36.3 Abdomen III: Acute Appendicitis, Colonic Obstruction and Volvulus, Lower GI Bleeding, Diverticular Disease, Colorectal Polyps and Cancer, Hemorrhoids, Anal Fissure, Perianal Abscess and Fistula

Why this area matters

Appendicitis is the most common emergency operation. Colorectal cancer is among the leading cancers in the Philippines, and hemorrhoids and anal fissures are frequent outpatient complaints. The TOS tests diagnosis, operation of choice, perioperative care and complications.

Acute Appendicitis: Pathogenesis, Clinical Signs & Alvarado Score

Acute appendicitis is the most frequent surgical emergency worldwide, with a peak incidence in the second and third decades of life.

Pathophysiology & Pain Migration

1. Luminal Obstruction: The initiating event in over 80% of cases is appendiceal luminal occlusion, caused by fecaliths (appendicoliths) in adults and submucosal lymphoid hyperplasia in children and young adults (often triggered by viral illness or dehydration). Rare causes include foreign bodies, Enterobius vermicularis, and carcinoid tumors.
2. Mucus Accumulation & Visceral Pain: Continuous mucus secretion behind the obstruction increases intraluminal pressure, stretching visceral afferent C-fibers entering the spinal cord at T10. This produces dull, poorly localized, periumbilical or epigastric visceral pain, typically accompanied by anorexia and nausea.
3. Ischemia, Transmural Inflammation & Somatic Shift: Rising intraluminal pressure exceeds venular and capillary perfusion pressures, producing mucosal ischemia, bacterial invasion (Escherichia coli, Bacteroides fragilis), and transmural inflammation. When the inflammatory process contacts the parietal peritoneum (innervated by somatic spinal nerves), pain sharpens and shifts to the Right Lower Quadrant (RLQ) at McBurney's Point (located one-third the distance along a line drawn from the anterior superior iliac spine [ASIS] to the umbilicus).

Pathognomonic Physical Signs

• McBurney's Sign: Maximal point tenderness in the RLQ at McBurney's point.
• Rovsing's Sign: Palpation or deep pressure applied to the Left Lower Quadrant (LLQ) elicits pain in the Right Lower Quadrant, caused by retrograde displacement of colonic gas stretching the inflamed appendiceal cecal junction.
• Psoas Sign: Pain elicited on passive extension of the right hip while the patient lies in the left lateral decubitus position (or active flexion of the right hip against resistance in supine position). Indicates an inflamed retrocecal appendix abutting the iliopsoas muscle.
• Obturator Sign: Pain elicited on passive internal rotation of the flexed right hip while supine. Indicates an inflamed pelvic appendix abutting the obturator internus muscle.
• Dunphy's Sign: Sharp exacerbation of RLQ pain triggered by coughing, indicating localized peritonitis.

Clinical Risk Stratification: The Alvarado Score (MANTRELS)

• Interpretation & Triage:
  • Score 1-4: Low probability of appendicitis; out-patient discharge with explicit warning signs.
  • Score 5-6: Equivocal / intermediate probability; requires active observation and cross-sectional imaging (contrast-enhanced abdominal CT in adult males and non-pregnant females; ultrasound or MRI in children and pregnant women).
  • Score $\ge 7$: High probability; warrants prompt surgical consultation and emergency appendectomy (laparoscopic preferred).

More on appendicitis:

• Imaging: ultrasound in children and pregnant women; CT in adults when the diagnosis is uncertain.
• Treatment:
  • appendectomy (laparoscopic or open) with preoperative antibiotics;
  • perforated appendicitis needs postoperative antibiotics;
  • an appendiceal mass or abscess presenting late is treated with antibiotics and percutaneous drainage, followed by interval appendectomy or colonoscopy in older patients to exclude cancer;
  • antibiotics alone succeed in many selected uncomplicated cases, but recurrence is common.
• Special groups: children, the elderly and pregnant women present atypically and perforate more often.
• Appendiceal tumors: carcinoid is the most common. Mucinous neoplasms can cause pseudomyxoma peritonei.

Large bowel obstruction and volvulus

• Causes:
  • colorectal cancer is the most common in adults;
  • volvulus;
  • diverticular stricture;
  • fecal impaction;
  • hernia.
• Closed-loop obstruction with a competent ileocecal valve risks cecal perforation, especially when the cecum is over 12 cm.
• Acute colonic pseudo-obstruction (Ogilvie syndrome):
  • massive colonic dilation without a mechanical cause, in elderly, bedridden or postoperative patients;
  • treated by correcting electrolytes, stopping opioids, rectal tube and neostigmine (with cardiac monitoring), with colonoscopic decompression if needed.
• Obstructing left-sided cancer:
  • resection with a Hartmann procedure, or primary anastomosis in selected patients;
  • colonic stent as a bridge to surgery or palliation.

Lower GI bleeding

• Causes:
  • diverticular bleeding: the most common in adults; painless, often massive and arterial;
  • angiodysplasia in the elderly;
  • colorectal cancer and polyps;
  • colitis (inflammatory, infectious, ischemic);
  • hemorrhoids and fissures;
  • post-polypectomy bleeding;
  • Meckel diverticulum in children.
• Approach:
  • resuscitate;
  • exclude an upper GI source, since brisk upper bleeding can cause hematochezia;
  • check the anus;
  • colonoscopy after bowel preparation in stable patients;
  • CT angiography for active bleeding, followed by angioembolization;
  • surgery (segmental or subtotal colectomy) for persistent bleeding.

