Clinical Features of Intestinal Obstruction 1

The diagnosis of dynamic intestinal obstruction is based on the classic quartet of: pain, distension, vomiting & absolute constipation. pain, distension, vomiting & absolute constipation. Obstruction may be classified clinically into 2 types: * Small bowel obstruction: high or low. * Small bowel obstruction: high or low. * Large bowel obstruction. * Large bowel obstruction. 2

Features of obstruction: * In high small bowel obstruction: Vomiting occurs early, is profuse & causes rapid dehydration. Distension is minimal with little evidence of dilated small bowel loops on abdominal radiography. 3

* In low small bowel obstruction: pain is predominant with central distension. Vomiting is delayed. Multiple dilated small bowel loops are seen on radiography. 4

* In large bowel obstruction: distension is pronounced. Pain is less severe and vomiting and dehydration are late. The colon proximal to the obstruction is distended on abdominal radiography. The small bowel will be dilated if the ileocaecal valve is incompetent. 5

Presentation influenced by whether the obstruction is: Complete or Incomplete. Complete or Incomplete. Complete SBO has all the cardinal features: Abdominal pain, Distension, Vomiting, Absolute constipation). 6

Presentation will be either: Simple: (when blood supply is intact) or Strangulating/strangulated: (when there is interference to blood flow). 7

The clinical features vary according to:The clinical features vary according to: * The location of the obstruction. * The location of the obstruction. * The duration of the obstruction. * The duration of the obstruction. * The underlying pathology. * The underlying pathology. * The presence or absence of intestinal ischaemia. * The presence or absence of intestinal ischaemia. In all cases of suspected intestinal obstruction, the hernial orifices must be examined. 8

Late manifestations of IO include: dehydration,oliguria, hypovolaemic shock, pyrexia,septicaemia, respiratory embarrassment and peritonism. 9

Pain: first symptom, occurs suddenly & is usually severe. first symptom, occurs suddenly & is usually severe. It is colicky in nature & centred on the umbilicus (small bowel) or lower abdomen (large bowel). The pain coincides with increased peristaltic activity. With increasing distension, the colicky pain is replaced by a mild and more constant diffuse pain. 10

If there is no ischaemia and the obstruction persists over several days, pain reduces & can disappear. The development of severe pain is suggestive of strangulation, especially if that severe pain is continuous & if not controlled with opiates. Colicky pain not a significant feature in postoperative simple mechanical obstruction and pain does not occur in paralytic ileus. 11

Vomiting: The more distal the obstruction, the longer the interval between the onset and the appearance of nausea and vomiting. As obstruction progresses, the character of the vomitus alters from digested food to faeculent material, as a result of enteric bacterial overgrowth 12

Distension: Distension: In the small bowel, the degree of distension is dependent on the site of the obstruction & is greater the more distal the lesion. Visible peristalsis may be present. This can sometimes be provoked by ‘flicking’ the abdominal wall. 13

Visible peristalsis. Intestinal obstruction due to a strangulated right femoral hernia 14

Constipation: may be absolute ( neither faeces nor flatus is passed) or relative (where only flatus is passed). Absolute constipation is a cardinal feature of complete intestinal obstruction. patient may pass flatus or faeces after the onset of obstruction as a result of the evacuation of the distal bowel contents. 15

The administration of enemas should be avoided in cases of suspected obstruction. This only stimulates evacuation of bowel contents distal to the obstruction and confuses the clinical picture. 16

The rule that absolute constipation is present in intestinal obstruction does not apply in: 1- Richter's hernia. 2- Gallstone ileus. 3- Mesenteric vascular occlusion. 4- Functional obstruction associated with pelvic abscess. 5- Partial obstruction (in which diarrhoea may occur). 17

Other Manifestations of Intestinal Obstruction are: 18

- Dehydration:- Dehydration: seen most commonly in SBO because of repeated vomiting and fluid sequestration. It results in: dry skin & tongue, poor venous filling sunken eyes oliguria. blood urea level & haematocrit rise, giving a secondary polycythaemia. 19

- Hypokalaemia:- Hypokalaemia: not a common feature in simple mechanical obstruction. An increase in: serum potassium, amylase or lactate dehydrogenase may be associated with the strangulation. 20

- Pyrexia:- Pyrexia: Pyrexia in obstruction is rare & may indicate: 1- the onset of ischaemia. 1- the onset of ischaemia. 2- intestinal perforation. 2- intestinal perforation. 3- inflammation or abscess associated with the obstructing disease. 3- inflammation or abscess associated with the obstructing disease. Hypothermia indicates septicaemic shock or neglected cases of long duration. Hypothermia indicates septicaemic shock or neglected cases of long duration. 21

