Introduction
The per rectum (PR) or digital rectal examination is a core clinical skill assessed in OSCE stations across surgical, gastroenterology, urology, and emergency medicine. Despite its intimate nature, a calm and systematic approach ensures patient comfort and diagnostic accuracy. In a typical OSCE, marks are awarded for consent, positioning, perianal inspection, digital technique, prostate or cervix assessment, interpretation of findings, and communication.
Indications
- Rectal bleeding or melaena
- Change in bowel habit
- Lower urinary tract symptoms in males (BPH, prostatitis, prostate cancer)
- Suspected faecal impaction or obstruction
- Anorectal pain or discharge
- Neurological assessment of sacral nerve integrity (cauda equina)
- Pelvic or abdominal pain
Equipment
Collect everything before approaching the patient:
- Non-sterile gloves (one pair)
- Lubricating gel (e.g. KY Jelly)
- Absorbent pad
- Tissues
- Good light source
Consent and Chaperone
Introduce yourself, confirm the patient's identity, explain the procedure clearly, and obtain verbal consent. Always offer a chaperone regardless of your own gender or the patient's gender — this is a key mark scheme point. Document that consent was obtained and whether a chaperone was present or declined.
💡 Tip
Always state: *"I would like to offer you a chaperone for this examination — would that be acceptable?"* even if the station brief implies a male patient. Omitting the chaperone offer commonly loses marks in UK OSCEs.
Positioning
Place the patient in the left lateral (Sims') position, with knees drawn up towards the chest. Expose from the waist downwards and maintain dignity with a sheet. Position an absorbent pad beneath the buttocks and ensure your light source gives a clear view of the perineum.
🧠 Mnemonic
PROBE — PR Examination Framework
P — Position (left lateral, knees flexed to chest)
R — Rectal wall (360° palpation through all four quadrants)
O — Outside first (full perianal inspection before inserting)
B — Bilobed prostate anteriorly (or cervix in females)
E — Exit inspection (examine the glove for blood, mucus, stool colour)
Perianal Inspection
Before any digital examination, spend 30 seconds inspecting the perianal region systematically.
| Finding | Possible Diagnosis |
|---|---|
| Bluish, painful external swelling | External haemorrhoids (below dentate line) |
| Pink mucosal protrusion on straining | Internal haemorrhoids or rectal prolapse |
| Linear posterior midline tear | Anal fissure (most common location) |
| Posterolateral fissure | Crohn's disease, TB, syphilis |
| External opening with surrounding induration | Fistula-in-ano |
| Erythema and excoriation | Perianal dermatitis, threadworm, Candida |
| Condylomata acuminata (cauliflower lesions) | HPV infection |
| Pigmented, irregular lesion | Anal carcinoma (squamous cell) |
| Midline pit or sinus with surrounding inflammation | Pilonidal disease |
⚠️ Red Flag
A fissure in the posterolateral position rather than the typical posterior midline raises suspicion for Crohn's disease, tuberculosis, or syphilis. Always document the precise location and arrange appropriate investigation.
Digital Examination Technique
- 1Apply lubricant liberally to your gloved right index finger
- 2Warn the patient: *"I'm going to touch the outside first, and then insert my finger gently"*
- 3Place your fingertip at the anal verge; ask the patient to bear down as if opening their bowels — this relaxes the external sphincter
- 4Insert your finger slowly and steadily with gentle, controlled pressure; do not force entry
- 5Assess resting anal tone, then ask the patient to squeeze and note the grip
- 6Rotate your finger systematically through all four quadrants: anterior, posterior, left, and right lateral walls
- 7Assess for masses, mucosal irregularity, tenderness, induration, or faecal loading
- 8In males, palpate the prostate anteriorly through the anterior rectal wall
- 9Withdraw slowly; inspect the glove carefully before removing
💎 Clinical Pearl
If the patient has an anal fissure with sphincter spasm preventing entry, do not force the examination. In an OSCE, state: *"I would not proceed further as this patient has significant sphincter spasm consistent with an anal fissure. I would consider topical GTN cream and refer to colorectal surgery rather than cause further pain."*
Prostate Assessment
The normal prostate is bilobed, smooth, with a palpable central sulcus, firm-elastic consistency, non-tender, and approximately 3–4 cm in width.
