Small bowel obstruction

Case-based teaching module

Case 1 Dear surgeon on-call,

Please see this 72 year old lady whom I visited at home today. She complains of abdominal pain and vomiting. BNO

o/e dryAbdo distended ++

Many thanks, GP

Objectives

• Describe and classify the common causes of small bowel obstruction

• Understand initial resuscitation• Appreciate the role of different investigations• Understand the principles of operative and

non-operative management

Small bowel obstruction - history

What key features will you seek in the history?• Site of pain• Nature of pain• Duration of pain• Duration of vomiting – bilious vs “faeculent”• When bowels last open, passing flatus• Recent history suggestive of malignancy• PMH – abdominal surgery - intra-abdominal pathology eg. Crohns

Why does small bowel obstruction tend to cause central colicky pain?

• Small bowel is of midgut embryological origin

• What are the anatomical borders of the foregut, midgut and hindgut derivatives?

Foregut

• (Pharynx)• Oesophagus• Stomach• Duodenum (D1 & ½ D2)• Liver, Pancreas, Biliary tree

• Blood supply?

Coeliac trunk

Midgut• Duodenum from ½ D2 onward• Jejunum• Ileum• Caecum• Ascending colon• Prox ⅔ Transverse Colon

• Blood supply?

SMA

Can you Label branches?

Midgut Arterial Supply

SMA

Middle Colic

Right Colic

ileocolic

Jejunal branches

Ileal branches

Appendicular

Inferior pancraetoduodenal

Hindgut

• Distal ⅓ Trasverse Colon•Descending Colon•Sigmoid Colon•Rectum

• Blood supply?

IMA

Label branches?

Hindgut

Superior rectal

IMA

Left colic

Sigmoid branches

Case 1 - history• 2 day history• Colicky central abdo pain• Vomiting last 24hrs, bilious• Bowels open 2 days ago, not passing wind• No recent weight loss/change in bowel habit/anaemia

• PMH – “bowel resection” for Crohn’s disease 20 years ago. No follow up since

- admission 2001 with adhesions, conservative - type 2 diabetes, insulin requiring

Small bowel obstruction - examination

What are you particularly seeking and trying to assess with examination?

• Hydration status of patient Mucous membranes, observations

• Signs of small bowel obstruction Abdominal distension Tinkling bowel sounds

• Potential causes of small bowel obstruction Abdominal scars Hernia Abdominal mass

• Evidence of small bowel strangulation/ischaemia or perforation Peritonism Fever

Case 1 - examinationo/e• Dry mucous membranes• Bilious vomitus on gown• HR 100, BP 130/70, T 36.9• Distended abdomen• Bowel sounds tinkling• Generally tender, no guarding• Midline laparatomy scar, no incisional hernia• No masses• Groin hernial orifices normal• PR – empty rectum

Small bowel obstruction - investigations

What initial investigations would you request and why?• Bloods FBC - ↑WCC suggests ischaemia, ↓Hb and MCV could suggest tumour U+Es – assess electrolyte loss, acute renal impairment LFTs Amylase – pancreatitis with ileus could present similarily

• AXR – seek bowel dilatation, sensitivity 60-80%• Erect CXR – seek perforation, sensitivity 80%• ABG – metabolic status of patient, evidence of

intestinal ischaemia

Biochemical markers of bowel ischaemia

• Metabolic acidosis is a late change• An isolated elevated lactate can be misleading• Persistent elevated lactate despite rehydration

suggests ischaemia

Case 1 - investigations

• WCC 7• HB 12 MCV 85• U 15 Cr 150 K 3.1 Na 134• Amylase 121

Case 1 - investigationsComment on the findings

Case 1 - AXR

•Multiple loops small bowel•Centrally positioned•Prominent valvulae coniventes•Cannot see rectum

How sensitive is AXR at detecting SBO?

