Small bowel obstruction according to Bailey and love

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Small Bowel Obstruction - Bailey and Love's Short Practice of Surgery (28th Edition, Chapter 78)

Classification

Intestinal obstruction is classified into two types:

Dynamic (mechanical): peristalsis works against a mechanical obstruction. May be acute or chronic.
Adynamic: no mechanical obstruction; peristalsis is absent or inadequate (e.g. paralytic ileus, pseudo-obstruction).

Causes of Small Bowel Obstruction

Figure 78.1 - Common causes and relative frequencies of intestinal obstruction

Figure 78.1 - Relative frequencies of causes of intestinal obstruction (Bailey & Love, Ch. 78)

By location of the obstruction:

Category	Examples
Intraluminal	Faecal impaction, foreign bodies, bezoars, gallstones
Intramural	Stricture, malignancy, intussusception, volvulus
Extramural	Bands/adhesions, hernia

Adhesions account for ~40% of cases; inflammatory causes (e.g. Crohn's disease) 15%; carcinoma 15%; obstructed hernia 12%; faecal impaction 8%.

Pathophysiology

In mechanical (dynamic) obstruction:

Bowel proximal to the obstruction dilates; bowel distal empties and collapses.
Initially, peristalsis increases to overcome obstruction; if unrelieved, the bowel continues to dilate, eventually becoming flaccid and paralysed.

Two main factors cause proximal distension:

Gas: Bacterial overgrowth produces gas, predominantly nitrogen (90%) and hydrogen sulphide.
Fluid accumulation: Approximately 3 litres of digestive juice enters the gut per day (saliva 500 mL, bile 500 mL, pancreatic secretions 500 mL, gastric secretions 1 litre). This accumulates as absorption is retarded.

Causes of dehydration and electrolyte loss:

Reduced oral intake
Defective intestinal absorption
Vomiting
Sequestration in the bowel lumen
Transudation of fluid into the peritoneal cavity

Strangulation

Strangulation is the most dangerous complication, when the blood supply to the obstructed bowel is compromised.

Causes of strangulation:

Mechanism	Cause
Direct pressure on bowel wall	Hernial orifices, adhesions/bands
Interrupted mesenteric blood flow	Volvulus, intussusception
Increased intraluminal pressure	Closed-loop obstruction

The sequence: venous return is compromised first → raised capillary pressure → impaired local perfusion → arterial supply impaired → haemorrhagic infarction. Bacteria and toxins pass through the ischaemic wall into the peritoneal cavity, causing peritonitis.

Cardinal Clinical Features

The four cardinal features of acute intestinal obstruction (Summary box 78.7):

Abdominal pain
Distension
Vomiting
Absolute constipation

Features vary by level

Feature	High SBO	Low SBO	Large Bowel
Vomiting	Early, profuse, rapid dehydration	Later, faeculent	Late
Distension	Minimal	Central (periumbilical)	Pronounced, early
Pain	Predominant, periumbilical	Severe, colicky	Less severe
Radiograph	Minimal dilated loops	Multiple dilated loops centrally	Colon distended

Pain

First symptom; sudden onset, severe
Colicky, centred on the umbilicus in small bowel obstruction
Coincides with peristaltic waves
As distension increases, colicky pain is replaced by constant diffuse pain
If obstruction persists without ischaemia, pain may diminish

Vomiting

In high SBO: immediate, profuse; initially gastric contents, then bile-stained
In low SBO: delayed and faeculent (reflux of bowel contents)

Distension

Absent in high obstruction; central/periumbilical in low SBO
Visible peristalsis ("ladder pattern") may be seen in thin patients

Absolute constipation

A reliable sign once bowel contents distal to obstruction are evacuated
NOT present in: Richter's hernia, gallstone ileus, mesenteric vascular occlusion, functional obstruction with pelvic abscess, all partial obstructions (where diarrhoea may occur)

Other Manifestations

Dehydration: Seen especially in SBO due to repeated vomiting and fluid sequestration. Signs: dry skin/tongue, poor venous filling, sunken eyes, oliguria. Blood urea and haematocrit rise.
Hypokalaemia: Not common in simple mechanical obstruction. Raised serum potassium, amylase, or lactate dehydrogenase - and leukocytosis or leukopenia - may indicate strangulation.
Pyrexia: Suggests ischaemia onset, intestinal perforation, or inflammation/abscess from the obstructing disease. Hypothermia indicates septicaemic shock.
Abdominal tenderness: Localised tenderness = impending ischaemia. Peritonism/peritonitis = infarction/perforation.

