The Acute Abdomen and Acute Gastrointestinal Haemorrhage

Introduction

The term acute abdomen is widely understood but is difficult to define precisely. Typically, the symptoms are of acute onset abdominal pain. The illness is of such severity that admission to hospital appears essential and operative surgery is a likely outcome. Many of the disorders causing an ‘acute abdomen’ are serious and potentially life threatening unless treated promptly. On the other hand, simple and relatively trivial conditions, such as constipation can produce acute and severe symptoms mimicking the early stages of an acute abdomen.

Major gastrointestinal (GI) haemorrhage is also a common reason for acute surgical referral, and is manifest by vomiting of blood ( haematemesis ), profuse rectal bleeding or the passage of melaena . Many such patients are initially referred to a general (internal) physician or gastroenterologist, especially if the presumptive diagnosis is of bleeding from a peptic ulcer or oesophageal varices.

Acute surgical emergencies constitute about 50% of all general surgical admissions. About half of these are for abdominal symptoms, predominantly pain, and half of those in this group resolve without operation.

Basic Principles of Managing the Acute Abdomen

The first goal is to resuscitate the patient with intravenous fluids and administer analgesia. The next is to make a diagnosis based on the history, examination, laboratory tests and imaging ( Box 19.1 ). Together these will help decide if an operation is necessary, its urgency, and clarify any nonsurgical treatment, for example, antibiotics for diverticulitis or conservative measures for acute pancreatitis. Most of the time, it will only be possible to make a differential diagnosis rather than a definitive diagnosis.

BOX 19.1

Plain Radiology in the Acute Abdomen—What to Look for

Five Main Image Densities are Detectable on Radiographs

White—metallic objects
Off white—calcified structures
Medium shades of grey—most soft tissues
Dark grey—fat
Black—gas

How to Review an Abdominal X-ray:

1
. Check name is correct and date is current.
2
. Note type of x-ray , that is, plain or contrast, erect or supine.
3
. Is the image of adequate diagnostic quality , that is, appropriate density? Does it show the whole abdomen?
4
. Bowel gas and bowel wall —note distribution and dilatation (small bowel diameter less than 3 cm, most large bowel less than 5 cm, caecum less than 9 cm). Absence of gas may indicate a displacing mass, ascites (central) or acute pancreatitis (ground glass appearance). Faeces appear mottled; ‘faecal loading’ may mean constipation or obstruction. Rigler sign is strongly suggestive of bowel perforation.
5
. Non-bowel gas —free intraperitoneal gas, for example, subphrenic gas in perforation of bowel, gas within bowel wall in necrosis, gas in biliary tree after sphincterotomy or fistula of gall bladder into bowel.
6
. Calcification —aortic wall in aneurysm; pancreatic, renal and ureteric stones; gallstones; pelvic phleboliths (calcified old venous thrombi); teratomas and foetus. Bones of spine and pelvis—osteoarthritis, metastases (lytic or sclerotic), Paget disease, fractures.
7
. Soft tissues. Thickened bowel wall. Check outline of kidneys (are both present? Length equal to three or more vertebral bodies) and psoas muscles (obscured in retroperitoneal inflammation).
8
. Artefacts —artificial objects placed by medical personnel—central venous line, nasogastric tube, metal vessel or Fallopian tube clips, biliary, vascular or bowel stents, inferior vena caval filter, intrauterine contraceptive device.
- —
  foreign bodies—embedded bullets, glass fragments, objects inserted rectally
- —
  projection of buttons, safety pins, rings on hand, coins, body piercing

In Patients with an Acute Abdomen, Always Review Chest X-Ray for the Following:

hiatus hernia
heart size
lung fields
pneumothorax
diaphragms: relative height; gas under•bony changes
central venous pressure line position

Disorders and Diseases Causing the Acute Abdomen

Intestinal Obstruction

Pathophysiology of Intestinal Obstruction

Any part of the GI tract may become obstructed and present as an acute abdomen. Gastric outlet obstruction, however, presents differently and is described in Chapter 21 . The causes of intestinal obstruction are many and varied, as outlined in Fig. 19.1 .

Fig. 19.1, Mechanical Causes of Bowel Obstruction.

Obstruction leads to proximal dilatation of bowel and disrupts the peristalsis. The manner of presentation depends on the level of obstruction in the GI tract (i.e., stomach, proximal or distal small bowel or large bowel) and on the completeness of obstruction. The most acute presentation is upper small bowel obstruction. This manifests within hours of onset as the large volume of gastric and pancreaticobiliary secretions is prevented from progressing, and thus regurgitates into the stomach and is vomited. In contrast, distal large bowel obstruction is more insidious in onset and presentation may be delayed by as much as a week in many cases.

Symptoms of Intestinal Obstruction

Symptoms and physical signs are summarised in Box 19.2 .

