6.1 Acute Appendicitis & Peritonitis
Key Takeaways
- Acute appendicitis is initiated by luminal obstruction (fecaliths in adults, lymphoid follicular hyperplasia in children and adolescents), causing progressive intraluminal hypertension, venous congestion, mucosal ischemia, transmural necrosis, and perforation if untreated.
- Classical presentation features migration of visceral, dull periumbilical ache (T10 autonomic dermatome) to sharp, localized somatic right iliac fossa (RIF) pain at McBurney's point (parietal peritoneal inflammation), accompanied by anorexia ('hamburger sign'), low-grade pyrexia, and nausea/vomiting.
- Physical examination signs localize inflammation and anatomical position: McBurney's point tenderness, Rovsing's sign, Dunphy's sign (cough tenderness), Psoas sign (retrocecal appendix), and Obturator sign (pelvic appendix).
- The Alvarado (MANTRELS) 10-point scoring system stratifies clinical management: scores <= 4 indicate appendicitis is unlikely (discharge with red flags), scores 5–6 warrant active inpatient observation and imaging, and scores >= 7 justify urgent appendectomy.
- Generalized peritonitis is a life-threatening surgical emergency characterized by involuntary muscular guarding, 'board-like' abdominal rigidity, diffuse rebound tenderness, and absent bowel sounds, requiring urgent NPO status, aggressive crystalloid resuscitation, broad-spectrum IV antibiotics (Ceftriaxone + Metronidazole), and immediate exploratory surgery.
6.1 Acute Appendicitis & Peritonitis
Core Surgical Rule: In every patient presenting with acute abdominal pain, acute appendicitis remains the most frequent non-traumatic surgical emergency. Never administer routine opioid analgesics or oral laxatives prior to establishing a definitive clinical examination baseline, as masking peritoneal signs can delay life-saving operative intervention. The development of involuntary muscular guarding and 'board-like' rigidity indicates peritonitis, transforming an elective or semi-urgent case into an immediate resuscitation and operative emergency.
Acute abdominal pain accounts for a significant proportion of surgical admissions in Kenyan sub-county, county, and national referral facilities. Among young adults and pediatric populations, acute appendicitis is the paramount diagnosis to confirm or rule out. Because delays in recognition directly increase the rate of appendiceal perforation, phlegmon formation, intra-abdominal abscess, and septic shock, mastering the pathophysiological evolution, physical signs, and clinical scoring frameworks is critical for the practicing Clinical Officer.
1. Surgical Anatomy & Pathophysiology of Acute Appendicitis
Surgical Anatomy and Anatomical Positions
The vermiform appendix arises from the posteromedial aspect of the cecum, approximately 2 to 3 cm inferior to the ileocecal valve, where the three taeniae coli (taenia libera, taenia mesocolica, and taenia omentalis) converge. This convergence serves as an indispensable surgical landmark for locating the base of the appendix during open or laparoscopic surgery. The arterial supply is the appendicular artery, a terminal branch of the inferior division of the ileocolic artery running within the mesoappendix; being an end-artery, occlusion directly precipitates ischemic necrosis.
The anatomical position of the appendiceal tip is highly variable and dictates the subtle variations in clinical presentation:
- Retrocecal / Retrocolic (65–70%): Most common position. The appendix lies behind the cecum. Anterior peritoneal signs may be absent or minimal; patient often presents with flank pain or a positive Psoas sign.
- Pelvic (25–30%): Second most common. The tip lies over the pelvic brim near the obturator internus, rectum, and bladder. Patients may exhibit urinary frequency, dysuria, tenesmus, diarrhea, or a positive Obturator sign.
- Subcecal (1.5–2%): Tip lies beneath the cecal pole.
- Pre-ileal and Post-ileal (1–2%): Lies anterior or posterior to the terminal ileum. Post-ileal inflammation may irritate sympathetic nerves, presenting with severe diarrhea and marked toxicity.