- Abdominal tenderness:- Abdominal tenderness: Localised tenderness indicates impending or established ischaemia. The development of peritonism or peritonitis indicates impending or overt infarction and/or perforation. In LBO it is important to elicit these findings in the RIF as the caecum is most vulnerable to ischaemia. 22

- Bowel sounds:- Bowel sounds: High-pitched bowel sounds are present in the vast majority of patients with intestinal obstruction. Normal bowel sounds are of negative predictive value. Bowel sounds may be scanty or absent if the obstruction is long-standing. 23

Clinical Features of Strangulation 24

It is vital to distinguish: strangulating from non-strangulating IO strangulating from non-strangulating IO because strangulation is a surgical emergency. The diagnosis is almost entirely clinical: 1- Constant pain, severe pain. 2- Tenderness with rigidity and peritonism. 3- Shock. 25

Additional features of strangulation: * shock: suggests underlying ischaemia especially if the shock is resistant to simple fluid resuscitation. * pain: is never completely absent. * local tenderness: are of great significance and, 26

* Generalised tenderness & rigidity is indication for early laparotomy. * IO in which pain persists despite conservative management, strangulation should be suspected. * if strangulation in external hernia, the lump is: - tense, tender and irreducible - and there is no expansile cough impulse. - Skin changes with erythema or purplish discolouration are associated with underlying ischaemia. 27

Skin discolouration over a strangulated incisional hernia 28

Ischaemic small and large bowel in the strangulated incisional hernia. 29

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Clinical Features of Volvulus 31

* Volvulus of the small intestine:* Volvulus of the small intestine: primary or secondary & occurs in the lower ileum. It may occur spontaneously in African people, particularly following the consumption of a large volume of vegetable matter, whereas in the West, it is usually secondary to adhesions passing to the parietes or female pelvic organs. 32

* Caecal volvulus:* Caecal volvulus: is usually a clockwise twist. It is common in females in the 4 th & 5 th decades. Presents acutely with classic features of obstruction. Ischaemia is common. examination may reveal a palpable tympanic swelling in the midline or left side of the abdomen. The volvulus typically results in the caecum lying in the left upper quadrant. The diagnosis is not usually made preoperatively. 33

* Sigmoid volvulus:* Sigmoid volvulus: The symptoms are of large bowel obstruction. Presentation varies in severity and acuteness, with younger patients appearing to develop the more acute form. Abdominal distension is an early and progressive sign, which may be associated with hiccough & retching. Constipation is absolute. Constipation is absolute. In the elderly, a more chronic form may be seen. In the elderly, a more chronic form may be seen. In some patients, the grossly distended torted left colon is visible through the abdominal wall. 34

IMAGING 35

Erect abdominal films are no longer routinely obtained and the radiological diagnosis is based on a supine abdominal film. An erect film may subsequently be requested when further doubt exists. 36

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Radiological features of obstruction (on plain x-ray): 38

The obstructed small bowel is characterised by: The obstructed small bowel is characterised by: * straight segments that are generally central and lie transversely. No/minimal gas is seen in the colon * The jejunum: characterised by its valvulae conniventes, which completely pass across the width of the bowel & are regularly spaced, giving a ‘concertina’ effect. * Ileum: is featureless. 39

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* Caecum : rounded gas shadow in the RIF. * Large bowel: except the caecum, shows haustral folds, which, unlike valvulae conniventes, are spaced irregularly, do not cross the whole diameter of the bowel and do not have indentations placed opposite one another 41

In IO fluid levels appear later than gas shadows as it takes time for gas and fluid to separate. fluid levels are prominent on erect film. When fluid levels are pronounced, the obstruction is advanced. In the small bowel, the number of fluid levels is directly proportional to the degree of obstruction and to its site, the number increasing the more distal the lesion. 42

In adults, two inconstant fluid levels – one at the duodenal cap and the other in the terminal ileum, regarded as normal. In infants (less than one year old), a few fluid levels in the small bowel may be physiological. 43

In patients without evidence of strangulation, there is a role for other imaging modalities: The diagnostic and therapeutic role of 50–100 mL water-soluble contrast agent in adhesive SBO. The appearance of contrast in the colon 4–24 hours after administration. If contrast does not reach the colon, surgery is required in about 90 % of patients. low colonic obstruction does not give rise to small bowel fluid levels unless advanced, but high colonic obstruction may do so in the presence of an incompetent ileocaecal valve. low colonic obstruction does not give rise to small bowel fluid levels unless advanced, but high colonic obstruction may do so in the presence of an incompetent ileocaecal valve. 44