~ 80%

Case 1 – initial management

• What are your priorities?• Rehydration/Resuscitation• Monitor UO + response to - catheter• Decompression – NG tube• Analgesia• DVT/PE prophylaxis

What measures would you use to guide your fluid and electrolyte administration?

• Estimation of fluid loss, likely to be litres of electrolyte-rich fluid in small bowel or lost already in vomit

• Estimation of daily requirements based on weight

• Estimation of ongoing losses, NG output• Urine output• U + Es

Case 1

• You have commenced iv fluid and electrolyte rehydration, with NG decompression and UO monitoring.

• You now need to decide on potential differential diagnoses and definitive management

What are the commonest causes for small bowel obstruction?

• Adhesions• Malignancy (including primary and metastatic

deposits)• Hernia(commonest cause in developing world)

How would you classify causes of SBO?

• Intra-luminal

• Luminal

• Extra-luminal

Intra-luminal

• Gallstone• Foreign body• Parasites

Luminal

• Tumour Primary – Small bowel eg. Lymphoma - Caecal tumour Secondary

• Inflammatory Crohn’s Radiation Post-op stricture

• Intussusception

Extra-luminal

• Adhesions Congenital Acquired

• Hernia

What are the likely differential diagnoses for our patient?

• Adhesions – laparotomy and “bowel resection” for Crohn’s disease 20 years ago

• Crohn’s stricture - seems unlikely given disease has not been active

• Should bear in mind other diagnoses, particularly malignancy, given patient’s age

Case 1 - Management

• It is 9pm on Monday, do you think this patient needs surgery tonight? Tomorrow?

What do you think are the indications for urgent surgery in small bowel obstruction?

• Evidence of strangulation – peritonism - leucocytosis• Perforation• Irreducible hernia

Case 1 - management• You decide to continue conservative treatment overnight

and r/v the patient on the WR the following morning• What features would you seek to decide whether

conservative management should be continued? NG output Peritonism Temperature HR Change in pain Flatus?

Small bowel obstruction – further investigations

• Water-soluble contrast studyo Useful in identifying patients with SBO that

are unlikely to settle with conservative Rxo Failure of contrast to reach caecum by 4 hrs

indicates surgical intervention likely to be necessary.

o Therapeutic in adhesional SBO due to osmolar effect

Gastrografin therapy for adhesional SBO

• 40 patients suspected adhesional SBO• Randomised to conventional treatment or

gastrografin• Water soluble contrast reduced hospital stay,

mean difference = –2.58; p = 0.004• Did not reduce need for surgical intervention

Burge J, Abbas SM, Roadley G et al. Randomized controlled trial of Gastrografin in adhesive small bowel obstruction. ANZ J Surg 2005; 75, 672-674.

Small bowel obstruction – further investigations

• CTo Gives information on other organs/pathology

outside the bowelo Oral contrast can have similar therapeutic

effecto Disadvantage is cost and radiation exposure

CT for small bowel obstruction

• Break out session for requesting CT from radiologist

Case 1 - CT

Laparotomy for small bowel obstruction

Describe your approach?• Midline incision• Identify transition point (Examine small bowel from DJ

flexure to IC valve)• If entire small bowel dilated with no transition point,

diagnosis of mechanical obstruction may be incorrect• Decompress small bowel by milking and aspirating

through NG tube• Take care not to tear friable distended bowel• Cover dilated bowel loops with moist packs

Laparotomy for small bowel obstruction

• When point of obstruction identified, treat cause– Divide adhesions/congenital bands– Right hemicolectomy for obstructing caecal tumour– Resect Crohn’s stricture

• Inspect any bowel caught in band/hernia for viability

• Resect ischaemic bowel and consider anastamosis vs exteriorisation

Laparotomy for Small bowel obstruction

Small bowel obstructionHow would your management differ in this 79 yr old lady with a similar history?

Small bowel obstructionSBO likely due to incarcerated inguinal/femoral hernia

Small bowel obstructionAnd this patient?