The mucosa is compressed such that only a probe can be inserted.

Clinical features:
Vomiting is the presenting symptom that after 2—3 days becomes forcible and projectile. The child vomits milk and no bile is present. Immediately after vomiting the baby is usually hungry. Weight loss is a striking feature and rapidly the infant becomes emaciated and dehydrated. Diagnosis can usually be made with a test feed. This may produce characteristic peristaltic waves that can be seen to pass across the upper abdomen. At the same time, using a warm hand, the abdomen is palpated to detect the lump.

Imaging:
Ultrasonography is the investigation of choice as it can, without difficulty, detect the classical features in the pyloric canal.
Contrast radiology was done in the past but is not necessary now.

Differential diagnosis:
The common D/D are gastro-oesophageal reflux, feeding problems, urinary tract infection and raised intracranial pressure.
 The condition cannot normally be confused with duodenal atresia or intestinal obstruction because of the absence of bile in the milk vomit.

Treatment:
Following diagnosis the first concern is to correct the metabolic abnormalities. Essentially this is the same situation that pertains in adults with the patient being dehydrated, with low sodium, chloride and potassium, and a metabolic alkalosis.
The child should be rehydrated with dextrose—saline and potassium (2.5 per cent dextrose plus 0.45 per cent sodium chloride plus 1 g of potassium chloride per 500 ml of fluid). This will restore the infant’s clinical condition and electrolytes to normal. Following stabilization of the patient, operation is required. 
Conservative treatment has little place in the management of this condition as with appropriate surgical treatment recovery is virtually 100 per cent.

Ramstedt’s operation
1) In preparing the child for operation it is important that the stomach is emptied and washed out with saline, and that hypothermia is avoided. To achieve this, the patient is encased in cotton wool allowing exposure of the upper abdomen. 
2) Operation is performed under general anaesthesia, although it is possible to perform the procedure under a local anesthetic. 
3) The skin is opened through a transverse incision placed in the upper abdomen over the right rectus sheath, which is opened in the same line. The rectus muscle is then split along the line of its fibres and the posterior rectus sheath opened in the line of the skin incision. 
4) The hypertrophied pylorus is delivered and rotated so that its superior surface comes into view. Thus, the least vascular portion can be selected for incision. To ascertain the distal limit of the hypertrophy the surgeon invaginates the duodenum with the index finger. 

5) The incision is made through the serosa only and from this point along the whole length of the pylorus and, importantly, the distal antrum. The hypertrophied pylorus has the consistency of an unripe pear, hence splitting the muscle coats can be accomplished by blunt dissection. On separating the edges with artery forceps the pyloric mucosa bulges into the cleft which has been made in the muscle as shown in the diagram above. 
6) Great care is taken not to penetrate the mucosa. When this injury occurs it is almost always in dividing the most distal part of the constricting fibres which are in the vicinity of the duodenal fornix. To be sure that there is no perforation some air is squeezed from the stomach into the duodenum. If a perforation has occurred it is closed and a piece of omentum placed over the closure. 
7) Haemostasis should be meticulous.


After operation the nasogastric tube can be removed and feeding commenced on the morning after operation. If the infant manages to feed without difficulty it can be discharged early from hospital. If the mucosa is inadvertently opened it is wise to delay feeding for 48 hours and to retain the child in hospital longer.

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