Intestinal obstruction

1
Intestinal obstruction

• Definition arrest of downward propulsion of
  intestinal content
• Classification
• according to
• A)pathological cause
• 1)simple intestinal
  obstruction
• 2) strangulated
  intestinal obstruction
• B)level of obstruction
• 1) high small
  intestinal obstruction
• 2) low small
  intestinal obstruction
• 3) large
  intestinal obstruction
• C)onset and course of obstruction
• 1) acute
• 2)chronic
  
• D) mechanical Vs Adynamic
• E) complete Vs incomplete

2
Causes of intestinal obstruction

• Dynamic
• Intraluminal
• Impaction
• Foreign bodies
• Bezoars
• Gallstones
• Intramural
• Stricture
• Malignancy
• Extramural
• Bands/adhesions
• Hernia( internal /external )
• Volvulus
• Intussusception

• Adynamic
• Paralytic ileus
• Mesenteric vascular occlusion
• Pseudo-obstruct

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Intestinal obstruction

• Small intestinal ileus is the most common form of
  intestinal obstruction it occurs after most
  abdominal operations and is a common response to
  acute intra abdominal inflammatory conditions
• Mechanical small bowel obstruction is somewhat
  less common such obstruction is secondary to
  intra-abdominal adhesions, hernias, or cancer
• Mechanical colonic obstruction most often
  develops in response to obstructing carcinoma,
  diverticulitis,or volvulus.
• Acute colonic pseudo-obstruction occurs most
  frequently in the postoperative period or in
  response to another acute medical illness.

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• When the bowel is occluded at a single point
  along the intestinal tract, simple obstruction is
  present.
• When a segment of bowel is occluded at two points
  along its course by a single constrictive lesion
  that occludes both the proximal and the distal
  end of the intestinal loop as well as traps the
  bowels mesentery, closed-loop obstruction is
  present.
• When the blood supply to a closed-loop segment of
  bowel becomes compromised, leading to ischemia
  and eventually to bowel wall necrosis and
  perforation, strangulation is present.
• The most common causes of simple obstruction are
  intra-abdominal adhesions, tumors, and
  strictures.
• The most common causes of closed-loop obstruction
  are hernias, adhesions, and volvulus.

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Etiology according to age

• Neonates congenital atresia , volvulus
  neonatorum, anorectal malformation ,mechonium
  ileus and Hirschsprungs disease
• infant ileocaecal intussusception ,
  Hirschsprungs disease and strangulated hernia
• Adult adhesion, strangulated hernia
• Elderly colon carcinoma, adhesion and
  strangulated hernia

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Pathology

• Simple
• distal to obstruction
• proximal
• peristalsis
• blind loop
• Strangulation
• General effect
• fluid and electrolyte loss
• septicaemia

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Pathophysiology

• Early in the course of an obstruction, intestinal
  motility and contractile activity increase in an
  effort to propel luminal contents past the
  obstructing point. Later in the course of
  obstruction, the intestine becomes fatigued and
  dilates, with contractions becoming less frequent
  and less intense.
• As the bowel dilates, water and electrolytes
  accumulate both intraluminally and in the bowel
  wall itself. This massive third-space fluid loss
  accounts for the dehydration and hypovolemia.
• The metabolic effects of fluid loss depend on the
  site and duration of the obstruction. With a
  proximal obstruction, dehydration may be
  accompanied by hypochloremia, hypokalemia, and
  metabolic alkalosis associated with increased
  vomiting. Distal obstruction of the small bowel
  may result in large quantities of intestinal
  fluid into the bowel however, abnormalities in
  serum electrolytes are usually less dramatic.
• Oliguria, azotemia, and hemoconcentration can
  accompany the dehydration. Hypotension and shock
  can ensue. Other consequences of bowel
  obstruction include increased intra-abdominal
  pressure, decreased venous return, and elevation
  of the diaphragm, compromising ventilation.
  These factors can serve to further potentiate the
  effects of hypovolemia.

