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Intestinal Obstruction2

Learning Objectives• To understand:

• The pathophysiology of dynamic and adynamic intestinal obstruction

• ︎The cardinal features on history and examination

• ︎The causes of small and large bowel obstruction ︎

• The indications for surgery and other treatment options in bowel obstruction

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• Classification

• Pathophysiology

• Strangulation

• Special types of mechanical obstruction

• Clinical features of intestinal obstruction

• Imaging

• Treatment of acute intestinal obstruction

• Treatment of acute large bowel obstruction

• Chronic large bowel obstruction

• Adynamic obstruction

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Some definitions• obstruction [ uhb-struhk-shuhn ] noun

• something that obstructs, blocks, or closes up with an obstacle or obstacles; obstacle or hindrance: obstructions to navigation.

• Impaired normal flow on intestinal contents

• Dynamic or mechanical and adynamic or paralytic ileus

• Dynamic, in which peristalsis is working against a mechanical obstruction.

• Mechanical can be extrinsic of intrinsic; complete or partial

• Neurogenic failure of peristalsis results in paralytic ileus

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CausesMiscellaneous

5%Pseudo-obstruction

5%Fecal Impaction

8%Obstructed Hernia

12%

Inflammatory15% Carcinoma

15%

Adhesions40%

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Causes

✦ Intraluminal

• Faecal impaction

• Foreign bodies

• Bezoars

• Gallstones

✦ Intramural

• Stricture

• Malignancy

• Intussusception

• Volvulus

✦ Extramural

• Bands/adhesions

• Hernia

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Adynamic obstruction

• Paralytic ileus

• Pseudo-obstruction

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Pathophysiology• Proximal bowel dilates

• Distal bowel empties

• Proximal distension is due to

• Gas

• Fluid

• Dehydration and electrolyte imbalance occurs9

Strangulation• Causes of strangulation

• Direct pressure on the bowel wall

• Hernial orifices

• Adhesions/bands

• Interrupted mesenteric blood flow

• Volvulus

• Intussusception

• Increased intraluminal pressure

• Closed-loop obstruction

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Closed-loop obstruction

• Bowel obstructed at both the proximal and distal points

• Classic from is a malignant stricture of colon with a competent ileocecal valve

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INTEST INAL OBSTRUCT ION1182

– defective intestinal absorption; – losses as a result of vomiting; – sequestration in the bowel lumen; – transudation of fluid into the peritoneal cavity.

STRANGULATIONIt is important to appreciate that the consequences of intestinal obstruction are not immediately life-threatening unless there is superimposed strangulation. When strangulation occurs, the blood supply is compromised and the bowel becomes ischaemic (Summary box 70.2).

Summary box 70.2

Causes of strangulation ■ Direct pressure on the bowel wall

Hernial orificesAdhesions/bands

■ Interrupted mesenteric blood flowVolvulusIntussusception

■ Increased intraluminal pressureClosed-loop obstruction

Ischaemia from direct pressure on the bowel wall from a constricting band, such as a hernial orifice, is easy to understand.

Distention of the obstructed segment of bowel results in high pressure within the bowel wall. This can happen when only part of the bowel wall is obstructed as seen in Richter’s hernias. Venous return is compromised before the arterial supply. The resultant increase in capillary pressure leads to impaired local perfusion and once the arterial supply is impaired, haemorrhagic infarction occurs. As the viability of the bowel is compromised, translocation and systemic exposure to anaerobic organisms and endotoxin occurs.

The morbidity and mortality associated with strangulation are largely dependent on the duration of the ichaemia and its extent. Elderly patients and those with comorbidities are more vulnerable to its effects. Although in strangulated external her-nias the segment involved is often short, any length of ischae-mic bowel can cause significant systemic effects secondary to sepsis and obstruction proximal to the obstruction can result in significant dehydration. When bowel involvement is extensive circulatory failure is common.

Closed-loop obstructionThis occurs when the bowel is obstructed at both the proximal and distal points (Figure 70.2). The distention is principally confined to the closed loop, distention proximal to the obstruct-ed segment is not typically marked.

A classic form of closed-loop obstruction is seen in the pres-ence of a malignant stricture of the colon with a competent ileocaecal valve (present in up to one-third of individuals). This can occur with lesions as far distally as the rectum. The inability of the distended colon to decompress itself into the small bowel

results in an increase in luminal pressure, which is greatest at the caecum, with subsequent impairment of blood flow in the wall. Unrelieved, this results in necrosis and perforation (Figure 70.3).

