How is pain sensed in the diaphragm?
- Torsion, rapid distention of a hollow viscus, forceful muscular contractions, and rapid stretching of solid organ serosa or capsule
- Substances released in response to local mech injury, inflammation, ischemia, necrosis
- Chemical substances released include: H+ and K+ ions, histamine, serotonin, bradykinin and other vasoactive amines, substance P, calcitonin gene-related peptide, prostaglandins, and leukotrienes
- Dull, cramping, burning, poorly localized, and more gradual in onset and longer in duration than somatic pain
- Secondary autonomic effects such as sweating, restlessness, nausea, vomiting, perspiration, and pallor often accompany
Describe abdominal pain due to visceral receptors?
- Abdominal organs transmit sensory afferents to both sides of the spinal cord
- Visceral pain is usually perceived to be in the midline, in the epigastrium, periumbilical region, or hypogastrium
Describe somatic/parietal pain
- Nerve fibers involved
- Aggravated by
- A-delta fibers
- Abdominal wall and peritoneum
- More intense, sharp, sudden, well-localized pain
- Aggravated by movement or vibration
- Lateralization possible because each side separately innervated
What are reflexive responses to somatic/parietal abdominal pain?
- Involuntary guarding
- Abdominal rigidity
How can quality of pain give you a clue to the cause of the abdominal pain?
Obstruction of Viscera
- Crampy, but can be constant
- Diffuse, or periumbilical if of small bowel
- Steady, achy
- Directly over inflamed area
- Better with laying still
What causes referred pain?
- What neurons involved
- What may cause it
- Visceral afferent neurons and somatic afferent neurons from different area converge on second order neurons
- May have embryological origin
- Cholecystitis -> shoulders or scapula
- Pancreatitis and perforated GU -> back
- Abdominal pain from non-abdominal organs
- Zoster -> Abdominal wall pain
- MI -> Epigastric pain
- MI or pneumonia -> Upper abdominal pain
How does localization vary by cause with abdominal pain?
- Visceral pain: localization unreliable
- Parietal pain: reliable location
- Most organs are bilaterally, symmetrically innervated
(EXCEPT: gallbladder, ascending/descending colon)
Difference between acute/chronic or recurrent abdominal pain?
- Acute = under 24 hrs, usually sudden onset
Rigidity upon palpation of the abdomen suggests what?
Rebound tenderness suggests what?
Absence of bowel sounds may indicate what conditions?
High pitched bowel sounds may indicate what?
What to look for on lab testing when working up abdominal pain?
- CBC: anemia, leukocytosis, leukopenia
- CMP: assess metabolic state, assess hepatobiliary disease
- Lipase (amylase): elevated in acute pancreatitis
- Pregnancy test for childbearing age women
When is x-ray useful in evaluating abdominal pain?
“Acute Abdominal Series”: Upright chest, Upright abd film, Supine abd film
- Suspected perforation
- Bowel obstruction
- Severe constipation
- Kidney stones
- Colonic pseudo-obstruction
- Sigmoid volvulus
Pros: fast, inexpensive, widely available
Cons: limited view
When is US useful in evaluating abdominal pain?
- Biliary evaluation
- Aortic aneurysm
- Ectopic pregnancy
Pros: readily available, inexpensive
Cons: limited evaluation, operator dependent, can be time consuming
When is CT useful in evaluating abdominal pain?
Chest, Abdomen, Pelvis
- Pancreatic disease
- Retroperitoneal collections
- Intra-abdominal abcess
- Some vascular processes
- Trauma-induced hematomas
- Inflammation (IBD, Diverticulitis)
Pros: excellent images, widely accessible, relatively fast
Cons: Expensive, radiation exposure
What is the key demographic for biliary disease?
Where is pain from biliary disease experienced?
Postprandial RUQ pain
- Biliary colic intermittent
What are types of biliary disease/co-conditions?
- 95% due to cholelithiasis
- Obstruction of the gallbladder leads to inflammation
- Stone in CBD
- Can cause pancreatitis
- Charcot's triad: pain, jaundice, fever
- Reynold's pentad: triad + hypoTN and change in mental status
In what condition is Charcot's triad/Reynold's pentad observed?
Causes of upper abdominal pain?
- Acute cholecystitis
Peptic ulcer disease
Describe peptic ulcer disease?
- Improved when
- Epigastric, improved after eating
- “Acute abdomen” if perforated Peritonitis/Peritoneal signs
- Rigid abdomen
- Lack of bowel sounds
Describe peptic ulcer disease
- Most common causes
- Diagnostic criteria
Most common causes:
- Epigastric pain radiating to the back
- Associated nausea and vomiting
- Elevated lipase (amylase)
- Clinical presentation
- CT characteristic findings
What may cause lower abdominal pain?