8
Pathophysiology

• As the intraluminal pressure increases in the
  bowel, a decrease in mucosal blood flow can
  occur. These alterations are particularly noted
  in patients with a closed-loop obstruction in
  which greater intraluminal pressures are
  attained. A closed-loop obstruction, produced
  commonly by a twist of the bowel, can progress to
  arterial occlusion and ischemia if left untreated
  and may potentially lead to bowel perforation and
  peritonitis. Bacteria translocating to mesenteric
  lymph nodes and even systemic organs.However, the
  overall importance of this bacterial
  translocation on the clinical course has not been
  entirely defined.

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Clinical picture

• Cardinal symptom
• Pain, Distention , Vomiting,
  Absolute constipation
• The nature of the presentation will be influenced
  by the site
• In high small bowel obstruction, vomiting
  occurs early and is profuse with rapid
  dehydration. Distension is minimal with little
  evidence of fluid levels on abdominal radiography
• In low small bowel obstruction, pain is
  predominant with central distension. Vomiting is
  delayed. Multiple central fluid levels are seen
  on radiography
• In large bowel obstruction, distension is early
  and pronounced. Pain is mild and vomiting and
  dehydration are late. The proximal colon and
  caecum are distended on abdominal radiography
• The nature of the presentation will also be
  influenced by whether the obstruction is
  acute chronic acute on chronic subacute.
• Acute obstruction usually occurs in small bowel
  obstruction, with sudden onset of severe colicky
  central abdominal pain, distensionand early
  vomiting and constipation
• Chronic obstruction is usually seen in large
  bowel obstruction, with lower abdominal colic and
  absolute constipation followed by distension.
• In acute on chronic obstruction there is a short
  history of distension and vomiting against a
  background of pain and constipation.
• Subacute obstruction implies an incomplete
  obstruction.
• Presentation will be further influenced by
  whether the obstruction is
• simple in which the blood supply is intact
• strangulating/strangulated
• Examination
• General,
• Abdominal inspection, palpation
  ,percussion , auscultation

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History

• The typical crampy abdominal pain associated with
  intestinal obstruction occurs in paroxysms at 4-
  to 5-minute intervals and occurs less frequently
  with distal obstruction. It is usually centred on
  the umbilicus (small bowel) or lower abdomen
  (large bowel). With increasing distension, the
  colicky pain is replaced by a mild constant
  diffuse pain.
• The development of severe persistant pain is
  indicative of the presence of strangulation. Pain
  may not be a significant feature in postoperative
  simple mechanical obstruction and does not
  usually occur in paralytic ileus.
• Nausea and vomiting are more common with a higher
  obstruction and may be the only symptoms in
  patients with gastric outlet or high intestinal
  obstruction. An obstruction located distally is
  associated with less emesis, and the initial and
  most prominent symptom is the cramping abdominal
  pain. As obstruction progresses the character of
  the vomitus alters from digested food to
  faeculent material, as a result of the presence
  of enteric bacterial overgrowth.
• In the small bowel the degree of distension is
  dependent on the site of the obstruction and is
  greater the more distal the lesion. Visible
  peristalsis may be present. Distension is delayed
  in colonic obstruction and may be minimal or
  absent in the presence of mesenteric vascular
  occlusion.
• Constipation may be classified as absolute (i.e.
  neither faeces nor flatus is passed) or relative
  (where only flatus is passed). Absolute
  constipation is a cardinal feature of complete
  intestinal obstruction. Some patients may pass
  flatus or faeces after the onset of obstruction
  as a result of the evacuation of the distal bowel
  contents. The rule that constipation is present
  in intestinal obstruction does not apply in
  Richters hernia gallstone obturation
  mesenteric vascular occlusion obstruction
  associated with pelvic abscess partial
  obstruction (faecal impaction/colonic neoplasm)
  in which diarrhoea may often occur.