Diverticular disease

• Diverticulosis: false diverticula (mucosa and submucosa) where vessels pierce the wall, usually in the sigmoid colon in Western patients; right-sided diverticula are more common in Asians. Linked to low fiber intake and age.
• Diverticulitis: left lower quadrant pain, fever and leukocytosis. CT confirms it and stages complications.
• Hinchey classification:
  • I: pericolic abscess;
  • II: pelvic or distant abscess;
  • III: purulent peritonitis;
  • IV: fecal peritonitis.
• Management:
  • uncomplicated: outpatient care, diet and selective antibiotics;
  • abscess: antibiotics plus percutaneous drainage;
  • perforation with peritonitis (Hinchey III to IV): emergency surgery, either a Hartmann procedure (sigmoid resection with end colostomy) or resection with primary anastomosis with or without a diverting ileostomy, or laparoscopic lavage in selected Hinchey III cases;
  • elective resection for complicated disease (fistula, stricture) or recurrent attacks after case-by-case review;
  • colonoscopy after recovery to exclude cancer.
• Colovesical fistula causes pneumaturia and fecaluria.

Colorectal polyps and cancer

• Polyps:
  • adenomas (tubular, tubulovillous, villous) follow the adenoma-carcinoma sequence (APC, KRAS, TP53). Size over 1 cm, villous histology and high-grade dysplasia increase cancer risk;
  • hyperplastic polyps are usually benign;
  • sessile serrated lesions are precursors through the serrated pathway.
• Hereditary syndromes:
  • familial adenomatous polyposis (APC): hundreds of polyps and near-certain cancer, so prophylactic colectomy is done;
  • Lynch syndrome (mismatch repair genes): right-sided cancers at a young age, plus endometrial and other cancers.
• Screening for average-risk adults from about age 45 to 50: fecal immunochemical test yearly, or colonoscopy every 10 years. Start earlier and repeat more often with family history.
• Presentation by site:
  • right colon: iron deficiency anemia, weakness, a mass;
  • left colon: change in bowel habits, narrow stools, obstruction;
  • rectum: hematochezia, tenesmus, incomplete evacuation.
• Workup: colonoscopy with biopsy, CEA (baseline and follow-up), CT of the chest, abdomen and pelvis, and for rectal cancer MRI of the pelvis (and endorectal ultrasound).
• Treatment of colon cancer:
  • resection with regional lymph nodes (right hemicolectomy, left hemicolectomy, sigmoidectomy);
  • adjuvant chemotherapy (FOLFOX or CAPOX) for node-positive (stage III) and high-risk stage II disease;
  • resection of liver metastases when possible.
• Treatment of rectal cancer:
  • locally advanced tumors: neoadjuvant chemoradiation or total neoadjuvant therapy, followed by total mesorectal excision;
  • operations: low anterior resection (sphincter-preserving, often with a temporary ileostomy), or abdominoperineal resection with a permanent colostomy for tumors invading the sphincters;
  • "watch and wait" after complete clinical response in selected patients.
• Anastomotic leak after colorectal surgery presents with fever, tachycardia, peritonitis or ileus around days 3 to 7.

Anorectal disorders

• Hemorrhoids:
  • internal hemorrhoids lie above the dentate line, are painless and bleed bright red. They are graded by prolapse:
    • I: no prolapse;
    • II: prolapse that reduces spontaneously;
    • III: needs manual reduction;
    • IV: irreducible.
  • Treatment of internal hemorrhoids:
    • fiber, fluids and avoiding straining;
    • office procedures for grades I to II, and some grade III (rubber band ligation, sclerotherapy);
    • hemorrhoidectomy for grades III to IV, mixed or complicated hemorrhoids.
  • External hemorrhoids lie below the dentate line and are painful when thrombosed. Excise them within about 72 hours; after that, manage conservatively.
• Anal fissure:
  • a tear of the anoderm, usually posterior midline;
  • severe pain on defecation and bright red blood;
  • chronic fissures show a sentinel pile, a hypertrophied papilla and exposed sphincter fibers;
  • off-midline or multiple fissures suggest Crohn disease, TB, HIV, syphilis or cancer;
  • treated with fiber, sitz baths and topical nitrates or calcium channel blockers (diltiazem), or botulinum toxin, then lateral internal sphincterotomy for chronic fissures.
• Perianal abscess:
  • arises from infected anal glands (cryptoglandular);
  • painful, tender swelling with fever;
  • treated by prompt incision and drainage; antibiotics alone are inadequate, though they are added in diabetes, immunosuppression or cellulitis;
  • Fournier gangrene is a necrotizing infection of the perineum needing emergency debridement.
• Anal fistula (fistula-in-ano):
  • follows an abscess in about a third of patients;
  • Goodsall rule predicts the internal opening: external openings anterior to the transverse anal line track straight, and posterior ones curve to the posterior midline;
  • treated by fistulotomy for low fistulas, and a seton, advancement flap or LIFT procedure for high fistulas to protect continence;
  • consider Crohn disease and TB for complex or recurrent fistulas.
• Pilonidal sinus and rectal prolapse are other common anorectal problems.
• Anal cancer (squamous, HPV-related) is treated with chemoradiation (the Nigro protocol), not primary surgery.