Core Topics in General & Emergency Surgery: Companion to Specialist Surgical Practice (45 page)
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Authors: Simon Paterson-Brown MBBS MPhil MS FRCS
Radiation enteritis
Patients can present with an acute abdomen during radiotherapy due to radiation enteritis or with acute-on-chronic attacks many years later. Patients in the former scenario can present considerable diagnostic difficulties as they are often neutropenic or suffering other side-effects of their treatment. The possibility of a primary pathology, such as acute appendicitis, arising during the course of radiotherapy must also be borne in mind but, where possible, surgical exploration is best avoided.
A more common acute presentation is with adhesions due to previous radiotherapy and these patients normally have obstructive symptoms. Again, a non-operative management policy is the best course as laparotomy is fraught with difficulty. The adhesions are often dense and, if the small bowel is inadvertently injured, there is a significant risk that it might not heal whether it is repaired or anastomosed.
Primary tumours of the small bowel are rare but can be the cause of acute small-bowel obstruction: surgical management at laparotomy will depend on the exact nature of the disease.
A more common problem is the patient with advanced intra-abdominal malignancy, with or without a past history of surgical treatment for malignancy, who presents with bowel obstruction. If the obstruction fails to settle or rapidly recurs, there is usually time to carry out appropriate investigations to determine the extent of the disease prior to surgery. CT is important in identifying a single area of obstruction, which might be amenable to surgery, as compared to extensive intra-abdominal disease without a single point of obstruction.
Ascites can be a confusing factor in such a patient and aspiration for cytology to confirm widespread malignancy can be helpful. Clearly in the presence of advanced and disseminated malignancy laparotomy should be avoided at all costs. However, if the obstructive symptoms are difficult to manage non-operatively and the patient is otherwise in reasonable condition, a laparotomy may be useful in the short term. When surgery is necessary, the exact procedure will depend on the operative findings. The choice usually lies between resection and bypass.
It is also important to recognise that not all patients have obstruction due to their malignant process. One study of patients who presented with obstruction following previous treatment of intra-abdominal malignancy reported that in around one-third of such patients the obstruction was due to a cause other than secondary malignancy.
8
In a study from Japan of 85 patients who had previously undergone surgery for gastric cancer and who were subsequently re-admitted to hospital with intestinal obstruction, the cause was benign adhesions in 20%.
9
The results of bypass entero-enterostomy for malignant adhesions are generally poor, with short periods of patient survival. For this reason there is growing expertise among palliative care physicians in the medical management of intestinal obstruction.
10
The principles involve the use of fluid diet, steroids and octreotide. The results of such management are variable but it does offer the opportunity to spare a patient the morbidity of laparotomy in the terminal phase of their disease.
Any hernia can present with intestinal obstruction (
Figs 9.2
and
9.3
) and if presentation is delayed, gangrene may have occurred and a bowel resection may be necessary. A Richter hernia involves part of the circumference of the bowel wall and the lumen is not obstructed. Infarction of the trapped bowel wall segment can still occur and there will be exquisite localised tenderness over a potential hernia site; the indication for surgical intervention is usually clinically apparent.
Figure 9.2
Supine abdominal radiograph demonstrating small-bowel obstruction in a patient with an irreducible femoral hernia.
Figure 9.3
Multislice CT image with intravenous contrast demonstrating small-bowel obstruction secondary to a left-sided Spigelian hernia.
Any patient with acute symptoms of a hernia that is irreducible should have urgent surgery, with repair carried out in the usual way. In the presence of obstruction necessitating bowel resection, it is probably best to avoid the use of a prosthetic mesh if possible. When there has been gross contamination of the surrounding area, the risk of complications is increased and a full treatment course of antibiotics should be given. In most cases, a direct approach to the hernia is appropriate. For a strangulated femoral hernia a ‘high’ McEvedy approach usually provides optimum access for both hernia repair and bowel resection if required. The incarcerated tissue may reduce under anaesthesia and it is unlikely, should this occur, that there will have been strangulation. However, the bowel loops must be inspected from within the hernia sac to ensure that a gangrenous loop of bowel or a strictured segment has not dropped back into the abdominal cavity (see also
Chapter 4
).