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Physical Examination

• The patient with intestinal obstruction may
  present with tachycardia and hypotension,
  demonstrating the severe dehydration that is
  present.
• Fever suggests the possibility of strangulation.
• Abdominal examination demonstrates a distended
  abdomen, with the amount of distention some what
  dependent on the level of obstruction. Previous
  surgical scars should be noted. Early in the
  course of bowel obstruction, peristaltic waves
  can be observed, particularly in thin patients,
  and auscultation of the abdomen may demonstrate
  hyperactive bowel sounds with audible rushes
  associated with vigorous peristalsis (i.e.,
  borborygmi). Late in the obstructive course,
  minimal or no bowel sounds are noted.
• Mild abdominal tenderness may be present with or
  without a palpable mass however, localized
  tenderness, rebound, and guarding suggest
  peritonitis and the likelihood of strangulation.
• A careful examination must be performed to rule
  out incarcerated hernias in the groin, the
  femoral triangle, and the obturator foramen.
• A rectal examination should be performed to
  assess for intraluminal masses and to examine the
  stool for occult blood, which may be an
  indication of malignancy, intussusception, or
  infarction.

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Strangulation

• Classic picture of strangulation include
  tachycardia, fever, leukocytosis, and a constant,
  noncramping abdominal pain. Tenderness with
  rigidity, Shock ,With the cardinal signs of
  intestinal obstruction
• In cases of intestinal obstruction in which
  pain persists despite conservative management,
  even in the absence of the above signs,
  strangulation should be diagnosed.
• When strangulation occurs in an external
  hernia, the lump is tense, tender and
  irreducible, there is no expansile cough impulse
  and it has recently increased in size.
• Pathology
• The venous return is compromised before the
  arterial supply. The resultant increase in
  capillary pressure leads to local mural
  distension with loss of intravascular fluid and
  red blood cells intramurally and extraluminally.
  Once the arterial supply is impaired,
  haemorrhagic infarction occurs. As the viability
  of the bowel is compromised there is marked
  translocation and systemic exposure to anaerobic
  organisms with their associated toxins. The
  morbidity of intraperitoneal strangulation is far
  greater than with an external hernia, which has a
  smaller absorptive surface.
• Causes of strangulation
• External Hernial orifices Adhesions/bands
• Interrupted blood flow Volvulus
  Intussusception
• Increased intraluminal pressure Closed-loop
  obstruction
• Primary Mesenteric infarction

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Closed-loop obstruction

• This occurs when the bowel is obstructed at both
  the proximal and
• distal points.
• It is present in many cases of intestinal
  strangulation. Unlike cases of non-strangulating
  obstruction, there is no early distension of the
  proximal intestine. When gangrene of the
  strangulated segment is imminent, retrograde
  thrombosis of the mesenteric veins results in
  distension on both sides of the strangulated
  segment.
• A classic form of closed-loop obstruction is seen
  in the presence of a malignant stricture of the
  right colon with a competent ileocaecal valve
  (present in up to one-third of individuals). 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 supply. Unrelieved, this results in
  necrosis and perforation

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Investigations

• Plain X ray of the abdomen Radiological features
  of obstruction
• The obstructed small bowel is characterised by
  straight segments that are generally central and
  lie transversely. No gas is seen in the colon
• The jejunum is characterised by its valvulae
  conniventes, which completely pass across the
  width of the bowel and are regularly spaced,
  giving a concertina or ladder effect
• Ileum the distal ileum has been described as
  featureless
• Caecum a distended caecum is shown by a
  rounded gas shadow in the right iliac fossa
• Large bowel, except for 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
• Blood urea and electrolyte
• Blood picture
• U.S.
• CT scan
• Endoscopy

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Treatment

• The treatment is urgent relief of obstruction
  after preparation
• Preoperative preparation ( fluid and
  electrolyte replacement ,antibiotics and Tube
  Decompression )
• Operation exploration
• Immediate operation indicated in peritonitis,
  incarcerated hernia, suspected or confirmed
  strangulation, sigmoid volvulus with systemic
  toxicity or peritoneal irritation, small bowel
  volvulus, colonic volvulus above sigmoid,
• Conservative (with exeption)
• indication 1)Adhesive
• 2)Ileocaecal
  itussusception
• 3)Sigmoid volvuls
• 4)feacal impaction
• Reassess patient every
  4 hr. Look for changes in pain, abdominal
  findings, and volume and character of NG
  aspirate. Repeat abdominal x-rays, and look for
  changes in gas distribution, pneumatosis
  cystoides intestinalis, and free intraperitoneal
  air.
• Classify patients condition as improved,
  unchanged, or worse.
• Decide whether operative treatment is
  necessary and, if so, whether it should be done
  on urgent or elective basis.
• Urgent operation Indications include
  Lack of response to 2448 hr of nonoperative
  therapy (increasing abdominal pain, distention,
  or tenderness NG aspirate changing from
  nonfeculent to feculent ? proximal small bowel
  distention with ? distal gas).