Diffuse abdominal pain sydnromes:
- Mesenteric ischemia
- Mesenteric embolism
- Mesenteric thrombosis
- Low flow mesenteric ischemia
- Small bowel obstruction
- What is it
- #1 cause of acute abdominal pain in US
- Obstruction and inflammation of appendix
- Periumbilical pain, anorexia, +/- vomiting
- Pain migrates to right lower quadrant
Diagnose by clinical presentation and imaging
Treatment is surgical
- Disease progression
- What is it
- Diverticulosis common, diverticulitis rare (5%)
- Occurs when diverticulum is obstructed with stool causing inflammation
- Usually sigmoid
- May progress to peritonitis or abscess: “complicated”
- Left lower quadrant pain, fever, obstipation
What are some causes of diffuse abdominal pain syndromes?
- Mesenteric ischemia (embolism)
Describe mesenteric ischemia/embolism
- Most common causes
- Exam findings
- Usually cardiac in origin: a.fib, mural thrombus
- Sudden, severe abdominal pain
Early examination unremarkable (pain out of proportion to examination)
Describe mesenteric thrombosis
- Atherosclerosis, usually at SMA
- Intestinal angina
- Weight loss
Describe low flow mesenteric ischemia:
- Reduced cardiac output
Describe small bowel obstruction:
- Usually from postoperative adhesions
- Malignancy, volvulus, intussusception
- Crampy, intermittent, midabdominal pain
- Abdominal distension
Acute abdominal series: dilated loops of small bowel with air-fluid levels
- IV hydration
What is normal as far as bowel habits?
- 2-3/day to 3/week
- Should be easy to pass
- Should feel relieved afterward
Pathophysiology of constipation: secondary?
- Colon disorders
- Metabolic disturbances
- Neurologic disorders
- Anal fissure
- Spinal cord lesions
Pathophysiology of constipation: idiopathic?
- Slow transit
- Functional outlet obstruction
Describe slow transit as a cause of idiopathic constipation
- Likely dysfunction of enteric smooth muscles or nerves
- Usually longstanding
- Longer exposure to mucosa will allow for more water absorption and fermentation by bacteria
Describe functional outlet obstruction as a cause of idiopathic constipation
- Ineffective opening of the anal canal or failure of the rectum to expel feces
- Pelvic floor dysfuction: lack of coordination or altered anatomy
What are alarm symptoms when working up constipation?
- Blood in the stool
- Weight loss
- Sudden onset of symptoms
What should be done on PE for constipation work up?
- Fecal column
- Examine perineum
- Cutaneoanal reflex ("anal wink")
- Rectal mass
What labs should be run when working up constipation?
- CBC: check for anemia
- BMP: hypkalemia, hypercalcemia, diabetes
- Not necessary in all pts
When should endoscopy and imaging be done for constipated pts?
No need unless alarm symptoms
- If rectal bleeding in pt under 45 yo (do sigmoidoscopy to rule out malignancy)
- If alarm symptoms (bleeding, weight loss) or age > 50, do colonoscopy
- KUB can be done to evaluate for fecal loading
What should be done for constipated pt if therapeutic trial does not yield improvement?
Sitz Marker study
- Capsule with markers ingested and then serial xrays
- If markers throughout the colon -> slow transit
- If markers in rectum -> pelvic floor dysfunction
How can constipation be treated?
- Dietary is difficult (20-30 g/day)
- May cause gas and distension
Increase fluid and exercise
- Good idea, but no evidence
- Pelvic floor dysfunction pts
- Attempt regular defecation schedule
- Chloride secretagogues
- Systemic agents
What are different laxatives/strategies?
- Wheat dextrin
- Mineral Oil
- Mg hydroxide
- Phosphate salts
- Polyethylene glycol
- Castor Oil
- Cascara fluid extract
How can you use biofeedback to treat constipation?
Pelvic floor dysfunction patients
Attempt regular defecation schedule
- Use suppositories or enemas
- Reward success
- Relearn to interpret sensation
What are chloride secretagogues and how do they help in treating constipation?
Lubiprostone- opens chloride channels and increases luminal fluid secretion
What are systemic agents and how do they help in treating constipation?
- Methylnaltrexone in opiate induced constipation
- Blocks opiate receptors on the GI tract
What surgeries may be done to treat constipation?
- Colonic inertia