BOWEL OBSTRUCTION Flashcards
What is bowel obstruction?
complete or partial disruption of the normal flow of gastrointestinal content.
What is a complete bowel obstruction?
no fluid or gas is able to pass beyond the site of obstruction.
What is incomplete bowel obstruction?
some fluid or gas is able to pass beyond the site of obstruction.
What is mechanical bowel obstruction?
physical blockage to the flow of gastrointestinal content.
What is non-mechanical bowel obstruction?
obstruction to flow secondary dilatation of the bowel in the abscence of mechanical blockage through failure of normal peristalsis
Aka ileus
What is a closed loop bowel obstruction?
the bowel is obstructed at two points, this prevents proximal or distal decompression of contents.
High-risk of rapid necrosis and perforation - surgical emergency!
What proportion of acute abdomen cases are found to have a bowel obstruction?
Around 15%
Outline the pathology after a bowel obstruction occurs?
Bowel segment has become occluded -> gross dilatation of the proximal limb of the bowel -> increased peristalsis -> secretion of large volumes of electrolyte-rich fluid into the bowel (third spacing)
What is a pseudo-obstruction in the bowel?
When the bowel is not mechanically blocked but is adynamic and not working properly
What are the most common causes of small bowel obstruction?
Post-operative adhesions or hernias
Others - IBD, malignancy, radiation enteritis, intussusception, gallstone ileus
What are the most common causes of large bowel obstruction?
Malignancy, diverticular disease or volvulus
What are post-operative adhesions?
strands of fibrous tissue that form following surgery due to the bowel being handled. It can lead to the abnormal adhesion between intra-abdominal tissue ans can trap the bowel which may leas to obstructions.
How do hernias cause small bowel obstructions?
Loops of bowel can become trapped within the hernial sac leading to obstruction and potentially strangulation and infarction if not managed urgently.
What proportion of pt with mechanical large bowel obstruction occur secondary to colorectal malignancy?
60%
20% diverticular stricture and 5% volvulus
What is paralytic ileus?
the general slow-down of the intestines and affects the entire intestinal tract (small and large bowel).
What causes paralytic ileus?
Poorly understood but commonly seen post-operatively
Other triggers - abnormal electrolytes and systemic upset
What is acute colonic pseudo-obstruction?
acute dilatation of the colon in the absence of an anatomic lesion that obstructs the flow of intestinal contents.
Aka Ogilvies syndrome
What causes acute colonic pseudo-obstruction?
Its aetiology is poorly understood and likely multifactorial. A combination of systemic illness, medications and biochemical abnormalities are implicated.
The condition is also often seen in the post-partum setting, particularly following caesarian section.
What are the symptoms+signs of bowel obstruction?
Abdominal pain (colicky/crampy)
Nausea
Absolute constipation (early in distal obstruction and late in proximal obstruction)
Vomiting (early on if proximal but late if distal obstruction)
Anorexia
Small volume diarrhoea
Obstipation
Systemic upset if significant dehydration or complication
Abdominal tenderness/peritoneum
Rebound
Abdominal distension
Abdominal mass - hernia?
Dehydration
Scars
Tympanic sound on percussion
Tinkling bowel sounds on auscultation
What does it suggest if a pt with bowel obstruction has features of guarding or rebound tenderness?w
Ischaemia is developing
What investigations should be done for a bowel obstruction?
Obs
ECG
Fluid balance
PR exam
Pregnancy test
VBG/ABG, FBC, U&E, bone profile, Magnesium, LFTs, amylase, CRP, group and saves
CT abdo/pelvis with contrast is imaging of choice but sometimes plain AXR is done
What does high lactate in bowel obstruction suggest?
Small bowel ischaemia may be present
What is seen on plain abdominal X-ray for small bowel obstruction?
Dilated bowel >3cm
Valvulae conniventes visible (lines completely crossing the bowel) creating a coiled spring appearance
What is seen on plain abdominal X-ray for large bowel obstruction?
Dilated bowel >6cm or >9cm if caecum
Haustral lines visible (indents that go Halfway are Haustra!!)
May see volvulus
What is Rigler’s sign?
Double-wall sign - gas outlining both sides of the bowel wall
Sign of pneumoperitoneum
What does a sigmoid volvulus look like on abdominal X-ray?
typical ‘coffee bean’ sign is described - sigmoid colon twisted at the root of its mesentery in LIF = dilation
Arises from left lower quadrant, haustra cannot be identified.
Multiple air-fluid levels may be seen.
Classical appearances often not present and a simple x-ray may not be diagnostic.