A final consideration is the patient who has an asymptomatic hernia who develops acute intestinal obstruction and who then demonstrates signs of an apparently irreducible swelling in the site of the hernia. The intestinal obstruction raises intra-abdominal pressure and this will, in turn, produce the irreducible hernia. The unwary may find the hernia difficult to reduce and, in their efforts to do so, can elicit tenderness. It is worth obtaining a plain abdominal radiograph in all patients with an irreducible hernia and apparent bowel obstruction. The absence of dilated small-bowel loops, or the presence of a dilated colon, should suggest the possibility that the apparently ‘incarcerated’ hernia is a secondary effect of some other intra-abdominal pathology. If in doubt, a CT scan may help reach the correct diagnosis preoperatively and allow planning of surgery. In such cases consideration will need to be given for a formal laparotomy rather than a local approach over the hernia.
Enterolith obstruction is rare: the commonest types are gallstone ileus and bezoars.
Gallstone ileus
typically occurs in the elderly female and is due to the development of a cholecystoduodenal fistula after an episode of acute cholecystitis with ongoing chronic inflammation. The gallstone may be visible on a plain abdominal radiograph and gas can often be seen within the biliary tree. At surgery the stone should be removed via a proximal enterotomy and the intestine proximal to the obstruction carefully palpated to exclude the presence of a second stone. In these circumstances the gallbladder should be left alone, as cholecystectomy can be difficult and is usually unnecessary.
Bezoars
may arise in psychiatric patients, the normal population after over-indulging in particular types of food (e.g. oranges and peanuts), and those who have ingested a foreign body. Rarely, they can occur with material that is collected within a jejunal diverticulum.
In children, acute presentation is usually to the paediatric department and the main differential diagnosis is gastrointestinal (GI) infection. This is discussed in more detail in
Chapter 12
. Intussusception in adults is usually caused by tumours of the bowel, often metastatic deposits, which should be treated on their merits once detected at laparotomy.
There are several systemic connective tissue disorders that can affect the GI tract and result in a loss of peristaltic power. These patients generally present with chronic symptoms and the presence of the underlying disorder is established. Occasionally, symptoms suggesting acute GI obstruction are present and the differentiation between full mechanical obstruction and ileus can be difficult. Expectant management of these patients should be pursued whenever possible. The obstructed episode may progress to perforation of the bowel and if peritonitis is present, the perforated bowel should be resected and consideration given to bringing the proximal bowel out as an ileostomy, depending on the site and state of disease. In addition, postoperative ileus is common and the differentiation of a further episode of mechanical obstruction or continuing ileus presents a diagnostic challenge.
GI ileus can occur after any abdominal operation. The surgeon may also be asked to see patients who have undergone gynaecological, orthopaedic or cardiac procedures who have apparent bowel obstruction. Each case must be judged on its merits but the differentiation between true mechanical obstruction and paralytic ileus can be difficult. In patients who genuinely have a mechanical obstruction, appropriate surgical intervention is frequently delayed as a result of this diagnostic dilemma. In these patients, the use of water-soluble contrast small-bowel studies and contrast-enhanced CT is often helpful and should be considered early.
11
Following the development of laparoscopic surgery, there have been reports regarding the use of laparoscopic surgery in the treatment of small-bowel obstruction.
12
,
13
Open surgery is the preferred method for surgical treatment of strangulating small-bowel obstruction as well as after failed non-operative management. However, in selected patients and with appropriate surgical skills, a laparoscopic approach can be attempted using an open access technique. Laparoscopic adhesiolysis may be suitable during a first episode of small-bowel obstruction, particularly when there has been limited previous surgery and/or a single band is anticipated, such as might occur in a patient who has previously had an appendicectomy but no other major abdominal surgery (
Fig. 9.4
). A low threshold for open conversion should be maintained.
6
,
12
Figure 9.4
Laparoscopic view of a band adhesion.
With thanks to Luigi Sussman, Auckland, New Zealand.
Small-bowel pathology may present as an acute abdomen, with either localised or generalised peritonitis. This may represent the end-stage of any condition causing obstruction, but this section considers conditions that present with primarily inflammatory signs.
