Wee 4/5 - H - Bowel obstruction - adhesion/hernia,/volvulus/tumour/stricture/bolus/intussusception/strangulation/adynamic Flashcards
Let’s talk about the presentation, diagnosis and management of bowel obstruction Any part of the GI tract may become obstructed and present as an acute abdomen. What happens to the bowel proximal to the obstruction?
There is dilatation of the bowel proximal to the level of obstruction with air and fluid
We have talked about small bowel obstruction in a previous set of cards so this shall mainly focus on large bowel obstruction Initially however, lets summarise some some bowel obstruction facts * What are the main causes of small bowel obstruction? * What are other less common causes?
Small bowel obstruction - the two main causes occur outside of the bowel Main causes is intra-abdominal adhesions followed by hernias * Other causes are rarer andoccur either within the lumen or within the gut wall * Within the lumen - food / bezoar, gallastone ileus * Within the gut wall - tumours, crohn’s, radiation
What is the typical presentation of small bowel obstruction? What may be seen on examination?
ACUTE PRESENTATION * Distention * Vomiting * Borbogymi -rumbling of the stomach (typical sound heard when hungry) * Pain * Faeculent vomiting On examination, may see abdominal scars indicating previous surgery and increases risk of adhesions Also look for both femoral and inguinal hernias
How is small bowel diagnosis confirmed?
Usually will involved an Abdominal XRay CT scan of abdomen - gastrografin studies (a radiographic dye) may help confirming the site of the obstruction
How is AXR able to differentiate between small and large bowel obstruction?
Small bowel obstruction - will show central gs shadows with valvulae conniventes (plicae circularis) that completely cross the lumen Large bowel obstruction - will show peripheral gas shadows, proximal to the blockage (ie in caecum bt not in rectum)
Adhesional small bowel obstruction resulting from previous surgery is treated conservatively in the first instance, with a success rate of around 80% What is the management of small bowel obstruction caused by adhesions?
MANAGEMENT Usually conservative - DRIP AND SUCK method Start IV fluids and correct any electrolyte disturbances (‘drip’) Make the patient nil-by-mouth (NBM) and insert a nasogastric tube to decompress the bowel (‘sucks out air and fluid to relive abdominal swelling’) Urinary catheter and fluid balance Analgesia as required with suitable anti-emetics
Why do you not want to carry out surgery for adhesional small bowel obstruction? How long can drip and suck usually be continued up until? Does the drip and suck method treat hernias?
As far as prevention of adhesional small bowel obstruction is concerned, best approach is to avoid operation as any surgical procedure predisposes to adhesions Drip and suck method only treats adhesional small bowel obstruction -up to 72 hour is standard Hernias cannot be treated with drip and suck and usually require reduction - manually - to prevent stangulation and necrosis and if problematic surgical reduction
When should you surgically intervene in a patient with small bowel obstruction?
Intervene with emergency surgery if there is a strangulation of the bowel as this can cause ischemia and necrosis Also intervene if there is small bowel perforation
What is the surgical management of an obstructed small bowel - carried out if suspecting strnagulation or perforation? What type of incision? Which drugs are given?
Surgical management of small bowel obstruction is usually via a laparotomy using a midline incison Antibiotics and antithromboembolic measures are also taken
LARGE BOWEL OBSTRUCTION How does the rate at which vomiting occurs in GI tract obstruction relate to where the obstruction is? Will vomiting still occur even if the patient has / is not eating anything?
The more proximal the obstruction, the earlier vomiting develops. Can occur even if nothing is taken by mouth: GI secretions continue to be produced – Saliva, gastric , pancreatic, bile, small intestine (up to several litres per day).
The nature of the vomiting gives clues to the level of the small bowel obstruction What kind of vomiting is seen if it is * A gastric outlet obstruction? * Upper small bowel obstruction? * More distal small bowel / large bowel obstruction?
Gastric outlet obstruction - semi-digested food eaten a day or two previously however no bile Upper small bowel obstruction - copious bile stained fluid (green or yellow) Distal small bowel / large bowel obstruction - thicker, brown, foul smelling vomitus (Faeculent)
What are the different presenting features of small bowel vs large bowel obstruction? Why do intermittent episodes of colicky pain occur?
