Acute abdomen: differential diagnosis, assessment and surgical management

Ask Rezzy/Acute abdomen: differential diagnosis, assessment and surgical management

Rezzy

Acute abdomen is one of those topics that can feel like a whirlwind when you're on a surgical rotation! It basically refers to any sudden, severe abdominal pain that might require urgent surgical intervention. Since you're prepping for the UKMLA AKT, we really need to focus on the "surgical sieve" for differentials and the "ABCDE" approach for assessment.

Differential Diagnosis: The Surgical Sieve

To keep things organized, it's helpful to think about the location of the pain. This is often the first clue to the underlying pathology.

Right Upper Quadrant (RUQ): Biliary colic, Cholecystitis, Ascending cholangitis, or even Hepatitis.
Left Upper Quadrant (LUQ): Splenic infarct or rupture (think trauma!), Gastritis.
Right Lower Quadrant (RLQ): ==Appendicitis== (the classic!), Ectopic pregnancy, Mesenteric adenitis.
Left Lower Quadrant (LLQ): Diverticulitis, Volvulus.
Epigastric: Peptic Ulcer Disease (PUD), Pancreatitis, Myocardial Infarction (don't forget the heart!).
Generalized: Peritonitis (due to perforation), Bowel obstruction, Ischaemic colitis.

Assessment: The "Surgical" Approach

When a patient rolls in with an acute abdomen, your assessment needs to be rapid but thorough.

ABCDE Assessment: Always start here. Is the patient hemodynamically stable? If they are tachycardic and hypotensive, you're thinking shock (septic or hemorrhagic).
History (SOCRATES): Pay close attention to the onset (sudden suggests perforation or vascular event) and associated symptoms (vomiting, change in bowel habits, or urinary symptoms).
Physical Exam:
- Inspection: Look for scars, distension, or visible peristalsis.
- Palpation: Check for guarding (voluntary) vs. rigidity (involuntary - a sign of peritonitis). ==Rebound tenderness== is a classic sign of peritoneal irritation.
- Percussion: Shifting dullness for ascites or loss of liver dullness (suggests pneumoperitoneum).
- Auscultation: Absent bowel sounds (ileus/peritonitis) vs. "tinkling" sounds (obstruction).

Surgical Management Principles

The goal isn't always to rush to theatre, but to decide who needs to go and when.

Resuscitation: "Drip and Suck" — IV fluids for hydration and an NGT (Nasogastric Tube) if there's vomiting or obstruction.
Analgesia: Don't withhold pain relief! It doesn't "mask" the signs as much as old textbooks suggest.
Antibiotics: Start broad-spectrum IV antibiotics if you suspect infection or perforation.
The "Decision to Operate": This is usually based on clinical signs of peritonitis, evidence of perforation on imaging (like free air under the diaphragm), or a clear surgical cause like a strangulated hernia.

I'll pull up a table that compares the most common causes of acute abdomen to help you differentiate them quickly during the exam.

Condition	Typical Pain Location	Key Clinical Features	Initial Investigation
Acute Appendicitis	Periumbilical moving to RIF	Anorexia, McBurney's point tenderness, guarding	Clinical / Ultrasound / CT
Acute Cholecystitis	RUQ (may radiate to R shoulder)	Murphy's sign positive, fever, leukocytosis	Ultrasound Abdomen
Perforated Peptic Ulcer	Epigastric (sudden, generalized)	Board-like rigidity, shock, history of NSAIDs	Erect Chest X-ray (Free air)
Acute Pancreatitis	Epigastric (radiates to back)	Vomiting, history of alcohol or gallstones	Serum Amylase/Lipase
Bowel Obstruction	Generalized / Central	Vomiting, distension, absolute constipation	Abdominal X-ray (Dilated loops)
Ruptured AAA	Mid-abdominal / Back	Pulsatile mass, hypotension, sudden collapse	Bedside Ultrasound / CT Angio

That table should help you keep the "big hitters" straight for the AKT. One of the most critical things to recognize on an exam is pneumoperitoneum (free air under the diaphragm), as it's a surgical emergency.

Let me find a clinical image of an erect chest X-ray showing this, so you know exactly what to look for.

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