SPECIAL TYPES OF MECHANICAL INTESTINAL OBSTRUCTION

Internal herniaInternal herniation occurs when a portion of the small intestine becomes entrapped in one of the retroperitoneal fossae or in a congenital mesenteric defect.

The following are potential sites of internal herniation (all are rare):

s� the foramen of Winslow;s� a defect in the mesentery;s� a defect in the transverse mesocolon;s� defects in the broad ligament;s� congenital or acquired diaphragmatic hernia;s� duodenal retroperitoneal fossae – left paraduodenal and right

duodenojejunal;

Figure 70.3 Carcinomatous stricture (X) of the hepatic flexure: closed-loop obstruction.

Figure 70.2 Distension. Closed-loop obstruction with no proximal (A) or distal (C) distension and impending strangulation (B).

B

A C

X

Jacob Benignus Winslow , 1669–1760, Professor of Anatomy, Physic and Surgery, Paris, France.

11-70-B&L_26th-Pt11_Ch70-cc.indd 1182 10/09/2012 11:54

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SPECIAL TYPES OF MECHANICAL INTESTINAL OBSTRUCTION

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Internal Hernia• Foramen of Winslow

• ︎ Defects in mesentery/transverse mesocolon

• ︎ Defects in the broad ligament

• ︎ Congenital or acquired diaphragmatic hernia

• ︎ Duodenal retroperitoneal fossae

• ︎ Caecal/appendiceal retroperitoneal fossae

• ︎ Intersigmoid fossa13

Enteric strictures

• Strictures secondary to tuberculosis or Crohn’s disease

• Malignant strictures from a lymphoma

• Subacute or chronic intestinal obstruction

• Resection and anastomosis is standard

• Strictureplasty in Crohn’s disease

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Bolus obstruction• Gallstones

• Food

• Trichobezoar

• Phytobezoar

• Stercoliths

• Worms15

Adhesions and bands

• Commonest cause of intestinal obstruction in Western countries

• Life time risk requiring admission is 4% subsequent to abdominal surgery

• Risk of requiring laparotomy is 2%

• Adhesions start to form with hours of abdominal surgery

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Causes of adhesions

Acute inflammation Sites of anastomoses, reperitonealisation of raw areas,

trauma, ischaemia Foreign material Talc, starch, gauze, silk

Infection Peritonitis, tuberculosis

Chronic inflammatory

conditions Crohn’s disease

Radiation enteritis

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Prevention of adhesions

• Factors that may limit adhesion formation include:

• Good surgical technique

• Washing of the peritoneal cavity with saline to remove clots

• Minimising contact with gauze

• Covering anastomosis and raw peritoneal surfaces

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Bands

• Usually only one band is culpable

• Congenital eg: obliterated vitellointestinal duct

• String band following bacterial peritonitis

• A portion of greater omentum adherent to the parietes

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Intussusception

• Most common in children

• Adult cases are secondary to intestinal pathology, e.g. polyp, Meckel’s diverticulum

• Ileocolic is the most common variety

• Can lead to an ischaemic segment

• Radiological reduction is indicated in most paediatric cases

• Adults require surgery

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Acute intussusception• One portion of the gut invaginate into an immediately adjacent segment

• Proximal into distal segments

• Most common in children

• Peak incidence 5-10 months of age

• 90% cases are idiopathic

• An associated upper respiratory tract infection or gastroenteritis may precede the condition

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Lead Points• Meckel’s diverticulum

• Polyp

• Duplication

• Henoch-Schonlein purpura

• After 2 years age a lead point is present in one third of children

• Adult cases invariably have a lead point- polyp or submucosal lipoma

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Components

• Composed of three parts

• Intussusceptum

• Middle tube

• Intussuscepiens

• Apex is the lead point

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Pathophysiology

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Volvulus

• Axial rotation of bowel about its mesentery

• >180° causes obstruction

• >360° causes vascular occlusion

• Primary and secondary types

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Volvulus• May involve the small intestine, caecum or

sigmoid colon; neonatal midgut volvulus secondary to midgut malrotation is life-threatening