Crohn's disease is a chronic relapsing inflammatory disease that can affect any part of the GI tract. A common presentation is inflammation of the terminal ileum and this occasionally presents as an acute abdomen. The small bowel alone is affected in approximately 30% of patients and the small bowel and colon together in 50%. The incidence of Crohn's disease is highest in the USA, the UK and Scandinavia and is rare in Asia and Africa, suggesting that dietary factors may be important. Similar to appendicitis, the disease can appear at any age but is most frequent in young adults and there may be a familial tendency. It is thought that the disease is most likely due to an immunological disorder, although the exact mechanism remains unclear although the final pathway is probably a microvasculitis in the bowel wall. Where possible, the management of patients with Crohn's disease should be undertaken by a surgeon with a special interest in this condition and the reader is referred to the much more detailed account of this disease in the
Colorectal Surgery
volume of the
Companion to Specialist Surgical Practice
series.
14
Only first principles for managing an acute episode are discussed in this chapter.
An acute clinical episode typically presents with abdominal pain, diarrhoea and fever, and can occur in a patient who has previously been entirely well. An acute presentation is more likely in young adults, hence the differential diagnosis of Crohn's disease in patients with suspected appendicitis.
Two other clinical presentations occur, although they are less likely to be acute. First, resolving Crohn's disease will produce fibrosis in the ileum that can cause obstructive symptoms. These tend to be subacute or chronic and an acute presentation with small-bowel obstruction is rare. Second, entero-enteric or enterocutaneous fistula occurs in Crohn's disease because of the transmural inflammation that is a characteristic histological finding.
A patient who presents with right iliac fossa pain, with symptoms that are more insidious than typical appendicitis, should give rise to clinical suspicion. Inflammatory markers may be markedly elevated (white cell count, platelet count, alkaline phosphatase, erythrocyte sedimentation rate), but these are not specific to Crohn's disease. An ultrasound scan may show thickening of the bowel wall or a mass, and contrast-enhanced CT will provide more detailed information.
If a patient with known Crohn's disease presents with an acute flare-up, or during first presentation the diagnosis of Crohn's disease is established before surgery, the patient should be referred to a surgeon with a special interest in this condition.
15
However, the diagnosis may only be suspected at the time of operation, and the surgeon must proceed according to first principles. In the presence of a localised inflammatory mass or stricture, resection and primary anastomosis may be appropriate. If surgery has been carried out for suspected appendicitis and a normal appendix with ileocaecal Crohn's disease is discovered, the appendix should be removed with careful repair of the caecum, so that the possible diagnosis of acute appendicitis is ruled out of any future attacks of pain. No further action needs to be taken at this time for the Crohn's disease and appropriate investigation and treatment can be initiated in the postoperative period. Fortunately, extensive small-bowel Crohn's disease is an uncommon finding at laparotomy, but in this situation the bare minimum should be carried out. If a stricture is found it should be resected, to treat the problem and to confirm the diagnosis. If multiple strictures are found multiple stricturoplasties can be carried out, with full-thickness biopsies taken for histology. The differential diagnosis of lymphoma should also be considered.
Mesenteric ischaemia can be due to embolism or thrombosis, arterial or venous, and may be acute or chronic. Chronic mesenteric ischaemia is also termed ‘mesenteric claudication’ and is usually caused by a stenosis in the proximal part of the superior mesenteric artery. Patients develop cramp-like abdominal pains after eating, caused by the increased oxygen requirements to the small intestine, which cannot be met by increased blood flow because of the stenosis. The disease is usually associated with atherosclerosis and the investigation of choice is mesenteric angiography. This condition is discussed in more detail in the
Vascular and Endovascular Surgery
volume of the
Companion to Specialist Surgical Practice
series and is not discussed further here. These patients should be transferred to a specialist vascular surgeon.
Acute mesenteric ischaemia can affect any part of the GI tract, but is most common in the small bowel and colon. Acute ischaemia to the small bowel will usually produce infarction, whereas ischaemia to the large bowel presents with bloody diarrhoea and abdominal pain, which will usually settle over the course of a few days and is often termed ‘ischaemic colitis’. Delayed strictures may occur.
Acute small-bowel ischaemia is caused by either thrombosis or embolus. Thrombosis may occur in the superior mesenteric artery or its branches, usually associated with underlying atherosclerosis. Embolus is often associated with atrial fibrillation, when an atrial thrombus dislodges and impacts itself in the superior mesenteric artery distribution. Venous thrombosis in the distribution of the superior mesenteric vein is a less common cause of acute small-bowel ischaemia but may be related to increased blood coagulability, portal vein thrombosis, dehydration, infection, compression and vasoconstricting drugs.
