What could be causing a growing bulge in the rectum or anus that sometimes disappears?

Growing Bulge in Rectum or Anus That Sometimes Disappears

The most likely diagnoses for a bulge in the rectum or anus that intermittently disappears are internal hemorrhoids (which prolapse and reduce spontaneously) or rectal prolapse, with internal hemorrhoids being more common in the general population. 1, 2

Most Likely Diagnoses

Internal Hemorrhoids (Most Common)

• Prolapsing internal hemorrhoids are the leading cause of intermittent anorectal bulging, particularly when the bulge reduces spontaneously without manual intervention 1, 3
• Internal hemorrhoids can prolapse through the anal canal during straining and spontaneously reduce when standing or lying down 1
• The intermittent nature strongly suggests second-degree hemorrhoids (prolapse with defecation but reduce spontaneously) or third-degree hemorrhoids (prolapse with defecation and require manual reduction) 3
• Associated symptoms may include mucus discharge, perianal itching, and painless bleeding, though bleeding is not always present 1, 3

Rectal Prolapse (Less Common but Important)

• Complete external rectal prolapse presents as a circumferential, full-thickness protrusion of the rectum through the anus that may be intermittent 4, 2
• Rectal prolapse has an incidence of approximately 2.5 per 100,000 inhabitants with a 9:1 female-to-male ratio 4
• The bulge in rectal prolapse is typically larger and involves concentric rings of rectal mucosa, distinguishing it from hemorrhoids which show radial bulging of discrete anal cushions 4
• Patients may experience lower abdominal pain, constipation, bloody stools, and mucus discharge 4

Critical Differential Diagnosis

Perianal Abscess or Fistula (Requires Urgent Evaluation)

• Perianal abscesses present with swelling, pain, cellulitis, and exquisite tenderness—if these symptoms are present, this becomes a medical emergency requiring prompt surgical drainage 5
• The absence of pain, fever, swelling, or discharge makes abscess unlikely 6
• Chronic anal fistulas may present as a palpable cord-like structure with intermittent drainage from an external opening 6
• Approximately one-third of anorectal abscesses lead to fistula formation 6

Thrombosed External Hemorrhoids

• These present as acutely painful, firm, bluish lumps that do not spontaneously disappear 7, 3
• The presence of severe pain within 48-72 hours of onset distinguishes thrombosed hemorrhoids from other causes 7

Diagnostic Approach

Essential Clinical Evaluation

• Physical examination including digital rectal examination, external inspection, and anoscopy is mandatory to confirm the diagnosis and exclude malignancy 1, 3
• Ask the patient to strain or bear down during examination to visualize prolapsing tissue 2
• Assess for:
  • Concentric rings (rectal prolapse) versus radial bulging of discrete cushions (hemorrhoids) 4
  • Presence of internal opening at dentate line (suggests fistula) 6
  • Signs of infection: erythema, warmth, fluctuance, tenderness (suggests abscess) 5

Red Flags Requiring Immediate Attention

• Pain, fever, or systemic symptoms suggest perianal abscess requiring urgent surgical drainage 5
• Inability to reduce the prolapse suggests incarceration with risk of strangulation 2
• Bleeding with risk factors for malignancy requires colonoscopy 1
• Approximately 11% of anorectal fistulas are caused by malignancy, so suspicious findings warrant biopsy 5

When to Order Imaging

• Imaging is generally not needed for straightforward hemorrhoids or simple rectal prolapse 5
• MRI or endoanal ultrasound is indicated for suspected complex fistulas or when surgical planning is needed 6
• CT scan with contrast is appropriate if deep abscess, malignancy, or complications are suspected 4

Management Algorithm

For Suspected Internal Hemorrhoids

1. First-line treatment is fiber supplementation (25-30g daily) and adequate hydration 1, 3
2. Conservative measures include sitz baths, avoiding straining, and stool softeners 7, 3
3. Refer for surgical evaluation if:
   • Large high-grade hemorrhoids (grade III-IV) 3
   • Failure of conservative management after 4-6 weeks 3
   • Recurrent thrombosis 3

For Suspected Rectal Prolapse

1. All patients with rectal prolapse should be referred for surgical evaluation 4, 2
2. Manual reduction can be attempted for reducible prolapse using Trendelenburg position 4
3. Preventive measures include aggressive treatment of constipation and increasing dietary fiber and water 4

For Suspected Abscess or Fistula

1. Perianal abscesses require prompt surgical drainage—do not delay 5
2. Simple superficial abscesses can undergo office-based drainage 3
3. Complex abscesses (deep, horseshoe, supralevator) require operating room drainage with broad-spectrum antibiotics covering Gram-positive, Gram-negative, and anaerobic bacteria 5
4. Rule out Crohn's disease in patients with recurrent fistulas by assessing for diarrhea, weight loss, and abdominal pain 6

Common Pitfalls to Avoid

• Never assume hemorrhoids without proper anoscopic examination—this can miss malignancy 1
• Do not delay drainage of perianal abscess, as undrained abscesses can expand into adjacent spaces and cause systemic infection 5
• Excision of thrombosed external hemorrhoids is only beneficial within 48-72 hours of pain onset 7
• Consider inflammatory bowel disease (especially Crohn's disease) in young patients with recurrent perianal disease 6
• Obtain colonoscopy if bleeding develops or if patient has risk factors for colorectal neoplasia 1