Surgery — Emergency General Surgery, NMC MBBS licence examination syllabus (Nepal Medical Council).
The acute abdomen: which one needs an operation?
The question is never "what is the diagnosis?" first. It is "does this abdomen need a surgeon tonight?"
Abdominal pain is one of the commonest presentations in any emergency department, and the great majority of it is not surgical. The clinical skill is not naming every cause — it is sorting quickly into three groups: the patient who needs an operation now, the patient who needs admission and repeated assessment, and the patient who can safely go home.
That sorting is done mostly at the bedside. How the patient lies, whether the abdomen is rigid, whether the pain came in waves or arrived all at once — these are worth more than most tests, and they are available in the first minute.
🩺 Where this lives: The single most useful habit in the acute abdomen is examining the same patient twice, a few hours apart, yourself. Early appendicitis and early ischaemia can both look unremarkable, and a first examination that is genuinely reassuring may be reassuring only about that moment. A patient whose tenderness has localised and whose observations have drifted between two examinations has told you far more than any single scan. This is why "admit for serial examination" is a real plan, not an admission of uncertainty.
Where the pain is
WHY PAIN MOVES — visceral to parietal
VISCERAL pain comes from the organ itself. It is carried
by autonomic afferents, is poorly localised, and is felt
in the MIDLINE according to embryological origin:
foregut → epigastrium
midgut → periumbilical
hindgut → suprapubic
PARIETAL pain comes from the parietal peritoneum, which
has somatic innervation. It is SHARP, WELL LOCALISED and
worse on movement.
So APPENDICITIS classically begins as vague central pain
(midgut visceral) and MIGRATES to the right iliac fossa
once the inflamed appendix irritates the overlying
parietal peritoneum.
That migration is one of the most useful features in the
history, and it is derivable rather than memorised.
The other half of the site question is what is not in the abdomen. An inferior myocardial infarction presents with epigastric pain. A lower lobe pneumonia irritates the diaphragm and presents with upper abdominal pain. Diabetic ketoacidosis produces abdominal pain severe enough to mimic a surgical abdomen. And in any woman of reproductive age, an ectopic pregnancy is on the list until a pregnancy test says otherwise.
Reading the abdomen
EXAMINATION THAT ACTUALLY DISCRIMINATES
LOOK FIRST — before touching
Is the patient still, or restless? Peritonitis keeps a
patient motionless; colic will not let them settle.
Distension? Scars? Visible peristalsis? Hernias?
PALPATE GENTLY, starting away from the pain
GUARDING — voluntary at first, then involuntary
RIGIDITY — a board-like abdomen is generalised peritonitis
Localised tenderness with PERCUSSION tenderness is a
kinder and more reliable sign than deep rebound
ALWAYS
Examine the HERNIAL ORIFICES
Examine the SCROTUM in males — torsion presents as
abdominal pain, particularly in adolescents
Consider rectal and, where appropriate, vaginal
examination
Check the pulses and look for an expansile mass
BOWEL SOUNDS are far less useful than they are made to
sound. Absent sounds suggest ileus or peritonitis;
high-pitched sounds suggest obstruction — but neither
finding overturns the rest of the examination.
Bowel obstruction
💡 Exam angle: the transition from colicky to constant pain in obstruction is the finding that changes the plan, and it is examined repeatedly. Colic reflects peristalsis working against a blockage. When the bowel becomes ischaemic, the pain becomes continuous, the patient becomes tender and unwell, and the lactate rises. Strangulation means the bowel is dying — the answer stops being conservative management and becomes urgent surgery.
The common causes
🔍 What actually presents, and what identifies it
AppendicitisCentral pain migrating to the right iliac fossa, anorexia, low-grade fever, localised tenderness. Commonest surgical emergency in the young. Atypical in the elderly, in pregnancy (where the appendix is displaced upward) and where the appendix lies retrocaecally.