- Ectopic positions (Rare): Subhepatic (due to incomplete cecal descent during fetal midgut rotation) or left lower quadrant (situs inversus totalis or intestinal malrotation).
[Appendiceal Luminal Obstruction]
(Fecalith / Appendicolith ~60%, Lymphoid Hyperplasia ~35%,
Foreign Body / Enterobius vermicularis ~4%,
Carcinoid / Neoplasm ~1%)
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[Continued Mucosal Secretion behind Closed Loop]
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[Elevated Intraluminal Pressure (>60 cmH2O)]
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[Venous and Capillary Compression -> Venous Congestion]
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[Mucosal Ischemia & Intramural Bacterial Translocation]
(Bacteroides fragilis, E. coli, Peptostreptococcus)
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[Arterial Thrombosis of Appendicular Artery]
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[Transmural Gangrenous Appendicitis (24-36 Hours)]
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[Perforation into Free Peritoneal Cavity (>36 Hours)]
(Localized Abscess vs Generalized Peritonitis)
The Ischemic Cascade
- Obstruction: In adults, a hard calcified fecal mass (fecalith or appendicolith) is the primary culprit. In children, infants, and young adolescents, lymphoid follicular hyperplasia within the submucosa (often secondary to viral gastroenteritis, Epstein-Barr virus, or measles) is the most frequent inciting factor. Less common causes include inspissated barium, seeds, Enterobius vermicularis (pinworms), and carcinoid tumors.
- Increased Luminal Pressure: The mucosal lining continues to secrete approximately 1 to 2 mL of fluid daily. In a closed loop, luminal pressure rapidly rises above the normal 10–15 mmHg, frequently exceeding 60–80 mmHg.
- Ischemia: Elevated intraluminal pressure exceeds capillary and venular pressures, resulting in venous engorgement and reflex arterial vasoconstriction. The mucosa becomes ischemic, compromising the mucosal epithelial barrier.
- Bacterial Invasion & Gangrene: Normal luminal commensals (Escherichia coli, Bacteroides fragilis, Klebsiella pneumoniae, and Pseudomonas) proliferate rapidly and invade the ischemic appendiceal wall. Transmural necrosis ensues, culminating in gangrene (gangrenous appendicitis).
- Perforation: Full-thickness necrosis leads to macroscopic wall perforation, commonly at the antimesenteric border where the blood supply is most precarious. Perforation typically occurs 24 to 48 hours after symptom onset, discharging purulent exudate and fecal matter into the peritoneal cavity.
2. Clinical Presentation: Visceral-to-Somatic Pain Migration
The temporal pattern of pain is the single most distinctive clinical hallmark of acute appendicitis:
Phase 1: Visceral Pain (Early 4-12 hrs) Phase 2: Somatic Pain (Late >12 hrs)
- Mediated by visceral afferent C-fibers - Mediated by somatic A-delta fibers
- Splanchnic innervation (T10 dermatome) - Parietal peritoneum inflammation
- Dull, vague, poorly localized ache - Sharp, severe, precisely localized pain
- Location: Epigastric / Periumbilical - Location: Right Iliac Fossa (McBurney's point)
- Accompanied by: Anorexia, nausea, vomiting - Accompanied by: Guarding, rebound tenderness
Cardinal Symptoms
- Abdominal Pain: Initially experienced as a vague, crampy periumbilical or epigastric discomfort. Over 6 to 12 hours, as transmural inflammation contacts the somatic parietal peritoneum of the anterior abdominal wall, the pain shifts and sharply localizes to the Right Iliac Fossa (RIF).
- Anorexia ('Hamburger Sign'): A nearly universal feature. If a patient with suspected appendicitis maintains a robust appetite or eagerly accepts food, the diagnosis should be questioned thoroughly.
- Nausea and Vomiting: Occurs in over 75% of cases. Crucially, pain almost always precedes vomiting in acute appendicitis. If vomiting occurs before the onset of pain, gastroenteritis or mechanical intestinal obstruction is significantly more probable.