| Feature | BPH | Prostate Cancer | Acute Prostatitis |
|---|---|---|---|
| Size | Enlarged (grade 1–4) | Variable | Normal to enlarged |
| Surface | Smooth | Irregular, nodular | Smooth |
| Consistency | Firm-elastic | Hard, craggy | Boggy, fluctuant |
| Central sulcus | Preserved then lost | Often absent | May be lost |
| Tenderness | Non-tender | Usually non-tender | Acutely tender |
| Temperature | Normal | Normal | Hot |
Prostate size grading:
- Grade 1 (~20–40 g): sulcus preserved, projects less than 1 cm into rectum
- Grade 2 (~40–70 g): sulcus flattened, projects 1–2 cm
- Grade 3 (~70–100 g): sulcus absent, projects 2–3 cm
- Grade 4 (>100 g): occupies most of the rectal lumen
⚠️ Red Flag
A hard, irregular, asymmetric prostate with loss of the central sulcus is carcinoma until proven otherwise — arrange PSA, MRI prostate, and urology referral. An acutely tender, hot, boggy prostate indicates acute prostatitis — do not massage as this risks bacteraemia and sepsis. Obtain urine and blood cultures and commence antibiotics promptly.
Anal Tone Interpretation
- Normal tone: firm squeeze on request, appropriate resting tone
- Reduced tone: lower motor neurone lesion (L4–S4), cauda equina syndrome, pudendal nerve injury, rectal prolapse
- Increased tone: anal fissure, anxiety, upper motor neurone lesion
⚠️ Red Flag
Reduced anal tone in a patient with back pain must prompt immediate assessment for cauda equina syndrome: ask about urinary retention, faecal incontinence, saddle anaesthesia (inner thighs and perineum), and bilateral lower limb weakness. This is a surgical emergency requiring urgent MRI spine and neurosurgical referral.
Completing the Examination
- Wipe away excess lubricant and offer the patient a tissue to clean themselves
- Allow the patient to dress in complete privacy
- Remove and dispose of gloves into clinical waste
- Perform hand hygiene
- Document: consent, chaperone, perianal findings, digital findings, prostate assessment, glove appearance, and management plan
FAQs
"When should I avoid performing a PR examination?"
Contraindications include severe neutropenia (ANC <0.5 × 10⁹/L), significant thrombocytopenia (<50 × 10⁹/L), known rectal perforation, acute anorectal trauma, or a patient who lacks capacity. Always state contraindications in your OSCE before proceeding.
"What does fresh red blood on the glove after a PR examination indicate?"
Fresh red blood suggests a distal colonic source: haemorrhoids, anal fissure, or rectal carcinoma. Never assume a benign cause in a patient over 45 with rectal bleeding or alarm symptoms — refer urgently via the 2-week-wait pathway for flexible sigmoidoscopy or colonoscopy.
"How do I describe the prostate in an OSCE?"
Use a structured description: size (normal or grade 1–4 enlarged), surface texture (smooth or nodular), consistency (firm-elastic, hard, or boggy), central sulcus (palpable or absent), tenderness (present or absent), and whether it feels fixed to the rectal wall.
"What if the patient refuses the PR examination?"
Acknowledge their absolute right to decline and explore any concerns non-judgementally. Offer alternatives where available: PSA blood test for prostate assessment, imaging for rectal symptoms. Document the refusal clearly. Never proceed without consent.
"Should I use lidocaine gel routinely for a PR examination?"
Lidocaine gel is not routinely required for a diagnostic PR examination — standard lubricating jelly is sufficient. Lidocaine gel may be appropriate when inserting a suppository in a patient with severe anal fissure or when there is significant sphincter spasm.
Related Posts
- Abdominal Examination OSCE — systematic assessment of the abdomen and lower GI causes of rectal bleeding
- Urinary Catheterisation OSCE — managing urinary retention secondary to BPH, a common downstream finding in PR examination
- A–E Assessment OSCE — managing haemodynamic instability in acute lower GI haemorrhage