What does a caecal volvulus look like on abdominal X-ray?
arises from the right lower quadrant
haustral pattern tends to be maintained
One air-fluid level seen
Classical appearances often not present and a simple x-ray may not be diagnostic.
What is NELA?
National Emergency Laparotomy Audit
What is the NELA risk calculator?
can be used to give an estimate of a patient’s 30-day mortality after emergency abdominal surgery
When do we use conservative management of bowel obstruction?
In absence of signs of ischaemia or perforation
80% success rate
Often referred to as a ‘drip and suck’ management
Whats the conservative management of bowel obstruction?
Pt must be nil-by-mouth and insert an NG tube to decompress the bowel - “suck”
Start IV fluids and correct any electrolyte disturbances - “drip”
Urinary catheter and fluid balance
Analgesia
Antiemetics
Cardiac monitoring in pt with multiple co-morbidities due to fluctuations in intravascular status
What can be done if cases of bowel obstruction do not resolve initially with conservative management?
A water soluble contrast study and AXR 6 hours after to check for ongoing obstruction vs resolution
As well as checking to see for resolution, what is an added benefit of doing a water soluble contrast study in bowel obstruction cases?
The gastrograffin (contrast medium) used may have therapeutic properties in resolving obstruction due to its osmotic effect on bowel wall oedema
When is surgical intervention indicated in bowel obstructions?
Suspicion of intestinal ischaemia or closed loop bowel obstruction
A cause that requires surgical correction (such as a strangulated hernia or obstructing tumour)
If patients fail to improve with conservative measures (typically after ≥48 hours)
What surgery can be done for bowel obstructions caused by physical obstructions e.g. tumour?
Defunctioning stoma and resection with primary anastomosis via laparotomy
What are the complications of bowel obstructions?
Bowel ischaemia
Bowel perforation leading to faecal peritonitis - HIGH MORTALITY
AKI if severely fluid depleted
End-organ injury
What is a volvulus?
Intestinal twisting/looping
What are the types of volvulus and what’s most common?
Sigmoid volvulus - most common
Caecal volvulus
Midgut volvulus
Who do sigmoid volvulus often occur in?
Older pt
Those with chronic constipation
Chagas’ disease
Neurological conditions e.g. DMD or parkinsons
Psychiatric conditions
Who do cecal volvulus occur in?
All ages
Those with adhesions or are pregnant
Who does might volvulus often occur in? Why?
Infants/young children
It’s caused by anomalous intestinal development
What are the complications of a volvulus?
Mesenteric artery compression causing intestinal wall ischaemia and infarction
Intestinal wall perforation or infection
What are the signs and symptoms of a volvulus?
Abdominal tenderness or pain
Abdo distension
Bilious vomiting
Constipation
Fever
Abnormal bowel sounds that are often decreased
Tympanic on percussion
Hematochezia - may indicate bowel ischaemia/necrosis
How are volvulus diagnosed?
X-Ray
Barium enema
CT scan
What is small bowel ischaemic?
Reduced blood flow to the small bowel that will subsequently cause infarction
What is intussuspection?
the movement or ‘telescoping’ of one part of the bowel into another. The proximal bowel segment is referred to as the intussuceptum whilst the distal segment as intussucipiens
When is the peak incidence of intussusception?
Between 5-7 months of age
Rare to occur after 2
Boys are twice as likely than girls to be affected
Where does intussusception tend to occur in the GIT?
Up to 90% of cases are of the ileo-colic type whereby the distal ileum passes into the caecum through the ileocaecal valve
What are the risk factors for intussusception?
Meckels diverticulum’
Polyps
Henoch-schonlein purpura
Lymphoma and other tumours
Post-operative
Viruses e.g. rotavirus
What proportion of intussusception cases is an underlying pathological cause identified?
25%
More likely if child is older or there is a high recurrence rate
How does intussusception present?
Sudden onset of inconsolable crying episodes
Pallor
Child may have knees drawn up to chest in attempt to alleviate pain
Normal self i between episodes
Recurrent consistency in stool due to pressence of mucus and blood
Vomiting and abdominal pain if intestinal obstruction
Distension
Palpable sausage-shaped abdominal mass often in RUQ
Signs of peritoneum
Bowel sounds present
How do we investigate intussusception?
Abdominal ultrasound
Can use AXR but low sensitivity
Contrast enema (not if peritonitis or perforation)
How is interssusception managed?
Fluid resuscitation
NG tube to decompress obstructed bowel
No operative reduction - using air or contrast enema
Surgical reduction
What are the complications of interssusception?
Obstruction - surgical emergency
Perforation
Dehydration and shock
Whats the prognosis of interssusception?