- Low-Grade Pyrexia: Body temperature typically rises modestly to 37.5°C–38.2°C. A high-grade spiking fever (> 38.5°C) with rigors strongly points toward appendiceal perforation, pelvic abscess, or mesenteric pylephlebitis.
- Altered Bowel Habits: Constipation is common due to localized reflex paralytic ileus; however, diarrhea may occur when a pelvic appendix directly irritates the anterior rectal wall.
3. Physical Examination & Eponymous Signs
Defining McBurney's Point
McBurney's Point represents the surface landmark of maximum tenderness. It is located precisely one-third of the distance along a straight line drawn from the Right Anterior Superior Iliac Spine (ASIS) to the Umbilicus.
| Eponymous Sign | Examination Technique | Pathophysiological Mechanism | Clinical Significance |
|---|---|---|---|
| McBurney's Point Tenderness | Deep palpation 1/3 distance from right ASIS to umbilicus | Direct pressure compresses inflamed parietal peritoneum over appendix | Most reliable, sensitive physical sign of acute appendicitis |
| Rovsing's Sign | Deep, continuous palpation in the Left Iliac Fossa (LIF) | Displaces colon gas retrograde toward cecum, causing sudden distension of inflamed appendix | Indicates localized peritoneal irritation in the RIF |
| Psoas Sign (Cope's Sign) | Passive hyperextension of right hip with patient in left lateral decubitus position, or active hip flexion against resistance | Stretches or contracts the iliopsoas muscle directly against the overlying inflamed appendix | Highly specific for an inflamed retrocecal appendix |
| Obturator Sign | Passive internal rotation of the right flexed hip and knee in supine position | Stretches the internal obturator muscle along the lateral pelvic wall | Indicates an inflamed pelvic appendix in contact with obturator internus |
| Dunphy's Sign | Instruct patient to cough firmly while observing abdominal response | Sudden intra-abdominal pressure rise jolts inflamed parietal peritoneum | Indicates localized peritonitis; useful in uncooperative or pediatric patients |
| Blumberg's Sign (Rebound) | Deep, steady palpation of RIF followed by sudden, brisk withdrawal of hand | Rapid stretch and recoil of inflamed parietal peritoneum | Confirms localized or generalized peritoneal irritation |
4. The Alvarado (MANTRELS) Scoring Framework
The Alvarado score remains the most widely validated and utilized clinical risk stratification score for suspected acute appendicitis in emergency and district hospital settings:
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| THE ALVARADO (MANTRELS) SCORING SYSTEM |
+-----------------------------------+-----------------------------+-----------+
| CLINICAL FEATURE | ACRONYM COMPONENT | POINTS |
+-----------------------------------+-----------------------------+-----------+
| Migration of pain to RIF | M - Migratory pain | 1 point |
| Anorexia | A - Anorexia | 1 point |
| Nausea or Vomiting | N - Nausea / vomiting | 1 point |
| Tenderness in the RIF | T - Tenderness in RIF | 2 points |
| Rebound tenderness in RIF | R - Rebound tenderness | 1 point |
| Elevated temperature (>= 37.3°C) | E - Elevated temperature | 1 point |
| Leukocytosis (WBC >= 10,000/mm³) | L - Leukocytosis | 2 points |
| Shift to the left (neutrophils) | S - Shift to left (>75%) | 1 point |
+-----------------------------------+-----------------------------+-----------+
| TOTAL POSSIBLE SCORE | | 10 points |
+-----------------------------------+-----------------------------+-----------+
Clinical Risk Stratification & Disposition Pathway
- Score <= 4 (Low Risk / Unlikely):
- Appendicitis is highly improbable (< 5% risk).
- Management: Search for alternative diagnoses (urinary tract infection, mesenteric adenitis, pelvic inflammatory disease). Discharge home with clear red-flag return instructions if pain worsens or fails to resolve within 12 to 24 hours.
- Score 5 to 6 (Intermediate Risk / Equivocal):
- Appendicitis is possible; clinical picture is non-definitive (~50% risk).
