Chapter 15 — Rare but Important Conditions Non-Surgeons Should Recognise

Purpose: ten uncommon conditions that hide behind common complaints — recognise the pattern, know the red flags, and send the patient down the right pathway the first time.

🎨 INFOGRAPHIC / VISUAL BLUEPRINT — CHAPTER 15

• Chapter colour palette: Graphite (#374151) header bar, Cloud Grey (#F3F4F6) panels, Ink (#111827) text, with a single red accent for emergencies.
• Hero graphic: A “field guide” grid of ten tiles, each with a small icon, the one clue that should make you think of the condition, and a coloured urgency dot.
• Icon set: Radiation trefoil, ulcer, concentric rings, nodule chain, white plaque, eczema patch, lightning bolt, stone (faecal mass), white-cell shield, red siren.
• Bedside aphorism banner: “When the common diagnosis does not fit, the rare one is often hiding in plain sight.”

1. Presentation and Red Flags

Table 15.1 — Ten rare conditions: how they present

2. Work-Up, Initial Management, and Referral Urgency

Table 15.2 — Ten rare conditions: what to do

Algorithm 15.1 — When the common diagnosis does not fit

[ANORECTAL COMPLAINT THAT DOES NOT FIT THE USUAL PATTERN]
|
+-- Prior pelvic radiotherapy + bleeding or urgency
|     -> radiation proctitis; exclude recurrence; GI
+-- Straining + mucus + anterior rectal ulcer or polyp
|     -> SRUS: BIOPSY (it mimics cancer); biofeedback
+-- Recurrent nodules and tracts in groin or buttocks
|     -> hidradenitis: dermatology +/- surgery
+-- White atrophic or well-demarcated itchy plaque
|     -> dermatosis vs HSIL vs Paget: BIOPSY
+-- Fleeting severe pain, normal exam -> proctalgia fugax
|   Long ache + tender levator -> levator ani syndrome
+-- Older or immobile, faecal mass + pain or fever
|     -> stercoral ulcer or PERFORATION: CT + surgeon
+-- Neutropenic + fever + abdominal pain or diarrhoea
|     -> neutropenic enterocolitis: antibiotics within
|        1 h, CT, haematology + surgery
+-- Days after banding, haemorrhoidectomy, or stapling:
    pain + fever + urinary difficulty
      -> PELVIC SEPSIS: emergency (Chapter 03)

3. Dangerous Mimics

Table 15.3 — Rare conditions and what they are mistaken for

4. Role-Targeted Action Boxes

🚑 ER DOCTOR ACTION BOX

• Post-procedure pain with fever or urinary difficulty is pelvic sepsis until proven otherwise.
• Older patient with impaction and new abdominal pain or fever: CT for stercoral perforation before any enema.
• Neutropenic fever with abdominal pain: antibiotics within 1 hour, CT, haematology and surgery together.

🩺 FAMILY MEDICINE / GP CLINIC BOX

• Ask about previous pelvic radiotherapy in every patient with rectal bleeding.
• Biopsy, or refer for biopsy, any persistent plaque or ulcer that does not behave as expected.
• Hidradenitis: support weight loss and smoking cessation; refer early to dermatology.

🏥 ER & WARD NURSE CARE AND SBAR BOX

• Neutropenic patients: no rectal temperatures, enemas, or suppositories (Appendix C).
• Post-procedure calls: escalate fever above 38.0 °C, worsening pain, or inability to pass urine immediately.

💊 CROSS-SPECIALTY PRESCRIBING TRAP

• Potent topical steroids are correct for lichen sclerosus (under specialist guidance) but wrong for undiagnosed perianal rashes.
• Enemas in suspected stercoral perforation or neutropenia can be lethal.

⛔ NEVER DO THIS

• Never treat an anorectal ulcer as SRUS without a biopsy.
• Never give an enema to a patient with suspected stercoral perforation.
• Never discharge a post-banding patient with fever and urinary retention.
• Never label pain as functional before structural causes have been excluded.

📝 COMMON DOCUMENTATION ERROR

• Radiotherapy history, immunosuppression, and recent anorectal procedures not recorded in the bleeding or pain history.

📨 REFERRAL URGENCY BOX

The Patient in Front of You — Chapter 15 Mini-Case

🧑‍⚕️ THE PATIENT IN FRONT OF YOU

A 78-year-old care-home resident on regular morphine has not opened her bowels for 6 days. She develops sudden lower abdominal pain and a temperature of 38.4 °C. The night team has prescribed a phosphate enema.

Step 1 Stop the enema. Sudden pain and fever in an impacted older patient suggests stercoral ulceration or perforation.

Step 2 Assess: examine for peritonism; bloods including lactate; urgent CT abdomen and pelvis.

Step 3 Act: perforation or peritonitis → resuscitation, antibiotics, emergency surgery. No perforation → gentle disimpaction, oral macrogol, opioid review.

Step 4 Prevent: laxatives with every regular opioid; bowel chart in the care home.

Board-Style Question — Chapter 15

A 26-year-old man with years of straining and mucus has a 1.5 cm ulcer on the anterior rectal wall, 8 cm from the anal verge, at sigmoidoscopy. What is the most important next step?

• A. Reassure him that this is SRUS and start fibre
• B. Take biopsies of the ulcer
• C. Arrange immediate rectal resection
• D. Start oral prednisolone for presumed IBD

Answer and explanation

• ❌ A SRUS is likely, but the diagnosis cannot be made safely without histology.
• ✅ B Correct. SRUS can mimic rectal cancer (and IBD); biopsy confirms the diagnosis before treatment with fibre, stopping straining, and biofeedback.
• ❌ C Resection is not indicated before diagnosis and is rarely needed for SRUS.
• ❌ D Steroids should not be started without a histological diagnosis.

Ten-Item Rapid Revision Checklist — Chapter 15

• 01 I ask about pelvic radiotherapy in patients with rectal bleeding.
• 02 I biopsy suspected SRUS before treating it.
• 03 I recognise hidradenitis and its overlap with Crohn’s disease.
• 04 I biopsy persistent perianal plaques (Paget disease, HSIL, lichen sclerosus).
• 05 I apply Rome IV criteria to functional anorectal pain after excluding structural disease.
• 06 I suspect stercoral perforation in impacted older patients with pain or fever.
• 07 I avoid enemas in suspected perforation and neutropenia.
• 08 I treat neutropenic enterocolitis as an emergency.
• 09 I recognise the post-procedure pelvic sepsis triad.
• 10 I use the urgency column of Table 15.2 for every referral.

Five Most Dangerous Mistakes — Chapter 15

1. ⚠️ Giving an enema to a patient with stercoral perforation.
2. ⚠️ Treating an unbiopsied rectal ulcer as SRUS when it is cancer.
3. ⚠️ Missing pelvic sepsis after banding.
4. ⚠️ Treating Paget disease as eczema for months.
5. ⚠️ Labelling pain as functional without excluding an abscess or tumour.

Suggested Figure and Table Captions for the Medical Illustrator — Chapter 15

• Figure 15.1. Field-guide grid of ten rare conditions with urgency dots.
• Figure 15.2. Endoscopic appearances: radiation proctitis telangiectasia; solitary rectal ulcer.
• Figure 15.3. Perianal dermatoses: lichen sclerosus, inverse psoriasis, Paget disease.
• Table 15.1. Ten rare conditions: presentation and red flags.
• Table 15.2. Ten rare conditions: work-up, management, and urgency.
• Table 15.3. Rare conditions and what they are mistaken for.
• Algorithm 15.1. When the common diagnosis does not fit.