Small bowel obstruction usually presents with early vomiting, distension is less and pain is higher in the abdomen eg umbilical Large bowel obstruction presents with later vomiting, more constant pain and greater distension, more pronounced constipation Intermittent episodes of colicky pain occur as peristalsis attempts to overcome the obstruction.
Constipation How is constipation defined by the Rome IV criteria?
Constipation is a common primary functional disorder of the bowel but may, of course, develop secondary to another condition. * ROME IV criteria - defecation that is unsatisfactory because of infrequent stools ( Often passes with difficulty (with straining or discomfort), or seemingly incomplete defecation.
What is absolute constipation? What is it pathognomonic of?
Absolute constipation is pathognomonic of bowel obstruction - neither faeces of flatus is passed rectally
Consitpation alone often does not advocate further investigation but when occurring with different symptoms, doctors will wan to rule out major pathology What could constipation + rectal bleeding make you suspicious of? What could constipation + distension + active bowel sounds make you suspicious of?
Constipation + rectal bleeding - think possible malignancy Constipation + distension + active bowel sounds - maybe a GI stricture eg Crohn’s or GI obstruction
Back to large bowel If the ileo-caecal valve remains competent (50% cases) backward flow of accumulated bowel contents is prevented . What will happen in this case? Why may it be an emergency?
When the ileo-caecal valve remains competent in large bowel obstruction - this will cause the thin walled caecum to become progressively distended with swallowed air and fluids secretions from the GI tract This can potentially lead to rupture - it is known as a closed loop obstruction
If the bowel is only partially obstructed, the clinical features may be less clearly defined. Vomiting may be intermittent and bowel habit erratic. What can chronic incomplete obstruction lead to? What is responsible for the colicky pain in this type of obstruction?
Chronic incomplete obstruction can lead to gradual hypertrophy of the muscle of the bowel wall proximally Peristaltic activity in this hypertrophic muscle is responsible for bouts of colicky pain which can be more prominent that in complete obstruction
We know that both small and large bowel obstruction can present with pain in the abdomen (more common in large) If the pain is sharp, localised pain and associated with peritonism ( acute abdominal pain, abdominal tenderness, abdominal guarding), what is indicated?
When there is sharp, localised pain and peritonsim this may indicate strangulation of the bowel - urgent surgery required to prevent ischaemia and necrosis
What is the most useful sign in the investigation of a suspected bowel obstruction? What is seen?
Most useful investigation is a supine AXR. Bowel proximal to the obstruction is distended with gas Small bowel - distended small bowel loops lie central and have vulvulae coniventes (completely across lumen) Large bowel - distended bowel is perpheral and has hasutraations (not completely across)
What is often subsequently performed to confirm the diagnosis and look for a cause? What is the cut off/transition point that is seen on this scan on bowel obstruction?
CT scan is often subsequently performed to confirm the diagnosis and look for a cause. Transition point on CT scan with distended bowel proximal and collapsed bowel distal to the site of obstruction.
What are the principles of the initial management of a bowel obstruction? (small or large)
Nil by mouth DRIP AND SUCK * Insert IV cannula and prescribe fluids to rehydrate and correct electrolyte imbalance * Pass a nasogastric tube to decompress the stomach - removing excess air For hernia, will need to manually move the bowel SURGERY IF neither of these work
There are many different causes of bowel obstruction - we are going to discuss the mechanical causes What are the two most common causes of small bowel obstruction?
Intra-abdominal adhesions (congenital or resulting from previous abdominal surgery or peritonitis. ) or Hernia (incarcerated hernia)
What are the common causes of large bowel obstruction? What are the rare causes of both small and large bowel obstruction?
Common causes of large bowel obstruction * Colon carcinoma * Constipation * Diverticular stricture * Volvulus - sigmoid or caecal Rare causes of both - * inflammatory strictures (crohn’s), * Bolus obstuction - food bolus, impacted faeces (EVEN RARER - gallstone ileus and bezoar) * Intussuception
What is volvulus? Where are the two common places it can occur?
Volvulus occurs when a mobile loop of bowel rotates causing obstruction at its neck Can happen in the small or large bowel Commonly either caecal or sigmoid volvulus