• The most common spontaneous type in adults is sigmoid

• Sigmoid volvulus can be relieved by decompression per anum

• Surgery is required to prevent or relieve ischaemia

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Sigmoid volvulus

• Rotation in anticlockwise direction

• Fulminant presentation: Sudden onset, severe pain, early vomiting, rapid deterioration

• Indolent presentation: Insidious onset, slow progressive course, less pain and late vomiting

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Compound volvulus

• Ileosigmoid knotting

• Rare condition

• Gangrene of one or both loops28

CLINICAL FEATURES OF INTESTINAL OBSTRUCTION

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Dynamic Obstruction

Classical quartet

Absolute Constipation

Vomiting Distension

Pain

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Classification

• Small bowel or Large bowel

• Complete or Incomplete (partial or subacute)

• Simple or Strangulating/strangulated

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High Small Bowel Obstruction

• Profuse early vomiting

• Dehydration is rapid

• Minimal distension

• Little evidence fo dilated small bowel loops on x-rays

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Middle Small Bowel Obstruction

• Intermittent pain

• Moderate abdominal distension

• Vomiting is moderate

• Multiple dilated small bowel loops on x-rays

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Low Small Bowel Obstruction

• Pain is predominant

• Central abdominal distension

• Vomiting is delayed

• Multiple dilated small bowel loops on x-rays

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Large Bowel Obstruction

• Distension is pronounced

• Pain is less severe

• Vomiting and dehydration later features

• Colon proximal to obstruction distended on x-rays

• Small bowel dilatation if ileocecal valve is incompetent

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Varying Clinical Features

• Location of obstruction

• Duration of obstruction

• Underlying pathology

• Intestinal ischemia

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Late manifestations• Dehydration

• Oliguria

• Hypovolemic shock

• Pyrexia

• Septicemia

• Respiratory embarrassment

• Peritonism

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Pain in intestinal obstruction• First symptom

• Sudden in onset, severe and colicky in nature

• Centred on the umbilicus in small bowel

• Lower abdomen in large bowel

• Colicky pain replaced with mild diffuse pain

• Severe pain suggestive of strangulation

• Paralytic ileus is usually painless

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Vomiting

• Interval from onset of pain to vomiting varies with site of obstruction

• Alters from digested food to feculent material as obstruction progresses

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Distension

• Distension depends on the site of obstruction

• Visible peristalsis may be present

• Can be provoked by ‘flicking’ the abdomen

• Distension is a later feature of colonic obstruction

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Constipation

• Classified as

• Absolute

• Relative

• Absolute constipation in complete intestinal obstruction

• Early on in obstruction some patients may pass flatus or faeces

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Other manifestations

• Dehydration more common in small bowel obstruction

• Pyerxia indicates the onset of ischmia or perforation

• Hypothermia occurs in septicemic shock

• Localized tenderness indicates infarction or perforation

• Augmented bowel sounds

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Clinical features: strangulation

• Constant and severe pain

• Tenderness with rigidity and peritonism

• Shock

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Clinical Features: intussusception• Classically presents with episodes of screaming and drawing up of legs

in a previous well male infant

• Vomiting is bile stained

• Redcurrant jelly stool

• Abdomen is not distended

• 60% of cases have a palpable lump in the abdomen

• DRE may reveal blood stained mucus and apex may be paplable. 44

Clinical : volvulus• Cecal volvulus clockwise twist

• Ischemia is common

• 25% of cases have a palpable tympanitic swelling in the midline or left side

• Sigmoid volvulus presents with increasing abdominal distension

• Hiccough and retching

• Constipation is absolute

• Grossly distended sorted colon visible in some patients

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IMAGING

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The AXR

• 3-6-9 Rule • Small bowel <3 cm • Large bowel <6 cm • Appendix <6 mm • Cecum <9 cm

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Supine vs Erect

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The stepladder sign

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X-ray Abomen

JejunumColon50

Coffee-bean sign

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Frimann-Dahl Sign

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Ileosigmoid Knotting

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Cecal Volvulus

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TREATMENT OF ACUTE INTESTINAL OBSTRUCTION

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Three Main Measures

• Gastrointestinal drainage via a nasogastric tube

• Fluid and electrolyte replacement

• Relief of obstruction

• Surgical treatment for most cases

• Closed loop obstruction and strangulation require urgent surgery

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Supportive management

• Nasogastric decompression by Ryle tube

• Free drainage with 4 hourly aspiration

• Sodium and water loss are replace with Hartmann’s solution or Normal Saline

• Broad spectrum antibiotics are started

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Principles of surgery

• Management of:

