Definition The term intestinal obstruction refers to any form of impedance to the normal passage of bowel contents through the small or large intestine. It is a common cause of acute abdominal pain.

Causes of intestinal obstruction I. Dynamic: (mechanical obstruction) A) Intraluminal: 1.Impaction. 2.Forign body. 3.Bezoar (tricho-bezoar & phyto-bezoar) 4.Gall stone. 5.Stercolith. B) Intramural: 1.Stricture (crohn's disease, T.B). 2.Malignancy. 3.Congenital atresia. C) Extramural: 1.Bands & Adhesion. 2.Hernia. 3.Volvulus. 4.Intussusception. 5.Tumor.

Causes of intestinal obstruction II. A dynamic: (functional obstruction) A) Paralytic ileus. (small bowel). B) Mesenteric vascular occlusion. C) Pseudo-obstruction. (large bowel).

Classification of intestinal obstruction 1. Small bowel obstruction & Large bowel obstruction. 2. Mechanical obstruction & Functional obstruction. 3. Simple obstruction & Strangulated obstruction. 4. Partial obstruction & Complete obstruction. 5. -Acute obstruction, Sub acute obstruction, Acute on chronic obstruction & Chronic obstruction.

Symptoms: Abdominal pain. Vomiting Constipation. Distention.

Most people who have small-bowel obstruction experience crampy abdominal pain that comes in waves. The pain is around the navel (umbilicus).

Small-bowel obstructions usually cause vomiting. The vomitus will usually be green if the obstruction is in the upper small intestine and brown if it is in the lower small intestine

Constipation and inability to pass gas are signs of bowel obstruction. However, when the bowel is partially blocked, a person may have diarrhea and pass gas. Someone with a complete obstruction may have a bowel movement if there is stool below the obstruction.

With blockages of the lower small intestine, the epigastric area may be distended, or bloated.

Aetiology  5% of acute surgical admissions are due to small bowel obstruction  In UK the commonest causes are :  (60% adhesion)  (20% strangulated hernia)  (5% malignancy)  (5% volvulus )

The bowel proximal to the obstruction dilates and that distal to the obstruction exhibits normal peristalsis and absorption until it becomes empty and collapses. Initially, proximal peristalsis is increased in an attempt to overcome the obstruction. If the obstruction is not relieved, the bowel continues to dilate, ultimately there is a reduction in peristaltic strength, resulting in flaccidity and paralysis. When strangulation occurs, the blood supply is compromised and the bowel becomes ischaemic.

 Direct pressure on the bowel wall  Hernia orifices  Adhesions/bands  Interrupted mesenteric blood flow  Volvulus  Intussusception  Increased intraluminal pressure  Closed-loop obstruction

 Colicky central abdominal pain  Vomiting - early in high obstruction  Abdominal distension - extent depends on level of obstruction  Absolute constipation - late feature of small bowel obstruction  Dehydration associated with tachycardia, hypotension and oliguria  Hypokalemia and pyrexia may be present  Features of peritonism indicating strangulation or perforation

Supine abdominal X-ray shows dilated small bowel Valvulae coniventes differentiate proximal small bowel, with complete circles, while a distal small bowel obstruction is featureless. Large bowel obstruction shows dilated peripheral loops with incomplete circles. Erect abdominal film rarely provided additional information, it may subsequently be requested when further doubt exists.

 Adequate resuscitation prior to surgery is essential  May require more than 5 litres of intravenous crystalloid  Adequacy of resuscitation should be judged by urine output and central venous pressure (CVP)  Surgery in under resuscitated patient is associated with increased mortality  If the obstruction is presumed to be due to adhesions and there are no features of peritonism then conservative management for up to 48 hours is often safe, but requires regular clinical review  If features of peritonism or systemic toxicity is present, then there is a need to consider early operative intervention  The exact procedure will depend upon the underlying cause

Absolute  Generalised peritonitis  Localised peritonitis  Visceral perforation  Irreducible hernia

Relative  Palpable mass lesion  'Virgin' abdomen  Failure to improve Indications for surgery

 Incomplete obstruction  Previous surgery  Advanced malignancy  Diagnostic doubt - possible ileus

 Functional obstruction most commonly seen after abdominal surgery  Also associated with trauma, intestinal ischaemia, sepsis  Small bowel is distended throughout its length  Absorption of fluid, electrolytes and nutrients is impaired  Significant amounts of fluid may be lost from the extracellular compartment

 Recent operation or trauma history  Abdominal distension is often apparent  Pain is often not a prominent feature  If no nasogastric tube in-situ vomiting may occur  Large volume aspirates my occur via nasogastric tube  Flatus will not be passed until resolution of the ileus  Auscultation will reveal absence of bowel sounds

 Plain abdominal x-ray may show dilated loops of small bowel  Gas may be present in the colon  If doubt as to whether there is a mechanical or functional obstruction then water soluble contrast study may be helpful

 Prevention is better than cure  Bowel should be handled as little as possible  Fluid and electrolyte derangements should be corrected  Sources of sepsis should be eradicated  For an established ileus the following will be required  Nasogastric tube  Fluid and electrolyte replacement  Alvimopan is the only licensed drug in prolonged ileus  Usually resolves spontaneously after 4 or 5 days

 15% colorectal cancers present with obstruction  Most patients are over 70 years old  Risk of obstruction greatest with left sided lesions  Usually present at a more advanced stage  25% have distant metastases at presentation  Perforation can occur at site of tumour or in a dilated caecum