- Management: Admit to surgical ward for active clinical observation. Keep NPO, place IV cannula, administer maintenance fluids, and conduct serial abdominal examinations by the same clinician every 4 to 6 hours. Perform abdominal ultrasound (graded compression ultrasound showing non-compressible blind-ending tubular structure > 6 mm outer diameter, appendicolith, or periappendiceal fat stranding). Avoid immediate antibiotics if active observation is planned, as they may obscure disease progression.
- Score >= 7 (High Risk / Highly Probable):
- Strong indication for acute appendicitis (>= 75–80% in females, >= 90% in males).
- Management: Proceed promptly to surgical consultation and urgent appendectomy. Routine CT imaging is not required in young men with typical presentations, though ultrasound or low-dose CT is advisable in females of reproductive age to exclude gynecological emergencies.
5. Peritonitis: Localized versus Generalized
Peritonitis represents inflammation of the peritoneal lining, categorized broadly into primary (spontaneous bacterial peritonitis, seen in cirrhotic ascites or nephrotic syndrome) and secondary peritonitis (arising from perforation, infection, or necrosis of an intra-abdominal viscus):
[PERITONITIS]
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[Localized Peritonitis] [Generalized Peritonitis]
- Contained by omentum and small bowel - Widespread peritoneal contamination
- Focal tenderness and localized guarding - Involuntary 'board-like' rigidity
- Bowel sounds present or hypoactive - Absent bowel sounds (silent abdomen)
- Patient relatively stable - Toxic, febrile, tachycardic, septic shock
- Early appendiceal phlegmon or mass - Appendiceal perforation / hollow viscus rupture
Physical Signs of Generalized Peritonitis
- Board-like Abdominal Rigidity: Involuntary, unyielding spasm of the rectus abdominis and anterior abdominal wall muscles that persists across the respiratory cycle. Unlike voluntary guarding (which relaxes when the patient is distracted or breathes with knees bent), involuntary rigidity cannot be overcome voluntarily.
- Severe Diffuse Rebound Tenderness: Exquisite peritoneal shock elicited by coughing, gentle percussion of the abdominal wall, or rapid release of palpation pressure.
- Silent Abdomen (Absent Bowel Sounds): Complete absence of peristaltic sounds on continuous auscultation for at least 3 minutes, reflecting diffuse paralytic ileus.
- Systemic Inflammatory Response / Septic Shock: Tachycardia (HR > 100 bpm), tachypnea (RR > 22 breaths/min), pyrexia (> 38.5°C) or hypothermia (< 36.0°C), hypotension (systolic BP < 90 mmHg), dry mucous membranes, and delayed capillary refill (> 2 seconds).
6. Preoperative Resuscitation and Surgical Management
Emergency Preoperative Resuscitation Protocol
Once generalized peritonitis or acute appendicitis requiring surgery is recognized, immediate resuscitation must precede anesthesia:
- NPO (Nil Per Os): Immediate cessation of all oral intake to prevent pulmonary aspiration during endotracheal intubation.
- Intravenous Crystalloid Resuscitation: Secure two large-bore peripheral IV cannulae (16-gauge or 18-gauge). Infuse Normal Saline (0.9% NaCl) or Ringer's Lactate rapidly (20 mL/kg bolus in shock, titrated to maintain urine output >= 0.5 mL/kg/hour, MAP >= 65 mmHg, and heart rate < 100 bpm).
- Nasogastric Tube (NGT) Decompression: Insert a wide-bore (16–18 Fr) NGT on free drainage and intermittent aspiration. Decompresses a distended stomach, relieves vomiting, and reduces aspiration risk.
- Urethral Catheterization: Place an indwelling Foley catheter with a urometer to monitor hourly urine output as an objective index of end-organ perfusion.
- Empiric Broad-Spectrum Intravenous Antibiotics: Administer parenteral antimicrobials active against enteric Gram-negative bacilli and anaerobes:
- Regimen: Ceftriaxone 1 g to 2 g IV once daily PLUS Metronidazole 500 mg IV every 8 hours.