Colonic obstruction is usually associated with a large amount of gas in the caecum. A barium follow-through is contraindicated in the presence of acute obstruction and may be life- threatening. Fluid levels may also be seen in non-obstructing conditions such as gastroenteritis, acute pancreatitis and intra-abdominal sepsis. 45

CT scan is now used very widely to investigate all forms of intestinal obstruction. It is highly accurate and its only limitations are in diagnosing ischaemia. Impacted foreign bodies may be seen on abdominal radiographs 46

Imaging in volvulus 47

* In caecal volvulus:* In caecal volvulus: radiological abnormalities are non-specific, with: Caecal dilatation (98–100 %), Single air-fluid level, Small bowel dilatation Absence of gas in distal colon are most common abnormalities. A barium enema may be used to confirm the diagnosis if there are no ischaemia, with: - absence of barium in the caecum - and a bird beak deformity. CT scanning is replacing barium enema. 48

* In sigmoid volvulus:* In sigmoid volvulus: a plain radiograph shows massive colonic distension. The classic appearance is: - dilated loop of bowel, the 2 limbs are seen running diagonally across the abdomen from Rt to Lt, - with two fluid levels seen, one within each loop of bowel (if an erect film is taken). 49

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TREATMENT OF ACUTE INTESTINAL OBSTRUCTION 51

three main measures for treatment of acute IO: 1- Gastrointestinal drainage via a nasogastric tube: - For facilitating decompression proximal to the obstruction, - Essential to reduce the risk of subsequent aspiration during anaesthesia. 52

2- Fluid and electrolyte replacement: The basic biochemical abnormality in IO is sodium & water loss, and therefore the appropriate replacement is Hartmann's solution or normal saline. The volume required should be determined by: Clinical, haematological & biochemical criteria. 53

3- Relief of obstruction: Surgical treatment is necessary for most cases of IO but should be delayed until resuscitation is complete, provided there is no sign of strangulation. 3 principles of surgical intervention are management of: 1- The segment at the site of obstruction. 2- The distended proximal bowel. 3- The underlying cause of obstruction. 54

** Antibiotics are not mandatory but we give broad- spectrum antibiotics early in therapy because of bacterial overgrowth. * Antibiotic therapy is mandatory for all patients undergoing surgery for intestinal obstruction. 55

Indications for early surgical intervention are: 1- Obstructed external hernia. 2- Clinical features suspicious of intestinal strangulation. 3- Obstruction in a ‘virgin’ abdomen. 56

The classic clinical advice that: ‘the sun should not both rise and set’ ‘the sun should not both rise and set’ on a case of unrelieved acute IO was based on the concern that intestinal ischaemia would develop while the patient was waiting for surgery. Where obstruction is likely to be secondary to adhesions, conservative management may be continued for up to 72 hours in the hope of spontaneous resolution. 57

The type of surgical procedure depend upon the cause of obstruction: division of adhesions (enterolysis), excision, bypass or proximal decompression. Following relief of obstruction, the viability of the involved bowel should be carefully assessed. 58

Differentiation between viable & non-viable intestine: 59

- When there are multiple ischaemic areas (mesenteric vascular occlusion), a second-look laparotomy at 24–48 hours may be required. 60

The surgical management of massive infarction is dependent on the patient's overall prognostic criteria. In the elderly, infarction of the small bowel from the duodenojejunal flexure to the right colon may be considered incurable. whereas in the young, with the potential for long-term intravenous alimentation and small bowel transplantation, excision may be justified. 61

Treatment of adhesions: Initial management is: IV rehydration & NG decompression; occasionally, this treatment is curative. IV rehydration & NG decompression; occasionally, this treatment is curative. Regular assessment is mandatory to ensure that strangulation does not occur. Conservative treatment should not prolonged beyond 72 hours. 62

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When laparotomy is required, although multiple adhesions may be found, only one may be causative. If there is absolute certainty that this is the cause of the obstruction, this should be divided and the remaining adhesions can be left in situ unless severe angulation is present. Division of these adhesions will only cause further adhesion formation. Division of these adhesions will only cause further adhesion formation. Laparoscopic adhesiolysis may be considered in highly selected cases of small bowel obstruction. 64

Postoperative intestinal obstruction Differentiation between persistent paralytic ileus and early mechanical obstruction may be difficult in early postoperative period. Mechanical obstruction is more likely if the patient has regained bowel function postoperatively which subsequently stops. 65

Obstruction is usually incomplete and the majority settle with continued conservative management. Postoperative intra-abdominal sepsis is a potent cause of postoperative obstruction. CT scanning is of particular value in the assessment of the postoperative abdomen. 66

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