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TreatmentFluid Resuscitation and Antibiotics

• Patients with intestinal obstruction are usually
  dehydrated and depleted of sodium, chloride, and
  potassium, requiring aggressive intravenous
  replacement with an isotonic saline solution such
  as lactated Ringers.
• Urine output should be monitored by the placement
  of a Foley catheter.
• After the patient has formed adequate urine,
  potassium chloride should be added to the
  infusion if needed. Serial electrolyte
  measurements, as well as hematocrit and white
  blood cell count, are performed to assess the
  adequacy of fluid repletion.
• Because of large fluid requirements, patients,
  particularly the elderly, may require central
  venous assessment and, in some cases, the
  placement of a Swan-Ganz catheter.
• Broad-spectrum antibiotics are given
  prophylactically by some surgeons based on the
  reported findings of bacterial translocation
  occurring even in simple mechanical obstructions.
  In addition, antibiotics are administered as a
  prophylaxis for possible resection or inadvertent
  enterotomy at surgery.

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TreatmentTube Decompression and follow-up

• Nasogastric suction empties the stomach, reducing
  the hazard of pulmonary aspiration of vomitus and
  minimizing further intestinal distention from
  preoperatively swallowed air. Patients with
  adhesive simple intestinal obstruction may be
  treated conservatively with resuscitation and
  tube decompression alone. Resolution of symptoms
  and discharge without the need for surgery have
  been reported in 60 to 85 of patients with an
  adhesive simple intestinal obstruction .
• Although an initial trial of nonoperative
  management of most patients with partial small
  bowel obstruction is warranted, it should be
  emphasized that clinical deterioration of the
  patient or increasing small bowel distention on
  abdominal radiographs during tube decompression
  warrants prompt operative intervention.
• The decision to continue to treat a patient
  nonoperatively with a presumed bowel obstruction
  is based on clinical judgment and requires
  constant vigilance to ensure that the clinical
  course has not changed.

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Special forms

• Intussusceptions
• Volvulus
• Paralytic illeus
• mesenteric vascular occlusion
• Pseudo-intestinal obstruction

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Paralytic illeus

• Causes of Ileus
• Post laparotomy
• Metabolic and electrolyte derangements (e.g.,
  hypokalemia, hyponatremia, hypomagnesemia,
  uremia, diabetic coma)
• Drugs (e.g., opiates, psychotropic agents,
  anticholinergic agents)
• Intra-abdominal inflammation
• Retroperitoneal hemorrhage or inflammation
• Intestinal ischemia
• Systemic sepsis

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• Abdominal distention, usually without the colicky
  abdominal pain, is the typical and most notable
  finding. Nausea and vomiting may occur.
• Plain abdominal radiographs may reveal distended
  small bowel as well as large bowel loops.
• The treatment of an ileus is entirely supportive
  with nasogastric decompression and intravenous
  fluids.
• The most effective treatment to correct the
  underlying condition may be aggressive treatment
  of the sepsis, correction of any metabolic or
  electrolyte abnormalities, and discontinuation of
  medications that may produce an ileus.
  Pharmacologic agents have been used but for the
  most part have been ineffective. Drugs that block
  syinput (e.g., guanethidine) or stimulate
  parasympathetic activity (e.g., bethanechol or
  neostigmine) have been tried.
• In addition, hormonal manipulation, using
  cholecystokinin or motilin, has been evaluated,
  but the results have been inconsistent.

