internal hemorrhoids

**Definition/Anatomy:** Hemorrhoids are engorged, displaced submucosal anal cushions (arteriovenous plexuses, with smooth muscle and connective tissue) that aid continence. Internal hemorrhoids arise above the dentate line from the superior hemorrhoidal (superior rectal) plexus. Typical positions: left lateral, right anterior, right posterior (3, 7, 11 o'clock in lithotomy position).

**Key anatomy (high-yield):** - Above dentate line: columnar epithelium, visceral innervation (inferior hypogastric plexus) → painless. Arterial supply: superior rectal artery (from IMA). Venous drainage: superior rectal vein → inferior mesenteric vein → portal system. Lymph: internal iliac nodes. - Below dentate line (external hemorrhoids): squamous epithelium, somatic innervation (inferior rectal nerve, from pudendal) → painful, especially when thrombosed. Drain via inferior rectal vein → internal pudendal → internal iliac → systemic (IVC). Lymph: superficial inguinal nodes. - Portal hypertension → portosystemic anastomosis between superior rectal (portal) and middle/inferior rectal (systemic) veins → rectal varices (distinct from hemorrhoids, though may coexist).

**Pathophysiology/Risk factors:** Increased intra-abdominal/anal canal pressure and downward displacement of cushions: straining, chronic constipation, prolonged sitting on toilet, diarrhea, low-fiber diet, pregnancy (increased pressure and progesterone-mediated relaxation), obesity, aging (weakened supporting tissue), pelvic masses, heavy lifting.

**Clinical presentation:** Painless bright red bleeding (hematochezia) with defecation (streaks on paper, drips into bowl, coating stool), prolapse, mucus discharge, pruritus ani, sensation of incomplete evacuation. Pain is NOT typical unless prolapsed and strangulated/thrombosed (suggests alternative dx such as anal fissure if severe pain with defecation).

**Goligher classification:** - Grade I: bleed, no prolapse - Grade II: prolapse with defecation, reduce spontaneously - Grade III: prolapse, require manual reduction - Grade IV: irreducible prolapse (risk of strangulation/thrombosis)

**Diagnosis:** History, external inspection, digital rectal exam, anoscopy (best for visualizing internal hemorrhoids). Colonoscopy/sigmoidoscopy indicated if age ≥45 (or per screening), alarm features, iron-deficiency anemia, family history, or atypical presentation — do not attribute bleeding to hemorrhoids without excluding colorectal cancer when appropriate.

**Management:** - All grades: increased fiber (25–30 g/day), fluids, stool softeners, avoid straining, sitz baths, topical agents for symptoms. - Grades I–III (failed conservative): rubber band ligation (first-line office procedure; complications: pain, bleeding, rarely pelvic sepsis), sclerotherapy, infrared coagulation. - Grade III–IV or failed other treatments: surgical hemorrhoidectomy (excisional; most effective, but most painful; complications include urinary retention, bleeding, stenosis, incontinence); stapled hemorrhoidopexy is an option. - Note: Rubber band ligation is done ONLY on internal hemorrhoids (above dentate line) — no somatic pain fibers. Banding below the line is excruciating. - Acute thrombosed external hemorrhoids: excision within 72 hours or conservative care.

**Differential diagnosis:** Anal fissure (painful, bright red blood, posterior midline, ↑ sphincter tone; treat with nifedipine/diltiazem topical, nitroglycerin), colorectal cancer, diverticular bleeding, IBD, angiodysplasia, anal fistula/abscess, rectal prolapse, rectal varices.

**Complications:** Chronic blood loss → iron-deficiency anemia, strangulation, thrombosis, ulceration, infection.

**Pearls for boards:** Painless bright red blood per rectum + known constipation/pregnancy = internal hemorrhoids. Painful, thrombosed lump at anal verge = external hemorrhoid. Internal = above dentate line = painless; external = below = painful. Dentate line is also the embryologic junction of endoderm (hindgut) and ectoderm.