Surgical problems

Published on 03/06/2015 by admin

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Last modified 03/06/2015

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CHAPTER 23 Surgical problems

Mark Davies, Garry Inglis

Bile

Bile may appear in vomitus or in aspirates from gastric tubes. Bilious vomiting should always be considered as potentially serious, especially in a previously well baby when an acute volvulus should be suspected and ruled out.

Generally speaking, the presence of bile that has made its way into the stomach (and is seen in vomitus or gastric tube aspirates) indicates that the gut is obstructed. This obstruction may be complete or partial, and may be anatomical or functional (i.e. with a still patent lumen).

For anatomical causes of obstruction see pages 131–3.

Functional gut obstruction can occur in babies in the following circumstances:

• gastrointestinal perforation (see below)
• necrotising enterocolitis (NEC; see below)
• post-surgical
• any baby that is generally unwell (especially with infection)
• gut immaturity, especially in babies <30–32 weeks gestational age.

Sometimes bile is seen in aspirates when the feeding tube sits at or has passed through the pylorus — this can be confirmed on an abdominal X-ray. In an otherwise well baby, this can be fixed by pulling the tube back so that its tip lies in the body of the stomach.

Determining cause

Significant causes of bile vomiting or bile-stained aspirates need to be distinguished from benign causes (such as a malplaced nasogastric tube or gut immotility due to immaturity) by examining the baby, and doing an abdominal X-ray and a full blood count (FBC) and film examination (and taking a blood culture and starting antibiotics if there is any suspicion of infection).

• Benign causes will usually be found in babies who are otherwise well with a soft, non-distended, non-tender abdomen that is not discoloured, who are passing normal stools.
• Significant causes may be associated with one or more of:

— an unwell baby
— an abnormal abdominal exam — distended, tender or tense, discolouration, mass, absent bowel sounds
— an abnormal abdominal X-ray — evidence of gastrointestinal perforation or necrotising enterocolitis, fluid levels, bowel distension
— an abnormal FBC — signs of infection, thrombocytopaenia.

Gastrointestinal perforation

Extremely preterm infants are prone to gastrointestinal perforation, which can occur in isolation or, more commonly, in association with necrotising enterocolitis (NEC; see below). If intestinal perforation is found, it does not automatically follow that NEC is present. It can be difficult to distinguish the two conditions pre-operatively, and risk factors are similar.

• Clinically the abdomen with perforated bowel and hence free peritoneal gas is almost always ‘smooth’ in appearance. When bowel loops are visible through the abdominal wall, often described as a ‘ropey’ abdomen, free gas is usually not present.
• In a plain supine X-ray of the abdomen, the presence of free gas in the peritoneal cavity (pneumoperitoneum) is demonstrated as a grey outline around the abdominal edge, with the falciform ligament visible in the upper abdomen to the right of the midline. This gas shadow is sometimes called the ‘football’ sign. Remember that the plain abdominal film is not usually taken erect, so don’t waste your time looking for a rim of free gas under the diaphragm. If in doubt, a right-side-up lateral decubitus film may be helpful as the gas may rise above the right lobe of the liver.
• ‘Double-shadowing’ of bowel walls is also indicative of free gas in the abdominal cavity — the Frimann-Dahl sign or Rigler’s sign. Normally only the mucosal surface of the bowel is contrasted by the presence of gas; free gas abutting the serosal surface creates another interface, giving rise to the characteristic double-shadow.
• Suspicion of free gas within the peritoneal cavity should also be raised where an unusually shaped shadow is present — i.e. if the gas shadow does not conform to any anatomical structure.

The management of infants with gastrointestinal perforation should include:

• stopping enteral feeds
• nasogastric tube with regular aspiration
• intravenous fluids
• antibiotics (after blood culture)
• immediate review by a paediatric surgeon; encourage them to do a laparotomy.

Necrotising enterocolitis (NEC)

This inflammatory disorder of the bowel has multifactorial causes. The extremely preterm infant is at greater risk.

There is a wide spectrum of clinical features in NEC. Signs can include feeding intolerance, vomiting, lethargy, temperature instability, abdominal distension, diarrhoea with or without frank blood, abdominal wall erythema and shock.

The Bell criteria are often used to classify the severity of the illness:

• Stage 1 — suspected NEC (generally unwell with feed intolerance and/or non-specific abdominal signs, ±bloody stool, but no pneumatosis)
• Stage 2 — definite NEC (unwell with definite abdominal signs and pneumatosis)
• Stage 3 — advanced NEC (severely ill with shock, marked abdominal signs, and ascites or intestinal perforation).

In general terms, large-bowel NEC is a much more benign illness than small-bowel NEC.

The characteristic radiographic findings are pneumatosis intestinalis and portal venous gas. Pneumatosis intestinalis represents gas in the submucous layer produced by intestinal bacteria.

• There are three patterns of pneumatosis intestinalis:

— the circle of submucous gas in a cross-section of bowel viewed end on;
— a ‘tram-track’ appearance of submucous gas in bowel viewed in longitudinal section; and
— a ‘whorl’ pattern seen when looking through a bowel wall with pneumatosis in it.

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