Mortality rates are <1%
What is bilious vomiting?
a person’s vomit is yellowish-green, which is the color of bile
What proportion of large bowel obstructions will require surgery?
Around 75%
What are abdominal hernias?
When abdominal organs protrude through the abdominal wall at sites of weakness
What are the 2 types of abdominal hernias?
Midline hernias and groin hernias
What are the 2 types of midline abdominal hernias?
Umbilical and epigastric
What are the 2 types of groin hernias?
Inguinal and femoral
What is an incisional hernia?
When contents herniate through an incisional scar from a previous abdominal surgery
What are the layers of the abdominal wall?
Visceral peritoneum
Parietal peritoneum
Extraperitoneal fat
Transversal is fascia
Internal oblique, external oblique and transversus abdominis aponeurosis
Transversalis fascia
Superficial fascia - fatty layer (campers)
Superficial fascia - membranous layer (scarpers)
Skin
What are midline hernias?
Epigastric hernia - where herniation occurs along lines alba
Umbilical hernias - through umbilicus
What are inguinal hernias?
Abdominopelvic contents protrude through the superficial inguinal ring into the groin
What are the most common type of abdominal hernias?
Groin hernias (inguinal in 70% of cases)
What are the bounds of the inguinal canal?
Bound superiority by internal oblique and transversus abdominis
Posteriorly by transversalis fascia and conjoint tendon
Inferiorly by inguinal ligament
Anteriorly by external and internal oblique aponeurosis
What are the 2 openings of the inguinal canal?
Deep inguinal ring (orifice of transversalis muscle fascia) and superficial inguinal ring (opens in external oblique aponeurosis)
What travels within the inguinal canal?
Men - spermatic cord
Women - round ligament
Both - ilioinguinal nerve and genital branch of genitofemoral nerve
Outline the embryo logical formation of the inguinal canal?
The processus vaginalis (outpouching of parietal peritoneum) herniated through the abdominal body wall to allow the gonads to descend from the abdomen
Which group of people are groin hernias more likely in and why?
Men as they have a larger and more prominent inguinal canal which is a site of weakness in the abdominal wall
What are indirect inguinal hernias?
When the processus vaginalis fails to close after tests have passed through it and so is considered a congenital hernia. Abdominal contents herniate lateral to the inferior epigastric vessels and through the internal and external rings of inguinal canal and end up in scrotum
More likely to occur in infants and children but can be seen in adulthood
What is a direct inguinal hernia?
Result from weakening of transversalis fascia. Most commonly weakens in the posterior wall of the inguinal canal (an area called Hesselbach triangle). This may occur as a result of increased abdominal pressure e.g. heavy lifting or coughing.
The abdominal contents bulge directly through the parietal peritoneum, medial to the inferior epigastric vessels and lateral to rectus abdominis muscles, going through external inguinal ring only
Tend to occur in middle-aged and elderly population as transversalis fascia weakens with age
What is the Hesselbach triangle?
Area defined medially by the lateral border of the rectus abdominis, superomedially by the inferior epigastric vessels and inferiorly by the inguinal ligament.
What test is done to differentiate between direct and indirect inguinal hernias?
Reduce the hernia and then place pressure over the deep inguinal ring. Ask pt to cough. If the hernia protrudes despite occlusion of the deep inguinal ring then its a direct hernia; if the hernias does not protrude then this indicated an indirect hernia. (Quite unreliable)
Whats the only reliable way to differentiate direct vs indirect inguinal hernias?
In surgery - direct hernias will be medial to the inferior epigastric vessels and indirect hernias will be lateral to the vessels
What are femoral hernias?
Uncommon
Abdominal contents pass through the femoral canal (medial to femoral vein and lateral to lacunar ligament.
What are uncomplicated/reducible hernias?
When the hernia can be reduced back into the abdomen by pressing on the peritoneal sac
What are incarcerated hernias?
When hernias cannot be manually replaced back to their original position
What are the complications of incarcerated hernias?
Decreased venous and lymphatic flow = swelling and oedema of incarcerated tissue = arterial blood flow to hernial sac contents cut off (strangulation) = ischaemia and tissue necrosis
Which hernias are the most serious and require emergency surgery as soon as possible?
Strangulated hernias
What are some causes of increased intra-abdominal pressure that can lead to hernias?
Chronic cough, abdominal distension (e.g. pregnancy, obesity, ascites), staining (chronic constipation, prostatism, heavy lifting), kyphoscliolisis
What are some causes of weakened tissue that can lead to hernias?
