Intestinal obstruction 3

Intestinal obstruction

Volvulus
It's a twisting or axial rotation of a portion of bowel about its mesentery.
Volvulus may be primary or secondary.
The primary occurs secondary to congenital malrotation of the gut, the abnormal mesenteric attachment or congenital bands.
Secondary which is more common is due to actual rotation of a piece of bowel around an acquired adhesion or stoma.
Volvulus neonotarum is due to a narrow mesentry of small bowel& caecum.the symptoms are repeated vomiting, catastrophic onset, distension& dehydration. Treatment is surgical.

Volvulus of the small intestine

This may be primary or secondary, usually occurs in the lower ileum. Treatment by surgical reduction& treating the underlying cause.

Caecal volvulus

This may occur as part of volvulus neo natorum & is usually a clockwise twist it's more common in females and usually presents acutely with the classic features of obstruction. In 25% cases examination may reveal a palpable tympanic swelling in the midline or left side of abdomen.
Plain radiography may reveal a gas-filled ileum & a distended caecum. Barium enema may be used to confirm the diagnosis with an absence of barium in the caecum & a bird beak deformity.
Treatment by surgical reduction& fixation of the caecum to the RIF (caecopexy), if the caecum is ischemic or gangrenous right hemicolectomy should be performed.

Sigmoid volvulus
Caused by:
- band of adhesion (peridiverticulitis)
Over loaded pelvic colon-
Long pelvic mesocolon-
-Narrow attachment of pelvic colon
Rotation nearly always occurs in an anticlockwise direction
The predisposing factors include; high residue diet& chronic constipation.
Clinical features
The symptoms are of large bowel obstruction. Young patients develop acute form progressive abdominal distension which may be associated with hiccough. Vomiting occurs late, with absolute constipation.
In the elderly chronic form may be seen (lower abdominal pain, absolute constipatipon & abdominal distension is a late symptom)
Plain radiograph shows massive colonic distension, a dilated loop of bowel running diagonally across the abdomen from right to left with 2 fluid levels seen, one within each loop of bowel.


Treatment
includes sigmoidoscopy to insert flatus tube to allow deflation of the gut therby allowing resuscitation &elective procedure. If failure, early laparotomy is mandatory to untwist the bowel, resection is preferable, or fixation of the sigmoid colon to the posterior abdominal wall in inexperienced hands.

Acute intestinal obstruction of the newborn

Congenital atresia
The incidence varies with anatomical site. duodenum(35%),jejunum(15%),ileum(25%),ascending(10%),multiple sites(15%)
Except in case of duodenal atresia, there are frequent associated abnormality of the heart& great vessels.

Atresia /stenosis of the duodenum

Atresia& stenosis are of equal frequency. In most cases except for the oesophagus, duodenum&rectum, the atresia is an insult of intrauterine vascular accident occurring late in pregnancy at the umbilical ring, so the ischaemic portion absorbed& disappear.
Because of complete obstruction, persistent vomiting occurs from birth; bile may or may not be present depending on the site of the septum. Distension is often absent, visible peristalsis may be seen in the left upper quadrant.
Atresia of the duodenum occurs at the level of the ampulla of vater.30% of babies have associated downs syndrome.
Radiology shows classic so called (double stomach) with 2 air-fluid levels.
In case of partial obstruction the lesion may be confirmed by instillation of gastrograffin through NGT, the medium must be aspirated once the lesion is confirmed.
Suprapapillry duodenal atresia my be distinguished from oesophageal atresia by absence of dribbling saliva & from infantile ploric stenosis by the absence of the lump. Duodenal obstruction in infancy may also be due to midgut volvulus, a band obstruction or annular pancreas.
Treatment; surgery is required as soon as resuscitation is completed; duodeno-jejunostomy is the operation of choice.

Atresia/stenosis of the jejunum/ileum

The vital importance of a diagnosis lies in the fact that proximal distension of the bowel may be so great that the vascular integrity is compromised, leading to gangrene& perforation.
In ileal atresia, the child born with abdominal distension or it occurs within 2 hrs after birth. In jejunal atresia early distension is absent but vomiting occurs early. In both condition, the vomit contains bile &some meconium is likely to be evacuated.
Radiology; air-fluid level are seen.
Surgery; either by exteriorisation of both limbs with subsequent closure or immediate end to end anastomosis.


Arrested rotation
The most common anomaly is when the caecum remains in the left hypochondrium& peritoneal band is found running from the caecum to the right side of the abdomen& then across the 2nd part of the duodenum (the trasduodenal band of Ladd).
The symptoms are repeated vomiting.
Treatment by early laparotomy to divide the band.

