5.3 Acute Surgical Conditions (Appendicitis, Cholecystitis, Bowel Obstruction)

Acute Surgical Abdominal Conditions

Evaluating the acute abdomen requires distinguishing non-operative medical conditions from surgical emergencies requiring urgent source control. Clinical evaluation focuses on anatomical localization, peritoneal signs (rebound, involuntary guarding, rigidity), and hemodynamic stability.

Acute Appendicitis

Pathophysiology & Clinical Presentation

Acute appendicitis is caused by luminal obstruction of the appendix by a fecolith (adults) or lymphoid hyperplasia (children/young adults). Obstruction leads to mucus accumulation, bacterial overgrowth, ischemic necrosis, and perforation.

• Classic Symptom Progression: Visceral periumbilical pain (T10 dermatome) $\rightarrow$ Anorexia ('hamburger sign') and nausea $\rightarrow$ Migration to Right Lower Quadrant (RLQ) somatic pain at McBurney's point (2/3 from umbilicus to anterior superior iliac spine).
• Physical Signs:
  • Rovsing Sign: RLQ pain elicited by deep palpation of the left lower quadrant.
  • Psoas Sign: RLQ pain on passive extension of the right hip (indicates retrocecal appendix).
  • Obturator Sign: RLQ pain on passive internal rotation of the flexed right hip (indicates pelvic appendix).

Diagnostic Strategy & Management

• Laboratory Findings: Mild leukocytosis ($11,000\text{--}16,000/\mu\text{L}$) with left shift; elevated C-reactive protein (CRP).
• Imaging Modality Choice:
  • Children & Pregnant Women: Ultrasound is initial choice (target: non-compressible blind-ending tubular structure $> 6\text{ mm}$ outer diameter). MRI if US inconclusive in pregnancy.
  • Non-pregnant Adults: Abdominal/pelvic CT scan with IV contrast is definitive ($> 95\%$ sensitivity/specificity; shows appendiceal enlargement $> 6\text{ mm}$, wall thickening, fat stranding, appendicolith).
• Management:
  • Uncomplicated Appendicitis: Preoperative single-dose IV antibiotics (cefazolin + metronidazole OR piperacillin-tazobactam) followed by laparoscopic appendectomy within 24 hours.
  • Perforated Appendicitis with Abscess: If patient is hemodynamically stable without generalized peritonitis, manage non-operatively with IV antibiotics and percutaneous image-guided drainage, followed by interval appendectomy in 6–8 weeks.

Biliary Tract Emergencies

Biliary pathology exists along a clinical spectrum dictated by the location of stone impaction and presence of infection.

⚠️ Exam Trap: Do NOT confuse acute cholecystitis with ascending cholangitis. Acute cholecystitis causes normal or slightly elevated bilirubin because the CBD remains open; ascending cholangitis involves common bile duct obstruction and causes severe conjugated hyperbilirubinemia, jaundice, and potential septic shock.

Intestinal Obstruction & Volvulus

Small Bowel Obstruction (SBO)

• Etiology: Postoperative adhesions (60–70% of cases), incarcerated hernias (20%), and primary/metastatic malignancy (10%).
• Clinical Presentation: High-pitched hyperactive bowel sounds early ('tinkling'), progressing to absent sounds; crampy abdominal pain, bilious vomiting, abdominal distension, and obstipation (inability to pass flatus or stool).
• Imaging Findings: Abdominal X-ray shows dilated loops of small bowel ($> 3\text{ cm}$), central distribution, multiple air-fluid levels in a step-ladder configuration, and absence of colonic gas. CT with IV contrast is definitive to identify transition point and ischemia.
• Management:
  • Uncomplicated / Partial SBO: Initial conservative trial with NPO, nasogastric (NG) tube suction decompression, IV fluid resuscitation, and correction of hypokalemia/hypochloremia. Water-soluble contrast (Gastrografin) challenge accelerates resolution.
  • Complicated / Strangulated SBO: Signs of ischemia (fever, leukocytosis, localized peritonitis, elevated serum lactate, loss of bowel wall enhancement on CT) require emergency exploratory laparotomy and resection of necrotic bowel.

Large Bowel Obstruction (LBO) & Volvulus

• Etiology: Colorectal adenocarcinoma (most common cause of LBO), followed by diverticular strictures and volvulus.
• Sigmoid Volvulus: Torsion of sigmoid colon on its mesentery, common in elderly, institutionalized patients with chronic constipation. Abdominal X-ray shows classic 'coffee bean sign' pointing to RUQ. Initial management: Endoscopic sigmoidoscopic decompression and rectal tube placement, followed by elective resection.
• Cecal Volvulus: Torsion of cecum in younger patients with mobile cecum. X-ray shows embryonic 'comma-shaped' cecum in LUQ. Treatment is emergent surgical resection (right hemicolectomy); endoscopic reduction is contraindicated due to high failure and ischemia rates.

Perforated Viscus & Peritonitis

Perforation of any hollow viscus (duodenal ulcer, perforated diverticulitis, appendiceal rupture) releases gastric/intestinal contents into the peritoneal cavity.

• Physical Exam: Board-like abdominal rigidity, severe involuntary guarding, rebound tenderness, and absent bowel sounds.
• Diagnostic Key: Upright chest radiograph or CT scan showing pneumoperitoneum (free air under the diaphragmatic domes).
• Immediate Therapy: Aggressive IV fluid resuscitation, immediate IV broad-spectrum antibiotics (covering enteric Gram-negative rods and anaerobes), and emergent exploratory laparotomy for definitive source control.