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pseudo-obstruction

• Factors associated with pseudo-obstruction
• Idiopathic
• Metabolic Diabetes, intermittent
  porphyria,Acute hypokalaemia, Uraemia,Myxodoema
• Severe trauma (especially to the lumbar spine
  and pelvis)
• Shock
• Burns
• Myocardial infarction
• Stroke
• Septicaemia
• Retroperitoneal irritation by
  Blood,Urine,nzymes (pancreatitis),Tumour
• Drugs,Tricyclic antidepressants,Phenothiazines,L
  axatives
• Secondary gastrointestinal involvement,
  Scleroderma ,Chagas disease

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MESENTERIC ISCHAEMIA

• Mesenteric vascular disease may be classified as
  acute intestinal ischaemia with or without
  occlusion venous, chronic arterial, central or
  peripheral. The superior mesenteric vessels are
  the visceral vessels most likely to be affected
  by embolisation or thrombosis, with the former
  being most common. Occlusion at the origin of the
  superior mesenteric artery (SMA) is almost
  invariably the result of thrombosis, whereas
  emboli lodge at the origin of the middle colic
  artery. Inferior mesenteric involvement is
  usually clinically silent because of a better
  collateral circulation.
• Possible sources for the embolisation of the SMA
  include a left atrium associated with
  fibrillation, a mural myocardial infarction, an
  atheromatous plaque from an aortic aneurysm and a
  mitral valve vegetation associated with
  endocarditis.
• Primary thrombosis is associated with
  atherosclerosis and thromboangitis obliterans.
• Primary thrombosis of the superior mesenteric
  veins may occur in association with factor V
  Leiden, portal hypertension, portal pyaemia and
  sickle cell disease and in women taking the
  contraceptive pill.
• Irrespective of whether the occlusion is arterial
  or venous, haemorrhagic infarction occurs. The
  intestine and its mesentery become swollen and
  oedematous. Blood-stained fluid exudes into the
  peritoneal cavity and bowel lumen. If the main
  trunk of the SMA is involved, the infarction
  covers an area from just distal to the
  duodenojejunal flexure to the splenic flexure.
  Usually, a branch of the main trunk is implicated
  and the area of infarction is less.

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Clinical features

• The most important clue to an early diagnosis of
  acute mesenteric ischaemia is the sudden onset of
  severe abdominal pain in a patient with atrial
  fibrillation or atherosclerosis. The pain is
  typically central and out of all proportion to
  physical findings.Persistent vomiting and
  defaecation occur early, with the subsequent
  passage of altered blood. Hypovolaemic shock
  rapidly ensues. Abdominal tenderness may be mild
  initially with rigidity being a late feature.
• Investigation will usually reveal a profound
  neutrophil leucocytosis with an absence of gas in
  the thickened small intestine on abdominal
  radiographs. The presence of gas bubbles in the
  mesenteric veins is rare but pathognomonic.

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Treatment

• Treatment needs to be tailored to the individual.
  
• In conjunction with full resuscitation,
  embolectomy via the ileocolic artery or
  revascularisation of the SMA may be considered in
  early embolic cases.
• The majority of cases, however, are diagnosed
  late.
• All affected bowel should be resected.
• Anti-coagulation should be implemented early in
  the postoperative period.
• After extensive enterectomy it is usual for
  patients to require
• intravenous alimentation.
• The young, however, may sometimes develop
  sufficient intestinal digestive and absorptive
  function to lead relatively normal lives.
• In selected cases consideration may be given to
  small bowel transplantation.

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Ischaemic colitis

• Infarction of the large intestine alone is
  relatively rare.
• Involvement of the middle colic artery territory
  should be treated by transverse colectomy and
  exteriorisation of both ends, with an extended
  right hemicolectomy in selected cases.
• Ischaemic colitis describes the structural
  changes that occur in the colon as a result of
  the deprivation of blood. They are most common in
  the splenic flexure, whose blood supply is
  particularly tenuous.
• They have been classified by Marston into
  gangrenous, transient and stricturing forms only
  stricturing forms cause obstruction and only a
  few such patients require resection.