Perforated viscusSudden severe pain, rigid abdomen, unwell. Free gas under the diaphragm on an erect film. Peptic ulcer is the classic cause.
Biliary diseaseRight upper quadrant pain, often after fatty food. Cholecystitis adds fever and local tenderness; ascending cholangitis adds jaundice and rigors — a septic emergency requiring biliary drainage as source control.
PancreatitisSevere epigastric pain radiating to the back, relieved by sitting forward, with vomiting. Gallstones and alcohol are the commonest causes. Raised amylase or lipase supports it — but the level does not indicate severity. Severity is assessed clinically and by scoring, and management is supportive with attention to fluid, organ support and the underlying cause.
DiverticulitisLeft lower quadrant pain and fever in an older patient. Complications include abscess, perforation and fistula.
Mesenteric ischaemiaThe great mimic: pain grossly out of proportion to the examination findings, often in an older patient with atrial fibrillation or vascular disease, with a rising lactate. A soft abdomen does not exclude it, and by the time peritonism appears the bowel is infarcted.
Ruptured abdominal aortic aneurysmOlder patient, abdominal or back pain, shock, pulsatile expansile mass. Frequently misattributed to renal colic — a first presentation of "renal colic" over 60 deserves imaging before that label sticks.
💡 Exam angle: pain out of proportion to signs is the phrase to recognise for mesenteric ischaemia, and "renal colic" in an older patient is the phrase to distrust for a leaking aneurysm. Both are diagnoses where the abdomen feels better than the patient is, and both are lethal when the reassuring examination is believed.
Initial management
The analgesia point deserves emphasis because the old teaching persists. Withholding opioids from a patient with severe abdominal pain on the grounds that it will "mask the signs" is not supported by evidence, and it is a source of unnecessary suffering. Adequate analgesia makes examination easier, not harder — a patient who is not writhing in agony can be examined properly.
Clinical reasoning: four presentations
🔍 Case 1 — the soft abdomen
PresentationA 78-year-old in atrial fibrillation has severe central abdominal pain for four hours. She is distressed, but the abdomen is soft with only mild tenderness. Lactate 4.8.
Key cluePain grossly out of proportion to the findings, with a raised lactate, in a patient at embolic risk.
ReasoningAcute mesenteric ischaemia. Early on, the bowel is ischaemic but the parietal peritoneum is not yet involved, so the abdomen feels deceptively benign. Peritonism appears only once infarction is established.
AnswerUrgent surgical involvement and CT angiography, resuscitation, and treatment of the cause. A soft abdomen here is a feature of the diagnosis, not evidence against it.
🔍 Case 2 — the changing pain
PresentationA patient with adhesional small bowel obstruction is managed conservatively. Overnight his colicky pain becomes constant, his heart rate rises, the abdomen becomes tender, and lactate is up.
Key clueColic replaced by constant pain.
ReasoningColic reflects peristalsis against an obstruction. Constant pain with tenderness and rising lactate indicates compromised blood supply — strangulation.
AnswerStop conservative management and escalate for urgent surgery. Continuing to "wait and see" past this point costs bowel.
🔍 Case 3 — the wrong label
PresentationA 71-year-old man has sudden severe left flank pain radiating to the groin. He is restless. This is his first such episode. He is labelled renal colic and given analgesia. BP 104/62.
TrapA convincing renal colic story in an older patient.
ReasoningA ruptured or leaking abdominal aortic aneurysm mimics renal colic closely, and a first presentation of colic in this age group is unusual. The borderline blood pressure is a further warning.
AnswerExamine for a pulsatile expansile mass, check the femoral pulses, and obtain urgent imaging with vascular involvement before accepting the renal colic label. This misdiagnosis is a recognised cause of preventable death.
🔍 Case 4 — the abdomen that is not surgical
PresentationA 19-year-old has severe abdominal pain and vomiting. The abdomen is tender with some guarding. He is tachypnoeic, dehydrated, and the surgical team is called to consider laparotomy. Glucose 27 mmol/L, ketones raised.
