Hemorrhoid

Basics

General:
- Normal venous sinusoids of the distal rectum and proximal anal canal
- Normal vascular cushions of anal canal that contribute to anal continence
- Arteriovenous shunt system exists at the level of the internal hemorrhoids that accounts for the bright red blood per rectum
When the hemorrhoids become symptomatic, hemorrhoid disease develops
Do not cause pain unless thrombosed or strangulated
Discrete masses of thick submucosa contain:
- Blood vessels
- Smooth muscle
- Elastic and connective tissue
Sliding down of part of anal canal lining
External hemorrhoids:
- Vessels situated below dentate line
- Covered by skin/anoderm
- Drain to internal iliac veins
Internal hemorrhoids:
- Submucosal vessels above dentate lines
- Drain to portal system
- Usually at left lateral, right posterolateral, and right anterolateral positions
- Grade 1: Painless, bleeding
- Grade 2: Prolapse with bowel movement (BM), spontaneously reduce
- Grade 3: Prolapse with BM, require manual reduction
- Grade 4: Chronically prolapsed, not reducible

Exact cause unknown
Gravitational forces and abdominal pressure cause distention of the sinusoids
Associated with straining and irregular bowel habits:
- Hard, bulky stools or diarrhea cause tenesmus/straining
- Push anal cushions out of anal canal
- Weaken submucosal tissue leading to prolapse
Higher resting anal pressures:
- Erect posture
Heredity:
- Absence of valves in veins
Increased intraabdominal pressure:
- Ascites
- Pregnancy
Portal hypertension

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