Congenital defects - patent processus vaginalis or patent umbilical ring
Collagen disorders - ehlers-danlos syndrome, FHx
Trauma
Ageing
Chronic malnutrition
Long term corticosteroid use
What are the risk factors for inguinal hernias?
Male
~70 years old
Low BMI - more intra-abdominal fatty tissue covers and protects the deep inguinal ring
What are the symptoms of hernias?
Small hernias can be asymptomatic. Larger hernias can present with pain, visible/palpable bulge, symptoms of bowel obstruction with incarceration, redness if strangulation
Inguinal hernias may have altered sensation over scrotum/inner thigh due to compression of ilioinguinal nerve
How do femoral hernias present?
Bowel obstruction typically (always check groins as part of abdominal examination)
What are risk factors for femoral hernias?
Women
Older age >50
Low BMI
Why is having previous laparoscopic inguinal hernia repair protective against a femoral hernia?
As the preperitoneal mesh should also cover the femoral canal
What are obturator hernia?
an abnormal protrusion of abdominopelvic contents through the obturator foramen of the bony pelvis into the medial upper thigh.
Very rare! <1% of all hernias
How do obturator hernias present?
As an emergency with an acute abdomen and clinical features of bowel obstruction and/or strangulation
Often pt report self-limiting episodes of subacute obstruction at home previously
Up to 50% of pt with present with pain and altered sensation along inner thigh due to compression of obturator nerve by hernia
What is Howship-Romberg sign?
Flexing the hip makes pain along inner thigh better and internally rotating the hip makes it worse - suggests compression of obturator nerve and if positive tells us there is an obturator hernia there.
Are umbilical hernia more common in men or women?
Women, especially during or after pregnancy
Are epigastric hernias more common in men or women?
Men
What is a spigelian hernia?
a lateral ventral hernia characterised by the abnormal protrusion of abdominal contents through a defect in the fascial layers lateral to the rectus sheath - very rare!!
How are hernias diagnosed?
Physical exam findings
Ultrasound may be used to visualise hernial orifice and contents
CT/MRI to rule out other diagnoses
How are hernias managed?
May not require management
Surgical repair
What is open repair for managing inguinal hernias?
involves directly exploring the inguinal canal via a groin incision, identifying and protecting important structures (including the spermatic cord and ilioinguinal nerve), reducing the contents of the hernia back into the abdominal cavity, and placing a mesh to strengthen the deep inguinal ring and the posterior wall.
Preferred for large inguinal total hernias
What is laparoscopic repair for managing inguinal hernias?
The operation involves visualising the anatomy from within the abdominal cavity, opening the peritoneum, pulling the contents of the hernia back inside, and placing a mesh in the preperitoneal space to cover the defect.
This approach is preferred for recurrent or bilateral inguinal hernias.
What are the benefits of laparoscopic repair of hernias rather than open repair?
Decreased post-op pain and faster recovery
What is a Richters hernia?
involves the partial herniation of just one edge of the bowel wall, usually the antimesenteric border of the small intestine, as opposed to its entire circumference.
What are internal hernias?
occur when bowel loops remain within the peritoneal cavity but pass through an opening in the peritoneumor the mesentery.
What is a hiatus hernia?
herniation of abdominal contents into the chest through the oesophageal hiatus of the diaphragm.
What is the sliding type of hiatus hernia?
extremely common
usually only involves a small part of the top of the stomach slipping upwards. This impairs the function of the lower oesophageal sphincter, leading to heartburn and reflux symptoms.
What is there para-oesophageal type of hiatus hernia?
can involve the stomach and multiple other abdominal organs herniating up around the oesophagus en masse. These may result in life-threatening complications and can be very challenging to repair.
What is a diaphragmatic hernia?
Unlike hiatus hernias, which pass through an existing anatomical opening, true diaphragmatic hernias are caused by the herniation of abdominal contents through a pathological defect in the diaphragm muscle.
What is a subxiphoid hernia?
This is a high ventral hernia in the upper abdomen less than 5cm from the xiphoid process or costal margin. It usually develops as an incisional hernia following a median sternotomy, upper midline laparotomy or rooftop incision. It is unusual for these to contain bowel unless they are very large, as the left lobe of the liver covers the fascial defect in most cases. They are usually asymptomatic.
What is a suprapubic hernia?
This is a low ventral hernia occurring in the suprapubic region less than 4cm above the pubic symphysis. It usually develops as an incisional hernia following a lower midline laparotomy or C-section. These can be challenging to repair, especially in obese patients, as the lower posterior rectus sheath is relatively weak and the hernia is close to the bladder and important neurovascular structures. A piece of mesh often has to be anchored directly onto the pubic bone to adequately cover the fascial defect.