 15% colorectal cancers present with obstruction  Most patients are over 70 years old  Risk of obstruction greatest with left sided lesions  Usually present at a more advanced stage  25% have distant metastases at presentation  Perforation can occur at site of tumour or in a dilated caecum in closed loop obstruction

Caecal tumours present with small bowel obstruction  Colicky central abdominal pain  Early vomiting  Late absolute constipation  Variable extent of distension

 Left sided tumours present with large bowel obstruction  Change in bowel habit  Absolute constipation  Abdominal distension  Late vomiting

 Plain supine abdominal x-ray will show dilated large bowel  Small bowel may also be dilated depending on competence of ileocaecal valve

All patients require  Adequate resuscitation  Prophylactic antibiotics  Consenting and marking for potential stoma formation

 At operation  Full laparotomy should be performed  Liver should be palpated for metastases  Colon should be inspected for synchronous tumours

Appropriate operations include  Right sided lesions – right hemicolectomy  Transverse colonic lesion – extended right hemicolectomy  Left sided lesions – various options

 Three-staged procedure  Defunctioning colostomy  Resection and anastomosis  Closure of colostomy  Three stage procedure will involve 3 operations!  Associated with prolonged total hospital stay  Transverse loop colostomy can be difficult to manage

Two-staged procedure  Hartmann’s procedure  Closure of colostomy  With two-staged procedure only 60% of stomas are ever reversed

 One-stage procedure  Resection, on-table lavage and primary anastomosis  With one-stage procedure stoma is avoided  Anastomotic leak rate of less than 4% have been reported

 Irrespective of option total perioperative mortality is about 10 %

 Volvulus: Twisting of loop of intestine around its mesenteric attachment site may occur at various sites in the GI tract  Most commonly: sigmoid & cecum  Rarely: stomach, small intestine, transverse colon  Results in partial or complete obstruction  May also compromise bowel circulation resulting in ischemia

 Sigmoid volvulus most common form of GI tract volvulus  Accounts for up to 8% of all intestinal obstructions  Most common in elderly persons (often neurologically impaired)  Patients almost always have a history of chronic constipation

 Redundant sigmoid colon that has a narrow mesenteric attachment to posterior abdominal wall allows close approximation of 2 limbs of sigmoid colon à twisting of sigmoid colon around mesenteric axis  Other predisposing factors  Chronic constipation  High-roughage diet (may cause a long, redundant sigmoid colon)  Roundworm infestation  Megacolon (often due to Chagas disease)  Peak age > 50 yrs.

 Torsion usually counterclockwise ranging from 180 – 540 degrees  Luminal obstruction generally at 180 degrees  Venous occlusion generally at 360 degrees à gangrene & perforation

May present as abdominal emergency  Acute distension  Colicky pain (often LLQ)  Failure to pass flatus or stool (constipation is a prevailing feature)  Vomiting is a late sign

 Tympanitic abdomen  Abdominal distention  +/- palpable mass

 Abdominal plain films usually diagnostic  Inverted U-shaped appearance of distended sigmoid loop  Largest and most dilated loops of bowel are seen with volvulus  Loss of haustra  Coffee-bean sign at midline crease corresponding to mesenteric root in a greatly distended sigmoid  Sigmoid volvulus – bowel loop points to RUQ  Cecal volvulus – bowel loop points to LUQ  Dilated cecum comes to rest in left upper quadrant  Bird’s-beak or bird-of-prey sign is seen on barium enema as it encounters the volvulated loop  CT scan is useful in assessing mural wall ischemia

 Large bowel obstruction due to other causes such as sigmoid colon cancer  Giant sigmoid diverticulum  Pseudo-obstruction (Ogilvie’s disease) Complications Colonic ischaemia Perforation Sepsis

 Derotation & decompression by rectal tube, colonoscope, or sigmoidoscope (flexible or rigid) when no signs of bowel ischemia or perforation  Laparoscopic derotation or laparotomy +/- bowel resection  Cecopexy à suture fixation of bowel to parietal peritoneum may prevent recurrence in cecal volvulus  Recurrence rate after decompression alone is 50%  However, resection is preferable if it can be achieved safely.

This may occur in an acute or a chronic form. The former, also known as Ogilvie’s syndrome, presents as acute large bowel obstruction. Abdominal radiographs show evidence of colonic obstruction, with marked caecal distension being a common feature. Indeed, caecal perforation is a well-recognised complication. The absence of a mechanical cause requires urgent confirmation by colonoscopy or a single-contrast water-soluble barium enema or CT.

When the cecal diameter exceeds 12 cm or the patient has a significant amount of abdominal discomfort, decompression is indicated as either: 1.IV Neostigmine in the patient without contraindications Colonoscopic decompression is indicated in those patients with contraindications to neostigmine administration or those who have failed neostigmine therapy. Another role for colonoscopy is to exclude a source of mechanical obstruction, in which case it may be both diagnostic and therapeutic.

The condition may recur in 25% of cases, necessitating further colonoscopy with simultaneous placement of a flatus tube. When colonoscopy fails or is unavailable, a tube caecostomy may be required. Continued symptoms may benefit from surgical intervention with subtotal colectomy and ileorectal anastomosis.

Mesenteric vascular disease may be classified as acute intestinal ischaemia – with or without occlusion – venous, chronic arterial, central or peripheral.

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.

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.

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. In the young, all affected bowel should be resected, whereas in the elderly or infirm the situation may be deemed incurable. Anti-coagulation should be implemented early in the postoperative period

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