- Alternative for Severe Sepsis / Perforation: Ampicillin + Gentamicin (5 mg/kg IV daily) + Metronidazole, OR Piperacillin/Tazobactam 4.5 g IV every 8 hours.
- Adequate Analgesia: Once the surgical decision is finalized, provide intravenous analgesia (e.g., IV Paracetamol 1 g, IV Tramadol 50–100 mg, or low-dose IV Morphine) to alleviate suffering without compromising surgical safety.
Operative Techniques
- Open Appendectomy:
- Incision Selection: Gridiron (McBurney's) incision (oblique incision perpendicular to the line connecting the ASIS to umbilicus, placed at McBurney's point, split along muscle fibers) or Lanz incision (transverse skin crease incision 2 cm below umbilicus centered on the lateral border of the rectus muscle, providing superior cosmesis).
- Technique: Divide subcutaneous tissues, split the external oblique aponeurosis along the line of its fibers, split the internal oblique and transversus abdominis muscles, grasp and incise the transversalis fascia and parietal peritoneum between artery forceps. Deliver the cecum, identify the taeniae coli, trace them to the appendiceal base, double-ligate the mesoappendix and appendicular artery, crush and transfix/ligate the base of the appendix, amputate, and either invert the stump with a purse-string / Z-stitch or leave it simple-ligated.
- Laparoscopic Appendectomy:
- Uses a 3-port technique (umbilical 10 mm port, suprapubic 5 mm port, and left lower quadrant 5 mm port). Offers reduced wound infection rates, shorter hospital stay, faster return to work, and superior diagnostic utility in females of childbearing potential.
- Appendiceal Mass / Phlegmon Management:
- If a patient presents > 5 to 7 days after symptom onset with a well-circumscribed, non-spreading mass in the RIF without signs of generalized peritonitis, this represents an appendiceal phlegmon/mass (omentum and ileal loops walling off the perforation).
- Management follows the Ochsner-Sherren regimen (conservative management): strict bed rest, NPO with gradual oral fluid introduction, IV fluids, IV broad-spectrum antibiotics, and serial boundary marking of the abdominal mass with a pen. If the mass enlarges, fever spikes, or peritonitis develops, abandon conservative therapy for emergency surgery. Following successful resolution, an interval appendectomy may be performed 6 to 8 weeks later.
A 22-year-old university student presents to the casualty department with a 24-hour history of worsening right lower abdominal pain. On physical examination, McBurney's point tenderness is equivocal, but passive extension of the patient's right hip while lying in the left lateral decubitus position elicits excruciating right lower quadrant pain. Which anatomical variation of the vermiform appendix and corresponding eponymous clinical sign does this finding indicate?
A 19-year-old male presents with right lower quadrant abdominal pain that began around the umbilicus before migrating to the right iliac fossa, accompanied by anorexia and one episode of vomiting. Physical examination reveals localized tenderness in the right iliac fossa without rebound tenderness, and his oral temperature is 37.5°C. Laboratory workup shows a white blood cell count of 8,500/mm³ with normal differential (no left shift). Based on the Alvarado (MANTRELS) scoring system, what is this patient's score and what is the recommended clinical management?
A 28-year-old female presents to the sub-county hospital with a 3-day history of acute abdominal pain that began in the epigastrium and has now become generalized. On examination, she is toxic, febrile at 39.0°C, pulse 124 bpm, and BP 90/60 mmHg. Her abdomen is rigid, board-like, exquisitely tender throughout with involuntary guarding, and bowel sounds are absent. Following aggressive IV crystalloid fluid resuscitation and nasogastric tube decompression, which empiric intravenous antimicrobial regimen and immediate surgical pathway are most appropriate under Kenya clinical guidelines?
In the classical pathophysiology of acute appendicitis, what is the primary initiating event that triggers the cascade leading to luminal hypertension, bacterial translocation, gangrene, and eventual transmural perforation?