CSD | Pain Mechanisms Aranda, MD

The Acute Abdomen

• This presentation is about the acute abdomen, a condition requiring immediate attention and treatment.
• It typically lasts from a few hours to a few days.
• Symptoms include abdominal pain and tenderness.
• Underlying pathology can originate from abdominal, thoracic, or systemic causes.
• Urgent surgical intervention may be necessary.

Objectives

• After completing this workshop, learners will be able to understand the diagnostic approach to various presentations of an acute abdomen.
• Identify symptoms (medical questioning) and signs (physical examination) in a patient presenting with an acute abdomen.
• Establish a primary diagnosis and propose at least two differential diagnoses.

Definition

• Acute abdomen is a condition requiring immediate attention and treatment, typically lasting from a few hours to a few days.
• Common symptoms include abdominal pain and tenderness.
• Underlying causes may be intra-abdominal, extra-abdominal, or systemic.

Types of Acute Abdomen

• Surgical (requiring surgery)
• Non-Surgical (not requiring surgery)

Non-Surgical Causes of Acute Abdominal Pain

• Metabolic: Diabetic ketoacidosis, tetany.
• Cardiovascular: Angina pectoris, coronary occlusion, pericarditis, embolism, thrombosis.
• Hematologic: Hemolytic anemia, purpura (Henoch-Osler), sickle-cell anemia, splenic enlargements with perisplenitis or infarction, leukemia, Hodgkin's disease.
• Infectious: Influenza, typhoid & paratyphoid fevers, poliomyelitis, malaria.
• Urinary: Pyelonephritis, acute urinary retention.
• Pulmonary: Pleurisy, pneumonia.
• Abdominal wall disorders: Herpes zoster, neuralgia, trauma.

Anatomy and Physiology of Abdominal Pain

• Pain resulting from abdominal pathology is transduced by sensory afferent fibers that travel with the autonomic and somatic nervous systems.
• These systems transduce pain differently leading to various nociceptive sensations.
• Different types of abdominal pain exist: visceral, somatic-parietal, and referred, which can influence how a person perceives pain perception.
• Cross-talk between the two systems affects the variation in abdominal distress perception.

Visceral Pain

• Deep, poorly localized, dull pain, often described as diffuse pain.
• Originates from the viscera.
• Poor localization is common, and referred pain can occur, making it distant from its origin.
• Causes include distention, inflammation, ischemia.

Somatic-Parietal Pain

• Sharp, sudden, well-localized pain.
• The source of pain stems from the parietal peritoneum.
• This covers the anterior and posterior abdominal walls and the undersurface of the diaphragm.
• Sensitivity to mechanical, thermal, and chemical stimulation leads to increased pain while handling.
• Pain is often worsened by movement or vibration.

Referred Pain

• Pain in areas distant from the diseased organ.
• Visceral and somatic afferent neurons converge which is why the pain can appear in areas far from the initial source.

Chronology of Abdominal Pain

• Pain patterns vary depending on the underlying cause.
• Some conditions have a gradual onset, while others have a sudden or rapid onset.
• The pattern of pain (whether colicky or progressive) can help diagnose the cause.

History of Abdominal Pain

• Chronological sequence
• Location of the pain
• Radiation of the pain
• Characteristics of the pain
• Aggravating/alleviating factors
• Associated symptoms

Medical Questioning

• Questions to guide the examination process.
• Details about the pain (character, location, timing, aggravating/alleviating factors).
• Associated symptoms (nausea, vomiting, fever, etc.)
• Other medical history relevant to the patient.

Medical History

• Past medical history of the patient.
• Special groups (e.g., older adults, pregnant women).
• Important to understand possible conditions specific to special groups.

Etiology of Abdominal Pain

• Common causes, including hemorrhage, infection, ischemia, perforation, inflammation, vascular, and various urologic, gynecological disorders.
• Statistics for various causes are provided based on reported cases.

Gastrointestinal Causes

• Symptoms (e.g., onset of diffuse abdominal pain, nausea, vomiting, rigidity/rebound tenderness, absent bowel sounds. pain from perforation. history of abdominal surgery)
• Diagnostic findings of gastrointestinal perforation.
• Acute management of gastrointestinal perforation.

Mechanical Bowel Obstruction

• Clinical features of mechanical bowel obstruction (colicky abdominal pain, obstipation/bloating, progressive nausea and vomiting, diffuse abdominal distention, tympanic abdomen, absence of bowel sounds).
• Diagnostic findings (e.g., dilated bowel loops, absence of rectal air shadow, multiple air-fluid levels on X-ray).

Acute Appendicitis

• Clinical features: RLQ, epigastric, and/or periumbilical pain (migrating abdominal pain), fever, nausea, anorexia. guarding, tenderness, and rebound tenderness.
• Diagnostic findings: neutrophilic leukocytosis, distended appendix on contrast-enhanced abdominal CT scans.
• Possible need for pain management checklist and/or esophageal perforation.

