Pathophysiology and Pain Patterns

Note for Saudi GP Board (SCFHS) General Practice — Surgery block (3% of paper). The official SCFHS General Practice curriculum lists its surgical topics by domain rather than a fixed public “Topic 6” label, so this note treats Topic 6 as Acute Abdomen Assessment & Differential Diagnosis, the most commonly tested surgical topic at GP level. Adapt the labels if your cohort’s enumerated Topic 6 differs.

🟢 Lite — Quick Review (1h–1d)

Rapid summary for last-minute revision before your exam.

Acute abdomen is any abdominal pain of recent onset (<24–48 h) that may need urgent surgical action. A GP must rapidly separate peritonitis, obstruction, ischemia, and hemorrhage from non-surgical mimics (renal colic, DKA, MI).

Cardinal signs: sudden severe pain, board-like rigidity, rebound tenderness, guarding, absent bowel sounds, fever, tachycardia, vomiting.
Always check: PR exam, urine hCG in women, ECG in >40 yr, blood glucose, lactate, lipase, FBC, group & save.
Imaging: erect CXR (free air), supine abdominal film, ultrasound first-line; CT when diagnosis unclear.
The triad that mandates laparotomy: peritonitis + sepsis + free air or perforation.

Red flag	Why it matters
Sudden pain → sudden relief (silent abdomen)	Perforated viscus with chemical peritonitis
Pain out of proportion to exam	Mesenteric ischemia
Vomiting + distension + absolute constipation	Bowel obstruction
Hypotension + tachycardia + cold periphery	Intra-abdominal hemorrhage

🟡 Standard — Regular Study (2d–2mo)

Standard content for students with a few days to months.

Pathophysiology and Pain Patterns

Visceral pain (early) follows midgut derivatives to the periumbilical region and is poorly localized. Parietal peritoneal irritation produces sharp, lateralized pain at the dermatome of the inflamed organ — McBurney’s point (appendicitis), right hypochondrium (cholecystitis), LUQ (pancreatitis). Referred pain (Kehr’s sign — shoulder tip pain from diaphragmatic irritation by blood or pus) signals upper abdominal pathology.

The 5 Surgical Categories

Categorizing pain speeds triage: perforation (peptic ulcer, diverticulum), obstruction (adhesions, hernia, volvulus, tumor), inflammation (appendicitis, cholecystitis, diverticulitis, pancreatitis), ischemia (mesenteric thrombosis, strangulated hernia, testicular torsion equivalent — ovarian), hemorrhage (ruptured AAA, ectopic, ruptured spleen).

History Framework — SOCRATES-S

A GP registrar should run a structured surgical history every shift: Site, Onset, Character, Radiation, Associations (vomiting, fever, bleeding), Timing, Exacerbating/relieving factors, Severity (1–10). Ask specifically about prior abdominal surgery (adhesions), last menstrual period, NSAIDs, anticoagulants, and previous gallstones.

Investigation	What it rules in / out
Erect CXR	Pneumoperitoneum, pneumonia mimicking pain
Supine AXR	Obstruction (valvulae conniventes = small bowel, haustra = large)
Lipase ≥3× ULN	Acute pancreatitis
Lactate >2 mmol/L	Mesenteric ischemia (early sign)
β-hCG	Ectopic pregnancy (must-do in women)
D-dimer + Doppler	Mesenteric vein thrombosis, AAA extension

Top GP exam pitfalls: missing ectopic pregnancy, missing AAA in elderly back pain, attributing DKA abdominal pain to a surgical cause, ignoring testicular torsion in young men with lower abdominal pain.
Resuscitate before you image: two wide-bore IVs, fluid bolus, analgesia (does NOT mask diagnosis), NG tube if vomiting, urinary catheter.

🔴 Extended — Deep Study (3mo+)

Comprehensive coverage for students on a longer study timeline.

Special Populations and Atypical Presentations

Elderly patients frequently lack peritoneal signs due to blunted reflexes and concurrent β-blocker or steroid use — a “soft” abdomen with sepsis still demands surgical consultation. Immunosuppressed patients (transplant, HIV, chemotherapy) may have a normal WCC and minimal tenderness despite perforation; maintain a low threshold for CT. Pregnancy displaces the appendix cephalad, shifting McBurney’s point to the right flank — appendicitis then mimics pyelonephritis. Always involve obstetrics early.

Common Mistakes at GP Level

Anchoring on a single finding (e.g., a normal lipase does not exclude early pancreatitis — recheck at 6 h).
Failing to serial-examine — appendicitis evolves over 12–24 h; a documented re-assessment at set intervals is the GP’s legal safeguard.
Prescribing opioids without ruling out surgical abdomen; analgesia is fine, but a “settled” patient still needs a clear diagnosis before discharge.
Discharging a patient with biliary colic without elective follow-up — recurrence within 2 years is >50%.

Practice Prompts

A 28-year-old woman with right iliac fossa pain, BMI 32, wants to “wait it out.” Construct a 90-second shared-decision script covering red flags, Alvarado score rationale, and follow-up plan.
A 72-year-old man on warfarin presents with painless upper abdominal bruising and hemodynamic instability 48 h after a fall. List your top 3 differentials and the single investigation that changes management.

Continue your study

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Pathophysiology and Pain Patterns