Week 7: Gastroenterology (2) (abdominal X-ray and nutrition) Flashcards
abdominal x-rays basics
- Check:
- Patient details
- Orientation
- Look at the x-ray- do you see anything obvious
- Then work through the GI tract in order
- Rectum (is air visible in the rectum)
- Large bowel and small bowel
- Stomach
- Kidneys, ureter and bladder
- Organs (liver and spleen
- bones
normal abdominal x-ray
- Should be able to see some air in the stomach and almost always in the sigmoid and rectum, and there should be one or two air filled small bowel loops
- Large bowel- peripherally placed with haustral markings that do not extend wall to wall
- Small bowel- more centrally placed with valvulae that extend the whole way across the lumen
large bowel on x-ray
peripherally placed with haustral amrkins that do not extend wall to waal
small bowel on x-ray
more centrally places with valvulae that extend the whole way across the lume
valvulae
plicae circulares or just small bowel folds, are the mucosal folds of the small intestine
hallmarks of intestinal obstruction
is dilated loops of bowel and absence of gas distal to the obstruction (e.g. in the rectum)
small bowel obstruction on x-ray
- Central position
- Often don’t see (need gas in the bowel to see)
- Plica/circulares/ permanent folds/ Valvulae conniventes
- Cross the entire wall
- Thin
- No gas in rectum
Causes of small bowel obstruction
- Adhesions (scar tissue) which form after surgery
- Hernias
- Colon cancer
- Strictures from an inflamed intestine caused by IBD
Large bowel obstruction on X-ray (369 rule)
Depends on the level of obstruction and ileo-caecal valve
- Peripheral position
- Haustra- sacculation’s formed by outer longitudinal muscles
- Lines only extend partially along the bowel wall
- Remember
- Transverse colon hangs down to the pelvic
- Sigmoid colon can loop and be long
In the presence of competent ileo-caecal valve…
- there is distension of the large bowel and caecum with normal looking small bowel (high risk of colonic perforation as the colon acts as a closed loop with no mechanism to decrease the luminal pressure
If ileo-caecal valve is incompetent …
there is dilation of both the large and small bowel and the risk of perforation reduced
UC and X-ray
- X-ray important for assessing flare up
- Looking for toxic mega-colin (med and surg emergency)
- lead pipe colon
classic findins of UC on x-ray
- Thickening of the colonic wall consistent with mucosal oedema secondary to active UC
signs of colititis constipation
-
- the normal colon acts to absorb water with liquid faeces entering the ascending colon from the small bowel. This gradually becomes more solid as it progresses through the colon
- E.g. in patients with left sided colitis constipation can occur in the right side of the colon due to distal inflammation important to look for on x-ray as proximal constipation cannot be diagnosed by PR exam
Toxic megacolon
‘segmental or total colonic diameter of greater than 6cm radiologically with signs of systemic upset (toxic)’
- Pan-colonic dilation that is worse in the transverse colon
- Mucosal oedema and dilated small bowel
- Urgent surgical input and colectomy with formation of an ileostomy
Volvulus
- Complete twisting of a loop of intestine around its mesenteric attachment site
- Can happen at various GI sites, however most commonly affects the sigmoid colon
risk factors for volvulus
- Chronic constipation
- Mega-colon
- Excessively mobile colon
- Elderly patients
symptoms of volvulus
- Abdominal distension
- Absolute constipation
- Abdominal pain
- X-ray findings are diagnostic
typical x-ray finding of volvulus: sigmoidal volvulus
- Coffee-bean appearance
- Caused by dilation proximal to the twist
- treatment placement of flatus tube or endoscopic decompression
x-ray caecal volvulus
- Rare
- Embryo sign
- Usually point of torsion is located in the ascending colonn
- Requires urgent surgical intervention
causes of large bowel obstruction
- Abdominal adhesions (scar tissue) from surgeries.
- Diverticulitis.
- Hernias.