Diverticulitis

• Presentation: fever, lower left quadrant (LLQ) pain, constipation, and tenderness/mass in the LLQ.
• Diagnostic test results: WBC count is elevated, and CT scan shows colonic diverticula with pericolic mesenteric fat stranding.

Cholelithiasis (Gallstones)

• Symptoms: biliary colic (RUQ pain radiating to right shoulder, nausea, vomiting, postprandial onset), may lead to normal abdominal examination.
• Diagnostic findings: abdominal ultrasound, which may show gallstones.

Acute Cholangitis

• Presentation: Charcot's triad (RUQ pain, jaundice, fever) or Reynold's pentad (Charcot's triad + hypotension and confusion), may include Charcot's triad.
• Diagnostic tests: elevated WBC, CRP, liver function tests (including ALP, AST, ALT, GGT, total bilirubin), and abdominal ultrasound.

Acute Pancreatitis

• Symptoms: severe epigastric pain radiating to the back, nausea, vomiting, epigastric tenderness/guarding/rigidity, hypoactive bowel sounds, possibly fever, history of gallstones or alcohol use.
• Diagnostic findings: elevated lipase and amylase, hypokalemia, abdominal ultrasound/CT scan with IV contrast (for pancreatic edema, peripancreatic fat stranding, or gallstones).

Ruptured Abdominal Aortic Aneurysm (AAA)

• Symptoms: sudden severe, central abdominal pain, radiating to the back, hypotension or shock, pulsatile mass in the abdomen, Grey Turner sign, and/or Cullen's sign.
• Diagnostic findings: elevated blood pressure, abnormal abdominal ultrasound/CT (with angiography), free fluid in the retro/intraperitoneal space.

Aortic Dissection

• Symptoms: sudden onset, severe tearing chest/abdominal pain radiating to the back, hypotension, syncope, neurological symptoms, asymmetric blood pressure, pulse deficit, new diastolic murmur (due to aortic regurgitation).
• Diagnostic tests/findings: ECG (nonspecific ST-segment changes), CXR (widening of the aorta), CT angiography (intimal flap, false lumen).

Acute Urinary Retention

• Symptoms: difficulty urinating, suprapubic pain, distended bladder, restlessness, and/or acute distress.
• Diagnostic tests: urinalysis and culture, assessment of BUN/creatinine, and/or ultrasound of the urinary tract.

Testicular Torsion

• Symptoms: severe lower quadrant or testicular pain, nausea, and vomiting, inappropriately elevated position of the affected testicle.
• Diagnostic findings: Doppler ultrasound (twisting of the spermatic cord, reduced perfusion of the testicle).

Nephrolithiasis

• Symptoms: severe (unilateral/colicky) flank pain, hematuria, nausea, vomiting, dysuria, frequency, and urgency.
• Diagnostic findings: urine dipstick and urinalysis, urine microscopy (for crystals), abdominal/pelvic CT scan, or ultrasound.

Ovarian Torsion

• Symptoms: sudden unilateral lower abdominal/pelvic pain, nausea & vomiting, unilateral iliac fossa tenderness.
• Diagnostic findings: pelvic ultrasound.

Pelvic Inflammatory Disease (PID)

• Symptoms: pelvic/lower abdominal pain, cervical motion tenderness, uterine tenderness, adnexal tenderness, mucopurulent cervical/vaginal discharge.
• Diagnostic criteria: NAAT for gonorrhea/Chlamydia, wet mount for leukorrhea, trichomoniasis, & bacterial vaginosis; HIV and syphilis tests; pelvic ultrasound for suspected tuboovarian abscess.

Acute Coronary Syndrome

• Symptoms: severe, dull pressure/squeezing sensation in the chest or epigastric region, radiating pain down arm or left shoulder, nausea, vomiting (may improve with nitroglycerin), diaphoresis, dizziness, and lightheadedness.
• Diagnostic findings: ECG (nonspecific changes, ST-segment elevation/depression), increased/normal troponin, TTE (hypokinesis, regional wall motion abnormalities ).

Acute Mesenteric Ischemia

• Symptoms: severe, diffuse abdominal pain, out of proportion to physical findings, pain may include vomiting, diarrhea, melena, hematochezia.
• Diagnostic findings: elevated lactic acidosis, hyperkalemia, leukocytosis, abnormal imaging (pneumatosis intestinalis).

Ruptures

• Conditions that can lead to acute abdomen.
• Rupture of abdominal structures can be catastrophic with rapid clinical worsening.

Workup

• Strategy for workup is outlined depending on the side of pain.
• Imaging and lab tests are recommended based on suspected causes.

Medical Examination Techniques

• Checklist for common examination methods includes inspection, palpation, & percussion.
• This outlines critical questions and relevant findings.

Laboratory Tests.

• Common lab tests for abdominal pain, including blood coagulation tests (PT, PTT, INR), D-dimer, cultures, & troponins.

Bibliography

• A list of references used in the provided material on the topic.

Test your knowledge of pain mechanisms, including nociceptors and types of pain such as visceral and somatic. This quiz covers key concepts in understanding how different types of pain are characterized and assessed. Perfect for students studying anatomy and physiology.