Key cluesDeep, rapid breathing with hyperglycaemia and ketosis.
ReasoningDiabetic ketoacidosis causes abdominal pain severe enough to mimic a surgical abdomen — the DKA chapter makes the same point from the other direction. The tachypnoea is Kussmaul respiration compensating for the metabolic acidosis.
AnswerTreat the DKA and reassess the abdomen as the metabolic state corrects. Pain from ketoacidosis settles with treatment; pain from a genuine surgical problem does not — which is why reassessment, not laparotomy, is the next step.
Commonly confused
Confusion
The distinction
Why it matters
Peritonitis vs colic
Still and rigid versus restless and writhing
Visible before you touch the patient.
Visceral vs parietal pain
Vague and midline versus sharp and localised
Explains why appendicitis migrates.
Colicky vs constant in obstruction
Constant pain suggests strangulation
Changes conservative management to urgent surgery.
Soft abdomen vs no serious disease
Mesenteric ischaemia is soft early
Peritonism appears only after infarction.
Renal colic vs leaking aneurysm
First colic over 60 is suspicious
A recognised and lethal misdiagnosis.
Amylase level vs severity
The level does not grade pancreatitis
Severity is clinical, not biochemical.
Surgical abdomen vs medical mimic
DKA, MI and pneumonia all present this way
Prevents an unnecessary laparotomy.
Rapid revision
MUST-KNOW FACTS
1. The first question is whether this abdomen needs an operation, not what
the diagnosis is.
2. Visceral pain: vague, midline, by embryological origin.
3. Parietal pain: sharp, localised, worse on movement.
4. Appendicitis MIGRATES from central to right iliac fossa.
5. Peritonitis: patient lies STILL, guarding and rigidity.
6. Colic: patient RESTLESS and unable to settle.
7. Percussion tenderness is kinder and as informative as deep rebound.
8. Always examine the hernial orifices and the scrotum.
9. Bowel sounds are far less useful than they are made to seem.
10. Obstruction: colicky pain, vomiting, distension, absolute constipation.
11. Small bowel obstruction: early vomiting, less distension, ADHESIONS commonest.
12. Large bowel obstruction: late vomiting, marked distension, CANCER commonest.
13. Colic becoming CONSTANT means strangulation — urgent surgery.
14. Free gas under the diaphragm means a perforated viscus.
15. Cholangitis: jaundice, fever and rigors — needs biliary drainage.
16. Pancreatitis: epigastric pain to the back, relieved sitting forward.
17. Amylase or lipase supports the diagnosis but does NOT grade severity.
18. Mesenteric ischaemia: pain OUT OF PROPORTION to signs, rising lactate.
19. "First renal colic" over 60 — exclude a leaking aortic aneurysm.
20. PREGNANCY TEST in every woman of reproductive age.
21. ECG in every upper abdominal pain — inferior MI presents this way.
22. DKA and lower lobe pneumonia both mimic a surgical abdomen.
23. Resuscitate first — third-space losses are large and invisible.
24. GIVE ANALGESIA. It does not mask the diagnosis.
25. Serial examination by the same clinician is the most useful investigation.
💡 Exam angle: the reliable threads are (a) still versus restless separating peritonitis from colic, (b) migrating pain in appendicitis, (c) colic turning constant in obstruction, (d) pain out of proportion in ischaemia, and (e) the medical mimics — DKA, inferior MI, pneumonia, ectopic. Notice that two of the deadliest here present with an abdomen that feels better than the patient looks.
Syllabus points
The triage question: does this need an operation?
Pain by site and the organs beneath
Visceral versus parietal pain and migration
Non-abdominal causes of abdominal pain
Peritonitis versus colic at the bedside
Examination that discriminates
Bowel obstruction and its cardinal features
Strangulation: when colic becomes constant
Common causes and what identifies each
Mesenteric ischaemia and leaking aneurysm
Initial management and the analgesia myth
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