Early detection of acute mesenteric ischaemia is difficult (see
Chapter 5
) and failure to detect this condition early continues to be one of the major causes of morbidity and mortality. The diagnosis is more common in the elderly patient who gives a history of vague but worsening abdominal pain. There may be a background history of atherosclerosis, but not invariably so. Initial examination findings can be unremarkable, lulling the clinician into a false sense of security.
The investigations for possible mesenteric ischaemia are discussed in detail in
Chapter 5
. CT with intravenous contrast performed as a diagnostic test for the ‘acute abdomen’ may suggest the diagnosis, but CT angiography (
Fig. 9.5
) is more useful if the diagnosis is suspected. Patients in whom a diagnosis is suspected should be resuscitated and prepared for laparoscopy or laparotomy. Once the diagnosis has been confirmed, a decision must be made as to whether the ischaemic bowel is salvageable by vascular reconstruction. If the underlying cause is thrombosis, then resection should be performed; however, if an embolus is present, then in selected patients exploration of the superior mesenteric artery with removal of the embolus may save an extended small-bowel resection.
16
This procedure is difficult and may require associated vascular reconstruction. Advice should be sought from a specialist vascular surgeon.
Figure 9.5
Multislice CT image with intravenous contrast demonstrating ischaemic bowel due to superior mesenteric vein thrombosis. With thanks to Dr Dilip Patel, Consultant Radiologist, Royal Infirmary, Edinburgh.
If surgical resection is carried out, primary anastomosis may be performed, providing the blood supply to both proximal and distal margins is adequate. If embolectomy and reconstruction have been performed, or there is doubt about the margins, then anastomosis should be deferred. In this situation the distal and proximal ends of bowel should be stapled off and returned to the abdomen, with re-exploration planned within 48 hours. At re-operation an anastomosis may be performed or the ends brought out as stomas if anastomosis is contraindicated. Attention must be given in the postoperative period to the general condition of the patient in order that any possible secondary ischaemic event can be detected early.
Unfortunately, for the majority of patients with mesenteric ischaemia the small intestine is beyond salvage at the time of laparotomy and requires resection. If the whole of the superior mesenteric artery has been affected, the majority of the small bowel and part of the proximal colon will often be involved and no resection should be performed. These patients should receive intravenous opiates and be kept well sedated, as death will occur shortly afterwards.
Overall prognosis is better following acute mesenteric venous infarction as compared to acute mesenteric arterial ischaemia, and survival better following arterial embolism as compared to arterial thrombosis.
17
Meckel's diverticulum is a remnant of the omphalomesenteric or vitelline duct. It arises from the antimesenteric border of the distal ileum approximately 60 cm from the iliocaecal valve. It may contain ectopic tissue, usually gastric, and is estimated to be present in approximately 2% of the population. Meckel's diverticulum may remain asymptomatic throughout life, particularly if it has a broad base and does not contain ectopic gastric mucosa. Occasionally, a band may exist between Meckel's diverticulum and the umbilicus, which can cause small-bowel obstruction. This should be treated as for a congenital band adhesion, although resection of the diverticulum should accompany division of the band. Occasionally, the diverticulum may intussuscept, also causing obstruction. Again, this will require reduction and excision. The other two common complications of Meckel's diverticulum are inflammation, when the patient presents with signs and symptoms similar to acute appendicitis, and haemorrhage. Acute inflammation is rarely suspected before surgery and the patient is usually diagnosed on the operating table (
Fig. 9.6a
) once a normal appendix has been found through a right iliac fossa incision or at laparoscopy. In the presence of inflammation, a Meckel's diverticulum should be excised and the small bowel repaired (
Fig. 9.6b
). Occult GI bleeding may occur from a Meckel's diverticulum that contains ectopic gastric mucosa and the diagnosis is usually established by CT angiogram. The treatment is again surgical resection.
Figure 9.6
(a)
Acutely inflamed Meckel's diverticulum identified at laparotomy.
(b)
Operative view after resection of the Meckel diverticulum shown in (a).