11.3 Acute Abdomen, Appendicitis, Hernias, Gallbladder & Colorectal Surgery

Approach to the Acute Abdomen

The "acute abdomen" refers to sudden, severe abdominal pain that often necessitates emergency surgical intervention. The diagnosis hinges on a detailed history, characterizing the pain (onset, character, radiation), and identifying associated symptoms like fever, nausea, vomiting, or changes in bowel habits. Physical examination is critical to assess for localized peritonitis (guarding, rigidity, rebound tenderness), which strongly mandates surgical exploration.

Diagnostic imaging is tailored to the suspected pathology. Ultrasound (US) is highly sensitive for right upper quadrant (RUQ) and pelvic pathology (e.g., gallstones, ovarian torsion) and is the safest modality for children and pregnant women. Computed Tomography (CT) of the abdomen and pelvis with intravenous contrast is the gold standard for most other acute abdominal conditions in non-pregnant adults, providing exceptional detail for appendicitis, diverticulitis, bowel obstruction, and perforation.

Acute Appendicitis

Appendicitis typically begins with vague periumbilical pain (due to visceral innervation) that migrates and localizes to the right lower quadrant (RLQ) at McBurney's point as the parietal peritoneum becomes inflamed. Classic signs include anorexia, nausea, and low-grade fever.

The Alvarado Score is a practical clinical scoring system used to predict the likelihood of appendicitis. It assigns points based on symptoms (migration of pain, anorexia, nausea/vomiting), signs (RLQ tenderness [2 points], rebound tenderness, elevated temperature), and laboratory values (leukocytosis [2 points], left shift of neutrophils).

• Score 0-3: Appendicitis highly unlikely.
• Score 4-6: Equivocal, warrants further observation or imaging (CT or US).
• Score 7-10: High probability of appendicitis, often prompting surgical consultation. Management of appendicitis is predominantly surgical (laparoscopic appendectomy), though non-operative management with antibiotics is an option for select uncomplicated cases.

Abdominal Wall Hernias

A hernia is the protrusion of an organ or fascia through the wall of the cavity that normally contains it. They can become incarcerated (irreducible) or strangulated (compromised blood supply, an emergency).

• Inguinal Hernias: Account for 75% of abdominal hernias.
  • Indirect Inguinal Hernias are the most common overall. They result from a patent processus vaginalis, protruding lateral to the inferior epigastric vessels through the deep inguinal ring into the inguinal canal, often descending into the scrotum.
  • Direct Inguinal Hernias occur due to a weakness in the transversalis fascia, protruding medial to the inferior epigastric vessels directly through Hesselbach's triangle. They rarely enter the scrotum.
• Femoral Hernias: Protrude through the femoral canal below the inguinal ligament. They are more common in women and carry a high risk of incarceration and strangulation due to the narrow neck of the femoral ring.
• Incisional Hernias: Occur at the site of a previous surgical incision due to failure of fascial healing.

Biliary Tract Disease

Gallstone disease (cholelithiasis) is common, often presenting as asymptomatic. When symptomatic, it follows a spectrum of increasing severity:

• Biliary Colic: Transient occlusion of the cystic duct by a stone, causing episodic RUQ or epigastric pain that typically resolves within a few hours. US shows stones without wall thickening.
• Acute Cholecystitis: Persistent obstruction of the cystic duct leading to gallbladder wall inflammation and infection. Patients present with constant RUQ pain, fever, leukocytosis, and a positive Murphy's sign (inspiratory arrest upon deep palpation of the RUQ). US shows pericholecystic fluid, wall thickening (>3mm), and stones. First-line management includes intravenous antibiotics and early laparoscopic cholecystectomy.
• Choledocholithiasis: Gallstones migrating into the common bile duct (CBD), presenting with jaundice, elevated bilirubin, and significantly elevated alkaline phosphatase. Often requires ERCP for stone extraction prior to cholecystectomy.
• Acute Cholangitis: Life-threatening infection of the biliary tree usually due to CBD obstruction. Clinically presents with Charcot's triad (RUQ pain, fever/chills, jaundice). In severe cases, it progresses to Reynolds' pentad (addition of hypotension and altered mental status). Treatment necessitates aggressive resuscitation, broad-spectrum antibiotics, and emergent biliary decompression (typically via ERCP).

Colorectal Surgery Principles

Bowel Obstruction: Small bowel obstruction (SBO) is most commonly caused by postoperative adhesions, followed by hernias and malignancies. Patients present with colicky abdominal pain, bilious vomiting, abdominal distension, and obstipation. Large bowel obstruction (LBO) in adults is predominantly caused by colorectal cancer, diverticular strictures, or volvulus.

Volvulus: Twisting of a bowel segment around its mesentery, leading to obstruction and vascular compromise. Sigmoid volvulus is common in elderly or institutionalized patients and appears on abdominal x-ray as a classic "coffee bean" sign. It can often be decompressed endoscopically. Cecal volvulus typically requires surgical resection.

Diverticulitis: Inflammation of diverticula (outpouchings), typically in the sigmoid colon. Uncomplicated cases present with left lower quadrant (LLQ) pain, fever, and leukocytosis, treated with bowel rest and antibiotics. CT with contrast is the diagnostic modality of choice. Complicated diverticulitis (abscess, perforation, stricture, fistula) may require percutaneous drainage or surgical intervention, such as a Hartmann's procedure for free perforation.