- Inflammatory bowel disease (IBD).
- Radiation therapy to the abdomen or pelvis.
- Twisted intestine (rare in adults)
perforation on x-ray
- Erect chest x-ray AP
- Perotisnim is very painful
- Heart enlarged
- Perforation will cause air within the peritoneal cavity which rises when the patient is upright
Pneumoperitoneum- need erect chest X-ray
- An erect chest x-ray can show even a very small volume of abdominal gas- free air in the diaphragm
- Reference to the clinical setting is required to determine if this a life threating perforation
pneumoperitoneum and recent laparoscopic surgery
- Patient might have undergone laparoscopic surgery earlier in the day→ free gas under diaphragm is insufflated CO2- an acceptable post surgery finding
- To expand visible field for surgeon
Causes of pneumoperitoneum
- Peptic ulcer
- Diverticular
- Tumour
- Obstruction
- Trauma
- Iatrogenic
Stones and calcification
Any stones are radio-opaque and therefor visible on plain abdominal x-rays
e.g. in chronic pancreatitis
foreign bodies
What is food?
- Energy
- Macronutrients
- Protein
- Carbohydrate (CHO)
- Fat
- Micronutrients
- Vitamins
- Trace elements
Energy
- Measured in kilocalories
- 1kcal is the amount of energy required to heat 1kg of water by 1oC at sea level
- 1kcal= 4.2kj
- Not all macronutrients provide the same energy
- Fat is most energy dense- 9kcal/gram of substrate
- CHO and protein= 4kcal/gram
How much energy do we need?
- As metabolic rate is the amount of energy expended daily by humans at rest e.g. enough energy for the functioning of the vital organs
- BMR 25 kcal/kg/day
how many calories does a male vs a female need
- Women 1440 kcal (1800)
- Man 1750 kcal (2200)
additional energy is required for
- Exercise and stress factors
- Dietary induced thermogenesis (DIT)
- Eating
- Absorption
- Metabolism
- Distribution of food
protein
- Most important
- Source of nitrogen required for
- Muscle
- DNA
albumin
- Expensive in both price and energy (DIT)
Carbohydrate
- Important for storage of energy
- Stored as glycogen in liver and muscle
- Broke down to glucose and used by all organs esp the brain (glycogenolysis)
Fat
- Highest density energy storage
- Broken down to fatty acids and glycerol
- Converted to glucose and ketones in starvation state
micronutrients
vitamins
electroyltes
trace elements
Vitamins
- Cannot be synthesised in the body and need to be included in the diet
- Can be fat or water soluble
- Fat: Always do eat KitKat
- Non fat: vit B1, B2, B3, B5, B6 etc
electrolytes
- Na/K/Cl-= 1mmol/kg/day
- Water = 25ml/kig/day
trace elements
- Selenium
- Zinc
- Phosphate
When you starve… you lose….