Chronic intestinal obstruction:

This may be organic or functional
Organic; 1- intramural; fecal impaction
2-mural; colorectal cancer, diverticulitis, strictures (crohns & ischaemia), anastomotic stenosis
3-extramural; adhesion, metastatic deposits, endometriosis
Functional; Hirschsprung disease, idiopathic megacolon, pseudo-obstruction

Clinical features

Constipation appears first, initially relative, then absolute, associated with distension.
Vomiting is late usually.
Rectal exam may reveal fecal impaction or tumour.
Diagnosis, by plain radiograph confirmed by water soluble enema to rules out functional cause.
Treatment: functional disease requires colonoscopic decompression & conservative management.
Organic disease needs laparotomy to deal with the underlying cause.

Adynamic obstruction

Paralytic ileus
It is failure of transmission of peristaltic waves secondary to neuromuscular failure result in stasis& accumulation of fluid& gas within the bowel with associated distension, vomiting, absence of bowel sounds& absolute constipation.
Types:
Postoperative; a degree of ileus usually occurred after any abdominal operation& its
self-limiting within 24-72hrs, it may be prolonged when there is hypoprotienemia or metabolic abnormality.
Infection; intraiabdominl sepsis may cause localized or generalized ileus
Reflex ileus; may occur following fractures of the spine or ribs, intraperitoneal hemorrhage.
Metabolic; uraemia& hypokaemia are the most common.
Clinical features
Paralytic ileus takes a clinical significance if 72hrs after laparotomy;
-there has been no bowel sounds on auscultation
-there has been no passage of flatus.
Abdominal distension becomes more marked& tympanitic. Pain is not a feature. Effortless vomiting may occur.


Radiology; gas-filled loops with multiple fluid levels

Management

With the use of NG suction& restriction of oral intake until bowel sound& passage of flatus return, electrolyte balance should be maintained.
Specific treatment is directed to the cause, the following principles apply;
-primary cause must be removed
Gastro intestinal distension must be relieved by decompression-
-Close observation for fluid& electrolyte balance
If paralytic ileus is prolonged &threatens life, a laprotomy should be considered to exclude hidden cause &facilitate bowel decompression.

Pseudo-obstruction

It is an obstruction, usually colonic in the absence of a mechanical cause or acute intra-abdominal disease, a variety of causes has been described.
-metabolic; DM, hypokalemia, uraemia, myxoedema
-severe trauma; especially to lumber spine &pelvis
-shock; burns, MI, stroke
-septicaemia
-retroperitonial irritation; blood, urine, enzymes (pancreatitis), tumour
-drugs; tricyclic antidepressants phenothiazines, levodopa, laxatives
-secondary GI involvement; scleroderma, chagas disease

Small intestinal pseudo-obstruction

May be primary or secondary. There is a recurrent subacute obstruction
Diagnosis is by exclusion of the mechanical cause.
Treatment: correction of any underlining cause. Metoclopromide& erythromycin may be used.


Colonic pseudo-obstruction
Acute or chronic form. Radiology shows evidence of colonic obstruction with marked caecal distension. Caecal perforation may occur. Exclusion of mechanical cause is urgent &done by colonoscopy or single water-soluble barium enema. Once confirmed, pseudo-obstruction should be treated by colonoscopic decompression. Recurrence in 25% of cases which requires further colonoscopy with placement of flatus tube. Continued symptoms may need surgical intervention with subtotal colectomy with ileorectal anastomosis.

Acute mesenteric ischaemia

Superior mesenteric vessels are most commonly affected, usually by embolisation (commoner) or thrombosis.
Possible cause of embolisation of SMA includes atrial fibrillation. MI, aortic aneurysm or endocarditis. Primary thrombosis is associated with atherosclerosis or thrombangitis obliterans. Primary thrombosis of SM vein may occur in portal HT, portal pyemia, sickle cell disease or contraceptive pills
Irrespective of arterial or venous, hemorrhagic infarction occurs, blood stained fluid exudes into the peritoneal cavity &bowel lumen. If the main trunk of SMA is involved, the infarct will involve area from duodenojejunal flexure to the splenic flexure.

Clinical features

The important clue to the diagnosis is the sudden onset of sever abdominal pain in patient with AF or atherosclerosis. The pain is central& out of all proportion to physical findings. Persistent vomiting& defecation occur with subsequent passage of altered blood, hypovolemic shock rapidly ensue. Mild abdominal tenderness initially. Rigidity is late feature.
Investigation show neutrophil leucocytosis.the presence of gas bubbles in mesenteric vein is rare but pathognomonic.

Treatment; in early cases embolectomy or revascularization. However the majority of cases are diagnosed late, all affected bowel should be resected. Anticoagulant should be started early in postoperative period.
Ischaemic colitis affect colon as a result of deprivation of blood supply. Commonly in splenic flexure. It is classified as gangrenous, stricturing &transient form.
Acute presentation with lower abdominal pain& passage of blood per rectum. DDX usually from carcinomna, crohns or ulcerative colitis.
In those patients without evidence of peritonism, most cases resolve spontaneously.
In a few a permanent stricture develops requiring elective resection.










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