• The segment at the site of obstruction

• The distended proximal bowel

• The underlying cause of obstruction

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Surgical Treatment

• Indications for early surgical intervention

• Obstructed external hernia

• Clinical features suspicious of intestinal strangulation

• Obstruction in a ‘virgin’ abdomen

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“the Sun should not both rise and set”

• Classical advice based on concern for development of ischemia

• Adequate resuscitation is necessary before surgery

• Conservative management up to 72 hours for adhesive obstruction

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Surgical Details• Midline incision

• Assessment is made of:

• The site of obstruction

• The nature of obstruction

• The viability of the gut

• The bowel is delivered into the wound

• Bowel decompression is performed61

Viable or non-viable?

Viable Non-viable

Circulation

Dark colour becomes lighter

Visible pulsation in mesenteric arteries

Dark colour remains

No detectable pulsation General

Appearance Shiny Dull and lustreless

Intestinal musculature

Firm

Peristalsis may be observed

Flabby, thin and friable

No peristalsis 62

Viable vs Non-viable

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Surgical details

• Type of surgery

• Adhesiolysis - enterolysis

• Excision of small bowel

• Bypass

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Decision making

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Decision making

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TREATMENT OF ACUTE LARGE BOWEL OBSTRUCTION

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Operative details

• Usually caused by carcinoma

• Occasionally by diverticular disease

• Pseudo-obstruction should be ruled out by contrast study or CT scan

• Midline incision

• Cecal distension confirms large bowel obstruction

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Right sided disease• Right hemicolectomy for removable lesion in:

• Cecum

• Ascending colon

• Hepatic flexure

• Proximal transverse colon

• Primary anastomosis safe if general condition of patient is reasonable

• Colostomy or ileostomy other options

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Left sided disease

• Splenic flexure lesions require an extended right hemicolectomy with ileo- descending colon anastomosis

• Cecostomy for gravely ill patients in imminent caecal rupture

• Left hemicolectomy with Hartmann’s procedure

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Treatment of sigmoid volvulus

• Flexible or rigid sigmoidoscopy with insertion of flatus tube

• Laparotomy with untwisting of volvulus

• Sigmoidopexy or resection depending on condition of bowel

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Resection

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CHRONIC LARGE BOWEL OBSTRUCTION

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Causes• Fecal impaction

• Crohn’s disease, ischemia, diverticulosis, anastomotic stenosis

• Metastatic deposits (ovarian), endometriosis

• Hirschsprung’s disease

• Idiopathic megacolon

• Pseudo-obstruction74

Investigation

• X-rays abdomen

• Single contrast enema

• CT scan

• Endoscopy

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Procedure

• Organic disease requires decompression

• Stomal stenosis managed easily

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Adynamic Obstruction

• Paralytic ileus

• Pseudo-obstruction

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Paralytic ileus

• Failure of peristaltic activity

• Accumulation of gas and fluid

• Abdominal distension, vomiting and absolute constipation

• Absent or tinkling bowel sounds

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Varieties

• Postoperative

• Infection

• Reflex ileus - spinal fractures, retroperitoneal haemorrhage

• Metabolic - Uremia and Hypokalemia

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Management of paralytic ileus

• Nasogastric suction

• Electrolyte balance

• Treatment of primary cause

• Prolonged ilues needs a CT scan to rule out abdominal sepsis

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Pseudo-obstruction

• Obstruction of the bowel in the absence of a mechanical cause or acute intra-abdominal disease

• Associated with an underlying neuropathy and/or myopathy

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Pseudo-obstruction• Metabolic

• Diabetes

• Hypokalaemia

• Uraemia

• Severe trauma (especially to the lumbar spine and pelvis)

• Shock

• Idiopathic

• Septicaemia

• Postoperative

• Retroperitoneal irritation

• Blood

• Urine

• Pancreatitis

• Drugs

• Secondary gastrointestinal involvement

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Colonic pseudo-obstruction• Acute or chronic

• Acute known as Ogilvie’s syndrome

• Absence of mechanical obstruction confirmed by colonoscopy or single contrast barium enema

• Treat identified cause

• IV Neostigmine 1 mg

• Colonoscopic decompression

• Cecal perforation likely if diameter > 14 cm

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