Appendix A — Quick-Reference Diagnostic Algorithms

This appendix gives a fast route from a presenting symptom to the most likely diagnosis. It is organised by symptom, since this is how a patient actually presents, not by disease. Each algorithm gives the key branching questions, and points to the chapter with full detail. Use this appendix for a quick orientation. Use the full chapter for complete assessment and management.

A.1 Rectal Bleeding

Bright red, painless, on the paper or dripping → Haemorrhoids (Chapter 10).

Bright red, with severe tearing pain on defecation → Fissure-in-ano (Chapter 11).

Mixed with mucus, altered bowel habit, especially in an older patient → Anorectal malignancy (Chapter 26). Refer urgently.

With diarrhoea and abdominal pain → Inflammatory bowel disease (Chapter 28).

After receptive anal intercourse, or with discharge → Sexually transmitted proctitis (Chapter 24).

A.2 Anal Pain

Severe, tearing, during and after defecation → Fissure-in-ano (Chapter 11).

Constant, throbbing, worse sitting, with swelling → Perianal or perirectal abscess (Chapter 13).

Sudden lump, very painful, bluish → Thrombosed external pile (Chapter 10).

Pain out of proportion to visible findings, with vesicles or ulcers → Herpes proctitis (Chapter 24).

Following known trauma or a foreign body → Anorectal trauma or foreign body (Chapter 27).

A.3 Perianal Swelling or Lump

Painful, tender, red, hot → Abscess (Chapter 13).

Soft, reducible, at the anal margin → Prolapsed pile or skin tag (Chapter 10).

With an opening discharging pus or serous fluid → Fistula-in-ano (Chapter 12).

In the natal cleft, above the anus, with hair → Pilonidal sinus disease (Chapter 19).

Large, oedematous tags, with gastrointestinal symptoms → Consider Crohn's disease (Chapter 28).

A.4 Anal Discharge or Itching

Itching, worse at night, with soiling → Pruritus ani. Search for a secondary cause (Chapter 25).

Discharge from an opening near the anus → Fistula-in-ano (Chapter 12).

Discharge with painless, wart-like growths → Condylomata acuminata, HPV (Chapter 24).

Discharge with diarrhoea or bleeding → Inflammatory bowel disease (Chapter 28) or infective proctitis (Chapter 24).

A.5 Something Prolapsing or Coming Out

Reduces on its own, only on straining, painless → Haemorrhoids (Chapter 10) or early rectal prolapse (Chapter 14).

Does not reduce, or needs manual reduction, full circumference → Full-thickness rectal prolapse (Chapter 14).

Internal bulge felt on straining, not visible externally → Rectal intussusception (Chapter 15).

In a woman, with obstructed defecation and normal endoscopy → Check bimanually for a retroverted uterus (Chapter 17).

A.6 Difficulty or Straining with Defecation

Straining with digital splinting, incomplete emptying → Obstructed defecation syndrome (Chapter 16).

Narrow, ribbon-like stool, history of previous surgery → Anal stenosis (Chapter 18).

Normal endoscopy, symptoms persist, patient is a woman → Reassess for a retroverted uterus (Chapter 17).

With abdominal distension or vomiting → Consider malignant obstruction. Assess urgently (Chapter 26).

A.7 Faecal Incontinence or Soiling

History of a difficult or assisted delivery → Obstetric anal sphincter injury (Chapter 21).

Elderly or immobile patient, soiling with liquid stool → Check for faecal impaction and overflow first (Chapter 20).

After previous anorectal surgery → Review the original procedure. Consider a sphincter injury (Chapters 20 to 22).

With a coexisting rectal prolapse or large piles → Treat the underlying cause first (Chapters 10 and 14).