fat
- Glycogenolysis
- Decreased insulin levels
- Decreased catecholamine levels
- Reduced metabolic rate
- Increased hormone sensitive lipase
- Gluconeogenesis from fat (glycerol)
- Ketogenesis from fat (fatty acids)
- Gluconeogenesis from AA (muscle)
when youre sick… you lose…
muscle
- No adaption
- High catecholamine levels
- No adaptive drop in insulin or BMR
- No rise in hormone sensitive lipase
- Fat not mobilised
- Massive muscle breakdown
How much should we feed when patients are in hospital
- Enough to maintain weight of patient
- Weight loss in illness equals muscle loss and therefore inhibits recovery
- E.g. if someone is obese this shouldn’t be taken as a time for them to lose weight
sarcopenia
- Age related loss of skeletal muscle
- Major cause for the increased prevalence of frailty and disability
- Muscle mass decreases, reducing mobility
if youre old and sick you have less physiological reserve…
- you lose what little muscle you have left→ more likely to become bed bound
- respiratory function decreases→ increased risk of chest infections
- reduced skin healing → pressure sores
The feeding hierarchy
Best → worse
- Normal oral feeding
- Oral nutritional supplements
- NG feed
- PEG (percutaneous endoscopic gastrostomy → a feeding tube fitted during endoscopy)/ RIG (radiologically inserted gastrotomy (no endoscopy required)
- PEG-J (percutaneous endoscopic gastrostomy with jejunal extension) / NJT (naso-jejunal tube)
- PN- parenteral nutrition
- TPN- total parenteral nutrition
Nasogastric feeding
- Short to medium term feeding
- Nutritional bridge to:
- Recovery
- Gastrostomy
- Not entirely benign
- Gastric erosions
PEG feeding
- Medium to long term feeding
- Nutritional support for:
- Chronic disease
- Radiotherapy
- Chemotherapy
- Palliative care
- Considerations
- Mouth opening
- Neck flexion
- Abdominal scars
- Respiratory reserve
- Does not protect against aspiration
- reflux
- saliva
PEG insertions
that an endoscopy is required for the insertion of a PEG feeding tube and therefore the patient has to be anatomically and physically able to have an endoscopy. If PEG is not possible a RIG can often be inserted as this is placed with direct puncture of the abdominal wall, but as this is held in place with a balloon only it does need to be regularly changed and is more prone to becoming dislodged.
RIG feeding
RIG feeding
- Gastrostomy insertion without intubation
- Nutritional support where:
- Upper GI tract inaccessible
- Respiratory disease present
- Disadvantages
- More complications than PEGs
- Have to be changed
- Relatively easily dislodged
NG/PEG/RIG feeds
- Generally 1 kcal/ml (Nutrison)
- Some 1.5-2.0 kcal/ml (Nutrison energy)
- Can also give supplementary water via NG/PEG/RIG
PN/TPN
- When do I use PN?
- Intestinal failure
- Inaccessible gut
- Obstructed gut
- Acceptable to use PN and EN together
nutuitonal assessment of malnutitions
The Malnutrition Universal Screening Tool (MUST) is a simple validated bedside tool.
Simple questions such as asking your patient about their appetite, diet history, changes in oral intake and changes in weight are key.
intravenous fluid regimine
Fluid type
- Traditionally
- ‘1 salt, 2 sweet’
- 1 litre saline = 154 mmol NaCl
- Promotes hyperchloraemic acidosis
- Reduced glomerular function
Electrolytes
- Na 1-1.5 mmol/kg/day
- 70kg man ~ 100 mmol
- K 1.0 mmol/kg/day
- 70kg man ~ 70 mmol
Normal saline
Hyperchloremic acidosis
The body maintains electro-chemical neutrality by the above equations, ie all positively charged and all negatively charged ions in the serum must always be equal. Changes in the concentration of one ion needs to be balanced by a change on the opposite side of the equation to maintain electro-chemical neutrality.
- (Na+ + K+) - (HCO3- + Cl-) = Anion gap
- (Na+ + K+ + H+) - (HCO3- + Cl-) = neutral
- H2O + pCO2 ⇔ H+ + HCO3-
- As AG decreases H+ increases
pH
- Infuse saline:
- (Na+ ⇑ + K+ + H+ ⇑ ) - (HCO3- ⇓ + Cl- ⇑ )=0
- Hyperchloraemic acidosis
- Normal saline isn’t ‘normal’ at all
“Normal” Saline is comprised of equal parts of sodium and chloride, and as such appears electrically neutral. The normal plasma chloride level however is less than that of sodium and thus when saline is infused, the serum chloride will rise to a greater degree than the sodium. The body tries to bring back electro-chemical neutrality with renal loss of bicarbonate and increased H+ production. This however results in an acidosis.
parenteral nutrition
Nutrition delivered to a patient without accessing or utilising the GI tract
- Delivered IV
when? Gut inaccessible
what is in PN
how is PN given
- Prolonged infusion over 12-24 hours via central venous catheter
- Can be given via. PICC line or Hickman line (pts can have both)
- Red- PICC
- Right – Hickman
Why use a central venous catheter
- CVC is a long flexible cannula that sits with its tip in a large vein
- This stops thrombosis and damage to vessel wall that might be caused by infusing PN into a small peripheral vein
Why is PN sometimes clear and sometimes cloudy and always covered?