BOX 19.2

Clinical Features of Bowel Obstruction and Strangulation

Symptoms

Vomiting—time of onset and nature of the vomitus suggest the level of obstruction
Absolute constipation (i.e., no flatus or faeces passed rectally)—pathognomonic of complete obstruction (but not present in partial obstruction)
Abdominal pain—usually colicky in character, often mild in uncomplicated obstruction and more severe in strangulation

Physical Signs

Dehydration—caused by vomiting, lack of fluid intake and fluid sequestration in obstructed bowel
Abdominal distension—caused by gas-filled loops of bowel. The more distal the obstruction, the greater the distension
Visible peristalsis—uncommon finding; usually encountered in a very thin patient with prolonged but incomplete distal small bowel obstruction
Abdominal tenderness—important feature distinguishing bowel strangulation from uncomplicated obstruction
Central resonance to percussion with dullness in the flanks—gas within dilated bowel loops rising to the uppermost point in the abdomen
Abnormal bowel sounds—exaggerated, lapping, sloshing, perhaps high-pitched or tinkling. Bowel sounds are absent or normal in adynamic obstruction

Vomiting

Bowel obstruction often presents as vomiting; the more proximal, the earlier it develops. Vomiting can occur even if nothing is taken by mouth because saliva and other GI secretions continue to be produced and enter the stomach. At least 10 litres of fluid are secreted into the GI tract each day. The nature of the vomitus gives clues about the level of obstruction. For example, vomiting of semidigested food eaten a day or two earlier suggests gastric outlet obstruction. Copious vomiting of bile-stained fluid suggests upper small bowel obstruction. If the vomitus becomes thicker and foul-smelling ( faeculent ), more distal obstruction is likely and this change is often an indication for urgent operation. The term faeculent is a misnomer as the vomitus contains altered small bowel contents rather than faeces itself.

Pain

Fluid and swallowed air proximal to an obstruction in combination with continuing peristalsis cause pain. The general area of the pain gives clues to the embryological origin of the segment of affected bowel: upper, middle or lower abdominal pain originates in foregut, midgut or hindgut, respectively. In obstruction, pain may not always be the most prominent symptom. However, when it does occur, it is usually colicky, occurring in short-lived bouts as peristalsis attempts to overcome the obstruction. In small bowel, the peristaltic action often increases for 24 to 48 hours after the onset of obstruction and then fades.

Constipation

Absolute constipation , that is, no faeces or flatus passed rectally, is pathognomonic of obstruction. The longer the duration, the more noteworthy it becomes in the diagnosis of obstruction.

Effects of Competence of the Ileocaecal Valve

Symptoms develop more gradually in large bowel obstruction because of the large capacity of colon and caecum and their absorptive capability. However, if the ileocaecal valve remains competent, no retrograde flow of accumulating bowel contents occurs and the thin-walled caecum progressively distends and eventually ruptures; operation is clearly more urgent in these cases. The ileocaecal valve becomes incompetent in about half the cases of large bowel obstruction. This allows the small bowel to distend, delaying the onset of obstructive symptoms and perhaps their acuteness.

Incomplete Obstruction

If bowel is partially obstructed, clinical features are less distinct. Vomiting may be intermittent and bowel habits erratic. Chronic incomplete obstruction leads to gradual hypertrophy of bowel wall muscle proximal to the obstruction and the strong peristaltic activity causes bouts of colicky pain, often more severe than in complete obstruction. In thin patients, the pain is often accompanied by visible peristalsis , the hallmark of incomplete obstruction. The most common cause is a slowly growing obstructing colonic cancer. Incomplete obstruction should not be called subacute obstruction as the term is misleading.

Physical Signs of Intestinal Obstruction

General Examination

Vomiting, diminished fluid intake and sequestration of fluid into the small bowel proximal to the obstruction, lead to dehydration . Gas-filled loops of bowel proximal to the obstruction produce abdominal distension ; the more distal the obstruction, the greater the distension. Examination may also reveal signs of anaemia or lymphadenopathy attributable to the primary disorder.

Groin Examination

It is essential that the groin is examined for hernias as the resulting bowel obstruction will not settle with conservative treatment. An obstructed femoral hernia is usually very small and rarely causes local symptoms or signs, even when strangulated. Hence it is easily missed if not specifically sought. Instead it produces the symptoms and signs of small bowel obstruction. This is an important clinical point—an obstruction caused by an irreducible hernia will not settle with the usual conservative treatment.

Abdominal Examination

On inspection , scars of previous operations provide a map of previous surgical disease, and raise the possibility of adhesive obstruction. On palpation , the most striking feature is the lack of abdominal tenderness except when strangulation has occurred. Obstruction with tenderness must be diagnosed as strangulation or perforation, necessitating urgent operation after fluid resuscitation. Note that a large obstructing abdominal mass may be palpable.

On percussion , the centre of the abdomen tends to be resonant and the periphery dull because bowel gas rises to the most nondependant point, mimicking ascites. On auscultation , obstructive bowel sounds are traditionally described as loud and frequent, high-pitched and tinkling; in practice, bowel sounds may or may not be increased but have an echoing, cavernous quality or else can sound like the lapping of water against a boat. A succussion splash , heard on gently shaking the patient’s abdomen from side to side, may be heard in gastric outlet obstruction.

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