Clinical signs of strangulation (Bailey & Love):

Presence of shock suggests underlying ischaemia
In impending or established strangulation, pain is never completely absent
Localised tenderness requires frequent reassessment
Generalised tenderness and rigidity indicate the need for early laparotomy
When pain persists despite conservative management, strangulation should be presumed
In external hernia: lump is tense, tender, irreducible with no expansile cough impulse; erythema or purple discolouration of overlying skin indicates ischaemia

Special Types of Mechanical SBO

Closed-Loop Obstruction

Occurs when both ends of a bowel loop are obstructed (e.g. a band compressing a loop). This is life-threatening because the closed segment cannot decompress proximally. Strangulation risk is high.

Adhesive Intestinal Obstruction

The most common cause. Adhesions form after previous abdominal surgery or peritoneal inflammation. Most resolve with conservative management. Conservative treatment should not be prolonged beyond 72 hours. At operation:

If a single causative adhesion is found, divide that only
Multiple adhesions: dissect from duodenojejunal junction to caecum
Serosal injuries should be repaired or oversewn with absorbable seromuscular sutures
Laparoscopic adhesiolysis may be considered in highly selected cases but is an advanced procedure

For recurrent obstruction from adhesions, options include: repeat adhesiolysis (enterolysis), Noble's plication, Childs-Phillips transmesenteric plication, or intestinal intubation (the last three are now rarely performed).

Obstruction from Enteric Strictures (Crohn's Disease)

Subacute/chronic presentation. Management: resection and anastomosis to establish histological diagnosis. Strictureplasty may be considered for short multiple strictures in Crohn's disease without active sepsis.

Bolus Obstruction

Causes: gallstones, food, trichobezoar, phytobezoar, stercoliths, worms.

Gallstone ileus: Elderly patients. A large gallstone erodes through the gallbladder into the duodenum and impacts ~60 cm proximal to the ileocaecal valve. Rigler's triad on AXR: SBO + pneumobilia + ectopic gallstone shadow (pathognomonic when 2 of 3 present, seen in 40-50%). At laparotomy, milk the stone proximally, crush or enterotomy; check for additional stones if faceted. Do not explore the gallbladder region.
Food bolus: After partial/total gastrectomy. Intraluminal crushing usually successful.
Bezoars: Trichobezoar (hair) from hair chewing - may indicate psychiatric disorder. Phytobezoar (fruit/vegetable fibre) associated with high fibre intake, previous gastric surgery, hypochlorhydria.

Acute Intussusception

One bowel segment invaginates into the adjacent segment - invariably proximal into distal.
Most common in infants aged 5-10 months; 90% idiopathic (hyperplasia of Peyer's patches as initiating event)
In adults: almost invariably has a lead point (polyp, Peutz-Jeghers, submucosal lipoma)
Classic presentation in infants: episodes of screaming and drawing up of legs, pale, listless between attacks, vomiting, then "redcurrant jelly" stool (blood and mucus)
Examination: sausage-shaped lump in right upper abdomen with concavity toward umbilicus, sign of Dance (emptiness in right iliac fossa), blood-stained mucus on PR

Investigations

Blood tests

FBC: leukocytosis may indicate strangulation
U&E: assess dehydration and electrolytes
Raised amylase, lactate dehydrogenase, serum potassium: associated with strangulation

Radiology

Plain AXR (erect and supine):

SBO: central dilated loops with valvulae conniventes (haustrations absent), air-fluid levels in step-ladder pattern
Gasless abdomen in strangulated obstruction or proximal high SBO
Rigler's triad in gallstone ileus

CT scan:

Now the imaging of choice for diagnosing SBO and identifying the cause
Can identify site, level, and aetiology
Can detect strangulation (loss of mural enhancement, mesenteric oedema)
For intussusception: "target" or "sausage"-shaped soft-tissue mass with layering; diagnostic accuracy 58-100%

Ultrasound:

High diagnostic sensitivity for intussusception in children (doughnut/concentric ring appearance in transverse section)

Treatment

Three main measures (Summary box 78.11):

Gastrointestinal drainage via nasogastric tube (NG decompression)
Fluid and electrolyte replacement (IV resuscitation)
Relief of obstruction

Surgical treatment is necessary for most cases but should be delayed until resuscitation is complete, provided there is no sign of strangulation or evidence of closed-loop obstruction.

Conservative Management

NG tube drainage + IV fluid resuscitation
Appropriate for adhesive SBO where strangulation is excluded
Should not be continued beyond 72 hours
Any deterioration, persistent pain, rising inflammatory markers, or failure to resolve = proceed to surgery

Surgical Indications (emergency/urgent laparotomy):

Signs of strangulation (persistent pain, tenderness, fever, shock)
Closed-loop obstruction
Failure of conservative management
Generalised peritonitis or peritonism
Irreducible hernia with obstructed bowel

Operative approach:

Divide causative adhesion(s)
Assess bowel viability; non-viable bowel must be resected
Doubtful viability: invaginate with seromuscular suture or resect
Laparoscopic approach: possible in selected cases by experienced surgeons

Bailey and Love's Short Practice of Surgery, 28th Edition - Chapter 78: Intestinal Obstruction

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