What is a lumbar hernia?
This is another rare lateral ventral hernia in which abdominal contents herniate posteriorly through the muscles of the superior or inferior lumbar triangle into the soft tissues of the back. It can occur spontaneously or as a result of surgery or torso trauma.
What is a sciatic hernia?
This is an extremely rare pelvic hernia in which abdominopelvic contents herniate through the greater or lesser sciatic foramen into the gluteal region. It may be mistaken for a buttock abscess.
What is a perineal hernia?
This involves the herniation of abdominopelvic contents through the muscles of the pelvic floor into the perineum. It occurs more frequently as an incisional hernia following radical pelvic surgery, such as abdominoperineal resection of the rectum or pelvic exenteration.
What is a traumatic hernia?
They occur as a result of high-energy blunt trauma to the abdominal wall with a sudden increase in intra-abdominal pressure which disrupts muscle and fascial layers, such as a seatbelt injury, handlebar injury or crush injury.
These mechanisms are associated with severe blunt polytrauma and patients may be critically unwell. There are often direct injuries to the underlying bowel with extensive soft tissue destruction leading to large and complex wounds.
What is a pseudo hernia?
a soft tissue bulge resulting from localised muscle paralysis secondary to trauma, nerve root compression by an intervertebral disc prolapse, peripheral neuropathy or infections such as shingles (herpes zoster). This may also be mistaken for a hernia on clinical examination but there is no actual muscular disruption and all muscle and fascial layers remain intact
Why are smaller hernias not dangerous? Why might you treat them anyway?
Because they typically only consist of fat or other non-critical structures
Overtime these defects can become bigger and slow loops of bowel to pass through the defect
What are the 3 main signs of bowel obstruction?
Distension
Vomiting
Absolute constipation
Why is treatment of femoral hernia almost always recommended straight away?
Because there’s a higher risk of complications developing in these cases
Whats the imaging of choice for small bowel obstruction?
CT contrast
What are the risk factors of abdominal wall hernias?
obesity
ascites
increasing age
surgical wounds
What blood results may suggest a strangulated hernia?
Leukocytosis and raised lactate
What are adhesions?
fibrous bands of scar tissue
What may cause adhesions?
Many occur secondary to previous surgery or intra-abdominal inflammation
however they can also be congenital.
What proportion of small bowel obstruction cases are adhesions responsible for?
60%
How do adhesions present?
They are asymptomatic but the effect of them presents with clinical features e.g. bowel obstruction, infertility, chronic pelvic pain
How can adhesions be prevented?
Correct surgical technique
Reducing intraperitoneal organ handling
Preventing thermal injury
Maintaining moist operative field
Reducing the risk of infection
Avoiding use of foreign body material
Shortening surgical time
How is uncomplicated bowel obstruction secondary to adhesions managed?
Tube decompression
Nil-by-mouth
IV fluids
Adequate analgesia
When is surgery indicated for adhesions?
For any pt with clinical features of ischaemia or perforation, or failed conservative treatment
What is adhesiolysis?
a procedure performed to break up and remove adhesions. It is a minimally-invasive procedure
When is adhesiolysis indicated?
When adhesions cause mechanical obstruction or strangulation
What is an enema?
an injection of fluid into the lower bowel by way of the rectum
What are enemas used for?
To relieve constipation
Bowel cleansing before a medical examination/procedure
What is a fecalith?
A stone made of faeces within the colon, vermiform appendix or rectum
What is an appendicolith?
When a fecalith occurs in the appendix
What is a fecaloma?
a mass of hardened feces being impacted mostly in rectum and sigmoid.
Whats the typical investigation of choice for suspected perforated bowel?
Erect chest x-ray - shows pneumoperitoneum
Gold standard is CT abdomen with contrast however! Not sure why - faster?
What are risk factors for a hiatus hernia?
Obesity
Increased intraabdominal pressure e.g. ascites or multiparity
What are the features of a hiatus hernia?
heartburn
dysphagia
regurgitation
chest pain
How do we investigate a hiatus hernia?
barium swallow is the most sensitive test
given the nature of the symptoms many patients have an endoscopy first-line, with a hiatus hernia being found incidentally
How do we manage a hiatus hernia?
all patients benefit from conservative management e.g. weight loss
medical management: proton pump inhibitor therapy
surgical management: only really has a role in symptomatic rolling hiatus cases
How do small and large bowel obstructions differ?
SBO - colicky pain that improves with vomiting. More vomiting than LBO.
LBO - continuous pain, no gas or stool can pass. Distension is more marked.