- PN is clear when no lipid had been added to the bag.
- The admixture of constituents is unstable and quickly degraded by exposure to light. This means that PN should be kept covered.
How many calories in a bag of PN?
- Grams of nitrogen X 25= protein calories
- Add this to glucose and lipid calories= total calories in bag
complications of PN
1) Mechanical
- Thrombosis
- Line fracture
- Line occlusion
- Pneumothorax (usually on CVC insertion)
- Air embolus (if line left open)
2) Biochemical
- Any electrolyte disturbance
- Abnormal liver function (carbohydrate overload)
- Hyperglycaemia
- Fluid overload
3) Infectious
- CVS related bacteraemia
- CVC related septicaemia
refeeding is a biochemical triad of
- Hypophosphatemia (biochemical marker)
- Hypokalaemia
- Hypomagnesaemia
what is refeeding syndrome
When the Allied troops liberated the Nazi concentration camps at the end of World War II they were appalled by the malnourishment that they came across. Out of sympathy they fed the former inmates with rich food and chocolate. Mysteriously many of those they fed died within days.
outline how refeeding syndrome occurs
- When carbohydrate is reintroduced in starvation, the insulin levels quickly rise to accommodate the glucose load to facilitate the production of glycogen, muscle and fat.
- This process requires ATP( which uses up phosphate) and drives phosphate, potassium, magnesium and water into cells and sodium out.
- As a result the phosphate stores become further depleted and the corresponding fluid shift causes oedema.
- The hypophosphataemia reduces the production of ATP and impairs function of cardiac muscle.
- In addition 2,3-DGP is reduced in red cells and this decreases the ability of red cells to deliver oxygen to tissues.
- The combined effect of fluid shifts, reduced tissue oxygenation and impaired cardiac function is potentially catastrophic.
presentation of refeeding syndrome
- Congestive cardiac failure precipitated by fluid shifts associated with reintroduction of CHO after prolonged starvation
who is at risk of refeeding syndrome
During starvation
- During prolonged starvation insulin levels drop activating hormone-sensitive lipase which results in the breakdown of fat.
- This results in the production of fatty acids and glycerol.
- The fatty acids are converted to ketone bodies which are used as an alternative fuel to glucose, and the glycerol is used for gluconeogenesis.
- In addition muscle is also broken down to amino acids which are used for gluconeogenesis.
- During starvation state phosphate stores become depleted
Prevention of refeeding
- Reintroduction of diet should be very slow
- 5-10kcal/kg/day
- IV Phosphate infusion
- Parenteral multivitamins
- Phosphate magnesium and potassium levels monitored
characteristics of anorexia
food restriction
disordered body image
fear of weight gain
Pathophysiology of anorexia
- Extreme starvation leads to reduction in hormones including adrenaline and glucagon.
- This facilitates a rise in hormone-sensitive lipase which results in the breakdown of fat to fatty acids and glycerol producing ketones and glucose (from gluconeogenesis) respectively.
- Muscle is also broken down to produce amino acids which can be used for gluconeogenesis.
- Patients with AN have low body mass index owing to reduced body fat and lean body mass (muscle).
clinical signs of anorexia
§
complications of anorexia
Medical presentation
- AN patients do not like to attend hospital and only attend if acutely unwell
- May present with: dehydration or an inability to continue to live independently owing to their clinical state
- Recurrent hypoglycaemia secondary to severe liver dysfunction
- Sign of either occult infection 9chest/urine) or end stage AN
- Low threshold for empirical antibiotics
